CA1128642A - Determination of a supersonic projectile trajectory by a convex transducer - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus for use in n firing range, in which transducers located adjacent the target area detect the airborne shock wave from supersonic projectiles, The position at which each projectile passes through the target plane is determined from the relative time of arrival of the associated shock wave at the transducers. A visual display of the target and the projectile position is provided for the use of range personnel.

Description

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BACKGROU~D OF~ THE INVENTION
-1. FIELD OF THE INVENTION
The present invention relates to a firing range and more particularly the present invention relates to a firing range for use in training of personnel in marksmanship.

2. THE PRIOR ART
At the present time, when personnel are trained in firing a weapon such as a rifle it is common to utilize a static firing range in which the personnel fire their weapons at targets which are remote from the firing point, the posi-tion that each round impinges on the target being indicated by further personnel acting as markers who are located adjacent the targets but protected by an earth bank or the like.
This arrangement suffers from the disadvantage that for every trainee marksman there must be a person to act as a marker, and furthermore a rigid target must be utilized which must be repaired after each shooting session so that the point of impact of further rounds on the target can readily be de- `
termined.
A further disadvantage of this prior arrangement is that the sport of shooting is not appealing as a spectator sport since spectators cannot readily see how the shooting is progressing.
Yet a further disadvantage of the prior proposed arrangement is that personnel training the trainee marksman find it difficult to monitor the progress of a large number of trainee marksmen and have to inspect the targets by means of a telescope or binoculars in order to assess how a trainee marks-man is performing. This procedure is time-consuming and in- `
convenient.

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Various at~empts have been made to overcome these disadvantages.
Several proposals have been made in which transducers or similar shock wave detec~ors are connected directly to a ri-gid target or a rigid member located behind the target, thedetectors being adapted to detect shock waves or vibrations generated in the target o~ member by the impact of a bullet on the target. The signals from the detectors are fed to a cal-culating device which calculates the position o~ the bullet or other projectile, and which causes that position to be dis~
played or stored. Specifications that disclose the systems o~
this general type are U.S. Patent Specification 2,973,964 (Zito) and U.S. Patent Specification 3,~78,495 (Gilbert).
Both these particular systems suffer from the disadvantage that a rigid target or member must be used, and the rigid tar-get or member must be replaced after a certain period of use, since otherwise the target or member will be perforated by bullets fired at the target and then the target or member will not satisfactorily transmit the shock waves or vibrations generated when a bullet impinges on the target. Also, if a rigid target is used, with very accurate marksmen a hole will soon be generated in the region of the "bull" of the target, this hole having a diameter greater than the diameter of the bullets being fired at the target. Thus after a period of time a bullet may pass through this hole without generating shock waves, and a shot that should be recorded as a "bull"
will be recorded as a "miss". Furthermore since the trans-ducers are spaced around the periphery of the target or member the transducers may thèmselves be hit by bullets fired at the target, and thus the transducers may be damaged. Thus these `~

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systems suffer from the disadvantage of expense in that both the targets or rigid membe~s and the transducers will have to be replaced at frequent intervals.
Various alternative proposals have been made in which transducers or the like are utilized to detect an air-carried shock wave generated by a bullet or projectile which travels at a speed faster than the speed of sound in air. Such a pro-jectile can be called a supersonic projectile. One very simple proposal of this type is disclosed in U.S. Specification 2,783,047 (Faxen) in which a single shock wave sensitive device is operated to generate a signal in response to a shock wave generated by a supersonic projectile such as bullet and impin-ging on the device. The shock wave sensitive device is moun-ted in a target area zone bounded by a wall so that the device will be responsive to shock wave impulses produced by bullets entering the target area but not those produced by projectiles which pass outside the target area. It will be appreciated, therefore, that this particular arrangement will only be able to distinguish between a "hit" and a "miss" and will not be able to provide any accurate information concerning the pre-cise position at which a bullet impinged upon the target area.
A further proposal in which airborne acoustic shock waves pro-duced by a supersonic projectile such as a bullet are utilized is described in U.S. Patent Specification 3,77~,059 (Rohrbaugh) and in this specification two metal rods are located respec-tively adjacent the base and one side edge of the target, there being acoustic transducers attached to the ends o~ the rods.
When a bullet is fired at the target the shock wave generated by the bullet will impinge on the rods, and a resultant acous~
tic wave generated by the rods will be transmitted to the trans-ducers which subsequently produce an electric signal. The - . . ,:: . , . ~ ~ -. , - :. , , .:. . , ~ :
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resultant signals are fed to a timing and calculating device which calculates the position of the trajectory of the bullet and permits the position at ~hich the bullet hits the target to be displayed on a device such as a cathode ray tube.
A further proposed arrangement is described in U.S.
Specification 3,489,413 (Groder) and this specification dis-closes the use of bi-directional transducers each adapted to detect whether a shock wave generated by a supersonic prcjec~
tile and impinging on the transducer originates from the left or right of the central axis of the transducer. The specifica-tion describes an arrangement in which a plurality of trans-ducers are arranged in a row adjacent the base of the target, and a further plurality of transducers are arranged in a col-umn adjacent the side of the target. In view o~ the nature of the system it is only possible to determine which broad area of the target was impinged upon b~ any particular bullet since it will only be possible to determine the position of the bul-let by reference to the two transducers at the base of the target between which the bullet passed and the corresponding two transducers at the side of the target. Thus the system only has very limited accuracy and furthermore the transducers provided at the side of the target are susceptible to damage by inaccurate firing.
A ~urther prior proposal is disclosed in U.5. Speci-fication 2,925,582 (Mattei~ a~d this specification discloses the use of four transducers spaced around the periphery of a target area, signa~s derived by the four transducers when a bullet is fired at the target being fed to an appropriate cal-culating and display device adapted to calculate and display the position of the bullet. The calculating device initially determines the duration of the shock wave detected by each . .
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transducer, since the dura~ion of the shock wave increases with increasing distance from the origin of the shock waves.
Signals representative of the durations of the shock wave con-trol the beam scanning circuits of a display device. This prior proposed arrangement suffers from the disadvantage that at least three of the transducers are exposed to fire from the marksmen and are thus susceptible to damage. Furthermore, the levels of accuracy obtainable with the system described in this U.S. specification are not very h.igh.
It will be appreciated that the pxiox art discussed above discloses the general use of transducers to detect shock waves present in a rigid target or to detect airborne shock waves generated by a projectile such as a bullet, but all the prior proposed arrangements suffer from either the disadvan-tage that the arrangement does not provide an accurate indica-tion of the precise position of the bullet, or the disadvan-tage that the transducers are in a position in which they may be damaged by bullets hitting the transducers. Furthermore, some of the prior proposals suffer from the disadvantage that rigid targets must be provided which must be replaced regular-ly to ensure that shock waves are transmitted satisfactorily through the rigid targets.
At the present time in training a trainee marksman to hold his weapon correct,ly it is necessary for a trainer to observe the firing position adopted by the trainee marksman.
If the weapon is held incorrectly the rounds fired by the trainee marksman will not hold a consistent group but will spread at random over and around the target. Consequently the trainer may be able to assess the faults of the trainee , . '. , I ' ' .
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marlisn~an. llo~ever, i~ the :Eau.l-ts of the trainee marksman are consisi.e~llt the trainer may reach -the conclusi.on that the sigh-t3 o:~ -the weapon of a trainee maricsman are~ incorrectl-y ad;just~d, allcl may adjusl; the s:i.ghts of -ihe weapon. Conseq--~
ently, althollgh the rounds ~:ired by -th.e trainee mar]csman Inay then group at the ce.ntre o~ the target, the -trainee marksiman may still be holding the weapon incorrec-tly.
It is f-llr-ther to be appreciated that, at the present time~ there is no way o:~ knowirlg what the trainee marksman actually sees over the sights of the weapon, and the present inveniion also seeks to provide an apparat-us to enable the image viewed by the trainee marksman to bc viewed by a trainer or to be recorcled.
¦ ~urthermore it is to be appreciated that correct breathing is an importallt part of accurate marksmanship, and thus the present invention also seeks to provide an apparatus ~or monitorillg the breathing of a trainee marksman and also for monitoring the pulse-rate of a trainee marksman.
The present invention seeks to provide an improved target in which the above described disadvantages are obvi.ated or reduced.
According to one aspect of this invention there is provided an apparatus for determi-ning i.nformation concerning the trajectol~r of a supersonic projectile passing through 2~ a predeterminecl area, the apparatus comprising at l.east three - ;:. . ~ . . .
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transducers located spaced adjacent an edge of the predetermined area, each said transducer comprising a member of rlgid material having a convex surface exposed to an airborne shock wave gener-ated by the supersonic projectile, and means for providing an output signal in response to detection of such a shock wave by said member, the output signal providing means being connected to said rigid member such that the distance of the path between any point on the convex surface and the said output signal providing means is constant so that the output signal is gener-ated at a pre-determined time relati~e to the instant at which the airborne shock wave impinges upon the said convex surface, regardless of the location of the point on the convex surface that is impinged by the shock wave, there being means to measure the time delays between the output signals generated by each of the transducers, and means adapted to calculate, from said time delays, information concerning the trajectory of the projectile.
In this specification the word "transducer" is used to mean a device capable of providing an output signal in response to detection of a shock wave generated by a supersonic projectile.
Preferably, the transducers are located adjacent the lower side edge of the predetermined area, and conveniently the trans-ducers are each adapted to be mounted so that the shock wave impinges directly on the transducer.
Preferably, each transducer may comprise a disc shaped member of a piezo-electric material and each disc preferably has a diameter of approximately 5 mm.
In one arrangement the plane of each disc shaped member is substantially vertical, but the plane of each disc may be hori-zontal or may be inclined.
Advantageously each transducer comprises a member of rigid material for transmitting said airborne shock wave to a piezo electric material element in firm contact with the base of the said~member~

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said member having a convex surface exposed to the shock wave.
Preferably said member is hemi-spherical.
Conveniently each transducer comprises a member of an insulating material having a recess to accommodate a disc of - 7a -.

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piezo-electric mater~al lla-ving con~uct:ive coa-tings oll tho t,~10 oppoaed face~ thereof and challnels accommoc~at:;ng conduc-tive r wires connected to said coatings, the base of said member of rigid materia:L being secured to tlle piezo~clectric disc.
preferably -the member of in~ulating material is surrounded by a sleeve of an electrically conducting rl~aterial to act as a ~araday Cage.
~dvantageously each transducer is mounted on a rigid structure, the transducer being mounted in an appropriately shaped block of acoustic de-coupling l)laterial, the block being clamped or otherwise secured to the r:igid structure.
I Preferably said acou3tic de-coupling material comprises closed cel~ polyethylene foam.
I The predetermlned area may be a target area which 1~ ' may be provided with one or more targets. The information calculated may be the position of the trajectory relative to the target area, F
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In an alternative embodiment of the invention the transducers may be mounted in apertures formed at predeter-mined locations in a support panel, the transducers being di-mensioned to be snugly engaged in said apertures, the panel being provided with means for absorbing shock waves. The panel may comprise a sheet of metal with sheets of sound ab-sorbing material secured to the faces thereof.
Preferably means for absorbing shock waves or sound may be located between a rigid target in said target area and said transducers.
Means may be provided for amplifying the signal pro-duced by each transducer, and such amplifying means may com-prise initial amplifying means and a threshold comparator which only passes si~nals having a predetermined minimum value. The output of the threshold comparator may be amplified with a linear amplifier, and the threshold comparator may be adjus-table. Four, five, six, seven, eight or nine transducers may be provided.
In one arrangement in accordance with the invention a plurality of target areas are located adjacent one another, and there is one array of transducers located under the tar-get areas, the calculating means being adapted to select sig-nals from the transducers providing an output signal in res-ponse to detection of a shock wave generated by a supersonic projectile fired at one of said target areas. The said array may be a linear row of transducers or may be two staggered rows of transducers.
Preferably means are provided for storing tempora-rily information concerning the time of generation of a signal by each transducer, and means are provided for subse~uently _g_ .
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The storing means may comprise counters which are started and stopped in response to the detection of a shock wave by predetermined transducers, the counts stored in the counter subsequently being transferred to the computer. Al-ternatively, a clock signal generator may be provided to pro-vide successive signals representative of successive instants of time, latches being provided adapted to store the signal generated by the clock signal generator at the instant that the latch receives a signal from an associat~d transducer;
means may also be provided to supply a signal indicative of each latch, and to transfer signals from each latch and the means providing a signal indicative of that latch to a buffer.
Further means may be provided for transferring signals from the buffer to a computer memory when the memory is able to accept the information.
A plurality of groups of transducers may be provided, each group being associated with one of said storing means.
Each group of transducers may be associated with one bank of targets.
Preferably said computer comprises means for scan-ning information signals fed to the computer to select groups of signals likely to be derived from a single shock wave, and means for calculating the position of a projectile from each of said groups of signals. The calculating means may comprise a pre-programmed general-purpose device. The computer may be adapted to control the display of information on a visual dis-play unit, and a television camera may be provided to gene-rate a display signal from a visual image of a target. Means .ay be provided for detecting when a portion of the targetimaqe corr~s- ...

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ponding to the ccllculated position of a projectile is being displaved, and for inverting or otherwise modifying the display si~nal a-t'that instant.
Preferably means are provided for determining the co-ordinates of the point of the visual image being scanned by the televlsion camera at any instant, and for comparing these co-ordinates with the co~ordinates of the position of the projectiles as calculated by the computer. ' '' ' The computer may also be proved with means for printing output data or punching paper with output dat~
In one embodiment of the invention the transducers `~
a~e all located adjacent a lower edge of a target are-a and are concealed from the flring point by means which cannot bo penetrated by said project:iles.
A rigid target may be provided in said target area and each target may be provided with means to move the target from a concealed position to a visible position and vice versa. Also means may be provided for illuminating the target provided at said target area to permit shooting to be conducted after dark.
Thé transducers and rigid target may be mounted on a -trolley which can move along a predetermin0d -track to permit ', the position of the target to be adjusted.
2~ ~ computer may be'provided adapted to control and monitor movements of the targets. If a plurality of targets are provided, the computer may be provdecl with means for displaying -thc condition of each,target. Alternatively, radio control meall.s are p~ovided to control rrlovement of the tar~e~t.
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Accordirlg to another aspect of th:is inve:ntlon the-re is provid~d a transducer for detecting an air'borne shock wave, the -transducer comprising a dome member of` substa:nt-Lal:Ly rigid ma-terial and llaving a. convex surface adapted to be exposed to the shock wave, the dome member transm-ltting the shock wave -to an elenlent which p.tovides an outpu-t signal in response to the shock wave, -the e].ement being connected to the base of the dome.
Preferably the dome member is hemi.~spherical.
Conveniently the elemen-t adapted to provida said output signal comprises a disc shaped member of` piezo-electric material, one planar face of which is connected to thc base of the dome menlber.
In one embodiment the disc is bonded into a recess formed in a housing formed of insulating material, the 'oase of the clome being provided wi.th a prejection dimensi.oned to pro;jec-t into said rece,ss and engage the disc of piezo~electric material . ~:
Conveniently opposed planar faces of said disc are 20. coated witl~ an electrically conductive material 9 and electrically conclucti.ve wires are connected to the coated f~.ces~
P:referably shielding means are provided to shiel;l the trnnsdllcers so that the regi~n of space from which the tr~ansducer~ may raceive sh.ock waves is bounded by a single pllne, and the shielding.means may comprise a rigid linear melDb~r extending in front of and a~ove the transducers.
Conveniently two substalltia].ly linear row.s of transducers may be pro-vided~ each row of transducer~ cornprising at leas.t three transducers J the two rows of transducerc, being arranged ill sllbstalltlally a common plane.

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~ccorcl;n~ l;o a1lo-tl1e-r ca.spec1; o:r` t~li.s :Lnve)~ti.on t1-Jere i.s provide~ a trl:irling equipl11cnt ro:r train;.ng personncl, saicd equiplnent coln~r:ising a weapon~ means for detecting lhe pressure applied to predc-ternli.ne p~rts of thc ~-eapon by a person hol.ding t~c weapoll, and rneans for recording or displaying the pressure applled to the weapon.
Preferab]y a visua:L display -un:Lt ma-y be prov;.ded to display the pressure appli.ed to the weapon comprising means to d-.splay a representation of weapon and means for causing parts of the represen-tation to have colours representative of the pressure applied to the correspondlng parts o:~ the actual weapon.
According to a further aspect of this invention there .~s provided a weapon for use in training personnel in the art of marksmanship, said weapon being provided with means for generating an image representa-tive of the image viewed by the marksman across the sights of the weapon, and means for recording the generated image or for en~ab:Ling another person to view the generatecl image.
2~ Preferably there is p-rovided a device for monitoring the breathing of a marksman, said device comprising a belt or the like adapted to be worn by th.e marksmatl and means f`or measuring the tension within the belt to ascer-tain the quantity of air within the lungs of the marksman.~ -In order that -the inven-tion may be more reaclily understood and so that further features thereof may be appreciated, the inveIltion will now be described by way of example wi-th referencie to the accompa:nying drawings in whichs Figure :L :i.s a perspecti.ve view of a rif].e range provided with a.n apparatv.s in accordance will~ the pre.se]lt invention;
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Figure 2 i5 a cl:;agram indicating the posit:ion o~
the trajectory Or a ~rojecti:le relative -to four transduce~s and relati~-e~ to co-ord;.nate axes;

Figure 3 illustrates hyperbolic co-ordinates defined by units of time dif:Eerence between the instant of reception of shock waves by adjacent pairs of transducers;
Figure 4 is a hlock diagram of one embodiment of the invention;
Figure 5 illustrates an arrangement of staggered transducers and the corresponding intersecting hyperbolic co-ordinates;
Figure 6 illustrates a transducer element;
Figure 7 illustrates the output signal generated by the transducer of Figure 6;
Figure 8 is an elevational view of four trans-ducers;
Figure 9 is an exploded perspective view of a preferred type of transducer;
Figure 10 is a cross-sectional view of the trans-ducer of Figure 9;
Figure 11 is a perspective view of an arrangement for mounting the transducer of Figures 9 and 10;
Figure 12 is a circuit diagram of an amplifier associated with the transducer of Figures 9 and 10;
Figure 13 is an elevational view illustrating the shock wave generated by a supersonic projectile;
Figure 14 is a representation of the trajectory of a projectile and the detection of the resultant shock wave by a transducer, points being identified thereon to assist in mathematical analysis of the situation;
Figure lS is a block diagram of another embodi-ment of the invention;
Figure 16 is a block diagram of part of the embodiment shown in Figure lS
Figure 17 is a block diagram of another part of the embodiment shown in Figure 15;

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~igllrQ L~ is a block diagrarl1 of another par-t O:r the embodi.men-t S}lOWII in Flgure 15;
ï~igure .1.9 is a repre.serltation of the trajectory of a projectile allCJ tl~e detection ol the resultnnt shock wave by a transducer, points being identified thereon to assist in mathematical analysis of the situation;
~igure 20 is a perspective view, partly cut away, of a panel for supportin~r transducers;
~igure 21 is a side view of a target and associated transducers i:Llustra-ting a block of so~nd absorbing material;
Figure 22 is a perspective view of another embodiment of a rifle range in accordance with the invention;
~igure 23 is a diagrammatic view showing the shock wave generated by a bu].let during its flight;
~igure 24 is a perspecti.ve view of a row of transducers shielded by a shield;
~igures25 to 28 are diagrammatic views o.f a shielded transducer and a shock wa~e generated by a bullet 9 these figures illllstrating the situation at successive instants ~0 of t:inle;
F:igure 29 is a perspective view illustrating a preforred axra~ of transducers;
l~igure 30 is a side elevætional view of a weapon in~accordance with the inverltion suitable for use in a range in ~ccorclance ~ith the present invclltion, providecl with pre~3ure-sensitive transclucexs, and a fibre optic device;
~igure 31 is an illustration o:C a display su.it~ble for use whon t.h.e weapon illustratecl in Figu]7e 30 is uti].i3ed, ~i.gu.re 32 is a diagra.lDlDatic per3pective view of a .
trainee ma.rksll~an utilising the weapon illustratcd in l~igure 30 :

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aMd also proviclod with means f`or mon;.tor:ing pu]so an~
breathing rates;
Figure 33 :i.s a bloc:li circui-t dlagram o:~ the apparatus utilised for monitoring the marksman lllus-trated in Figure 32;
Figure 3lI is a flow dlagram O r opcration of the apparatus illus-trated in Figure ll and ~igure 35 is a flow diagram o~` operati.on of the apparatus illustrated in ~igure 15.

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~efarri1~g -to Figure l of the accompany:ing d~awings a rifle range in aecordance ~ith t11e ~reserl-t inventio-n eomprisQs a plurality of~ firing points :L intendecl to be oecupled by -trainee marksmen 2, and a corresponding number of targets 3 intended to be fired at by the -trainee marksmerl.
The targets are shown in a single bank~ but a plurality of banks of targets spaced at increasing distances from the firing points may be provided. Loca-ted in front of the targets is an earth bank 4 or ot}ler protective device and located behind the earth bank 4, and thus out of the line of sight o~ the trainee marksmen 2, are a-t least three transducers 5, the transducers being arranged at spaced positions adjacent the ]o~er edges of` the targe-t ~nd being adapted to sense the shock ~;aves generated by bullets fired at the targets. One S long row of transducers may be provicled in front of all the targets, or a separate group of transducers may be provided ~or each -target. The transduce;~s 5 will be described in more detall hereinafter. The transducers 5 are connected1 by mean~s of appropriate cables 6 to a co~lputer 7 or other suitable ealeu~ating device which is aceommodated in a control room 8 uti~ ed by the range controller. Tlle computer is adapted to ealeullte the position of eaeh round fire at each -target 3 ~h~n the shoek wave generated by the round is deteeted by the ;~
tra~1sducers. T11e position of` eaeh bullet may be displayed 2~ on a visual display unit 9 in the control room and 011 a visual display unit 10 provided at each firing point l. Thus the trai1lee marksman may see ~here each particular round .in~p~ ges on the target. ~f spectaGor.s ll arc- to be present, a large visual display device 12 may be eonnected to the .
compu~er 7 to enal~le the spectators 10 to vie~ tho progress of tbe -1ri~ , :

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~ shooting. In aclcl~t;oIl, or a~ an al~rnlltive to t'he provision o~ -the d;sp]ay Wl:its, print out dovicos or papor punching devices ]3 may be operated by the computer 7 to providc a printe(it or punchod paper out;pul; inclic~tlng the point at which eacll bullet impinges upon the target 3.
It wi.ll be appreciated that wi-th a system o~ this type it is not necessar,v to use rigi.d ta.rge-ts, and the only requirement of the target is that the target should be visible to the tralnee marl~sman to provide an aiming po,nt.
Thus it ls not necessary to utilise personnel to repair targets or indicate the position at which incli.v:idual rounds impinged upon the target, It will also be appreciatcd that since the transducers 5 are l.ocated behind the ear-th bank 4, t~e only possible ~ay in which the tran~ducers can be damaged al a result of` firing is as a consequcnce of a ricochet, and such r:icochets are very unusual. 'rhe probability of any transducer being dan~aged is extremely low. As will be explained in more detail hereinafter, utilising a system of' this type it is possible to ob-tain great accuracy and, in fact, with a -target area o.f 6 ft. by 6 ft. it :is possible to calculate the position of any builet, imp:inging on Lhat; target area with an accuracy of greater than ,1 inch. It is bel.ieved that if appropriate s-teps are taken this.accuracy 1' may be improved.
¦ 2~ Now that the invention has been broad:Ly clescribecl~
the apparatus will be described in more detail.
. In one relatively simple embodimcnt of the in.vention I it is asswned -that the shocl~ wave generated by a supersonic ¦ p.rojectile expands in a direction perpend:Lcular to the i 3 trnjectory oI` th.e projectile, arld th.us a plural.:ity oI` de-t;ectors .
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in a si.ngle plane per1?endicular to t}l~ -trajecto~y will detect the shoclc wave at -tinles dependen-t solely upon the distance of` the respective d~tector fronl the trajectory.
In an 0mbodiment o~ the inventi.on of thls type at least four transducers T , Tl, T2, and T3 as .shown in Figur~ 2 are arranged on a horizontal line e~tending from lef-t to rlght.
The distance from tran.sducer T to transdueers Tl, T2 and T3 ean be considered to be xl, x2 and X3 respectively. If a bullet passes over the transducers at a general point P(x, y) on eo-ordinates based on transducer T , the distanees from the pair x, y to the transdueers To, Tl, T2 and T3 will be lo, ll, 12 and 13, respeetively.
It is assumed that the trajeetory of the bu]let is p rpendieular to the vertieal plane eontaining the transducers, l~ and also tha-t the transducers will reeei.ve the shoek wave from the bullet sequentially and with time delays varying in dependence upon the preeise trajectory of the bullet. From the signals genera-ted by the transdueers, further signals tl, t2 and t3 ean be ealcula-ted, tl being the time delay between -the reoepti.on o~ the shoek wave by transducer Tl and transducer T , (this figure being negatlve ir transdueer To reeeives the shoek wave b~ore transdueer Tl), anci t2 and t3 corresponding time delays ~or transdueers T2 and T3.
It will be apparellt that t~ ~lo) /Vn (~

t2 ( 2 o) / - (~2) t3 = (13~ n (~) wllere Vll is the velocity of the shock wave perp0nd;.eular to the traJectory of` the bullet.

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We }~ave that 12 ~2 ~ x2 12 y2 f x2 ~ xl2 2xxl 122 -- Y + X + X2 - 2xx2 123 _ y2 ~ x2 ~ x2 - 2xx3 Ther~ ore 2 _ 12 - (11 ~1o)(ll + lo) = (11 10)(11 ' ~ 1 2 0 2 0)( 2 ~ lo) ~ ~12 ~ 10)(12 ~ lo ~ 2~1o)~X2~2~;X

13 - 10 - (13 10)(13 + lo) = ~13 ~ lo3(13~ lo ~ 2~10)=x3 -2~-x2 ' ' . ''' '' ' ~

Substitutin~,r i'or ( 11 - lo) by tlVn etc ~ .

:10 ~r2' tl ~ 2Vntl lo = Xl 2XX1 ~1 Vll t;2 ~ 2Vnt2 lo - xz 2 C2_ y;~ t2 + 2V t3 lo = X3 2xx3 Mu L l;~ plyillg Cl by t2 and (~2 by tl and subtracting: -Y~ tlt2-(tl- t2) _ xlt2 ~ x2tl ~ 2x (x2t;L - xlt2) 1.~ Mult.iplying ,1 by t3 and Cl by tl and sul:)tract:ing:-Vn tit3 ( t~ 3) = Xlt3 ~ ~3tl * 2x (x:3tl ~ ~ t3) D2 n~ricling DJ. ~ 1)2 and 7~carrangillg g:i V3 S
~ 1 (-~3~ 2~3)t2(t,.~t2)~ t~ 2t23~,3(~ t3,~! .

~X i; -~-t3)l2(tl't2) ~ 2tl-x~t2)t3(t;l 3) J ~u .. . .. , . , . .. . ; . .. .... . .
, ` ~ , ., ; ~
., .
.. . " , ... ,, .., ~
.. .. ; .

( ) 3L~Z8~

Cyclic rear:rall~ement of terms wi.ll also y:ield:-f~ 1 2 x2tl)t3(~2~t3)~ (X3t2~X2t3) tl(t2-t ) l(., lt2 x2tl)t3(t2~t3)- tX3t2-X2t3)tl(t - L; ) and x - 1 1(x2~3-x3t2)tl(t3-tl)- (xlt3 x3 1) 2( 3 2) l~ 2 3 x3t2)tl(t3~tl)- (Xlt3-X3tl)t2(t3-t ) 411 the value~ on -the ~ight o~f the equation are known~
- ! . . , '~

' ~
. ~ ~

. ~ ' ' ~ ' ' " ' ' ' . ' . ; .
.
.' ' . . , ' ,~

9_ . ' æ
c~la~in~ rounc- x ~Te Inay rr:it;e rrom nl y2 xlt2(X1~2X) X2tl( 2 . tlt2(t]~t2) Cyclic rearran~enlent of terms w:ill also yield j y2 _ X2t3(~c2-2~{) ~ X3t2(X3 ~ ' ` t2t3(t2-t3) , and v2 _ x3t](X3-2x) - Xlt3(X1~2X) _____~__ . ' ' Thus ~e can measure the erfecti~re spced of sound; wllich enables the val~le of y to be determined as follows :
Usin~r Cl t~e may ~rite -o ~ (~;l(Xl-2X) ~ Vn-tl) ~ (X (x2-2x)-V2t2) ' 4v2t2 , _ (X3(X3-2~c)-vrlt3) . 1~V2.1;2 ~ J
}lence we can fi.nd y:-.~ Y -- [ 1 _ x . As lndica-ted above in an appara~tus in accordance with the present inventlon a plural.~ty of transducers are 1 located beneath a target at wllick a tl-aillee marksman is to ~i.re~ Consi.der an embodilnerll; o~ the invention i.n whictl at le~st tllxee t;xal-sdllcers are arranged in a hor.i.zorltal line, . _20~

,, i .
' 8~
the transducers bein~ equispacc~l. Tl~e trarl.sdllc~rs l~, 1.5, .1.7 are illustratecl scl~ematically in Figure 3. The tr~nsdueors each genora-te a signa~.~the time a-t wh:ich a shock wave generated by the bullet is detected, and the signals are f~d to a timing device which calculates the time delays between the detection of the sllock wa~e by the first transducer and the last transducer. Referring to Figure 3 of the drawings, it can be seen that. if the shock ~ave is detected by the transducers :L5 and 16 simultaneously then the trajectory Or tlle bullet must lie on the cen-tral vertical line too.
However, if the difference i.n time of detections of the shock.
wave is one unit o~ time9 the transducer 16 receiving the shock ~ave before transducer 15s then lt will be appreciated that the trajec-tory o* the bullet is somewhere on the 1~ hyperbolie line'tOl. Similarly if the shock wave is detected by the transducer 15 one unit of -time before it i.s d~tected by the transducer 16 then the trajectory of the bulle-t must be on the hyperbolie line -tl . I-t will readily be appreciated that a ~amily of these hyperholic eoordinates-may 'be generated, simi.lar hypcrbolie coordinates bèil~g defi.ned by tha combination o~ transdueers 16, 17 and a:Lso by the combination of transducers l~, 17.
In one specific embodimellt of the invention based on the foregoing mathematieal a.nalysis, five transdueers J8--22 '~
(as sho~l in Figure ll) are uti.lisecl whieh are mounted in 'position so that they are spaeed apa:rt in a row beneath thc target area. A typical transducer construc-tion that may be use~ will be describc-d hereinafter. The output of each transducer i~ fed to a ~e.spc-cti~e one o~ arilplifiers 23~27 to ampllfy the OUtpllt slgr~ l. A typlcal ampliI`ier ci.:rcu.it wi.l.:l. be , - . - . . ~:

: , : ; ~ : - . :, :, : .

'~ descr~ eclllereillar~Qr. Cvunters ~8~ ~9, 30 arl~ 31 ~l:rc COllrleCte~-respectively to tlle oul,pl.lt.s of ampli:C:iers 23, Z~l, 26 and 27, A Iogic c(Jn1;rol ~levice 32 is co,~lccted to the OUtpllt of the amplirler 25, ancl i,s also connected to provide a signal to eacll of the courlters 2c", 29, 30 and 31 when a signal i.s present OIl tha output of a1npllfier 25. I~ach coun~er may be of the type 7l~l91 sold by Texas lnstruments. Each counter is comlected so that if it initially receives a signal ~rom the respective amplifier it will count at a prede-ter~ ined rate in a negative sen.se until the cont.rol device 3~ :receives a s:ignal from amplifier 25, anci then the ~ counter w:ill stop. Alter.llative].y, i.f the counter initially receives a signal frolll the co:n'trol de~ice 32~ then the eounter ~T:ill count at the prede~termined rate i.n the positive sense unti.l the courlter receives a signal from the associated amplifier, Thus, as a bullet or other supersoni.c projectile passes over the transducers 18 to 22 and the shook ~ave is .detected sequentially by the transducers, the counters 28, 29, 30 and 31 will store counts representative of the time dirfereilce betweeIl the instant of detection of the shock wave by tra~sducers lS, 19, 21 ancd 22 respectively and transducer 20.
A computing device 7 is connected to the outputs of the eounters, and includes a memory for storlng the counts. The 25 eomputjng device 7 scans the s~,ored tlme delays and calculates the time difference between each adJacent pair oI` transducers. ~omputlng device 7 then compares the calculated time dif~ercnces and se].ects the group of four adjacent transducers for wh:ic,h the calcul.ated time cli~`:[`ereIlces ', .

. , ' ' ' .
., . ~ ': . ,~. '', ' ' -`` .~2~ 2 are smalles-t in magnitudeO The comput;ng devi.ce then proceeds to calculate the position of the trajectory of the bul:Let from the meQ~sured values for tl, t2, and t3, and known values for xl, x2 and X3, ;.n accordance with equations given above. The measured values of the di.stances between all the transducers (ie xl, x2 and x3) are permanen-tly stored in the computer memory. Once the position of the bullet is detcl~mined, thi.s posi-tion can be displayed on an appropriate d:isplay device 33, prin-ted by ~ printer, or otherwise utili.zed to indicate the shooting accuracy oP the trai.nee marksman .
In the embodiment of the invention presently being described the computing device 7 can be considered to calcul.ate the position of the trajectory of the bullet by determining the l~ hyperbolic coordinates of the trajectory. For accurate results to be obtained it is necessary either to use at l.east .four (prcferably five) transducers and utilise information derived from each of the transducers to assist in calculating the posltion of the trajectory~ or it is necessary to provide the computer ~ith inforl~lation concerning the velocity of thc bullet and the velocity of sound i.n air. Thus, in certain ci.roulllstances it may be adequate to utilize three transducers.
For example, where a certain amount of inaccuracy can be tolerated, and/or where match ammunition is being util.ized7 the computer or other calculating device can be pre-programmed ` or otherwise supp].ied with the bullet velocity and 1he sound ~l.ocity.
If four transdllccrs are ll-tilized there is a vertical elro:r zone extending above tl).e transducers. I.f a bul.let :is rired throu~ll this parti.cular error zone there is a hi~,h Z~6~Z

probahil:ity that the comput:ing dev.i.ce will err~neously caLculate the posltion o* thc bullet and the crror may b~ as large as several ~eet. Thus, even :if ~our transducers are util;.zed, and the -target is so pos;.tloned relative to the transclucers that the error zone does not; coincidc wlth the target area, if a trainee marksman misses the target an~ the bullet passes throug]l the error zone it is possib].e that the computer will calculate the positlon of` the bullet erroneously, and will inclicate that the bullet hi-t the targe-t, while the bullet in real;ty lllissed the target. T.his error zone, is, in actual j fact5 symlnatrically located between two of the transducers and thus, when a bullet passes through thls error zone the two transducers with respect to wllich the error zone is symmetrically located will each detect the shock wave substantially sin~ultaneously. It is possible to take account of this *act and to prog~ramn~e the computing clevice to recogni.se a situation where the bullet has passed into the error zone, i.e.
-to recognise the situation ~here the two transducers in question receive the shock wave substantially simultancously, nnd to provi.de an appropriate di.splay or print out. Tllus if -the error zone is not on the target area the compu1;er is to inclicate that the bullet was a "~niss" or to indicate that the bu~llet passed through the error zone. In any event a bu].let pa~lssing into the error zone would be disregarded and would 2~ llOt be recorded as a "hit".
S.i.ncc the existence of` the above described error zc,ne is clisadvantageolls, it is preferred to u.tilise at :Least f`ive transducers as il:l.ustrated in I~lgure 1~ I* such an arrangement is utiliz~d there are five different notional groups of ~our 30 . l:ransduce-rs -that can be selected from the five transclucers.

- ' . ~ - , ,, :

.

: -` ? 1 1~2~2 The col]~putin~ device 7 is aclapt~d to store signals r~prc-sentati~e of tllc time O:r recepti.on of the sllock. wave by each of the transducers 5, to calcu:l.ate the posl-tion of the projecti.le by using one prima-~r group of four tran.sducers. Howev~r~ when the computin~ device ini.tlall-y selecte a group o.~ four transd~cers, it will determ:ine wllet}ie.r -the bullet or projectile passed through the error zone of that particular group of four transducers. If so, the computing device rejects that group and selects a ~urther group of four transducers from the five and repeats the calculation. Of course, in such a situa-tionS
it would be possible for -the calculation to be repeated using each of the relllaining four of the five possible transducer groups, and for the computing device then to take an average or mean result, thus fur-ther reducing the error.
. In utilizing a five transducer arrangement of this type it -is possible to provide reasonable accuracy over a large rectangu]ar area located immediately above the row of transducers.
The only zones where accuracy cannot be guaranteed are located at the very side edges of the rectangular area above the transduccrs. If it is desired to eliminate the possible errors tllat.may occur wh.en a bul.let passcs through t;hese zones, the transclucers may be selectcd or adjusted so that each transducer OIlly detects shocl~ waves frorn a proJectile wi.th:in a pradeterminecl ;
~distance of the transducer, this predetermined dis-tance being 2~ se~ected so -that bu]le-ts entering i:nto the zones where errors are likel-~r to occur are not detected by all -the transducers.
I~ the shock wave g~nerated by a bul:l.et i.s no-t detected by all the transducers the posit:ion of the bullet is not calculated.
Al1;ernat;vely, th.e comput.ing clevice may be programmec1 to detec-t ~0 when a ~ll].et passes wlthin the error zone ancl to provicle an -2~- .

~ ; . : . ~ . , . ~ . , , ~ ;:. : : : ;

`'`'`~'`` ~2~6~æ

ap~ropriat:e outl-)u-t~ since lr the bu.llet doe.s enter the error zone the various time dirferences be-tween the instants of recepti.on o~ the shock wave by the ~ar:ious transd~cers will have a very recognisable pattern.
In yet another embodiment of the inventi.on, where the . invention is utilized on a range having a large number of targets, it i5 possible to provide a long row of transducers, the transclucers being located beneath t'he targets. Whenever a bullet is firecl at a target the shock wave generated by the bullet wil.l initially be detected by one transducer or by two transducers substantially silnultaneously. Depending upon wh.ich tr~nsducer, or transducers, inltially detect the shock wave, a group of four or five transducers surrounding that initial transducer or transducers is selected by'the computing device.
1~ The times o~ shock wave detection by those transducers are utili~ed as a basis ~or the calculation.
While it has been indicated above that certain error ~ones appear ~here transducers are located in a straight horizontal ~ e, it is e.nvisaged thatthese error zones Inay be reduced or or obviated i~ the transducers are arranged, as sho~.~ in ~i~urc 5, in one upper horizontal row 34, 35 9 36, and one lo~er hor:iY.ontal ro~ 37, 38, the transducers 37, 38 in the lower ~oW being o~fset with regard to the transducers 34, 3~, 36 in tlle upper row. Thus the transducers define a letter "W".
:Ct wi.ll be apprecia-ted tha-t -the hyperbolic coordinates de~:ined by the transduc`ers when dis~osed in this way intersect at righ-t angles or at an angle dependant upon the angle o~ inc;.dence bet~een the arills o~ -t'he "W", thu.s pro~-ldillg a h-igh degree o~
accuracy. Some o~ these hyperbollc coordinat.es are illust.ra-ted~
0~ course, :i.n ad.dition to the i.ntersec-ting hyperbol-ic coorcli.nates ~6 .
, ,; . .
. ` . ` . ~, . .
.. .. . ....
` , , : ,.;
i , . . ... ; ... .
. ' . ,. ~
..... ..
. ` . . .. . :
... . .. .. .
... . . ...

- ~2~2 as illustr~ted, the tllree transdllcers 34, 35; 36 in the upper :row can be utilised in precisely the same way as the three -transd~lcers illustrated in Figure 3, and thus many intersecting h~perbolea can be dQ~'ined.
In practicing the presen-t invention it is poss:;ble to utilize as a -transducer, a flat disc 39 of a piezo-electric material. Such a transducer may bé located in a hori~ontal posi-tion as illustrated in Flgure 6. Such a transducer does possess several disadvantages, however.
If ca bullet 40 is fired to the right of the transducer the subsequent shoclc wave 41 will impinge on the edge or corner o~ the transducer 39, and the transducer will be compressed both ;
in a vertical direction and in a horizontal direc-tion. The resultant output of the transducer will have a wave form substantially as~illustrated in Figure 7, which is a negative golng sinusoidal wave I`orm 42 ha-ving a small positive "pip" 43 at the leading edge. I-t is desired to measure the time T
illustrated on the wave form, and it is very difficul-t to detect this time ~ accurately since the amplitude of the "pi.p" 43 dopends upon the precise position of a bullet, ls di:~ficult to d:istinguish :from baclcground noise, and can even be absent.
Tho comput;ng device is provided with inI'ormation concerning the position of the transducer, this information being the precise position of the center 44 of the transducer. All calculations are performed on the assump-tion that the 'transducer is at this particular position, and that the ou-tput signal ~enerated by the transducer is indica-tive of tlle insta~ at ~hich the shock wave arrives at this part:icular position. The transducer, ho~ever, provides an outpu-t l~ith a prede-torminec1 re~ponse tlme as soon as the shocl~ wave imp;llges .
~27~ ~

` `" ~L~%~ L2 upon the transduce:r. If a bu]let 1l5 passes vcrti.cally above the transducer 39 the shock wave imp.ingcs clirec-tly on the upper surface o~ the transducer, generatirlg an appropriate outpu-t si.gnal. Now it ca~ be seen that the trajectory of the bullet /lO Pired to tb.e right of the transducer is ~ur-t;her from the point ll~ than the trajectory of the bullet 45 passing immediately over the transducer.
However the distance between the transduceb~ surface and each o~ the trajectories of the bulle-ts 40, 45 is equal to a distance L. Since the transducer provides an outpu-t as soo~ as the shock wave impinges on -the transducer, the -tillles between -the bullets passing and the output signal being generated are equa:L. Thus -the output cf the tr~nsducer would sug~gest that the trajectories o~ the bulle-ts 40, 45 l~ are equispaced from point 44, which is not correc-t. In other words 9 a slight timing error will be generated and the calculated trajectory of the bullet pa,sing to the ri~ht of the tr~lsducer will be c].oser to the point L~4 than it is in reality.
Thi.s particular disadvantage can be overcome by diSpOSillg -the transducers in a vertica:l. orientation so that ~ the tr~lsducers are in the form of vertical discs ll6, 1~7, 48, 1i9l~(as sho~ igure ~), the planar faces of the discsbe ng directed towards the trainee marksman. As a bullet 50 2~ passes over the discs and the resultant shock ~lave is generated the shoclc wave will always impinge UpOIl the periphery oP each discg and the poin-t o:~ impingement of the shock wave on each disc will be an equal clistance ~rom the centre or origirl oP the disc. A cons-tant timing error will thus be

3~ i.n-troducecl i.l~.tO each signal generatecl by each transducer.

.

.
:,' ' ':' ': :
:, :, . ~ . ' ',, :

f ~ ~28~
Since on~.y the tinle d~ rerences are used as a basis fol tha calculati.ons tllis cons-t~nt error will bo cancelled out.
However, oricnting the discs in a vertical position will not obvia.te the problen, o:C the posi-tive plp 113 at the beginnlng of the output signal 42, therefore, in the present i.nventionS
i.t ls pref`erred to provide each trans~uce~ with a dome of a so.lid materi11 having a convex surface exposed -to the shock waves~ the planar base of the dome being in lntimate con~act ,witll the transducer material and being adapted to transmit shoclc waves ~rom the a-tmosphere to the transducer. Ir a hemispherical dome is utilized, provided that the a.xis of the dome is pointing vertically upwards in front of the target, or is directed towards the trainee marksma.n, or is at an orienta-tion ~etween these two limiti!lg orientations, the shoc]c waves 1~ generated by the projectiles flred at the target will always strike the periphery of the hemispherical dome tangentially, and shock waves will be transmitted radially through the dome directly to the center o~ the transducer. Thus a constant t:im~ g error is introduced, this timing error being equal to tlle t:ime ta]cen for the shock wave to pass f~oln the periphery o~ the hemispllerical dome to the center thereof~ and cas indicated above such a constant t:iming error will be of` no consequence.
It will be appreciated that -the hemispherical dome serves to preven-t or m;.nimi.ze the genera-ti.on of the positi.ve-going pip 43 at the beginning o~ the wavc form genera-ted by the transducer, and t]~us -the output o~ the transducer now :resemb.les more c:Losely a sinuso:idal wave formO However, it :i.s :i.mport~lt that the instant Or commencemellt of this si.nusoidal wave ~orm be measured w:i.tn great ac~cl~lac~ a~ld thus it :i.s preferred to : , . .

u-tili~e a trallsducer -that will have a very fast rcC.iponse~
thoug.ll not necessarily a large response. It is found that i~ t1le respoIIse -time of a s_ries o~ piezo-clect~ic discc. of di~ferel~t si~e are comp~tred, th~ rc6pons~ tirl1e :is a function of tl-le diameter of th.e c~:;sc, the su1aller di.scs havillg a faster respnnse til11e. ~owevera it has been found that a response ti1ne o~ all discs with 5 mm diameter or smaller are substantially equal. It is to be noted, howevL~r, that the amplitude of the output of such a disc is proportional to its s:;ze, and it is ~or this reason that it is presently preferred to utili~ie a ciisc having a diameter of 5 mm, since such a size pro~ides the fastest response tirn~ wl-th the ~-highest amplitude output signal. This si.æe of disc is also preferred since the output of a transducer provided with 1~ such a disc has a ~requency much higher than that of i~ny noise or interference likely to be encountered and thus such noise can be filtered out. However, it is envisaged that smaller f di.ameter discs may be preferred for reasons of improved accuracy.
With reference to ~igures 9 and lO of the accompanying drawi.ngs a preferred transducer for use in comlection wi.th the present i.nvention colr1pr.ises a transducer element cons:is~.ing o~ a disc 51 of piezo-electric material such as, fo~r example, lead zirconium titanate. The disc 51 is l mm thJlck ancl 5 mnr in diamete.r. The opposed planar ~aces of the 2~ d:isc 5l are providecd with a coating o~ a conductive rnaterial 52, such as silver which may be provided in any convenient way, such as by vacu~m~ deposition Two electri.cally conductive wire3 53, 54, I'or exa1nple, ot' copper or gold9 are com~ected to tlle center o~ the lower sur:~ace o.~ the disc and to the per:ip]lery of thc ~pper s-lrf`ace o.t` th.e disc by so:Lderi.ng or : ,.

- - - - - . : , . . .. :

.:., .
: :~ ' , ~ . ,'; ' . 'i; ' , ,, : .
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2~
by ultrasonic bonding The clisc 52 is then fi.rmly mour.l;e-l in a housin~ l~hich eomprises a cylllldrica] n~ember 55 havill~ a 5 mrn diameter recess 56 in one end face, tlle recess 56 having a depth of 1.5 mm, the recess 56 also being assoelcated ~ith an axial bore 57 e~tending tl-;rough the rr.ernber 55 to aeeommodato the wlre 53 pro~ided on the lower sur~aee of the piezo-elcetrie meinber.
A seeond bore 58, parallel to bore 57, is formed in the periphery of the member 55, this bore 58 being adapte~ to aeeomr,lodate the wire 5L~ and termillating in ~n open reeess 53 adjacent the main reeess 56. The me~nber 55 may be ~ormed Gf Tul`no~ hicll is a pllenolic resin borlded fabric, thi.s materi.al being re~dlly obtainable in cyli.ndrical formO The housing may be machilled froln this materlal, al-though alternatively, the housing may be ~ormed of a two part phenolie resin sueh as that sold under -the Trade Mark "Araldite", the resin being retainecl in a eylinclrica.l.
aluminium ease 60, and subsequently ~eing macllined: If tho latter e~pedi.ent is utilized the aluminium ease 60 may be eartlled to provide a ~araday cage to mi.nimize no:ise. The piezo~electrie ~naterial and wires are bonded in-to the member 55 with an aclhesive sueh as ~raldite or a cyano acryl:ic impact acUlosive. Two small bores 61, 62 are forllled in the lower surfaee of the Inember 55, and electrically conducting plns 62, 63 are mounted in the bores. The wires 53, 54, protruding from the ` lower ends of the bores 57, ~8 are soldered to the pins, and an 2~ adhesi-ve or other suitable setting Inateri.al is utilized to retain all the elements in posi-tion and also to secure a soLi~l}lcmi~plleri.eal dome 65 to the traMsclueer. Tlle dolr~ ma~
be machilled :~rom alumini.um or east from a ;ettlng resin mat:e:r.ial sueh a.s that solcl ~mdor the Tlacle Marli "Araldite"~
3 The cloms 65 ~rei`erabl~ has an outer diameter Or about ~ mlr~ hieh is equa:l.
31- .

: ; ,: . . : : : ~

r' `, to the dilmeter of the housing. ~ centrally disposed projection 66 on the base of thc dome member is adapted to contact the p;.ezo-elcctric disc 51 and has the same diameter as -the disc 51. ~l-ternati~ely, the dome and the memeber 55 may be cast as a single integral unit.
The pins 63, 64 protruding from the base of the holder may be connected to a co-axial cable, and the entire ~nnectlon ma~ be encapsulated in soft rubber. The coaxial cable may be short (i.e. up to 1 me-tre in length) and is eonnected te a suitable amplifier adapted to amplify the output signal generated by the transducer. In an alternati~e embodiment of the invention the ~ins provided on the holder are eonneeted directly to a printed circuit board upon which is mounted the amplifier, the printed circuit board being 1~ potted on to the base of the hous:ing.
The housing eouplHd with its assoeiated transducer, is mounted, as generally deseribed above, in front of the ~argHt, and it is important that both the housing and any cable emerging from the housing be aeoustieally decoupled from any suppor~ of any other rigid structure that eould possibly receive the shock wave detected by the transducar bofore tho shock wave is rec.eived by the hemispheriea:l. dome p~ovi.ded on top of the transducer. Thus, if the transdueers a~e mountHd on a rigid horizontal framework i.t is i.mpor-tan.-t 2~ that the transducers are acou.stica.Ll- rl.~-eoupled from sueh a framewvrk. The transducers may be mo~ ted on a blocl~
of any suitable acousti.c de-eouplin~ medium, such as an expanded polymer foam, or a comb:inat;ioll of polymer foam and metal platH. The mos-t preierred material is closed oell 3 foam polyetl-lylene, tl-lis material be:ing solcl uncler the Trade ~ . :

.. . , ,; :,. ..
, : ' ' . :' !, . ~ , . ~
, ' ' ' ~ , ' ' , ' .'. '' ' . ', ': ' ' ' .
,:' ` ' ; ' '' . ' . ' ~. ' '~ ~ , " ; ' ' :
' ' , . ,~ '' ~ ", ~ . ' ' ' z~2 ~lal-h :'Plast:i~o-te" by ~alcelite Xy.l.onite IimitedO 0~ cour~;o, many other aco-ustic de coupline .llaterials may be used suel-as g.~ass fibre cloth or mineral wool.
'l`he -transducer may be mounted by taking a ~lock 67 of acoustically coupli.ng medium as illustrated i.n Figu~e 11, ~ormlngr a hole or recess 68 withi.n the block o~ material dimensioned to accor.~odate the transducer and ~lol~er and inserl;in~ -the housing into the reeess. The 0ntire block may thln be clamped in any convenient way, sueh as by clamps 69 to a suit~ble framework or support 70, -these it~ms being ~illustratecl sc~lemati.eallyO
hen the transducers have been positioned relative to ~e target it is neeessary for inforsr.~tion concerning the p ecise positi.on of each transdueer to be suppli.ed to the 1~ eomputer together with in~ormation eoneerning the position o~ eacll target'relative to the transduee:rsO The appropriate distances may be measured carefully and the appropriate information may be fed to the transdueer~ or other nlethods may be used for supplying informatlon to the eomputer~ For ~ exanlple~ instead of measuring the dis-tanee betweeII the .
trallsducers with a ruler or the .l.ike~ a rod of metial may be loeated so that the rod of nletal is touehing eaeh of the trallsducers, alld an ult~asonie pulse may be propagated alon~r the rod of''metal, the time of arrival of the pulse at each 2~ transdueer being measured and reeorded by the computerO The . eomputer is provided with the spt~ed of the ultrason:ie pulse - wa~e along the Isletalli.e rod, and eonsetlllently the computer is able -to ealc~lla-te, wi.th ~ high c~egre'e o~ accuracy~ the l>reei.se pos:ition of eaCIl tr~nsducerO
3 [-t ~i.ll be apprecii.l-tecl -thclt when bullets aro :Li:recl , . _ .
~2 ~
. ....... ~ ,~

.. . . : " . .,. - , : .: .

,, 86~2 towards t.h~ targets tho position oE tho bul:ie-t is measu-etl relative to the tr.~1sducer, and i.-t is this position that is eventua]ly displaytcl by I;he computer. Thus it is important that the compu-ter bc provitled wil;h precise lnformation concernir1g the position of` the target relative ~o the transducers.
Tl1e an~plitud~3 of the signal generated by each Or the transduccrs as described above will depend upon the velocity of the bullet, the precise na-ture of the bulllet, the distance of` the bullet from the transducer, and many ~other variable factors.
l From the transducer signal it is necessary to obtain a - s:i.gnal whic11 can be utilized to operate a means which measures the time a-t which the shock wave was detected by the tr~s-l~ ducer. It is accordingly desired to change the analog trans-ducer sig11al oE ~igure 7 having an imprecise leading t-~dge, into a digital signal. The transducer signal is :Eed to i~n ampli:Eier which provides a digital signal havin.g a f`ast lead:ing edge, the amplifier being triggered by a shock wave but not tri~gered by any no:ise. The pref`erred amplif:i.Qr 71 ~ sho~l i.n Figure 12 of` the accompanying drawings a ant~ i-t is to bt3 noted that the signal is supplied to the ampli-fier along t11e coaxial cable 72, the two cores o~ the coaxial cable being f`ej past various biasing resistors to the input o.-E a di.f`~er-2~ ential amplif`ior 73. T11e ou-tput oE tht-~ di~:Eerential amp].ifier 73 is AC coupled. to a trig~er threshold comparator 74 in whic11 t.he ~:ignal is compared with a predetermi~td re~`erence s.ig11al to prevQnt l;ke onl;ixe apparatus bei11g triggered by IlOi se rather than a ShO ck wave '~.t3 trigger tllreiho].d 3~ . c:oll2paratQI 74 ma)~ be adjustetl to ~et t11Q th~.~es11o1.d se11sit-ivil:yO Tilo ~utput Or t11Q compal-ato:r :i~ ainp1iried w:ith a . . .. . . 3t :. , ,: . , . :~, , , ~ :

,: ~: .- , . . ~:

linear ~mpli~ier arrallgeJI)cnt 75~76S77 and ~n ampl:iI:i.od s:igncl:
is prov:ided at outp~.t 78.
Th~ component re:[erclices shown in Figure 1~ o~ the aecompalaying drawings identify the components utilise~l in S the preferxed e~.bodiment o:f tlle ln-vention, theso eomponl~nts being military grade components available f`rom Te~as Instrumen ts .
The output o~ the amplifier 71 can be considere~ a di~ital signal, since it indicates whether tlle transducer output is greater or less than the prcdetermined threshold.
As already i~ldicated the mathematical analysis given abo~e is based on the assumpti.on that the shock w~e generated by a supersonie projec-tile expand3 perpendieularly to the t~ajectory of` the projectile; while embodimen-ts of the invention based on the above mathematical analysis ha~-e pro~en satisf`aetory, their aceuracy cannot be impro~ed over eertain limii;s.
It h.as now been appreciated that when a bulle-t is f`i.red ~rom a gun such as a rif`le, at each instant o~ -time the supersonie bullet generates a shock wave~ each shock wave subsequently expanding spherically at a linear rate~ Fi~re 13 of the aeeomp~lying drawings illustrates the trajec-tory of`
a bullot ~lcl indieates the positions oecupied by the bullet at inst~n-ts ~ le ~i~ure also illustrates the sphcrical 2~ shock wa~r~s genera-ted by the bul]et at those instancec; 3 the shock waves all being il].ustrated at the instc~.t g4 -C-t will be appreeiated tllat the di.~meter of` the shoek wave at the position occupied by the bulle-t at t:ime ~4 i.s nil, whe:reas the d:i.ameter o~ the .shock wa~e generated by the bl~l.let at t.ilne .is rela-ti.~rely :Largev It will also be appreci.atecl ~rom l~:i.gllre 13 o~ the accompar~yi.ng drawings, -that the en~e].ope o:E`

35 :

,. I
.. ; . . .

~286~2 the spl~ores defines a gellcrally con:ica.1. shock wave, and since a shock wave ls generated at every installt such a con.ical envelope i5 generated.
~igure l4 i.llustratcs the tra;jectory of a bullet or other projectile approaching the target~ and also illustrates the shock wa~re genera-ted when the bul3e-t is at the posi-l;ion A
being detected by a sensor CO The bullet impi.Ilges on the target at the point B.
It is possible -to cons:ic1er the situation fro.~ a mathematical approach, initially assurning that at a tin1e T
the bull.et is at a position P somewhere on the trajeotory, and also ~y constructing a perpendi.cular from point D on the trajectory to the sensor C. The shock wave generated when the bullet is at point A on the trajectory is detected by the transducer C.
Conside~r a bullet tra~elling along the trajectory PADB ultimately striking the target at B. It is requi.rcd -to find the coordinates of the point B in the -target plane with respect to the origin O of the coordinate system.
P presents the position of`-the bulle-t when a timing perio~ is started. The shoclc wave ~l:ich eventual.ly triggers ~ the sonsox at C ori.g:inates from point A on the bullet tr~jectory. D is a point on the trjaectory such tha-t CD is pe ~ endicular to AD.
2~ 1 It is ass~ed that the bullet trajectory is linear over the (relatively shor-t) distance PB. Let T be a unit ..vector in the di.recti.on of the trajectory.
From the properties of shock waves from supersonic pro;jectiles, ~e ha~e that 3si~ o _ s .~ .. cØ.. (3.) b ~6 ---: , . - , ~:.......... :

2~6~
- where ~ is the velocity of sound and vb ~s th~J -~elocity of the bulletO
Now, the time for the shoclc wave to reach the sensor at C is given by t - time ~or bullet to travel ~ time for shock wave lo from P to A -I;ravel from A to C
Starting with this initia:L mathematical concept it is possible to derive a vector equa-tion relating the varlous voctorial parameters and t.
A similar equation will hold for each of the sensors .in the scnsor array, When the time t is lcnown for each sensor in the array it is possible to solve the equatiolls as a set o~ simultaneous equations. Xn one case the equations will earh contain five unlcnowns, and thus five equations must 1~ be,solved simultaneously. The equations rnay be solved iterative:Ly.
A rifle range tha-t is based on such a ;nathematical approach will now be describedO
l~igure 1~ of the accompanying drawings illustrates tlle - 20 al;rallgetnont of transducers 7~ Oll a range havine a plurality o~ lanes 80 flnd a plur~llty o:L target ban~ 81, The trans~lucers ' ' ` ' ., '.:',' ,' . ~

, , , , ! I .

'' ' ' `' ' ~' ` , , . ~ ,, 79 o~ each target bank 81 are connected to a tirning arrar~cr.l~n~
82 (uhich will be descl:ibed hereinafter) and the output o~ each timing arrangenlent i9 ~ed to a b-~ffer 83~ Thus referring to ure ~ of th.e accompanying dra-:/ing~ therc ~re three ban.ks of ta~gets 81' whi.ch provid~ si.gnal.s ~rom thc t:ransduc~rs to ~hQ
three timing arrange~ent~ 82~ and thus to th.ree buffers 83. The buffer~ are interrogated sequentiall~ by computing device r~ and when any in~ormation is available at the output o~ a buf~er 83, then that in~ormat~on ;.s transfcrred intc computing device 7 and subsequently the bu~fer is cleared. Each target bank is providod with a long row of transducer~ lo~ated in front of each target~ There is not a specific group o~ transducers ~ocated in front of each lndividual target. It is to be ~ppreciated that in utilising an arr~lgement in which inform-1~ ation ~rom each bank of transducers is stored in a buffer, with the buffer~ being interrogated by a single computing clevice, the amount o~ wiring needed on. the ra~ge is minimized~ since othel~iise each transducer would need t~ be individually connocted to a computing de~ice.
Re~erring to Figure 169 each timin~ arrangement 82 compr~se,s a group o~ tristate latches 84~ each latch being connoc~ed to the output of the ampli~ior 71 a~ociated with an individual transducer. I,atches 84 ~ay be o~ the type sold b~ ~.
Telas Instruments ~lder the ref'orence number 74363. Each of' the 2~ trlstate latche~ 84 is connected to a.n output o* a 24 bit cloc~
signal gelleratc)~ 85~ generator 85 provicling~ successlve Sigllcal9 .
indicat.ive of` the precise tim~. A new signal is generated eve~-5~ ¦~
ten nano seconds. The a.rrangemc-~nt 1'S such that ~hen. the digit~l si.~lal i.s provided f'.rom the al~pl:ifier 71 as30ciated Wit~l a t~ansdllcer to a la-tch 84-~ th~ latch will ~ecord the 24 ~ cJcsc3{

. ,.. ,. ~

:' ~' , '' -,.. ' . : :
,, :
,, ~ ~ , .. . .

,6~
9ig~nal prcs~nl; on th~ output of the 2l~ bit clocl~ sig~al gonerator 85 at that in~tant, The digita], sigllal from the ampli.fier 71 is also fed~ ~imultaneou~ly, to a control dc~ice 86 which sub.sequently causes tllc si~lal recordcd on tho latch 84-, together with a signal permanent:Ly rccordcd on a rcad ol~ly memory 87 associated with th~ l~tch, to be transferred to the buffer 83. The signal stored on the read'onlr memory 87 is a signal which identifies the transducer a,ssociated with that particular :Latch 84. The buffer 83 i a "first in~first out"
t~pe device and temporarily stores the informatioll~ The information stored in the buffer 83 comprises the time signal temporarily stored in the latch 84~ and the transducer ic3,entit-,y slgnal permanently stored in the associatecl read onlr memory 87 Once this information has been acceptéd-by the ~uffer 83, a 1~ further control signal is sent to the latch 84; the latch then clears and is ready to store another signal from the c].ock signal generator 85 on receipt of a further shock wave from the associ.ated transducer. Thus~ the buffer 83 will storc a large um~er of separate items of information~ each item of info~nation compr.ising a signal identi.fying a particular transducer and a slgnal represenlative of the time of receipt o~ a shock wavc by tllat particular transducer. Of courser if t~o successi~e shock waves are detected by the same transducer~ t;hon two succe.ssive signals will be temporarily stored in the assooiated buffer9 ~5 comprising the same transclucer identiPyingr signal9 but having different signals representative of the time of receipt Gf a shock wa~e by that tran3ducer.
I~hen a sig~al. stored in the buffer is a~ailable in tlle output of one ~uI`fer 83, a sig~ilal is ,orwarded to cause '~O compul;i~g clevice 7 to l.nterrog~.t;e eacll of the buffc,r~ acc~p-ting ~ -- 3~ ~

:, . :, . .

86t~
lnformat:ion ~rom thta ~uff`er ~3 that has info~n~ltion presen-t On its outputO Referrill~ now -to Figure 17~ information ~ro~n the bv.~fer B3 i3 fed to ~ first mini~computer 88 a~ 1rell as to a memory 89 present in the computing assembly 7. These components9 and othe~ components presen-t in the computin~ assernbly 7, are connected together by a maxibus 90 (shown in Figu~e 17 in thta accompan~ drawings)~ The arrangement operates in real time1 that i9 to say, time not shared bet~een the various components, but the components optarats independently of each other~ and the components may thus operatta simultancously. The mi~i-compllter 88~ 1~hich may be a Texas Instr~ents T~IS 9900 computer associated with a local memory cornprisillg an Intel 2102 memo~y~ initially scans the data received from the bu~fer and compares the various tinles of reception o~ the shock waves by the transducers. ~rom tllis lnitial comparison various "groups" of received signa].s a~e identified7 each such group of signals comprising shoc}~
wave detection times wi-thin a prede-termined range and -thus beln~
si~nals that are possibly derived from a single projectile. ~or taxanlple, as a projectile passes over the transducers the shoclc wa~e ~enerated by that proJec~ile will be detected ~y ~ive or 9:iX ~l'allSdUCerS of a long row o~ transducers located ~rLder t'ht~
tnrgets at wl-:;ch the projectile is aimed. The~e transducers will all detect the shock wave within a comparatively short period of time, and thus the signals detected by the transducers can easily boldistinguished ~rom the si~Lals received by thta transducer~
~oin a subsequelLt projectile, since the si~Lals recei-ved from tht2 su~set~uen-t projectile ~ill be much latar in -time.
As lndicated a~ove~ the ml~i~computer 88 seletcts li,kel-y groups o~ receinved sigllals and ~teteds ths signaJ.s -~o a special purpoCle calcu:iator or p~e-programmecl general p~rposta compul:tar 6~;~
91 having a P~0~ (progr~mmed readout memory) which subjec-ts the input d~t~ to the prodoter~ined mathQ~Iatical operations de~cr-ibecl abo~re9 and provides an output s~gnal represcntative of the po~ition o~ the tra~ector~ of -the projoctile.
It is pr~ferable that the programming of unit 91 i~
cont~i~ed in the hardwar~ of the device, so that no software progra~nme is necessary~ Thus the device can operate at a very high s~e6dJ Such an approach is feas-ble ~or this port.ion: of` computi~g arrangement 7 since uni-t 91 will only be required to perform one mathematical f~nction However9 it i5 t:o be appreciated that a softl~are-programn~ed computer could be used, provided that such a co~np~ter was able to operate ~lth su~ficient speed. A~ter the maths unit 91 has calculated the position of ~he projectile trajectory relativa to the target ~rea, that infvrmation is fed to memory 895 and from there to a visual dlsplay assembly 92.
The visual display assemblr 92 comprises mean~s fOI' generating a signal which~ when fed to a cathode ray tube~
causes that catho~ ray tube to display a rep~esentation o~
a target. :Ref~rrlng to Fi~ure 18, the pre~erred ~eans for genorating such a signal comprises a closed circuit television cnmela 91~ c3sociated with means 9~ for projecting an image on a photogrlplli.c slide 96 into the camera. l~lc camera 94 operates in the usual way and thus produces a video signal 2~ r~p~esentative of the image on the slido 96~ A190 present o~l the sl.ide 96 are vari.ous ~narks o.r lines defln:ing X and Y
axes~ tho position o~ the tar~et be:i.ng known ~ith regard to tihese axes. Part o~ -th~ vi.deo s:igrnal from the cam~ra is ~ed to t~.o sepQ:rate ~e te~ctor ci~ouit~ 97~ 98~ wllich are adapted t:o detec~ tha posi-tiorl o-f the heam ~canni.rl~r ~he -ta:rget ~.. ~,, ` ~ ` ` ' ~ . .

64;~
iII the camera at any instant~ the dctf~ctor circuits 97~ 98 bo:ing connectcd to a blallking de~icf 99 adapted to bla~ out tllat part o~ the vide~ sif~rnal which rela-tQs to thf3 marks de~ining the axes~
Th~ls the resulting vidoo signal o~ lin~ 100 comprises only a part o~ the ~ideo signal generated by the camera 94~ that being the part vf the s.ignal representati~e of the image of the ta~get.
The signals generated by the X detector a~d Y detector are also ~ed to a ~eparate comparator 1019 this comparator being provided with informa-tion, ~rom the computing device 79 compris ing the precise position of each proJectile det~cted by the system. The comparator 101 co~.pares the posi-tion of the p~ojectile wi.th the signal~ from th~ X detector and Y detector, and when the signals correspond, that is to say when the beam in the camera 94 is direct0d at the area o~ the image projected tO the camera 94 correspondi~g to the area of the target 011 thc ra~ge that has been impinged by the projcctile, then the comparator pro~idos ~n output signal which is fed to c~n exclusive OR gate 102. T~e OUf;pUt of the blan~ 99 is fed to n cathode ray tube 103 via the exclusive OR gate 102, and it will be appreciated that the cathode ray tube wi.ll d.isplay an .image of the target derived by the camera 94 .~rom the slidc 96; and ~ill al.so display~ o~ that image, arear l~here the color of the image has been re~srsed indicative o.f the points of the target impingred upon by t~le bullets or pro3ectiles fired 2~ on the range. 0f course~ it is ass~ed that the bu110t or projectile will implng~ upon. tlle target at the position calcul~
ate~ by the comput~r :from the informat.i.on lerl~red b~ the transducers~
0~e ~l.sual d:isp1ay unit 92 Illay be pro~ided ~or a range control].c~ and the xang-3 controller may sel~3ct any ~arget o~ ~e plurali-l.y o~' t;ai~get.s on t;he raIl~e a.~ bf~in~, a -targf3-l; o .. . , . . ., .,, . .. . i .

4;2 illteresl:, and then th.e visual d:i.splay wlitt ~rill d.:isplay a represent;ation o~ tllat particulaI target and a represerlta-tion of the posi-t:ions at which projectiles fired at that tal-get hav~ impinged on thc -target, or passed by the target.
plurality Or such vi..sual displ.ly units may be provided ~`or plurality of r~n~e controlle~s, and .indeecl, as envisaged in tll~ openin~ para~raphs of t'h-is description an individual.
display Ullit nlay be provided for eacll trainee mar~sman so that the markslllan Inay il~nediately see where each bullet goesu It i.s en~isaged that in a range in accordarlce with the invent:;on the individual. targets will eaeh ~e associated with ~ meella~ism for raising the target to an exposed pos:i.tion a~ld lo~rer~ -the target to a concealed position. These mechanisms may ~e controlled by the compu~er assembly~ and tlle cotllputer assembly may inelude a users programme store 104 Oil whieh a predetermined progran~ne of`lnovements of the targets may be stored, the targets executing these predeterlr.ined mQvelllents ~hen the stored programme is aetivated~ A second ~ mirL~colllp~lter 105 which again may be a Texas TMS 9900 eom]?utQr ,!0 may l~e pro~icled connected to the nlechanical cleviceiY 106 ~hi.c]

arc provided -to move the targets, tllis computer recording -the pos:Lt;:ion o~ each part:icular target and c]leclcing tlle correct ~unetioning~ of` each particu:Lar targetO A rurther visual display ~Ln:it 107 may- be provlded i.n such an embod:iment oI` the invention, th:is display un:it displaying itnages dep:ic-l,lng~ the ~-arious targ~c-ts present on the range, the display present on -the ~isual display unit at any part:icular tlme belng ind:icative of the condition o~ each target, -tllat is to say, whether l.lle tar~et i:.-> in clne rai.sed pos:ition oY~ ;.n tlle lo~ere~-3 pos:il::io.L, .~ncl also inclicat:iil~, t;~)e nurl~er o.t' hits tha-c have , . , ~43~
.. , . , . , . . :
:

,. :.
- . : .: . . .
. .
.: '.

864;~
been score'-l on any par-tictllar -targetO It i:s envi~aged tllat this particular v:isual d:Lsp].ay unit will t>a provided f->r a suparvîsory ranga controller who may~ from con~iderin~r the ~risual display ~lit 9 a~se~ the precise condition of each target present on the range, This visual disp:lay uni~ is also adapted to indicate a mal*unction of any par-ticular target~
A printer 108 is also associated with the computer assembly~ the printer be.ing operable to provide print-ovts of any of the information present in the storeO A paper pu~lcher may also be providedO
The main computer 109 which provides a controlling function is preferably a computer ~old ~y Comput,er ~utomation (Naked ~lini Di~ision) of Ir~ine, California9 as computer OS 1 4~10~ the users progran~te storage 104 is pre~era~ly a floppy di,sc s~ib system model 1~566-XX as sold by Computer Au-tomation, the main tnentory 89 is preferably a core mernory of` wp to 32 K
words as sold by Computer Automation~ and the preferrod printer 108 is a Centronix 306, also a~ailable from Computer ~utomation~
It ~Yill be appreciated that rllany modifications n~ay be ma~e~ arld the computer may be provided with :~acilitie,~ ~or calculati~g a score attrib~table to any particular projecti.le~
this score being d:Lsplayed Oll tho appropriato ~isual display it.
~ ~lo targets uti].ised in a range in accordance with the present in~ention may be static targets~ may be targots that ~lse and fall in rcsponse to command signals a3 sho~m in Fitg-ure 1~ or may merely be sprays of`~Yater or the lil~e with vi~ual images replesent,a-tive oI' the targets projectad on -them, '~f the ~.argets are of thc? -type that rise and ~all.~ the tar~rets ma~-be remoto eontrollecl by ~ig-na:l.s oll a oable9 a5 d.eSCribC?d abO-~C?9 . ; , . ' ' . '',., . ','" , " ~ :

2 !36~2 althou~rh t;h~ t~rg~t~ may be con.trolled by radio ~i~nals, '~Ae comA~uter may b~ operLlted to caus~ a tar6ret to ~all briefl~r~ ene~er the target i5 a.ctually hit by a trainee marksmaD.. F~rthe~more, while th~ invontion ha~ boen described ~ith refer~n~e spec:ifically to a fixed rifle range9 lt is to be appreciatec. that the i.nventi.on may be utilised in a ran~e ~here targ0ts mo~e along on trolley.s~ the tr~ns~ucors also being mounted on the trolleys ln a fixed position relative to the targct;sO AlterrAatively~ the invention may be utilised in connection witll groun~to-air or air-to air weapoA7~As tralnlng~ in ~hich case the transducers would be ~ounted on the droguo ~Yhich i9 the target~ .
h~n a range as described above is utilised for ~raining a large nunl~er of mark~men the computer which is locatecl at a central control console may perform many functioIls and tho precise functions performed by the computer may be controlled ~y vario1l~ push buttons o~ the llke pro~ided on ~.
the control console.
Initially the oomputer ma~ be adapt~d to calculate the position of each rol.md fi.red at oach targot and to provi.de sig~1als to vis~al dlsplay units pro~i.ded a~jace7lt each trainoe marksman so l,hat oach o~ the visual displa~
units displays a represe7ltation of the ta~get at which the trainee marksman is aiming~ and also pro~ides an indi.catio f the poll~ts at whicll the trairAee mclrksnl~l has hit tha target in any particulal- firing session~ '~hus~ if a traînea mal~ksman i9 to iire t~n rounds at the -ta:rget~ as t~e rounds are successive l~r fired a-t the target s~o tho position of impact oi` t,he rourAds 0.71 the ta:rxet may ~e dl~played on the approp~:iate vi.su~l di~pl~r ~n.it, . ~ ~5 .. . ... .
, .. .~
. I ~ , . . .

L2~36~Z
Of course~ near-misses can also be disp].ayed uI)oll the viLsual c~isplay unit1 since such near-ln:isses ~ill be detected by the transducersO At tlle enc1 of a shooting session if the marl;sm~n has beon reaso~ably accurate in his shooti.ng ~ there should be ten points mar]ce~ on the representation of the taret~ indicating precisely wh.ere the rounds have hit ~he targetO It is possible that the various po-ints di..splayed on the display unit may be associated with numbers indi.cating the precise order in ~hich the rounds were fired at the target, thus permittirlg the marksman to assess whether his accuracy ~as improving or not during the shooting session~
The computer may also calculate for each target fo~
e~ch shooting sessi.on in the overall dimension of the ~'~roup" as fired by the training marksmanO These figures l~ may also be displayed on the individual display unit 9 provided .
~or each trainee marksman. Alternatively, the number of "hits" alld tlle number of ~misses~ may bc recorded and displayed~
o~ the score obtained by the marksman may be ~isplayed.
It is envisaged that the computer 7 may be progran1med .o draw tlle attention of the range controller 1;o any trainee mclr]{sman ~ho is firing very irlaccura-tely to enable the range controller to provide that -trainee marksman wi-th instructions or advice. The central control console is provided with a . display device 8 enabling the trainer instantly to vie~ a 2~ representati.on of any one c)f the ta:rgets~ thi.s rep:resentati.on corresponding prec:i.sely with the representation sho~ on the visual display of the appropr:Late trainée marl~sman. Th~s the t~-aine~ lay mon:itor the progress of each trainee Inarksnla~
l`he prlnter 13 may merely print the score and group:i.ng 3 o1~tc.i.ned L~v each of t]l.e ~.rainQe mark~;men duri.nf~ a ,hoot:i.n.~
":

LZ8~
~ sessivn, or the pxintt-3r may be operate~ -to provide a p.rlnl--out re~resent~ltion.of any o.r all o.~ the targets includi.hg a represelltation of the points at which each of the tar~ets has been hiit by bulJe-tsO Such a prirlt-out may constitute a permanent recorcl o~ the shoo-tirlg of any particulair markslnall.
The targcts 3 utiliscd with the present invention may be static targets, and it will be appreciated that since the targets onl~r function as an a.iming mark it will not be necessary to replace any target unt:il the target is virtually totally destroyedO It will also be appreciated that tlle ~invelltion may be used with advantage in connection with targets that can be moved i`rom a concealed position to an exposed or ~ring position, and vice-versaO Targets of this type are illustrated in ~i.gure l of the accompanying dra~ings, The l~ invelltion may also be used in co~loction with targe-ts mounted on trollies for nlovemeIlt along a predetermined track, the - -tr~nsducers also being mounted directly or indirectly on the trolley ror mo~ement with the target~ 0~ course, the invention Inay be ~Ised ln conjunction with man~ facilites, such as ligllts . to illuminate the target to perrnit shooting to be contlucted a~ter darlc, antl means on or adjacent tlhe -target to si.mulate retaliatory fire, Such means may be controlled by the computer to be operatcd in response to a shot fired at the target but ~.~hich is a near miss. Many further possibilities will suggest thelllselves to tllose skilled ~n the art"
~ 'rhe Inal-henlatical analysis given above presumes that the aiF in ~]hicll the projectile is fired is still, but if the range is an open ai.r range the poss:ibility al.ways e~;is-ts that the t~:;nd may be blow:LngO Thc following imathenlatical arlalys:i.s 3 ta];es aCCOUD t Or th.e e~`fect of ~incl~

~ ~7 .. . . . . . ................................ .

,~ ' . .. : . :, .

2~6~
Referriny to Figure 19 a bullet travels along the trajectory PAB, even~ually striking the target at B, whose coordinates are to be found.
The shock wave which eventually triggers the sen-sor at C initiates at point A on the bullet trajectory.
P is the position of the bullet when a timing period is started, i.e. P represents an arbitrary orgin of tlming .
o, a point in the target plane, is the origin of our coordinate system.
Now let the total time for the signal to reach C
from P be t, t is made of the time taken for the bullet to reach A and the time taken for the shock wave to reach C
from A, Let these be tl and t2 respectively.
We can regard the shock wave motion as being a spherical expanding wave front in moving air, In tim~ inter-val t2, the centre of the spherical disturbance has moved from A to R due to the effect of wind, while the disturbance has expanded to radius RC.
Again it i5 possible to define a vector equation relating various vectorial parameters and the sum of tl and t2 .
For example such an equation will relate the time of arrival of the shock wave at a sensor C~ to the position of the sensor and the coordinates of the bullet hit position in the target plane.
A similar equation will hold for each of the sen-sors in the array, and sufficient sensors will allow equation to be solved for the various unknowns.
In practice iterative methods may be ado,pted for solving the equations.

. ~ ,~, ,. , " , .
- :

~. ~ . . . . .:

12136~Z
~'rhell ~ d i. S tak.cll iJ-ltO ~lccollnt th_r- are mor-~
unkno~TIl.s and thu~3lll0re itcms O:r i.npll-t data hav~ to 'be availa~le to exlabl.fe tlle pos:ition of the projec-tile to be de-termined. l~l)en solv:ine simultancous equa-t:ions ther3 h~ve to be ac many equa-tions as there are urLknowns~ and thus d large~number o~ time differences have -to be measured i:f accurate results are to be obtainedO
¦In an alterIlati.ve approacll to the problems posed by the e~istence of wind the speed and direction of -the wincl may be measured and fed to the computer, and due account of the willd speed may be talien into account in perforn~ing -the necessa.ry calculations~
¦ One convenient way of measurlng the w:ind speed, or a~ least me~suri.ng the erfectc Of tlle wind speed, is to 'provide one or more sound sourccs, such as sound emitting transducers, located at predetermined poi.nts relative to the transducer array. The sound emitting transducers are controlled by the computcr and emit sounds of such a frequency that tl~e~ may be del:ected by the trans~ucers, The transducers ~ ancl tilning devices measure -i;he time of detecti.on of the SOUlldl~aves ~enerated by the transcucers and these times are compa~ed w.ith the times at which the transducers are cactiva-tedO
This comparison enables the effects of wind to be measured accurately, and the ePfects of wind can t'lUS be monitored instant by instant~ and at several pa.rts o~ the ran~e. This is of parti.cular use in bl.u-tery concl:i.tions.

~L19,~

-.`, , ,: .

- . , " . , 836~2 transducers enable accurate results to be obtained if the projectile has a known oblique incidence and there is no wind, six transducers enable accurate results to be obtained if the projectile has an unknown horizontal component of incidence and a known vertical component and there is no wind, seven transducers enable accurate results to be obtained for normal incidence and an unknown wind factor, and for known oblique incidence and an unknown wind factor; and eight transducers enable accurate results to be obtained for bul-lets with an unknown horizontal component of incidence and aknown vertical component of incidence if there is no wind.
If the transducers are in the staggered, two row arrangement, six transducers enable accurate resultsi to be obtained if the projectile has a known horizontal component of incidence, an unknown vertical component of incidence and there is no wind, seven transducers enable accurate results to be o~tained if the projectile has an unknown in- ;~
cidence and there is no wind, eight transducers enable accurate results to be obtained if the projectile has a known horizontal component of incidence, an unknown horizon-tal component of incidence and there is unknown wind factor, and nine transducers enable accurate results to be obtained when the projectile has unknown incidence and there is an unknown wind factor.
The numbers of transducers listed above indicate :
the number of transducers in the group selected bv the computer, and timing signals must be received by the com-puter from the ~ , , , , ' ' ' ' ' !
', ' ' ' ' ,', ;, : ~.

,' , . .. ~ ' ' . . ' ~:

` `` ~L~2~ 2 spcclficd n.~ ber o:f~ t;-lansdllccrs 1~: tllC position Or a projeci,i.le. i.s to bc cal.culatcd accurat,ely in each of the spec;.~ied set o:~ concl.:it:ionsO
Olll t]le fOregOillg it will be apprcciated thcat on any occasions it i.s preferable to mount the tral~sducers i~l .a staggerecl o:r non~linear arran~ementO One pref'erred method of mounti.7l~ the trallsducers in this ~ashion is illustrated in F:iglre 20~ The tx~ansducers are mounl;ed within appropriately spaced apertures 110 :~ormed in a pane7. 111 compri.sing a oentral rlg~id sheet of metal 112 tha faces of which are pro~rided witll sheets of sound absorbing material 1130 The domes 65 of the transducers protrude from the front face of thc panel ll:L and are thus exposed to the shock wavesO
The reax~ encl oI' each transducer is provided with a radially l~ extending flange 114 which is adapted to contact the rear sur.~ace of th.e panel 111 to assist in locating tlle transducersO
The aperturc!s 110 can be accurately locatcd by drilli.ng the ap~r-tures ~rith an appropriate jig. If the spacing between the aperturcs tends to vary w:i.th varyi.ng temperature as a rcsult of th(~rn~al e~pansion means may be provided to measure the telnpel-al;ure and to provide compensati.ng i.nforr~ation to the computer 7. Tlle panel 111 may be as 10ng as dosired, and rnay accolmllodate as Inany transducers as required~
The transduce:rs may detect secondary shock. waves 2~ gcller.l-ted ~rllell thc projec-tile lnl~?inges on a rigld targret located adjac,ellt the transducexs~ Tlle timi.ng de~rices, and thus the conlputerS ma~ be ullable to disting~ll.sh bct~reen such scconciar~y shocl~raves~ alld l,he shock ~ra~es that are ge~.exated - p:r:imaril$~ by tlle projectileO Ti].us it is pre~er:red to local;e tlle Ineans ~.ll support;lrlg 1;1le tra7lsduc~rs acljacent a blocl;
.

, ~ ; '. .::: .

'. : , . ,~ .

8~;~2 Or sound abs()rl:~inL~r ~late:r:ial or otller so-und absorb:LIlgr nled.i.unl;
locnted betw~en the t:ran.lclucerg and thc targret :L16 as sho~n iIl Figure 1. A sh.ock wav~ trave:L:Ling in the direction of arrow 117 ancl ge:nerated by a buli.et wil]. thus be detcc-ted by -the transclucers, but a shock wave emana-ting from the target and travelling in the dircction of arrow :L18 wlll no-t be detected by the transducers. Thus -the transd-ucers are in the shadow of -the member 115.
Figure 22 :illustratcs ano-ther embodiment of a ra~ge utilising appa.ratus in accordance with the invention. One set of transducers 120 are located below and in front of c?
set of static -targets 121. These transducers 120 arc connected to the computer 7 by a land linQ 122 as described ~bove. In addition to the static -targets 121 there is a.
radio controlled target carrying self propelled troll~y 123 which is movable along a monorai.l track 124. The trolley 123 carries a target which is a representation of a tank.
A set oI` transducers 124' ar~ mounted on the trolley and signals are set frorn the transducers 124~ to the computer 7 via ~0 a rad:i.o link 125. A second radio link 126 is provided to enable control signa:Ls to be set to the trolley 123. ~any othQr rang0s nlav be designed ~rhich utilise the present inv~ntion, such ranges having static or trolley mou:nte(-l targcts, targets that can fall automa-tically when hit arld -targets ~hat are especial:Ly illurninated for n:ight t:ime shoo-ting.
Fi.gure 23 illustrates the tra;jectory 127 of a bullet ~hich passes over three transducers 128, 129, 1.30.
The bul1.et gellerates a conical.shock wavc~ as the bu:Llet trcavels a.l.ong -the traiectory 127 and at the in~-tant a-t ~hi.ch the bllllct reaches the point 131 the transducer 129 de-teicts :, : 51~ .
~.~
. , . ., , . ~.. ~ . .", . ~.. - , :, t~e COlli.C~ sl~ocl; wavc generated by t:lle bullet. It can easi]y ~c sllo~ tl~al, -the bul]et actuLI].].y irlitia-ted tlle por-tion o:~ the shocl; ~ave detected hy l;he transclucer 129 when th.o bullet was a.t the pO:iXl ~ 132. ~n this speclri.c e~ample, -the next -transducer -to detect the shock wave is the tral1sclucer 128 wlli.ch detects the shock wave at the :instant -tha.t the bulle-t reaches the point 133. It can 'be sllown that the por-t:i.on of the shock wave detected by the -tra,nsducQr ].28 was genera-tecl when -the bu].let was at the point .0 134 on the trajectol~. Simi].arly the portlon of the shock wave detec-ted by the transducer 130 will have orlgina-ted at a differellt point on the trajectory of the bullet, and thus it can readily be appreciated that each portion of the shock ~ave that is detected, in a typical case, wi~.l have been generated at, a different point on the -trajectory of the bul.,l.et, It has been noted that in many cases as a bullet passes throu~l air the bullet is subjec-ted to retardation md thus the bullet is -travelling at di.fferent speeds at the various points on the trajeetory at which the bullet .?~ aetually generates the shock waves which are subsequently detectecl'oy the transchlcers. This leacls to an error and under cert;aill circumstances the apparatus may provlde inaccurate results.
In order to overeome this particular difficulty a sh:ielding means is provided in ~ront of t,he transducers.
l~igure 2l~ illustrates an embodi.ment of the present inven-tion ln whicll transducers 135 are arranged ln a li.near row and a shield member 136 is provided which shields the transducers 135 from the coniccl shoel; wave gellerated i.n all regions '30 of space e~cept a specifica.lly defi.xlecl reg:i.on ~l-ich ls bounded ~ 51B -.. . : : ~ ~,;
. .
.

`: ' : ' : , :~

~ 86~;~
by a singlc,~ pla.ne. The shi.eld member 13G compr:ises a sill~le silnple elonga-te member which ex-tends hori~or~ ta:Lly in ~ront of -the -t~callsdllcer,s and whictl terminates almost directly above -the tr~msduee:rs, Tllis ~:r~ectively derines 1.
a "hor:i~on" for the transducers 135 and the tra~sclucers can detect a shock wave originat-;ng above this "horizon" but cannot detect a shock ~ave origi.nating below the "hori~on".
The member 136 thus shi.elcls the -transdueers and sinee the shock waves generated by a supersonic projectile compr:ise the envelope of a plurality of success~ve spherically expc~lding shock waves it will be appreeiated that the first shock wave detecte~ by any transdueer 135 in tlle row o~
transducers will be th~shock wave genera-ted by the projectile ~t the illstant that it passes through the plane ~hjch is defined by the row of transducers and shield rnember~ namely the i.nstant that the projeetile rises above the "horizon". .:
Thus all the transdueers in the row of -transducers will del;ect the shock wave that is generated a-t a single instant during the flight o~ the projeetile arld eonsequently all 2() errors eaused by retardation of the projeetile may be obv;.ated.
The angle of inelination of the plane defi:ned by the trlnsduee:rs and the "horizorL'SIllust be such that t~le plane intersects the trajectory o~ a bullet at a point closer to the transdllcers than the point of` origin of the ~irst shock wa.ve that woulcl be detected by the transdueers if the shielcling nleans were not there.
Figu~e 25 illus-trates the shieldi.ng means .136 and a transducer 135 and also .illus-tra-tes a l~ullet passing along a I;rajectory :1.37 gc,~nerating a conlcal .s]Lock wav0 13So Flgu-25 a:l.so -l.l.l~-L.strates tlle target, 139 at whi(11 the bullet was ~irec1 _ ,'j~ (! ~

- - . ~ : :; , . . .

2~36~æ
- Figurc 2~ illus~rates t]le situction ~f`-tel a ~rief per;.od o:~ t;.llle ancl sl~ows that t~-e shock ~ra~Te 138 has advarlc~cl, but has no-t :impinged upon the transducer 135.
~igure 27 illustrates the situatioll a:rter :f-urther brleI
per~ocl of tirn~ and shows tha-t tll~ conica.L shocl~ wave does not impinge UpOIl th.e transducer 135 since the shi.e.1.d 136 de:~i.nes a "slladed" area whieh is bounded by the plane 1ll0. Within the region def.ined by tlie plane lLfo a spherical ~rave 141 is forrned, this spherical wave impinging upon the tran.sducer ~35 as illustrated in Figure 28 which illustrates the situation at a later pOillt in time. :Ct ean be seen that the spherical wave that actuall-~ impinges on the transducer 135 or:igi.nates ~rom a point 142 which. is de~i.ned by the shield 136 and -the transducer 135.
It is to be understood that whilst the plane de:fined by the transdueers and the shield mav be inclilled it is preferred for the pl~le to be substantially vertica.l. Th~ls tha "hori~on"
is substc~ntially vert:ieally located above the transclueers an.d thus the transdueers only deteet the shoek wave or projeeti:Le gonerated by the projeetlle when the projectile is immediately above the -transclueers. l`he shielding means 136 ma-y comprise an elongate eonerete member or a metal strip.
It has been found that tlle overall accuracy o~ a range i.n~aeeordanee with the presellt invention may be optimised i~
th~ transdueers are arranged i.n a specific array. The preferr-3d array is illustra-ted ln ~igure 29, and it is to be no-ted tha-t the array comprises two linear rows o~ transducers `-142, lL~3, the rows pre~e:rably being parallel 9 a:nd the transducers being evenly spaeed in the rows9 tht3 transdueers o:~ ol~e I`OW 11~2 be:ing substantl.a.l.ly co-allgned wltll the _ s~D -. . . . ... . ..
. .
- ~ , . .. : ,., :.:
` ....... : ,, , :
:: . : .: : . ,, , ,:

, :. , .:. ::

9.~L;28~
-~ transclucers 143 of` the o-tller ~ow. The two rows may bc in a si~gl.e horizoll-l,al plane~ or may ~e i.Jl a vertical pl.ane or may 'be in a pl.~ne at any inclination. Th.e transducers a,re pre~erably loc~-l.tecl in froJlt of~ the target ].L~ but the row of transducers ].Ll2 i9 pre~erably substantially in the plane of -the target 144. Where two rows of tran~sducers arc providecl as illustrated in Figure 29 each row of transducers may be provided with a separate shielding means 136 as illustrat,ed in Eigure 24. In such, an embodiment of the invention the shock ~ave gensra-ted by a bu]let as it passes -through each of two pla.nes will be detected by the transducers of the respective rows of transducers.
Fi.gure 30 illustrates a weapon in accordance with the invention ~or use w:i.-th a range in accordance with t;he invention as described above 9 although. the weapon may be used in other ranges. The weapon comprises a con~entional rifle 145 7 but it is to be appl~eciatecl that the weapon may be any other conventional type o~ weapon. The rifle 145 is provided with four pressure sensitive transducers 1~6, 147, 148 and 149, the pressure sensitive transducers being located at -the parts o~ the ri:~le that are engaged by t~e trainee marlcsman when the r:;~le is being fired. Thus there :is a l.ransducer 149 in the ~utt of the rifle 9 that '`
~eing the part of the rifle that is urged against the shouldsr of the trainee marksmsn. There is another transducer 148 at the cheek of the ri~le, that is to sa.y the part of the rifle that is engaged by the cheek o~ tne trainee marksman.
Furt,her transducers are pro-vided at the !nain halld grip 147 ~nd tl~e fors-hancl grip 146 of -t;he rifle, -the~se being t;he par-t 3~ o:~ the ri:~le actually gr.ipped by the h~nds Or -the trainee _ 51E -. / ~; . ;, ~ ' .' ' ' ! ' ' , .'., . . ' i ' gL~2E36~;~
marl;srnall. Tlle pressllre sell.s:itive~ trallsdllcers Illay be releasal)ly attach~3d to -tl~e rifle, bu~ i.t is pr~f`errod -t~iat the trans~uc~rs a-l^e int~grally ~orlne~ ~ith the rl~le so that t~le sur:~aces o:C -the trcmsduce~rs are rlush with the remaining surraces o* thè r;r:L.e and so tha-t thc rifle has the same ":~eel" as a rifle not provlded with the transducers.
Th~ ~ransducers 1)~6~ 9 may be of any convenient type, and thus may comprise a strain-gauge type transducer ~ ich~ as an increasing pressure is applied to the transducer 1.0 cause an increase in strain to be applied to an elongate w:ire, the resistivi-ty of the wire baing measured and being indicative o~ the s-train applied to th.e plates, one plate being smooth and the other plate being provided w.lth pyramidal projections extending towards the *irst plate, the plates being separated by a th:in sheet o* rubber or other such insulating material. As increasing pressure is applied to the transduce:r -the insulating material will be de~ormecl by the ~pyramidal projections and the electrical resistance and/or capacitance batween the two-plates will vary. This resistance and/or capacitance may be measured electronically by apply:ing a voltage across the pla-tes and observing the resuLtant current flow or by applying ~ alternating voltage to tlle plal;es and measuri.ng the capacitance. In yet a fur-ther ~orm o* t:ransducer may be us~3cl in the presen-t lnvention pressure may be applied to a body constitu-ted b.y carbon granules simi.lar to -t:he body present in -the conven-tional carbon microphone, and thus the res:is,i,ance o:~ the body o* carbon granules will a.lter in respoIIse to applied presswre. 1'he resistance of` the bod-y of carbon grc~lwles may be measured electrolJ.i.c~ll.].yg a.gaill by apply:Lllg a ~roltage and observi.ng or - ,~j :I J? .......................... !

" ' , ' ,'; ~ '~ , . ' ' , .

LZ86~L2 ` measuring t]Ze r~ul-tant current 1 l ow.
In any e~en-i, the rifle :is provided witll the above described plurality of pressure sensitive tr,lllsducers and the t:ransduccrs are connected, for example by mei~ns of a lead 1.50 to a compara-tor 15.1. and thus to a computer l52.
The comparator 15l is provi.ded wi.-th an appropri.ate memory or means providing reference signals, and the signals representative of the pressures applied to the various transducers 011 the rifle are compared with si.gnals representative of predetermined pressures which are deemed to be the correct preisures. S:ignals are t]lUS produced which indicate whether the pressure applied to any particular transducer is correct, i.s too great 9 or is too lit-tle. A display device 153 is provi.ded and portion of -the display device provides a dlsplay as illustrated in ~igure 31 ~vhich illustrates a sc:reen l54 of the display device 153. Shown on the screen l54 is a ~epresentation l55 o:f the rifle 14$ arld also the screen is provided with four illuminated indi.cating devices 15~6, 157 9 l55, 159, each display de~ice corresponding to one of -the transducers. In one mode of operal;:ion t.he display device 1~3 will cause tl3.e pressures appl.iecl to the transducers to be displa.yed instantanecusly, and t1~1.s a tra:inee marksman may grasp -the rifle and may a~just his grip and firi.ng position until such -time -th.at the . .
di~play con:firms that tbe correct pressure is being app:Lied to`ieach o:f the transducers. Thus, when the trainee marksman.
il1itially grasps the ri:fle it may be that too great a pressure is being ap~lied l:o two o-f the transducers, ancl too small a pressllre is being appl-;ed to the rcmain:ing -I~vo transducerc;. Th.~s the trail~ee ma.rksmal~ may ini.-tially release ..
_ 51G --- i !: :, : :: ~, .' . , ~ : . , :, ~ - . , : . .

the pressl.c l-pl~liecl-to tlle ~irst -two transd~cers until the correct pressure is indicatcd as bein~ applie~ ancl subsequen-tly -the trainee l~arl~sm.ln may increase -the pressure app]ied to ttLe relllaini.ng two -trangclucer~ unt:il agai:n thc S display ind:;cates that the corr~ct pressure :is being applied. Thus the trainee marksman may get the feel of the correct :E:irlllg position and th.e correct appli.ed pressures.
In a second mode of operat:ion o~ the device no pressures are indicated oll the display device until the trigger is .~0 pullecl and the round is ~ired and then the display will indicate the pressures applied to the various pressure transducers at tlle ins-tant o~ ~irlng o~ the ri:~le. The displ~y will be maintained on the display device ~or a predetermined period of time and then the display wlll be L5 erased to permit he trainee marksman -to proceed to ~ire anol;her round.
Whils-t there are many ways i.n which the display could indicate the application o~ the correct pressure or the incorrect pres~ure, iYl one embodimen-t the display is providecl with the devices ].56-159 ~or illuminating parts of the rep.Lrcsentation o~ the rif`le corresponding to the par-ts o~
the riflQ prov;.cled wi.th -the pressure transducers with light of` di~erent colours, Thus th.e portions ].56-159 the ri~le may be il].uminated with the red light i~ the pressure applied to the ri~le is too great~ green li~ht :L~ I;he pressure is correct ~nd with -the yellow light i~ -the pressure -is insuf:Eicient.
7~1ilst the dev:ices 156-159 may each merely comprise three bulbs oI` di~eren-t colour moun-ted behirld a single lens or tran~P.~rent WinClOW 1J1 .a display it is to be appreclated t,hat 3~ the displcay ~lay be prov-:i.ded or. a colour cathode ray tube ~ 51~I ~

,, , . ,~ . , ~ ' anc] in suc]-l a case -l;ho colour oP the rer)r:esentat:i.on oP any partlc~lar .~rec.lln-ly g,ra.dua].].~ l~e modulatod :in respollse to ~M :incre~se ln pro~sswre ~ppl:i~d -to the tr~nsclucers.
It is preferred that a sensor i.s provided orl the trigger adapted to sense whell t:he markslrJcln tak.es the Pirst pressure on the trigger and this sensor :is connected to a -timing device to onsul-e that the trainee marksman maintains first pressure Por an adequate period oP time. IP the trainee ma.rlcsman snatches the -trigger without holdlng the :L0 Pirst pressure for a sufPicient period oP time, a lamp 160 may bo illwili.nated on the di,splay.
3l ~igure-~4-also i],lustrates a Pibre optic bundle 161 which is colmected -to 1;he rear sight 162 oP the rifle 145. The Pibre op-tic b~ndle is connected to the rear sight L5 oP the weapon is such a way that ~hils-t the trainee marksman may still see over the rear ~;,ight towards the target, an image corresponding to the image viewed by -the trainee ma.rlcsman is ~ithcdra~l through the fibre optic bundle 161.
The Pibre optic bundle 161 is collnec-ted to a vidicon tube 20 . ~` or o-ther image recording device 1,62 as .illustrated schematically in l~igure 33, ancl the output o:E` t,he image recorcling dovice :is :E`ecl to -the computer 152 where the ,image may be rec~rded or ~storecl. TI1Q image may also be supplied to a disp't.ay dbv:ice 163 provided Por -the range con-troller, although the ,~5 di~splay device 163 may be provided adjacent the trainee marksman. ~t will be appreciated tha-t tlhe person -trai,ning a trainee ma.rksm~m wi,.l be able to observe precisely the same image as that observed by t.he trai:nee marksman when Pi,ri,Mg the woapon, and the vi,clicoM or tube or other device i.62 may 't~e a-.lapted to recorcl o.r~.ly th.e :ima.ge vi~wed 'hy the ~ 51~ -~, ` , i ~ . ' ' ' ' ' ~2~3642 trainee marksman at the instant of firing or to record the image vi~wed by the trainee marksman all the time.
Since breathing is an important part of accurate shooting it is preferred to provide the trainee marksman with means for monitoring his breathing. It is envisaged that such means may comprise a belt 164 tightly worn by the trainee marksman, the belt incorporating strain gauges or the like. As the marksman breathes in, so the strain gauges may be placed under tension, and thus the breathing of the trainee marksman can be monitored. Preferably, the belt is also provided with transducers or the like adapted to detect the pulse of the trainee marksman, so that the pulse rate of the trainee marksman can again be monitored. Signals gene-rated by the strain gauges and the transducers are supplied, through a lead 164', to the comparator 151 and thus to the computer 152. The information may be stored or recorded by the computer 152.
Figure 32 illustrates a marksman utilizing a rifle 145 as illustrated in Figuxe 30 and wearing the belt 1~4, and it can be seen that the marksman is firing at a target and is provided with a display device which provides a rep-resentation of the target indicating where bullets fired at the target actually impinge upon the target, the display device also providing a representation of the rifle providing an indication of the pressures applied to the various partæ
of the rifle by the trainee marksman.
Whilst one particular rifle in accordance with the present invention has been described it is to be noted that the means for recording an image corresponding with the image viewed by the trainee marksman may comprise any appropriate , . , ~ :

: . ~ . , .
-,. ~

means, alld ~ cor~)orate tlle llse o:f` a semi-silverecl nlirror or other such dcvice. Wl~ l.st the invention has been clescribecl wil,ll re-L`erence I;o an embodiment in whi.ch transducers a:re mountecl o:n a ri:~:l.e, -the transducers may be~ moun-ted ;n gloves worn by a marksman utilising ~lle rifle.
3 L~ 3.5 Figures ~ an~ ~ are flow char-ts Or the two computing processes described above, with reference to ~igures 4 and 15.

It ~lill be understood that -those skilled in the art can readily prepare ~rom these flow charts, and from the equations developed above, a speeial~purpose computing and controlling arrangemcn-t for carrying out the described sequenee of ~uncti.ons~ Those skilled in the art wi.ll furthcr recognize that one or more general~purpose computers may be rea~ily programmed to perform such ~unctions without resort to undue e~perimentation. For this reason~ more detai.led description o~ apparatus ~or ~ these p~rposes is not deemed necessary here7 It is to be nppreciated that in certain embGdinlents of the invention the transducers may need to be in a three dimensional array, rather than in a single plane.

In yet ano-ther embodiment of the invent:ion any errc~s causecl by de-acceleration of the projectile may be overcome by providi.ng the computer with in~ormation concerning the law of deceleration or other parameters n~fecting deceleration o~ the bul.le-t, the computer thus being able to calculate -the deceleration of` any part-;cular bullet ~n~ to correct ai~ errors caused by such decle:ration.

',. , ' ~.

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Claims (77)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for determining information concerning the trajectory of a supersonic projectile passing through a pre-determined area, said apparatus comprising at least three transducers located spaced adjacent an edge of the pre-deter-mined area, each said transducer comprising a member of rigid material having a convex surface exposed to an airborne shock wave generated by the supersonic projectile, and means for providing an output signal in response to the detection of such a shock wave by said member, the output signal providing means being connected to said rigid member such that the dis-tance of the path between any point on the convex surface and the said output signal providing means is constant so that the output signal is generated at a pre-determined time relative to the instant at which the airborne shock wave impinges upon the said convex surface, regardless of the location of the point on the convex surface that is impinged by the shock wave, there being means to measure the time delays between the output signals generated by each of the transducers, and means adapted to calculate, from said time delays, information con-cerning the trajectory of the projectile.

2. An apparatus according to claim 1 wherein the transducers are located adjacent the lower side edge of the predetermined area.

3. An apparatus according to claim 1 further comprising means for mounting said transducers so that said shock wave impinges directly on the transducers.

4. An apparatus according to claim 1 wherein each said trans-ducer comprises a disc-shaped element of a piezo-electric material.

5. An apparatus according to claim 4 wherein each said disc shaped element has a diameter of approximately 5 mm or less.

6. An apparatus according to claim 4 wherein said disc-shaped member has one face thereof secured to the base of said member having a convex surface.

7. An apparatus according to claim 6 wherein a portion of the base of the member with the convex surface protrudes from the rest of the base, the disc-shaped member being secured to said projecting portion.

8. An apparatus according to claim 7, wherein the convex surface of said member of rigid material is hemis-pherical.

9. An apparatus according to claim 5 wherein each said transducer further comprises a member constructed of a rigid electrically insulating material having a recess to accommodate said disc-shaped element, said element having conductive coatings on the two opposed faces thereof and conductive wires connected to said coatings.

10. An apparatus according to claim 9 wherein said member of rigid electrically insulating material is surrounded by a sleeve of an electrically conducting material to act as a Faraday Cage.

11. An apparatus according to claim 1 wherein each said transducer is mounted in a block of acoustic de-coupling material, said block being secured to a rigid structure for maintaining said transducer in a fixed position.

12. An apparatus according to claim 11 wherein said acoustic de-coupling material comprises closed cell poly-ethylene foam.

13. An apparatus according to claim 1 further comprising a support panel having apertures formed at predetermined locations, said transducers being dimensioned for snugly fitting engagement in said apertures, and said panel having means for absorbing shock waves, whereby only airborne shock waves may reach said transducers.

14. An apparatus according to claim 13 wherein said support panel comprises a sheet of metal having sound absorbing material secured to the faces thereof.

15. An apparatus according to claim 1 wherein the transducers are located at points in a three dimensional array so that the transducers are not in a single plane.

16. An apparatus according to claim 1 further comprising means for amplifying the signal produced by each transducer.

17. An apparatus according to Claim 16 wherein said amplifying means comprises means for receiving and initially amplifying said transducer signal and a threshold comparator which only passes signals from said initial amplifying means having a predetermined minimum value.

18. An apparatus according to Claim 17 further compri-sing linear amplifier means for amplifying the output of said threshold comparator.

19. An apparatus according to Claim 17 wherein the predetermined minimum value of said threshold comparator is adjustable.

20. An apparatus according to Claim 1 wherein at least four transducers are provided.

21. An apparatus according to Claim 1 wherein said transducers are arranged in a linear row.

22. An apparatus according to Claim 20 wherein at least five said transducers are provided and said transdu-cers are arranged in two staggered rows.

23. An apparatus according to Claim 1 wherein the pre-determined area is a target area and the information concer-ning the trajectory is the position of the trajectory rela-tive to the target area.

24. An apparatus according to Claim 23 wherein a tar-get is provided in the target area, and means for absorbing shock waves or sound is located between the target and the transducers.

25. An apparatus according to Claim 1 wherein a plurality of target areas are located adjacent one another, there being a single array of transducers situated general-ly beneath said plurality of target areas, said calculating means being adapted to select signals from the particular transducers which provide an output signal in response to detection of a shock wave generated by a supersonic pro-jectile fired at one of said target areas.

26. An apparatus according to Claim 25 wherein said array comprises a linear row of transducers.

27. An apparatus according to Claim 25 wherein said array comprises at least two staggered rows of transducers.

28. An apparatus according to Claim 1 further compri-sing means for storing temporarily information signals con-cerning the time of generation of a signal by each trans-ducer, and means for subsequently transferring said information signals to said calculating means.

29. An apparatus according to Claim 28 wherein said storing means comprises a plurality of counters, each said counter being started upon receipt of a signal from one said transducer and stopped upon receipt of a signal from another said transducer.

30. An apparatus according to Claim 28 further com-prising a clock signal generator for providing successive signals representative of successive instants of time, a latch coupled to each transducer for storing the time sig-nal provided by said clock signal generator at the instant that the latch receives a shock wave induced signal from the associated transducer, means for providing a signal identifying each said latch, means for transferring the time signal and identifying signal from each said latch to a buffer, and means for transferring signals from said buf-fer to said calculating means.

31. An apparatus according to Claim 28 wherein a plurality of groups of transducers are provided, each group being associated with one said storing means.

32. An apparatus according to Claim 31 wherein each said group of transducers is associated with one bank of said target areas.

33. An apparatus according to Claim 28 wherein said calculating means comprises means for selecting groups of said information signals likely to be derived from a single shock wave, and means for determining from each of said group of signals the position of passage of a projectile through said target area.

34. An apparatus according to Claim 33 wherein said calculating means comprises a pre-programmed general pur-pose computing device.

35. An apparatus according to Claim 28 further inclu-ding a visual display device.

36. An apparatus according to Claim 28 further compri-sing means for generating a display signal representative of said target area, means coupled for receiving said display signal and providing a visual display of said target area, and means coupled to said display signal generating means, said calculating means and said visual display means, for detecting when a portion of said display signal correspon-ding to the calculated position of said projectile is being displayed and for modifying said display signal at that in-stant, whereby a visual indication of the projectile posi-tion relative to said target area is provided.

37. An apparatus according to Claim 35, wherein said display signal generating means comprises a television camera, and wherein said display signal is modified by in-verting the display signal.

38. An apparatus according to Claim 37 further compri-sing means for determining the coordinates of the point of the visual image being scanned by the television camera at any instant and means for comparing these coordinates with the coordinates of the position of the projectile as deter-mined by said calculating means.

39. An apparatus according to Claim 28, further com-prising means coupled to the output of said calculating means producing a permanent record of the position of said projectile relative to said target area.

40. An apparatus according to Claim 39, wherein said record producing means comprises mean for printing said record.

41. An apparatus according to Claim 39, wherein said record producing means comprises means for punching paper to produce said record.

42. An apparatus according to Claim 1 wherein said transducers are located adjacent a lower edge of a target area and are concealed from the firing point by means which cannot be penetrated by said projectile.

43. An apparatus according to Claim 1 wherein a tar-get is provided in said predetermined area.

44. An apparatus according to Claim 43, further com-prising means for moving the target from a concealed position to a visible position and vice versa.

45. An apparatus according to Claim 43, further com-prising means for illuminating said target provided at said target area to permit shooting to be conducted after dark.

46. An apparatus according to Claim 43, further com-prising a trolley upon which said transducers and said target are mounted and which can move along a predetermined track to permit the position of said target to be adjusted.

47. An apparatus according to Claim 44, wherein means is provided for controlling and monitoring movements of said target.

48. An apparatus according to Claim 47, wherein a plus rality of targets are provided and wherein said controlling and monitoring means is provided with means for displaying the condition of each said target.

49. An apparatus according to Claim 44, further compri-sing radio control means for controlling movement of said target.

50. A transducer for detecting an airborne shock wave, said transducer comprising a dome member of substantially rigid material having a convex surface to be exposed to the shock wave, said dome member transmitting said shock wave to an element for providing an output signal in response to the shock wave, said element being connected to the base of the dome, the path from any point on the convex surface to said element through the material of the dome being constant, so that the output signal is generated at a pre-determined time relative to the instant at which the airborne shock wave impinges upon the said convex surface, regardless of the location of the point on the convex surface that is impinged by the shock wave.

51. A transducer according to claim 50 wherein said dome member is hemi-spherical.

52. A transducer according to claim 50, wherein said element adapted to provide said output signal comprises a disc shaped member of piezo-electric material, one planar face of which is connected to the base of said dome member.

53. A transducer according to claim 50 wherein said disc is bonded into a recess formed in a housing formed of insulating material, the base of said dome being provided with a pro-jection dimensioned to project into said recess and engage said disc of piezo-electric material.

54. A transducer according to claim 50, wherein opposed planar faces of said disc are coated with an electrically conductive material, and electrically conductive wires are connected to said coated faces.

55. An apparatus according to Claim 43 wherein signals from said transducers are conveyed to said calculating means via a radio link, and wherein control signals are conveyed to said trolley via a radio link.

56. An apparatus according to Claim 55 wherein a com-puter is provided adjusted to control and monitor movements of said targets.

57. An apparatus according to Claim 56 wherein a plu-rality of targets are provided and said computer is provided with means for displaying the condition of each said target.

58. An apparatus according to Claim 1 wherein means are provided for calculating the effect of wind speed, said means comprising a controllable source of sound waves of a frequency detectable by the transducers, and means to cal-culate the effect of wind speed from signals received by said transducers from said source of sound waves.

59. An apparatus according to Claim 1 wherein shiel-ding means are provided to shield the transducers so that the region of space from which the transducers may receive shock waves is bounded by a single plane.

60. An apparatus according to Claim 59 wherein the shielding means comprises a rigid linear member extending in front of and above the transducers.

61. An apparatus according to Claim 1 wherein two substantially ...

linear rows of transducers are provided, each row of transducers comprising at least three transducers, the two rows of transducers being arranged in substantially a common plane.

62. An apparatus according to claim 61 wherein the transducers are arranged in two linear rows, the transducers being substantially evenly spaced.

63. An apparatus according to claim 62 wherein the rows of transducers are parallel and the transducers in the rows are co-aligned with each other.

64. An apparatus according to claim 63 in which the plane containing the transducers is horizontal.

65. An apparatus according to claim 63 in which the plane containing the transducers is vertical.

66. An apparatus according to claim 61 in which each of the rows of transducers is provided with means shielding the transducers of that row so that the region of space from which the transducers of each row may receive a shock wave is bounded by a single plane.

67. An apparatus according to claim 1, including a weapon, means for detecting the pressure applied to pre-determined parts of the weapon by a person holding the weapon, and means for recording or displaying the pressure applied to the weapon.

68. An apparatus according to claim 67 wherein the weapon is a gun or rifle and the means for detecting the applied pressure comprise transducers or the like.

69. An apparatus according to claim 67 in combination with a visual display unit provided to display the pressure applied to the weapon comprising means to display a repre-sentation of weapon and means for causing parts of the representation to have colours representative of the pressure applied to the corresponding parts of the actual weapon.

70. An apparatus according to claim l, including a weapon for use in training personnel in the art of marksman-ship wherein said weapon is provided with means for generating an image representative of the image viewed by the marksman across the sights of the weapon, and means either for recording the generated image to enable the image to be redisplayed at a later time, and for enabling another person to view the generated image at a remote position.

71. An apparatus according to claim 70 wherein said means comprise a fibre optic device, one end of the fibre optic device being positioned or located to receive an image which is substantially identical to the image received by the marksman.

72. An apparatus according to claim 71 in which a semi-silvered mirror is provided within the sight, the fibre optic device being adapted to receive an image from the semi-silvered mirror.

73. An apparatus according to claim 70 in combination with a device adapted to record the image.

74. An apparatus according to claim 1, including a device for monitoring the breathing of a marksman, said device comprising a belt or the like adapted to be worn by the marksman and means for measuring the tension within the belt to ascertain the quantity of air within the lungs of the marksman.

75. An apparatus according to claim 74 wherein the means for determining the tension within the belt comprise a strain gauge or the like.

76. An apparatus according to claim 74 incorporating a transducer to detect the heart beats of a trainee marksman.

77. An apparatus according to claim 1, 2 or 3 wherein means are provided for supplying said calculating of a bullet, the calculating means being adapted to obviate any errors caused by such deceleration.