GB2181266A - Graticule adjustment - Google Patents

Abstract

In an optical aiming sight for a rifle, the sight including a graticule cell (1) for injecting a graticule image into the optical axis of the sight, the position of the graticule cell is adjustable for azimuth and elevation correction by means of a graticule cell adjuster (4). The adjuster comprises a graticule cell mounting support (8) which is disposed between a first pair of parallel linkages (9, 10) which afford movement of the cell along a first axis. A second pair of parallel linkages (17, 18) are connected to the first pair of parallel linkages at a position substantially normal thereto, the second pair of linkages affording movement of the cell along a second axis which is normal to the first axis. The arrangement affords a simple and uncomplicated means for achieving azimuth and elevation correction of the injected graticule in the optical aiming sight. <IMAGE>

Description

SPECIFICATION Graticule adjustment This invention relates two graticule adjustment within, for example, a low light or night vision aiming sight fora rifle.

In such aiming sights itisnecessarytoartificially illuminate the graticule and this is conveniently achieved by means of a graticule cell which is disposed away from the optical axis ofthe sight, the generated image being injected into the sight by reflection. The example is shown in UK patent application 2,149,933A, incorporated herein by reference, in which a prism member is used to inject the graticule image.

As with all such aiming sights it is necessary to provide for azimuth and elevation correction by means of adjustmentto the relative position ofthe graticule. Known mechanisms for achieving such adjustmenttendto requirefinelymachined highly accurate component parts, in view ofthe extremely small increments of movement required ofthe graticule in the sight. Examples of known ways of achieving graticule adjustment appear in US patents 3,936,137 and 3,994,597 which are also incorporated herein by reference.

In US patent 4,417,814, also incorporated herein by reference, the illuminated graticule source is moveable for azimuth and elevation correction by a mechanism disposed above the sight which includes a verticallyslidable wedge which transmits horizontal movement to a pairofcylindrical bearings fixed to a bracket within which is received on a screw thread a light source for generating a graticule image in the form of an aiming dot or mark.

In all ofthe known embodiments referred to above adjustment ofthe graticule image requires rather complicated or exposed arrangements which may easily be damaged in use and do not readily lend themselves to service or repair or replacement.

It is an object of the present invention to provide an aiming sight ofthe type exemplified in which the aforementioned disadvantages are obviated.

According to the invention there is provided an optical aiming sight for a rifle, the sight including a graticule cell for injecting a graticule image into the optical axis ofthe sight, the position of the graticule cell being adjustable for azimuth and elevation correction of the injected graticule by means of a graticule cell adjuster comprising cell mounting means disposed between a first pair of parallel linkages affording movement ofthe cell along first axis, and a second pair of parallel linkages substantially normal to the first pair and connected thereto, the second pair affording movement ofthe cell along a second axis substantially normal to the first, the arrangement affording azimuth and elevation correction of the injected graticule and hence sight.

Conveniently, the first and second pair of parallel linkages and the cell mounting means are integral with each other and may be formed from a single moulding of a plastics material. The adjuster may include a support such as a plate operable to prevent orinhibitunwanted movementoftheadjusterand hence graticule cell in a direction normal to the first and second axes referred to such that the adjuster is constrained for movement in a single plane only.

The invention will now be described, byway of example only, with reference to the accompanying drawing which shows an exploded view of a graticuleadjusterforan aiming sight(notshown) according to the invention, In the drawing a cylindrical graticule cell 1, of conventional type, has a hollow head portion 2 within which is disposed a graticule 3 which is illuminated buy a LED within the cell 1, for injection into the optical aiming sight.

The graticule adjuster according to this embodiment of the invention is essentially of three parts comprising a parallel link mechanism shown generally at4, a flatsupportplate 5 and a rectangular housing 6.

The parallel link mechanism 4 isformedfrom a single plastics injection moulding and has a central platform 7 on which is disposed a hollow cylindrical graticule cell support 8, defining cell mounting means according to this embodiment ofthe invention, which receives the graticule cell 1.At diagonally opposite sides of the platform 7 are a first respective pair of parallel linkages, 9,which are resiliently hinged to the platform 7 by webs 11,12.

At the ends of the linkages 9,10 remote from webs 11,12 are respective fixing lugs 13,14 each of which is resiliently hinged by a respective web 15, 16. Each lug 13,14 is provided with a pairofholesfor receiving screws by which each lug 13, 14 is securable to the support plate 5 as described later.

Asecondpairoflinkagesl7, l8areresiliently hinged to the lugs 13,14 by respective webs 19,20 and are disposed substantially normal tothefirstpair of linkages 10.

At the ends ofthe linkages 17,18 remote from the lugs 13,14 are furtherfixing lugs 21,22 which are resiliently hinged to the linkages 17, 18 by respective webs 23,24. The lugs 21,22 are each provided with a hole for receiving a screw by which each lug 21,22 is securable to the housing 6 as described later, Extending through a pairofthreaded holes in adjacent walls in the housing 6 in mutually orthogonal directions are a pair of adjusting screws 25,26 (shown in solid line for clarity) on the free end of each of which is a respective ball joint 27,28 carried on a respective spindle 29,30.

Complementaryslots3l,32 are provided respectively on the lug 13 and platform 7.

On assembly the lugs 13, are screwed to the support plate 5and the lugs 21,22 are screwed to the housing 6, in the positions shown by the fixing holes.

In this position the ball joints and spindles 27,28 and 29,30 are received in the slots 31,32. When thus assembled, the support plate 5, although fixed to lugs 13,14 is nevertheless free to move within the housing 6.

Clockwise or anti-clockwise rotation of adjusting Screw25willpushorpullthelug l3andhencemove the position ofthe graticule cell 1 along a first axis denoted by 'X'. Similarly, clockwise or anti-clockwise rotation of screw 26 will push or pull the platform 7 and hence move the position of graticule cell 1 along a second axis denoted by 'Y' substantially normal to the first axis.

The provision ofthe support plate 5 prevents or inhibits unwanted movementoftheadjusterand movement ofthe adjuster and hence graticule cell in a direction, denoted by 'Z', normal to the first and second axes such that the adjuster is constrained to remain in a single plane only.

Itwill be appreciated by those skilled in the artthat the use of a parallelogram linkage, with the graticule cell fixed centrally therewithin, will give rise to some rotation of the cell as a consequence of adjustment for azimuth and elevation correction. However, the extent of such rotation is typically only degree, and is thus negligible when compared to other sighting errors which arise in practice, such as the sighting errors attributable to the hand movements ofthe rifleman using the sight.

The embodimentofthe invention described above is illustrative only and other way of achieving bi-axial movement of a graticule cell within a parallelogram linkage can be adopted. Forinstance, if desired the adjusting screws 25,26 may be disposed for convenience adjacent to each other on a common wall ofthe housing 6, one of the screws being linked to an "L" shaped lever by which orthogonal movement of the adjuster can be achieved, the other screw being used to obtain uni-directional movement.

Furthermore, each adjusting screw 25 or 26 may be provided with means for incremental adjustment which may be obtained by means of a detent ball and spring arrangement.

Additionally, if it is required to provide positive backlash-free movement ofthe adjuster, spring biassing means may be included in addition to the resilience ofthe plastics injection moulding, particularly in configurations where there is no positive push/pull linkage of each screw 25 or 26to the adjuster mechanism 4.

The invention in the embodiment described thus provides a relatively simple, low cost and robust arrangement with minimal component parts.

Claims (6)

1. An optical aiming sightfora rifle, the sight including a graticule cell for injecting a graticule image into the optical axis ofthe sight, the position of the graticule cell being adjustable for azimuth and elevation correction of the injected graticule by means of a graticule cell adjuster comprising cell mounting means disposed between a first pair of parallel linkages affording movement of the cell along afirstaxis, and a second pairofparallel linkages substantially normal to thefirst pairand connected thereto, the second pair affording movement ofthe cell along a second axis substantially normal to the first, the arrangement affording azimuth and elevation correction ofthe injected graticule and hence sight.

2. Asightaccordingto claim 1 inwhichthefirst and second pairofparallel linkages and the cell mounting means are integral with each other.

3. Asightaccording to claim 2 inwhich thefirst and second pair of parallel linkages and the cell mounting means are formed from a single moulding of a plastics material.

4. Asightaccording to any preceding claim in which the adjuster includes a support such as a plate operable to prevent or inhibit unwanted movement oftheadjusterand hencegraticulecell in adirection normal to the first and second axes such that the adjuster is constrained for movement in a single plane only.

5. A sight substantially as hereinbefore described.

6. Agraticulecell adjusterforan optical aiming sight substantially as hereinbefore described with reference to and as shown in the accompanying drawing.