GB2413622A - Airgun system - Google Patents

Abstract

An airgun system comprises a gas reservoir 3 of generally cylindrical configuration and having a gas dump valve 7 at a forward end, a gun barrel 1 with an associated chamber 2A within which the said reservoir 3 is slidably receivable, an abutment means 4 arranged between said barrel 1 and said chamber 2A, and a firing mechanism 6,10 for driving the reservoir 3 forwardly within said chamber 2A the arrangement being such that such forward movement of the reservoir 3 is effective to discharge said reservoir 3 by causing abutment of said gas dump valve if 7 against the said abutment means 4, whereby the valve 7 is opened and gas discharged from the reservoir 3 is effective to propel a missile through the gun barrel 1.

Description

241 3622 Airgun System This invention concerns an improved airgun system

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 airg,uns have become well known, particularly those sold under lo 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. 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 characteristics of a pneumatic are found preferable by many shooters to the more traditional so 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 airgun using a one shot gas cartridge system would be more efficient as the reservoir of the cartridge only needs to hold a volume and pressure of gas sufficient for one shot.

However the cartridges need to be designed for efficient operation at a constant gas pressure.

Known gas cartridges are relatively complicated, of expensive construction and do not meet legal requirements in United Kingdom. There is therefore a need for a simple inexpensive and legally permitted one- shot gas cartridge system for an airgun.

In accordance with one aspect of the invention there is provided an airgun system comprising a gas reservoir of generally cylindrical configuration and having a gas dump valve at a forward end, a gun barrel with an associated chamber within which the said reservoir is slidably receivable, an abutment means arranged between said barrel and said chamber, and a firing mechanism for driving the reservoir forwardly within said chamber, the arrangement being such that such forward movement of the reservoir is effective to discharge said reservoir by causing lo abutment of said gas dump valve against the said abutment means, whereby the valve is opened and gas discharged from the reservoir is effective to propel a missile through the gun barrel.

By the term "gas dump valve" as used herein is meant a valve of the type that remains open when actuated so that all of the gas within the reservoir is discharged at once. This is in contrast to valves of the kind that remain biased towards the closed position by the gas pressure within the reservoir so that only a proportion of gas is discharged from the reservoir depending upon the force used to actuate the valve.

A dischargeable gas reservoir for use in the abovementioned system 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 l 92046A, but formed part of a self contained cartridge that was intended to receive a missile to be fired. Such cartridges are now illegal in United Kingdom. In accordance with this invention the valve of the reservoir is adapted to be released by abutment against a separate means that does not form part of a cartridge assembly. Thus, for example, the forward end of the valve member may project forwardly from the reservoir so that it can readily engage an abutment means positioned in front of the reservoir. Alternatively the abutment means may have a rearward projection for insertion within the front end of the 3s reservoir without mechanically engaging the latter to form an assembly.

In the system of the invention the missile to be fired is not incorporated into a cartridge but must be loaded separately into the gun. Depending upon the type of action selected for the airgun the missile may be loaded either directly into the gun barrel or may be placed into a missile s receiving means arranged between the barrel and the abutment means. Various alternative options will be described below, and further preferred features of the invention will become apparent therefrom and from the appended subordinate claims The invention is illustrated by way of example in the accompanying drawings in which: Fig l is a sectional elevation of one embodiment of an airgun system according to the invention shown in diagrammatic form and in a charged condition, Fig 2 is a similar view of the system shown in a discharged condition, Fig 3 is a view similar to Fig I showing a modified arrangement, Fig 4 is a further view similar to Fig I of another arrangement according to the Invention, Fig S shows a modification of the arrangement of Fig 4, Fig 6 shows a yet further modification of the arrangement of Fig 5, and Fig 7 is a diagrammatic view showing a method of charging a reservoir of the airgun system.

Referring to Fig I an airgun system comprises a gun barrel 1, an associated member 2 with a chamber 2A containing a gas reservoir 3 and a wad 4 containing an airgun pellet 5 to be fired through the barrel I by the pressure of gas from the reservoir 3. A firing mechanism comprises a member 6 slidably mounted within a frame portion 10 of the airgun, for imparting thrust agamst 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 rotary 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 wad 4 and a head 7A of as the valve member is moved rearwards relatively to a valve seat 3A.

The valve member 7 has a stem 7B sealed within the reservoir 3 by means of an O-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 s 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 lo unseat the valve head 7A, the valve 7 then snaps open into the position shown in Fig 2 and allows the gas charged within the reservoir 3 to be dumped through the wad 4 to drive the pellet 5.

The airgun system show can be reloaded by removing the wad 4 and reservoir 3 from the chamber 2A and inserting a reloaded wad 4 and recharged reservoir 3. For this purpose the member 2 can be displaced relatively to the barrel 1 and the frame 10 to bring the chamber 2A out of alignment with the barrel 1 and the firing member 10 so that it is accessible for reloading.

The member 2 may thus comprise a revolving cylinder or a transversely displaceable breach block of known type. A known plunger type ejection system as used in a revolver can be So employed for the removal of the wad 4 and reservoir 3.

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 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 withy the reservoir 3 when external gas pressure is removed.

Whilst one embodiment of the invention has been described it will be appreciated that various alterations can be made without departing from the spirit and scope of the invention. Thus, whilst the wads 4 have been shown as separate components for insertion in the chamber 2A, these could be formed integrally with a member designed to fit removably on the front of a revolving cylinder of the airgun and to receive a plurality of missiles that can be reloaded simultaneously. Such an arrangement is shown in Fig 3.

Alternatively instead of wads 4 the member 2 may have an integral missile receiving means and abutment for engagement by the valve member 7 as shown in Fig 4. Such an arrangement is suitable for muzzle loading of the missile receiving means with an appropriate missile such as a paintball. A yet further possible configuration of the system of Fig 4 is shown in Fig 5. In this case the valve member 7 does not need to be extended forwardly as the missile receiving means has a rearward extension 4A that can project into the front of the reservoir 3 to engage the valve head 3A.

In another modification the valve stem 7B can extend rearwards so that it projects from the rear lo of the reservoir 3 in the discharged state. The reservoir 3 can then act as an expanding ram during discharge in order to force the wad 4 or the member 2 forwardly for more gas tight engagement with the barrel 1. In this case the internal diameter of the valve seat 3A is preferably smaller than the diameter of the valve stem 7B. As the valve stem 7B moves backwards it engages the member 6 and the reservoir 3 is then forced forwards relatively to the member 6 by Is means of the gas pressure therein so that the wad 4 or its equivalent becomes clamped between the front end of the reservoir 3 and the barrel 1.

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 virtually impossible to convert to fire firearm JO cartridges as the firing mechanism uses the thrust member 6 in place of the conventional firing pm.

In Figs l to 5, for simplicity, the body of the gas reservoir 3 has been shown diagrammatically as If formed in one piece. However, in similar hitherto known constructions it has proved necessary to fabricate the body by machining several pieces of metal and then assembling them to form the body, as shown in Fig 4 of GB 2192046A. It will be appreciated by one skilled in the art of metal forming that other forms of construction may be utilised as desired.

so In the arrangements described above the reservoir 3 is arranged coaxially with the barrel I of the airgun. In some constructions it may simplify loading of the missile if the reservoir 3 is located in spaced parallel relation to the barrel 1.

In Fig 6 there is shown in diagrammatic form an arrangement that is suitable for a single shot s5 rifle or pistol. The components that correspond with those of Fig 5 are indicated with the same reference numerals. However in this case the missile receiving means 4 is omitted and an abutment 14A communicates with a transfer port IS leading directly to the bore of the barrel 1 that is arranged above the chamber 2A. The barrel 1 and the member 2 are also fixed with reference to one another and are shown as being integral for simplicity. In this case the missile 5 s 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 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 lo port 15. Such arrangements are well known and the means for enabling manual opening and closing of the bolt are therefore omitted for clarity. To enable insertion of the reservoir 3 into the chamber 2A and removal of the reservoir therefrom the member 6 is mounted not in the frame of the airgun but in a block 18 that 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. Such a firing mechanism may also be employed in other configurations of the airgun system according to the invention.

As already mentioned above the present invention does not include a method of charging the reservoir 3 described. For the sake of completeness, however one basic method will be described with reference to Fig 7. A gas supply union shown diagrammatically at 20 is fixed to a support not shown and has an inlet 21 for receiving gas at high pressure. The forward end of the reservoir 3 can be received in a bore 22 of the union and a gas tight seal is provided by an O-ring 23. A stop member 24 is movable towards and away from the union 20 to allow insertion of the reservoir 3 in the latter and can be locked in the position shown in order to retain the rear end of the reservoir 3 against the pressure of gas within the bore 22 of the union 20. A further stop member 25 can be inserted through an aperture in the stop member 24 in order to engage and locate the rear end of the valve member 7. With the stop member 25 retracted relatively to the valve member 7 gas is su pplied to the union 20 and the reservoir 3 is charged to high pressure since the valve member 7 is driven rearwardly under pressure to allow gas to enter the reservoir 3. Whilst maintaining the pressure within the reservoir 3 at a predetermined level the stop member 25 is driven forwards to engage the valve member 7 and to force the valve head 7A into engagement with the valve seat. The gas supply to the inlet 21 is now removed so that atmospheric pressure prevails on the downstream side of the valve head 7A and the valve is inherently biased into the closed position as described above. The stop members 24 and 25 can now be retracted to allow removal of the charged reservoir 3 from the union 20.

Claims (6)

1. An airgun system comprising a gas reservoir of generally cylindrical configuration and having a gas dump valve at a forward end, a gun barrel with an associated chamber within which the said reservoir is slidably receivable, an abutment means arranged between said barrel and said chamber, and a firing mechanism for driving the reservoir forwardly within said chamber, the arrangement being such that such forward movement of the reservoir is effective to discharge said reservoir by causing abutment of said gas dump valve against the said abutment means, whereby the valve is opened and gas discharged from the reservoir is effective to propel a missile through the gun barrel.
2. 2 A system according to claim 1, in which said gas reservoir comprises 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 s 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.

   so
3. 3 A system according to claim 2, in which the forward end of the said valve member is arranged to project forwardly from the said reservoir so that it can readily engage the said abutment means.
4. 4 A system according to claim 2, in which the said abutment means has a rearward projection for insertion within the front end of the reservoir to engage said valve head.
5. A system according to any one of claims I to 4, in which the said chamber is aligned with said barrel and is displaceable relatively thereto to enable insertion of a missile between the abutment means and the barrel.
6. 6. A system according to claim 5, in which the said abutment means forms part of a missile receiving means located between the said chamber and the barrel.

   a. A system according to claim 6, in which a plurality of the said chambers are arranged in a revolver cylinder so that each can be brought into alignment with said barrel and a corresponding missile receiving means is located in said cylinder adjacent each said chamber.

   8 A system according to claim 7, in which each missile receiving means is a separate member in the form of a wad that is insertable in the forward end of a said chamber and arranged to engage between the barrel and the cylinder.

   g A system according to claim 7, in which each missile receiving means is integral with said cylinder.

   lo A system according to any one of claims 1 to 4, in which the said chamber is located in Is parallel relation to said barrel, spaced from the axis of the bore therein, the forward end of said chamber being coupled to the bore of said barrel by means of a transfer port extending from said abutment means, the barrel having a loading port located to the rear of said transfer port and a sliding bolt member being arranged to open and close said loading port and to advance a missile from the loading port to a position in the bore of the barrel in front of said transfer port.

   A system according to any one of claims 1 to 10, in which a rear end of said chamber is closed by means of a block that is displaceable relatively thereto to enable insertion of a reservoir in said chamber, said block being associated with a firing member for transmitting 2s forward movement to said reservoir.

   ] 2 A system according to claim 1 1, in which the said block is a rolling block.

   3 A system according to claim 11, in which the said block is a falling block.