FR2517046A1 - Cartridge case for firearm - has sheet metal welded cylindrical cage and end fitted firing cap - Google Patents

Abstract

The firearm cartridge case has a cylindrical case (21) made of metal sheet, welded edge to edge. At its ends are stiffening rings (23b), of U section, around the metal sheet. At the rear of the case is an end (30) with longitudinal channels for the propulsion gases. The end has an annular support (31a), also with holes to pass the propulsion gases. The end also houses the firing mechanism parts, consisting of relay charges (33,34) and a primer (35). The end part connects with an ignition transmission pipe (10) in the centre of the cover.

Description

METALLIC SOCKET AND PROPULSIVE LOAD
COMPRISING SUCH SLEEVE.

The present invention relates to a metal sleeve for containing a powder charge 9 it also relates to a propellant charge comprising such a socket
The shooting of projectiles by mortar-gun poses many difficulties; in fact, a mortar-gun is a device intended for the shooting of various projectiles; it must allow, indifferently, its charge by the mouth and by the breech of the barrel-tube For many reasons, among which> the exchangeability of the firing turrets, the harmful residues of the propulsive charge of the projectile; Ba need to evacuate the sockets pulled out of the turret, one is led to eject by the mouth of the barrel-tube all the unconsumed components of the propellant charge: the box of firing, the tube of transmission of fire, envelopes, etc ...

 To solve the problem of getting rid of the sleeve of the propellant charge, it has already been proposed to make consumable cardboard envelopes; these always leave residues of combustion which hinder the reloading of the weapon, by blocking the breech or the following projectile, with, consequently, all the risks of shooting accident which can result from it.

 In another way, work has been carried out to make ejection sockets using metal shells. Since these metal shells are subjected to very high internal pressure forces and extremely high temperatures, mechanical deformations and adhesion of these shells to the core of the barrel ensue and, in fact, it has proved impossible to ejector sockets of this type during the moment of shooting.

 To overcome this drawback, it has been proposed to make a perforated metal casing of a multitude of holes whose function aims to equalize the internal and external pressure forces applied to the casing wall; until now, this palliative has ended in failures, the desired security of fire not being reached.

 The object of the invention is to overcome all the aforementioned drawbacks and aims to provide a projectile socket whose operating safety meets the shooting safety requirements normally required in operation.

 To achieve this goal, the invention proposes to make a metal sleeve that avoids the self-fretting effect. To achieve this, it is necessary to equalize the pressures on the inner and outer faces of the casing of the socket. According to the invention, this object is achieved by a socket whose envelope is constituted by a welded wire cloth edge on board. Thus, the contacts between the bushing and the core of the barrel are punctual and the pressure of the combustion gases of the charge does not create forces tending to apply the envelope to the barrel tube.

 According to another characteristic of the invention, the envelope is welded wire to wire along a generatrix of the cylinder and is provided at each of its ends with a stiffening ring.

 From now on, we see other advantages provided by a socket made according to the invention: the envelope thereof is of low mass and requires only moderate energy for its ejection through the tubecanon.

 According to the invention, this projectile socket is equipped with a firing box (MAF) situated at the rear part of the socket, and this box comprises a plurality of longitudinal channels intended to create a local overpressure at the level of the cylinder-tube breech.

Other characteristics and advantages of the invention will emerge more clearly from the detailed description which follows of a nonlimiting exemplary embodiment, given with reference to the appended drawings in which:
Figure I, in a simplified schematic form, shows the elements of a propellant charge of a projectile placed in a gun mortar.

 Figure 2a shows the main parameters of the mesh of a wire mesh.

 Figure 2b shows a fragment of wire mesh.

 3 shows, in a longitudinal sectional view, an embodiment of the casing of a metal sleeve according to the invention.

 FIG. 4a represents, in longitudinal section, an embodiment of a propellant charge comprising a metal sleeve according to the invention.

 Figure 4b shows the details of the embodiment of the base of the metal sleeve.

 Figure 4b shows the details of the embodiment of the base of the metal sleeve.

 FIG. 4c shows the details of embodiment of the longitudinal channels disposed at the periphery of the base of the metal bushing.

 Figure 5 shows the pressure laws inside the tubecanon.

 Figure 1, in simplified schematic form, shows the elements of a propellant charge for a projectile placed in a barrel-tube. The barrel tube 1 comprises a bolt 2 allowing the loading of the propellant charge 4 coupled to its projectile 3. The end of the tube opposite the bolt is the mouth 5 of the barrel and the inner surface of the wall of the tube is designated like the soul 6 of the tube. The cylinder head is equipped, in its axial part, with a mechanical striker 7. The projectile 3 can be of a known type: perforating or splintering, or an arrow projectile, that is to say a projectile under calibrated pushed by a hoof. This projectile is mechanically coupled to the propellant charge 4 which comprises an envelope 8 containing a powder charge 9 and a fire transmission tube 10 having a plurality of perforations 11. On the opposite side to the projectile, the propellant charge is equipped with a MAF box (firing) 12 which contains the relay charges and is provided with a primer 13 which is placed opposite the firing pin 7.

 At the moment of firing, that is to say after percussion of the pyrotechnic primer 13 by the striker 7 located in the cylinder head 2 of the barrel, the order of firing the powder charge is propagated through the relay charges and the fire transmission tube 10 and causes the ignition of the powder charge. Under the pressure of the gases resulting from the combustion of this charge, the projectile 3, due to its weakened connection 14 with the propellant charge, is thrown out of the tube 1. At this moment, the unconsumed components of the propellant charge must be ejected through the mouth 5 of the barrel tube; to do this, the casing 8 of the sleeve must be able to slide freely in the core 6 of the tube and means must be provided to propel all the components through the tube, with a speed just sufficient to ensure the debris fallout in the immediate vicinity of the shooting turret.

 Before describing in detail an embodiment of the casing of the socket, we will recall the essential notions concerning the metallic cloths. Metal cloths are one of the members of the metal fabric family; they find their application in various industries, in particular for the sieving of particles, the direct filtration of fluids, as protection devices of various elements. A wire cloth is an object obtained by the interlacing of parallel stretched wires, called warp and wire son arranged perpendicular to the first by mechanical means (shuttle, clamps, projectiles) and called weft son.

 A wire cloth is defined by its armor which designates the interlacing mode of the warp and weft threads; by its texture which specifies the differences between the warp and the weft and finally by its mesh which designates the opening formed by the interlacing of the threads.

Depending on the weave and texture of the canvas, the mesh can be square, rectangular, triangular or other geometric shapes.

The parameters that characterize a wire cloth are shown in Figure 2a; Those are:
- The nominal opening of the mesh which, for square or rectangular meshes, indicates the respective distances V and V 'between 2 warp son and 2 son of consecutive frames.

the pitch which indicates the distances P and P 'axis to axis of 2 warp and 2 deformed wires,
the transparency which corresponds to the ratio in percentage, of the area of the openings to the total area, for example, for a square mesh, the transparency T is given by the following relation:
T (%) - (wreenllr) x 100 = V x 10B
(not) p2 and finally ~ the porosity which corresponds to the ratio of the percentage to the volume of the voids to the total volume. The section of the wires and the nature of the construction material of these wires must also be considered.

The choice of a wire mesh that meets the requirements of the problem posed, is based on the selection of characteristics and magnitudes of the parameters listed above. The most judicious choice seems to be provided by a web whose armor, or mode of interweaving of the threads, as represented in FIG. 2b, where each thread passes successively above and below the thread which it crosses with a thread. Offset of one (1) lead at each cycle. This type of armor provides an optimal anchorage of the threads, a regular mesh, a very strong mechanical rigidity and the transparency of the fabric can easily be varied between 30 and 95% .The choice of a square mesh provides a web of equal resistance and the choice of the sizes of the different parameters: the pitch, the section and the nature of the wire depend on the specific application of the sleeve of the propellant charge. Sometimes woven fabrics of high transparency are simply called "fences".

FIG. 3 shows an embodiment of a projectile socket 20, or more exactly the envelope of this socket according to the invention. The envelope 21 of the sleeve is formed by the winding on itself of a wire cloth, of which, only a fragment 21a is shown in this figure. This envelope is
obtained by cutting into a canvas roll of a piece of
length L substantially greater than the length of the load of
powder and width substantially less than the developed of
the soul of the barrel tube. This piece of canvas is arched to get
a cylindrical element of diameter D1, slightly less than
inner diameter of the tube-barrel, and whose chaste sons come
in contact along a generatrix 22 of the cylinder.
welding, the sections of the son in contact are made integral.

Different welding processes are applicable, however the pro
In this case, the laser welding process allows more mechanically robust wire-to-wire connections. To complete the
manufacture of the envelope, this one receives, at each of its ends
mits, stiffening rings 23a and 23b, of "U" section which
fit tightly into these ends of the envelope. For
consolidate the interlocking of these stiffening rings, these
can be glued to the canvas by a resin, such as a resin
epoxy. The outer diameter D2 of the rings is slightly inferred
the inner diameter of the barrel tube. According to a variant of
realization, these stiffening rings, or at least one of
these rings, can be integral parts of iron flanges
setting of the envelope.

As an illustration, the casing of a bushing with a diameter of 80
mm and a length of about 300 mm, can be built with
a wire mesh with square mesh, at a pitch of about 3 mm
diameters of weft and warp threads of the order of mm or
least, these filters being made of a material such as steel and,
preferentially, a stainless steel.

Fig. 4a shows an embodiment of a load
propellant for a mortar-gun comprising a bushing (20)
the external envelope 21, made of wire cloth, has already described on the
Figure 3. At the rear end of the casing 21 is arranged a
hollow cylindrical base plate 30 for housing the accesses
the firing of the propellant charge, for example,
relay charges 33 and 34 and a primer 35. This base, at its periphery, comprises at least one scope and, preferably, two bearing surfaces 31a and 31b, intended to provide a support of the sleeve on the core of the barrel. In addition, this base 30 is coupled to a fire transmission tube 10 centered on the axis of revolution of the envelope 21.This fire transmission tube contains rods 24 made of a pyrotechnic material and its wall comprises perforations 11, evenly distributed to ensure the uniform ignition of the powder charge 9. The end of the opposed fire transmission tube 30 is equipped with a ferrule 25 The function of this ferrule is to provide a means of coupling the propellant charge and the projectile 3 and, by means of centering feet 26, to ensure the alignment of the propellant charge and the projectile 3, which is equipped with a sealing belt 3b to the gas flow provided by the combustion of the loading 9. The connection 27 between the base of the projectile 3 and the ferrule 25 is weakened to allow a rupture of this connection at the instant of fire. Finally, the base 30 comprises a plurality of longitudinal channels 32 intended to allow the diffusion of a very small fraction of the pressurized gases supplied by the combustion of the load 9. This loading is constituted, for example, by small blocks of a pyrotechnic material such as "BALISTITE", which can be optionally protected from the external environment by a bag made of a consumable material.

 The base 30 of the metal sleeve, for clarity, is shown stripped of its firing accessories in Figure 4b. In this figure, we see that this base comprises a ferrule 26 for coupling to the fire transmission tube passing through the sleeve. It can also be said that the bearing surfaces 31a and 31b are slightly rounded to facilitate the sliding of the sleeve in the core of the barrel.

 FIG. 4c is a transverse view of the base 30 which shows the radial arrangement of the longitudinal channels 32.

To understand the function of the longitudinal channels 32 formed in the periphery of the base 30 of the socket, reference will now be made to FIG. 5, which represents the pressure laws.
P in the barrel tube at the instant of fire. The pressure P1 in the section of the barrel-tube defined, on the one hand by the sealing belt 3b of the projectile and the bearing surface 31a of the base increases extremely rapidly at time to, then decreases as soon as the projectile progresses in the tube and, afterwards, crosses the mouth of the tube. On the other hand, the pressure P2 resulting from the diffusion of the gases, through the channels 32, in the section of the tube adjacent to the cylinder head, increases with a certain delay to reach at a time t1 a value equal to that of the pressure P2. From this moment tl, the base 30 of the sleeve is subject to a pressure force which allows its progression inside the tube and, consequently, its ejection through the mouth of the tube. This force of pressure must be just sufficient to ensure the fallout of the unconsumed components of the propellant charge in the immediate vicinity of the barrel.

 Propellant firing tests constructed in accordance with the invention were carried out and confirmed the expected results.

 We now see more clearly the advantages of a socket whose envelope is constituted by a wire mesh.

The mechanical strength of the envelope is not hindered by its transparency to the ejection gases of the projectile; the reduced mass of the socket facilitates its ejection through the mouth of the barrel-tube; in addition, the simple geometric shape of this envelope allows automated manufacturing and a relatively low cost of implementation.

 Such a socket allows to build a propellant charge that can be introduced by the breech of a barrel and ejected at the moment of firing by the mouth thereof.

 The application of a metal sleeve made according to the invention is not strictly limited to a barrel mortar but, more generally, firing a projectile in a closed tube at one of its ends.

Claims (7)

 1. A propellant charge metal sleeve for a barrel, characterized in that it comprises a cylindrical envelope (21 consisting of a wire mesh welded edge to edge along a generatrix (22) of the cylinder, this envelope comprising two stiffening rings ( 23a and 23b) disposed at each of these ends.  2. Bushing according to claim 1, characterized in that the wire cloth is welded wire to wire.  3. Bushing according to claim 2, characterized in that the stiffening rings (23a and 23b) have a section 2'U 'which is interlocked in the wire mesh.  4. Bushing according to claim 3, characterized in that the stiffening rings are glued to the wire mesh  5. propellant charge for a barrel, characterized in that it comprises a socket according to one of claims 1 to 4 and - in that the rear portion of the casing (21) of this sleeve comprises a base (30) perforated by longitudinal channels for the diffusion of the combustion gases of the powder charge.  6. propellant charge according to claim 5, characterized in that the base (30) of the sleeve comprises at least one annular surface (31a) interrupted by diffusion channels of the combustion gas powder loading.  7. propellant charge according to claim 6, characterized in that the base of the sleeve is a firing box which contains the pyrotechnic relay charges and a primer.