US2550482A - Sighting mechanism - Google Patents

Description

DEHIWH nuum April 1951 F. v. JOHNSON SIGHTING MECHANISM Filed Nov. 4, 1942 3 Sheets-Sheet l Inventor. FrithioF Johnson, y w

l-hs Attorneg.

3EARGH ROOM April 24, 1951 F. v. JOHNSON 2,550,482

SIGHTING MECHANISM Filed NOV. 4, 1942 3 Sheets-Sheet 2 Inventof FTi'thiO'F Johnson,

i5 Attorneg April 24, 1951 F. v. JOHNSON sxsmme MECHANISM 5 Sheets-Sheet 3 Filed Nov. 4, 1942 r m m 0 6 mcMZ M #5 J *M l a M O ..n w r n o w r a. w m Kw nh .w 1 FH I F s Patented Apr. 24, 1951 b'tillibnf fiuum SIGHTING MECHANISM Frithiof V. Johnson, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application November 4, 1942, Serial No. 464,453

6 Claims. (01. 3349) This invention relates to sighting mechanism, more particularly to sighting mechanism for use in the control of gunfire, and it has for its object the provision of improved mechanism of this character.

While it is applicable more generally in the control of gunfire, this invention is especially useful in the control of the fire of machine guns at rapidly moving targets, such as aircraft. And it relates in general to the type of sighting mechanism described and claimed in my copending application, Serial No. 459,780, filed September 26, 1942, Patent 2,467,831, granted April 19, 1949, and which is assigned to the same assignee as the present invention.

The sighting mechanism of that application controls the gun so as to give it the correct lead angle with relation to the line of sight to the target as required bythe speed of the target. The present invention likewise controls the gun to give it the correct lead as required by the speed of the target, but in addition it superimposes an elevation lead correction as required by the gun elevation and the range to the target. This correction I will refer to as superelevation.

In accordance with this invention, a sight is provided for establishing a line of sight to the target. The sight is mounted upon a support which is movable so that the line of sight may be brought to bear on the target and follow it. And the support itself is caused to move in a rigid system with the gun which is controlled.

Also mounted upon the-support is a gyrosco which is free to move about a predetermind point of suspension. The gyroscope is coupled to the support so that these members may be moved relatively to each other, but the coupling means is constructed and arranged to apply a torque to the gyroscope which is proportional to the magnitude of the displacement between the gyroscope and the support and which tends to precess the gyroscope to bring its spin axis into a predetermined position with reference to the support. When the support is moving in order to cause the line of sight to follow a target, the gyroscope will be displaced from this predetermined relative position by an amount dependent upon the sped of the target, and also upon the strength of the coupling means between the gyroscope and the support.

The coupling effect between the gyroscope and the support is controlled to give the gun the correct lead as is made necesary by the speed of the target, and this is accomplished by controlling the torque generated by the coupling means in accordance with the time of flight of the projectile from the gun to the target.

In addition, the sighting device of this invention includes means for changing the position of the gyroscope in elevation with reference to the support so as to introduce the correction for superelevation, referred to above.

In one form of this invention, the gyroscope is displaced in the vertical planewith reference to its support by an amount required by gun elevation and target range by the application of a torque to the gyroscope gimbal system. This torque is varied in accordance with a function of the angle of elevation of the gun.

Therefore, in keeping the line of sight on the target in elevation, the superelevation lead correction is automatically generated and applied to the gun.

For a more complete understanding of this invention, reference should be had to the accompanying drawings in which Fig. 1 is a side elevation, mainly in section, illustrating a sighting device embodying this invention; Fig. 2 is an end elevation of the sighting device of Fig. 1, the major portion of the figure being shown in section; Fig. 3 is an end elevation view of a part of the sighting device of Figs. 1 and 2 taken through the line 3-3 of Fig. land looking in the direction of the arrows, the figure being drawn to a larger scale than Figs. 1 and 2; Fig. 4 is a sectional view taken through the line 4-4 of Fig. 1 and looking in the direction of the arrows, the figure being drawn to a larger scale than Fig. 1; Fig. 5 is a perspective view of a portion of an optical system used in the sighting device of Figs. 1-4; Fig. 6 is a diagrammatic representation of certain control elements for the gyroscope elements of the sighting device; and an electrical power system therefor; Fig. 7 is an elevation view illustrating the relationship of the sighting device to a gun and how it is connected with the gun; Fig. 8 is adiagrammatic view of certain elements of the sighting mechanism illustrating the functioning of these elements; Fig. 9 is a diagrammatic representation of a field of battle; and Fig. 10 is a diagrammatic view illustrating a modification of a part of this sighting mechanism.

Referring to the drawings, this invention has been shown in one form in connection with a sighting device I 0 intended to be used in' the control of a machine gun H, and intended to determine for any firing problem the gun lead angle made necessary by the speed of the target.

and the superelevation, which is required by the gun tlevation and the range to the target. In the specific embodiment shown, the machine gun II is mounted for use from the ground against aircraft targets; and it is mounted so that it may be moved both in train and in elevation with reference to the support. As shown in Fig. 7, the gun is mounted upon a suitable turntable 42 mounted upon a fixed base l5; so that it may be moved in train about a VertiLal axis. Also, it has trunnions l4 about which it may be elevated on a horizontal axis.

The sighting device comprises a metallic casing l5 defining a chamber i6, and a casing section I! depending from the casing l5 and defining a chamber [8.

Mounted within the chamber I6 is a gimbal ring 19 rotatably supported by shafts 20 and 2!. Pivoted to the gimbal ring l9 to move about an axis at right angles to the suspension axis of the ring is a gyroscope 24; the ring is provided with shafts 25 which are received in bearings (not shown) mounted in the gyroscope. Mounted within the casing of the gyroscope is the gyroscope wheel shaft 21, which shaft is driven by any suitable high-speed motor (not shown), but which preferably will be a three-phase induction motor. The motor also is housed by the gyroscope casing. As will be understood, the axis of the shaft 21 constitutes the spin axis of the gyroscope.

The shaft 21, as shown, projects from the one end of the gyroscope casing, and On its projecting end it carries an eddy current disk 28. The eddy current disk comprises a plate-like disk 29 which is rigidly secured to the shaft 27 and which carries a second plate 30 having an outer curved surface approximately in the form of a segment of a sphere which has its center in the center of suspension of the gyroscope. Spun over the curved surface of this member is an electrically conducting sheet 3|, which preferably will be made of copper. Positioned opposite the eddy current disk 28 is a suitable electromagnetic device 32 fixedly mounted in the adjacent wall of the casing 15. The magnet 32 comprises a central pole 33 and an outer annular pole 34 between which is inserted the magnet energizing coil 35. The magnet 32 is mounted in the casing 15 so that the longitudinal axis of the center pole piece 33 passes through the center of suspension of the gyroscope; and the lengths and shapes of the pole pieces 33 and 34 are such that their ends lie on a spherical surface having a center at the center of suspension of the gyroscope.

The eddy current disk 28 and the magnet 32 constitute a coupling between the gyroscope and the casing I5 which applies a torque to the gyroscope which tends to precess it into alignment with the axis of the magnet. It will be understood that in the operation of the coupling, when the eddy current disk 28 is rotated in the magnetic field set up by the magnet, and the axis of the gyroscope is aligned with the axis of the magnet no eddy currents are induced in the disk. However, if the axis of the magnet departs from the axis of the disk, the motion of the disk under the magnetic poles causes eddy currents to flow in the copper sheet 3|. A resulting electromagnetic force acts on the gyroscope which tends to precess it into alignment with the magnets axis. The magnitude of this restoring force varies directly with the angle of departure between the gyroscope and the magnet, and with the coefficient of coupling which is a function of the magnet excitation current. This excitation of the magnet is controlled by means of a suitable rheostat 36 (Fig. 6) which is provided with a manually operable setting knob 31.

The operation of the coupling may better be understood by reference to Fig. 8. This is a diagrammatic view and is a plan of the gyroscope and magnet with an angular displacement AB between them. The eddy current disk 28 is assumed to spin clockwise viewed from the magnet, the portion of the disk at p, directly under the center pole of the magnet, is travelling upwardly perpendicular to the plane of the figure. The motion of this part of the disk in the field of the magnet causes eddy currents to be induced in the disk. These currents interacting with the field which produces them, causes a retarding force to act on the disk at the point p in a downward direction. This force constitutes a torque about the spin axis of the gyroscope and also about the horizontal axis 26-26. The torque about the spin axis tends to slow the spin axis, but such slowing is prevented by the electrical power supplied by the gyroscope motor. The torque about the axis 26--26 causes precession about a vertical axis, that is, precession in the plane of the figure, which tends to bring the gyroscope into correspondence with the magnet. The linear speed of the disk through the magnetic field increases as A5 increases, while the torque arm remains substantially constant, whereby the precession rate varies substantially directly with A13, and with the square of the magnetic field.

Therefore, it will be observed that the gyroscope will follow the motion of the magnet in the horizontal plane. In exactly the same way, the gyroscope will follow the motion of the magnet in elevation should the magnet be displaced in elevation with reference to the gyroscope.

The gyroscope is intended to control the line of sight of the sighting mechanism, and it is connected to a suitable optical system so that the line of sight remains parallel to the gyroscope axis.

The optical system controlled by the gyroscope is constructed and arranged to establish a collimated line of sight parallel to the axis of the gyroscope. This optical system is mounted within a tubular member 38 depending from the casing section l'l. It comprises a reticule 39 secured in a fixed position in the tube 38. The reticule 39 is formed of glass and has its upper side 39a silvered. In this silvered side is scribed a Cross 40 simulating cross hairs. Mounted in the tube 38 below the reticule 39 is a source of light 4|, shown as an incandescent lamp. The light passing through the cross 40 is focused by the collimating lens 42. And in passing through this lens all of the light rays from any single point on the reticule are made parallel. The collimated light next strikes an inclined glass 43 which is mounted in the chamber I8. This glass 43 is carried by a fork-like extension 44 of the gimbal ring [9 so that it rotates with the gyroscope about the axis of suspension of the ring I9. It is also connected with the gyroscope by an angle halving linkage 45, which is connected by a pin 45a with the gyroscope and a pin 45b with the glass 43, :0 as to rotate about an axis parallel to the axis of movement of the gyroscope in the gimbal ring l9 through one-half the angle made by the gyroscope; the distance frcm the axis 25-26 of the gyroscope to pin 45a is substantially one-half the distance from the axis of rotation of the mirror 43 in the extension 44 to the pin 45b so bti-itibi'i nuulw that the mirror moves on this axis through but one-half of the angle of movement of the gyroscope about axis 2926. Therefore light from the center of the reticule 39 striking the glass 43 is reflected parallel to the gyroscope axis. An observer looking into the reflecting glass will at all times see the center of the cross lines, and the center of the cross lines will move about in the field of view as the gyroscope moves about relative to its casing l5.

It will be observed that the two walls 46 and 41 of the casing 17 opposite the two inclined faces respectively of the glass 43 are formed of glass so that the observer may look directly through the chamber l8 and the transparent glass 43 to view the reticule image, and also to view the target. The observer will be stationed at the right-hand side of the chamber, as viewed in Fig. 1, his eye being indicated in this location.

It will be observed, therefore, that the optical system'generates a lighted reticule which may be viewed in the field of view of the target, and it will be further understood that in the operation of the s ght it is the purpose of the observer to bring the reticule image onto the target, and to keep it on the target.

The sighting mechanism is connected with the gun i I so that the central axis of the magnet 32 always remains parallel with the bore of the gun; that is, so that when the spin axis of the gyroscope is aligned with the axs of the magnet, the spin axis and the line of sight will be parallel to the bore of the gun. For this purpose, the sighting mechanism 19 is connected with the gun by means of a parallelogram linkage comprising a link 43 having one end rigidly connected with the gun trunnions so as to be swung with the gun, a link 49 which has one end pivoted to the link 48 and its other end pivoted to the casing 15, and further, rigid horn-like supports 50 pivotally secured to a fixed standard 5|. This standard 5| is secured to the gun turntable [2 by means of columns 52 so as to move with the gun in train. As the gun elevates to some position, indicated in dotted lines in Fig. '7, the link 58 turns with the gun about the axis of trunnions I4. The motion of the end of the link 48 is transmitted through link 49 to the sght casing which turns about the pivot at 5! to the dotted line position, as shown in. Fig. '7. In view of the connections between the sighting mechanism I0 and the gun. it will be understood that the central axis of the magnet 32 will be held in fixed parallel relation with the bore of the gun, and will move with it irrespective of the motion given the gun in-train and elevation.

The gyroscope 24 is also controlled by means of an unbalanced weight 53 which is mounted within the chamber Hi. This weight is mounted upon an arm 54 which in turn is secured to one side of a face gear 55. This face gear, as shown, is mounted to rotate in a bearing 56 which is supjorted upon a fixed bracket 5'! in the chamber IS. The face gear meshes with a pinion 5S fixed to the upper shaft 29 of the gimbal ring l9. The weight and face gear thus are pivoted to move on a horizontal axis which is parallel to the axis of the gun trunnions Id. The weight applies through the face gear and pinion 58 a torque to the gmbal I9 in such a direction as to cause the gyroscope to precsss in such a way as to depress the eddy current disk 29.

It will be observed that when the Inc of sight is horizontal, the effect of the moment of the weight on the ring l9 will be a maximum, and

when the line of sight is directly vertical the effect will be zero. This is as it should be, because if the target be in the horizontal plane of the sight, then for a given range the gun must be elevated to a higher angle than for any other position of the target to compensate for the effect of gravity in the trajectory of the projectile. The other extreme condition is when the target is directly above the sight; under these conditions, the gun will be directed straight at it, and superelevation will be zero-neglecting, of course, differences in the relative speed of the target and the sight.

On the end of the gyroscope opposite the eddy current disk 28 is a nutation damper. This damper comprises an annular weighted ring 59 which is pivoted on an inner flexible ring 60 by means of pivot pins 6! located in a diameter of the rings, as more clearly shown in Fig. 3. The ring 60 is pivoted to the gyroscope casing 24 by means of pins 62 to move on an axis passing through a diameter at right angles to the axis of movement of the ring 59. The pins 6] and 62 are in the form of screws and they are adjusted so that a predetermined resistance to motion is set up between the two rings and between the inner ring and the casing. Nutational motions of the gyroscope produce relative motions between the two rings and between the inner ring and casing. The frictional forces so produced cause the nutation to be damped. Stops 63 are provided to engage the weighted ring 59 to limit its movement, the stops providing some impact damping.

The nutation damper just described is not a part of this invention, but is that of Charles S. Grimshaw, and it is described and claimed in this copending application, Serial No. 487,309, filed May 7, 1943, Patent 2,412,453 granted D..- cember 10, 194.6, and which application is assigned to the same assignee as this invention.

Also, the gyroscope is provided with a suitable caging device 64 provided with a control knob 65 for caging and releasing the gyroscope.

The electrical diagram for the sighting mechanism is illustrated diagrammatically in Fig. 6. Electrical power for the system is supplied from a battery 66. A dynamotor 61 functions to convert the direct currentof the battery to three phase alternating current for the three phase induction motor of the gyroscope 24. The gyroscope motor is started by closing a switch 68. The lamp M is connected to the direct current source 66 and is controlled by means of a switch 69, and its intensity is controlled by an adjustable resistance 10. The magnet 32 and its controlling resistance 36, as shown, are connected to the battery 66 through switch 68.

In the operation of the sighting mechanism, it will be assumed that the gyroscope is rotating to rotate the eddy current disk 28 and that the magnet 32 is energized. Also, it will be assumed that the lamp 4! is energized. The observer will view the target through the transparent windows 46' and 41, and the transparent reflecting glass 43. Also, the observer will view the image of the reticule 39 in the field of view of the target. The gun I I is moved in train and in elevation to move the casing l5 so as to bring the image of the reticule onto the target and to cause the image to remain on and follow the target as the target moves in space.

When the casing I5 is thus moved with the gun, the axis of the gyroscope will lag behind the casing by an amount which is dependent upon the speed of the casing, and the coupling coeflicient between the gyroscope and the casing, that is, between the eddy current disk 28 and the magnet 32. The speed of the casing l5, of course, measures the angular velocity of the target, and the coupling coefficient is adjusted by the resistance 36 in accordance with the time of flight of the projectile from the gun to the target so that the lag in the position of the gyroscope axis behind the support is the correct lead angle for the gum-neglecting for the moment the effect of the weight 53 on the gyroscope that is, it is the correct lead for the gun, as required by the speed ofthe target; the rheostat 36 is graduated in terms of range, and preferably a range scale, graduated in hundreds of yards, will be provided to assist the observer in setting the time of flight knob 3'! of the rheostat.

The displacement of the gyroscope with reference to its casing I5 is imparted to the line of sight because of the motion imparted to the glass 43 by the gyroscope. Therefore, in order to keep the reticule image on the target, the position of the gun II, which is fixed to the casing l5, necessarily will have to be advanced with reference to the line of sight by an angle equal to the angle of lag of the gyroscope behind the casing l5, and this angular advance of the gun will be its correct lead, as required by the speed of the target.

The unbalanced weight 53 functions to generate superelevation, which as pointed out previously, is the correction to be applied to the gun in elevation which is required by the range of the target and its position in the elevation plane. This weight, as previously pointed out, functions to depress the gyroscope with reference to the magnet, and thereby in bringing the reticule image back on the target the observer will necessarily generate superelevation and apply it to the gun.

The operation of the sighting mechanism may be better understood by reference to Fig. 9. Here the target is following an inclined course ABC. The gunner moves his gun II in such a manner as to keep the line of sight established by the illuminated reticule on the target. The spin axis of the gyroscope 24 will also be directed toward the target because, as has been described, the

optical system is arranged to make the line of sight parallel to the gyroscope axis.

The line of sight is shown making an angle [3 with a fixed base line 0A in the plane of target travel OAC. AB is the lead angle made necessary by the velocity of the target along ABC, and a is the superelevation angle. The elevation of the gun is denoted eg. The pivot axis 202| of the gyroscope gimbal l9 lies in vertical plane OED, and is inclined at an angle so from the vertical. The magnet axis lies along the bore of the gun.

The lead angle AB can be found with good accuracy from the expression B AB T dt where T is time of flight of the projectile corresponding to present range, and

is the angular velocity of the target.

It can also be shown that the superelevation correction is closely represented by o'=KT cos eg 8 where K is a constant depending on the ballistics of the projectile. That is, a" varies with the cosine of the elevation of the gun and is nearly a linear function of the time of flight corresponding to the present range of the target.

Torques from two sources act to precess the gyroscope in following the target. The first of these arises in the eddy current coupling device. The eddy current disk 28 is shown turning counter-clockwise as viewed from the magnet. The portion of the disk directly under the center pole at the magnet is traveling in a direction perpendicular to plane OBD. The eddy currents induced in the disk by its motion in the magnetic field interact with the field to produce a retarding force, shown as F, which is also directed perpendicular to plane OBD; but in a direction opposite the motion. This force constitutes a torque about the spin axis of the gyroscope and also about axis qq, in plane GED, and passing through the axis of suspension of the gyroscope. The torque about the spin axis tends to slow the spin of the gyroscope, but such slowing is prevented by the electrical power supplied to the motor. The torque about axis qq is shown as vector Q, the direction of which indicates the axis about which the torque acts, and the length of which indicates the magnitude of the torque. The speed with which the disk passes under the magnet depends on the magnitude of angle DOB, so that force F increases as angle DOB increases. Since the moment arm of F about axis qq remains essentially constant, the torque Q also increases as angle DOB increases. By properly prc-portioning the thickness of the conducting sheet 3| on the eddy current disk 28, the torque Q is made to vary directly with angle DOB. Torque Q also varies with the square of the flux density under the magnet, and this is controlled by the rheostat 3B which is set in accordance with present range to the target. The torque Q is therefore Q=C (angle DOB) (square of flux density) where C is a constant depending on the design of the sight.

The second source of torque acting on the gyroscope is the superelevation weight. This, through the combination of face gear 55 and pinion 58 applies a torque R to the gyroscope about the pivot axis of the gyroscope gimbal, which axis is perpendicular to the gun bore and lies in a vertical plane OED. The magnitude of R varies with the cosine of the elevation angle eg of the gun. This will be seen from the fact that when the gun bore is horizontal, the weight projects horizontally and exerts its maximum torque on the gimbal, whereas when the gun bore is vertical the weight is pointed upward and exerts no torque on the gimbal. The torque applied by the weight may thus be expressed as R=M cos eg where M is a constant depending on the weight and the gear ratio at the face gear and pinion combination.

It is well known that under the action of a torque such as Q, the gyroscope will precess in such a direction as to tend to align itself with the torque; and further that if two torques such as Q and R act simultaneously the rate at which the gyroscope moves can be found by vectorial addition of the rates due to the torques separately. Since the gyroscope precesses in plane OBC to follow the target it is evident that the resultant of torques Q and R must lie in plane 0130. In other words, the superelevation torque R tends C (angle DOB) (square of fiux density) Angular momentum of spin The scale of rheostat 36 is calibrated to make the magnet flux such that Angular momentum of spin T when range R is set on the scale. angular rate produced by torque Q is Angle DOB T This may be resolved into two components of velocity,

Then the AB p 77 in plane OBC and T in plane OCD But the velocity of the gyroscope in plane CEO is whence @4 dt T B AB- T This is the desired solution for the lead angle. As has previously been described, the rate in plane GOD is exactly equal to and opposite that produced by the superelevation weight,

which is M cos eg Angular momentum of spin Thus a M cos eg T angular momentum of spin u'=T cos e g angular momentum of spin However, the desired value is a'=K T cos 69 which is obtained if the moment of the superelevation weight is made M ,=K (angular momentum of spin) =constant From examination of the above analysis it will be seen that in order to cause the gyroscope and the line of sight to move with the target, the gunner must lead the target by an angle which depends directly on angular velocity. Furthermore, the longer the range set on the rheostat 36 the weaker is the flux of the magnet and the greater must be the lead angle toproduce a given angular velocity. The additional effect of the superelevation weight causes the gyroscope to tend to precess downward from the target; and the operatorin order to compensate for the down= ward precession will elevate the gun, and hence the magnet, until the additional upward rate which it produces compensates for the downward rate due to the superelevation weight. Further it will be seen that the longer the range and the weaker the magnet flux, the greater must be the upward displacement of the gun to effect this compensation, and the greater will be the superelevation produced.

Small variations from the desired result M cos so will occur when the'gimbal ring l9 rotates about its axis TT. The result of this is to cause the weight 53 to rise or drop through-a small angle. The error resulting from this rise or fall may be made quite small by making the ratio between the large gear 55 and the small gear 58 quite large.

If it be desired to increase the accuracy of the mechanism, the moment rM may be varied by using a sliding weight, as shown more clearly in Fig. 10. Here, the sliding weight H is mounted upon an arm 12 projecting from the large gear 13 which corresponds to the gear 55. This gear 13 is geared to a gimbal ring 14 corresponding to the gimbal ring [9 through a gear 15 corre sponding to the gear 58. The weight II is positioned by means of a cord 16 and a spring TI. The cord is wrapped over a cam 18, the position of which is adjusted inaccordance with a function of advance range Ba and present range R. That is, the moment M of the above-mentioned equation:

must be equal to the superelevation function for the advance range of the target, as determined from suitable range stages (which range is the targets range at the instant of impact with the projectile) times angular momentum of spin and divided by the time of flight T of the projectile for present target range.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. Gun sighting mechanism comprising means for establishing a line of sight, a gyroscope connected to said means so that the direction of said line of sight is always in fixed relation to the direction of the spin axis of the gyroscope, said gyroscope controlling the direction of said line of sight in accordance with the position thereof, means mounting said line of sight establishing means and said gyroscope movable with the gun as it is moved in space in order to cause said line of sight to follow a target, means on said movable means for applying to said gyroscope a precessing torque to cause it to tend to follow said last-named means as it is moved to cause said line of sight to follow the target and for controlling said torque so that the position of said gyroscope with reference to said last-named means measures the lead angle of the gun required by the speed of the target, and additional means connected to said gyroscope for applying to it a precessing torque in accordance with the range of the target and elevation of the gun to displace the gyroscope spin axis with reference to said last-named means so that a correction in elevation is applied to said gun.

2. Sighting mechanism for a gun comprising sighting means for establishing a line of sight, a gyroscope, means connecting saidgyroscope to 11 said sighting means so that the gyroscope spin axis and said line of sight are always in parallel- 1 ism and so that the gyroscope controls the direction of said line of sight, a mount for said sighting means and gyroscope movable in train and elevation in order to cause said line of sight to 7 follow a target, said gyroscope controlling the di- 1 rection of 'said line of sight in accordance with its Y position relative to said mount, coupling means between said mount and gyroscope applying a torque to said gyroscope in order to cause it to precess to tend to follow said mount as the mount moves in keeping said line of sight on the target, means controlling the coupling effect of said coupling means in accordance with the range of the target, and additional means connected to said gyroscope for applying a torque to it to cause its spin axis to be displaced in a vertical plane with reference to said mount by an amount which is a function of the range of the target.

3. Sighting mechanism for a gun comprising sighting means for establishing a line of sight, a

gyroscope, means connecting said gyroscope to said sighting means so that the gyroscope spin axis and said line of sight are always in parallelism and so that the gyroscope controls the direction of said line of sight, a mount for said sighting means and gyroscope movable in train and "elevation in order to cause said line of sight to follow a target, said gyroscope controlling the direction of said line of sight in accordance with its position relative to said mount, coupling means between said mount and gyroscope applying a torque to said gyroscope in order to cause it to precess to tend to follow said mount as the mount moves in keeping said line of sight on the target, means controlling the coupling effect of said coupling means in accordance with the range of the target, and an unbalanced weight connected to the gyroscope so as to apply a torque to it to cause it to precess its spin axis vertically with reference to said mount by an amount which is a function of the elevation of said gun and mount, and to the range of said target.

4. Sighting mechanism for a gun comprising sighting means for establishing a line of sight, a gyroscope, having gimbal ring support means, means connecting said gyroscope to said sighting means so that the gyroscopes spin axis and said line of sight are always in parallelism and so that the gyroscope controls the direction of said line of sight, a mount for said sighting means and gimbal rin support means movable in train and elevation in order to cause said line of sight to follow a target, said gyroscope controlling the direction of said line of sight in accordance with its position relative to said mount, coupling means between said mount and gyroscope applying a torque to said gyroscope in order to cause it to precess to tend to follow said mount as the mount moves in keeping said line of sight on the target, means controlling the coupling eilect of said coupling means in accordance with the time of flight of the projectile to the target, and an unbalanced weight connected to a predetermined 65 one of the gimbal axes of said gimbal ring support means for applying a torque to the gyroscope to displace its spin axis in the vertical direction with reference to said mount by an amount which is a function both of the angle of elevation of the gun and the time of flight of said projectile.

5. Sighting mechanism for a gun comprising a sight for establishing a line of sight to a target, a support for said sight, a gimbal ring on said support mounted for rotation on a nominally and generally vertical axis, a gyroscope in said ring mounted for movement on an axis at right angles to said vertical axis and with its spin axis generally horizontal, connection means between said gyroscope and sight so that the direction of said line of sight is always in parallelism with the spin axis of said gyroscope and is controlled in accordance with the position of said gyroscope with reference to said support, said support being movable in train and elevation so as to keep the line of sight on a target, an electromagnetic coupling between said support and said gyroscope for applying to said gyroscope a precessing torque to cause it to tend to align itself in a predetermined position with reference to said support, means controlling the magnetic coupling effect of said coupling in accordance with the time of flight of a projectile to said target, and an unbalanced weight connected to said gimbal ring to apply thereto a torque about its axis of movement which torque is a function of the position of said support in elevation and also of the time of flight of said projectile.

6. Sighting mechanism for a gun comprising sighting means for establishing a line of sight, a gyroscope, means connecting said gyroscope to said sighting means so that the spin axis of the gyroscope and said line of sight are always in parallelism and so that the gyroscope controls the direction of said line of sight, a mount for said sighting means and gyroscope movable in train and elevation in order to cause said line of sight to follow a target, said gyroscope controlling the direction of said line of sight in accordance with its position relative to said mount, connection means between said mount and gyroscope for causing a displacement between said gyroscope and said mount which is a function of the angular velocity of said mount and the range of said target, and additional means connected to said gyroscope to displace it with reference to said mount by an amount which is a function both of the angle of elevation of said mount and of the range of said target.

FRITHIOF V. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,936,442 Willard Nov. 21, 1933 FOREIGN PATENTS Number Country Date 616,248 Germany Aug. 1, 1935 Certificate of Correction Patent No. 2,550,482 April 24, 1951 FRITHIOF V. JOHNSON It is hereby certified that erg-or appears in the rinted specification of the above numbered patent requirmg correction as f0 ows:

Qolumn 6, line 65, for 46' read 46; column 9, lines 83 and 84, for the equatxon read gand that the said Letters Patent should be read as corrected above, so that tha same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 21st day of August, A. 11 1951.

THOMAS F. MURPHY,

Assistant Oommz'asiam of Fannie.

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