US3815505A

US3815505A - Self-destructing apparatus for impact-detonating explosive devices

Info

Publication number: US3815505A
Application number: US00310092A
Authority: US
Inventors: P Roh; M Strunk
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1972-11-28
Filing date: 1972-11-28
Publication date: 1974-06-11
Anticipated expiration: 1991-06-11
Also published as: BE791993A; GB1401827A; FR2208516A5; NL7216146A

Abstract

A self-destructing apparatus for impact-detonating explosive devices having a piezoelectric fuze responsive to sonic waves for detonation of the device. The apparatus includes means responsive to at least one of firing or dropping of the impact-detonating explosive device for triggering a sonic wave generator after a predetermined time delay, the sonic wave produced by the generator being transmitted to the piezoelectric fuze for detonation of the explosive device, thereby ensuring destruction of the device.

Description

United States-Patent [191 Rob et a1.

[ June 11, 1974' SELF-DESTRUCTING APPARATUS FOR IMPACT-DETONATING EXPLOSIVE DEVICES [75] Inventors: Peter Roh; Manfred Strunk, both of Troisdorf, Germany [73] Assignee: Dynamit Nobel Aktiengesellschaft,

Troisdorf, Germany 22 Filedz Nov.28, 1972 21 Appl. No.: 310,092

[52] US. Cl. 102/70.2 GA, 102/74, 102/78, 102/83 [51] Int. Cl...... F42c 1l/02, F22c 9/00, F426 11/06 [58] Field of Search.. 102/70.2 GA, 70.2 R, 70.2 A, 102/72, 71, 74,78, 82, 83, 84, 85, 85.6

[56] References Cited UNITED STATES PATENTS 2,515,040 7/1950 Hatcher 102/72 2,827,851 3/1958 Ferrara 102/70.2 GA 2,870,712 l/1959 Brown et a1 l02/70.2 GA

2,938,461 Rabinow 102/70.2 R 3,043,222 7/1962 Kaspanl l02/70.2 R 3,078,802 2/1963 Sturrock 102/72 3,320,890 5/1967 Ciccone et a1... l02/70.2 GA 3,356,026 12/1967 Lubig 102/702 GA 3,371,608 3/1968 Webb 102/72 Primary Examiner-Samuel W. Engle Assistant ExaminerC. T. Jordan Attorney, Agent, 0r Firm-Craig & Antonelli [5 7] 'ABSTRACT A self-destructing apparatus for impact-detonating explosive devices having a piezoelectric fuze responsive to sonicwaves for detonation of the device. The apparatus includes means responsive to at least one of firing or dropping of the impact-detonating explosive device for triggering a sonic wave generator after a predetermined time delay, the sonic wave produced by the generator being transmitted to the piezoelectric fuze for detonation of the explosive device, thereby ensuringdestruction of the device.

14 Claims, 3 Drawing Figures AWQM L j PATENTEDJUM 1 1 m4 3.815.505

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FIG

SELF-DESTRUCTING APPARATUS'FOR IMPACT-DETONATING EXPLOSIVE DEVICES The present invention relates to a self-destruction device for explosive devices detonating'on impact, such as, for example, projectiles, rockets, or bombs, having a piezoelectric fuze which can be triggered by sonic shock waves.

Many varieties of piezoelectric detonators are known for projectiles, rockets, bombs, or the like, and described in detail, for example, in US. Pat. No. 3,356,026. It is furthermore known from US. Pat. No. 2,894,457 thatpiezoelectricfuzescanbe triggered by sonic shock waves which are produced in the explosive device when impinging upon the target after having been fired or dropped with the sonic waves passing via the .wall of the explosive device to the detonator for generating the ignition voltage in the piezo crystal.

For reasons of safety, it is basically desirable to construct percussive explosive devices, if at all possible, in such a manner that they self-destruct, if they fail to detonate by contact with the target within a predetermined period of time after firing or dropping.

Accordingly, it'is. the objective of the present invention to provide an impact explosive device with a piezoelectric fuzev'vhich can be triggered by sonic waves and to artificially produce in the percussion explosive device, a sonic wave for triggering the piezoelectric fuze after the elapse of a predetermined time interval after firing or dropping of the explosive device.

stant of ignition of the detonator, so that the sonic wave,

produced during the reaction of the detonator is transmitted to the piezoelectric fuze. The manner in which the spatial arrangement of the piezoelectric fuze and the detonator is advantageously provided, i.e., whether these components are disposed, for example, separately from each other or in a parallel or series disposition in a common housing, depends on the requirements in each individualcase. However, in any event, the important factor is a maximally advantageous sound transmission from thedetonator to the piezo crystal, so that a detonator of such .a size'is utilized which cannot ignite or damage the impact explosive device directly, i.e., circumventing the piezoelectric fuze. Such an arrangement thus ensures that it is impossible for the impact explosive device to become inoperable or even to detonate in case of an unintended premature triggering of the self-destruction device i.e., as long as the piezoelectric fuze is still in the safety position.

The delay line can be constructed conventionally on an electronic basis, by providing that electrical energy, supplied upon the firing or dropping of the percussion explosive device, for example, from the outside, is transmitted via capacitors, resistors and other circuit components with a desired delay to an electrically ignitable detonator. However, in order to be able to construct the fuze with the self-destruction unit advantageously as a self-contained, compact structural device without extraneous electrical contacts, in accordance with the present invention, the delay line may be selected in a known manner as a pyrotechnical mixture ignitable with the aid of an impactor friction-sensitive primer element and to maintain, at a spacing from the primer element, an ignition pin in a locked position which can be overcome, likewise in a conventional manner, by inertial forces, this-pin being movable toward the primer element by means of inertial forces, spring force, or the like. In this connection, it is, of course, also within the teachings of the present invention to employ, in place of the hitting or striking primer element with firing pin or striker pin, an electrically ignitable primer element which derives the electrical energy required for ignition, for example, from a battery installed therein.

In accordance with another embodiment of the present invention, the delay process, as well as the sound generation, are effected mechanically by holding a striker pin at a spacing from an impingement surface associated with the piezoelectric fuze by means of a locking action, against the force of a compression spring, which locking action can be overcome in a conventional manner by inertial forces. The striker pin is provided with a serration, anda conventional blocking gear meshes therewith, so that the movement of the fir ing pin against the impingement surface can be retarded in a predetermined manner. The striking surface is in such a spatial arrangement with respect to the fuze that the satisfactory sound transmission'to the piezo crystal is also ensured in this case. I

A particularly favorable transmission of the sonic waveto the piezo crystal is obtained by providing that theimpingement surface is part of one of the two abutments of the piezoelectric fuze. The abutment contacting the piezo crystal is constructed so that it can absorb the impact forces occurring upon impingment of the striker pin, without the function of the piezoelectric fuze being impaired thereby.

In case a reinforcement of the impact power of the striker piniis considered advantageous, inaccordance with a further feature of the present invention, the impingement surface is formed as part of an impactsensitive detonator, from which the sonic wave is then transmitted to the piezo crystal.

These and further objects, features and advantages of the present-invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein FIG. 1 is a longitudinal sectional view of a piezoelectric fuze with a self-destructing device provided with a pyrotechnical delay unit;

FIG. 2 is a longitudinal sectional view of a piezoelectric fuze with a self-destructing device provided with a mechanical delay unit; and

FIG. 3 is a schematic circuit diagram for an electronicdelay unit in accordance with the present invention.

Referring now to the drawings wherein like reference numerals are utilized to designate like parts throughout the several views and more particularly to FIG. I, a piezoelectric fuze and a self-destructing device are disposed side-by-side in an outer housing 23, which can be inserted, for example, in the bottom of a projectile, not shown, with a propagation charge 9 arranged at one end pointing into the flight direction. The piezoelectric fuze is installed in the housing 1 and is provided with a safety mechanism for placing the fuze in the armed condition only during or shortly after the firing of the projectile. For this purpose, a spring 2 is compressed by a stud 3 upon firing, by the inertia of the latter, so that an arming ball 4 is released and a rotor 5 can be pivoted by a biased torsion spring 6, to such an extent that a detonator 7 contacts with its central contact, not shown, a displaceably arranged contact element 8 and comes into engagement with the propagation charge 9 with its opposed end face for placing the fuze in the armed position. The contact element 8 is in electrically conductive connection via a compression spring 10 and one abutment 24 with a piezo crystal 11, which crystal is insulated on one side from the housing 1 by means of an insulating cup 12. The other side of the piezo crystal 11 is in electrically conductive connection with the outer casing of the electrically ignitable detonator 7 via another abutment 13, the housing 1, and the rotor 5. Upon the impingement of a sonic wave on the fuze, an electric voltage is produced in the piezo crystal 11 which serves for igniting the detonator 7.

An annular casing 14 is disposed around the housing I and the self-destructing device is arranged within two parallel-arranged bores of the casing. Upon firing, a pin 16 is displaced, due to its inertia, toward the rear against the bias of spring such that an arming ball 17 is released. The arming ball 17 serves for locking a primer pin 18 in an initial position such that upon release of the ball 17, the primer pin 18 which is constructed as a striker pin moves from its locked position due to its inertia, toward the rear and against a frictionsensitive primer element 19, whereby the latter is ignited. This primer element 19, in turn, ignites a pyrotechnical mixture provided thereafter, which, after burning through within a predetermined delay period, ignites a flash-sensitive detonator 21. The detonator 21, during its reaction, produces a sonic wave traveling, via the metallic components which are in contact with one another with a minimum amount of play, to the piezo crystal 11, generating at that point the electrical voltage required for igniting the detonator 7.

Conventional mixture compositions can be employed for the primer element 19, the delay line with the pyrotechnical mixture 20, and for the detonator 21, which are advantageously combined into a unit within a common casing 25. For example, a mixture of tetrazene and trinitroresorcinate can be used for the friction-sensitive primer element 19; a mixture of antimony, potassium chlorate, and lead chromate can be employed for the pyrotechnical mixture 20; and two series-connected compressed components of lead azide and penthrite can be utilized for the detonator 21, wherein the compressed unit of the flame-sensitive lead azide is disposed adjacent to the pyrotechnical mixture 20. The strength of the detonator 21 is dimensioned so that it produces, on the one hand, a sonic wave sufficient for triggering the piezoelectric fuze, but, on the other hand, is incapable of detonating the projectile directly, or even to cause damage to the projectile.

The embodiment illustrated in FIG. 2 corresponds to that of FIG. 1 with respect to the piezoelectric fuze, so that the same components have been provided with identical reference numerals. In this embodiment, the self-destructing device is constructed as a purely mechanical device and is disposed behind the piezoelectric fuze. However, it is also possible to arrange this self-destructing device beside the fuze, if this should its locked position. The thus-released striker pin 27 is set intomotion by means of a pretensioned compression spring 26. The striker pin 27 has lateral extending teeth or serrations 31, meshing with a gear wheel '28 which, due to the gear inhibitor 29, can rotate only in an inhibited manner. The construction of the gear inhibitor 29 is known, in principle, from German Offen- Iegungsschrift 1,927,911. As shown, the teeth 31 do not extend to the rear end of the striker pin 27, so that .the latter is accelerated without impediment by means of the compression spring 26 in the end portion of its forward movement. The striker pin impinges on the impact surface 32 of the abutment 13 of the piezoelectric fuze and thereby produces a sonic wave resulting in the response of the fuze. In front of the abutment 13, a percussion-sensitive detonator, not shown, may be arranged in opposition to the striker pin 27 in order to produce a stronger sonic wave. The abutment l3 rests on the housing 22 with the interposition of an elastic, electrically conductive member, e.g., one or several cup springs 33, to ensure that the abutment is in sufficient intimate contact with the piezo crystal 11.

In accordance with another embodiment of the present invention, an electronic delay line is illustrated in FIG. 3, wherein a capacitor C is charged in a conventional manner via two electrodes E and E The electrodes E, and E are disposed on the outer surface of the jacket of the impact explosive device in such a manner that, during the firing and/or dropping of the impact explosive device from a barrel or, for example, a bomb well, they are in contact for a sufficient length of time with energized counter electrodes disposed at that point. A capacitor C is charged in a predetermined manner via the resistor R by the capacitor C for such a period of time until the flashover voltage of a spark gap device F has been reached. Thereafter, the capacitor C is discharged via the spark gap device F and an electrically ignitable detonator D, which detonator produces the sonic wave required for triggering .the piezoelectric fuze arranged proximate thereto as in the FIG. 1 and FIG. 2 embodiments.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It should therefore be understood that within the scope of the appended claims, the invention may be sive device for triggering said sonicwave generating means after a predetermined period of delay to generate sonic waves for triggering of the piezoelectric fuze to effect detonation" of the explosive, whereby the selfdestructing apparatus is only indirectly effective on the.

explosive via the piezoelectricfuze of the impact detonating device.

2. Self-destructing apparatus according to claim 1, wherein said sonic generating means includes a detonatorand' said means for triggering said sonic wave generating means includes delay means for igniting said detonator after the predetermined period of delay, the sonic wave generated during the reaction of said detonator being transmitted to the piezoelectric fuze.

3. Self-destructing apparatus according to claim 2, wherein said delay means includes a pyrotechnical mixture having a predetermined burning time, said mixture being ignitable by primer element means, said means for triggering said sonic wave generating means further including movable primer pin means, locking means for retaining the primer pin means in a first position, said locking means being responsive to at least one of firing and. dropping of the impact-detonating explosive -device for releasing said primer pin means to permit the movement thereof, said primer pin means being movable from the first position which is spaced from said primer element means to contact said primer element means for igniting the pyrotechnical mixture.

4. Self-destructing apparatus according to claim 3, wherein said primer element means is one of an impact sensitive and friction sensitive primer element.

5. Self-destructing apparatus according to claim 3, wherein said locking means is responsive to inertial forces upon at least one of firing and dropping the impact-detonating explosive device for releasing said primer pin means.

6. Self-destructing apparatus according to claim 3, wherein said primer pin means is movable from the first position to contact the primer element means by inertial forces.

7. Self-destructing apparatus according to claim 3, wherein said primer pin means includes a primer pin and spring means biasing said primer pin toward said primer element means, said spring means moving said pin into contact with said primer element means upon release of said primer pin.

8. Self-destructing apparatus according to claim 1, wherein said sonic wave generating means includes striker pin means biased for movement against an impingement surface proximate to the piezoelectric fuze for producing the sonic waves, and said triggering means for said sonic wave generating means includes locking means for retaining said striker pin means in a first position spaced from the impringement surface and responsive to at least one of firing and dropping the impact-detonating explosion device for releasing said striker pin means for movement toward the impingement surface, and delay means for controlling the speed of movement of the striker pin during at least a portion of the path of movement between the first position and the impingement surface.

9. Self-destructing apparatus according to claim 8, wherein the delay means is an inhibiting gear meshing with serrations provided on said striker pin means along at least a portion of the surface thereof.

10. Self-destructing apparatus according to claim 8, wherein said sonic wavegenerating means includes a striker pin and a compression spring for biasing said striker pin in the direction toward the impingement surface.

ll. Self-destructing apparatus according to claim 8, wherein saidimpingement surface is an abutment surface of the piezoelectric fuze.

12. Self-destructing apparatus according to claim 8, wherein said impingement surface is a part of a percussion-sensitive detonator.

l3. Self-destructing apparatus according to claim 1, wherein said means for triggering said sonic wave gen erating means is electronic circuit means responsive to at least one of firing and dropping ofthe impactdetonating explosive device for providing an electrical triggering signal and said sonic wave generating means is an electrically ignitable detonator responsive to the electrical triggering signal.

14. Self-destructing apparatus according to claim 13, wherein the electronic circuit means includes first and second electrodes energized during at least one of the firing and dropping of the impact-detonating explosive device, a first capacitor having first and second terminals connected respectively to said first and second electrodes, a resistor having one terminal connected to the first terminal of said first capacitor, a second capacitor having a first terminal connected to the other terminal of said resistor and a second terminal connected to the second terminal of the first capacitor, a spark gap device having one terminal connected to the other terminal of said resistor and another terminal connected to one terminal of said electrically ignitable detonator, said detonator having another terminal connected to the second terminal of the second capacitor.

Claims

1. Self-destructing apparatus for impact-detonating explosive devices have a piezoelectric fuze responsive to sonic waves generated upon impact of the explosive device for the detonation of an explosive of the explosive device, the self-destructing apparatus comprising sonic wave generating means for generating sonic waves to trigger the piezoelectric fuze of the impactdetonating device, and means responsive to at least one of firing and dropping of the impact-detonating explosive device for triggering said sonic wave generating means after a predetermined period of delay to generate sonic waves for triggering of the piezoelectric fuze to effect detonation of the explosive, whereby the self-destructing apparatus is only indirectly effective on the explosive via the piezoelectric fuze of the impact detonating device.

2. Self-destructing apparatus according to claim 1, wherein said sonic generating means includes a detonator and said means for triggering said sonic wave generating means includes delay means for igniting said detonator after the predetermined period oF delay, the sonic wave generated during the reaction of said detonator being transmitted to the piezoelectric fuze.

3. Self-destructing apparatus according to claim 2, wherein said delay means includes a pyrotechnical mixture having a predetermined burning time, said mixture being ignitable by primer element means, said means for triggering said sonic wave generating means further including movable primer pin means, locking means for retaining the primer pin means in a first position, said locking means being responsive to at least one of firing and dropping of the impact-detonating explosive device for releasing said primer pin means to permit the movement thereof, said primer pin means being movable from the first position which is spaced from said primer element means to contact said primer element means for igniting the pyrotechnical mixture.

10. Self-destructing apparatus according to claim 8, wherein said sonic wave generating means includes a striker pin and a compression spring for biasing said striker pin in the direction toward the impingement surface.

11. Self-destructing apparatus according to claim 8, wherein said impingement surface is an abutment surface of the piezoelectric fuze.

13. Self-destructing apparatus according to claim 1, wherein said means for triggering said sonic wave generating means is electronic circuit means responsive to at least one of firing and dropping of the impact-detonating explosive device for providing an electrical triggering signal and said sonic wave generating means is an electrically ignitable detonator responsive to the electrical triggering signal.