GB2372552A - Airgun regulators - Google Patents

Abstract

An air regulator for an airgun comprises a body 2 having a first connection point 201 for connection to a source of compressed air, and a second connection point 202 for connection to an air transfer port of an airgun. A cylinder 210 extends between the first and second connection points 201, 202, and a piston 3 is mounted for sliding movement in it. Spring discs 5 bias the piston 3 resiliently towards an end position. The piston 3 has three stepped portions 311, 312, 313 that engage within corresponding stepped bores 211, 212, 213. A passageway 301, 302 connects the cylinder portions 311, 312, such that high pressure air introduced into the cylinder 210 prevails at both cylinder portions 311, 312, which present different surface areas to the high pressure air, to create forces on the piston 3 in opposing directions. The spring discs 5 supplement one of those opposing forces. Such airgun regulators may be made relatively simply of a convenient size, utilising a relatively light spring, whilst still operating very reliably and efficiently.

Description

AIRGUN REGULATORS

This invention relates to airguns and is concerned particularly with airgun regulators.

Modern airguns are designed to operate by metering a controlled amount of high pressure air into the gun barrel behind the pellet or other projectile. Typically, the air is provided from a reservoir of compressed gas at high pressure. A regulator is highly desirable, in order to present the air to the pellet at a reasonably constant pressure.

Known air regulators comprise a piston which operates against the resilient bias of a spring, in order to close a valve which controls the supply of air from a reservoir. This spring biases the valve into an open position, such that high pressure air can enter a cylinder from the reservoir. The high pressure air acts on the piston in the cylinder to close the valve against the resilient bias of the spring. Put simply, when the pressure in the cylinder is high enough, at or about a predetermined value, it overcomes the spring pressure to close the reservoir valve.

In recent years, the design of air regulators has steadily improved, such that they operate quite reliably. However, to make the regulator of a practicable size, both the piston and the. spring tend to be quite substantial items, due to the high pressures involved. Equally, because of the high pressures, to utilise a lighter spring necessitates making the whole regulator of an inconveniently small size, which is relatively difficult to manufacture.

Preferred embodiments of the present invention aim to provide airgun regulators which may be improved in this respect, and can be made relatively simply of a convenient size, utilising a relatively light spring, whilst still operating very reliably and efficiently.

According to one aspect of the present invention, there is provided an air regulator for an airgun, the regulator comprising: a. a body; b. a first connection point on the body, arranged for connection to a source of compressed air; c. a second connection point on the body, arranged for connection to an air transfer port of an airgun; d. a cylinder extending between said first and second connection points ; e. a piston mounted for sliding movement in said cylinder; and f. resilient bias means for biasing said piston resiliently towards a first end position in said cylinder: wherein said piston comprises: i. a first portion closest to said first connection point; ii. a second portion closest to said second connection point; and iii. a passageway that connects said first and second portions : such that: (1) high pressure air introduced from said source into said cylinder passes through said passageway to prevail at said first and second piston portions, to

create forces on said piston in opposing directions ; (2) said first and second piston portions present different surface areas to said high pressure air; and (3) said resilient bias means supplements one of said forces in one of said opposing directions.

Preferably, when in said first end position, said piston is operative directly or indirectly to shut off the supply of compressed air from said first

.. connection point.

Preferably, said cylinder and said piston have corresponding stepped portions of different diameters.

Preferably, said passageway extends substantially between opposite ends of the piston.

Preferably, said first and second connection points are at or adjacent respective opposite ends of said body.

Preferably, said cylinder is vented to atmosphere or other reference pressure source at a point between said first and second piston portions.

Said resilient bias means may comprise a series of spring elements and means for compressing said elements.

Preferably, said body is elongate.

Preferably, said body is substantially rectilinear.

The invention extends to an air regulator according to any of the preceding aspects of the invention, in combination with a source of compressed air for attachment to said first connection point.

Preferably, said source of compressed air comprises an air bottle.

Said body may be constructed integrally with said source of compressed air.

The invention extends to an airgun provided with an air regulator according to any of the preceding aspects of the invention.

Said body may be constructed integrally with a part of said airgun.

It will be appreciated by those skilled in the art that, although air is typically used as a propellant in airguns, any suitable compressed gas may be used. Therefore, in the context of this specification, the term"air"is to be construed to include any gas that is capable of being compressed and use to propel a projectile in a gun or rifle.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 shows one example of an airgun regulator in longitudinal section ; and Figure 2 illustrates the regulator fitted to an air rifle.

The illustrated airgun regulator 1 comprises a body 2, a piston 3, a bottle adapter 4 and a set of spring discs 5. Also shown in Figure 1 are a sealing member 6, 0-rings 7 and 8, a circlip 9 and a nut 10. Typically, the body 2, the piston 3 and the bottle adapter 4 are machined of stainless steel; the spring discs 5 are of spring steel; the sealing member 6 is of a hard plastics material, the 0-rings 7 and 8 are of elastomeric materials, the circlip 9 is of spring steel and the nut 10 is of steel, brass or any suitable metal.

The body 2 is formed at one end with a tapped bore 201 which affords a first connection point for an air bottle-that is, a bottle containing pressurised gas. The bottle adapter 4 is engaged and secured at an inner end of the bore 201, with the 0-ring 8 providing a gas-tight seal between an end wall of the bore 201 and an opposing face of the bottle adapter 4.

In use, an air bottle 12 is screwed into the bore 201. A spigot 401 on the bottle adapter 4 engages a corresponding nozzle at the end of the bottle, to engage a valve and release compressed air from the bottle. Compressed air from the bottle enters a passageway 402, one end of which is afforded by a radial bore in the spigot 401 and the rest of which is provided by an axial bore in the bottle adapter 4. The manner in which the bottle adapter 4 engages an air bottle valve is generally known to those skilled in the art, and therefore requires no further detailed description here.

At an opposite end, the body 2 is provided with an externally threaded portion 202 which affords a second connection point for connection to an airgun. In this respect, the airgun is provided with a corresponding tapped bore with which the externally threaded portion 202 engages, such that the body 2 as a whole can be screw-threadedly engaged with the airgun. Again, those skilled in the art will be familiar with the way in which a regulator engages with an airgun, so a further detailed description need not be provided here.

The body 2 is provided with two or more flats 203 at the"bottle end", for engagement with a tool to facilitate or inhibit rotation of the body 2. Likewise, the body 2 is provided with two or more flats 204 at the"gun end".

At the gun end, the body 2 is formed with a series of stepped, coaxial bores 211,212 and 213, which define a cylinder 201 in which the piston 3 is mounted for sliding movement. By way of an example, the bore 211 may have a diameter of 6mm, the bore 212 a diameter of 9mm and the bore 213 a diameter of llmm.

The piston 3 is formed with three correspondingly stepped portions 311,312 and 313, which engage within the bores 211,212 and 213 respectively.

The piston portions 311 and 312 engage the respective bores 211 and 212 with a close fit, and the 0-rings 7 provide sealing between the respective portions of the piston 3 and the cylinder 210.

Once the piston 3 has been inserted in the cylinder 210 during assembly of the regulator 1, the circlip 9 is engaged in an annular recess formed in the body 2, to retain the piston 3 within the cylinder 210 by bearing against an end face 314 of the piston portion 313.

Once the piston 3 has been assembled and retained within the cylinder 201, the spring discs 5 are placed on an end portion 315 of the piston 3, where they bear at one end on an end face 214 of the body 2 and are retained in place at an opposite end by the nut 10 which engages a screwthread on the end portion 315, such that the spring discs 5 are compressed to a desired degree.

It will appreciated that, in this condition, the resilient bias of the spring discs 5 operates to urge the piston 3 to the right as seen in Figure 1, away from the bottle adapter 4. By adjusting the strength and number of the spring discs 5, and the degree to which they are compressed by the nut 10, the operating pressure of the assembly of spring discs 5 can readily be adjusted.

At the bottle end, the piston 3 carries the sealing member 6, which is arranged to bear against a valve seat 403 formed on the bottle adapter 4, in order to open and close the passageway 402 which provides communication between the air bottle and the gun.

The piston 3 is formed with a central, longitudinal bore 301 which communicates with two or more radial bores 302 to afford a passageway for communication between the opposite ends of the piston 3.

A radial bore 205 in the body 2 affords communication between the ambient atmosphere (or any other external reference pressure) and the second bore 212, at a point between the 0-rings 7.

The regulator 1 operates very simply and effectively as follows.

With a replaceable bottle 12 engaged with the bottle adapter 4, high pressure air passes from the bottle 12 through the passageway 402 to enter the cylinder 210. Due to the passageway afforded by the bores 301, 302, the high pressure air is rapidly established at both ends of the piston 3.

Due to the sealing provided by the 0-rings 7, the forces acting on the piston 3 to urge it to the right as seen in Figure 1 are the spring force of the spring discs 5, the high pressure air acting on the first piston portion 311 (diameter 6mm), and atmospheric pressure acting on the annular surface 215 at the step between the first and second piston portions 311, 312. The force acting on the piston to the left as seen in Figure 1 is the high pressure air acting on the difference in effective surface areas between the first and second piston portions 311 and 312.

Thus, when the high pressure prevailing at both ends of the piston 3 is sufficiently high, the differential force due to the difference in crosssectional areas of the first and second piston portions 311, 312, which are subjected to the high pressure, causes the piston 3 to be urged to the left until the sealing member 6 bears firmly against the valve seat 403 to close the passageway 402. (At this point, the pressure in the bottle then acts on the sealing member 6 over the cross-sectional area at the opposing mouth of the passageway 402.)

When a sequence for firing the respective airgun is initiated, a metered amount of the high pressure air at the gun end of the piston 3 is passed via a transfer port into a breech of the gun, to be presented to the pellet or other projectile, which is then fired. Consequently, the pressure prevailing around the piston 3 drops slightly, allowing the piston 3 to be moved slightly to the right, in order to open the passageway 402 until the pressure around the piston 3 is again restored to its predetermined level, at which the passageway 402 is again closed by the sealing member 6 bearing against the valve seat 403.

In experiments, it has been found that an airgun regulator constructed as illustrated may operate very rapidly, reliably and accurately. Moreover, it may be very easily manufactured to relatively small dimensions, in order that it may be easily incorporated in many different models of airguns.

It will be appreciated that, by making use of the differential surface areas of the piston portions 311 and 312, which are subject to the pressure prevailing around the piston 3, a spring force to urge the passageway 402 open may be very significantly less than in conventional arrangements, where a strong spring force has been set against a correspondingly strong force from a simple piston. This improved effect is achieved by providing the passageway via the bores 301,302 which allows the same pressure to prevail at both ends of the piston 3.

As indicated above, the pressure setting at which the device 1 regulates the gun pressure can be adjusted quite simply, by varying the number and strength of the spring discs 5, and the extent to which they are compressed by the nut 10.

By way of example, it has been found that a regulator constructed as illustrated may regulate an air bottle pressure of 3, 000 psi rapidly and effectively to a working pressure of 1,250 psi, to within an accuracy of 50 psi. This affords a high degree of accuracy in shooting, by ensuring that each shoot is taken at a substantially constant air pressure.

Particularly with a significant pressure differential between bottle and gun, it is advantageous if the mean diameter of the passageway 402 is less than that of passageway afforded by the bores 301 and 302. In this way, as the pressure in the bottle falls with use, the variation in force experienced by the sealing member 6 from the bottle pressure is proportionally less.

By way of example, the passageway 402 may comprise bores of 1 mm diameter; the radial bores 302 may have a diameter of 1.5 mm and the main longitudinal bore 301 may have a minimum diameter of 2.5 mm.

Preferably, the cross sectional area of the passageway in the piston 3 is at least 1.5 times, and preferably 2 times, that of the passageway 402.

In an alternative arrangement, the passageway 402 is provided with a valve that closes under pressure from the air bottle 12, and the cylinder 210 and piston 3 are effectively reversed in direction so that, under the influence of high pressure, the piston is urged away from the passageway 402. Upon the pressure around the piston 3 dropping, it is urged under

r esi 1 resilient bias towards the passageway 402, to open the valve in the passageway 402.

A further advantage of the illustrated example is that, by providing atmospheric pressure at a point between the piston portions 311 and 312,

this can be achieved by a simple drilling from one side of the body 2, without any additional sealing requirements.

The smaller the difference in cross-sectional areas between the piston portions 311 and 312, the lighter the spring force afforded by the spring discs 5 (or other resilient bias means) can be.

In the illustrated arrangement, if for any reason the valve seal at the valve seat 403 were to leak slightly, for example due to contamination, then the more the pressure builds up within the vicinity of the piston 3, the harder the sealing member 6 would be urged against the valve seat 403, thereby operating in a fail-safe manner.

It is to be noted that, when the bottle pressure falls significantly to about the regulated pressure or below, the passageway 402 remains open, thereby allowing a number of shots to be taken, before the pressure falls to too low a level. This contrasts with other previously proposed regulators where the bottle pressure is shut off completely, once it falls below regulated pressure.

Should it be desired to operate at a higher pressure-e. g. 2000 psi, then it is necessary simply to increase the strength and/or number of the spring discs 5.

Figure 2 illustrates the regulator 1 when fitted in an airgun. The regulator 1 is mounted in the stock 11 of an air rifle and receives the air bottle 12 containing compressed air. The gun side of the regulator 1 is connected to the breech of a barrel 14 by an air transfer port 13.

Although in the example illustrated in Figure 1, the regulator 1 is made to fit detachably to a respective airgun and to receive a detachable bottle, in alternative embodiments, the regulator can be built integrally into an air bottle 1 (or other source of compressed gas), or an airgun, or both.

In this specification, the verb"comprise"has its normal dictionary meaning, to denote non-exclusive inclusion. That is, use of the word "comprise" (or any of its derivatives) to include one feature or more, does not exclude the possibility of also including further features.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (15)

1. An air regulator for an airgun, the regulator comprising : a. a body; b. a first connection point on the body, arranged for connection to a source of compressed air; c. a second connection point on the body, arranged for connection to an air transfer port of an airgun; d. a cylinder extending between said first and second connection points ; e. a piston mounted for sliding movement in said cylinder; and

L I L 1 1 1 f. resilient bias means for biasing said piston resiliently towards a first end position in said cylinder: wherein said piston comprises : i. a first portion closest to said first connection point; ii. a second portion closest to said second connection point; and iii. a passageway that connects said first and second portions: such that: (1) high pressure air introduced from said source into said cylinder passes through said passageway to prevail at said first and second piston portions, to create forces on said piston in opposing directions; (2) said first and second piston portions present different surface areas to said high pressure air; and

(3) said resilient bias means supplements one of said forces in one of said opposing directions.

2. An air regulator according to claim 1, wherein, when in said first end position, said piston is operative directly or indirectly to shut off the supply of compressed air from said first connection point.

3. An air regulator according to claim 1 or 2, wherein said cylinder and said piston have corresponding stepped portions of different diameters.

4. An air regulator according to claim 1,2 or 3, wherein said passageway extends substantially between opposite ends of the piston.

5. An air regulator according to any of the preceding claims, wherein said first and second connection points are at or adjacent respective opposite ends of said body.

6. An air regulator according to any of the preceding claims, wherein said cylinder is vented to atmosphere or other reference pressure source at a point between said first and second piston portions.

7. An air regulator according to any of the preceding claims, wherein said resilient bias means comprises a series of spring elements and means for compressing said elements.

8. An air regulator according to any of the preceding claims, wherein said body is elongate.

9. An air regulator according to claim 8, wherein said body is substantially rectilinear.

10. An air regulator substantially as hereinbefore described with reference to the accompanying drawings.

11. An air regulator according to any of the preceding claims, in combination with a source of compressed air for attachment to said first connection point.

12. An air regulator according to claim 11, wherein said source of compressed air comprises an air bottle.

13. An air regulator according to claim 11 or 12, wherein said body is constructed integrally with said source of compressed air.

14. An airgun provided with an air regulator according to any of the preceding claims.

15. An airgun according to claim 14, wherein said body is constructed integrally with a part of said airgun.