GB2211588A

GB2211588A - Air guns

Info

Publication number: GB2211588A
Application number: GB8724881A
Authority: GB
Inventors: Antony John Allen Bubb
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-10-23
Filing date: 1987-10-23
Publication date: 1989-07-05
Anticipated expiration: 2007-10-23
Also published as: GB2211588B; GB8724881D0

Abstract

An air gun for use with air cartridges has a chamber (2) surrounding the bore (1) of the barrel and of substantially larger diameter than the latter. An air cartridge (10) can be received as a sliding fit in the chamber (2) to form a piston and cylinder arrangement so that air pressure developed during actuation of the cartridge tends to force the latter rearwardly. The mechanism of the gun is such as to allow rearward movement of the cartridge feed and/or be used to cause relative movement between the cartridge case (10) and a valve member (14) of the cartridge to ensure complete discharge of the latter. <IMAGE>

Description

IMPROVEMENTS IN AIR GUNS This invention concerns improvements in air guns, and more especially to an air gun for use with an air cartridge of the kind described generally in my co-pending Patent Application No. 8708693.

The invention also concerns certain improvements in air cartridges of the kind described in Patent Specification No. 8708693. Such improved cartridges are not necessarily restricted to use in the air gun according to the first aspect of the invention.

In accordance with a first aspect of the invention, an air gun comprises a generally cylindrical chamber portion surrounding the bore of the barrel, and of substantially larger diameter than the latter, the chamber portion being arranged to receive as a sliding fit a piston member the forward face of which is arranged to be pressurised by air discharged from the cartridge at the time of firing, whereby the piston member is caused to recoil relatively to the chamber for the purpose of transferring energy to an actuating mechanism of the gun and/or the air cartridge.

Conveniently, the piston member is formed by the frontal portion of the air cartridge itself. The recoil force consequently transmitted to the air cartridge may be utilised, for example, for cycling a semi, or fully, automatic cartridge feed mechanism of the gun. Alternatively, or in addition, the recoil of the cartridge may be utilised to improve the firing characteristics of the cartridge itself, in a manner to be described below.

In accordance with another aspect of the invention, a cartridge of the kind described in my co-pending Patent Application No. 8708693 and having the valve head on the downstream side of the air discharge aperture is modified by forming the valve member in more than one portion with the valve head and at least a part of the valve stem formed integrally from synthetic plastics material. This enables the valve seat to be formed integrally with the cartridge casing, substantially simplifying the frontal sealing arrangement of the cartridge.The portions of the valve member can be assembled together after passage of the part of the stem portion integral with the valve head through the outlet aperture, and in the case of the embodiment of cartridge provided with an air flow controi baffle, the latter may be a simple washer that is snap-engaged with a corresponding portion of the synthetic plastics valve stem during assembly of the valve member.

The various aspects of the the invention are illustrated by way of example in the accompanying drawing, the single figure of which is an elevation, partly in section, of an air gun in accordance with a first aspect of the . invention, shown equipped with air cartridges according to the second aspect of the invention.

In the drawings, the reference numerals indicate components of the arrangement as listed below.

1. Gun barrel 2. Chamber 3. 0-ring seal 4. Magazine 5. Bolt 6. Firing member 7. Ejector plunger 8. Compression spring 9. Extractor claw 10. Air cartridges 11. Front cartridge aperture 12. Rear cartridge aperture 13. Rear end plug 14. Valve stem 15. Valve head 16. Valve seat 17. End cap 18. 0-ring seal 19. Baffle washer 20. Bullet The air gun as illustrated may operate according to several optional arrangements. The firing member 6 may either be retractable and cockable with respect to the bolt 5 for release by an appropriate sear mechanism when the bolt 5 is in the closed position, or may form an integral part of the bolt 5, in which case the bolt 5 is itself a firing member latched by means of the sear mechanism, and the gun is fired from the bolt open position.

In the first case, the bolt 5 is spring loaded to a closed position wherein the bolt is moved to the left as viewed in the drawing in order to urge the forward end of the uppermost air cartridge 10 fully home into the chamber 2, with the extractor claw 9 engaging the rear extractor groove of the cartridge case and the ejector plunger 7 depressed against the depression spring 8.

To fire the gun the firing member 6 is released to strike the rear end of the air discharge valve, and fire the cartridge in the manner generally described in Patent Application No. 8708693. As the bullet 20 is discharged from the front of the cartridge 10, air will leak radially into the small air space between the front of the cartridge and the end wall of the chamber 2 surrounding the barrel 1, since the effective air seal between the cartridge and the chamber is made around the circumference of the cartridge 10 by means of the O-ring seal 3.Thus at the instant at which the bullet 20 enters the barrel the cartridge casing is subjected to a rearward thrust force determined by the pressure of the discharge air, and the cross-sectional area of the cylindrical cartridge casing Provided that the latter area is sufficiently large, and/or the air pressure to which the cartridge is charged is sufficiently high, this rearward thrust force will prove adequate to impart a recoil force to the spring loaded bolt 5 so that, after a delay determined by the inertia of the latter, and sufficient to enable the air pressure also to fire the bullet 20 effectively, the bolt 5 will recoil until the front of the cartridge 10 is retracted past the rear upper edge of the cylindrical chamber 2, to be ejected in the known manner of a semi-automatic firearm.At the same time, since the lower cartridges 10 in the magazine 4 are spring urged upwardly in the known manner, the release of the upward cartridge from the chamber 2 frees these cartridges for upward movement, whereby an additional ejection force is imparted to the extracted cartridge and next lower cartridge adopts the position of the uppermost cartridge as shown in the drawing, with the rear upper edge of the chamber 2 retaining the cartridge in position ready for feeding into the chamber 2 as already described.

It will be noted that the cartridge feeding system adopted here is effectively the reverse of that of the normal magazine, in that, since the magazine is integral with the gun, the rearward portion of the chamber 2 can serve to restrain the uppermost cartridge in position in a similar manner to the normal lips provided at the rear of a conventional exchangeable magazine. This enables the uppermost cartridge to be fed into the chamber 2 in a direct line so that the angled feeding required in a normal firearm is avoided. This is a consequence of the fact that air cartridges do not need to be fully chambered, being self-contained pressure vessels. This also has the result that the recoil movement required of the bolt 5 is substantially reduced in relation to that of a conventional firearm, so that the energy needed to recycle the firing mechanism is substantially lower.

In the case in which the gun is fired with the bolt 5 from the open position, the operation is substantially the same as described above with the exception that upon release of the bolt 5 the initial chambering of the cartridge is affected by thrust forces from the plunger 7, the extractor claw 9 and/or the firing member 6 (with a force insufficient to open the valve member) and firing of the cartridge is effected under the continued momentum of the bolt 5 as the front of the cartridge reaches the end of the chamber 2 and the bolt 5 can continue forwardly so that the firing member 6 displaces the valve head 15 from its valve seat. In this arrangement, since the firing member 6 is fixed with respect to the bolt 5, the rearward thrust on the forward end of the cartridge 10 during the initial build-up of air pressure in the chamber 2 will cause relative movement of the cartridge casing and.the valve member to maintain the fully open position of the air discharge valve. In this case the air baffle 19 may be omitted from the valve member, since its function in transmitting forward thrust force to the valve member relatively to the cartridge casing is no longer necessary. Therefore, the construction of the bolt -5 and firing member 6 as an integral unit may also be of advantage in gun mechanisms wherein the bolt 5 is a simple firing member and is not intended to recycle a semi-automatic cartridge feed mechanism.

It will be appreciated that various alterations may be made to the mechanism of the gun illustrated without departing from the scope of the invention. For example, the 0-ring seal 3 may be omitted if the tolerance between the cartridge casing and chamber 2 is sufficient to restrict the escape of pressure air to an acceptable level. Furthermore, although the rearward thrust from the pressure air is developed directly upon the cartridge itself, the rearward thrust force may be developed upon an intermediate annular piston provided between the front of the cartridge 10 and the bore of the barrel 1. Such an arrangement may allow a more flexible design of air cartridge. Moreover, it is understood that the gun mechanism is not limited to use with cartridges of the kind specifically illustrated, but could be utilised with any suitable.construction of air cartridge.

Turning now to aspects of the air cartridge as specifically illustrated, it will be noted that the cartridge is generally of the design as shown in Figs. 1 to 3 of Patent Application No. 8708693. However, in this case the valve seat 16 is formed integrally with the cartridge casing and the valve member comprises an integral head 15 and stem 14 formed of suitable material, e.g. Nylatron, dimensioned so that the valve stem can be assembled into the cartridge through the frontal discharge aperture. An end cap of material forming a suitable striking surface, e.g. hardened steel, is screw threaded to the rear end of the stem 14 and has a diameter larger than the affective area of seal between the valve head 15 and the seat 16. Preferably the valve head 15 and valve seat 16 have surfaces of slightly differing cone angle so that a near line seal is formed either at the internal periphery of the valve seat 16 or at the external periphery of the valve head 15, as desired. The baffle 19, when provided, may be a simple annular washer forced on to the valve stem 14 and snap-engaged with a groove therein after assembly of the valve stem 14 into the cartridge casing, and before attachment of the end cap 17.

The air cartridge may be charged in a similar manner to that described in Patent Application No. 8708693.

However when the diameter of the end cap 17 is to be greater than that of the bore 11, a sliding spigot and socket joint of larger diameter than the bore 11 may be provided at a point intermediate the outlet of the pump and a union of smaller diameter to be connected with the bore 11.

Claims

1. An air gun of the kind adapted for use with a precharged air cartridge, comprising a generally cylindrical chamber portion surrounding the bore of the barrel and of substantially larger diameter than the latter, the chamber portion being arranged to receive as a sliding fit a piston member the forward face of which is arranged to be pressurised by air discharged from the cartridge at the time of firing, whereby the piston member is caused to recoil relatively to the chamber for the purpose of transferring energy to an actuating mechanism of the gun and/or the air cartridge.

2.-An air gun as claimed in claim 1, wherein the piston member is an air cartridge provided in combination with the air gun.

3. An air gun as claimed in claim 1 or 2, comprising a recoil actuated automatic or semi-automatic firing mechanism arranged to derive energy from said piston.

4. An air gun as claimed in any one of claims 1 to 3, in combination with an air cartridge of the type having a valve member drivable forwardly towards an open position by impact from the rear of the cartridge, wherein the firing mechanism of the gun is adapted to allow rearward sliding movement of cartridge case while restraining the valve member, whereby pressurisation of said piston is effective to maintain the valve of the cartridge in the open condition following firing.

5. An air gun substantially as described herein with reference to the accompanying drawing.