GB2307033A - A cartridge for an air gun - Google Patents

Abstract

A cartridge 10 is disclosed for use in a compressed gas powered weapon, such as an air-gun. The cartridge 10 has a tubular housing 20 and a projectile comprising a wad portion 30 for forming a seal with the housing as the projectile is expelled and a travelling portion, such as shot pellets 35, intended to travel furthest and hit a target. A paper membrane or plastics disc 25 retains the pellets in the housing before use. The disc 25 and is attached to housing 20 by thin webs which readily break as the projectile (and disc) are expelled.

Description

A CARTRIDGE FOR AN AIR GUN The present invention relates to an air gun, and in particular to a cartridge for use with an air-gun.

The term air-gun is used herein to denote any type of barrelled weapon which uses compressed gas to fire a projectile. There are a number of known arrangements for storing and releasing a controlled amount of compressed gas into a firing chamber of a gun. Air-guns are commonly made in the form of a pistol or rifle and used for recreational target shooting firing relatively small pellets.

Prior art cartridges using gunpowder have a number of disadvantages. They are inherently volatile, due to their explosive material content. The cartridges are vulnerable to degradation if exposed to excess heat or humidity and have a limited storage lifetime. Further, powder cartridges are relatively difficult and expensive to manufacture.

When fired, powder cartridges produce a loud retort which, for sports shooting activities especially, may cause noise pollution for persons in the vicinity. Further, the loud retort of gunfire may startle or disturb a live target or prey, and may reveal the position of the firer. Also, all powder cartridge guns have a strong recoil, which may be uncomfortable or even dangerous for the user.

An aim of the present invention is to provide a cartridge which overcomes at least some of the disadvantages associated with powder cartridges.

Examples of prior art cartridges for use with air guns include EP-A-O 281 592 and US 3 111 121 and problems here include excessive air leakage past the projectile.

According to the present invention there is provided a cartridge for use in an air-gun, comprising: a cartridge housing; and a projectile locatable within the housing, said projectile for being expelled by compressed gas applied to said housing, said projectile comprising a wad portion for forming a seal with the housing as the projectile is expelled and a travelling portion intended to travel furthest and hit a target.

The cartridge may have a lip portion at or near the rear of the housing, preferably rearmost. The lip portion protrudes radially outward from the housing to aid handling, including insertion and removal of the cartridge, and to aid location of the housing in the firing chamber since the lip may fit into a corresponding recess.

The projectile is preferably locatable inside the housing with a relatively snug fit and the wad portion forms a relatively loose but substantially air-tight seal with the interior of the housing. This seal inhibits compressed air from bypassing the projectile when the gun is fired.

The cartridge may be provided with stop means which operatively retains the projectile at a desired location within the housing. In one embodiment, an inwardly protruding lip is formed at the rear of the housing, which acts as a stop to inhibit the projectile from moving rearwardly out of the housing.

The projectile may comprise one or more separate or linked parts. Preferably, the projectile comprises a separate wad locatable rearmost in the housing so as to push a separate travelling part.

The stop means mentioned above is ideally positioned to leave a gap or void between the rear of the projectile and the rear of the housing. When firing, this void allows a buildup of pressurised gas behind the projectile and within the housing, which improves performance.

The wad may take any suitable form. In a simple from, the wad is a disc or cylinder of material such as lead or plastics material. The wad preferably comprises an elongate body portion having a disc or discs radiating therefrom. In one embodiment, a disc is provided at either end of a cylindrical body portion. The body portion gives the wad rigidity and inhibits twisting of the discs.

One or more of the disc or discs may comprise flexible material and may be oversize so as to be forced against the interior of the housing. In one embodiment, the wad has at least one rigid disc for strength and stability, and at least one flexible disc for an efficient seal.

In a second preferred embodiment the wad is substantially U-shaped in cross section, having tubular body portion closed at one end by a circular disc portion. The wad is arranged in the housing with the open end of the tube rearmost so that, in use, compressed air applied to the rear of the housing forces the walls of the body into a sealing abutment with the interior of the housing. The open end of the body may also have an external sealing ring portion.

The travelling portion may take any suitable form, such as shot pellets, a single pellet, a bullet, a shell, or a dart (including a tranquilliser dart). In the preferred embodiment the cartridge is used as a shotgun cartridge and the projectile comprises a wad and a plurality of shot pellets. The length of the wad is chosen such that a predetermined amount of shot may fill the remainder of the cartridge housing.

Retaining means may be provided at one end of the housing to retain the projectile during transportation and loading of the cartridge.

In one form, the retaining means may be a thin membrane, such as paper or plastics material, adhered to the housing. When fired, the projectile may burst through the membrane. The membrane may be used to seal the interior of the housing, e.g. to prevent moisture penetration.

The retaining means may also be a web, mesh or disc, suitably of plastics material. A weak link is preferably provided between the retaining means and the housing, e.g.

by making perforations or by forming thin connecting web(s). When fired, the retaining means can be easily ejected together with the projectile.

Also according to the present invention there is provided a breech arrangement for an air gun: said breech arrangement including a breech block for receiving a pellet, or alternatively a cartridge as described herein, wherein said breech block is pivotable in a plane orthogonal to the longitudinal axis of said breech arrangement.

The firing chamber is sized appropriately to receive either a pellet or a cartridge. A removable plastics material inner sleeve may be used to give the desired internal diameter.

The breech arrangement allows the breech block to pivot from a closed position where a firing chamber is operatively in line with a barrel of a gun, to an open position where a cartridge may be inserted longitudinally into the firing chamber of the breech block.

The breech block may be mounted to a body portion of the breech arrangement by a longitudinal pivot bar. A closure arrangement for retaining the block in the closed position is provided, preferably opposite the pivot bar. In one embodiment, the closure arrangement comprises a closure lever pivotably mounted on the block such that a portion of the lever is engageable into a corresponding recess in the body, or vice versa.

The breech block preferably comprises means for ejecting a cartridge. In one embodiment, the block has a cylindrical through-bore forming the firing chamber. The firing chamber has a spring biassed internal sleeve. The sleeve acts against the housing, such as against an outwardly protruding lip or rim portion.

Ideally, the breech body has a sloped portion such that as the breech block is rotated toward a closed position, a cartridge is forced by the slope portion into the firing chamber and against the biassing of the ejection sleeve.

Opening the block allows the sleeve to eject the cartridge.

Preferably, the breech block is sized to be slightly smaller in length that the cartridge. Also, the breech body snugly receives the block and the gap in the body is itself slightly shorter than the cartridge. This ensures that the cartridge fits tightly against the breech body and helps to provide an effective air seal, especially where the cartridge is made from a relatively soft material such as plastics material. This seal may be further assisted by the ejector mechanism biassing the cartridge against the body.

Commonly, the pressurised gas reservoir of an air rifle is an elongate cylinder mounted below the barrel. The firing mechanism operates a valve mechanism to release the gas. For greatest efficiency, it is desired to apply the gas from axially behind the firing chamber, i.e. in the direction of intended travel of the projectile. However, where the reservoir and valve mechanism are mounted below the firing chamber, the ideal direction of application is difficult to achieve.

Further, according to the present invention there is provided a breech arrangement for an air gun, comprising a gas transfer port for transferring gas from a pressurised gas reservoir to a firing chamber, wherein a first portion of said transfer port is angled with respect to the longitudinal axis of the breech arrangement.

The first portion may lead into a second portion which is arranged co-axially with the firing chamber, so that gas is applied from the desired direction. Any 90 degree bends are avoided, since these create bottlenecks and, at high pressures, tend to send gas back toward the reservoir.

In the prior art, the firing mechanism of an air gun is commonly cocked by pulling back a bolt, the bolt having a radial finger arm which is guided along a longitudinal slot.

The bolt is released by the trigger mechanism and operates a valve mechanism. The trigger may be sensitive and, for example through rough handling, may cause the gun to fire when not intended.

Yet further, according to the present invention there is provided a trigger mechanism for an air gun, comprising a longitudinal guide slot, wherein said guide slot has an offset recess or gate portion for retaining a finger arm.

The retaining recess or gate portion acts as a safety gate. The bolt is pulled back by the finger arm and is rotated such that the finger arm lies in the safety recess.

In this position, the bolt is inhibited from moving forward, so accidental operation of the trigger does not cause the gun to fire. To fire, the bolt must first be rotated so that the finger arm is realigned with the guide slot.

The trigger mechanism comprises a number of parts, including a trigger block which is used to release the firing bolt mentioned above. The block commonly comprises a housing and a number of levers. In one prior art arrangement, a vertical pivot bar is connected to a horizontal shear bar. At the downward end of the vertical bar is connected a second horizontal bar. This second bar is connected to a curved, downwardly extending finger bar.

Pulling the finger bar with the finger moves the shear bar to release the remainder of the mechanism.

A disadvantage of this prior art arrangement is that the vertical bar, shear bar, horizontal bar and finger bar are all manufactured separately and assembled together such as with screw and thread joints. This leads to high labour costs and unreliable operation as the parts must be checked and retightened from time to time.

Still further, according to the present invention there is provided a trigger mechanism for an air gun comprising a vertical bar, shear bar, horizontal bar and finger bar, wherein these four bars are a single integral bar.

The single bar, called herein an f-bar, can be manufactured as a single unit such as by laser cutting. The single f-bar substantially reduces labour costs and reduces maintenance work.

By way of example, preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a sectional side view of a cartridge; Fig. 2A is a side view of a first wad; Fig. 2B is a side view of a second wad; Fig. 3 is a sectional side view of a cartridge housing; Fig. 4 is a sectional side view of a breech block; Fig. 5 is an end view of the breech of Fig. 4; Fig. 6 is a sectional side view of a breech arrangement and barrel; Fig. 7 is an end view of the breech of Figs. 4 & 5 in operation in conjunction with the breech arrangement of Fig. 6; Fig.s 8-10 show an alternative breech arrangement; Fig.s 11 & 12 show an alternative breech block; Fig. 13 shows an alternative cartridge; Fig.s 14 & 15 show a bolt guide with safety recess; and Fig.s 16-18 show a part of a trigger mechanism.

Referring firstly to Fig. 1, cartridge 10 comprises a cartridge housing 20 and a projectile including wad 30 and shot 35.

In use, the cartridge 10 is loaded into the firing chamber of the breech of a gun. Compressed air applied to one end of the housing expels the projectile.

Housing 20 is generally elongate and tubular. Rim or lip 22 at one end of the housing is used to locate the cartridge in the firing chamber and to hold the housing during firing. The housing may be made of any suitable material, such as metal, but in the embodiment is moulded from plastics material.

In one embodiment, the projectile is a bullet. The wad 30 shown in Figs. 1-3 itself serves as an effective bullet.

Persons skilled in the art will readily appreciate that a wide variety of projectiles may be used. Of particular applicability is a dart, such as a tranquilliser dart for use on animals. The projectile or at least part thereof may be coloured to be highly visible, or may be fluorescent for night use.

In the embodiment shown in Fig. 1, a travelling part of the projectile comprises shot pellets 35. Standard prior art shot pellets may be utilised, such as those used in shotgun powder cartridges. The cartridge may be sized to carry the same quantity of shot as a prior art powder cartridge. In the embodiment, the diameter of the cartridge is kept constant, at around 9 mm. The length of the cartridge is selected according to the shot capacity required.

Retaining means 25 is provided at one end of the housing to retain the projectile, i.e. during transportation and loading of the cartridge. In one embodiment, retaining means 25 is a thin membrane of paper or plastics material which is moulded into or adhered to the housing 20.

In the embodiment shown in Figs. 1 and 3, the retaining means comprises a circular plastics material disc 25 secured to housing 20 by thin webs 26. When the projectile is fired, the disc 25 breaks away from the housing and is expelled together with the projectile 30,35.

To assemble the cartridge, a measured amount of shot 35 is loaded into housing 20, and then wad 30 is inserted.

This is a relatively simple process and may be done by the user, with variations in components selected according to personal preference. The length of wad 30 is selected such that the remainder of the housing holds a desired amount of shot. A typical range is between 30-90 grams of shot.

Wad 30 forms an effective air seal against the inner surface of the housing. As shown in Fig. 2A, wad 30 may comprise an elongate body portion 31 having a disc 32,33 at either end. Fig. 2B shows a second embodiment of the wad 30, comprising a tubular body 34 closed at one end by integral disc 36. At the rear sealing ring 37 runs around the exterior circumference of the body 34. Typical dimensions of the wad for use with a 9mm barrel would be 9mm outside diameter for body 34, 9.55mm for sealing ring 37, and 5mm long. Wad 30 may be made of any suitable material, such as lead or other metal, but in the preferred embodiment is moulded from plastics material.

In use, cartridge 10 is arranged in the firing chamber of the breech such that ends 21 of housing 20 abut one end of the barrel portion of the gun. The internal diameter of the cartridge is preferably substantially identical to that of the barrel, such that a contiguous, substantially continuous, smooth internal surface is achieved.

To fire, wad 30 is subject to air or gas pressure using delivery/release arrangements well known in the field of air pellet guns. Air pressure acting on wad 30 ejects the wad together with shot 35 through or together with retaining means 25. Since there is a smooth internal surface, the projectile moves cleanly from the housing into the barrel.

The wad preferably provides an air seal also whilst in the barrel.

Cartridges can be made having a wide range of diameters, to fit a wide range of barrels. All common prior art barrel sizes for powder cartridge firearms can be achieved, including the popular 9mm (.38) for bullets and 12, 16 and 20 gauges for shot (20, 18 & 17 mm respectively).

Larger shells are also possible, e.g. for use as artillery or field guns. Limitations arise mainly in the available compressed air delivery arrangements.

Figs. 4-7 show a preferred breach arrangement for loading cartridges such as shown in Figs. 1-3 into the breech of a gun.

Referring firstly to Fig. 6, the barrel 40 and part of the breech arrangement 50 of a gun are shown. Compressed gas, such as from a pre-charged compressed air reservoir, is released upon action of a trigger arrangement and directed into channel 52 of the breech arrangement. The compressed air from channel 52 exits opening 53 into the firing chamber of the breech to expel the projectile.

Fig. 4 shows a sectional side view of a breech 60 having a firing chamber 62 for receiving a cartridge such as shown in Figs. 1-3. Chamber 62 has an enlarged section 64 at one end for receiving retaining rim 22 of cartridge 10.

The main cartridge housing 20 fits into chamber 62.

Breech 60 may be provided with ejector means for ejecting the housing 20, i.e. after firing. The ejector means in one embodiment is a washer or pin(s) acting, e.g.

by means of spring biassing, against the rim 22.

As shown in Figs. 5 and 7, breech 60 is pivoted or hinged with respect to breech arrangement 50. A pivot pin engages pivot point 65 and a corresponding receiving aperture in breech arrangement 50. Thus, breech 60 is allowed to pivot in a plane orthogonal to the longitudinal axis of breech arrangement 50. The axis of rotation is generally parallel to the longitudinal axis of the breech arrangement.

As shown in Fig. 7, pivot 65 allows breech 60 to be opened in order to insert a cartridge 10. Breach 60 can then be closed so that chamber 62 is aligned with barrel 40.

A spring biassed locking pin (not shown) engages receiving aperture 66 to lock breech 60 in the closed position.

Sealing means may be provided on breech 60 or breech block 50 such that the firing chamber has an effective air seal when in the closed position.

An alternative breech arrangement is shown in Figs. 810, using corresponding numbering. A hinged breech block fits into gap 51 and is hinged by a pivot bar through aperture 65. For ease of manufacture, a protruding end of the pivot bar may be bent over and located in a recess in coupling portion 54 between the breech and the barrel (not shown).

Referring to Figs. 8 and 10, the breech body has a sloping portion 55 which co-operates with the breech block to force the cartridge into the firing chamber, against the reaction of the ejector mechanism.

An angled port 52, at about 30 degrees, leads from a valve mechanism (not shown) to an axial opening 53 of around 3-4mm in length. When the breech is in the closed position, opening 53 is substantially aligned with the wad 30 at the rear of cartridge 10 (see also Fig.s 1-3). The angled port 52 increases firing pressure by as much as 50% compared with the right-angled port of Fig. 6. This is particularly beneficial at high pressures such as 70 to 80 foot-pounds.

Figures 11 and 12 show an alternative breech block. As in Fig.s 4 and 5, a cartridge is inserted with rim 22 lying in enlarged section 64. An internal sleeve 66 is biassed by spring 67 to eject the cartridge. The breech is held closed by closure lever 68, the end of which engages recess 66 of the breech body 50 (see also Fig. 8).

Fig. 13 shows a second embodiment of the cartridge, wherein the rim 22 also protrudes inwardly into the housing to inhibit the wad 30 from coming readwardly out of the housing. This creates a void 36 which improves performance by allowing a buildup of gas in the housing and behind the wad 30.

Fig. 14 shows a firing bolt 70 in the rest position after firing. Fig. 15 shows the bolt 70 with finger arm 71 rotated to lie in safety recess 72 of longitudinal guide slot 73. In this position the bolt is cocked but may not fire until first rotated so that arm 71 is in line with the main portion of guide slot 73.

Fig.s 16-18 show a remainder of the trigger mechanism.

Ball 74 is coupled to bolt 70. In the position shown in Fig.

16, bolt 70 has been drawn back such that ball 74 is located in a cup in cup lever 75. Cup lever 75 is spring biassed and held in place by catch lever 76. F-bar 80 is pivoted such that shear bar portion 81 rests against catch lever 76.

The F-bar is one integrally formed piece comprising shear bar 81, vertical bar 82, horizontal bar 83 and finger bar 84. Movement of F-bar 80 by finger pressure on trigger 84 causes shear bar 81 to move catch lever 76, thus releasing cup lever 75 and so bolt 70, which can then strike a valve mechanism to release pressurised gas.

The cartridge described herein has a number of advantages over prior art powder cartridges. Firstly, since an air propulsion system is used, there is relatively low noise. Reduced noise pollution is desirable, particularly for sports shooting. Also, a live target is less likely to be startled or disturbed by shots being fired and the position of the firer is less easily determined. Air powered weapons have low recoil compared with powder firearms, which increases user safety.

By choosing appropriate materials for the projectile, environmental impact can be reduced. For example, the projectile can be made of a readily biodegradable plastics material. Since plastics material components are used in the cartridge, it is significantly cheaper to produce and to manufacture than prior art metal-cased powder cartridges.

Further, the present cartridge is inert and not in itself dangerous. The cartridge is highly resistant to excess heat and moisture.

The breech arrangement described herein also has a number of advantages over prior art breech arrangements, such as a bolt breech. The hinged breech described herein is readily disassembled for cleaning and maintenance. The hinged breech allows spent cartridges to be removed relatively easily and new cartridges loaded. Since only a relatively small portion of the breech moves, the pivoting action is relatively reliable and may be made from relatively small and cheap components.

Claims (15)

1. A cartridge for an air-gun, comprising: a cartridge housing; and a projectile locatable within the housing, said projectile for being expelled by compressed gas applied to said housing, said projectile comprising a wad or wad portion for forming a seal with the housing as the projectile is expelled and a travelling portion intended to travel furthest and hit a target.

2. A cartridge as claimed in claim 1, wherein said wad is located rearmost in the housing to push the projectile during expulsion.

3. A cartridge as claimed in claim 2, wherein said travelling portion comprises a plurality of shot pellets.

4. A cartridge as claimed in claim 2 or 3, wherein said wad comprises a disc or cylinder of compliant material.

5. A cartridge as claimed in claim 2 or 3, wherein said wad comprises an elongate body portion having a disc or discs radiating therefrom.

6. A cartridge as claimed in claim 5, wherein said wad comprises an elongate body portion having one disc radiating from either end.

7. A cartridge as claimed in claim 2 or 3, wherein said wad comprises a tubular body closed at one end.

8. A cartridge as claimed in claim 7, wherein said wad is arranged in the housing with the closed end of the body foremost so that, in use, compressed air applied to the rear of the housing forces the walls of the body into a sealing abutment with the interior of the housing.

9. A cartridge as claimed in claim 8, wherein said body also comprises an external sealing ring portion.

10. A cartridge as claimed in any preceding claim, comprising means for operatively retaining the projectile at a desired location within the housing.

11. A cartridge as claimed in claim 10, having stop means comprising an inwardly protruding lip formed at the rear of the housing to inhibit the projectile from moving rearwardly out of the housing.

12. A cartridge as claimed in claim 11, wherein said stop means is arranged to leave a void between the rear of the projectile and the rear of the housing.

13. A cartridge as claimed in claim 11, having retaining means comprising a sealing membrane, such as of paper or plastics material, or alternatively a readily detachable web, mesh or disc, suitably of plastics material, across a forwardmost end of said housing.

14. A cartridge as claimed in any preceding claim, comprising a lip portion protruding radially outward at or near the rear of the housing.

15. A cartridge substantially as hereinbefore described with reference to the accompanying drawings.