WO1999012872A1

WO1999012872A1 - Self-contained percussion output device

Info

Publication number: WO1999012872A1
Application number: PCT/US1997/015642
Authority: WO
Inventors: Richard J. Michna; William C. Hadden; Daniel P. Sutula, Jr.
Original assignee: The Ensign-Bickford Company
Priority date: 1997-09-05
Filing date: 1997-09-05
Publication date: 1999-03-18

Abstract

A percussion output device (10) is assembled from a shell (12) having an open end (12b) and a closed end (12a) that provides an inert striking plate and that defines a conduit (24) therein. A mallet member such as a ball (26) is disposed in the conduit (24) in the shell (12) near the open end (12b) of the shell (12). The ball (26) can travel through the conduit (24) to the closed end (12a). An impeller such as the signal-emitting end of a length of shock tube (14) is disposed in the open end (12b) of the shell (12). A signal emitted from the impeller, e.g., from shock tube (14), impels the ball (26) towards the closed end (12a), generating a percussion output that can be used to initiate percussion-sensitive devices. The device (10) is self-contained in that no projectile or explosive or pyrotechnic signal is released from the shell (12).

Description

SELF-CONTAINED PERCUSSION OUTPUT DEVICE

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to percussion output devices. Such output devices have a variety of uses, including the initiation of percussion-sensitive "target" devices such as primer caps. Often, the target device is used to initiate another material or device that may, for example, initiate a detonation or deflagration signal in a signal transmission line. A typical prior art percussion output device may comprise a firing pin, hammer, or other mallet member and means for impelling the mallet member, e.g., a trigger spring, as may be seen in flare guns.

Related Art A representative percussion-sensitive target device is seen in U.S. Patent

5,365,851 to Shaw, dated November 22, 1994, which discloses an initiator device for initiating a signal in a signal transmission tube. Such tubes are well-known in the art to comprise an extruded single-or-multiple-layer polymeric tube structure having a dusting of pyrotechnic or explosive material on its inner surface. The Shaw Patent discloses an end fitting that disposes a primer cap in position to be initiated by the percussive impact of a striking pin and to direct the output of the primer cap towards the signal-receiving end of a length of shock tube, to initiate a signal in the tube.

U.S. Patent 4,957,027 to Cherry, dated September 18, 1990, discloses a de- arming device comprising a length of shock tube (26) (Figure 6) having a piston (50) secured at the signal-emitting end thereof within an open-ended barrel (52). The barrel (52) provides the conduit through which the piston (50) is directed towards a conventional percussion-sensitive target device such as a gun cartridge (30), which the piston strikes directly. The cartridge (30) comprises a primer (34) that initiates a load of powder (35) which propels a clay slug (36) through a second barrel (40) (Figure 5) that can be aimed at a target. This Patent teaches firing the clay slug at an improvised explosive device (IED) in order to destroy or de-arm the IED. U.S. Patent 5,259,315 to Rekas, dated November 9, 1993, discloses a non- electric detonator in which the signal emitted from a fuse or primer tube (1) propels a striking pin (4) towards a primer cap (7), against the resistance of an elastic spherical body (8). The output of the cap (7) initiates a delay element (9), which in turn initi- ates an output charge (12).

Signal transmission lines are well-known for use in the transfer of non-electric initiation signals for the initiation of explosive or pyrotechnic devices. Brisant signal transmission lines such as detonating cord, safety fuse and the like are well-known to contain a solid core of reactive material inside a tubular sheath. Such lines are often self-consuming .and they release an explosive or pyrotechnic shock, pressure or flame front along their length when they function. Self-contained signal transmission lines are known to comprise extruded, flexible plastic tubing having a reactive material in the form of a fine powder disposed on the interior wall of the tubing, .and .are often referred to as signal transmission tubes. The reactive material is ignited to propagate a signal through the tubing, which remains intact and thus contains the signal as it passes through the tube. Typically, the signal transmission tube is of a small outside diameter and may be formed of a multi-layer tube as illustrated in U.S. Patent 4,328,753 to Kristensen et al, dated May 11, 1982, which shows the cross section of a multi-layer tube comprising .an outer layer surrounding an inner layer on the inner sur- face of which a coating of reactive powder adheres. In signal transmission tubes known as "shock tubes", the reactive powder comprises a pulverulent high explosive material, e.g., PETN or HMX aluminum powder, yielding a high velocity of signal propagation through the tube. In tubes known as "low velocity signal tubes", the reactive material comprises a deflagrating material such as manganese/potassium per- chlorate, silicon/red lead, as set forth, e.g., in U.S. Patent 4,757,764 to Thureson et al, dated July 19, 1988. The signal in a low velocity signal tube travels at a slower rate than a signal in shock tube, and by a different signal propagation mechanism. Shock tube is believed to propagate a signal therethrough by a shock wave that passes through the tube, whereas low velocity signal tubes are believed to propagate a signal therethrough by a pressure/flame front principal. SUMMARY OF THE INVENTION

The present invention relates to a percussion output device. The device comprises a shell that comprises an inert striking plate. The shell defines a conduit therein having a first end and a second end through which a mallet member may travel from one end to the other. A mallet member is disposed in the conduit at a first end thereof. The device further comprises impelling means in dynamic relation to the mallet member for impelling the mallet member through the conduit to the striking plate.

According to one aspect of the present invention, the shell and the impelling means may be dimensioned and configured to occlude the mallet member from the environment.

According to another aspect of the present invention, the device may further comprise air displacement means for allowing for the displacement of air within the shell by the mallet member as it approaches the striking plate of the shell.

According to still another aspect of the present invention, the shell and the im- pelling means may be configured to contain the signal produced by the impelling means. In such embodiments, the impelling means may be selected from the group consisting of the signal-emitting end of a length of shock tube, the signal-emitting end of a low velocity signal tube .and an impelling charge secured on the end of a length of delay fuse. This invention also provides a method for initiating a percussion-sensitive detonator from a detonating cord. The method comprises disposing a mallet member in a conduit in a shell having a closed end that provides a striking plate, the mallet member being disposed in dynamic relation to the detonating cord, disposing the percussion-sensitive detonator in impact transfer relation to the striking plate, and initiat- ing the detonating cord to propel the mallet member through the conduit to the striking plate to thereby initiate the detonator.

Another method aspect of this invention provides a method for imposing a delay in a non-electric initiation signal being transferred from a first device to a second device. This method comprises using the signal from the first device to initiate a delay means for slowing the signal, for a predetermined delay interval, after the delay interval, propelling a mallet member towards a striking plate, to create an impact therewith, .and transferring the energy of the impact of the mallet member on the striking plate to initiate a signal in the second device.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a percussion output device in accordance with a particular embodiment of the present invention, prior to function;

Figure 2 is a cross-section view of the device shown in Figure 1, with the retainer nut thereon, after function;

Figure 3 is a cross-sectional view of the device of Figures 1 and 2 coupled to a percussion-sensitive target device, prior to function;

Figure 4A is a cross-sectional view of a mallet member-guide assembly for use in a percussion output device in accordance with the present invention;

Figure 4B is a cross-sectional view of the assembly of Figure 4 A, taken along line A- A, and showing the mallet member partially deployed within a shell; Figure 4C is a perspective view of the guide of Figure 4A;

Figure 5 A is a cross-sectional view of part of a percussion output device in accordance with another embodiment of the present invention;

Figure 5B is a schematic cross-sectional view of a percussion output device with impelling means comprising a detonating cord in accordance with still another embodiment of the present invention;

Figure 5C is a schematic cross-sectional view of a percussion output device similar to that of Figure 5B but with an optional impulse dissipation means;

Figure 5D is a schematic cross-sectional view of an alternative embodiment of a percussion output device comprising impulse dissipation means; Figure 6 is a partly cross-sectional elevation view of a percussion output device comprising impelling means comprising a delay means and a discrete explosive charge; and

Figure 7 is a partly cross-sectional elevation view of the device of Figure 6 coupled to a signal-emitting device and a percussion-sensitive signal-receiving device, for interposing a delay in transferring a signal from one device to the other. DETAILED DESCRIPTION OF THE

INVENTION AND PREFERRED EMBODIMENTS THEREOF

The present invention relates to a device that provides a percussive output through an inert striking plate by impelling a mallet member towards the striking plate. The device may comprise a non-mechanical and, preferably, non-electric impelling means for the mallet member. For example, the impelling means can comprise, e.g., a signal transmission line such as detonating cord or a delay fuse, or a signal transmission tube such as shock tube or low velocity signal tube, or a discrete explosive or pyrotechnic charge, or a combination thereof, as described below. Each of the foregoing impelling means provides a non-electric, non-mechanical signal that impels the mallet member towards the striking plate.

The present invention differs from the device shown in the Cherry Patent described above, U.S. 4,957,027, in that the mallet member of the present invention is disposed within a closed-ended shell comprising an inert striking plate whereas Cherry's device requires the mallet member (piston 50) to strike a percussion-sensitive pyrotechnic target device (e.g., cartridge 30). In addition, the mallet member in a device according to the present invention is separated from the target device by the striking plate, and is preferably enclosed or "occluded" by the shell and the impelling means, and is thus physically isolated at least from the target device and, preferably, from the environment. For example, the mallet member may be disposed in the conduit of a generally cylindrical shell having one end closed by the striking plate and the other end being occluded by the impelling means, as will be described below. In contrast, an open-ended shell or barrel (as shown by Cherry) would leave at least the mallet member, and possibly the impelling means, vulnerable to exposure and possi- ble deterioration from environmental contaminants, e.g., moisture, that may enter through the open end of the barrel unless and until a target device is secured thereto. By enclosing the mallet member and, preferably, the output of the impelling means, the present invention avoids such contamination and the possible interference with the output function even before a target device is in place. Further, the closed-ended shell of the present invention will retain the mallet member when the device functions, whether the target device is in place or not, thus avoiding the release of a projectile. In contrast, if a signal is emitted by shock tube (26) of Cherry's device before the tar- get device, e.g., gun cartridge (30), is in place, the open-ended barrel will permit the piston (50) to be ejected from the barrel (52) as a projectile, posing a hazard to the user.

The present invention differs from the detonator shown in the Rekas Patent discussed above, U.S. 5,259,315, at least because the output of the present invention is principally percussive; there is no explosive output necessary for this invention as is required from Rekas' detonator.

Broadly described, a preferred embodiment of the present invention comprises a shell having a closed end, within which is disposed a mallet member at a position remote from the closed end of the shell. Within the shell there is a bore or conduit through which the mallet member may be impelled. An impelling means is disposed in dynamic relation to the mallet member in a position from which it can propel the mallet member through the conduit. Typically, the impelling means is secured to or within the shell at one end of the conduit. A closed end of the shell comprises a striking plate at the end of the conduit opposite from the impelling means, to bear the impact of the mallet member. Preferably, the striking plate is inert and malleable and can be deformed by the impact of the mallet member. In operation, the impelling means impels the mallet member through the conduit towards the closed end of the shell, i.e., towards the striking plate, which bears the impact of the mallet member and, in response thereto, emits a percussion output in the form of a shock wave or a physical deformation of the shell, i.e., a bulge, or both. Since the striking plate of the device is inert, and since the impelling means preferably does not comprise a charge of explosive or pyrotechnic material sufficient to burst the closed end of the shell, the device emits only a percussion output when functioned apart from a target device; no explosive or pyrotechnic signal is released. Thus, one feature of particular embodiments of the present invention is the containment of an output signal from the impelling means and another such feature is the lack of an explosive or pyrotechnic output from the shell. A device in accordance with some embodiments of this invention can therefore be described as comprising only (or consisting essentially of) charges of explosive or pyrotechnic materials whose output signals are containable by the shell. This is one way in which the present invention offers improved safety relative to the prior art. In addition, the device contains or occludes the mallet member before and after it functions. Occluding the mallet member improves the reliability of the device by protecting the impelling means and the mallet member from environmental contamination, and it assures that no projectile will be released from the device when it functions. Thus, due to the containment (or occlusion) of the mallet member and the containment of the signal of the impelling means, the device of the present invention is safer, less noisy and more reliable in operation than prior art devices.

To facilitate movement of a mallet member through the conduit, the device may comprise air displacement means. The air displacement means ameliorates the compression of air between the mallet member and the striking plate so that the for- ward movement of the mallet member and, therefore, its impact energy, is not detrimentally diminished by the compression of air in the conduit. For example, the device may define a pressure-relief volume, as discussed below.

Optionally, the device comprises coupling means to facilitate securing the device to a percussion-sensitive target device or to a coupler for a target device. Such coupling means may comprise, e.g., a flange suited for a bayonet-style coupling, a tightening nut, a threaded surface, etc.

Figure 1 shows a percussion output device 10 in accordance with one embodiment of the invention, prior to functioning. Output device 10 comprises a generally cylindrical shell 12 having a closed end 12a and an open end 12b. Shell 12 is mounted on the end of a length of shock tube 14, which provides the impelling means of the device. Shell 12 comprises coupling means including a collet 12c to provide a shoulder 12d against which an externally threaded nut mounted on the exterior surface of shell 12 may bear. Shock tube 14 is surrounded by bushing 16 onto which the open end 12b of shell 12 is crimped at 18a, 18b. Bushing 16 functions to help establish a hermetic seal about shock tube 14, thus inhibiting the entry of contaminants such as environmental moisture into the interior of shock tube 14 and shell 12, and inhibiting the release of a signal emitted from shock tube 14. The signal-emitting end 14a of shock tube 14 abuts an optional isolation cup 20, which is well-known in the art for the dissipation of static charges. Isolation cup 20 abuts a guide 22. (Isolation cup 20 may be eliminated or it may be replaced with a conductive ball 26 within guide 22 composed of a static-dissipative polymeric material.) Guide 22 is dimensioned and configured to engage the interior surface of shell 12 and to define a central bore or conduit 24, but part of guide 22 is configured to allow spaces 22a, 22b between guide 22 and shell 12, for reasons described below. Guide 22 is shown as a separate structure from shell 12, but in alternative embodiments, the guide may be formed integrally with the shell in a single unit. When formed as a separate structure, guide 22 may be formed from a polymeric material such as nylon, high density polyethylene or the like. Conduit 24 has two ends, a first end near open end 12b of shell 12 and a second end near closed end 12a of shell 12.

One end of conduit 24 is near the signal-emitting end 14a of shock tube 14 while the other end of conduit 24 opens to the closed end 12a of shell 12. A mallet member such as ball 26 is disposed in guide 22 at the end of conduit 24 near the signal-emitting end 14a at the open end 12b of shock tube 14. The conduit 24 is dimensioned and configured so that the ball 26 can travel therethrough from the first end to the second end, to strike the striking plate at closed end 12a.

Shell 12 and, therefore, closed end 12a, are formed from aluminum, a non- explosive material, and thus constitutes the inert striking plate of the illustrated embodiment since it receives the impact of ball 26 without generating a pyrotechnic or explosive signal. Although not shown in Figures 1, 2 or 3, means are provided to temporarily hold ball 26 near the signal-emitting end 14a of shock tube 14, e.g., guide 22 may comprise a shallow interior circumferential groove in conduit 24 sized to provide a stop for ball 26, or it may define a seat such as seat 76 (Figure 4A) or .an internal fence 82a (Figure 5 A) for this purpose. Alternatively, ball 26 may be sized to have a friction fit in the conduit. As can be seen in Figure 1, ball 26 is occluded, or completely enclosed, by shell 12 and shock tube 14, e.g., there is no opening in shell 12 that exposes ball 26 to the environment or that allows ball 26 to exit shell 12 when it is impelled by shock tube 14.

In a typical embodiment, shell 12 may be formed from aluminum having (at portions other than collet 12c) a thickness of 0.017 to 0.022 inch. Shock tube 14 may have an interior diameter of 0.05 inch and a loading of reactive material therein of about 14.5 milligrams per meter; ball 26 may have a diameter of 0.054 inch and may be made from steel, and the length of conduit 24 may be about 0.75 inch.

Figure 2 depicts the device 10 after functioning in an unconfmed environment, i.e., after the signal emitted from end 14a of shock tube 14 has breached the isolation cup 20 and impelled ball 26 through conduit 24 to strike the closed end (or "striking plate") 12a of shell 12. In an unconfined environment, there is no target device pressed against closed end 12a, so the impact of ball 26 causes a bulge 12f. Figure 2 illustrates that shell 12 remains intact after device 10 functions, thus containing the output signal from shock tube 14 and the mallet member therein. Therefore, device 10 functions without the release of explosive or pyrotechnic reaction products (i.e., it is non-brisant), without releasing a projectile, and without significant noise output. In these ways, device 10 is uniquely self-contained and quiet. Figure 2 also illustrates that shell 12 has a cylindrical exterior mounting surface 12e on which can be disposed a rotatable, externally threaded nut 28 for use in coupling device 10 to a target device. Nut 28 and collet 12c comprise coupling means for device 10. Since the impelling means of device 10 comprises shock tube 14, which is well-known for containing an initiation signal traveling therethrough, and since the signal-emitting end of shock tube 14 is sealed within shell 12, device 10 effectively contains the signal produced by the impelling means to impel the mallet member. Thus, the impelling means and the shell are dimensioned and configured to contain the signal produced by the impelling means.

Figure 3 shows, on the left, device 10 coupled to a percussion-sensitive target device via a coupler 30, prior to functioning. The illustrated target device is an initia- tion fixture 50 mounted on a shock tube 52, as disclosed in U.S. Patent 5,365,851

(discussed above). As indicated above, nut 28 of device 10 is threaded into coupler 30 to urge end 12a towards initiation fixture 50 by bearing on shoulder 12d. The target device is equipped with a similar coupling means as device 10, so coupler 30 serves as an adapter. In alternative embodiments, the percussion output device and the target device may comprise complementary (e.g., male/female) coupling means.

Initiation fixture 50 comprises .an end sleeve 54 which is generally cylindrical in configuration and which has a longitudinal internal bore. The signal-receiving end of shock tube 52 is inserted into the internal bore of end sleeve 54 with an intervening closure bushing 56. Then, end sleeve 54 is crimped, for example, at crimps 58a, 58b, to secure end sleeve 54 onto shock tube 52. The internal bore of end sleeve 54 has an annular internal fence 62 having a central aperture that defines a cap receptacle at the proximal end of sleeve 54, for receiving a self-contained, percussion-sensitive initiat- ing charge, such as a primer cap 60. Primer cap 60 may comprise a conventional, relatively low-strength primer cap available from Olin Corporation under the designation M42C1. Preferably, the cap receptacle provides a friction fit for primer cap 60, thus sealing off the interior of end sleeve 54. When primer cap 60 is in place, the proximal end of end sleeve 54 (relative to device 10) may be hermetically sealed by applying a coating of a varnish or similar sealant to the end of the initiation fixture. Thus, closure bushing 56 .and the sealant at the end of the initiation fixture together provide a hermetically sealed closure for the interior of shock tube 52.

The central aperture in fence 62 provides a touch hole 64, of a diameter smaller than the diameter of primer cap 60, for guiding the energy released from primer cap 60 towards the signal-receiving end of shock tube 52.

An isolation cup 66 is disposed against the distal side offence 62. The interior of isolation cup 66 is dimensioned and configured to receive the end of shock tube 52. Closure bushing 56 may engage the edge of isolation cup 66. As is known in the art, isolation cup 66 serves to disperse static electricity which may develop through the handling of shock tube 52, thus preventing the electricity from discharging from the end of shock tube 52 directly to primer cap 60 and prematurely initiating the cap. Isolation cup 66 also advantageously provides a stand-off space between the signal- receiving end of shock tube 52 and touch hole 64 in fence 62. The transmission of a signal from cap 60 to shock tube 52 through touch hole 64 and isolation cup 66 occurs in virtual silence.

Like shell 12, sleeve 54 has a cylindrical surface on which an externally threaded nut 68 can rotate, to thread into a coupler such as coupler 30 and, by bearing on shoulder 70 formed by collar 72, to urge primer cap 60 towards closed end 12a of shell 12. Primer cap 60 is thus positioned to receive the impact of striking ball 26 on end 12a. Ideally, primer cap 60 is disposed in contact with end 12a before device 10 functions, so that it receives the full impact of striking ball 26 through shell end 12a. In such a configuration, end 12a typically does not form a bulge as in the uncoupled environment of Figure 2 either because the energy of the impact of striking ball 26 is transferred to the adjacent structure, i.e., to primer cap 60, or because the output of primer cap 60 at least partially flattens a bulge in end 12a formed by the impelling means. In use, device 10 .and initiation fixture 50 .are secured in coupler 30 to position cap 60 in initiation relation to end 12a of shell 12. A signal in shock tube 14 penetrates isolation cup 20 and impels ball 26 towards closed end 12a of shell 12. The impact of ball 26 on closed end 12a is conveyed to primer cap 60. Cap 60 generates a signal that penetrates isolation cup 66 and touch hole 64 and initiates a signal in the signal-receiving end of shock tube 52. Shock tube 52 carries the signal along its length to its opposite, signal-emitting end, on which a signal-receiving device, e.g., a detonator (not shown), may be secured.

Figures 4A and 4B depict a mallet member-guide assembly 74 comprising anti-static ball 26' and a guide 22' which has conduit 24' for use in shell 12. For clarity, a perspective view of guide 22' is provided in Figure 4C. Guide 22' forms a seat 76 configured to retain ball 26' securely enough so that it stays in position during shipping, handling and installation, but to allow ball 26' to be discharged therefrom by the impulse signal emitted from a shock tube. This assembly may be manufactured by insertion molding the metal ball 26' within the semi-conductive guide 22', or the ball 26' may be inserted as a secondary operation. Figure 4B depicts a longitudinal cross section of the assembly shown in Figure 4A taken along the line A- A, and shows the guide 22' inside shell 12 to illustrate how the guide is dimensioned and configured to provide air displacement means within the shell. Guide 22' comprises an externally cylindrical seat portion 32 that is dimensioned and configured to fully engage the cylindrical interior of shell 12. The remainder of guide 22' comprises a beveled portion 34 (see also Figure 4C) that has truncated sides 82 to leave spaces 22a, 22b between guide 22' and the shell, and a notch 80. Notch 80 and truncated sides 82 cooperate to allow ball 26' to displace air in conduit 24' into spaces 22a, 22b (as suggested by air flow arrows 78) as the ball advances towards the striking plate, i.e., towards end 12a', as indicated by ball advancement arrow 78a. Thus, spaces 22a, 22b act as pressure relief volumes, and the air in shell 12 will therefore not become excessively compressed by ball 26' and will not significantly dissipate the impact energy of ball 26' on the striking plate provided by end 12a of shell 12. A shell comprising an alternative form of air dispersment means in accordance with another embodiment of the present invention is shown in Figure 5 A. Within shell 12' there is a guide and ball assembly comprising a guide 22' and a ball 26. Guide 22' defines a conduit 24' that opens to end 12a' of shell 12' and comprises an internal annular fence 82a that defines a seat portion 82b where a mallet member such as a ball 26' may initially reside (as shown in dotted outline). When impelled by an impelling means (not shown), the ball 26' is ejected from the seat and travels through conduit 24' towards end 12a', which constitutes the inert striking plate of the device 12. An intermediate portion 24a' of conduit 24' contiguous with seat portion 82b has an internal diameter approximately equal to that of ball 26', so that as ball 26' approaches closed end 12a', the air within conduit 24' between ball 26' and closed end 12a' becomes compressed. However, shell 12' comprises air displacement means in the form of a part of an end chamber portion of 24b' of conduit 24' that is contiguous with closed end 12a' and into which intermediate portion 24a' opens. End chamber 24b' has a larger diameter than ball 26', so that as ball 26' enters end chamber 24b', the air compressed between ball 26' and end 12a' can then flow around ball 26', and the intermediate portion 24a' of conduit 24' can act as a pressure relief volume. The iner- tia of ball 26' carries ball 26' onward to its impact with end 12a'.

A percussion output device according to an embodiment of the present invention is shown in Figure 5B. Device 84 comprises shell 12' within which is disposed a ball and guide assembly comprising the guide 22' and ball 26' of Figure 5 A. Shell 12' comprises impelling means in the form of sleeve 12g', for slidably receiving therein impelling means in the form of a detonating cord 86. When threaded through sleeve 12g', detonating cord 86 is disposed in dynamic relation to ball 26', so that when detonating cord 86 initiates, its radial output will impel ball 26' through guide 22' to strike end 12a'.

A percussion-activated detonator 85 is secured at the output end of device 84 as a target device for device 84. Detonator 85 comprises a detonator shell 87 that contains an output charge 88, which typically comprises a secondary explosive material. Also contained within detonator shell 87 is a percussion-sensitive initiator 90. The input end of detonator 85 is secured by coupling means 92 to position initiator 90 in impact transfer relation to device 84. In use, the initiation of detonating cord 86 impels ball 26' through guide 22' so that it strikes end 12a'. The energy of the impact is transferred to initiator 90, which initiates output charge 88 of the detonator. The detonator may be positioned to initiate some other device, as desired. Device 84 par- tially shields detonator 85 from device 84 and interposes a minimum stand-off distance 94 between them, thus attenuating the force of the output signal from detonating cord 86. Accordingly, detonator 85 can be initiated by detonating cord 86 with reduced danger of detonating cord 86 damaging detonator 85 (or its target device, e.g., a primer charge) in a manner that prevents its proper function. In a particular embodiment, detonating cord 86 of the impelling means may comprise a downline detonating cord for use in a borehole blasting environment. Detonator 85 may be secured within a conventional cylindrical booster charge comprising, e.g., PETN, which may be used to initiate the borehole explosive charge, which typically comprises ANFO (a mixture of ammonium nitrate and fuel oil). Percussion output device 84 and stand-off 94 provide added reliability by assuring for the reliable initiation of detonator 85 and, consequently, the initiation of an associated booster charge and, in turn, the borehole explosive charge, with reduced risk that the initiation of detonating cord 86 could damage detonator 85 or the associated booster charge or other target device. In another embodiment, the percussion output device may comprise a diffusion chamber between the impelling means and one or both of the mallet member and the target device. The energy impulse generated by the impelling means is transferred through the diffusion chamber to impel the mallet member, but it is drawn out by the diffusion ch.amber to reduce the risk of damage to the mallet member or another com- ponent of the percussion output device, the target device, or the coupling means that holds the target device to the percussion output device. A diffusion chamber provides a volume between the impelling means and that may be, for example, about four times as large as the volume of the conduit between the mallet member and the striking plate before the impelling means is activated, or larger. Thus, the shell 212 of per- cussion output device 84', Figure 5C, includes a diffusion chamber 214 between the mallet member (ball 26') and the impelling means (detonating cord 86'). A connector block (not shown) may be configured to retain device 84' and detonating cord 86' in operative relation to each other. In a similarly configured percussion output device 84", the shell 212' (Figure 5D) comprises retaining means such as a tubular holder 212a' for retaining detonating cord 86' in operative relation to diffusion chamber 214. In both embodiments, diffusion chamber 214 dissipates the output of detonating cord 86^* before it bears on ball 26'. In addition, diffusion chamber 214 adds, between the t.arget device .and detonating cord 86', an additional stand-off distance 194 to the minimum stand-off distance 94 principally attributed to the length of the conduit in the device. Preferably, diffusion chamber 214 is dimensioned and configured so that the output of detonating cord 86' can impel ball 26' effectively towards the striking plate of closed end 12a' without damage to the target device or to the coupling means holding the percussion output device 84' to the target device (detonator 85).

A percussion output device according to the present invention and comprising yet another type of impelling means is illustrated in Figure 6. Device 10" comprises the ball and guide assembly of Figure 5 A disposed within a shell 12" so that conduit 24' opens to end 12a" of shell 12". Shell 12" comprises coupling means in the form of an internally threaded ferrule 95. Device 10" comprises impelling means 96 that comprises an externally threaded ferrule 98 that is dimensioned and configured to engage the internal threads of ferrule 95. Impelling means 96 further comprises a generally tubule stem member 100 that defines an internal bore 102 extending longitudi- nally therethrough. Stem member 100 provides an input end 100a and an output end 100b for impelling me∑ms 96. Disposed within bore 102 is a delay means comprising a length of delay fuse 104 that extends from a first end at input end 100a to a second end at output end 100b. Stem member 100 defines an optional orifice 106 that allows a segment of delay fuse 104 to emerge from bore 102, loop .around stem member 100 and re-enter bore 102, thus defining a loop portion 104a outside of stem member 100 but within ferrule 98. Secured on the second end of delay fuse 104 is an end cap 110 that contains an impelling charge 108. Impelling charge 108 comprises a charge of explosive material. End cap 110 is secured in the output end 100b of impelling means 96. Impelling means 96 is dimensioned and configured so that when ferrule 98 threadably engages ferrule 95, impelling charge 108 is positioned in dynamic relation to ball 26'. In the illustrated embodiment, a transfer member 112 is disposed between guide 22' and the output end 100b of impelling means 96. Transfer member 112 is dimensioned and configured to focus the output signal produced by impelling charge 108 onto ball 26'. Impelling charge 108 has sufficient brisance to breach end cap 110 and to propel ball 26' to end 12a", but is not powerful enough to rupture or breach shell 12". The input end 100a of impelling means 96 is dimensioned and configured to engage a conventional initiation device for delay fuse 104. For example, input end 100a may comprise a seat 100c within which a standard primer cap may be secured. In use, .an initiation signal is received at input end 100a to initiate delay fuse 104. The signal travels through delay fuse 104 to impelling charge 108, thus interposing a predetermined delay between the initiation of the impelling means, e.g., at input end 100a, and the output of the impelling means, e.g., the initiation of impelling charge 108. The orifice 106 in stem member 100 gives the designer the option of configuring delay fuse 104 to either pass straight through bore 102 in the shortest dis- tance from input end 100a to output end 100b to provide a short delay interval or to loop around stem member 100 in one or more optional loops such as loop 104a, to increase the length and therefore the delay interval imposed by the delay fuse 104. Upon receipt of the signal from delay fuse 104, impelling charge 108 produces an output signal that passes through transfer member 112 and impels ball 26' towards shell end 12a", to produce the percussion output of the device.

If device 10" of Figure 6 is equipped with a percussion-sensitive primer cap in seat 100c as part of the impelling means, device 10" would be dimensioned and configured to contain the signal produced by the impelling means therein. Therefore, the operation of device 10" will not result in the emission of any pyrotechnic or explosive signal or in the release of a projectile. Accordingly, the device is advantageously safe for the user and can be safely and conveniently transported. Such a device would not be accorded a hazardous U.S. Department of Transportation shipping classification, and would therefore be less difficult to ship in accordance with applicable regulations than prior art initiation devices. Device 10" is shown in Figure 7 as the target device for device 10 of Figure 1, in an embodiment in which input end 100a is equipped with a percussion-sensitive primer cap 114 that is capable of initiating delay fuse 104. Device 10" is shown in use to interpose a delay in the transfer of a brisant, non-electric signal from one device, e.g., a signal transmission line comprising shock tube 14, to a second device, e.g., shock tube 14". Input end 100a is engaged by a coupler 116a which positions primer cap 114 in impact transfer relation to the output end of a percussion output device 10 of Figure 1 by means of a coupling nut 105 that threadably engages coupler 116a. Similarly, the closed end 12a" of device 10" is secured within a second coupler 116b. Also secured in coupler 116b is the target device of device 10", a percussion-sensitive initiation fixture 118 that is secured onto shock tube 14". Initiation fixture 118 comprises a percussion-sensitive initiation charge 120 that is disposed in dynamic transfer relation to output end 12a" of device 10". In operation, a shock tube signal received in shock tube 14 propels a first ball 26 to the closed end of the shell secured onto shock tube 14, thus creating a percussion output. The percussion output initiates the impelling means of device 10" by initiating primer cap 114, which in turn initiates a signal in delay fuse 104. The signal travels through delay fuse 104 over a predetermined in- terval and then initiates impelling charge 108, which impels ball 26' towards closed end 12a" of device 10". The energy of the resulting impact is transferred to initiation charge 120, which in turn initiates a signal in shock tube 14". Thus, a shock tube signal is transferred from shock tube 14 to 14" .and a predetermined delay is imposed on the signal. The signal tr.ansfer and delay are achieved entirely with contained physi- cal, pyrotechnic and small, non-breaching explosive signals so that the device can be used with a high degree of safety. Since all of the illustrated components, i.e., device 10", initiating fixture 118 .and device 10", are all sealed against contamination when manufactured, these components may be separately transported to the field and effectively interconnected by field personnel without special tooling. The invention has been described in detail with respect to particular embodiments thereof, but many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification which discloses the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are intended as part of the invention which is to be limited only by the appended claims.

Claims

THE CLAIMSWhat is claimed is:

1. A percussion output device, comprising: a shell comprising an inert striking plate and defining a conduit therein having a first end and a second end, through which a mallet member can travel from one end to the other; a mallet member disposed in the conduit at a first end thereof; and impelling means in dynamic relation to the mallet member, for impelling the mallet member through the conduit to the striking plate.

2. The device of claim 1 wherein the shell and the impelling means are dimensioned and configured to occlude the mallet member from the environment.

3. The device of claim 2 comprising air displacement means for allowing for the displacement of air from between the mallet member and the striking plate as the mallet member approaches the striking plate.

4. The device of claim 1, claim 2 or claim 3 wherein the shell and the impelling means are dimensioned and configured to contain the signal produced by the impelling means.

5. The device of claim 4 comprising impelling means selected from the group consisting of the signal-emitting end of a length of shock tube, the signal-emitting end of a low velocity signal tube and an impelling charge secured on the end of a length of delay fuse.

6. A method for initiating a percussion-sensitive detonator from a detonating cord, comprising: disposing a mallet member in a conduit in a shell having a closed end that provides a striking plate, the mallet member being disposed in dynamic relation to the detonating cord; disposing the percussion-sensitive detonator in impact transfer relation to the striking plate; and initiating the detonating cord to propel the mallet member through the conduit to the striking plate to thereby initiate the detonator.

7. A method for imposing a delay in a non-electric initiation signal being transferred from a first device to a second device, the method comprising: using the signal from the first device to initiate a delay means for slowing the signal, for a predetermined delay interval; after the delay interval, propelling a mallet member towards a striking plate, to create an impact therewith; .and transferring the energy of the impact of the mallet member on the striking plate to initiate a signal in the second device.

8. The device of claim 1 or claim 2 or claim 3 further comprising a diffusion chamber between the impelling means .and the mallet member.