US3705552A

US3705552A - Pyrotechnic coiled delay cord assembly for hand grenade fuze

Info

Publication number: US3705552A
Application number: US113416A
Authority: US
Inventors: Russell E Lerman
Original assignee: US Department of Army
Current assignee: US Department of Army
Priority date: 1971-02-08
Filing date: 1971-02-08
Publication date: 1972-12-12
Anticipated expiration: 1989-12-12

Abstract

An improved hand grenade fuze that has an out-of-line metal sheathed pyrotechnic delay cord helically wound about a mandrel. The delay cord forms the threads of a delay-detonator assembly which cannot be screwed into the fuze head unless the delay cord is present thereby insuring the presence of the delay element.

Description

United States Patent Lerman 1 Dec. 12, 1972 [54] PYROTECHNIC COILED DELAY CORD FOREIGN PATENTS OR APPLICATIONS ASSEMBLY FOR HAND GRENADE 305,056 8/1916 Germany ..l02/64 FUZE 593,396 5/1925 France ..I02/64 [72] Inventor: Russell E. Lerman, Morris, NJ.

Primary Examiner-Verlin R. Pendegrass Asslgneei The United states Amen" as Attorney-Harry M. Saragovitz, Edward J. Kelly and represented by the Secretary of the H b B l Army [22] Filed: Feb. 8, 1971 [57] ABSTRACT An improved hand grenade fuze that has an out-of- [21] Appl' 113416 line metal sheathed pyrotechnic delay cord helically wound about a mandrel. The delay cord forms the 52 US. Cl ..l02/64, 102/85 threads of a delay-detonawr assembly which cannot 51] 1111. c1. ..F42b 27/00, F42c 9/10 be Screwed into the fuze head unless the delay cord is [58] Field of Search ..l02/64, 65 -72 85 thereby insuring the Presence of the delay ment. [56] Referen Cited 3 Claims, 8 Drawing Figures UNITED STATES PATENTS 2,687,093 8/1954 Botts .L.l02/24 R I 22 74 6 '9 27 I8 2a 42 21 46 4e l p aw: 50 I I t ,1: h I Io-1: I 2' '1 i l I a a l 3 o o I a I PATENTEUUEC 12 I972 SHEET 2 BF 2 INVENTOR.

BY! RUSSELLE. LERMAN FIG. 7

mmngnnzn 12 m2 3; 705 552 SHEET 1 0F 2 H INVENTOR) BY,- RUSSELL E. LERMAN PYROTECI-INIC COILED DELAY CORD ASSEMBLY FOR HAND GRENADE FUZE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to an improved delay fuze for hand grenades or similar explosive devices which require a fixed time delay after initiation of the fuze by a percussion primer.

Difficulty has been encountered with prior art grenades that utilized in line delay columns to initiate a detonator. One of the problems with the aforementioned prior art has been the danger that the user of the device has been subjected to when a delay column was inadvertently left out of the grenade during the manufacturing, or where the delay column was improperly constructed. In such instances the malfunction could result in a grenade failing premature rather than failing safe. The primer, in such cases where there is either a missing or defective delay column, directly activates the detonator without the required delay. The current stateof-the art manufacture of delay column requires the pressing of pyrotechnic powder in metal tubes at controlled consolidation pressures. Since this is a difficult operation to always perform because some delay columns are produced which have cracks in the powder material, or where voids are caused by powdering. If

such a defective delay column is not detected in the initial inspection, the grenade will expose the user to the possibility of premature explosion or have erratic time delays. In order to overcome the aforementioned dangers expensive inspection procedures such as x-ray photography are required to eliminate those devices with either missing or defective delay columns.

Another problem encountered with the in-line primer, delay column, detonator construction is the requirement that the delay column be loaded through the top of the fuze head. This top loading operation requires the use of a separate primer assembly which must be assembled into the fuze head on top of the delay column after the latter has been filled.

Additional difficulty encountered with present grenades has been due to the need for high energy primers to reliably initiate the pyrotechnic delay column. The use of high energy primers has resulted in additional malfunction caused by blown primers, and primer assembly and cracked fuze housings.

Pyrotechnic columns whether in the pressed or extruded metal sheathed form tend to burn more accurately as the burning rate is increased. Prior art pressed delay columns are limited in their accuracy because of the limited length of column that can be incorporated in the in-line fuze design. In the present invention this limitation in length is overcome by making the delay column in the form of a coil and using pyrotechnic material having a faster and more accurate burning rate. The extruded metal cord containing pyrotechnic mixtures may be obtained commercially in a variety of burning rates.

SUMMARY OF THE INVENTION The present invention relates to a hand grenade fuze which will prevent premature detonation due to inadpyrotechnic material which can be activated by a lower energy primer.

One of the objects of this invention is to provide a hand grenade which is cheaper to manufacture because it requires less inspection and fewer parts.

Another object of this invention is to insure that in the event of a malfunction after the grenade is activated that it will fail safe rather than fail premature.

Another object of this invention is to eliminate the need for a separate primer holder assembly.

Another object of this invention is to reduce the erratic times for delay which occur in prior art in-line delay column type fuzes.

Another object of this invention is to reduce the number of malfunctions occurring in hand grenades due to blown primers and/or cracked housings by the use of a lower energy primer.

Another object of this invention is to eliminate inad vertently omitted delay columns by making it impossible to assemble the fuze if the delay column is not present.

A further object of this invention is to eliminate the need to percent x-ray assembled grenades in order to detect missing delay columns.

For better understanding of the present invention, together with other and further objects thereof,

reference is made to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional elevation of a grenade fuze assembly, striking means, and safety means according to the invention.

FIG. 2 is an elevational view of the mandrel illustrated in FIG. 1.

FIG. 3 is a sectional view of the mandrel taken along line 33 in FIG. 2.

FIG. 4 is an elevational view of the mandrelpyrotechnic delay cord sub-assembly as illustrated in FIG. 1.

FIG. 5 is a sectional view of the mandrel-pyrotechnic delay cord sub-assembly taken along line 5-5 in FIG. 4.

FIG. 6 is an enlarged partial sectional view of the lower right hand comer of the mandrel-pyrotechnic delay cord sub-assembly as illustrated in FIG. 5.

FIG. 7 is an elevational view, and partial sectional view of the combined detonator-delay assembly consisting of a mandrel-pyrotechnic delay cord sub-assembly crimped to a detonator sub-assembly as illustrated in FIG. 1.

FIG. 8 is a plan view of the combined detonatordelay assembly of the mandrel-pyrotechnic delay cord sub-assembly and the detonator sub-assembly, taken along line 8-8 as illustrated in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG. 1, a hollow fuze head has a first central bore 11, axially aligned therewith and connected thereto is a second primer bore 12 of smaller diameter; flash hole 13 of smaller diameter than primer bore 12 is concentrically connected therewith; primer bore 12 is intermediate to the first central bore 11 and flash hole 13. A threaded bore 14 is axially aligned with the flash hole 13; flash hole 13 is intermediate to the primer bore 12 and the threaded bore 14. Concentrically located with the lower half of the threaded bore 14 is a threaded boss 20. The complete fuze assembly as illustrated in FIG. 1 is screwed to a grenade housing 21 by means of the threaded boss 20, the grenade housing contains an explosive charge (not shown).

A percussion primer 22 is firmly held in primer bore 12 by a lip 24 produced by a crimping tool (not shown) which extrudes a portion of the fuze head material immediately adjacent to the primer bore over and circumambient the outer periphery of the primer 22.

A safety lever 36 has an arcuate end 17 which is positioned under pivot pin 18, the middle section of the safety lever 36 is held firmly attached to the fuze head 10 by a striker retaining safety pin 32 which is slidably positioned in a fuze pin aperture 30 and a concentrically positioned safety lever pin aperture 31. The combination of the pivot pin 18 restraint upon the arcuate extension 17 and the striker retaining pin 32 restraint upon the striker lever 34 prevents the safety lever 36 from being inadvertently moved.

A striker lever 34 is pivotally held by a striker pivot pin 28, the striker pivot pin is firmly held by the interference fit between a striker pivot pin aperture 27 and the striker pivot pin 28. The striker pivot pin aperture 27 horizontally located in the fuze head 10, has its axis perpendicular to the longitudinal axis of the grenade fuze assembly. A striker spring 26 is also supported by the striker pivot pin 28 and spring loaded to exert a rotational force against the striker lever 34 when the safety lever 36 is intentionally released. Removal of the safety pin 32 and release of the safety lever 36 by the user will permit the spring loaded striker lever 34 to rotate about striker pivot pin 28, throwing off and separating safety lever 36 from the fuze head 10, permitting striker lever 34 to forcibly impact upon the percussion primer 22.

A cylindrical mandrel 38 as shown in FIG. 2 and 3 has a helically cut mandrel thread 40 in its outer periphery.

A metallic sheath pyrotechnic delay cord 42 is tightly wound in the mandrel helical threads 40 to form a mandrel-delay cord sub-assembly as shown in FIGS. 4 and 5. The enlarged sectional view of FIG. 6 shows the mandrel 38 helically wound with an aluminum metal sheath 43 surrounding an inner pyrotechnic delay composition having a burning rate of approximately 2 inches per second as a core 44.

FIGS. 7 & 8 show a detonator-delay assembly wherein the mandrel-pyrotechnic delay cord sub-assembly as illustrated in FIGS. 4, 5 and 6 is partially inserted into an aluminum detonator case 46; the detonator case 46 material is crimped over the convoluted delay cord 42 and mandrel 38 so as to leave a safety gap 48 intermediate to the lower end of the mandrel 38 and the top of a first detonating material 50 of lead styphnate, the balance of the detonator case is composed of a second detonating layer 51 of lead azide, and a third detonating layer 52 of cyclonite; The aforementioned detonator-delay assembly is screwed into the threaded bore 14 using the partially projecting delay cord 42 of the mandrel-pyrotechnic delay cord assembly as the mating threads. The presence of the crimped detonator case 46 about the mandrelpyrotechnic sub-assembly acts as a predetermined stop for the distance that the mandrel-delay assembly will travel into threaded bore 14, a gas chamber 15 is provided for the expanding gases generated by the primer 12 after initiation by striker lever 34. The mandreldelay assembly prevents the direct initiation of the detonator by the primer other than through the delay cord.

From the above description it will be evident that the present invention insures that a delay cord will be present when the fuze is assembled, because the detonator cannot be attached to the fuze head without the delay cord acting as the mating thread. This improved fuze eliminates the need for expensive x-ray inspection techniques, and permits the fuze to fail safe rather than fail premature. This invention permits the use of lower energy primers because the aforementioned design allows the delay element to be screwed up to the output end of the primer thereby reducing the probability of blown primers, cracked fuze heads and duds.

I wish it to be understood that I do not desire to be limited to the exact detail of construction shown and described for obvious modifications will occur to a person skilled in the art.

What is claimed is:

1. An improved hand grenade fuze of the type wherein said fuze has means for holding a percussion primer, means for channeling gases from said primer to a gas chamber, means for operatively striking said percussion primer, safety means for preventing said striking means from operating inadvertently, means for attaching said fuze to a grenade body, and a detonating means for actuating a main explosive charge, wherein the improvement comprises:

a fuze head having'a threaded bore communicating with said primer;

a pyrotechnic delay cord;

a solid cylindrical mandrel having a peripheral helical thread on its longitudinal surface extending from one end of said mandrel to the other end;

a mandrel-delay cord sub-assembly consisting of said delay cord wound upon said peripheral helical thread;

a detonator-delay assembly having said detonating means attached to said mandrel-delay cord sub-assembly so that said mandrel-delay cord sub-assembly partially protrudes out of said detonating means providing a screw like extention, said delay cord interfitably engages said threaded bore when said detonator-delay assembly is screwed into said threaded bore, said detonating means having a shoulder which permits said mandrel-delay cord assembly to be screwed into said threaded bore for a predetermined fixed distance.

2. An improved hand grenade fuze as recited in claim 1 wherein the pyrotechnic delay cord comprises:

delay core; and

a metal sheath longitudinally circumambient to said delay core composition having open ends exposing said delay core to said primer on said one end of said mandrel, and exposing said delay core to said detonator on said other end of said mandrel.

3. An improved hand grenade fuze as described in claim 2 wherein said metal sheath is aluminum.

Claims

1. An improved hand grenade fuze of the type wherein said fuze has means for holding a percussion primer, means for channeling gases from said primer to a gas chamber, meanS for operatively striking said percussion primer, safety means for preventing said striking means from operating inadvertently, means for attaching said fuze to a grenade body, and a detonating means for actuating a main explosive charge, wherein the improvement comprises: a fuze head having a threaded bore communicating with said primer; a pyrotechnic delay cord; a solid cylindrical mandrel having a peripheral helical thread on its longitudinal surface extending from one end of said mandrel to the other end; a mandrel-delay cord sub-assembly consisting of said delay cord wound upon said peripheral helical thread; a detonator-delay assembly having said detonating means attached to said mandrel-delay cord sub-assembly so that said mandreldelay cord sub-assembly partially protrudes out of said detonating means providing a screw like extention, said delay cord interfitably engages said threaded bore when said detonator-delay assembly is screwed into said threaded bore, said detonating means having a shoulder which permits said mandrel-delay cord assembly to be screwed into said threaded bore for a predetermined fixed distance.

2. An improved hand grenade fuze as recited in claim 1 wherein the pyrotechnic delay cord comprises: delay core; and a metal sheath longitudinally circumambient to said delay core composition having open ends exposing said delay core to said primer on said one end of said mandrel, and exposing said delay core to said detonator on said other end of said mandrel.