Mechanical guns and projectors – Fluid pressure – With control for discharge of fluid pressure
Patent
1987-07-13
1989-09-12
Reese, Randolph A.
Mechanical guns and projectors
Fluid pressure
With control for discharge of fluid pressure
124 73, 124 70, F41B 1100
Patent
active
048650099
DESCRIPTION:
BRIEF SUMMARY
This invention relates to guns, and especially to guns that utilize gas or air to propel a pellet or other projectile.
Airguns that rely upon a compressed air cylinder to provide the propulsive discharge have been known for many years. These guns are popular because there is virtually no recoil and therefore no loss of concentration, which is often an effect on the user of gun recoil. However a problem with airguns operated by progressive discharge of a compressed air cylinder is in achieving consistency in the propulsive force which varies as the air cylinder discharges.
A typical prior art airgun comprises a rechargeable cylinder with a valve through which air is discharged to propel the pellet. The valve is of a type where the sealing surface is pushed into the air cylinder in response to the trigger to open the valve and the closure is effected by the pressure from within the air cylinder reseating the valve. The time for which the valve is open, and thus the level of gas discharge depends upon various factors but in particular the pressure within the air cylinder. In fact the pressure within the cylinder has several effects; with the high pressure of a newly filled cylinder the pressure within the cylinder resists the valve opening for longer, then while the valve is open relatively high pressure air discharges and finally the valve is urged closed earlier, with the overall result that a short relatively high pressure burst of air is discharged; with a nearly discharged cylinder in which the pressure is relatively low the valve opens earlier, the escaping air is of lower pressure and the valve closes later so that a longer relatively low pressure burst of air is discharged. Attempts have been made to balance the system by adjusting the valve area in order to provide greater equality between the masses of discharged air but these do not overcome the difference in the nature of the high and low pressure bursts and so, in terms of consistency of performance, the compressed air cylinder airgun is as yet not comparable with, for example, a mechanical spring gun. Thus the choice is either to use a mechanical pressurizing system for consistent projectile force but suffer recoil or use a compressed air cylinder gun and modify aim to compensate for the discharge characteristics.
Guns are available that operate on liquid gas cylinders, notably carbon dioxide, and of course for a given temperature the pressure within a liquid gas cylinder remains constant as long as there is some liquid still present. Therefore recoil free liquid gas guns, of similar structure to airguns, are available and these have (at constant temperature). the advantage of consistency by virtue of a liquid carbon dioxide cylinder replacing the compressed air cylinder. However these guns suffer from considerable temperature dependence there being a variation of as much as 100 psi (689 kNm.sup.-2) in the liquefaction pressure between hot and cold days which gives inconsistency under varying temperature conditions. Also, in some countries these gasguns are classified as firearms, for example in the U.K. they are classified under Section 1 of the Firearms Act and therefore they have to be licensed.
The present invention is directed towards providing a gun of compressed gas cylinder type with consistent discharge characteristics. Within the context of this specification `compressed gas` means gas that is pressurized but not liquified and `pressurized` is used to imply both gas that is compressed and also gas that is liquified under pressure.
Accordingly the present invention provides a gun comprising a discharge chamber for holding compressed gas, means for discharging gas from the discharge chamber to propel a projectile, and means for compressing gas in the discharge chamber to a predetermined pressure between successive discharges, said means comprising a pressurized gas chamber adapted to hold gas at a pressure at least equal to the particular predetermined pressure.
In a first embodiment the means for compressing gas comprises a valve interc
REFERENCES:
patent: 645932 (1900-03-01), Beck et al.
patent: 2594240 (1952-04-01), Wells
patent: 3204625 (1965-09-01), Shepherd
patent: 4572152 (1986-02-01), Olofsson et al.
patent: 4616622 (1986-10-01), Milliman
Cardew Gerald V.
Ford John B. M.
Knight Anthony
Reese Randolph A.
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