GB2223294A - Impact indicator - Google Patents

Abstract

An impact indicator for an artillery training shell comprises a body (10) adapted to be received in a recess (4) in the rear end of the shell and having a cavity (16) in its rear end face, the cavity (16) containing an indicator device (21, 22) and a quantity of explosive material (41) capable of ejecting the indicator device (21, 22) from the body (10). The indicator device can comprise a body of pyrotechnic material (21), for example a material capable of generating a flash and/or smoke visible at a considerable distance, and may be contained in an aluminum capsule (22). The pyrotechnic material (21) may be ignited by the explosive charge (41) on ejection. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO ARTILLERY TRAINING AMMUNITION This invention relates to artillery training ammunition, and in particular is concerned with an impact indicator to be incorporated in such ammunition.

In use of training ammunition it is an important consideration that the point of impact should be identifiable by the user so that he has an indication of how closely he has approached the target. In the instance of artillery training ammunition this objective is very difficult to meet, because the point of impact is normally at a considerable distance, and because the shell will normally possess considerable terminal velocity and kinetic energy, so that on impact with the ground it becomes buried to a substantial depth in a very short space of time.

A known design of full bore training shell is provided with a nose fuze to initiate a smoke and flash pellet on impact to give a smoke and flash signature through holes in the shell body. Such a design is ineffective in the common situation where the shell impacts soft ground, because the shell is buried before the smoke and flash pellet can take effect. The performance would deteriorate still further in snow.

The present invention seeks to mitigate this problem.

Accordingly the present invention provides an impact indicator for an artillery training shell comprising a body adapted to be received in a recess in the rear end of the shell, said body having a cavity in its rear end face, and said cavity containing an indicator device and a quantity of explosive material capable of ejecting the indicator device from the body.

Most conveniently the indicator device includes a quantity of a pyrotechnic composition.

Preferably the impact indicator comprises a fuze capable of detecting proximity of or impact with a target and initiating the explosive material in response thereto.

Preferably also the impact indicator includes a safety and arming unit for preventing the fuze from initiating the explosive material except after having been fired from a gun and travelling a predetermined distance from the gun.

Advantageously the rear end of the cavity is sealed by a blow out plug resting on a shoulder formed around the cavity.

According to another aspect of the invention there is provided an artillery training shell having a recess in its end face wherein there is received an impact indicator in accordance with the invention.

The invention will now be described by way of example only with reference to the accompanying drawings, of which Figure 1 is a sectional view of an artillery training shell adapted to receive an impact indicator in accordance with the invention, Figure 2 is a sectional view of an impact indicator in accordance with the invention, suitable for use with the shell of Figure 1, Figure 3 is a sectional part view of the impact indicator shown in Fig 2, showing further detail, Figure 4 is a plan view of the safety and arming unit forming a part of the impact indicator of Figure 2.

As shown in Figure 1, an artillery training shell comprises a hollow body 1 of increased thickness so as to provide equivalent mass to a high-explosive filled shell with the same external profile. The body 1 is provided with a nose plug 2 representing a normal fuze which it replaces, and a driving band 3. In its rear end the body 1 is provided with a stepped cylindrical cavity 7 having a large diameter rear section 4 and a smaller diameter section 5 forward thereof, a shoulder 6 being thus formed therebetween. The rearmost part of the section 4 has an internally screw-threaded portion 8.

As shown in Figure 2, an impact indicator has a body 10 of stepped cylindrical form having a large diameter section 11 and a small diameter section 12, separated by a shoulder 13. The rearmost part of the section 11 has an externally screw threaded portion 14. The screw threads 8 and 14 are complementary, and the dimensions of the body 10 are such that the body 10 is fully and closely received in the recess 4 when the screw threads 8 and 14 are fully engaged with the shoulders 6, 13 in abutment. A sealing ring 15 is received in a groove in the section 11, and seals against the surface of the section 4 to prevent the ingress of dirt, moisture, etc. The body 11 is provided with holes 19 in its rear end face for the purpose of fitting an assembly tool. The body 10 has a stepped cylindrical cavity 16 open to its rear end.

The outermost portion of the cavity 16 contains a steel disc 17 which is provided with a sealing ring 18 for sealing against the wall of the cavity 16.

Rearwardly of the disc 17 and serving to hold it in place is a screwed ring 20.

Alternatively the body 11 could be formed to suit the same purpose. The disc 17 rests against a shoulder of the cavity 15 to transmit the loading of the propellant gases on launching the shell from a gun.

Forward of the disc 17 and closely received within a reduced diameter part of the cavity 16 is a cylindrical aluminium capsule 22 containing a quantity of pyrotechnic material 21. The pyrotechnic material can be any suitable material capable of generating a signal visible at a considerable distance, consisting for example of a flash and/or smoke. Alternatively a solid pellet of pyrotechnic material can be used instead of the aluminium capsule 22, or some other means for generating a visular or non-visible signal which can be detected at a distance such as a chaff dispenser. Forward of the capsule is a metal bulkhead 23 retained by a circlip 24. The metal bulkhead 23 has a centre section 25 of reduced and specified thickness in order to control its explosive sealing and transfer properties.

Forward of the bulkhead 23 is an inertial mass whose forward motion is controlled by a spring 27.

The inertial mass consists of an assembly comprising, a magazine 28 containing a variable quantity of explosive 41 of variable power and composition, a delayed arming unit 29 of a type well known and a spring-loaded detent 30 which interferes with a shutter 31 of the delayed arming unit. A striker 32 is secured in the body 10 such that it aligns with the longitudinal axis of the assembly.

The delayed arming unit 29 serves to retain an initiator 33 in a safe out of line position until the shell has been fired from a specified gun and travelled a specified distance.

As shown in Figure 3, the detent 30 is slideable in a longitudinal bore 34 in the magazine 28, and is urged forwardly to the position shown by a spring 35 which is captive between a cap 36 and the detent 30.

On firing the shell 1 from a gun having a rifled barrel the set back moves the detent 30 rearwardly in its bore against the action of the spring 35. At the same time the spin imparted to the shell 1 by the rifling results in a radially outward centrifugal force on a plunger 37, which is now free to move outwardly against the action of a spring 38 under this centrifugal force. The way is thus cleared for the shutter 31 to rotate around its pivot and thus line up the indicator 33 with the striker 32.

Movement of the shutter 31 is controlled by an escapement wheel 38 and pallet 39 via a toothed segment 40 which is secured to the shutter 31. This mechanism prevents the shutter 31 rotating to an armed position until a specified time has elapsed.

Such a time is controlled by the geometry and intertia of the mechanism, and by the spin rate of the shell.

When the shell reaches its target,, even if it strikes obliquely, the inertial mass moves forward relative to the body 10 causing the striker 32 to impinge upon and initiate the detonator 33, thus causing the explosive 41 in the magazine 28 to be disrupted which transfers energy through the bulkhead 25 to ignite the pyrotechnic composition 21 in its container 22. By this stage the shell may well have buried itself quite deeply in a soft target such as snow or soft ground. However , the pressure and shockwave generated by the explosive 41 and pyrotechnic 21 is sufficient to displace the disc 17 and the blow out plug 20, and to propel the burning pyrotechnic rearwardly from the body 10 and upwardly to emerge from any crater in wich the shell 1 may be buried. The pyrotechnic composition 21 thus continues to burn above the surface at the target despite the shell having become buried in the ground, to provide a clear visible signal comprising a flash and copious smoke.

Claims (7)

1. An impact indicator for an artillery training shell comprising a body adapted to be received in a recess in the rear end of the shell, said body having a cavity in its rear end face, and said cavity containing an indicator device and a quantity of explosive material capable of ejecting the indicator device from the body.

2. An impact indicator according to claim 1 wherein the indicator device includes a quantity of a pyrotechnic composition.

3. An impact indicator according to claim 1 or claim 2 wherein the impact indicator comprises a fuze capable of detecting proximity of or impact with a target and initiating the explosive material in response thereto.

4. An impact indicator according to any one preceeding claim and including a safety and arming unit for preventing the fuze from initiating the explosive material except after having been fired from a gun and travelling a predetermined distance from the gun.

5. An impact indicator according to any one proceding claim wherein the rear end of the cavity is sealed by a blow out plug resting on a shoulder formed around the cavity.

6. An impact indicator substantially as hereinbefore described with reference to the accompanying drawings.

7. An artillery training shell having a recess in its end face wherein there is received an impact indicator in accordance with any one preceding claim.