US3630152A - Safety fuse with time and impact action - Google Patents

Abstract

A safety fuse, preferably usable for light grenades and shells having combined time and impact action, comprising a main piston containing elements of the ignition chain, said piston being displaced radially in a bore in the fuse casing by a driving spring, the time of this movement being prolonged by the vacuum created behind the ring-tightened piston, said vacuum being adjustable by leak holes having an arbitrary diameter. The fuse also contains a delay-composition-containing piston that is movable toward a fixed firing pin in a direction at an angle to the main piston. The delay piston has stopping means preventing its movement as long as the main piston has not reached its outward, fully armed position.

Description

Unite States Patent [72] Inventor Claes G. Arnell 3,078,802 2/1963 Sturrock 102/72 Torshalla, Sweden 3,313,236 4/l967 Lohmann 102/72 [2i] Appl. No. 36,170 3,371,608 3/1968 Webb lO2/72 [221 Ned May 1970 Primary Examiner-SamuelW. Engle [45] Patented 1971 Attorney-Munson & Fiddler [73] Assignee Forsvarets Fariksverk Eskilstuna, Sweden [32] Priority May 10, 1969 [33] Sweden [3l] 7026/69 [54] SAFETY FUSE TIME AND IMPACT ACTION ABSTRACT: A safetv fuse, preferably usable for light 4 Claims, 2 Drawing Figs grenades and shells having combined time and impactac tion, comprising a main piston containing elements of the ignition [52] U.S. Cl 102/72, chain, Said piston being displaced n in a bore in the f 102/78. 02/855 casing by a driving spring, the time of this movement being [51] B e v r 9/10 prolonged by the vacuum created behind the ring-tightened [50] Field of Search lO2/7l, 72, piston, Said vacuum being adjustabre by leak ho|e5 having an 78, 80v arbitrary diameter. The fuse also contains a delay-composition-containing piston that is movable toward a fixed firing pin {56] References Cited in a direction at an angle to the main piston. The delay piston UNITED STATES PATENTS has stopping means preventing its movement as long as the 2,005,053 6/1935 Schlafer 102/72 main piston has not reached its outward, fully armed position.

\l v v \I v v v 10 VVVVVL/ I V V IV 14 v v v .9 21 11 v V v V l l V V V V V V V 28 +4 I l l s," L 1 PATENTEDU228197I 3.630.152

INVENTOR l it ,4 CLAES G. ARNELL BY MUNSON & FIDDLER ATTORNEY SAFETY FUSE WITH TIME AND IMPACT ACTION Fuses for antiaircraft shells usually have an impact-sensitive circuit and a time-sensitive circuit that starts to work if the shell misses the target, resulting in self-destruction. Such fuses are known and are shown in US. Pat. Nos. 3,078,802 and 3,371,608. The hammer and firing pin units shown have a conically shaped bore containing a ball that transmits the retardation during impact to the hammer independent of the direction of impact such as by a ball and cone striker. US. Pat. No. 3,371,608 discloses a movable piston containing a delay composition that is thrown against a fixed firing pin when the projectile is brought to rotation during launch.

The present invention relates to a fuse of this type that has a piston provided with a special safety ball lock where the piston prevents the time circuit from not releasing until the piston has had sufficient time to move to a position where the firing pin in the impact circuit can reach the percussion cap and the booster. The fuse is especially suited for hand and smoke grenades and in particular grenades that can be attached to a rear driving part having stabilizing fins enabling the grenades to be launched by a small mortar.

The accompanying drawing discloses an embodiment of the invention and in which FIG. 1 shows a main section parallel with the axis of the piston and FIG. 2 shows a sectional view taken perpendicular to said axis.

In the drawing is shown a fuse casing 1 having a transverse bore 20 in which a main piston 7, surrounded and sealed by double O-rings, is fitted. The main piston 7 is preferably spring loaded by springs 30 and at one end is pierced by a hole containing a percussion cap. The cap is shown at Ma and a booster 14b and the cap are fully displaced in relation to a detonator when the piston 7 is pushed into the bore 20. The detonator is located in the center of a cover 11 that is sealed by an O-ring 21 and it covers a hole extending through the top wall of the casing. A TNT charge 10 is located above the cover 11 and the booster. Attached in the cover is a fixed firing pin 12 (FIG. 2) and a small permanent magnet 9 that holds a ball 9a that is capable of movement through a second hole in the top wall of the fuse casing. The ball 9a projects down into the upper widened part 8a of a radial bore in the piston 7 and said bore has a shoulder indicating the transition to a deeper, lower part 8b of the bore, said part 8b having the same diameter as the ball. The fuse casing I has, parallel to its axis, a hole containing another piston 13 (FIG. 2) that is spring loaded from below by spring 23 and is filled with a delay composition. This is a time circuit piston and it has a stopping flange 1311 that abuts against the jacket of the main piston 7 except when the piston 7 is in a fully drawn-out, armed position. The main piston 7 has at its underside, a recess 6b for the purpose of catching the firing pin before the piston 7 has had enough time to move out to fully armed position. The piston 7 also has in its externally projecting end, a hole for a transport-locking sprint 7a that prevents the piston from being pushed in unintentionally. Finally, the main piston 7 can have at least one small leak hole [7 for air going radially into the guiding hole for the main piston spring 30. The diameter of this hole regulates the duration of time for the outward arming movement of the piston together with the driving spring pressure.

Just under the main piston 7 there is a transversely directed hole 24 in the fuse casing for a locking pin 15, sealed with an O-ring and provided with a handle 25 directed at an angle. The end of the locking pin remote from the handle has a U- shaped recess 26 into which a movable firing pin 6 penetrates through a central guiding hole 27 in the bottom wall of the fuse casing. The firing pin 6 has a head and is shaped like a thum btack and it abuts directly against a relatively large metal ball 5 located in a conical, funnel-shaped bore provided with a permanent magnet 3 in its bottom in an adjacent bottom socket 2 that is threaded into the lower part of the fuse casing l. The socket 2 is externally threaded and can be equipped with either a protective cap or a short tube 4 or tail, with a driving charge and guiding fins underneath. In such a form the fuse can be used in wing shells for a small portable mortar with a range of a couple of hundred yards.

The operation of the fuse is substantially as follows:

If used in a handgrenade where both delay and impact action are desired the transport safety or spring 7a and the striker operation or locking pin 15 are both removed. The user then manually pushes the main piston 7 inwardly and when he later launches the grenade the ball 5 will overcome the attraction of the magnet 9 by this movement and the ball 5 falls down from the mouth into the bottom of the bore 8b in the main piston that is now free to move outwardly. This outward movement takes approximately from 1 to 1.5 seconds because of the strong suction or vacuum effect behind the piston 7 and the air will only leak in through the small hole 17. The piston is halted in the armed position by means of a small peg l6 positioned in the bottom wall of the casing l and which pin strikes against one end of a recess or shallow groove or slot 16a formed in the lower part of the piston 7. The flange 13a on the piston 13 that contains the delay composition, is now able to pass through a corresponding recess or cutaway part in the jacket of the main piston 7 with the result that the piston 13 strikes against the fixed striker pin 12 in the cover 11. The gages from the ignited delay composition will leak out through and along the groove or slot 16a because the O-ring at the right end of the piston will be outside the external wall of the fuse casing. After about 3 seconds a flashover to the percussion cap 14a will take place and the grenade will explode. If the grenade should make an impact before flashover from the outburned delay charge, the ball 5 will push the firing pin 6 into the percussion cap 14a but if the user happens to drop the grenade before launch, the piston will not have had enough time to move fully outwardly before impact with the result that the firing pin 6 will only enter the recess 6b, rendering the grenade harmless.

If the impact striker action is not desired, the striker safety, the locking pin 15, can be allowed to stay in the fuse at launching.

If the fuse is to be used in an ammunition round in a light mortar there is often no need for delayed action and the piston 13 can therefore be locked by any conventional lock. The transport and striker function safety (7a and 15 respectively) are removed as herein described and the grenade is introduced into the mortar barrel after the driving tail part has been threaded on. The gas pressure during launch will push the piston 7 inwardly with a force much greater than if one uses hand power and the ball 9a will be moved down into the bore 8b due to the linear acceleration. The piston does not start to move-outwardly until the grenade has left the barrel but after that there is obtained an unusually long trajectory safety. That is tosay, the grenade travels a long distance from the gun muzzlebefore the fuse is fully armed.

What is claimed is:

l. A safety fuse having combined delay and impact-type action and preferably adapted for a hand or smoke grenade, said fuse containing a firing pin actuated by an impact-sensitive body located in an adjacent bottom socket attached to a fuse casing and comprising a conical funnellike surface, a permanent magnet, a percussion cap, a booster charge, a transversely movable main piston in the casing, the booster charge being located in the piston, the piston being spring loaded and fitted in a bore in the casing, the casing having a second bore, the latter bore containing a spring-loaded, delay-compositioncontaining piston, a fixed firing pin toward which the latter piston is movable, the main piston when in a safety position being prevented from moving outwardly, a locking body preventing such movement, said locking body partly resting in a hollow in the casing, a magnet mounted in a cover over the hole and holding the locking body in place, the main piston having a radial bore into which the locking body partly projects, said bore having a narrowed portion, the main piston being pushed inwardly in the casing when the fuse is subjected to a small acceleration force such as occurs in launching, such movement causing release of the locking body and permitting the movement of the locking body into the narrowed portion of the radial bore, the delay composition piston having a flange that passes a cutaway part of the main piston when the latter has reached its fully armed position with the percussion capjust in front of the firing pin.

2. A safety fuse according to claim 1, wherein the main piston is sealed by O-rings and is provided with at least one leak hole extending into a guide hole for the piston-biasing spring on the rear side of the main piston in order to clear the subpressure created behind the main piston when it is being brought to armed position whereby, except for the piston spring pressure. the diameter of said leak hole determines the delay time of the arming movement.

3. A safety fuse according to claim 2, wherein the fuse casing has a hole on a level with an end of the firing pin for a sidewardly displaceable locking pin having a recess for the reception in safety position of the firing pin which has the lowest possible mass, said locking pin having a head abutting directly against the impact-sensitive body as long as the locking pin striker functions safety stays in.

4. A safety fuse according to claim 1, wherein a short tube with a hole, fins and driving charges can be attached to a bottom socket of the fuse and that the main piston is pushed inwardly by the pressure of the driving gases in the barrel of a mortar during launch.

Claims (4)

1. A safety fuse having combined delay and impact-type action and preferably adapted for a hand or smoke grenade, said fuse containing a firing pin actuated by an impact-sensitive body located in an adjacent bottom socket attached to a fuse casing and comprising a conical funnellike surface, a permanent magnet, a percussion cap, a booster charge, a transversely movable main piston in the casing, the booster charge being located in the piston, the piston being spring loaded and fitted in a bore in the casing, the casing having a second bore, the latter bore containing a spring-loaded, delay-composition-containing piston, a fixed firing pin toward which the latter piston is movable, the main piston when in a safety position being prevented from moving outwardly, a locking body preventing such movement, said locking body partly resting in a hollow in the casing, a magnet mounted in a cover over the hole and holding the locking body in place, the main piston having a radial bore into which the locking body partly projects, said bore having a narrowed portion, the main piston being pushed inwardly in the casing when the fuse is subjected to a small acceleration force such as occurs in launching, such movement causing release of the locking body and permitting the movement of the locking body into the narrowed portion of the radial bore, the delay composition piston having a flange that passes a cutaway part of the main piston when the latter has reached its fully armed position with the percussion cap just in front of the firing pin.

2. A safety fuse according to claim 1, wherein the main piston is sealed by O-rings and is provided with at least one leak hole extending into a guide hole for the piston-biasing spring on the rear side of the main piston in order to clear the subpressure created behind the main piston when it is being brought to armed position whereby, except for the piston spring pressure, the diameter of said leak hole determines the delay time of the arming movement.

3. A safety fuse according to claim 2, wherein the fuse casing has a hole on a level with an end of the firing pin for a sidewardly displaceable locking pin having a recess for the reception in safety position of the firing pin which has the lowest possible mass, said locking pin having a head abutting directly against the impact-sensitive body as long as the locking pin striker functions safety stays in.

4. A safety fuse according to claim 1, wherein a short tube with a hole, fins and driving charges can be attached to a bottom socket of the fuse and that the main piston is pushed inwardly by the pressure of the driving gases in the barrel of a mortar during launch.

Images