GB2160299A - Air gun - Google Patents

Abstract

A gun for firing a projectile such as a dart under air pressure, comprises a breech 12 for the projectile, a barrel 10, a chamber 20 for compressed air, a reservoir 24, a trigger 30 for charging the chamber with pressurised air from the reservoir, a trigger 42 for firing the projectile, and a telescopic sight 18 incorporating a focussing element controllable by the pressure in the chamber 20. The pressure in the chamber 20 is lowerable to adjust the focusing element prior to firing by means of a bleed button 40. The correct firing pressure is achieved when the target is in focus, this being just sufficient for the dart to arrive at target with sufficient energy to penetrate an animal's hide without killing. <IMAGE>

Description

SPECIFICATION A gun Field of the Invention This invention relates to a gun, and in particular to an air gun which may be used to fire a dart or other projectile for the purpose of immobilising an animal. Such guns are required by veterinary surgeons to enable them to immobilise their patients before treating them.

The propellant which fires the projectile will be referred to in this specification as "air".

Although air is likely to be the predominantly used propellant, it would be possible to use other gases, and the term "air" as used in this specification is to be taken as including other gases.

Background to the Invention Veterinary surgeons have to be capable of dealing with a wide variety of animals having different physical characteristics. The shooting of an immobilising dart into the skin ofan animal is a known technique, and in this technique it is important that the dart should penetrate the animals hide, but it should not be fired with such force that it might possibly kill the animal.

Because different species of animals have different thicknesses of hide, it is necessary for the surgeon to exercise his judgement as to how far he needs to be from the animal before he fires the dart, taking into account what he knows of the firing characteristics of the gun.

Summary of the Invention According to the present invention, there is provided a gun for firing a projectile by air pressure, the gun comprising a breech for receiving a projectile, a barrel, a charge chamber for storing compressed air, means for varying the pressure of the air in the charge chamber, means for admitting compressed air from the charge chamber into the breech to fire the projectile, a telescopic sight having a focussing element, and a pressure sensitive transducer sensitive to the pressure in the charge chamber and adapted to move the focussing element in response to changes of pressure in the chamber.

By varying the pressure of the air used to fire the projectile, the energy imparted to the projectile can be varied. Normally a greaterpressure will be needed when firing at a greater distance from the animal than will be needed when firing at a lesser distance from the animal.

To avoid the necessity of having to make calculations about distance and pressure, the focussing element of the telescopic sight is interlinked with the pressure in the charge chamber. Thus, the target animal can be viewed through the sight and then air can be vented from the charge chamber thus reducing the pressure. As the pressure in the chamber drops, so the focussing element of the telescopic sight moves, and the gun will be set up so that when the sight focusses on an animal at a particular distance from the gun, the air pressure in the charge chamber will be at the necessary level to fire a projectile at the target animal with sufficient velocity to pierce the animals hide, but to do no further damage.

Thus, the user of the gun needs to make no special calculations. All he does is aim, focus and fire.

In practical terms, the operator may operate a bleed valve which bleeds air from the charge chamber, and as the pressure drops so the focus of the sight will change.

The gun may include a pressure reservoir, and means for charging the reservoir with compressed air, as well as a connection between the reservoir and the charge chamber which is under the control of a valve operated by a printing trigger.

Both the reservoir and the charge chamber may be formed as annular casings surrounding the gun barrel.

There is preferably a damper mechanism between the charge chamber and the pressure sensitive transducer so that, when the gun is fired and the pressure in the charge chamber drops sharply, the transducer is not immediately effected in a sudden fashion.

A silencer may be fitted around the barrel near the open end thereof.

The gun may have two handles; one of these may be a The gun may have two handles; one of these may be a conventional stock, with a firing trigger arranged to be operated while holding the stock. The second handle may be nearer the open end of the barrel and may include a priming trigger which allows compressed air to pass from the reservoir to the charge chamber, and an air bleed button which allows air to bleed out of the charge chamber.

The invention will now be further-described by way of example, with reference to the accompanying drawing, which is a schematic side view of a gun in accordance with the invention.

The gun has a barrel 10 which, at its lefthand end has a breech 12 for receiving a projectile. The breech will be openable for insertion of the projectile, but details of the necessary mechanism are not shown. The gun will be held in the firing pbsition by its user who will hold a first handle or stock 14 and a second handle 16. A telescopic sight 18 is mounted above the barrel. Around the barrel 10 are mounted three annular chambers. A charge chamber 20 is nearest the breech 1 2.

A silencer 22 is at the opposite end of the barrel and a reservoir chamber 24 is in the middle. All of these chambers are separate from one another, although they are connected by various air passages which will be described.

In operation, the reservoir 24 is first charged with compressed air. This is done by means of a priming pump 26 operated by a handle 28. The handle 28 moves a piston in the pump 26 and this pumps air into the reservoir 24. Some form of gauge may be provided to indicate when the reservoir is fully charged. A dart or other projectile is then placed in the breech 12, and the gun is primed by pressing a priming trigger 30 which opens a valve 32 and allows compressed air to pass from the reservoir 24 through passages 34 and 36 to the charge chamber 20. When the priming trigger is released, compressed air is trapped inside the charge chamber.

The gun is then aimed at its target, and the target is sighted through the sight 18. Initially the sight will be set so that it focusses on a point at the extreme range of the gun. Assuming that the actual target is somewhere within this range, the focus of the sight 18 must be shortened. The focussing element in the sight is controlled by pressure, and in particular by the pressure in the charge chamber 20 to which the sight is connected through a passage 38. In order to alter the focus on the sight 18, it is therefore necessary to reduce the pressure in the charge chamber 20 and this is done by pressing a bleed button 40 which is connected to the air valve 32. Pressing the button 40 allows air to pass from the charge chamber through the passage 36 to atmosphere, in a controlled manner.Thus, as the bleed button 40 is held down, the compressed air pressure in the chamber 20 will gradually reduce and this will have an effect on the focussing element of the sight 18. The user will continue to watch his target through the sight 18, and once the target is completely in focus he will release the bleed button 40. At this stage, the pressure in the chamber 20 will be just the pressure needed to propell the dart to its target and to arrive at the target with sufficient energy to penetrate an animal's hide.

The gun can then be fired. This is done by pulling a firing trigger 42 which opens a valve 44 in a passage 46. Opening the valve 44 allows the pressure from the charge chamber 20 to reach the back of the projectile, and to propell the projectile along the barrel and to its target.

Clearly when this happens the pressure in the charge chamber 20 drops suddenly. To prevent this having an adverse effect on the telescopic sight 1 8 which is controlled by this pressure, a throttle or damper 48 will be included in the passage 38 so that the pressure acting on the focussing element of the sight would only move relatively slowly.

To prevent an undue amount of noise arising when the gun is fired, a silencer 22 is mounted at the end of the barrel. This communicates with the barrelthroUgh holes in the barrel wall, and provides a sinciflg effect in a known manner.

The gun therefore makes it very easy to control the speed with which the dart is fired in accordance with the distance of the user from the target. No special knowledge or experience is required, because correct setting up of the gun itself will automatically fire the dart at the correct speed.

Claims (10)

1. A gun for firing a projectile by air pressure, the gun comprising a breech for receiving a projectile, a barrel, a charge chamber for storing compressed air, means for varying the pressure of the air in the charge chamber, means for admitting compressed air from the charge chamber into the breech to fire the projectile, a tele'scopic sight having a focusing element; and a pressure-sensitive transducer sensitive to the pressure in the charge chamber and adapted to move the focusing element in response to changes of pressure in the chamber.

2. A gun according to claim 1, including means for venting air from the chamber to reduce the pressure therein and thus adjust the focusing element.

3. A gun according to claim 2, wherein said venting means is a bleed valve.

4. A gun according to any of claims 1 to 3, including a pressure reservoir, means for charging said reservoir with compressed air and a valve-controlled connection for supplying air from the reservoir to the charge chamber.

5. A gun according to claim 4, wherein said valve is operable by a priming trigger.

6. A gun according to claim 4 or claim 5, wherein said reservoir and charge chamber are formed as annular casings surrounding the gun barrel.

7. A gun according to any of claims 1 to 6, including a damper mechanism between the charge chamber and the transducer.

8. A gun according to any of claims 1 to 7, including a silencer fitted around the barrel adjacent to the open end thereof.

9. A gun according to any of claims 1 to 8, having two handles, are in the form of a conventional stock, with a firing trigger operable while holding the stock, and the other in the form of a priming trigger located nearer the open end of the barrel than the firing trigger.

10. A gun for firing á projectile by air pressure, substantially as hereinbefore described with reference to the accompanyinJ drawings.