GB2278187A - Infantry weapons - Google Patents

Abstract

A simple and inexpensive breech block obturation system incorporates a flexible, annular seal 16. A tapered land 17 on a breech block 13 provides a secondary closure in the event of seal failure. Seal failure permits gases from barrel 1 to leak to channel 18 and thus via passage 19 to expel plug 20 indicating to a gun crew that seal 16 needs replacing. The invention can be usefully incorporated into an aerobutt gun or a field trials mortar. <IMAGE>

Description

INFANTRY WEAPONS This invention relates to improvements in infantry weapons and in particular, although not exclusively, to breech-loading mortars.

An object of the invention is to provide a compact, safe and reliable breech block obturation arrangement.

Conventional breech block obturators rely on either a complex pad obturator or a copper washer seal. Known arrangements have the disadvantage of requiring high preload forces in order to seal effectively and requiring precise location.

This invention comprises a breech-piece for attachment to a gun barrel, said breech piece including a breech ring and a breech block, wherein the breech block incorporates: a forward portion which forms a fine fit within a corresponding forward portion of the breech ring; a central portion having a recess in which is located a spring-loaded, annular, flexible seal for ensuring a gas-tight seal between the breech ring a breech block; and an aft portion having means for releasably securing the breech block to a corresponding aft portion of the breech ring.

By using a spring-loaded flexible seal, a gun incorporating the invention can be operated successfully at far higher pressures than conventional arrangements.

Furthermore, the invention advantageously provides a hand-fitting seal without the need for preload or precise longitudinal location of the breech block.

Further advantages of the invention are its low cost of manufacture and its lack of complexity. Also, the seal can be replaced, if need be, in the field, without the use of special tools or equipment.

The spring-loaded, flexible seal is preferably of the type having the registered trade name "Shamban Variseal".

Such a seal comprises a stainless steel spring whose outer surface incorporates a wear resistant coating.

The means for releasably securing the breech block within the breech ring can conveniently take the form of a screw-threaded arrangement. Alternatively, a wedge arrangement could be used.

Optionally, the central portion of the breech block may be tapered to provide a secondary closure in order to reduce hazardous gas leaks in the event of failure of the flexible seal.

As a further option, the breech block may incorporate a bleed line which forms a passageway for any gas escaping past the flexible seal (and past the taper if a taper has been provided).

The invention can be usefully incorporated into an aerobutt gun or a field trials mortar, for example.

Some embodiments of the invention will now be described, by way of example only, with reference to the drawings of which: Figure 1 is a cross-section of a breech piece in accordance with the invention and particularly suitable for use with an aerobutt gun, and Figure 2 is a cross-section of an alternative form of breech-piece in accordance with the invention and particularly suitable for use with a field trials mortar.

In Figure 1 a gun-barrel 1 is secured at one of its ends to a breech outer ring 2. Both gun-barrel 1 and outer ring are of generally cylindrical form and are secured to one another by means of co-operating screw-threaded portions 3 and 4 provided on the outer surface of the gun-barrel 1 and inner surface of the ring 2 respectively.

Extending from the threaded portion 4 of the outer ring 2 and remote from the gun-barrel 1 is a non-threaded portion, or land 5, in which is located (as a fine fit) a breech, inner cylindrical sleeve 6. A front face 7 of the sleeve 6 is separated from the gun-barrel 1 by a soft copper seal 8. Extending further from the land 5 is a second threaded portion 9 which carries a breech, inner, threaded ring 10 whose front face abuts the rear face of the sleeve 6. This inner, threaded ring 10 has a fine thread on its outer surface for co-operation with the breech outer ring 2 and a buttress thread 11 on its inner surface for co-operation with a corresponding thread on an aft threaded portion 12 of a breech block 13.

The breech block 13, which is made from a generally cylindrical block of steel alloy, has a forward portion 14 which forms a fine fit within the sleeve 6 and a central portion which incorporates an annular recess 15. Within the recess 15 sits a Shamban Variseal Static (RTM) seal 16 of u-shaped cross-section. The central portion of the breech block 13 is also provided with a tapered land 17 which extends from the aft threaded portion 12 towards the annular recess 15. At the point of commencement of the taper, there is provided an annular groove 18 which connects with a longitudinal passageway 19 which, in turn, opens out into the rear face of the breech block 13.

Located within the passageway 19 is a pellet 20 easily visible on the rear face of the breech block 13. An axial channel extending through the breech block carries a firing pin 21.

When the breech block is screwed into the inner ring 10 into its operational position (as shown in the drawing), the block forms a plug within the sleeve 6 with its tapered land 17 contiguous with the correspondingly-shaped inner wall of the sleeve 6. The seal 16 is compressed slightly in its recess 15 between the block 13 and the sleeve 6 and thus forms the primary seal which prevents gases generated within the gun-barrel 1 from escaping rearwards or outwards through the breech piece. The forward portion 14 of the block 13 nearly fills the sleeve 6 providing only a narrow passageway between the gun barrel 1 and seal 16, thus restricting direct exposure of the seal to combustion products.

In operation and with the breech block 13 removed, the gun-barrel 1 is charged, with a mortar bomb for example, by loading the bomb through the breech outer ring 2 and into position in the gun-barrel 1. Then the breech block 13 is screwed by hand into the inner threaded ring 10 to its fullest extent.

On operation of the firing pin 14 (which functions in a conventional manner), the bomb is fired from the gun-barrel 1.

High pressure gases produced by the charge are prevented from escaping past the breech block 13 by the action of the seal 16. Gas pressure on the seal 16 forces the arms of the flexible u-shaped seal 16 outwards against the walls of the breech block 13 and the sleeve 6, thus making its sealing action even more effective.

Once the mortar round has been fired, the breech block 13 is unscrewed by hand, a fresh charge is loaded and the breech block 13 is screwed into position again ready for the next firing.

Should the seal 16 fail, allowing gas to leak past it, the presence of the tapered land 17 acts to prevent serious leakage by acting as a secondary closure.

Any gas which escapes beyond the tapered land 17 is bled off via the annular groove 18 and passageway 19.

This escaping gas will expel the plug 20 to indicate to the gun crew that obturation was incomplete and that a new seal is required.

In Figure 2 an alternative breech piece comprises a breech ring 20, for attachment to a gun barrel (not shown), into which is inserted a breech block composed of two parts 22 and 22A. An aft part 22A of the block incorporates a shoulder 23 which is held up against a rear face of the breech ring 20 by a wedge arrangement (not shown) which is incorporated, along with an optional trigger mechanism in the rear portion 24 of the breech piece. A firing pin 25 is located within an axial channel running through the two breech block parts 22 and 22A.

The forward part 22 of the breech block forms a fine fit within the breech ring 20 and adjacent to its point of contact with the rear part 22A incorporates a recess 26.

In the recess 26 is a seal 27 of the type described with reference to Figure 1.

In operation, a mortar bomb can be loaded either via the gun muzzle with the breech piece in place, or can be breech-loaded with the breech piece initially removed. In either case firing can be initiated either by the trigger mechanism or by direct actuation of the firing pin.

High pressure gases produced in the gun barrel on firing are prevented from escaping past the breech block 22A by the action of the seal 27.

Claims (6)

1. A breech-piece for attachment to a gun-barrel, said breech piece including a breech ring and a breech block, wherein the breech block incorporates: a forward portion which forms a fine fit within a corresponding forward portion of the breech ring; a central portion having a recess in which is located a spring-loaded annular, flexible seal for ensuring a gas-tight seal between the breech ring and the breech block; and an aft portion having means for releasably securing the breech block to a corresponding aft portion of the breech ring.

2. A breech-piece according to claim 1 in which the means for releasably securing the breech block within the breech ring is a screw-threaded arrangement.

3. A breech-piece according to either preceding claim in which the central portion of the breech block incorporates a secondary closure means having the form of a tapered land.

4. A breech-piece according to any preceding claim in which the breech block incorporates a bleed line.

5. A breech-piece according to claim 4 in which the bleed line incorporates a pellet for indicating leakage of combustion gas.

6. A breech-piece substantially as herein before described with reference to the drawings.