GB2175676A

GB2175676A - Mounting telescopic sights on air guns

Info

Publication number: GB2175676A
Application number: GB08609053A
Authority: GB
Inventors: Kenneth William White
Original assignee: BSA Guns Ltd
Current assignee: BSA Guns Ltd
Priority date: 1985-04-13
Filing date: 1986-04-14
Publication date: 1986-12-03
Also published as: GB8609053D0; GB2175676B; GB8509520D0

Abstract

An air gun, instead of having dovetail recesses formed directly in the body tube 2 of the gun for mounting a telescopic sight, is fitted with a carrier 6 including a dovetail 8 to be engaged by clamps of mounts for a telescopic sight. The carrier extends along the axis of the body tube 2 and is mounted thereon by passing downwardly-projecting integral headed parts 10 through enlarged portions of keyhole shaped openings 12 in the carrier and then moving the carrier axially with respect to the body tube 2 to take the headed parts 10 into narrower portions of the openings. Resilient strips 11 are interposed and tightly compressed between the carrier 6 and body tube 2. Instead of being integral, the headed parts 10 may be separate components secured to the carrier by screws, or the heads of screws engaging threaded holes in the carrier may themselves form the headed parts for engagement with appropriately dimensioned keyhole openings. <IMAGE>

Description

SPECIFICATION Mounting telescopic sights on air guns This invention relates to air guns adapted to be fitted with telescopic sights.

Telescopic sights are usually mounted on air guns in mounts in the form of clamps fitted at the base with dovetail recesses which engage complementary grooves on the body tube of the rifle. The body tube is usually the cylinder of the actuating piston and cylinder of the air gun but may be an outer housing tube. The dovetail recess of each clamp is usually provided with relatively moveable side walls which can be separated to remove the sight together with its mounts from the gun and drawn one towards the other to grip the grooves. The grooves are usually milled in the outer surface of the body tube and their depth is limited by the wall thickness of the tube.

The clamps are apt to work loose, particularly when the gun is fixed.

The present invention aims to provide improved means for mounting a telescopic sight on an air gun.

The present invention consists in an air gun wherein an elongated carrier including a dovetail, adapted to be engaged by clamps of mounts for a telescopic sight, extends along the axis of the body tube of the air gun and is mounted thereon by securing means which engage openings pierced through the wall of the body tube.

The dovetail on the separate carrier can be made larger than dovetail grooves directly on the wall of the body tube. The complementary dovetail recesses in the base of the sight clamps can also be made larger so that they are less liable to distort when tightened. The dovetail and the complementary recesses in the clamps can be made more accurately. For these reasons a better fit can be obtained between the clamps and the dovetail so that the clamps are less likely to work loose. As dovetail grooves no longer have to be milled in the outer surface of the body tube, the walls of the body tube can be made thinner and the air gun lighter.

The securing means preferably comprises axially spaced keyhole shaped openings in the top wall of the body tube to be engaged by similarly spaced, downwardly-projecting headed parts of the carrier. The headed parts are shaped and dimensioned so that their heads can pass downwardly through the enlarged portions of the keyhole shaped openings and then be moved into retaining engagement with narrower portions of the openings by relative axial movement of the carrier and the body tube. The narrower portions preferably extend forwards of the enlarged portions, that is to say towards the muzzle end of the gun.

The retaining engagement of the headed parts and the openings must hold the carrier firmly on the body tube but the keyhole openings will allow slight axial movement of the carrier relative to the body tube during firing and this reduces the risk of the securing means shearing, a frequent cause of failure in previous proposals. Stop means may be provided to prevent excessive axial movement of the carrier relative to the body tube in the disengaging direction and may also prevent similar axial movement of the sight mounts relative to the carrier. Resilient means such as a rubber pad or pads may be interposed and tightly gripped between the carrier and the body tube to ensure firm engagement and provide a shock absorber inhibiting the transmission of shocks to the sight, for example, on firing.

The carrier may have a saddle-shaped base conforming generally to the outer surface of the body tube which is usually cylindrical. The hollow underside of the saddle-shaped base may be formed with a recess or recesses to locate the resilient pad or pads, if provided.

The hollow underside of the saddle-shaped base need not conform exactly to the outer surface of the body tube but for lateral stability there should be engagement between at least the longitudinal edges of the carrier and the body tube. The base may conform substantially to the body tube with the smallest cross-section to which it is to be fitted and may still be used satisfactorily with body tubes of larger cross-section in a range of air guns.

The carrier may be one unitary structure including the dovetail and the base and the headed parts or other elements of securing means as provided. The carrier is preferably made as an extrusion, for example in aluminium alloy, or as a casting or moulding. When the carrier is made by extrusion a continuous rib of appropriate cross-section may be provided out of which to form the headed parts, unwanted parts of the rib being subsequently cut away to leave integral headed parts of appropriate length.

Instead of being integral with the main portion of the carrier the headed parts and the main portion of the carrier may be separate components secured together by screws. The screws may pass inwardly through the main portion to engage screw-threaded holes in the headed part.

Alternatively the headed parts could simply be headed screws engaging screw-threaded holes in the carrier. The screws may be preassembled with the carrier, the headed end of each screw being left to project a predetermined amount from the underside of the carrier. The screws may be locked in the set position by an adhesive on the screw thread.

Instead of the screws being set as described, spacer sleeves may be used on the shanks of the screws which are tightened until the sleeves are clamped between the screw heads and the carder, setting them at the appropriate projection.

The screws may be countersunk-headed and engage openings in the body tube of key-hole shape. Each opening has an enlarged end of circular form allowing the head of the associated screw to pass through. From the circular end extends a slot just wide enough to receive the shank of the screw or sleeve surrounding it. The countersunk head provides a lead to assist the screw to enter the slot with the head tightly engaging the bore of the body tube.

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figure 1 its a side view of an air rifle on which a telescopic sight is mounted by means according to the present invention, Figure 2 is an enlarged fragmentary crosssection on line Il-Il of Fig. 1, Figure 3 is a sectional plan view on line Ill-Ill of Fig. 2, Figure 4 is a fragmentary plan view of the rifle of Fig. 1 with the telescopic sight removed, Figure 5 is an exploded view sectioned on line V-V of Fig. 2, Figure 6 is a view similar to Fig. 2 of a second embodiment, Figure 7 is a view similar to Fig. 2 of a third embodiment, and Figure 8 is a fragmentary plan view of part of the third embodiment shown in Fig. 7.

The air rifle shown in Fig. 1 comprises a barrel 1, a body tube 2 and stock 3. The telescopic sight indicated by the reference numeral 4 is supported by mounts 5 on a carrier 6 secured to the top of the body tube 2.

The carrier 6, shown in greater detail in Figs. 2, 3 and 5, is a length cut from an aluminium alloy extrusion the cross-section of which is shown in Fig. 2. It has a main portion 7 comprising a dovetail portion 8 and a saddle portion 9. The underside of the saddle portion is hollow to conform generally to the cylindrical outer surface of the body tube 2. In the extrusion a continuous rib of inverted Tsection depends from the underside of the saddle portion. The rib is symmetrical about the central vertical axial plane of the extrusion.

Parts of the extruded rib are cut away to leave only axially spaced headed parts 10 projecting downwards from the main portion in Fig. 5. The hollow underside of the saddle portion 9 is provided with shallow recesses to receive pads or strips 11 of rubber or other suitable resilient material.

Through the wall of the body tube 2 elongated keyhole slots 12 are pierced along the axis of the body tube 2 and spaced apart to correspond to the spacing of the headed parts 10. The enlarged portions of the keyhole slots 12 are large enough to admit the heads and the narrower portions the stems of the headed parts 10. The carrier is fitted by passing the heads of the headed parts 10 through the enlarged portions of the keyhole slots 12.

Radial pressure is then exerted on the carrier urging it towards the body tube 2, for example in a vice, to compress the rubber pads 11 while the carrier is slid forward, that is towards the barrel 1 of the air rifle, relative to the body tube 2 so that the stems of the headed parts enter the narrower portions of the keyhole slots 12. The heads of the headed parts 10 overlap the marginal portions of the bore of the body tube to retain the carrier 6 on the body tube when the pressure exerted on the carrier for assembly purposes is removed. Considerable compression of the rubber pads 11 still remains so that the carrier is tightly held on the body tube. In the assembled position the rear end of the carrier 6 is aligned with the rear end of the body tube 2 which is closed by a plug 13 in the usual way.A stop plate 14 is secured to the plug 13 by a screw or screws 15 and projects upwards across the end of the carrier 6 to prevent rearward movement of the carrier 6.

Disengagement of the headed parts 10 from the keyhole slots 12 is thereby prevented.

The stop plate 14 may also extend beyond the dovetail portion 8 and so prevent rearward disengaging movement of the sight clamps on the dovetail portion 8. The stop plate 14 is also supported by a metal back block 16 on the stock 3.

In this embodiment the body tube 2 is the cylinder of the air rifle in which works a piston 17. As shown in Fig. 2 a groove 18 may be cut along the skirt of the piston 17 to afford clearance for the headed parts 10.

In the second embodiment, of Fig. 6, headed parts 10' are separate components secured to the main portion 7 of the carrier by screws 20 engaging threaded holes in the headed parts 10' which are in effect Teeheaded nuts. The headed parts 10' are fitted to the carrier 6 before the carrier is fitted to the body tube 2. Assembly of the carrier and body tube is effected as described for the previous embodiment.

In the third embodiment, shown in Figs. 7 and 8 the headed parts comprise countersunkheaded screws 21 engaging blind, screwthreaded holes in the underside of the carrier 6. The screws 21 could be set at a predetermined projection from the underside of the carrier and locked by a suitable adhesive on the thread in the blind hole. As illustrated however spacer sleeves 22 are fitted around the shanks of the screws 21 before engagement with the blind holes and the screws are tightened as far as the spacer sleeves 22 allow.

Keyhole slots 23 are provided in the body tube 2 as shown in Fig. 8. The keyhole slots 23 have enlarged circular portions large enough to allow the heads of the screws 21 to pass through. The narrower portions of the keyhole slots 23 will admit just the shank of the screws 21, or the outer diameter of the spacer sleeves 22 where these are provided.

The conical undersurfaces of the heads of the countersunk-screws 21 provide a lead to assist entry of the screws 21 to the narrower portions of the keyhole slots during assembly of the carrier on the body tube which, after the pre-assembly of the screws and carrier, is carried out as described for the embodiment of Figs. 1 to 5.

Claims

1. An air gun wherein an elongated carrier including a dovetail, adapted to be engaged by clamps of mounts for a telescopic sight, extends along the axis of a body tube of the air gun and is mounted thereon by securing means which engage openings pierced through the wall of the body tube.

2. An air gun according to Claim 1 wherein the securing means comprises axially spaced keyhole shaped openings in the top wall of the body tube to be engaged by similarly spaced, downwardly-projecting headed parts of the carrier, the headed parts being shaped and dimensioned so that their heads can pass downwardly through the enlarged portions of the keyhole shaped openings and then be moved into retaining engagement with narrower portions of the openings by relative axial movement of the carrier and the body tube.

3. An air gun according to Claim 2 wherein the narrower portions of the keyhole openings extend forwards of the enlarged portions, that is to say towards the muzzle end of the gun.

4. An air gun according to Claim 2 or Claim 3 wherein stop means are provided to prevent excessive axial movement of the carrier relative to the body tube in the disengaging direction.

5. An air gun according to Claim 4 wherein the stop means also prevents similar axial movement of the sight mounts relative to the carrier.

6. An air gun according to any preceding claim wherein resilient means such as a rubber pad or pads is interposed and tightly gripped between the carrier and the body tube.

7. An air gun according to any preceding claim wherein the carrier has a saddle-shaped base conforming generally to the outer surface of the body tube.

8. An air gun according to Claims 6 and 7 wherein the underside of the saddle-shaped base is formed with a recess or recesses to locate the resilient pad or pads.

9. An air gun according to Claims 7 or 8 wherein the hollow underside of the saddleshaped base does not conform exactly to the outer surface of the body tube but for lateral stability there is engagement between at least longitudinal edges of the carrier and the body tube.

10. An air gun according to any preceding claim wherein the carrier is one unitary structure including the dovetail and the base and the headed parts or other elements of securing means provided.

11. An air gun according to Claim 10 wherein the carrier is made by extrusion, a continuous rib of appropriate cross-section being provided out of which to form the headed parts, unwanted parts of the rib being subsequently cut away to leave integral headed parts of appropriate length.

12. An air gun according to any one of preceding Claims 1 to 9 wherein headed parts of the securing means and a main portion of the carrier are separate components secured together by screws.

13. An air gun according to Claim 12 wherein the screws pass inwardly through the main portion to engage screw-threaded holes in the headed part.

14. An air gun according to any one of preceding Claims 1 to 9 wherein the securing means comprises headed screws engaging screw-threaded holes in the carrier, the screws being pre-assembled with the carrier and the headed end of each screw being set to project a predetermined amount from the underside of the carrier.

15. An air gun according to Claim 14 wherein the screws are locked in the set position by an adhesive on the screw thread.

16. An air gun according to Claim 14 wherein spacer sleeves are fitted on the shanks of the screws which are tightened until the sleeves are clamped between the screw heads and the carrier, setting the heads at the appropriate projection.

17. An air gun according to any one of Claims 14 to 16 wherein the screws are countersunk-headed and engage openings in the body tube of keyhole shape, each opening having an enlarged end of circular form allowing the head of the associated screw to pass through and, extending from the circular end, a slot just wide enough to receive the shank of the screw or sleeve surrounding it.

18. An air gun substantially as described herein with reference to and as illustrated by Figs. 1 to 5 of the accompanying drawings.

19. An air gun substantially as described herein with reference to and as illustrated by Figs. 1 to 5 as modified by Fig. 6 of the accompanying drwings.

20. An air gun substantially as described herein with reference to and as illustrated by Figs. 1 to 5 as modified by Figs. 7 and 8 of the accompanying drawings.