GB2071827A - Improvements in or relating to air guns - Google Patents

Abstract

A mechanism for an air gun uses carbon fibre reinforced composite material in the form of two arms stressed from a planar form to the bowed state, in which state considerable potential energy is stored, and held in this state by a sear (not shown) engaging piston a piston secured to the arms. In the embodiment of Fig. 8, a piston 2 is coupled to the ends of arms 6a, 6b through toggle linkages 5a, 5b through which arms energy is transmitted to the piston on release of the stressed arms to force same along the cylinder 1 communicating by orifice 3 with the gun barrel. The arms are stressed by first drawing back connection blocks 20 along guide 22 with attendant movement back of the arms and piston and thereafter forcing blocks 20, 22 forward whilst holding the piston to bow and stress the arms. The arms preferably are shaped in profile and section to impart a required force/distance characteristic to the piston. In an embodiment of Figure 5, arms 6a and 6b are coupled at their rear ends to blocks 7a, 7b pivoted at 8a, 8b. In operation a block 9, pivoted to the block 7a, 7b through links 10a, 10b, is moved rearwardly to allow the arms 6a and 6b to diverge. At this point the piston is restrained and the block moved forward to stress the arms to the bent position shown and secured against movement. Release of the piston causes it to move forward through the cylinder 1 under the force of the bent arms. <IMAGE>

Description

SPECIFICATION Improvements in or relating to air guns This invention relates generally to air guns and more particularly is concerned with a mechanism for incorporation therein to produce rapid compression of air to propell the pellet through the barrel. Known constructiion of air guns excluding those termed "pump action" in which a reservoir cylinder is used to store compressed air through a pumping means and CO2 gas guns, comprise a piston assembly which is held in a cocked condition against the power of a compression spring, and on discharge of the weapon the piston is moved down a cylinder producing compression of the air which is conducted to the rear of the pellet so as to move same down the barrel.

In such a construction the travel of the piston is relatively long and this means that the air compression process tends to be fairly gradual in build up. The inertial mass of the piston spring assembly is also fairly large and this energy must be absorbed at the end of the stroke. In most cases there is considerable rebound of the piston resulting in inaccuracy of aim.

It is an object of this invention to provide a compressed air mechanism for an air gun which avoids the use of a helical compression spring with the associated long travel of the piston, and which can preferably be constructed to as to be generally "recoilless".

Another object is to provide a mechanism which, in the unloaded or uncocked state, has not parts subject to compression thus avoiding the likelihood of injury if the weapon is dismantled.

According to this invention there is provided an air gun, or an air compression mechanism for an air gun, with a piston movable in a cylinder to provide compression of air for propelling a projectile along a barrel of the gun, the piston being operatively coupled to the one end or ends of one or more longitudinally inextensible but flexurally resilient arms, the other end or ends of the or each arm being fixed relative to the cylinder, a cocking mechanism operative to draw back the piston relative to the cylinder and to further cause relative displacement whereby the arm or arms are flexurally stressed to bow and a firing means to hold the piston against the force of the stressed arms and release same on operation of a trigger mechanism.

Preferably two arms are provided in side by side relationship and arranged on opposed sides of a medial longitudinal plain, the arms being coupled to bow in opposed senses.

With the arms lying generally longitudinally of the gun and bowing outward reaction forces are substantially cancelled out.

The lateral forces cancel with such an arrangement and there is little recoil force in view of the small masses moving longitudinally.

The arms preferably but not essentially are straight and lie in spaced parallel configuration when unstressed and form a mechanism in axial alignment with the piston and cylinder. When incorporated within a gun the mechanism may be arranged to lie parallel with the barrel axis. In such an arrangement considerable potential energy is stored with relatively small flexural displacement of the arms leading to a short stroke of the piston which may be designed in an optimum manner with optimum (over square) bore to stroke ratio. This provides very rapid pressure buildup on discharge accompanied by little movement.

The motion of the piston is arrested by the arms themselves avoiding piston bounce. The arms are preferably arranged to bow inwardly at their medial portions during stressing.

The piston is preferably coupled to the end of each arm through a toggle linkage whereby the arms are, in one embodiment, parallel when uncocked and diverge, by virtue of the toggles, at their ends coupled to the piston, to a V-shape configuration with associated pivotal deflection of mounting means securing the other ends of the arms, when the piston is drawn back in the cylinder or, in a second embodiment, are divergent outward at the other ends from the toggles when uncocked and are caused to bow to a more parallel configuration by virtue of the toggles when cocked, the other ends of the arms being securly held in a mounting means. An actuating mechanism operative on the mounting means causes the other ends of the arms to be brought to coplanar relationship in the first embodiment thus effecting stressing and applying force to the piston through the toggles.

In the second embodiment the mounting means with the ends of the arms is moved forwardly to effect stressing, with the toggles pivoting outwardly.

The arms are of a composite such as a carbon fibre reinforced material and may be shaped in section and profile to provide a required characteristic of force to displacement of the piston, taking into account the mechanical leverage of the toggles. In this way a more favourable distribution of compression can be obtained during discharge as against a helical spring in which force diminishes towards zero as the end of the stroke is approached.

Two embodiments of air compression mechanisms designed for incorporation into an air rifle are shown by way of example in the accompanying drawings which, to a certain extent, are diagrammatic.

In the drawings: Figure 1 shows a plan view of the mechanism of a first embodiment in an uncocked position after firing, Fipt!re 2 shows a side view of the mechanism (together with the cocking lever) in the condition as shown in Fig. 1, Figure 3 shows a detail of the ends of the arms remote from the piston when the piston is brought back in the cylinder to a cocked state without flexure of the arms, Figure 4 shows a detail of the piston and cylinder assembly, Figure 5 shows a plan view as in Fig. 1 but with the arms fiexed and the mechanism cocked ready to fire, Figure 6 shows a plan view of the mechanism, of a second embodiment, in an un- cocked position after firing, Figure 7 shows the mechanism after the first stage in the cocking action, Figure 8 shows the mechanism after the second stressing stage of the cocking, and Figure 9 shows a side view with the cocking lever system schematically.

Referring first to Fig. 1, this shows the compression mechanism according to the invention in the uncocked condition and after discharge. The assembly has an integral structure incorporating a cylinder 1 at one end in which a piston 2 is freely movable with an air communication passage 3 leading to the breech 4 of Ihe barrel. The rear end of the piston is pivotally coupled with two toggles 5A and 5B which at their other ends pivotally connect with the one ends of respective arms 6A and 6B. The arms comprise composite carbon fibre reinforced material such as that known as "scotch ply' or other high energy storage material, possibly spring steel and are longituc inally inextensible but capable of flexure.The other end of the each arm is rigidly secured in a mounting means 7A and 7B respectively which means are pivotally mounted within trie mechanism body at 8.R and 8B. An actuating mechanism comprising a movable block 9 is pivotally coupled with the ends of the mounting means 7A and 7B through further toggles 1 OA and 10B respectively. Fig. 2 shows in side view the mechanism and includes the trigger 11 coupling rod 1 2 and sear 1 3 The sear 1 3 coacts with an abutment 14 provided in the piston the defined by an annular groove around the periphery thereof.A plril-off adjusting mechanism 1 5 is provided for the trigger assembly.

Furthermore, a cocking lever with associated linkages generally shown as 1 6 is also provided, this being operatively coupled to the relevant cocking lever or other system provided on the gun itself.

Referring now to Fig. 3, the initial cocking of the mechanism is effected through release of the actuating mechanism 9 which is normally held by engagement of one end cf the lever 1 7 so that said mechanism may move rearwardly thereby allowing the mounting means 7A and 7B to pivot about the respect tive pivot pins 8A and 8B. This allows the arms 6A and 68 to diverge from one another into a V-shaped configuration as shown. During this action the piston 2 moves rearwardly in the cylinder and the toggles 5A and 5B pivot outwardly to accommodate such movement.

Fig. 4 iliustrates the terminal position in which the piston is engaged with the sear 1 3.

In the position shown in Fig. 3 the arms 6A and 6B are unstressed and the stressing thereof is achieved through the cocking mechanism 1 6 which operates to force the actuating mechanism 9 forwardly thereby applying an outward force through the toggles 1 OA and 10B to the ends of the mounting means 7A and 7B. The actuating mechanism is forced forward until the arm 1 7 engages therewith at which point the mounting means are again brought into abutting relationship with the ends of the arms mounted therein parallel. This produces flexural deformation of the arms as illustrated in Fig. 5 with accompanying storage of potential energy.

With such an arrangement the force gradient applied to the piston 2 can be closely controlled principally by the configuration of the toggles 5A and 5B and it can be seen that if these extended normal to the line motion of piston 2 then there would be no retaining force necessary on the piston. In practice the toggles diverge from this position by a small angle but never-the-less the force required to hold the piston in this cocked state is relatively slight. The arrangement provides for the force exerted from the fiexure of the arms 6A and 68 to be controlled so that a maximum occurs towards the end of the piston travel producing aiso a higher velocity of motion in the piston.It can also be seen that when the piston reaches the end of the travel the arms 6A and 6B stop the motion and the piston does not come into abutment with any energy absorbing end stop.

In the second embodiment shown in Figs. 6 to 9 the construction is mainly similar to that described and, in this connection, like parts of like function are given the same reference numerals. In this embodiment the arrangement of the arms and the cocking action is modified to simplify the stressing.

Referring to Figs. 6 to 8 the arms 6a, 6b are secured to piston 2 through respective toggles 5a and Sb at their one ends but are rigidly clamped at their other ends in block member 20 with an included angle of some 10 between the arms. The block 20 is slida ble along a shaft 22 and an intermediate fixed spreader 21 is provided between the two arms. To cock the weapon the block 20 is first drawn back with accompanying move ment of the arms, toggles and piston until the sear engages and holds the piston in the rearmost position shown in Fig. 7. During this movement the arms are spread slightly, by virtue of contact with the block 21 and the angle existing between the arms, thus "breaking" outwardly the toggle linkages.With the piston 2 now held by the sear forward movement applied to block 20 causing stressing of the arms as shown in Fig. 8. The weapon is now cocked ready for discharge. The cocking mechanism is simplified to that illustrated in Fig. 9 with a cocking lever 23 secured to the weapon body or shaft 22 by a pivot 24 and a link 25 pivotally coupled to lever 23 at 26 and to the block 20 at 27.

Movement of lever 23 in direction A moves block 20 rearwards from the position of Fig. 6 to the position of Fig. 7 at the end of the travel shown in broken lines. Movement of the lever forwards in direction B then moves block 20 forward to stress the arms. Following discharge of the weapon the condition shown in Fig. 6 is re-established.

It will be understood that details of the construction and known related parts required for operation are omitted for clarity.

In the construction the piston mass can be made very small in comparison with conventional pistons using helical springs, and the mass itself is not a function of the weapon performance as the momentum does not significantly contribute to compression of air.

Due to the very small displacement undergone by the flexural deformation of the arms the spring means can be considered as effectively stationary with respect to the piston thus avoiding recoil forces. Because the muzzle energy of the discharged projectile depends essentially on the dimensions of the arms and the degree of flexural stress, it is possible to incorporate within the mechanism means whereby these values can be changed easily and in the field to provide varying levels of power.

The material from which the arms are made is not a crucial part of the invention, but conveniently carbon or other fibre reinforced composites are preferred, although other materials capable of providing sufficient potential energy on limited flexural deformation would be suitable depending on the final result required in the weapon.

The profile of the arms together with the section proves an important factor in the discharged characteristic, although these variables are best determined impirically according to the gun in which the mechanism is to be used.

The invention thus broadly provides a mechanism in which a small flexural deformation of the relatively rigid arm structure is utilised through a system of linkages to provide the motive force for a piston of relatively large area and short stroke which produces compression of the air to propel a pellet along the barrel of the gun.

Claims (14)

1. An air gun with a piston movable in a cylinder to provide compression of air for propelling a projectile along a barrel of the gun, the piston being operatively coupled to the one end or ends of one or more longitudinally enextensible but flexurally resilient arms, the other end or ends of the or each arm being fixed relative to the cylinder, a cocking mechanism operative to draw back the piston relative to the cylinder and to further cause relative displacement whereby the arm or arms are flexurally stressed to bow and a firing means to hold the piston aginst the force of the stressed arms and release same on operation of a trigger mechanism.

2. An air gun according to Claim 1, whereinn two arms are provided in side by side relationship and arranged on opposed side of a medial longitudinal plane, the arms being coupled to bow in opposed senses.

3. An air gun according to Claim 3, wherein the arms are straight and lie in spaced parallel configuration when unstressed and form a mechanism in axial alignment with the piston and cylinder.

4. An air gun according to Claim 3, wherein the mechanism is arranged generally parallel with the barrel axis.

5. An air gun according to any preceding claim. wherein the bore to stroke ratio of the piston and cylinder is over square.

6. An air gun according to any preceding Claims 2 to 5, wherein the arms bow inwardly, towards the barrel axis, at their medial portions during stressing.

7. An air gun according to any preceding Claims 2 to 5, wherein the piston is coupled to each arm through a toggle linkage, the arms being parallel when the gun is uncocked, and diverge by virtue of the toggle, at their ends coupled to the piston, to a V-shape configuration with associated pivotal deflection of mounting means securing the other ends of the arms, when the piston is drawn back in the cylinder.

8. An air gun according to any preceding Claims 2 to 5, wherein the piston is coupled to each arm through a toggle linkage, the arms being divergent outward at the other ends from the toggles when uncocked and are caused to bow to a more parallel configuration by virtue of the toggles when cocked, the other ends of the arms being securely held in a mounting means.

9. An air gun according to Claim 7, wherein an actuating mechanism operative on the mounting means causes the other ends of the arms to be brought to coplanar relationship effecting stressing and applying force to piston through the toggles.

10. An air gun according to Claim 8, wherein the mounting means with the ends of the arms is moved forwardly to effect stressing, with the toggles pivoting outwardly.

11. An air gun according to any preceding claim, wherein the, or each, arm is of a compositie fibre reinforce material.

12. An air gun according to Claim 11, wherein the, or each, arm is shaped in section and profile to provide a required characteristic of force to displacement of the piston.

1 3. An air gun according to any preceding claim, with a lever actuated cocking mechanism operatively coupled with the arm and piston assembly, a first movement of the lever drawing back the assembly end engaging the piston with a trigger coupled sear, a second movement of the lever relatively displacing a rear securement of the arms with respect to the piston to effect stressing of the arms.

14. An air gun mechanism constructed and arranged to function substanLially as herein described with reierer.e to Figs. 1 to 5 or, in the alternative to Figs. iw (a 9 of the accompanying drawings