GB2424941A

GB2424941A - Airgun and exchangeable gas reservoir arrangement

Info

Publication number: GB2424941A
Application number: GB0520237A
Authority: GB
Inventors: Antony John Allen Bubb
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-08
Filing date: 2005-10-05
Publication date: 2006-10-11
Anticipated expiration: 2025-10-05
Also published as: GB2424941B; GB0520237D0

Abstract

An airgun comprises a barrel 1 for receiving a missile 5 to be fired, a bolt 17 movable relatively to said barrel 1 from a position enabling insertion of the missile 5 at a breech end thereof to a position in which a gas tight seal is formed behind the inserted missile 5, a chamber 2A for receiving an exchangeable gas reservoir 3 and a firing mechanism 6A,18 for discharging said reservoir 3. The chamber 2A is spaced apart from the bore of said barrel 1 in a direction perpendicular to the longitudinal axis of said bore and a transfer port 15 is arranged to communicate between said chamber 2A and the bore of said barrel 1. This arrangement prevents the airgun from being converted to fire firearms cartridges as the chamber 2A does not communicate directly with the bore of the barrel.

Description

Airgun This invention concerns an improved airgun of the kind wherein a

one shot air or gas cartridge is used to discharge a missile such as an airgun pellet.

Self contained gas cartridges for airguns have become well known, particularly those sold under the name Brocock and of the so-called tandem design.

Brocock cartridges have been designed to simulate a cartridge for a firearm and to be dischargeable by means of the firing pin of a firing system similar to that of a firearm. The cartridges are intended to be self contained, that is to say that they can incorporate a missile such as an airgun pellet as a firable part of the cartridge in the same way as a firearm cartridge. This, unfortunately, has the severe disadvantage that airguns adapted to fire the Brocock cartridge are too readily convertible to fire a firearm cartridge. For this reason, airguns using self-contained : gas cartridges have recently been banned in United Kingdom. * * **.*

Pneumatic airguns have become extremely popular in recent years, primarily because the S...

* ,20 characteristics of a pneumatic are found preferable by many shooters to the more traditional * : * *.: spring airgun. Pre-charged pneumatics are also preferred to the pump up guns in which the user must exert significant energy in pumping air into a reservoir before each shot. A pre-charged pneumatic has a reservoir that can store a sufficient volume of gas at high pressure to fire * ::: :* multiple shots without recharging. A popular source of high- pressure air for pre-charged pneumatic airguns is the diver's tank. However a pre-charged airgun is inherently inefficient as to fire many shots the initial charge must be at higher pressure than is necessary for a given power and the pressure reduces with each shot until it is insufficient to fire further shots and the gun must be recharged. For maximum accuracy and to comply with legal requirements some form of pressure regulation is necessary so that the muzzle energy of the gun remains constant with varying pressure in the reservoir. This complicates the mechanical construction and increases cost.

Theoretically an airguil using a one shot gas cartridge system is more efficient as the reservoir of the cartridge only needs to hold a volume and pressure of gas sufficient for one shot. There is therefore a need for a simple inexpensive and legally permitted airgun capable of using as as a power source an exchangeable gas reservoir that is capable of being fired in the manner of a one- shot gas cartridge.

The present invention provides an airgun comprising a barrel for receiving a missile to be fired, means movable relatively to.said barrel from a position enabling insertion of a missile at a breech end thereof to a position in which a gas tight seal is formed behind the inserted missile, a chamber for receiving an exchangeable gas reservoir of the kind capable of being fired in the maimer of a one shot gas cartridge, and a firing mechanism for discharging said reservoir, characterised in that said chamber is spaced apart from the bore of said barrel in a direction perpendicular to the longitudinal axis of said bore and that a transfer port is arranged to communicate between said chamber and the bore of said barrel in such a manner that, in use, gas discharged from a gas reservoir contained in said chamber is conducted to said bore at a point upstream of the position of an inserted missile.

A dischargeable gas reservoir for use in the airgun according to the invention may comprise a generally cylindrical body containing a valve member having a stem end slidably sealed in a first opening at or adjacent one end of the body and a head end adapted to engage an internal valve seat around a second opening at the other end of the body, the effective area of said valve head being greater than that of the cross- section of the said stem whereby the valve is biased closed in a stable position when the reservoir is charged with gas at an elevated pressure but becomes unstable and biased open when the valve head is displaced from the valve seat and subjected to * : :* the pressure of gas from within the reservoir. Such a gas reservoir is known from GB2 I 92046A, . but formed part of a self contained cartridge that was intended to receive a missile to be fired.

* Alternatively such a dischargeable gas reservoir may be formed by a known tandem air cartridge * :.: of the Brocock type that is used without an inserted missile so that it becomes a simple air reservoir rather that a self contained cartridge.

*::: :* In the airgun of the invention the missile to be fired is not incorporated into a cartridge but must be loaded separately into the barrel of the gun in a maimer similar to that of a precharged pneumatic airgun. The fact that the chamber for receiving the gas reservoir is displaced away from the axis of the barrel rather than being in line therewith makes it impossible for the gun to be converted to fire firearms cartridges.

Another advantage of the invention is that direct loading of the airgun pellet into the barrel rather than into the front of a cartridge ensures that the pellet is accurately fitted within the barrel without danger of deformation as it is transferred from a cartridge to the barrel upon firing. Accuracy of the airgun can thus be improved. The construction of the airgun is simplified in comparison with the known precharged pneumatic as there is no need for a bulky gas reservoir or for a gas regulator or discharge valve.

Further advantages and preferred features of the invention will become apparent from the following description and drawings and from the appended subordinate claims The invention is illustrated by way of example in the accompanying drawings in which: Fig I is a sectional elevation of one embodiment of an airgun according to the invention shown in diagrammatic form and in a charged condition, Fig 2 is a view similar to Fig 1 showing a modified arrangement, and Fig 3 is a further view similar to Fig 1 of another arrangement according to the invention, In the drawings, for simplicity, all relatively fixed components are shown as if made in one piece, although one skilled in the art will appreciate that in practice they may be assembled from several components for ease of manufacture. This is a mere matter of design that is not relevant to the invention. Referring to Fig I there is shown in diagrammatic form an airgun arrangement that is suitable for a single shot rifle or pistol. The airgun comprises a gun barrel 1, and an associated member 2 with a chamber 2A containing a gas reservoir 3. The barrel 1 and the member 2 are fixed with reference to one another and are shown as being integral for simplicity.

An abutment 4A is formed at the forward end of the chamber 2A and has a bore that * : communicates with a transfer port 15 leading directly to the bore of the barrel 1 that is arranged * * above the chamber 2A. A missile 5 can be loaded directly into the barrel 1 via a loading port 16 that is located to the rear of the transfer port 15. In a manner well known from pre-charged I...

* , pneumatic rifles the missile 5 can be advanced from the loading port 16 to a position in front of * : * * the transfer port 15 by means of a bolt 17 that is slidable to and fro in the rear of the barrel. The bolt, when in the closed position illustrated, also seals the bore of the barrel at a point between

. the loading port 16 and the transfer port 15. Such arrangements are well known and the means * for enabling manual opening and closing of the bolt are therefore omitted for clarity A firing mechanism comprises a member 6 slidably mounted within a block 18 of the airgun, for imparting thrust against the rear end of the reservoir 3 under the action of a suitable kinetically driven force applying member such as a hammer, or possibly a rotaly cam, indicated diagrammatically by the arrow X. When the reservoir 3 is driven forwards by the member 6 a forward end of a valve member 7 contained in the reservoir 3 abuts against the rear end of the abutment 4A and a head 7A of the valve member is moved rearwards relatively to a valve seat 3A. . .DTD: The valve member 7 has a stem 7B sealed within the reservoir 3 by means of an 0-ring 8 and the outer diameter of the stem 7B is less than that of the valve head 7A so that when the valve 7 is closed the elevated pressure within the reservoir 3 biases the valve 7 into a stable closed condition. However as soon as the seal between the valve head 7A and the valve seat 3A is broken the valve becomes unstable and the valve member 7 is driven rearwards by the gas pressure within the reservoir 3 acting on the valve stem 7B.

Provided that the kinetic energy of the firing mechanism driving the member 6 is sufficient to unseat the valve head 7A, gas from the reservoir causes a build up of presure behind the abutment 4a as the passage to the transfer port 15 is initially obstructed by the head of the valve 7. This increased pressure in front of the valve head 7A then causes the valve to snap open and allows the gas charged within the reservoir 3 to be dumped through the transfer port 15 to drive the pellet 5.

To enable insertion of the reservoir 3 into the chamber 2A and removal of the reservoir therefrom the block 18 is displaceable relatively to the chamber 2A, for example in the manner of a known falling block or rolling block rifle action. When the block 18 is configured as a falling block or rolling block it may be associated, in known manner, with a spring loaded hammer that can be released by a trigger to strike the member 6 as if it were a firing pin.

Alternatively a rotary member (not shown) that is releasable by a trigger in a similar manner to a hammer may simply have a cam surface that slides against the member 6 to impart forward movement thereto. * *. * * * **. .

* : : : * The method of charging the reservoir 3 to a high gas pressure does not form part of this invention. In principle any method can be used that enables gas to charged through the open end ** * .2o of the reservoir 3 past the valve member 7. The latter must be constrained by some external * : * * means so that it is free to move rearwards relatively to the reservoir 3 to allow gas to enter the latter, but is biased against the valve seat 3A to retain gas within the reservoir 3 when external gas pressure is removed. I... * *

* 25 It will be seen that the arrangement described is not only very simple and effective for the construction of an inexpensive airgun, but is also impossible to convert such an airgun to fire firearm cartridges as the chamber 2A is not in alignment with the barrel 1. This feature also allows the legal use of known tandem air cartridges that were designed to simulate a firearm cartridge as they cannot be used in the form of a self contained cartridge. That is to say they must be used without an inserted missile so that they are effectively simple air reservoirs and not cartridges.

Figure 2 shows a modified arrangement of the embodiment of Fig 1 for use with tandem air cartridges. In this case the abutment 4A is omitted and the chamber 2A is modified to receive a tandem cartridge in place of that shown in Fig I. The tandem cartridge is well known and thus is not illustrated for simplicity. The block 18 is arranged to close the chamber 2A and is provided with a conventional firing pin 6A in place of the member 6 of Fig 1. Although not illustrated for simplicity it will be appreciated that the chamber 2A and block 18 are similar to those of a conventional firearm and are provided, for example, with known loading and firing mechanisms and with an extractor for ejecting fired cartridges.

Fig 3 shows another arrangement that is similar to that of Fig 1 and in which like parts are indicated by the same reference numerals. However it has a different firing mechanism for discharging the reservoir 3 that avoids the need for the reservoir to be moved within the chamber s 2A at the time of firing. The general configuration of this embodiment is similar to that of a known so-called multi-pump pneumatic airgun and is thus suitable to enable the conversion of such a multi-pump airgun to use exchangeable reservoirs 3 of the type described above with reference to Fig 1. As is well known the multi pump pneumatic airgun normally comprises a barrel arranged above a tubular cylinder containing an air reservoir that communicates with the barrel via a transfer port and contains a discharge valve that is actuatable by the firing mechanism of the gun. The barrel has a loading port with a bolt action for feeding airgun pellets into the barrel in front of the transfer port. In front of the air reservoir the tubular cylinder contains a piston that is movable to and fro by means of a toggle lever linkage in order to pump air into the reservoir via a non return valve arranged at the forward end of the reservoir.

In the arrangement of Fig 3 the airgun adopts this known construction of the multi pump * : : pneumatic with the following exceptions. Instead of the air reservoir the tubular cylinder is * : : : : provided with the chamber 2A for receiving the exchangeable reservoir 3 and with a loading port 20, partially illustrated, for receiving the reservoirs 3. Instead of the pump piston the cylinder I...

* has a bolt 21 coupled to the toggle lever linkage in such a manner that the bolt 21 can be cycled * : *..: in the maimer of a known bolt action for the feeding and extraction of reservoirs 3 through the port 20. In known manner not illustrated the bolt 20 has a conventional extractor and the reservoirs have their rims shaped to cooperate therewith. S... * S S...

The abutment 4A is omitted in this embodiment and the transfer port 15 communicates directly with the front of the chamber 2A. Also in a manner similar to that of the precharged pneumatic airgun, there is provided a hammer 22 slidable in the member 2 and capable of being held in a cocked position as illustrated by means of a pivoted sear 23 that can be released by a known trigger mechanism, not shown. The forward end of the hammer 22 has a nose 22A that is guided in a closely fitting bore that communicates with the transfer port 15. The hammer 22 is loaded by a compression spring 24, and, when the sear 23 is released, is driven forward so that nose 22A impacts against the forward end of the valve member 7 and displaces the valve head 7A from the valve seat 3A. This causes the reservoir 3 to be discharged through the transfer port 15 and the barrel I in the manner already described above. However for the correct discharge of the reservoir 3 the following points are of importance. Firstly the bolt 21 should allow the communication of the chamber 2A to atmosphere so that the rear end of the valve stem 7B is subject to ambient pressure. Secondly the air passage from the reservoir 3 to the transfer port should be such as to allow rapid build up of the pressure of air from the reservoir 3 on the front side of the valve head 7A to ensure that the valve 7 remains open after the impact of the nose 22A of the hammer 22. Preferably the pressure of the bolt 21 should maintain an effective seal between the body of the reservoir 3 and the portion of the chamber 2A surrounding the transfer port 15. Other essential or preferred characteristics of the reservoir 3 and valve 7 are described in GB2192046A, * ** * * * S.. S S... * S *.S. S... * . S...

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Claims

I. An airgun comprising a barrel for receiving a missile to be fired, means movable relatively to said barrel from a position enabling insertion of a missile at a breech end thereof to a position in which a gas tight seal is formed behind the inserted missile, a chamber for receiving an exchangeable gas reservoir of the kind capable of being fired in the manner of a one shot gas cartridge, and a firing mechanism for discharging said reservoir, characterised in that said chamber is spaced apart from the bore of said barrel in a direction perpendicular to the longitudinal axis of said bore and that a transfer port is arranged to communicate between said chamber and the bore of said barrel in such a manner that, in use, gas discharged from a gas reservoir contained in said chamber is conducted to said bore at a point upstream of the position of an inserted missile.
2. An airgun as claimed in claim 1, in which the said chamber is adapted to receive an exchangeable reservoir in the form of an airgun cartridge of the kind intended to simulate a firearm cartridge, said chamber being associated with a firing mechanism comprising a firing pin for discharging such a cartridge. * I S...
3. An airgun as claimed in claim I, in which the said chamber is adapted to receive an airgun I...

reservoir of the kind comprising a cylindrical body that is slidable within the chamber to enable * : *.: actuation of a valve at a forward outlet end of the body, and in which a firing mechanism includes means for exerting thrust on said cartridge body at a rear end thereof.

* : : :*
4. An airgun as claimed in claim 1, in which the said chamber is arranged below the said barrel to extend away from said said transfer port in a direction towards the muzzle end of said barrel, and in which a bolt for loading exchangeable reservoirs into said chamber is coupled to a toggle lever linkage at the forward end of the airgun to enable cycling to said bolt for loading and extraction of reservoirs through a loading port arranged in front of said reservoir.
5. An airgun substantially as described herein with reference to Fig I of the accompanying drawings.
6. An airgun substantially as described herein with reference to Fig 2 or 3 of the accompanying drawimgs.