EP0532721B1 - Revolver mortar - Google Patents

Abstract

Rapid fire mortar, comprising an ammunition cylinder, the liners (10) of which are fitted at their rear with a metal seal (22), the bottom (30) of which forms an ammunition support. The seal is slidingly mounted in the liner in order to compensate the manufacturing tolerances of the liners, its walls being capable of elastic deformation resulting from the effect of gas pressure during firing to provide a gas-tight seal between the liner and the firing plate.

Description

The invention relates to a barrel mortar, of the type in which a barrel tube is associated with an ammunition barrel mounted for rotation about an axis parallel to the axis of the tube and comprising several cylindrical open ammunition receiving sleeves at their front and rear ends and each of which is brought by rotation of the barrel to a shooting station in which it is aligned with the tube, its rear end then being supported on a shooting plate comprising means for firing the ammunition.

Patent FR-A-1 487 089 which is based on the preamble of independent claim 1, describes a cannon, that is to say an artillery piece, comprising inter alia a generally rifled tube extended by a chamber , a cylinder head and a cylinder head wedge. The ammunition is loaded by the breech by clearing the breech corner located at the rear of the tube. The weapon comprises a striker which is actuated to initiate the charge of propulsion. The projectile follows a taut or curved trajectory, according to the desired range, and is stabilized on trajectory by the rotation which is impressed on it by the scratches of the tube. There is therefore no similarity with a mortar.

Patent WO 92/01901) describes a handgun, in particular a hunting weapon which has no similarity to a cannon or a mortar. This handgun is intended for firing ammunition without a casing and sealing must be ensured by the chamber of the weapon itself and a sealing means is used for this.

Mortars of the aforementioned type generally equip armored vehicles and allow a relatively high rate of fire, thanks to the barrels whose shirts can be reloaded easily in ammunition during the shots, and which also allow a rapid burst fire when all the shirts a barrel were previously loaded.

However, the rotation of the barrel which makes it possible to bring the liners in turn into the firing position, that is to say in alignment with the cube and resting on the firing plate comprising means for firing ammunition , requires high dimensional accuracy of the parts in question by using more or less complex means to ensure gas tightness during firing while allowing rapid rotation of the barrel and loading of liners by their front end.

The invention aims to solve these problems by means of simple structure.

It proposes, for this purpose, a mortar, of the type in which a barrel tube is associated with an ammunition barrel mounted for rotation about an axis parallel to the axis of the tube and comprising several cylindrical casings for receiving ammunition, open at their front and rear ends and each of which is brought by rotation of the barrel to a shooting station in which it is aligned with the tube, its rear end then being supported on a shooting plate comprising means for firing the ammunition, each liner comprising means with elastic deformation ensuring gas tightness when fired with respect to the liner and the shooting plate, characterized in that the means with elastic deformation form a support and positioning stop for the ammunition introduced into the jacket by the front end of the latter, and in that these means consist of a metallic seal of generally cylindrical shape with ext open front end and rear end having an annular bottom wall with central orifice, this seal being mounted in a bore in the rear end of the liner and retained in this bore by means such as, for example, a screwed nut.

The elastic deformation of the aforementioned means, caused by the pressure of the propellant gases during firing, allows a perfect seal between the jacket and the firing plate. Furthermore, the weight of the ammunition loaded in the shirt allows an elastic support in slight prestressing of these means on the shooting plate when the shirt is brought into the shooting position.

In a preferred embodiment of the invention, the metal seal is mounted to slide without radial clearance in the bore of the jacket and is of rectified external cylindrical surface whose diameter is equal to the diameter of the bore of the jacket.

This sliding assembly without play of the seal in the jacket allows, without affecting the sealing, a correction of the dispersions of the dimensions of manufacture of the shirts. The rectification of the cylindrical surfaces in contact with the seal and the jacket also makes it possible to avoid metal-to-metal encrustations during firing, which would have the effect of trapping the seal in the shirt and preventing its normal operation.

According to another characteristic of the invention, the internal surface of the seal is cylindrical with a circular section in the vicinity of the bottom wall, with a diameter ensuring the centering of the ammunition, and is frustoconical at its front part, the wall thickness of the seal decreasing towards its front end.

This frustoconical internal surface has the function of facilitating the loading and positioning of the ammunition in the jacket, and also facilitating the elastic deformation of the corresponding part of the seal, which rests on the bore of the jacket to ensure the tightness, under the effect of gas pressure during a shot.

According to another characteristic of the invention, the external surface of the bottom wall of the joint is slightly frustoconical, its small base forming the aforementioned central orifice and being projecting from the bottom of the joint.

The internal surface of the bottom wall of the joint comprises an annular part situated in a plane perpendicular to the axis of the joint and connected to the internal cylindrical surface of the joint, to form a bearing face of the base of the ammunition, and a frustoconical part extending to the central orifice of the bottom part, the thickness of this wall decreasing in the direction of the axis.

Thus, the bottom of the seal is able to withstand the shock of a munition loaded by the front end of the liner and falling by gravity into this liner, and is also capable of deforming elastically to apply pressure to the plate and ensure gas tightness when firing.

• la figure 1 est une vue schématique en coupe axiale d'une chemise comportant un joint métallique selon l'invention;
• la figure 1A est une vue à plus grande échelle du détail encerclé I de la figure 1;
• la figure 2 est une vue semblable à la figure 1, mais représente la chemise en position de tir.

The invention will be better understood and other characteristics, details and advantages thereof will emerge more clearly from the description which follows, given by way of example with reference to the appended drawings in which:

• Figure 1 is a schematic view in axial section of a jacket having a metal seal according to the invention;
• Figure 1A is an enlarged view of the circled detail I in Figure 1;
• Figure 2 is a view similar to Figure 1, but shows the shirt in the firing position.

The joint according to the invention is particularly intended for use in an 81 mm rapid-fire mortar, such as that which has been developed by the applicant to equip light armored vehicles. Such a mortar is well known and its general structure has therefore not been shown.

The mortar barrel comprises five jackets, such as that shown diagrammatically in FIG. 1 and designated by the reference 10, which are of generally cylindrical shape with circular section and whose front 12 and rear 14 ends are open.

The rear end 14 of each liner 10 comprises, in the embodiment shown in the drawings, three successive bores 16, 18 and 20, of progressively decreasing diameter, which are used for receiving and maintaining a metal seal 22 according to the invention.

The bore 16 of larger diameter of the rear part of the jacket 10 has a threaded internal surface and receives a nut 24 for retaining the seal 22 in the jacket.

The second bore 18, of short length, is intended to receive an annular rim 26 projecting from the cylindrical external surface of the seal 22, while the third bore 20 constitutes the actual housing of the seal 22.

The seal 22 is made of spring steel and is of generally cylindrical shape, with an open front end 28 and a rear end comprising an annular bottom wall 30 with a central opening 32. The external cylindrical surface 34 of the seal has a diameter equal to that of the bore 20 of the jacket 10, is rectified, as well as the surface of the bore, to allow sliding without play of the seal in the bore 20.

The corresponding internal surface of the seal comprises a cylindrical part 36 of circular section, connected to the bottom wall 30 of the seal and having a diameter equal to the internal diameter of the jacket 10 beyond the bore 20, and also comprises a frustoconical part 38, extending the cylindrical part 36 to the front end 28 of the seal and widening towards this end, so that the wall thickness of the seal decreases towards its front end. The angle at the top of this frustoconical part 38 is not very pronounced, and is 8 ° in the preferred embodiment of the invention.

The bottom wall 30 of the joint has a frustoconical outer surface 40 with a very flat apex angle (of 179.26 ° in the preferred embodiment of the invention) and oriented towards the outside so that the edge of the central orifice 32 projects slightly outwards. The internal surface of this bottom wall 30 includes an annular part 42 perpendicular to the axis of symmetry of the joint, extended up to the central orifice 32 by a frustoconical part 44 having a smaller angle at the top than that of the surface frusto-conical exterior 40 (for example 172 ° in the preferred embodiment of the invention), so that the thickness of the bottom wall 30 decreases progressively in the direction of the axis of symmetry of the joint.

As indicated above, the seal also comprises an annular rim 26 projecting from its external surface, in the vicinity of its rear end.

To mount the seal 22 in the jacket, it suffices to introduce this seal into the rear end of the shirt, then to screw in place the nut 24 which abuts on the bottom of the first bore 16. The possible sliding of the seal 22 in the bore 20 of the jacket is then limited by the annular rim 26 which abuts, either on the nut 24, or on the bottom of the second bore 18 of the rear end of the shirt. When the seal 22 is in abutment by its annular rim 26 on the nut 24, the external surface of the bottom wall 30 of the seal 22 is slightly projecting outwards relative to the rear end 14 of the jacket 10 .

The operation is as follows:
in the loading position, which corresponds to that shown in Figure 1, the jacket is inclined obliquely to the horizontal, and is loaded with a conventional mortar ammunition, of which only the rear end comprising a stabilizer 46 is shown in FIG. 1. The ammunition is introduced through the front end of the jacket 12 and falls by gravity into the jacket onto the metal seal 22. The ammunition is centered by the cylindrical part 36 of the internal surface of the seal 22, and its support by the annular surface 42 of the bottom 30. Under the effect of the weight of the ammunition, which is of the order of 4 kg for an 81 mm mortar, the seal 22 is supported by its annular rim 26 on the retaining nut 24.

By rotation of the barrel, the jacket 10 containing the ammunition is brought into the firing position, represented diagrammatically in FIG. 2 in which it is aligned with the mortar tube 48 and is supported at its rear end on a firing plate 50 comprising in a bore 52 means, not shown, for firing the ammunition. The sliding mounting of the seal 22 in the jacket 10 makes it possible to automatically adjust the position of the seal 22, the bottom wall 30 of which is in elastic support on the firing plate 50, under the effect of the weight of the ammunition, the central orifice 32 of this bottom wall being aligned with the bore 52 of the firing plate 50 and having a diameter greater than that of the bore. A seal between the jacket and the firing plate 50 is thus ensured as soon as the jacket 10 is in the firing position. At the start of the coup, it develops very quickly a relatively high pressure inside the jacket 10, which is 100 to 600 bars depending on the propellant charge of the ammunition, and which has the effect of strongly applying the cylindrical wall of the seal 22 on the wall of the bore 20 of the jacket and, on the other hand, the bottom wall 30 on the firing plate 50, guaranteeing a seal against the propellant gases. Thanks to the structure described above, the deformations of these walls of the joint remain in the elastic range, and the joint regains its initial shape after the start of the blow, when the pressure decreases inside the liner 10.

As is clear from the above, the seal according to the invention provides a very good gas tightness when firing ammunition and allows, by its elastic preload on the shooting plate, to compensate for the dispersions of the dimensions of the shirts.

Claims (9)

1. A mortar, of the type in which the gun barrel is associated with an ammunition magazine mounted revolving around an axis parallel to the barrel axis and incorporating several cylindrical chambers (10) to receive the ammunition, open at their front and rear ends, and each one being brought through the revolution of the magazine to a firing position in which it is in alignment with the barrel (48), its rear end pressing against a firing plate (50) incorporating means to fire the ammunition, each chamber comprising elastically deformable means (22) ensuring gas tightness during firing with respect to the chamber (10) and the firing plate (50), characterised in that the elastically deformable means (22) form an abutment to support and position the ammunition introduced into the chamber from the front thereof, and in that said means are formed of a metallic seal (22) of a generally cylindrical shape having an open front end and a rear end fitted with a ring-shaped base (30) which has a central aperture (32), this seal being mounted in a bore (20) at the rear end of the chamber and held in place by means such as, for example, a screw retainer (24).
2. A mortar according to Claim 1, characterised in that the metallic seal (22) is mounted sliding, without radial play, in the bore (20) of the chamber and has a ground cylindrical outer surface whose diametre is equal to the diametre of the chamber bore (20).
3. A mortar according to Claims 1 or 2, characterised in that the inner surface of the seal is cylindrical with a circular section in the vicinity of the base (30), with a diametre ensuring that the ammunition is centred, and which is cone-shaped at its front part, the thickness of the seal wall tapering towards its front end.
4. A mortar according to Claim 3, characterised in that the vertex angle of the said cone-shaped inner surface (38) of the seal is around 8°.
5. A mortar according to one of Claims 1 to 4, characterised in that the outer surface (40) of the seal base (30) is slightly tapered, its small base forming the afore-mentioned central aperture (32) which protrudes from the seal base.
6. A mortar according to Claim 5, characterised in that the vertex angle of this cone-shaped outer surface is around 179.26°.
7. A mortar according to one of Claims 1 to 6, characterised in that the inner surface of the seal base (30) incorporates a ring-shaped part (42) located in a plane perpendicular to the seal axis and connected to the cylindrical inner surface of the seal to form a supporting face for the ammunition base, and a cone-shaped part (44) extending up to the central aperture (32) of the base part (30), the thickness of this wall tapering towards the axis.
8. A mortar according to Claim 7, characterised in that the vertex angle of the cone-shaped part (44) of the inner surface of the seal base is around 172°.
9. A mortar according to one of Claims 1 to 8, characterised in that the cylindrical outer surface of the seal incorporates, in the vicinity of its rear end, a ring-shaped rim (26) received in a short bore (18) of the chamber and working in conjunction with the bottom of this bore and with the afore-mentioned retaining means (24) to restrict the sliding of the seal with respect to the chamber.

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