GB2150673A

GB2150673A - Impact fuse

Info

Publication number: GB2150673A
Application number: GB08429837A
Authority: GB
Inventors: Hans Assmann
Original assignee: Oregon Etablissements fuer Patentverwertung
Current assignee: Oregon Etablissements fuer Patentverwertung
Priority date: 1983-11-29
Filing date: 1984-11-26
Publication date: 1985-07-03
Also published as: BE901152A; DE3441556A1; ZA849152B; GB8429837D0; FR2555733A1; IL73565A0

Abstract

In an impact fuse comprising a fixed (9) and a displaceable fuse portion (14) for self-destruction ammunition which is to be fired from a barrel and which includes a pyrotechnic bore-safe safety means, the safety means includes a fusible member (26) and pyrotechnic compositions (6) disposed in a carrier (7) which is concentric to the axis of a projectile of the ammunition. One of the pyrotechnic compositions which is disposed in the region of the fusible member is in the form of a heating composition (24) and another directly adjoining pyrotechnic composition is formed as a delay composition (25). The displaceable impact fuse portion (14) has a safety sleeve (17) which is at least partially pushed onto the carrier (7) and is connected to the carrier (7) by way of the fusible member (26). The fuse is initiated by the propellant gases from charge 20 deflecting a diaphragm 12 and causing a pin 12 to strike a primer 10. When the fusible member 26 has been melted by the heat 2 from the charge 24, the striker 15 moves forward owing to inertia and comes to rest against a diaphragm 29, whence it is thrown against the fixed fuse part 9 either upon impact with a target or by the propellant gases from a charge 16 that is ignited by the delay composition 25. <IMAGE>

Description

SPECIFICATION Impact fuse This invention relates to an impact fuse for ammunition which is to be fired from a barrel, having impact fuse portion, a displaceable impact fuse portion, pyrotechnic bore-safe safety means and self-destruction means, wherein the bore-safe safety means includes a fusible member and pyrotechnic compositions, one of which is formed as a heating composition located in the region of the fusible member and another of which is formed as a delay composition, are disposed in a carrier which is locatable concentrically with respect to the axis of a projectile of the ammunition.

An impact fuse of such a kind is to be found for example in German patent specification No. 1 101 225. In that fuse, a needlelike pin which is provided as the displaceable impact fuse portion is fitted into the carrier of the pyrotechnic pellets or compositions, the entire carrier being longitudinally displaceable on the centre line of the projectile. The fusible member which is disposed at the other end of the carrier is formed by an insert which serves as a spacer member and which axially fixes the carrier in a secured position, and prevents the needle-like pin from coming out of a radially displaceable blocking member which is disposed between the two portions of the impact fuse.As soon as the fusible insert has melted after firing of the heating pellet or composition, the carrier becomes axially displaceable so that the needle-like pin comes out of the blocking member, and the blocking member moves radiaily due to centrifugal force or by spring assistance so that, upon impact, the needle-like pin can impact onto the exposed detonator. Upon firing, a firing pellet or composition which is disposed between the heating composition and a delay composition is acted upon. The firing composition then simultaneously fires the heating composition and the delay composition- which results in the needle-like pin coming into operation even without impact of the projectile, after the set delay time.

In such construction, destruction of the fusible insert does not directly result in release of the displaceable impact fuse portion and therefore does not represent a direct bore-safe safety means, but only results in release of the actual bore-safe safety blocking member which in further succession releases the displaceable impact fuse portion.

In a fuse for hand or throwing grenades, which is described in German patent specification No. 710 622, fusible inserts also serve as a precautionary stage for blocking elements which prevent-relative movement between the two portions of the impact fuse. The fusible insert fixes a safety sleeve which is displaceable under the action of a spring and which is disposed around the fixed impact fuse portion, and blocks a ball locking arrangement. The heat which is produced by a delay composition destroys the fusible insert and due to the safety sleeve being displaced, the balls are released and in turn release the displaceable impact fuse portion.

There is thus a need for a generally improved impact fuse in which destruction of the fusible insert results in direct release of the axially displaceable impact fuse portion so that there is no need for additional blocking members and the disadvantageous design features which they involve.

According to the present invention there is provided an impact fuse for ammunition which is to be fired from a barrel, having a fixed impact fuse portion, a displaceable impact fuse portion, pyrotechnic bore-safe safety means and self-destruction means, wherein the bore-safe safety means includes a fusible member and pyrotechnic compositions, one of which is formed as a heating composition located in the region of the fusible member and another of which is formed as a delay composition, are disposed in a carrier which is locatable concentrically with respect to the axis of a projectile of the ammunition, wherein the displaceable impact fuse portion has a safety sleeve which is at least partially pushed onto the carrier which is connectible to a body of the ammunition, and is connected to the carrier by way of the fusible member, and wherein the delay composition directly adjoins the heating composition in the carrier at the side of the heating composition remote from the firing side of the heating composition.

The direct connection of a axially displaceable safety sleeve as a carrier for a delay composition and a detonator of a hand grenade fuse having a stationary fuse portion is to be found in German patent specification No. 1 5 78 458. In the fuse described in the latter patent, after the destruction of the fusible member which is formed for example by one or more solder joints, the sleeve which carries the pyrotechnic compositions or pellets is moved under the force of a spring into an active position in which the detonator can fire a secondary charge. In such arrangement, the fusible member is heated by the heat which is given off by the delay charge when it is fired.

Moreover in such arrangement, the fusible member represents a throwing or launching safety device which is to be equated to a bore-safe safety means, to prevent premature detonation of the hand grenade as the fusible member holds the detonator at an inoperative distance from the secondary charge. However, the pyrotechnic compositions do not include a heating composition which serves exclusively for the purposes of developing heat so that, as an effect which is extremely advantageous with a hand grenade, in the event of failure of the delay charge, the grenade is inoperative or dud so that it can be saved and rendered harmless substantially without danger.

In the impact fuse according to the present invention, for the purposes of destroying the fusible member, the fuse has its own heating composition which can be easily ignited so that release of the safety sleeve from the carrier does not depend on the firability of the delay composition which in any case is required only in the event of failure of the impact fuse. The active position of the displaceable impact fuse portion which is formed either by the detonator or by the striker, however, is also attained in the event of failure of the delay composition. Thus, the heating composition is fired first in the firing chain of the pyrotechnic compositions contained in the carrier, and thereby destroys the fusible member which in particular is formed by at least one solder joint comprising a low temperature solder between the safety sleeve and a portion of the carrier.Therefore, by virtue of inertia, the impact fuse portion together with the safety sleeve can move forwardly into the active position as the projectile is slowed down by the air resistance to which the impact fuse portion in the interior of the projectile is obviously not exposed. Completely independently thereof, the heating composition fires the delay composition which is so set that it is only after impact of the projectile that the delay composition would trigger off detonation thereof, if it has not already occurred.

Thus, the fusible member directly ties one of the two impact fuse portions to an immovable mass and, after setting that connection, produces the second operative capability of the impact fuse without further intermediate or safety members.

Preferably the fusible member has a softening or melting time which, in relation to the initial speed of the projectile, provides a boresafe safety configuration for at least the first 30 metres and at most the first 50 metres of the trajectory. In order to feed the heat developed by the heating composition to the fusible member with minimum losses, preferably the portion of the carrier which is connected to the safety sleeve via the fusible member is in the form of an annular web which is axially defined by annular grooves formed on both sides in the wall of the carrier.

Advantageously the safety sleeve is fitted into an annular space which is defined between a tapered portion of the carrier, which accommodates the pyrotechnic compositions, and an outer guide sleeve.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 is a longitudinal sectional view of the impact fuse of the invention fitted in a 40 mm explosive fragmentation grenade or shell with cartridge; and Figure 2 is a view to an enlarged scale of a detail of Figure 1.

An explosive fragmentation grenade or shell shown in Figures 1 and 2 of the accompanying drawing comprises a multi-part projectile casing made up of a front portion 1 which is made for example from steel, a central portion 2 made for example of aluminium and a base portion 3 also made for example of aluminium. Also provided in the region of the front portion 1 and the central portion 2 is a fragmentation casing 4 formed by steel balls embedded in plastics material.

Disposed in the interior of the explosive fragmentation grenade or shell is a highly explosive charge 5 which is disposed around a sleeve 8 made for example from plastics material. The sleeve 8 is fitted onto a carrier 7 which is made for example from brass and which contains pyrotechnic compositions 6, while formed between the sleeve 8 and the carrier 7 over the major part of the common length thereof is an annular space into which the safety sleeve 1 7 which is described hereinafter is fitted. The firing mechanism for the pyrotechnic compositions 6 comprises a primer capsule or pellet 10 and a primer member 11.

The primer member 11 is fixed on a deformable membrane 1 2 of metal, for example copper, which is fixed in the base portion 3 of the grenade or shell by a clamping screw 1 3.

The pellet 10 is fitted into the lower opening of the tubular carrier 7 which is screwed into the base portion 3 from the interior.

A projector or firing tube 1 8 made for example of aluminium is provided for firing the grenade, the body of the grenade being fitted into the projector 18. A propellant charge cartridge 1 9 with a propellant charge 20 and a propellant charge primer pellet 21 is screwed in the bottom of the projector 1 8. For the discharge of propellant charge gases from the propellant charge 20 into a cavity 22 inside the projector 18, the propellant charge cartridge 1 9 has bores or passages 23.

The propellant charge 20 is fired by impacting of the propellant charge firing primer pellet 21; the striker pin (not shown) which is required for that purpose being part of the equipment of the projector 18. The propellant charge gases pass into the cavity 22 where they build up a pressure which both drives the grenade out of the projector 1 8 and deforms the deformable membrane 12 of the firing mechanism for the pyrotechnic compositions 6 of the grenade. When such deformation of the diaphragm 1 2 occurs, the primer member or firing needle 11 strikes against the primer cartridge or pellet 10 in the carrier 7. The resulting flash from the primer pellet 10 passes into the interior of the carrier 7 and fires a heating composition 24 as the first pyrotechnic composition.The heating composition 24 burns, giving out the maximum amount of heat in the minimum possible time, and transmits the heat in particular to the surrounding portion 28 of the carrier 7. The portion -28 is connected to the end of the above-mentioned safety sleeve 17, which is towards the base portion of the projectile, via a fusible or melting member 26 which is formed by one or more solder joints distributed around the periphery of the portion 28.

The fusible member 26 softens or is destroyed and thereby releases the sleeve 1 7. In order for the heat produced by the heating composition 24 to be transmitted with minimum losses to the fusible member 26 which for example is a silver solder or another lowtemperature solder (suitable melting temperature at about 120"C), the portion 28 of the carrier 7 is in the form of an annular web which extends between two annular grooves 27 adjoining same on both sides in the axial direction. In the region of the annular grooves 27 of the carrier 7, the wall thickness thereof is reduced as much as possible in order to keep the flow of heat in the axial direction at a low level, so that the required effect can be achieved with a short column of heating composition, which is long enough to cover approximately the full height of annular web.

At least one delay composition 25 is pressed into the carrier 7, directly adjoining the heating composition 24. Firing of the delay composition 25 is effected by the heating composition 24. Therefore, the delay composition 25 adjoins the heating composition 24, in the firing chain, at the side of the composition 24 which is remote from the side at which the heating composition 24 is fired.

The duration of burning of the delay composition 25 is slightly more than the duration of flight of the projectile (for example 9 seconds in relation to 8 seconds). In turn, an additional charge 16 adjoins the delay composition 25. This charge 1 6 would be fired after termination of the flight of the projectile, if the projectile has not already been detonated upon impact.

Disposed in the sleeve 17, which is axially displaceable in the sleeve 8 after it has been released, is an impact fuse portion 14 which is axially displaceable with the safety sleeve 1 7 and which, in the illustrated construction, forms a striker and carries a firing needle member 1 5 which projects out of the front end of the safety sleeve 1 7 and which, upon impact of the projectile, fires the detonator charge which is disposed in the front portion 1, in the form of the fixed impact fuse portion 9. It will be appreciated that the two portions 9 and 14 may also be interchanged, that is to say the detonator charge may be fitted into the sleeve 1 7 and the member 1 5 may be fitted into the front portion 1.

The safety sleeve 17, when released, with the displaceable fuse portion 14, is not retarded in the sleeve 8 due to the external air resistance during the flight of the projectile, but the projectile itself is. By virtue of its inertia in the movement of the projectile therefore, the safety sleeve 1 7 with the fuse portion 14 moves forwardly into the active impact position while the projectile is in flight. A membrane 29 preferably is provided at the front end of the sleeve, so that the forward movement of the fuse portion 14 comes to a halt while it is still at a small distance from the fixed fuse portion 9. The membrane 29 which can be easily destroyed is then penetrated upon impact by the displaceable fuse portion 14 so that contact between the two fuse portions 9, 14 occurs with a force sufficient to ensure that detonation occurs.

If impact of the projectile is too soft to set off the detonator charge, the projectile is still destroyed as the delay composition 25 which is fired by the heating composition 24 fires the charge 16. The charge 1 6 preferably is in the form of a propellant charge which drives the displaceable fuse portion 14 and thus causes it to impact onto the fixed fuse portion 9 with the necessary force. However, the charge 1 6 itself could also form a detonator charge so that, in the event of failure of the impact fuse, the explosive charge 5 of the projectile is fired by the charge 1 6.

The displaceable fuse portion 14 may not only be fitted into the safety sleeve 1 7 which preferably is made of brass, as illustrated, but it may be formed integrally therewith or it may also have a peripheral bead or crease into which the sleeve 1 7 is pressed, the sleeve 1 7 being shorter in that case.

Claims

1. An impact fuse for ammunition which is to be fired from a barrel, having a fixed impact fuse portion, a displaceable impact fuse portion, pyrotechnic bore-safe safety means and self-destruction means, wherein the bore-safe safety means includes a fusible member and pyrotechnic compositions, one of which is formed as a heating composition located in the region of the fusible member and another of which is formed as a delay composition, are disposed in a carrier which is locatable concentrically with respect to the axis of a projectile of the ammunition, wherein the displaceable impact fuse portion has a safety sleeve which is at least partially pushed onto the carrier which is connectible to a body of the ammunition, and is connected to the carrier by way of the fusible member, and wherein the delay composition directly adjoins the heating composition of the carrier at the side of the heating composition remote from the firing side of the heating composition.

2. An impact fuse according to claim 1, wherein the displaceable impact fuse portion is fitted into the safety sleeve which projects beyond it on the carrier side.

3. An impact fuse according to claim 1, wherein the fusible member has at least one solder junction, comprising a low temperature solder, between the safety sleeve and a portion of the carrier.

4. An impact fuse according to claim 3, wherein said portion of the carrier which is connected to the safety sleeve via the fusible member is in the form of an annular web which is axially defined by annular grooves formed on both sides in the wall of the carrier.

5. An impact fuse according to claim 1, wherein the safety sleeve is fitted into an annular space which is defined between a tapered portion of the carrier, which accommodates the pyrotechnic compositions, and an outer guide sleeve.

6. An impact fuse according to claim 1, wherein disposed adjoining the delay composition is an additional charge formed as a propellant charge.

7. An impact fuse for ammunition which is to be fired from a barrel, substantially as hereinbefore described with reference to the accompanying drawings.

8. A round of ammunition having an impact fuse according to any one of claims 1 to 7.