WO1996012690A9

WO1996012690A9 - Isolation member with improved static discharge barrier and non-electric detonator cap including the same

Info

Publication number: WO1996012690A9
Application number: PCT/US1995/013093
Authority: WO
Filing date: 1995-10-13
Publication date: 1996-09-26

Abstract

An isolation member (34) for use in a non-electric detonator cap (10) is of substantially cylindrical shape and has an interior passageway (40) extending therethrough and defining a positioning region (44) and a discharge port (56). The positioning region (44) is dimensioned and configured to snugly receive and seat therein a signal transmission line or shock tube (30) and to orient the signal-emitting end (30a) thereof to aim along the longitudinal axis of cap (10) through a rupturable diaphragm (42) at the target provided by receptor charge (14). The isolation member is positioned between and spaces the signal-emitting end (30a) of the signal transmission line (30) from the receptor charge (14) contained in the detonator cap (10). The diaphragm (42) is formed with centrally intersecting score lines (42a, 42b) that facilitate rupturing of the diaphragm by the signal. The diaphragm (42) may have a circular or polygonal, e.g., rectangular, periphery. The isolation member is preferably made of a semi-conductive material to bleed off to the shell (12) any static electricity charges transmitted through the signal transmission line (shock tube 30) so as to prevent static discharge initiation of the charge.

Description

ISOLATION MEMBER WITH IMPROVED STATIC DISCHARGE BARRIER AND NON-ELECTRIC DETONATOR CAP INCLUDING THE SAME

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention concerns an improved isolation mem¬ ber for use in a non-electric detonator cap and an im¬ proved detonator cap including the same. More particular- ly, the present invention concerns an improved isolation member for use in the cap to retard the discharge of stat¬ ic electricity from an initiation signal transmission line through the detonator cap charge.

Related Art

The use of isolation members in non-electric detonat¬ or caps which are to be assembled to fuses capable of transmitting a static electric charge is known in the art, as shown by U.S. Patent 3,981,240 issued September 21, 1976 to E.L. Gladden. That Patent discloses the use of signal transmission lines, i.e., fuses, of the type dis¬ closed in U.S. Patent 3,590,739 issued July 6, 1971 to P.A. Persson. Such fuses, commonly referred to as "shock tubes", typically comprise an elongated hollow tube made of one or more synthetic organic polymeric material(s)

(plastics) containing on the interior wall thereof a coat¬ ing of reactive material such as a pulverulent high explo¬ sive and reducing agent, for example, PETN or HMX and alu¬ minum powder. The coating of reactive material on the interior wall is quite thin and leaves the tube hollow, providing an open channel or bore extending the length of the tube. When the reactive material is ignited, as by a spark igniter or a detonator cap used as a signal trans¬ mitter, or any other suitable means, ignition of the reac- tive material propagates an initiation signal through the bore of the tube. If the tube is properly connected to a receptor detonator cap, the initiation signal will initi¬ ate detonation of the cap. (As used herein, the "recep- tor" detonator cap is the cap which is to be detonated by the initiation signal transmitted through the tube or other signal transmission line. )

Other patents concerning such shock tubes and the manufacture thereof include U.S. Patent 4,328,753, issued May 11, 1982 to L. Kristensen et al and U.S. Patent 4,607,573 issued August 26, 1986 to G.R. Thureson et al. As disclosed in the Thureson et al Patent, the reactive material may comprise a thin coating or dusting of a mix- ture of an explosive such as PETN, RDX, HMX or the like, and a fine aluminum powder, and the shock tube may be a plural-layer tube. For example, as disclosed in the Kristensen et al Patent, the inner tube may comprise a plastic, such as a SURLYN"* ionomer, to which the reactive powder will adhere and the outer tube may be made of a me¬ chanically tougher material such as low or medium density polyethylene. (SURLYN is a trademark of E.I. DuPont de Nemours & Co. for its ionomer resins.)

U.S. Patent 4,757,764, issued July 19, 1988 to G.R. Thureson et al, discloses signal transmission lines com¬ prising tubes as described above except that instead of an explosive powder of high brisance (e.g., PETN or HMX), the reactive material is a low velocity deflagrating material. Use of a deflagrating material provides a reduced speed of transmission of the initiation signal propagated through the tube as compared to shock tubes. Such deflagrating material tubes are referred to as low velocity signal transmission lines ("LVST* lines"). Numerous deflagrating materials are disclosed in U.S. Patent 4,757,764, includ- ing manganese/potassium perchlorate, silicon/red lead, and zirconium/ferric oxide, to name but a few of the many dis¬ closed in that Patent starting at column 3, line 48. As pointed out at column 4, line 47 et seq. of that Patent, LVST* lines transmit an initiation signal by means of a "pressure/flame front" principle whereas shock tubes, when ignited, produce a "shock wave initiation signal" which travels through the tube. Both types of tubes, shock tubes and LVST* lines, as well as detonating cords, espe- cially low-energy detonating cords, may be utilized to initiate detonator caps for use in demolition, mining and other systems. Such tubes and cords are collectively re¬ ferred to herein and in the claims as "signal transmission lines".

Signal transmission lines of the type comprising a tube containing a metallic powder such as aluminum as part of the reactive material are capable of transmitting a static electric charge which may result in premature deto- nation of the receptor detonator cap, which can of course have catastrophic results. Accordingly, the invention of the above-mentioned Gladden Patent 3,981,240 provides a fuse-retaining bushing (28) made of a semi-conductive plastic material. The bushing provides a "stand-off", i.e., a space, between the signal-emitting end of the ini¬ tiating fuse (26) and the target of the initiation signal which, in the illustrated case, is a primer or booster charge (20). The bushing isolates the signal-emitting end of the signal transmission line from the target by a thin, flat rupturable membrane (40). The bushing further pro¬ vides a shunt path for transmitting static electric charges from the signal-emitting end of the initiating fuse to the metallic shell or casing (12) of the detonator cap, thereby bleeding off static charges before they reach a potential high enough to cause a spark which could pene¬ trate the membrane and ignite the cap charge to premature¬ ly detonate the cap.

The prior art also includes isolation bushings simi¬ lar to those shown in U.S. 3,981,240 but comprising a rup- turable diaphragm having four radial rupture grooves that emanate from the periphery of the diaphragm but do not in¬ tersect; instead, they terminate independently at non-cen¬ tral points on the diaphragm.

SUMMARY OF THE INVENTION

The present invention provides an isolation member for positioning the signal-emitting end of a non-electric signal transmission line within the shell of a detonator cap. The isolation member comprises a substantially cyl¬ indrical body dimensioned and configured to be received within the shell of the detonator cap. The body has an input end, an output end and an interior passageway ex- tending through the body to allow an initiation signal to be transmitted therethrough from the input end to the out¬ put end of the body. The interior passageway defines a positioning region at the input end of the body and a dis¬ charge port at the outlet end of the body. There is a signal-rupturable diaphragm that has a periphery and that is disposed within the interior passageway to isolate the positioning region from the discharge port. The diaphragm is connected to the interior passageway at its periphery and it has a plurality of intersecting score lines formed therein to facilitate rupture of the diaphragm without de¬ tachment of the diaphragm or portions thereof from the body.

According to one aspect of the invention, the dia¬ phragm may have a generally circular periphery and the score lines may intersect at approximately the geometric center of the diaphragm.

According to another aspect of the invention, the po¬ sitioning region may comprise a shoulder formed in the in¬ terior passageway and the diaphragm may be attached at its periphery to the shoulder.

Optionally, the diaphragm may have a pair of score lines which extend diametrically across the diaphragm and which intersect at a right angle with each other. Alter¬ natively, the diaphragm may have three radial score lines that intersect at about the center of the diaphragm.

According to still another aspect of the invention, the diaphragm may have a periphery which is generally po¬ lygonal in configuration with apices defined at the inter¬ section of adjacent straight-line segments of the periph- ery. In such case, it is preferred that the score lines emanate from the apices of the periphery of the diaphragm. Yet another aspect of the invention provides that the body may be substantially entirely comprised of a semi- conductive synthetic organic polymeric material.

The present invention also provides a detonator cap for connection to a length of non-electric signal trans¬ mission line having any one of a selected range of outside diameters and terminating in a signal-emitting end. The cap comprises an elongated shell having an open end for receiving the non-electric signal transmission line and an opposite, closed end. A retainer bushing is positioned in the open end of the shell and has a bore extending there- through for receiving therein a segment of the length of signal transmission line to connect the line to the elon¬ gated shell with its signal-emitting end enclosed within the shell. There is a receptor charge positioned within the elongated shell and disposed between the bushing and the closed end of the shell and axially spaced from the bushing. Finally, the cap includes an isolation member, as described above, disposed within the shell in the space between the bushing and the receptor charge.

Optionally, the cap may include a length of signal transmission line connected to the shell and may extend through the bore of the bushing with its signal-emitting end seated in the positioning region.

Other aspects of the present invention are set forth in the following description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view, with parts broken away, of a detonator cap having incorporated therein an isolation member in accordance with one embodiment of the present invention;

Figures 1A and IB are cross-sectional views, enlarged with respect to Figure 1, taken along, respectively, lines A-A and B-B of Figure 1;

Figure 1C is an enlarged view of the portion of Fig- ure 1 containing the isolation member;

Figure ID is a reduced-size (relative to Figure 1) view of another embodiment of a detonator cap generally corresponding to that of Figure 1, except that the upper part of the drawing is broken away;

Figure 2 is a perspective view of the isolation mem¬ ber of Figure 1;

Figure 2A is an end view of output end 38 of the iso- lation member of Figure 2;

Figure 2B is an end view of input end 36 of the iso¬ lation member of Figure 2;

Figure 2C is a cross-sectional view, enlarged with respect to Figure 2B, taken along line C-C of Figure 2B; and

Figure 2D is a view similar to Figure 2A but enlarged with respect thereto, of another embodiment of an isola¬ tion member according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

AND PREFERRED EMBODIMENTS THEREOF

Referring now to Figure 1, an embodiment of a recep¬ tor detonator cap in accordance with the present invention is generally indicated at 10 and comprises a tubular cas- ing or shell 12 made of a suitable plastic or metal, such as a semi-conductive plastic material or, as in the illu¬ strated embodiment, aluminum. Shell 12 has a closed end 12a and an opposite, open end 12b. A signal transmission line comprises, in the illustrated embodiment, a shock tube 30 having a signal-emitting end 30a which is con¬ nected to shell 12 as more fully described below. A re¬ ceptor charge generally indicated at 14 is enclosed within shell 12 and is comprised of, in the illustrated embodi¬ ment, a sealer element 16, a delay element 20, a primary explosive charge 22, e.g., lead azide or DDNP (diazodini- trophenol), and a secondary explosive charge 24, e.g., PETN. As those skilled in the art will appreciate, recep¬ tor charge 14 may include more or fewer elements than those illustrated in Figure 1. Thus, sealer element 16 and delay element 20 may be eliminated so that receptor charge 14 may comprise only one or more explosive charges, such as primary and secondary charges 22, 24, to provide an instantaneous-acting detonator cap. In other instan- taneous-acting caps the primary explosive charge 22 is omitted, so that the receptor charge 14 simply comprises the secondary explosive charge 24. In other detonator cap configurations, the receptor charge 14 may comprise, in addition to sealer element 16 and delay element 20, an additional, highly exothermic pyrotechnic element disposed between the sealer element and the delay element in cases where the delay element core is a relatively insensitive composition. This type of arrangement is illustrated in Figure ID, wherein parts identical to those of Figure 1 are identically numbered and the description thereof is not repeated. The detonator cap 10' of Figure ID in¬ cludes, in addition to the components of detonator cap 10 of Figure 1, a starter element 18 which comprises a pyro- technic core 18a and a sheath 18b. In other known con¬ structions, elements 16, 18 and 20 of Figure ID may be re¬ placed by what is referred to as a "rigid element". Such rigid element comprises a unitary sheath which contains in sequence (as sensed moving from open end 12b towards closed end 12a) a pyrotechnic core, a primary explosive core and a secondary explosive core. Such rigid element may be used in place of sealer element 16, starter element 18 and delay element 20. Alternatively, a sealer element 16 may be deployed adjacent to the rigid element, on the side thereof facing the open end of the detonator. Anoth¬ er known variation is a detonator which contains a delay element 20, but no sealer element 16 or starter element 18. Generally, any known type of detonator construction may be used in connection with the invention. According- ly, receptor charge 14, which provides the target for the signal (e.g., that emitted from the discharge or signal- emitting end 30a of shock tube 30) may provide either a pyrotechnic or an explosive charge target.

As shown in Figures 1A and IB, the sealer and delay elements 16, 20 each comprise respective pyrotechnic cores 16a and 20a encased within suitable respective sheaths 16b and 20b. The sheaths 16b and 20b conventionally comprise a material such as lead or aluminum which may readily be deformed by pressure or crimping. Thus, a crimp 26 may be formed in shell 12 to slightly deform lead sheath 16b, thereby securely sealing and retaining receptor charge 14 positioned within shell 12. Alternatively, the sheath may be pressed after it is placed within the shell, using a press pin. In response to the pressure, the sheath will expand and seal against the inside wall of the shell. In other cases, the sheath may be sized to have an outside diameter which is equal to or slightly larger than the in- side diameter of shell 12, to provide an interference fit. In the illustrated embodiment, receptor charge 14 in¬ cludes a pyrotechnic train comprised of elements 16 and 20 and an explosive charge comprised of primary and secondary explosive charges 22 and 24, occupies only a portion of the length of shell 12, and is disposed adjacent the closed end 12a thereof. The open end 12b of shell 12 is fitted with a retainer bushing 28 and receives one end of a length of fuse which may comprise any suitable signal transmission line, e.g., shock tube 30 as illustrated or an LVST* line or a low-energy detonating cord. The sig¬ nal-emitting end 30a of shock tube 30 is enclosed within shell 12. A crimp 32 is formed at or in the vicinity of open end 12b of shell 12 in order to grip retainer bushing 28 and shock tube 30 in place and to seal the interior of shell 12 against the environment. Accordingly, retainer bushing 28 is usually made of a resilient material such as a suitable rubber or elastomeric polymer. Shock tube 30 is of conventional construction, comprising a laminated tube having an outer tube 30b which may be made of poly- ethylene, extruded over, or co-extruded with, a sub-tube 30c which may be made of a polymer, such as a SURLYN™ ionomer, to which the reactive powder adheres. Alterna¬ tively, a monolayer tube may be employed. A dusting 30d of reactive powder (greatly exaggerated in thickness in Figure IC for clarity of illustration) clings to the inner wall provided by the inside surface of sub-tube 30c.

Isolation member 34 is interposed between the sig¬ nal-emitting end 30a of shock tube 30 and the input end of the receptor charge 14 which, in the embodiment of Figure 1, is the end of sealer element 16 which faces the open end 12b of shell 12. As best appreciated with respect to Figure 1A, the target area which the signal emitted from shock tube 30 must strike and ignite in order for the det¬ onator cap 10 to properly function is, in the illustrated embodiment, the limited area provided by the exposed igni¬ tion face end of pyrotechnic core 16a. If tube 30 is not aligned along the longitudinal axis of shell 12, for exam- pie, if tube 30 is curved at or near the signal-emitting end 30a thereof, the signal emitted from signal-emitting end 30a may not squarely strike pyrotechnic core 16a, but all or part of it may instead strike sheath 16b, thereby causing a misfire. Isolation member 34 has a positioning region 44 described below which is designed to prevent such curving of tube 30 and consequent misfiring.

Referring now to Figure 1C, isolation member 34 is seen to be seated upon the ignition face end of sealer element 16 with discharge port 56 aligned with pyrotechnic core 16a. It will be noted that although generally sub¬ stantially cylindrical in shape, isolation member 34 ta¬ pers slightly inwardly in moving from the direction (Fig¬ ure 2C) of its input end 36 towards its output end 38. In the illustrated embodiment of Figure 2C, a first section 34a of isolation member 34 has a taper angle α of, e.g., about 1 degree or less, and the longitudinally longer sec¬ ond section 34b has a slightly larger taper angle β of, e.g., from about 1 to 5 degrees. This dual-tapered con¬ figuration facilitates both removing isolation member 34 from the mold in which it is formed and insertion of iso¬ lation member 34 into snug-fitting contact, for example, interference or force fit, with the interior of shell 12. As described above, the taper angle α of the first section 34a of isolation member 34 is significantly smaller than the taper angle β of the longer, second section 34b of isolation member 34. By utilizing this construction, a sufficiently large taper, angle β, is attained to facili¬ tate mold release and insertion of isolation member 34 in- to shell 12, while the smaller taper, angle α, at the first section 34a minimizes tilting of isolation member 34 out of alignment with the longitudinal center axis of det¬ onator cap 10 after insertion of isolation member 34 into shell 12. The smaller taper of first section 34a provides a region of increased wall contact between isolation mem¬ ber 34 and the interior wall of shell 12, thereby elimi¬ nating or at least reducing the tendency of isolation mem¬ ber 34 to tilt out of longitudinal alignment. The length (along the longitudinal axis of member 34) of first sec¬ tion 34a may be increased relative to the length of second section 34b to facilitate maintaining proper alignment of member 34 within shell 12.

As is known in the art, for example, from the above- mentioned E.L. Gladden U.S. Patent 3,981,240, isolation member 34 may be molded of a semi-conductive synthetic or¬ ganic polymeric material. Thus, a suitable polymer may have carbon black or other conductive material mixed therein in order to render isolation member 34 electrical- ly semi-conductive. The term "semi-conductive" is used herein in a broad sense. It embraces a range of electri¬ cal conductivity which will cause any static electric charge which tends to build up in the interior of shock tube 30 to be conducted from signal-emitting end 30a thereof radially through the body of isolation member 34 and be grounded to the metal (or semi-conductive plastic) shell 12 of detonator cap 10 before sufficient potential builds up to cause a spark. Unless so grounded, a static electricity spark discharge could cause unintended igni- tion of reactive material 30d on the interior wall of shock tube 30 or of discharged reactive powder accumulated on the signal-rupturable diaphragm 42, or could penetrate signal-rupturable diaphragm 42 and discharge port 56 to prematurely ignite receptor charge 14. Referring now to Figures 2 to 2C, isolation member 34 is seen to have a substantially cylindrical body and an input end 36 and an output end 38. An interior passageway 40 (Figure 2C) is comprised of a positioning region 44 which opens to the input end 36 of isolation member 34, and a discharge port 56 which opens to the output end 38 of isolation member 34. Interior passageway 40 is seen to be concentrically disposed about the longitudinal axis of isolation member 34 and extends therethrough from input end 36 to output end 38. A signal-rupturable diaphragm 42, described in greater detail below, is disposed within interior passageway 40 and separates positioning region 44 from discharge port 56. Positioning region 44 comprises entry segments 52a, 52b and 52c. Entry segment 52a is an initial entry seg¬ ment which defines the mouth of positioning region 44, entry segment 52b is a second entry segment and entry segment 52c is a third entry segment. A juncture 53 is formed between segments 52a and 52b. Juncture 53, togeth¬ er with an adjacent portion of entry segment 52a, serves as a shoulder 52 to receive a signal transmission line. A juncture 54 is formed between entry segments 52b and 52c. Positioning means comprise a plurality of shoulders (three in the embodiment illustrated in Figure 2C) comprised of shoulder 52 and stepped shoulders 46, 48. Shoulders 46 and 48 are separated by longitudinally extending stepped chamfers 50a, 50b which decrease in diameter as sensed moving from input end 36 towards output end 38. Shoulders 52, 46 and 48 provide seats for signal transmission lines of different diameters (and strengths), e.g., shock tubes 30, 30' and 30'' (the latter two shown in phantom outline) as seen in Figure 1C. Shoulders 52, 46 and 48 serve to dispose the signal-emitting ends of such signal transmis- sion lines at a suitable set-off distance from the recep¬ tor charge 14. The respective inside and outside diame¬ ters of the sizes of shock tube or other signal transmis¬ sion line and their respective loadings of reactive mate¬ rial (e.g., reactive powder 30d in the case of shock tube 30) are such that the different spacings between the end of receptor charge 14 and the signal-emitting ends (30a in the case of shock tube 30) of the signal transmission line are appropriate for reliable ignition of receptor charge 14 by the signal emitted from the particular size of sig¬ nal transmission line employed.

Positioning region 44 terminates at the signal-rup¬ turable diaphragm 42, which is attached to shoulder 48, as seen in Figures 2B and 2C. Diaphragm 42 isolates the tar¬ get provided by receptor charge 14, which in the illus¬ trated embodiment is pyrotechnic core 16a, from electro¬ static discharge, which is diverted to shell 12 by isola¬ tion member 34 as described above, and prevents any dis- lodged reactive material 30d from accumulating on top of the inlet face of pyrotechnic core 16a, as is known in the art. In normal operation, the signal emitted from shock tube 30 is sufficiently powerful to rupture diaphragm 42 so that the signal extends to the inlet face of pyrotech- nic core 16a. The remaining portion of interior passage¬ way 40 is comprised of a discharge port 56 which is separ¬ ated from positioning region 44 by the diaphragm 42.

As best seen with respect to Figures 2, 2A and 2B, isolation member 34 has a plurality (four in the illu- strated embodiment) of exterior grooves 58 extending longitudinally along the exterior surface thereof. At their respective opposite ends, grooves 58 open to input radial grooves 58a and output radial grooves 58b (Figures 2B and 2A, respectively). The use of exterior longitudi- nal grooves on the outer longitudinal surface of the iso¬ lation member is a known expedient in the art to facili¬ tate inserting the isolation member into the shell 12 of detonator cap 10, the fit of a member such as the iso¬ lation member 34 in shell 12 being a snug one. The grooves extending longitudinally along the exterior sur¬ face provide a flow path for air to escape past the iso¬ lation member from the closed end 12a of shell 12 as the isolation member is force-fit inserted into the shell, thereby lessening both the resistance to smooth insertion of the isolation member and the possibility of the ex¬ pelled air rupturing diaphragm 42. The extension of such grooves radially around both the input and output ends of the isolation member 34 by the provision of radial grooves 58a and 58b in the illustrated embodiment, provides an alternate flow path for an initiation signal that fails to rupture diaphragm 42. The alternate flow path runs be¬ tween input end 36 and discharge port 56 of the isolation member exteriorly of the isolation member 34. This alter¬ nate flow path also provides a vent flow path to relieve the pressure increase inside the detonator associated with ignition of the shock tube, thereby increasing reliability as discussed in detail in co-pending patent application Serial No. 08/327.204 "Alternate Signal Path Isolation Member and Non-Electric Detonator Cap Including the Same". In use, when a signal has travelled along shock tube 30 and reaches signal-emitting end 30a, the energy and pressure pulse of the signal impinges upon diaphragm 42 of isolation member 34, rupturing the diaphragm. The signal then is directed toward the target region of a receptor charge 14, which may comprise one or more elements and ex¬ plosive charges. Since isolation member 34 is preferably made from a semi-conductive material, any static elec- tricity that builds up on shock tube 30 is shunted to the metallic shell 12 via isolation member 34, and is thus diverted away from the receptor charge to safely prevent premature, inadvertent detonations.

As indicated above, the reliability with which an in- itiation signal properly strikes the target region of the receptor charge 14 is, in some cases, affected by the way in which diaphragm 42 ruptures in response to the signal. Research regarding the performance of isolation mem¬ bers comprising non-intersecting score lines, in accord- ance with the prior art, has shown that in some instances, the signal emitted by a shock tube and received by an iso¬ lation member severs the diaphragm from the isolation mem¬ ber about the periphery of the diaphragm. At least in some instances, the separated diaphragm, which typically resembles a disk, appears to deflect the initiation signal away from the central pyrotechnic core of the receptor charge 14. In other instances, the separated diaphragm may land upon and thereby shield the pyrotechnic core, e.g., core 16a of Figure 1A, from the initiation signal. These phenomena are believed to explain, in part, at least some of the failures associated with attempted firings of detonator caps comprising isolation members according to the prior art.

An isolation member according to one embodiment of the present invention has, as shown in Figure 2A, a dia¬ phragm that has diametric intersecting score lines 42a and 42b which intersect approximately at the center of dia- phragm 42. By utilizing an isolation member having score lines that intersect at a central point on the diaphragm, the reliability of the detonator cap is improved. Without wishing to be bound by any particular theory, it is be¬ lieved that when score lines intersect each other, the diaphragm is more easily ruptured at the point of inter¬ section than at the diaphragm periphery, and that when the diaphragm ruptures at its center, the tendency for the diaphragm to separate from the isolation member about the diaphragm periphery is alleviated. Thus, when the pres- sure pulse from a signal from the shock tube or other sig¬ nal transmission line strikes diaphragm 42, the diaphragm ruptures along the score lines. As a result, generally triangular portions of the diaphragm having apices near the center of the diaphragm are severed from one another by the initiation signal and flex away from the center of the diaphragm toward receptor charge 14. The diaphragm is thus split into sector-shaped flaps or petals that remain attached to the isolation diaphragm about the circular pe¬ riphery of the diaphragm. Although the embodiment shown in Figure 2A includes a diaphragm 42 having a circular periphery, the present in¬ vention will also find utility in connection with dia¬ phragms having polygonal peripheries. For example, as shown in Figure 2D, diaphragm 42' has a rectangular pe- riphery with diagonally disposed score lines 42a' and 42b' that intersect at about the center of diaphragm 42'. In other embodiments, the diaphragm may have the peripheral configuration of a polygon other than a rectangle, e.g., a triangle, pentagon, etc. In all such polygonal periphery embodiments, it is preferred that the score lines emanate from the corners of the polygon, i.e., from apices defined by the intersection of adjacent straight-line segments of the polygonal periphery, toward a mutual intersection point approximately at the center of the diaphragm. Thus, when the diaphragm bursts along the score lines, the re¬ sulting triangular flaps can flex along straight, hinge¬ like regions at the straight-line segments of the periph- ery to allow the initiation signal to pass therethrough without becoming detached from the body of the isolation member. These straight line hinge segments will allow the triangular segments of the diaphragm to hinge open more easily than if the hinge lines are curved, thus allowing easier passage of the ignition pulse from 30a to 16a. In addition, while the invention has been illustrated as hav¬ ing a pair of orthogonal diametric grooves, this is not a limitation on the invention; in other embodiments there may be three or more radial grooves that intersect at about the center of the diaphragm, to form, e.g., a Y- shaped configuration or a star-shaped configuration.

Although illustrated embodiments show straight score lines or grooves, e.g., 42a, 42b, this should not be con¬ sidered a limitation on the invention. Instead, the in- vention should be construed to encompass diaphragms having score lines that deviate from straight line segments, e.g., one or more score lines may have a curved configura¬ tion. Similarly, although it is preferred that the score lines emanate from the periphery of the diaphragm, it is not a necessary limitation on the invention. Thus, an isolation member in accordance with the present invention may comprise a diaphragm having centrally intersecting score lines that emanate from the central intersection point toward the periphery of the diaphragm, but which terminate at a point or points on the diaphragm surface rather than at the periphery thereof. While the invention has been described in detail with respect to specific preferred embodiments thereof, it will be apparent to those skilled in the art that upon a read¬ ing and understanding of the foregoing that numerous vari- ations and alterations may be made to the disclosed embod¬ iments which nonetheless lie within the spirit and scope of the invention and the appended claims.

Claims

THE CLAIMSWhat is claimed is:

1. An isolation member for positioning the signal- emitting end of a non-electric signal transmission line within the shell of a detonator cap comprises: a substantially cylindrical body dimensioned and configured to be received within the shell of the detona¬ tor cap and having an input end, an output end and an in¬ terior passageway extending through the body for transmis¬ sion therethrough of an initiation signal from the input end to the output end of the body, the interior passageway defining a positioning region at the input end of the body and a discharge port at the outlet end of the body; and a signal-rupturable diaphragm having a periphery and disposed within the interior passageway to isolate the positioning region from the discharge port, the diaphragm being connected to the interior passageway at the periph¬ ery of the diaphragm and having a plurality of intersect¬ ing score lines formed therein to facilitate rupture of the diaphragm without detachment of the diaphragm or por¬ tions thereof from the body.

2. The isolation member of claim 1 wherein the dia¬ phragm has a generally circular periphery and the score lines intersect at approximately the geometric center of the diaphragm.

3. The isolation member of claim 1 wherein the posi¬ tioning region is comprised of a shoulder formed in the interior passageway and the diaphragm is attached at its periphery to the shoulder.

4. The isolation member of claim 2 or claim 3 where¬ in the diaphragm has a pair of score lines which extend diametrically across the diaphragm and intersect at a right angle with each other. 5. The isolation member of claim 1 wherein the dia¬ phragm has a periphery which is generally polygonal in configuration with apices defined at the intersection of adjacent straight-line segments of the periphery.

6. The isolation member of claim 5 wherein the score lines emanate from the apices of the periphery of the dia¬ phragm.

7. The isolation member of claim 1 wherein the body is substantially entirely comprised of a semi-conductive synthetic organic polymeric material.

8. The isolation member of claim 2 or claim 3 where¬ in the diaphragm has three radial score lines which inter¬ sect with each other at about the center of the diaphragm.

9. A detonator cap for connection to a length of non-electric signal transmission line terminating in a signal-emitting end, the signal transmission line having any one of a selected range of outside diameters and the cap comprising: an elongated shell having an open end for receiv¬ ing the non-electric signal transmission line and an oppo¬ site, closed end; a retainer bushing positioned in the open end of the shell and having a bore extending therethrough for re¬ ceiving therein a segment of the length of signal trans¬ mission line to connect the same to the elongated shell with the signal-emitting end of the transmission line en¬ closed within the shell; a receptor charge positioned within the elongated shell and disposed between the bushing and the closed end of the shell and axially spaced from the bushing; and an isolation member disposed within the shell in the space between the bushing and the receptor charge and comprising a substantially cylindrical body having an in¬ put end facing the open end of the shell, an output end facing the closed end of the shell and an interior pas¬ sageway extending through the body, the interior passage¬ way defining a positioning region at the input end of the body and a discharge port at the output end of the body, and a signal-rupturable diaphragm having a periphery and disposed within the interior passageway to isolate the po¬ sitioning region from the discharge port, the diaphragm being connected to the interior passageway at the periph¬ ery of the diaphragm and having a plurality of intersect¬ ing score lines formed therein to facilitate rupture of the diaphragm without detachment of the diaphragm or por¬ tions thereof from the interior passageway.

10. The detonator cap of claim 9 further including a length of signal transmission line connected to the shell and extending through the bore of the bushing with the signal-emitting end of the transmission line seated in the positioning seat.

11. The detonator cap of claim 9 or claim 10 wherein the diaphragm has a circular periphery and the score lines intersect at approximately the geometric center of the diaphragm.

12. The detonator cap of claim 9 or claim 10 wherein the positioning region is comprised of a shoulder formed in the interior passageway and the diaphragm is attached at its periphery to the shoulder.

13. The detonator cap of claim 9 or claim 10 wherein the diaphragm has a pair of score lines which extend dia¬ metrically across the diaphragm and intersect at a right angle with each other.

14. The detonator cap of claim 13 wherein the dia¬ phragm has a periphery which is polygonal in configuration with apices defined at the intersection of straight-line segments of the periphery. 15. The detonator cap of claim 9 or claim 10 wherein the score lines emanate from the apices of the periphery of the diaphragm.

16. The detonator cap of claim 9 or claim 10 wherein the isolation member is substantially entirely comprised of a semi-conductive synthetic organic polymeric material.

17. The detonator cap of claim 9 or claim 10 wherein the diaphragm has three radial score lines which intersect with each other at about the center of the diaphragm.

AMENDED CLAIMS

[received by the International Bureau on 25 April 1996 (25.04.96); original claims 1, 2, 9 and 11 amended; remaining claims unchanged (4 pages)]

1. An isolation member for positioning the signal- emitting end of a non-electric signal transmission line within the shell of a detonator cap comprises: a substantially cylindrical body dimensioned and configured to be received within the shell of the detona¬ tor cap and having an input end, an output end and an in¬ terior passageway extending through the body for transmis¬ sion therethrough of an initiation signal from the input end to the output end of the body, the interior passageway defining a positioning region at the input end of the body and a discharge port at the outlet end of the body; and a signal-rupturable diaphragm having a periphery and disposed within the interior passageway to isolate the positioning region from the discharge port, the diaphragm being connected to the interior passageway at the periph¬ ery of the diaphragm and having a plurality of score lines formed therein that intersect at about the center of the diaphragm to facilitate rupture of the diaphragm without detachment of the diaphragm or portions thereof from the body.

2. The isolation member of claim 1 wherein the dia¬ phragm has a generally circular periphery.

3. The isolation member of claim 1 wherein the pos¬ itioning region is comprised of a shoulder formed in the interior passageway and the diaphragm is attached at its periphery to the shoulder.

4. The isolation member of claim 2 or claim 3 wherein the diaphragm has a pair of score lines which extend dia¬ metrically across the diaphragm and intersect at a right angle with each other.

5. The isolation member of claim 1 wherein the dia¬ phragm has a periphery which is generally polygonal in configuration with apices defined at the intersection of adjacent straight-line segments of the periphery.

8. The isolation member of claim 2 or claim 3 wherein the diaphragm has three radial score lines which intersect with each other at about the center of the diaphragm.

9. A detonator cap for connection to a length of non¬ electric signal transmission line terminating in a signal- emitting end, the signal transmission line having any one of a selected range of outside diameters and the cap com¬ prising: an elongated shell having an open end for receiv¬ ing the non-electric signal transmission line and an oppo¬ site, closed end; a retainer bushing positioned in the open end of the shell and having a bore extending therethrough for re¬ ceiving therein a segment of the length of signal trans¬ mission line to connect the same to the elongated shell with the signal-emitting end of the transmission line en¬ closed within the shell; a receptor charge positioned within the elongated shell and disposed between the bushing and the closed end of the shell and axially spaced from the bushing; and an isolation member disposed within the shell in the space between the bushing and the receptor charge and comprising a substantially cylindrical body having an in¬ put end facing the open end of the shell, an output end facing the closed end of the shell and an interior pas¬ sageway extending through the body, the interior passage¬ way defining a positioning region at the input end of the body and a discharge port at the output end of the body, and a signal-rupturable diaphragm having a periphery and disposed within the interior passageway to isolate the po¬ sitioning region from the discharge port, the diaphragm being connected to the interior passageway at the periph¬ ery of the diaphragm and having a plurality of score lines formed therein that intersect at about the center of the diaphragm to facilitate rupture of the diaphragm without detachment of the diaphragm or portions thereof from the interior passageway.

11. The detonator cap of claim 9 or claim 10 wherein the diaphragm has a circular periphery.

14. The detonator cap of claim 13 wherein the dia¬ phragm has a periphery which is polygonal in configuration with apices defined at the intersection of straight-line segments of the periphery. 2 -

15. The detonator cap of claim 9 or claim 10 wherein the score lines emanate from the apices of the periphery of the diaphragm.