HK1012701B - Gas cartridge - Google Patents

Description

The present invention relates to a method in which a cartridge is used to initiate the recycling of an automatic or semi-automatic firearm and to a cartridge for use in the method.

In connection with conventional pyrotechnic cartridges it is known to use the recoil produced when the cartridge is fired to apply a rearward force to the breech block of the firearm to set in train the reloading and recocking cycle.

Pressurised gas cartridges are also known from, for example, FR-A-2 403 536 and EP-A-499 332, but are incapable of generating sufficient rearward force to actuate recoil-operated automatic and semi-automatic firearms.

According to one aspect of the present invention in a method in which a cartridge is used to recycle an automatic or semi-automatic firearm, gas under pressure used to expel a projectile passes from a main chamber in a body of the cartridge through a passage, and a rearwardly directed force generated by the cartridge is applied to the breech block; the method is characterised in that compressed gas contained in the main chamber is released when the cartridge is fired and passes from the passage into an expansion chamber defined by a sleeve telescopically surrounding the body, to cause the sleeve and body to move relative to each other, whereby the cartridge applies force to the breech block, a valve member extending from the body being progressively withdrawn from an aperture in a forward radial wall of the sleeve as such movement takes place, the valve member preventing discharge of gas from the expansion chamber until a predetermined amount of relative movement has taken place between the body and sleeve, whereupon the aperture is opened and gas is discharged therethrough.

FR-A-2 403 536 discloses a cartridge comprising a body and a sleeve which telescopically surrounds the body; the body having a peripheral wall and also a forward radial wall enclosing a main chamber in which compressed gas is contained when the cartridge is in use, the forward radial wall having a passage extending therethrough to define a path for gas to leave the chamber, the sleeve having a peripheral wall surrounding the peripheral wall of the body and also a forward radial wall disposed forwardly of the forward radial wall of the body, the forward radial wall of the sleeve having therein an aperture, a first valve being provided to release gas from the main chamber when the cartridge is filed. A cartridge in accordance with another aspect of the invention is characterised in comparison with FR-A-2 403 536 in that an expansion chamber is defined between the forward radial walls of the sleeve and body respectively, and a valve member is arranged normally to close the aperture in the forward radial wall of the sleeve and to open the aperture in response to a predetermined amount of relative movement between the body and sleeve which takes place as gas enters the expansion chamber from the main chamber, thereby to discharge gas forwardly from the expansion chamber.

Following firing of a cartridge according to the invention, gas to be used to eject a projectile is admitted to the expansion chamber. The pressure of gas in the expansion chamber acts on the end wall of the body and drives the body rearwardly in the manner of a piston to apply force to the breech block. The sleeve is held in place by engagement with the wall of the chamber of the weapon. The gas is subsequently discharged from the expansion chamber and used to eject the bullet or other projectile. The moment at which the gas is discharged from the expansion chamber is determined by the sleeve and body entering predetermined relative positions. To this end, the valve may take the form of a spigot which extends axially from the body and normally projects into and obturates the aperture in the radial wall of the sleeve. The relative movement between the sleeve and body leads to the spigot being progressively withdrawn from the aperture until, in said predetermined relative positions of the body and sleeve, the spigot is withdrawn from the aperture and the gas from the expansion chamber exhausts through it. Although the bullet or other projectile may be held in place by a rim of the sleeve in a conventional way, it may alternatively be fitted to the spigot from which it is released at the instant the pressurised gas is applied to the projectile.

In the drawings:

• Figure 1 is a longitudinal section through a pressurised gas cartridge in its charged state prior to firing,
• Figure 2 shows the parts in their relative positions shortly after firing,
• Figure 3 shows the parts in their respective positions at the end of the firing sequence.

Referring to Figure 1, a cartridge has a two-part case formed from a body 10 and a sleeve 14 mounted telescopically on the body. The sleeve has a radially inwardly extending wall 16 at its forward end which bounds an aperture 53. The body 10 defines a primary chamber 21 for containing gas under pressure. Because the cylindrical portion of the sleeve is not under any gas pressure it may have a relatively thin wall. The body is provided at its forward end with an external annular shoulder 54 arranged to cooperate with an internal shoulder 54' at the rearward end of the sleeve in order to limit relative movement of the two parts. An 0-ring 55 seals the body to the sleeve at their forward ends.

The body has a radially inwardly extending wall 33 at its forward end which in the charged state is in close contact with the end wall of the sleeve. An axial spigot 51 projects from the wall 33 and is a sliding fit in the aperture 53. A cavity in the inner side of the wall 33 has a cylindrical portion which serves as a seat for the head 36 of a piston valve having a stem 13. The end wall of the cavity is conical in shape and formed with ports 34 opening into an annular V-sectioned groove in the outer surface of the end wall 33. The groove 60 forms a part of an expansion chamber to be described later. The valve head 36 is formed with a pair of collars 31, 32 defining a groove which receives an 0-ring sealing the valve head against the cavity.

An insert 11 is screwed into the rearward end of the body and is sealed relative to the body by an 0-ring 15. The insert has a cylindrical extension which defines a bore 20 which guides a skirt portion 57 at the rearward end of the stem 13. The primary gas chamber 21 surrounding the piston valve contains a gas, conveniently air, under a pressure which is preferably at least 50 bar (5x10⁷ Pa) and more preferably substantially 200 bar (2x10⁷ Pa).

In the charged state of the cartridge as shown in Figure 1, the body and sleeve are in their closed positions with the two end walls juxtaposed.

Upon the cartridge being fired, the piston valve is moved rearwardly, initially into the position shown in Figure 2. The valve head 36 is therefore withdrawn from the cavity 35 and frees the ports 34. Gas from the primary chamber escapes into the groove 60 and causes the body to begin its rearward movement relative to the sleeve. This movement begins the enlargement of an expansion chamber 61 which continues to enlarge as rearward movement of the body continues. Gas is prevented from escaping between the body and sleeve by the 0-ring 55. During this movement the spigot slides back through the aperture 53 until eventually it is withdrawn completely therefrom into the position shown in Figure 3. The air from the expansion chamber now escapes through the aperture 53 and ejects any projectile carried by the cartridge. The projectile may be held in place by a lip on the rim of the wall 16, or may be provided with a socket which receives the spigot 51. In the charged state of the cartridge as shown in Figure 1, the body and sleeve are in their closed positions with the two end walls juxtaposed.

The operating mechanism for the cartridge is substantially as described in EP-A-499 332 to which reference should be made and the operating mechanism will therefore be described only briefly.

The rearward movement of the piston valve is initiated by displacement of a relief valve which comprises a spool member supported within the skirt 57 of the piston valve. The spool member has a central body portion 12 and forward and rearward shoulders 42, 43 defining grooves for receiving 0-rings 40, 41. A stem portion extends rearwardly from the shoulder 43 and is located within a relief passage 23. Frusto-conical valve seats 44 in the relief passage 23 are contacted by a complementary portion of the rearward shoulder and by the rearward 0-ring. The forward 0-ring 40 is sealed against the bore within the skirt 57. A compression spring 50 applies a relatively weak pressure to the spool member. Two chambers are thereby formed, namely a secondary chamber 22 located between the end of the skirt 57 and the seal ring 41 and third chamber 47 located within the skirt 57 forwardly of the shoulder 42. The chamber 22 is in communication with the primary chamber 21 through a bleed passage existing between the skirt and the bore 20, so that in the charged state the pressures within the chambers 21 and 22 are equalised. A duct 46 extends through the spool member to connect the chamber 47 to a vent in the peripheral surface of the stem portion, whereby the chamber 47 is at atmospheric pressure.

Upon the stem portion 45 being struck by a firing pin moving in the direction of the arrow "A", the spool member is propelled into the skirt, so lifting the rearward shoulder 43 and 0-ring 41 from their seats.

Gas in the chamber 22 vents to atmosphere through the relief passage. Although some gas flows through the bleed passage 24 from chamber 21, this flow is negligible and does not prevent the pressure in the chamber 22 falling sharply. The gas in chamber 21 applies pressure to the forward surface of the skirt 57 which greatly overcomes that applied by gas in chamber 22 to the rearward rim of the skirt, and the piston valve tends to move rearwards, as discussed above.

Because chamber 47 is at atmospheric pressure and able to vent through duct 46, the spool member is drawn into the skirt, thereby allowing the piston valve to move towards the position shown in Figure 3.

By varying the length of the spigot 51 or the length of the body of the cartridge or the ratio of the former to the latter, the time at which gas is released and the projectile discharged may be adjusted relative to the rearward motion of the body.

Because the cartridge according to the invention is reusable, it is very suitable for use as training ammunition, particularly for semi-automatic pistols and other recoil-operated weapons. The cartridge may also be particularly suitable for use in paint-ball guns, because the ball may be adapted easily to fit on the spigot 51. Although the cartridge has been described as being used to eject a projectile, it will be appreciated that it may be used as a "blank" without a projectile but will still be capable of applying force to the breech block. Valve arrangements other than those shown may be used to admit gas to the expansion chamber in response to the cartridge being struck by the firing pin, and to discharge gas from the expansion chamber at the desired instant.

Claims (5)

1. A method in which a cartridge is used to recycle an automatic or semi-automatic firearm, wherein gas under pressure used to expel a projectile passes on firing of the cartridge from a main chamber (21) in a body (10) of the cartridge through a passage (34), and a rearwardly directed force generated by the cartridge is applied to the breech block, characterised in that compressed gas contained in the main chamber is released when the cartridge is fired and passes from the passage into an expansion chamber (61) defined by a sleeve (14) telescopically surrounding the body (10), to cause the sleeve (14) and body (10) to move relative to each other, whereby the cartridge applies force to the breech block, a valve member (51) extending from the body being progressively withdrawn from an aperture (53) in a forward radial wall (16) of the sleeve as such movement takes place, the valve member preventing discharge of gas from the expansion chamber (61) until a predetermined amount of relative movement has taken place between the body and sleeve, whereupon the aperture is opened and gas is discharged therethrough.
2. A cartridge comprising a body (10) and a sleeve (14) which telescopically surrounds the body; the body having a peripheral wall and a forward radial wall (33) enclosing a main chamber (21) in which compressed gas is contained when the cartridge is in use, the forward radial wall (33) having a passage (34) extending therethrough to define a path for gas under pressure to leave the chamber (21), the sleeve (14) having a peripheral wall surrounding the peripheral wall of the body (10), a forward radial wall of the sleeve (16) being disposed forwardly of the forward radial wall (33) of the body, the forward radial wall (16) of the sleeve having therein an aperture (53), a first valve (36) being provided to release gas from the main chamber when the cartridge is fired, characterised in that an expansion chamber (61) is defined between the forward radial walls (16, 33) of the sleeve and body respectively, the aperture (53) being normally closed by a valve member (51), the valve member (51) serving to open the aperture in response to a predetermined amount of relative movement between the body and sleeve which takes place as gas enters the expansion chamber (61) from the main chamber (21), thereby to discharge gas forwardly from the expansion chamber.
3. A cartridge as claimed in claim 2, characterised in that the valve member (51) extends from the forward radial wall (33) of the body (10) into the aperture (53) in the forward radial wall of the sleeve (14), whereby relative movement of the sleeve and body as gas enters the expansion chamber causes the valve member (51) to be withdrawn relative to the aperture (53).
4. A cartridge as claimed in claim 3, characterised in that the valve member (51) is in the form of a spigot, and a projectile has a socket which receives the spigot.
5. A cartridge as claimed in any of claims 2 to 4, characterised by a cavity (35) in the wall (33), the cavity (35) opening into the main chamber (21), the cavity having a conical radial wall from which a plurality of ports (34) open through the wall (33) into the expansion chamber (61), a valve head (36) being received in the cavity (35) and being withdrawable from the cavity (35) by an operating mechanism responsive to movement of a stem (45) positioned to be struck by a firing pin, to allow compressed gas to escape from the main chamber (21) into the expansion chamber (61).