WO1997000419A1

WO1997000419A1 - Improvements relating to sighting devices

Info

Publication number: WO1997000419A1
Application number: PCT/GB1996/001486
Authority: WO
Inventors: Jeremy Robin Gibbs; Keith Edwin Frank Brown; Carel Dawid Myburgh
Original assignee: Denel (Proprietary) Limited
Priority date: 1995-06-19
Filing date: 1996-06-19
Publication date: 1997-01-03
Also published as: IL122678A0; AU6133196A

Abstract

A self-powered optical reflex sight for a firearm comprises a tubular housing having a front end for receiving a target to be sighted and a rear viewing end. A reflecting lens is mounted at the front end of the housing, and a light source is mounted in a light source holder towards the rear end of the housing. The light source is arranged to be reflected off the reflecting lens so as to define a reticle image. Vertical and horizontal adjusting screws are carried on the housing for adjusting the alignment of the light source relative to the tubular housing and the reflecting lens. The sight includes a light collection assembly comprising a light-collecting lens and an optic fibre assembly having a collection portion arranged to receive light from the light-collecting lens. The optic fibre assembly includes a transmission portion for transmitting light to the light source and a source portion having a triangular cross section defining the light source. The light source includes a tritium lamp mounted within the light source holder for illuminating the source portion of the optic fibre in low light conditions.

Description

IMPROλΕMENTS RELATING TO SIGHTING DEVICES

BACKGROUND TO THE INVENTION

THIS invention relates to a weapon sight, and in panicular to an optical reflex weapon sight for a firearm.

Reflex sights typically comprise a light source which shines on a front partially reflective lens so as to define a reticle which a shooter superimposes on a target viewed through the front lens. The .light source is normally located at the focal point of the lens, and is reflected on the operatively rear surface of the lens so as to define a reticle for aiming the sight.

Currently available reflex sights have a number of associated shortcomings, including fragility of the sight housing, visibility' of the sight by a target observer, and batteries for powering the light source going flat at inopportune moments. Further, the reticle may tend to become only marginally visible against bright backgrounds, and may also tend to obscure large areas of the target at longer ranges, thus making such sights relatively inaccurate and difficult to use with night vision equipment. SUMMARY OF THE INVENTION

According to the invention there is provided a self-powered optical reflex sight for a firearm comprising: a tubular housing having a front end for receiving a target to be sighted and a rear viewing end: a reflecting lens mounted at the front end of the housing: a light source mounted in a light source holder towards the rear end of the housing. the light source being arranged to be reflected off the reflecting lens so as to define a reticle image; mounting means for mounting the sight to the firearm: adjustment means carried on the housing for adjusting the alignment of the light source relative to the tubular housing and/or the reflecting lens: and a light collection assembly comprising an optic fibre assembly having a collection poπion arranged to receive ambient light, a transmission ponion for transmitting light to the light source, and a source ponion defining the light source.

Preferabh'. the light collection assembh' includes a light-collecting lens which is arranged to focus ambient light onto the collection portion of the optic fibre assembh-. is forward-looking in the direction of the target and is mounted adjacent the reflecting lens.

Conveniently, the source poπion of the optic fibre has a polygonal cross- section defining a polygonal reticle. Typicall)'. the source ponion has a triangular cross-section defining a triangular reticle.

Advantageously, the light collecting lens or an adjacent lens holder is formed with an elongate channel in its operatively rear surface for receiving the collection ponion of the optic fibre, a front surface of the lens being formed with an elongate lens track conesponding to the channel for focusing light along the length of the collection poπion of the optic fibre.

In a preferred form of the invention. the channel and the conesponding track encircle the reflecting lens and have a spiral configuration.

Alternatively, the channel and the conesponding track have a serpentine configuration and are located beneath the reflecting lens.

Conveniently, the collection poπion of the optic fibre comprises a bundle of coloured micro-fibres having a round cross-section.

Typicall} . the collection ponion of the optic fibre is joined to the transmission ponion. the transmission ponion comprising a bundle of clear micro-fibres having a round cross-section, and the transmission poπion is joined to the source poπion. the source poπion comprising a bundle of coloured micro-fibres.

Advantageously, the reflecting lens is formed with a reflective coating on its rear surface for preventing the light source from shining through the lens and an anti-reflective coating on its front surface.

The light source may include an auxiliary powered lamp operable during low ambient light conditions. The auxiliary lamp typically comprises a tritium lamp mounted within the light source holder and ananged to illuminate the source ponion of the optic fibre. Conveniently, the adjustment means comprises a horizontal adjustment screw for adjusting the position of the light source holder along a horizontal axis, and a vertical adjustment screw for adjusting the elevation ofthe light source holder pivotably about the horizontal axis, both the horizontal and venical adjustment screws being rotatably mounted to the tubular housing.

The adjustment means conveniently comprises a light source holder through which the opposite end of the optic fibre passes, a horizontal adjustment screw for adjusting the position of the light source holder along a horizontal axis, and a λ'eπical adjustment screw for adjusting the elevation of the light source holder pivotably about the horizontal axis, both the horizontal and venical adjustment screws being rotatably mounted to the tubular housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1, 2 and 3 show respective front, side and rear views of a first embodiment of a reflex sight of the invention;

Figure 4 shows a cross-sectional side view on the line 4-4 of

Figure 1 ;

Figure 5 shows a cross-sectional top view on the line 5-5 of

Figure 4;

Figure 6 shows a cross-sectional end-on view on the line 6-6 of

Figure 2; - D -

Figures 7 to 9 show respective front, side and rear views of a second embodiment of a reflex siεht of the invention:

Figure 10 shows a cross-sectional side view on the line 10-10 of Fiεure 7:

Figure 11 shows a cross sectional top plan view on the line 1 1 1 of Fiεure 10:

Figure 12 shows a cross-section on the line 12-12 of Figure 10: and

Figure 13 shows a cross-section on the line 13-13 of Fiεure 10.

DESCRIPTION OF EMBODIMENTS

Referring first to Figures 1 to 4. a first embodiment of a reflex sight 10 comprises a tubular housing 12 having a slanted front opening 14 and a rear viewing opening 16. The tubular housing defmes a central aiming axis 18. and is formed with a mounting slot 20 for enabling the sight to be mounted rigidly to a complemental sight mount on an automatic rifle or the like.

A single reflecting lens 22 is mounted towards the front end of the sight, and sits between an O-ring 24, which in turn abuts agamst a shoulder 26 defined in the housing. and an optic fibre holder 28. The lens 22 is a non- magnifying lens, and has an inwardly directed concave face 30 and an outwardly directed convex face 32. The optic fibre holder 28 has a front face formed with a serpentine channel 34. and an optic fibre 36 is coiled within the charmel. A ribbed clear plastic light collecting lens 38 formed with a parallel array of convex ribs 38 A and is fitted over the coiled optic fibre cable. The parallel ribs 38A overlie the optic fibre 36 so as to enable light falling on the ribs to be concentrated on the optic fibre 36. The optic fibre 36 is formed from a bundle of luminous plastic micro-fibres having a round cross-section. The bundle of fibres is coated with a thin layer of polycarbonate which protects the core of the fibre whilst still allowing light to be collected and transmitted by the core. The ribbed lens 38. the optic fibre 36 and the optic fibre holder 28 in combination form a light collecting assembh 40 at the front opening 14.

An optical window 42 is located just inwardly of the rear opening 16 in an appropriate slot 43 defined within the housing. and within which an O-ring 45 is also fitted. The main purpose of the optical window 42 is to seal the chamber 44 and to prevent foreign matter from getting into the chamber 44 of the sight.

A light source assembly 46 is similarly located towards the rear opening of the housing. and includes a light source holder 48. The optic fibre 36 is fed rearwardly from thε light collecting assembly 40. as is shown at 36A. with its opposite end 50 extending through a central aperture 51 formed in the light source holder 48. and terminating in a triangular end face 52 having Imm sides.

As is clear from Figure 5, a radioactive self-powered tritium light source having a half life of over twelve years is housed within the light source holder 48 adjacent the optic fibre end 50, and is used to supply iUumination to the fibre from dusk onwards, when ambient light shining on the light collector assembly 40 is poor or non-existent.

The light source holder 48 is mounted for horizontal adjustment on an adjusting screw 56 cam'ing a worm thread 58 and mounted for rotation between opposite walls 60 and 62 of the housing. A compression spring 64 acts between the light source holder and the innermost surface of the wall 62 so as to hold the screw 56 in position. The adjusting screw 56 has senations 66 extending around the outer circumference of its head 68. A blind bore 70 is formed through the wall 62 transversely relative to the main axis of the adjusting screw 56. A spring 72 is located at the blind end of the bore, and pushes a pointed plunger 74 against the seπations 66. so as to index the adiusting screw 56 as it is rotated. Rotation of the adjusting screw 56 results in audible "clicks" as the pointed end of the plunger 74 travels between the grooves in the senations. The pointed plunger 74 also prevents the screw from being rotated and the sight from drifting from a zeroed position. A circlip 78 stops the light source holder 48 from being screwed out completely and an O-ring 80 prevents water and dust from entering into the sight mechanism.

Venical adjustment of the light source holder 48 is effected by means of an adjusting screw 82 which sits in a counter-sunk bore 84 angled downwardly from the rear opening 16. The screw 82 is formed with a tubular internalh threaded shank 86 into which the complementally fitted shaft 88 of an adjustable plunger 90 or shoe is screwed. Rotation of the adjusting screw 82 causes upward and downward movement of the shoe 90, which in turn bears against a rearmost tail portion 92 of the light source holder, thereby causing the light source holder to pivot about a major axis 94 of this adjusting screw 56. This causes the triangular light emitting end face 52 of the optic fibre to move vertically in relation to the reflecting lens 22.

A coil spring 96 has a front end which seats within a bore 98 formed within a housing and a rear end which seats within a similar bore 100 formed in the tail portion of the light source holder. The spring maintains the tail 92 of the light source holder in constant contact with the shoe 90. A further coil spring 102 acts between the housing and the uppermost surface of the arm of the T-shaped shoe 90 so as to hold the adjusting screw 82 in position and to tension the shoe 90. The adjusting screw 82 is provided with an identical indexing system as the adjusting screw 56. incorporating a similar spring and plunger arrangement.

As is clear from the detail at 105 in Figure 4. the lens 22 is formed with an anti-reflection coating 106 on its outer convex surface 32 for preventing any minor-like reflection off the front of the lens so as to reduce the visibility of the lens when viewed from the front. A reflective coating 108 on the rear concave surfacε 30 of the lens prevents the light source from shining through the lens, not only preventing visibility of the light source with the naked eye but also by means of third generation night vision equipment. A hardened outer coating 1 10 covers the non-reflective coating 106 and prevents this coating 106 from being scratched.

The lens 22 is formed from a Schott BG39 filter glass or alternatively a Schott S8612 filter glass. The reflective coating 108 has a reflection of greater than 99.5% at 570 to 600nm. and a transmission greater than 80% at between 420 and 500nm in respect of light having an angle of incidence of between 0 and 10°. The non- or anti-reflective coating 106 has a

SUBSTTTUTE SHEET (RULE 26) reflectivity of less than 1% in respect of light having a wavelength of between 430 and 700nm at an angle of incidence of between 0 and 20°. In place of a separate hardened coating 1 10. the coatings 106 and 108 themselves may be harder than glass and are used to protect the lens from staining and other damage. The optical window 42 is formed from clear glass, with an anti-reflective coating on its operatively rare face so as to allow use with night vision equipment.

As is clear from Figure 6. the slot or groove 20 formed in the underside of thε sight is mounted over a complemental tongue 1 12 extending from a rear centre poπion of the firearm. Four sets of countersunk bores 1 14 extend through the sight, and mounting screws 1 16 are passed through the bores and screwed into complemental threaded apeπures 1 18 formed in the tongue 1 1 . Clamping inserts 120 are located in the countersunk bores behind the heads of the mounting screws 1 16.

The light collector assembh' 40 gathers ambient light from the front opening of the sight and transmits it via the optic cable 36. with the triangular tip 52 of the cable transmitting light in a nanow collimated beam to the rear reflective surface 30 of the lens 22. The shooter looks through the lens 22 via the rear window 42 with either one or both eyes open and superimposes the triangular reticle defined by the triangular tip of the optic fibre on the targεt to aim.

As the light collector assembly 40 is forward looking in the direction of the target, the intensity of the reticle will vary automatically depending on the amount of light falling on it from the front. As a result, when a shooter is shooting into a brightly lit area from a dark area, the reticle brightness will intensify. When aiming from a bright area onto a dimly lit target area, the reticle brightness will dim so as not to predominate relative to the target. In conditions of zero or poor light, the tritium light source will automatically illuminate the reticle.

The adjusting screws 56 and 82 can be used to adjust the reticle in such a way that the point of impact at a predetermined distance is the uppermost apex of the triangle. Typically, the entire triangle can be used for quick snap-shooting at close range, and the apex of the triangle is conveniently used for more deliberate and accurate long shots. The reticle is amber in colour rather than red. making it approximately fifteen times more visible to the human eye and also visible with second and third generation night vision equipment.

In the event of the optical sight failing, front and rear fixed open sights 122 and 124 are mounted to the housing 12 for emergency use. The front open sight 122 is mounted atop an overhanging portion 126 defining the slanted front opening. This overhanging portion 126 shades the lens 22 so as to prevent undue reflection off the front convex surface 32 of the lens.

Refening now to Figures 7 to 1 1 , a second prefened embodiment of a reflex sight 130 is shown. Those components which are similar or identical to the components in the first embodiment are indicated with the same numbering or are suffixed with an "A", and the second embodiment will be described only in so far as the components differ from those in the first embodiment.

The tubular housing 12A is formed with curved front and rear openings 14A and 16A. and is provided with front and rear apertured mounting slots 20A and 20B.

The reflecting lens 22 is mounted within a rubber seal 132 which in tum rests against a rear shoulder of a lens holder 134. A light collector holder 136 has a rearmost portion 138 which forms a complemental fit with the lens holder 134 and abuts against the rubber seal 132 so as to retain the lens 22 in position. The light collector holder 136 has an outer peripheral recess 140 which accommodates a light collector 142. The rearmost face of the light collector 142 is formed with a spiralling oval channel 144 within which an optic fibre 146 is coiled. The front face of the light collector is formed with a convex series of ribs 148 which have an oval spiral pattern coincident with the spiral of the channel 144 and optic fibre 146. This allows the light falling on the front face of the light collector to bε focused on the optic fibre, which is located at the focal length of the convex ribs 148. with a typical light path being indicated by anows 150. The optic fibre 146 is formed from a bundle of amber coloured (540nm) luminous plastic micro- fibres 152 having a round cross-section. The bundle of fibres is coated with a thin layer (6 - 7μ) of transparent polycarbonate 154 which protects thε corε of the fibre whilst still allowing light to be collected and transmitted by the core. The fibre optic cable 136 is joined by means of a fibre optic jointer 155 to a clear round transmission optic fibre 156 just rearwardly of an innermost end 158 of the channel 144 holding the amber optic fibre 146. The transmission optic fibre 156 is made from a bundle of clear plastic micro-fibres having a round cross-section matching the round cross-section of the amber fibres. The fibre bundle is coated with an opaque layer of polycarbonate which protects the core and prevents light from being lost from the core. The transmission fibre 156 is further protected by means of a black plastic shrink sleeve 160 fitted along its entire length, namely from the light collector assembly 142 through the housing to the light source holder 48A.

At the light source holder 48A the transmission fibre 156 is joined to a reticle fibre 164 by means of fibre optic connector 166. The reticle fibre 164 is formed from an amber coloured (540nm) bundle of luminous plastic micro-fibres having a triangular cross-section. The bundle of fibres is coated with a thin layer of polycarbonate which protects the core of the fibre whilst still allowing light to be collected from the adjacent tritium lamp 54. The triangular fibre optic cable 164 and tritium lamp are sealed inside a metal housing constituted by the fibre optic holder 48A. leaving only the triangular end 52 of the optic fibre exposed, and thereby providing the assembly with maximum protection whilst preventing extraneous light loss from the fibre

A flat optical window 42A is located just inwardly of the rear opening 16A housing and is held in place by means of a threaded retaining ring 170. The window 42A is sunounded

a rubber seal 172 which is similar to the sea! 132 holding thε front lens 22.

The light source holder 48A is mounted for an adjustment on an adjusting screw 56A similar to the adjusting screw 56. A compression/torsion spring 64A holds the screw 56A in position and serves to bias the tail end 174 anti¬ clockwise against an adjustable plunger 90A extending from an adjusting nut 82A. The adjusting screw 56A is provided with an indexing assembly 176 which includes senations 66A on the screw head, and a transverse bore 70A accommodating a spring 72A which serves to push a plunger 74A having a bladed end 75 against the senations 66A. so as to index the adjusting screw 56A as it is rotated. The spring 72A is held in position by means of a L J -

rectangular plug 178. A similar indexing assembly 179 is used to index the adjusting screw 82A with similar components being suffixed by a "B".

The adjusting screw 82A is used to adjust the elevation of the light source holder 4SA. and sits in a counter-sunk bore 84A. Rotation of the adjusting screw 82A causes forward and rearward movement of the shoe or plunger 90A so as to cause the triangular light emitting end face 52 of the optic fibre to move vertically in relation to the reflecting lens 22.

Referring now to Figure 13. the slots 20A and 20B formed in the underside of the sight are mounted over a tight fining complemental tongue 1 12A extending from a rear centre portion of the firearm. Two spiral or roll pins, one of which is illustrated at 180. are driven through the mounting holεs 1 14A and thε borεs 1 I SA formed through the tongues so as to hold the sight in position.

Whilst the emergency front sight 122 is unfixed in this embodiment, the rear sight 124 A can be adjusted for windage by drifting it within its dovetail recess 182. A filler plug 184 is located in a middle slot between the slots 20A and 20B. and used to fill the sealed chamber 44A cavity within the sight with nitrogen or a similar gas.

One advantage of the reflex sight of the invention is that it is entirely self- powered, with the radioactive tritium lamp having an effective life of around of twenty years. This means that there is no need for regular battery replacements or extemal electrical connections.

A further advantage is that the sight is self-adjusting owing to the forward- looking orientation of the light collection assembh'. The brightness of the reticle thus adjusts automatically in concert with the brightness of the target area.

The triangular shape of the source portion of the fibre optic cable provides for a triangular reticle which facilitates aiming. At the same time, the provision of a circular optic fibre for the transmission and collection portions of the optic fibrε assembh' is advantageous owing to the fact that round optic fibre can be bent about a far smaller radius (as little as 13mm^") than a triangular optic fibre (approximately 300mm) without incuning significant liεht losses.

Claims

1. A self-powered optical reflex sight for a firearm comprising: a tubular housing having a front end for receiving a target to be sighted and a rear viewing end: a reflecting lens mounted at the front end of the housing; a light source mounted in a light source holder towards the rear end of the housing. the light source being ananged to be reflected off the reflecting lens so as to define a reticle image: mounting means for mounting the sight to the firearm: adjustment means canied on the housing for adjusting the alignment of the light source relative to the tubular housing and/or the reflecting lens: and a light collection assembly comprising an optic fibre assembly having a collection ponion ananged to receive ambient light, a transmission ponion for transmitting light to the light source and a source portion defining the light source.

2. A sight according to claim 1 in which the light collection assembly includes a light-collecting lens which is ananged to focus ambient light onto the collection portion of the optic fibre assembly, is forward-looking in the direction ofthe target and is mounted adjacent the reflecting lens.

3. A sight according to either one of the preceding claims in which the source ponion of the optic fibre has a polygonal cross-section for defining a polygonal reticle on the reflecting lens.

4. A sight according to claim 3 in which the source ponion has a triangular cross-section defining a triangular reticle.

5. A sight according to any one of the preceding claims in which the light collecting lens or an adjacent lens holder is formed with an elongate channel in its operatively rear surface for receiving the collection portion of the optic fibre, a front surface of the lens being formed with an elongate lens track conesponding to the channel for focusing light along thε length of the collection portion of the optic fibre.

6. A sight according to claim 5 in which the channel and thε corresponding track encircle the reflecting lens and have a spiral configuration.

7. A sight according to claim 5 in which the channel and the corresponding track have a serpentine configuration and are located beneath the reflecting lens.

8. A sight according to any one of the preceding claims 5 to 7 in which the collection portion of the optic fibre comprises a bundle of coloured micro-fibres having a round cross-section.

9. A sight according to claim 8 in which the collection poπion of the optic fibre is joined to the transmission portion, the transmission portion comprising a bundle of clear micro-fibres having a round cross-section, and the transmission portion is joined to the source ponion. the source ponion comprising a bundle of coloured micro- fibres having a polygonal cross-section.

10. A sight according to any one of the preceding claims in which the reflecting lens is formed with a reflective coating on its rear surface for preventing the light source from shining through the lens and an anti-reflective coating on its front surface.

1 1 . A sight according to any one of the preceding claims in which the light source includes an auxiliary self-powered lamp operable during low ambient light conditions.

12. A sight according to claim 10 in which the auxiliary lamp comprises a tritium lamp mounted within the light source holder and ananged to illuminate the source poπion of the optic fibre.

13. A sight according to any one of the preceding claims in which the adjustment means comprises a horizontal adjustment screw for adjusting the position of the light source holder along a horizontal axis, and a venical adjustment screw for adjusting the elevation of the light source holder pivotably about the horizontal axis, both thε horizontal and vertical adjustment screws being rotatably mounted to the tubular housing.

14. An optical reflex sight comprising: a tubular housing having ^~ a front end for receiving a target to be sighted and a rear viewing end; a reflecting lens mounting at the front end of the housing; a light source mounted in a light source holder towards the rear end of the housing, the light source being arranged to be reflected off the reflecting lens so aε to define a reticle image; and a light collection assembly comprising an optic fibre assembly having a collection portion arranged to receive ambient light, a transmission portion for transmitting light to the light source and a source portion defining the light source.