FIELD OF THE INVENTION

This disclosure relates to a zero-stop turret for a firearm sight. In one embodiment, the disclosure relates to a zero-stop turret mounted to a housing of a telescopic sight of a firearm.

BACKGROUND TO THE INVENTION

Telescopic sights for firearms, for example a pistol or rifle, typically have a tubular external housing and a pair of manually adjustable sighting mechanisms including a manual adjustment control mounted on the housing, one for adjusting windage and the other for adjusting elevation. Such a telescopic sight will have an optical system housed by the housing, which comprises opposite objective and eyepiece lenses and in between these lenses within the housing a sighting element, typically either a wire reticle or an etched reticle, bearing a graphic image pattern that is optically arranged with respect to the objective and eyepiece lenses, such that the graphic image pattern provides the aiming point in a telescopic image generated by the objective and eyepiece lenses.

The manual adjustment controls are usually part of a generally cylindrical assembly, referred to as a turret assembly or simply as a turret. The elevation turret has a rotatable elevation knob which, when turned, causes the aiming point to move up or down, and the windage turret has a rotatable windage knob which, when turned, causes the aiming point to move left or right.

Telescopic sights are normally equipped with a parallax compensation mechanism which essentially consists of a movable optical element that enables the optical system to project a telescopic image of objects at varying distances and a graphic image provided by the reticle together in exactly the same optical plane. The optical system between the objective and eyepiece lenses normally includes an erector lens so that the eyepiece image is correctly oriented and not inverted. Therefore, there are normally two focal planes inside the housing along an optical axis defined by the objective and eyepiece lenses, a front focal plane or a rear focal plane, and the sighting element may be located at either of these focal planes. On fixed power telescopic sights there is no significant difference between these two options, but on variable power telescopic sights the front plane location remains at a constant size compared to the target, while the rear plane location appears as a constant size to the user as the target image grows and shrinks. There are other advantages and disadvantages for both locations, however, the choice of location for the sighting element is not central to the present invention.

Usually, the sighting element and/or other associated internal optical components, such as an erector lens, are held by a movable mount inside the housing, most commonly a tube that has an axis that extends in substantially the same direction as the optical axis of the telescopic lens system The manual adjustment controls are arranged to move the movable mount, and hence the sighting element and/or other associated internal optical components in orthogonal directions in order to generate an apparent movement of the reticle image in the telescopic image, thereby adjusting the aiming point. The movable mount is often arranged to pivot at one end, and depending on the location of the sighting element in either the front or rear focal plane, the sighting element may move with the movable mount, or may remain substantially fixed in place while other associated optical components, such as an erector lens, move with the movable mount. However, the particular mounting and movement arrangement of the sighting element and/or other associated internal optical components is not central to the invention.

Each rotatable turret knob is linked to an actuator including a linkage mechanism and a plunger which extends to the interior of the housing. Together, the rotatable turret knob and linkage mechanism provide a manual adjustment control for making a sighting adjustment. The linkage mechanism converts the rotational movement of the turret knob to movement of the plunger to cause a corresponding shift in the transverse orientation of the sighting element and/or other associated internal optical components. So that a user can judge how far to turn each knob, the manual adjustment mechanism usually comprises a click-stop mechanism to quantize the rotation and hence movement of the plunger and the corresponding adjustment to the aiming point. The user can usually both hear and feel a click detent mechanism as the turret knob is turned from one click-stop position to the next. Different types of telescopic sights have different gradations in movement, and these are normally marked off in increments on a scale that extends circumferentially around the turret knob, or may alternatively be printed on a non-rotating part of the turret or scope housing closest to the turret knob.

For example, a telescopic sight intended for air guns or small bore rim fire rifles will have an adjustment mechanism in which each single click of adjustment will change the aiming point by ¼ minute of angle (MOA), which at a range of 100 yards (91.7 m) is approximately ¼″ (6.4 mm). In general, target or long range telescopic sights may have finer graduations than this and hunting telescopic sights may have coarser graduations than this. An example of a coarser gradation would be an adjustment mechanism in which each single click of adjustment will change the aiming point by 1 milliradian of angle (mrad), which at a range of 100 yards (91.7 m) is approximately ⅓″ (9.1 mm).

Adjusting the sight allows a user to place an aiming feature of the reticle, such as a crosshair, directly on their intended point of impact without having to “hold over” the target for trajectory (or bullet drop) compensation.

Conventional turret knobs have markings on them that indicate how many clicks of adjustment have been dialled in on the turret, or an angular deviation, or a distance compensation for a given cartridge. Turret knobs are normally marked at each graduation, starting with “0” (zero) and increasing as the turret knob is turned. Sometimes, turrets can rotate more than one revolution. A problem then arises in that the scale repeats itself every revolution, which can result in confusion as to the number of rotations from a true zero setting of the turret correct for a particular distance for which the elevation has been sighted.

Aa an example, a turret knob may provide 10 mrad of adjustment over one full revolution. This may be graduated in 0.1 mrad increments, for a total of 100 increments on a scale and 100 corresponding click-stop positions. As a result, the user would see the digits 0 through 9 around turret knob and 10 mrad would be a full rotation back to the zero position. Turning beyond this then necessitates remembering the number of full turns when the turret knob is to be rotated back to its original setting.

For very long range shots, one may need to dial 40 mrad or more of compensation to compensate for bullet drop, and so turret knobs may need to provide to 4 full turns before mechanically running out of total rotational travel. The alternative, of click-stop increments being closer together makes it difficult to read the scale and to feel a definite click at each increment. Although this problem can be dealt with to some extent by increasing the diameter of the turret knob, it is normally desirable for scopes to be small, streamlined, and lightweight.

In addition, it is common when installing a new riflescope onto a rifle to “zero” the rifle. There are also many smartphone apps and other devices that can aid a shooter in calculating their ballistic compensation for a given range and environment, which can then be dialled into the turret knob. For example, a .308 calibre (7.82 mm) at a 1000 yard (914.4 m) shot may need to have 8.7 mrad compensation to place the crosshair in the correct spot in the riflescope in order to compensate for the drop of the bullet. After shooting at a long range target, a shooter will normally dial the turret “0” position, and sometimes this may need to be done quickly if there is a “target of opportunity” at a closer range.

For these reasons it is desirable to have a “zero-stop” turret, i.e. one that can be turned to a position in which there is a stop against further rotation, and one in which preferably the zero-stop position is also adjustable, so that it can be set according to the distance chosen when sighting the rifle scope reticle against a target.

It is an object of the invention to provide a convenient turret comprising a zero-stop mechanism, a method of setting such a zero-stop mechanism and a method of setting a zero-stop of a sighting adjustment turret to limit an adjustment range of a sighting element of a telescopic sight.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a turret for a telescopic sight, comprising a turret assembly and affixed externally to the turret assembly a turret knob, wherein:the turret assembly comprises:a base portion, the base portion having a seat for fixing the turret assembly to an aperture in a housing of a telescopic sight;a plunger extending along an axis of the turret within the base portion, and being movable along said axis for actuating a movable member within said housing;an adjustment mechanism linked to the plunger, the adjustment mechanism being rotateably mounted to the base portion and being configured, in use, to drive axial movement of the plunger along said axis; andthe turret knob is attached to the adjustment mechanism whereby, in use, a user can turn the turret knob to effect rotation of the adjustment mechanism in opposite first and second rotational directions, to move the plunger axially in opposite first and second axial directions by manually turning the turret knob in corresponding rotational directions;

wherein the turret assembly further comprises a zero-stop mechanism for limiting the rotation of the adjustment mechanism in both rotational directions, wherein the zero-stop mechanism comprises:a first stop member for limiting rotation of the adjustment mechanism, the first stop member being fixed to the base portion;a second stop member for limiting rotation of the adjustment mechanism, the second stop member being releasably secured to the adjustment mechanism whereby the second stop member when secured to the adjustment mechanism is rotationally carried by rotational movement of the adjustment mechanism and when released from the adjustment mechanism is freed from being carried by said rotational movement;a movement limit member extending around the turret assembly, the movement limit member comprising: (i) a substantially annular main body, said main body being rotatable about said axis with respect to both the base portion and the adjustment mechanism; and (ii) a lug extending away from said main body and being guided by said rotation of said main body along a circular path, and the lug having a first side and opposite the first side, a second side,

and wherein, the configuration of the lug, the first stop member and the second stop member when rotationally secured to the adjustment mechanism is such that:in the first rotational direction the second stop member comes into contact with the first side of the lug whereby said main body is rotated in the first rotational direction by the lug as the lug is moved along the circular path by the second stop member until the second side of the lug comes into contact with the first stop member, thereby limiting the rotation of the adjustment mechanism in the first rotational direction; andin the second rotational direction the second stop member comes into contact with the second side of the lug whereby said main body is rotated in the second rotational direction by the lug as the lug is moved along the circular path until the first side of the lug comes into contact with the first stop member, thereby limiting the rotation of the adjustment mechanism in the second rotational direction; and wherein, the configuration of the lug, the first stop member and the second stop member when rotationally released from the adjustment mechanism is such that the adjustment mechanism is freed from said rotational limits of the zero-stop mechanism.

According to a second aspect of the invention, there is provided a telescopic sight comprising:an elongate external housing of generally cylindrical shape providing a sealed enclosure for optical components held within the housing between opposite objective and eyepiece ends of the housing, said optical components comprising an adjustable sighting assembly;a turret mounted externally on a central portion of the housing, the turret being according to the first aspect of the invention, wherein the plunger extends along the axis of the turret within the base portion of the turret assembly, and is movable along said axis to actuate a movable member of the adjustable sighting assembly within the housing.

According to a third aspect of the invention, there is provided a method of setting a zero-stop to limit the rotation in both directions of rotation of an adjustment mechanism of a turret for a telescopic sight, the turret being according to the first aspect of the invention, and the method comprising:releasing the second stop member from the adjustment mechanism so that the second stop member is freed from being carried by rotational movement of the adjustment mechanism;making a desired sighting adjustment of a telescopic scope;adjusting the rotational position of the second stop member with respect to the adjustment mechanism in either the first direction of rotation or the second direction of rotation until the first side of the lug comes into contact with one of the first and second stop members and the second side of the lug comes into contact with the other one of the first and second stop members;securing the second stop member to the adjustment mechanism so that the second stop member will rotate in unison with the adjustment mechanism about the axis of the turret and thereby setting in one direction of rotation a first rotation limit corresponding to the desired sighting adjustment, a second rotation limit in the other direction of rotation being set by contact between the lug and both the first and second stop members after more than one full turn of the adjustment mechanism and less than two full turns of the adjustment mechanism.

According to a fourth aspect of the invention, there is provided a method of setting a zero-stop of a sighting adjustment turret to limit an adjustment range of a sighting element of a telescopic sight, said turret comprising a turret assembly and a turret knob removeably affixed externally to the turret assembly, the turret assembly comprising:a base portion fixed to said telescopic sight;an adjustment mechanism that is rotatable in opposite first and second rotational directions around a turret axis and which is linked to a plunger that is movable in opposite first and second axial directions in response to rotation of the adjustment mechanism in, respectively, said first and second rotational directions; anda zero-stop mechanism for limiting the rotation of the adjustment mechanism in both directions of rotation, the zero-stop mechanism comprising a first stop member fixed to said fixed base portion, a second stop member removeably affixed to the adjustment member, and a movement limit member extending around the adjustment mechanism and comprising a substantially annular main body and a lug extending away from said main body, the lug comprising first and second sides facing, respectively, in opposite rotational directions;

wherein the method comprises:removing the turret knob from the turret assembly;releasing the second stop member from the adjustment mechanism so that the second stop member is freed from being carried by rotational movement of the adjustment mechanism;making a desired sighting adjustment of a telescopic scope;adjusting the rotational position of the second stop member with respect to the adjustment mechanism in either the first direction of rotation or the second direction of rotation until the first side of the lug comes into contact with one of the first and second stop members and the second side of the lug comes into contact with the other one of the first and second stop members;securing the second stop member to the adjustment mechanism so that the second stop member will rotate in unison with the adjustment mechanism about the axis of the turret and thereby setting in one of said rotational direction a first rotation limit corresponding to the desired sighting adjustment, a second rotation limit in the other rotational direction being set by contact between the lug and both the first and second stop members after more than one full turn of the adjustment mechanism and less than two full turns of the adjustment mechanism; andaffixing the turret knob to the turret assembly.

The desired sighting adjustment may be made either with the turret knob attached, or with the turret knob removed. After the desired sighting adjustment has been made, the turret knob may, if this has been attached during the sighting adjustment, be removed, if needed, to gain access to the adjustment mechanism.

Preferably, the first side of the lug faces in the first rotational direction and the second side of the lug faces in the second rotational direction.

Preferably the turret knob comprises a cap portion and a substantially cylindrical skirt portion that depends axially from the cap portion. In a preferred embodiment of the invention, the zero-stop mechanism is concealed behind the skirt portion when the turret knob is affixed to the adjustment mechanism.

The substantially annular main body of the movement limit member may have radially outer and radially inner surfaces that are substantially cylindrical. These cylindrical inner and outer surfaces may then be bounded by opposite end surfaces of the main body that are substantially annular in shape and that extend in planes that are perpendicular to the turret axis.

The rotation of the adjustment mechanism is preferably quantized by a click-stop mechanism so that the rotation of the turret knob is held at desired points around a revolution of the turret knob.

In a preferred embodiment of the invention, the turret knob is removeably attached to the adjustment mechanism. When attached, this may protectively conceal all or most of the adjustment mechanism. When removed, this provides access to the zero-stop mechanism for a user to rotationally disengage the second stop member from the adjustment mechanism so that a zero-stop rotational position of the adjustment mechanism can be set, after sighting in of the turret.

The zero-stop mechanism may comprise a substantially annular mount that extends circumferentially around the adjustment mechanism, from which the second stop member extends. The annular mount may be configured to be releasably securable to the adjustment mechanism.

The second stop member may be mounted to a supporting portion of the annular mount.

The annular mount of the zero-stop mechanism is preferably ring-shaped but need not be an unbroken ring extending around a full circle. It is sufficient only that the zero-stop mechanism extends around more than half a circle so that it is rotationally seated around the adjustment mechanism.

The annular mount preferably comprises a collar that extends fully around the adjustment mechanism.

In a preferred embodiment, the second stop member is a pin that extends substantially parallel with the axis of the turret.

Most preferably, the pin extends in a direction from a main body portion of the collar towards the base portion of the turret assembly.

The collar may have a shield that extends from the main body portion of the collar. The pin can then be shielded in a radial direction by the shield.

The annular mount may comprise a ring that extends fully around the adjustment mechanism.

The annular mount may comprise a skirt that extends from an outer periphery of said ring in a direction towards the base portion of the turret assembly. Preferably, the skirt that extends coaxially with the ring of the annular mount. The skirt then may provide a shield for the pin.

The annular mount preferably comprises at least one fixing member for releasably securing the annular mount to a radially outwards surface of the adjustment mechanism. The fixing member may, for example, be a grub screw that extends radially inwards from an aperture in a circumferentially extending surface of the annular mount to bear on this radially outwards surface.

The turret knob is preferably removeably secured to the adjustment mechanism and the adjustment mechanism may be provided with a series of grip features extending around a rim of the adjustment mechanism by which a user may, in use, grip this rim to rotate the adjustment mechanism to make a sighting adjustment when the turret knob is removed from the adjustment mechanism.

The configuration of the lug, the first stop member and the second stop member is such that the movement limit member is interposed rotationally between the first and second stop members.

The substantially annular main body of the movement limit member is most preferably ring-shaped.

The main body of the movement limit member is preferably ring-shaped but need not be an unbroken ring extending around a full circle. It is sufficient only that the movement limit member extends around more than half a circle so that it is rotationally seated as part of the turret assembly.

The substantially annular main body of the movement limit member may be seated on an annular ledge extending around the adjustment mechanism. The fixed base portion may be in the shape of an upwardly facing cup in which the adjustment mechanism is rotationally seated, this cup having a rim that is radially outwards from this annular ledge.

The rim of the cup may be axially offset with respect to the ledge around the adjustment mechanism to provide a clearance gap with the substantially annular main body of the movement limit member.

The first stop member may be mounted to a supporting portion of the rim of the cup.

The first stop member is most preferably a pin that extends substantially parallel with the axis of the turret. For example, the turret knob may comprise a cap portion and the pin may extend in a direction from the fixed base portion towards the cap portion of the turret knob.

In a preferred embodiment of the invention, the first stop member is radially outwards with respect to the second stop member. The first stop member may have a first extent in a direction parallel with the axis of the turret and the second stop member may have a second extent in a direction parallel with the axis of the turret. These first and second extents preferably overlapping one another in a plane perpendicular to the axis of the turret assembly. This helps to limit, in an axial direction, the extent of the lug, in order to help keep the turret assembly relatively compact.

The lug may extend both axially and radially away from the main body of the movement limit member. The axial projection may be configured to contact the second stop member and the radial projection may be configured to contact the first stop member.

The first and second sides of the lug preferably present respective first and second abutment surfaces that are oriented, substantially, in opposite rotational directions of the movement limit member. For example, the first and second abutment surfaces may be parallel with each other or, alternatively, lie in a plane extending through the axis of the turret.

The first and second stop members preferably present respective first and second stop surfaces that are oriented, substantially, in opposite rotational directions of the movement limit member.

The first side of the lug may present a first common face for contacting, at a first limit of rotation, the first stop member and for contacting, at a second limit of rotation opposite to the first limit of rotation, the second stop member.

Additionally, or alternatively, the second side of the lug may present a second common face for contacting, at a first limit of rotation, the second stop member and for contacting, at a second limit of rotation opposite to the first limit of rotation, the first stop member.

The turret knob may comprise a cap and a skirt that depends axially from a periphery of the cap. The adjustment mechanism may then comprise an axially slideable member that is movable between a raised orientation and a lowered orientation, the cap being removeably mounted to the axially slideable member.

The skirt and the fixed base portion preferably have therebetween matching formations which, in use, inter-engage to lock the turret knob against rotation when the turret knob is depressed to cause the axially slideable member to be in the lowered orientation, and which disengage to free rotationally the turret knob when the turret knob is pulled up to cause the axially slideable member to be in the raised orientation.

Additionally, or alternatively, the axially slideable member when in the lowered orientation may be configured to overlap the substantially annular mount, thereby limiting axial movement of the annular mount away from the fixed base portion when the annular mount is rotationally released from the adjustment mechanism.

