Patent Application
20120117849
A magnetic boresighter is a device that magnetically attaches to the front of a rifle barrel and permits a user to align the pointing direction of his scope to the angle of the front of the rifle barrel. Because the bullet exits the barrel traveling in the direction of the end of the barrel, this is a good method of aligning a scope.
To do this, the typical boresighter includes a reticle, permits light to enter at the end farthest from the scope and collimates this light, so that the reticle is effectively placed at an infinite range, straight ahead of the rifle barrel. In order for the reticle to be visible to someone looking through the scope, however, the collimated light, traveling in a straight line, must be able to enter the scope objective lens. So if there is no overlap between a cylinder extending straight back from the collimator lens and the objective lens of the scope, it will not be possible to use the boresighter. As scopes may be installed at different distances above the rifle breach block, a magnetic boresighter requires some flexibility in placement, in order to be able to accommodate a range of scope installations.
Unfortunately, currently available magnetic boresighters tend to be fairly expensive and may not attach magnetically to every rifle barrel end. One boresighter includes a magnet for attaching to the end of a rifle barrel, but the optical portion of the boresighter is arranged all forward of the magnet when attached to a rifle, introducing some instability to the attachment. Also, currently available boresighters feature a vertically extending longitudinal magnet, which is about 50 mm (2 inches) in vertical extent. Although this may help accommodate a wide range of scope installations, it also drives up the expense of boresighter manufacturing.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.
In a first separate aspect, the present invention may take the form of a rifle boresighter having a front adapted to face a rifle user after the boresighter has been attached to a rifle and a rear adapted to face away from the user after the boresighter has been attached to a rifle. The boresighter includes a post defining a receptacle that retains a magnet and a tubular housing having a front and a rear coincident to the front and rear of the boresighter and being supported by the post. A collimating lens is supported at the front of the tubular housing, a reticle supported in the tubular housing and a light window in the rear of the tubular housing. Also, the tubular housing is supported by the post approximately midway between it front and its rear, thereby providing a balanced load to the magnet.
In a second separate aspect, the present invention may take the form of a rifle boresighter, including a post defining a receptacle, retaining a magnet and a tubular housing supported by the post. A collimating lens assembly is supported at the front of the tubular housing, a reticle supported in the tubular housing and a light window in the rear of the tubular housing. Also, the magnet is roughened to provide frictional support against the front of a rifle barrel.
In a third separate aspect, the present invention may take the form of a boresighter that includes a magnet for attachment to the end of a rifle barrel, and optical assembly and a bridge connecting the two, and wherein the magnet has a vertical extent of less than 40 mm, thereby reducing the expense of the boresighter while accommodating most rifle and scope assembly geometries.
In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.
Exemplary embodiments are illustrated in referenced drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.
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Different rifle and scope assembly geometries have differing vertical displacements between the rifle center bore and the scope reticle center point. The boresighter collimates the light that is emitted through its front, toward the scope. Accordingly, as long as there is some horizontal straight line overlap between the boresighter optical train and the scope objective lens, the reticle image from the boresighter will theoretically appear to a user looking through the scope. But if there is only a very small overlap, the amount of light being received by the scope from the boresighter will be very small, so that the reticle from the boresighter will be very dim or even imperceptible. A boresighter is limited in the range of rifle/scope assembly geometries that it can accommodate by the vertical extent of the magnet used to attach the boresighter to the end of a rifle. Magnet 32 has a diameter of 25 mm, which, together with a collimating lens assembly diameter of 24.5 mm and a closest surface separation between magnet and collimating lens (a bridge) of 15 mm, accommodates most rifle and scope assemblies. The long magnets used in currently existing boresighters drive up the cost, making it impractical for some shooters to purchase a boresighter. Boresighter 10 addresses this problem by utilizing a smaller magnet, that can still work with most geometries. This breakthrough enables shooters who would not otherwise be able to afford a boresighter in order to properly align their scopes to rifle boresight, to do so.
While a number of exemplary aspects and embodiments have been discussed above, those possessed of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
