GB2107031A - Practice grenade - Google Patents

Abstract

A primer tube (3) which penetrates into the interior of the inert charge (2) of a practice grenade brings the primer charge substantially to the centre of the envelope (1). In this part, the primer tube (3) comprises grooves (21 and 22), regularly distributed, and of which the depth lies between one quarter and approximately one half of the thickness of the primer tube in this zone. In this manner, safety is clearly improved. <IMAGE>

Description

SPECIFICATION Practice grenade The invention relates to practice grenades.

A practice grenade is proposed in French Patent No. 1 370 838 comprising an envelope of revolution of synthetic material, in one piece and substantially smooth provided with an opening which receives a priming tube extending in a blind manner to the interior of the envelope, of which the remainder is filled with a ballast material forming an inert charge, whilst the priming tube receives from its blind side the charge for bringing into operation and the remainder of the priming tube is arranged for its assembly, in operation, with a practice igniter plug while the priming tube is closed by a delay plug for storage conditions.

These practice grenades have been established as being advantageous, especially in relation to those of which the envelope is in several parts whether metallic or of synthetic material.

Some applications have however, revealed a disadvantage; it happens that the envelope is projected with sufficient energy two cause slight damage, in particular in the case of improper use.

The present invention seeks to find a solution to this problem.

According to an important characteristic of the invention, the part of the priming tube situated in the region of the charge for initiating operation comprises regularly distributed grooves, of which the depth lies between approximately a quarter and one half of the thickness of the priming tube at the said part of the priming tube.

Most advantageously, the said part of the priming tube comprises four grooves extending substantially over its length, and of a depth substantially equal to their width.

In one particular embodiment, the said primer tube is made by low pressure polyethylene moulding.

According to another preferred characteristic of the invention, the said priming tube only extends into the envelope over about two thirds of the depth of the latter, the said part of the priming tube provided with grooves being disposed in the central zone of the envelope.

Other characteristics and advantages of the invention will become apparent from reading the detailed description which follows, given with reference to the accompanying drawings, provided only to illustrate by way of non-limiting example one preferred embodiment of the present invention and in which: - Figure 1 illustrates in the form of a part sectional view a practice grenade; - Figure 2 illustrate in the form of a section an improved practice grenade; - Figure 3 is a sectional view of the part of the priming tube of the grenade of Figure 2; and - Figure 4 is a sectional view along the line of the section A-A of the priming tube of Figure 3.

The practice grenade of Figure 1 comprises an envelope 1 of revolution of synthetic material in one piece and substantially smooth. This envelope 1 is provided at its lower part with a flat base, and an upper part with an opening into which is engaged a priming tube, penetrating in a blind manner to the interior of the envelope 3, whilst this priming tube carries at its upper part a cap 4 capable of coming into engagement with a suitable thread formed around the opening of the envelope 1. The remainder of the envelope 1 is filled with a ballast material or forming an inert charge 2. The charge for-putting the practice grenade into operation is located within the priming tube 3. Finally the remainder of the priming tube is arranged for its assembly, in operation, with a practice ignition plug.In contrast, in the storage position the priming tube is closed by a delay plug 5 shown in Figure 1.

Figure 2 represents an improved grenade in accordance with the present invention, and corresponding elements to those of Figure 1 have retained the same reference numerals. Figure 2 shows that the priming tube 3 accommodates from the interior towards the exterior, a charge of detonating 'composition 31 , then a spacer 32 accommodating'a priming cap 33. The zone 34 is that intended to receive the practice igniting plug.

Here the wall 20 of the opening of the envelope 1 will be better seen, on which the cap'4 of the priming tube 3 is secured by screw'threads.

The improvement in accordance with the present invention relates esentially to the cooperation between this priming tube and the remainder of the'grenade.

Considered as a whole, the priming tube. is illustrated in a more detailed manner irk Figure 3.

Its cap 4, comprises an external flange 1.7, in which is formed internally the screwthread 18 intended to cooperate with the integral screwthread of the wall 20 of the opening of the envelope 1.

This collar 1 7 is connected by a radial flange 1 6 serving as a plane of support for the igniter plug with a main internal part of the primer tube, generally cylindrical, and which maybe subdivided into three sections 11, 12 and 13.

The part 1 3 receives the screw thread 15 intended to accommodate the delayplug 5 or alternatively the ingition plug in operation. The part 12 is that into which there will be engaged the active part of the igniter plug, and to define the bottom a peripheral groove 14, into which there is secured the spacer 32 carrying the igniter charge 33, which here is a cap with a base of black powder. Below, the priming charge itself 31 is placed, which is here a composition with a base of about 20% aluminium and about 80% of potassium perchlorate.

It will thus be seen that the priming charge is disposed within the priming tube below the groove 14 which is intended to receive the spacer 32. In this part of the primer tube, designated by the reference 11, in accordance with the preferred embodiment of the invention four grooves are provided, regularly distributed, and arranged axially within the cylindrical zone 11. A section of Figure 4 clearly shows these four grooves 21 to 24.

As the drawing shows, the depth of these grooves lies between approximately a quarter and a half of the thickness of the primer tube over this part of the tube, the tube itself being here in the form of a low pressure polyethylene moulding.

It will also be noted that in this instance the grooves extend axially over the whole length of the part of the tube in question 11, but it will be well understood that the grooves may be only provided over a part of the this zone. The drawing also shows that the depth of the grooves is substantially equal to their width, and preferably equal to about 1 mm. The thickness of the wall of the primer tube in this zone is at its side of the order of 2 mm. It is on the contrary somewhat greater, for example by 3 to 4 mm in the zones 12 and 13 already referred to.

According to another aspect of the invention, it will be noted that in Figure 2 that the primer tube penetrates into the envelope over about two thirds of the depth of the latter, the part 11 of the primer tube, provided with grooves, being disposed in the central zone of the envelope.

In a somewhat surprising manner, it has been established that the grenade of Figures 2 and 3 explodes with a very precise tear in the envelope, without any projection of the latter in the manner of a splinter, and whilst at the same time producing moreover the desired effects of a practice grenade, namely to distribute a cloud of inert charge, whilst causing a noise approaching sufficiently closely as possible to that of a normal device.

Although this has not yet been completely explained, it appears that the provision of grooves in the zone 11 of the primer tube is important for obtaining this result. This being the case, the detonating charge 31 will probably open initially at the level of these grooves, whilst applying itself upwardly on the spacer 32, itself rigidly anchored in the groove 41 of the primer tube. It is believed also, at the present time, that the central arrangement of this assembly within the envelope is desirable.

It should be understood that the present invention is not limited to the particular embodiment which has just been described, and extends to any equivalent modification and/or is in accordance with its spirit.

Claims (6)

1. A practice grenade, of the type comprising an envelope of revolution (1) of integral synthetic material and substantially smooth, provided with an opening (20) which receives a primer tube (3) extending in a blind manner to the interior of the envelope, of which the remainder is filled with a ballast material (2), whilst the primer tube accommodates, at its blind end, a priming charge (31), the remainder of the primer tube being arranged for assembly, in operation, with a practice igniter plug, characterised by the fact that the part of the primer tube (11) disposed at the region of the primer charge comprises regularly distributed grooves (21--24), of which the depth lies between one quarter and one half approximately of the thickness of the primer tube in the said part of the primer tube (11).

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2. A practice grenade according to claim 1,characterised by the fact that the said part of the primer tube (11) comprises four grooves (21, 24) extending substantially over its length, and of a depth substantially equal to their width.

3. A practice grenade according to one of claims 1 and 2, characterised by the fact that the said primer tube (3) is in the form of a low pressure polyethylene moulding.

4. A practice grenade according to one of claims 1 to 3, characterised by the fact that the said primer tube (3) does not extend into the envelope (1) more than about two-thirds of the depth of the latter, the said p-rt of the primer tube (11) provided with grooves lying in the central zone of the envelope (1).

5. A practice grenade comprising a casing, an igniter, a primer tube and a primer charge, the primer tube having grooves therein in the region of the primer charge.

6. A practice grenade substantially as hereinbefore described with reference to the accompanying drawings.