Patent Publication Number: US-9846010-B2

Title: Firearm scope height tool

Description:
FIELD OF THE INVENTION 
     The present invention relates to firearm accessories, in particular a tool for determining the height of scope rings appropriate for fitting a scope to a firearm. The tool is also suitable for fitting other optical devices such as a red dot sight. 
     BACKGROUND TO THE INVENTION 
     Sighting scopes are a useful accessory for a firearm, however firearms are often supplied without a scope leaving the shooter to purchase and fit a scope. A scope is usually fitted to a mounting rail or dovetail on the top of a firearm with the aid of scope rings. Scope rings come in a variety of heights to suit different scope and firearm combinations as well as the preferences of a shooter. A scope ring must support a scope at a sufficient height so that the scope clears the barrel and preferably as low as possible to increase the accuracy of the scope/firearm combination. It is therefore important that the correct height scope rings are chosen, this however is not an easy task. It is common for incorrect scope rings to be selected and purchased. This is both inconvenient for a shooter and a costly exercise if the scope rings cannot be returned to the vendor. 
     At present there is no easy and reliable method to determine the appropriate height of scope rings to use with a particular firearm and scope combination. A search of online forums for shooters confirms that this is a common problem. 
     In the first instance a shooter may hold a scope in the appropriate position and attempt to measure the height from the top of the rail to the middle of the scope. This method is fraught with inaccuracies. 
     Some online calculators exist for determining scope ring height, however these rely on accurate measurements of firearm and scope geometry. Some calculators come with predefined values for some measurements for particular firearms and scopes, however the coverage is not universal and is often limited to particular brands of firearms and scopes that the web site vendor is affiliated with. 
     The object of this invention is to provide a tool capable of measuring the appropriate height for firearm scope rings to alleviate the above problems, or at least provides the public with a useful alternative. 
     SUMMARY OF THE INVENTION 
     In a first aspect the invention comprises tool for temporarily mounting a scope to a mounting rail of a firearm, including a body with a mounting slot to attach the tool to the mounting rail; a slide with a saddle for supporting the scope, the slide vertically movable with respect to the body; and means for measuring the vertical displacement of the saddle with respect to the mounting rail. 
     Preferably the measuring means comprises a scale on the body and a pointer on the slide, however the scale may be on the slide and a pointer on the body. 
     The measuring means may also comprise a first shoulder attached to the body and a second shoulder attached to the slide, wherein the first shoulder and second shoulder are vertically displaced from each other equivalent to the vertical displacement of the first saddle with respect to the mounting rail. Alternatively the measuring means comprises a third shoulder attached to the body and a fourth shoulder attached to the slide, wherein the third shoulder and fourth shoulder are vertically displaced from each other equivalent to the vertical displacement of the centre of the scope with respect to the mounting rail. 
     Preferably the tool further comprises at least one guide slot and the slide comprises at least one guide to restrain movement of the slide with respect to the body, alternatively the body may further comprise at least one guide and the slide comprises at least one guide slot to restrain movement of the slide with respect to the body. In preference the slide is releasably fixable to the body to prevent movement of the slide with respect to the body. 
     The mounting slot may be adapted to fit to a Picatinny mounting rail or a dovetail. 
     The slide may further comprise a second saddle and be movable between a first configuration in which the first saddle supports the scope and a second configuration in which the second saddle supports the scope. Preferably one saddle is 1″ and one 30 mm. 
     The tool may further comprise a slide extension with a fifth shoulder horizontally aligned with the fourth shoulder. 
     It should be noted that any one of the aspects mentioned above may include any of the features of any of the other aspects mentioned above and may include any of the features of any of the embodiments described below as appropriate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows. 
         FIG. 1  is a perspective view of a firearm scope height tool according to the present invention suitable for use on a firearm with a Picatinny rail. 
         FIG. 2  shows the tool of  FIG. 1  from a front view. 
         FIG. 3  shows the tool of  FIG. 1  from a rear perspective view. 
         FIG. 4  shows a perspective view of an embodiment of the tool suitable for use on a firearm with a dovetail. 
         FIG. 5  shows the tool of  FIG. 4  from a front view. 
         FIG. 6  shows the frame of the tool from a front perspective view. 
         FIG. 7  shows the frame of the tool from a rear perspective view. 
         FIG. 8  shows the saddle of the tool from a front perspective view. 
         FIG. 9  shows the saddle of the tool from a rear perspective view. 
         FIG. 10  shows a firearm fitted with a Picatinny rail. 
         FIG. 11  shows the firearm of  FIG. 10  fitted with the tool. 
         FIG. 12  shows the firearm of  FIG. 10  fitted with a scope. 
         FIG. 13  is a close up view of a Picatinny rail with the tool fitted. 
         FIG. 14  is a close up view of a Picatinny rail fitted with the tool and a scope. 
         FIG. 15  shows a scope height tool according to a further embodiment from a front perspective view. 
         FIG. 16  shows the tool of  FIG. 15  from a rear perspective view. 
         FIG. 17  shows an exploded view of the tool of  FIG. 15 . 
     
    
    
     DRAWING COMPONENTS 
     The drawings contain the following numbered items:
       20  scope height tool (first embodiment)     30  frame     32  mounting slot (Picatinny)     33  mounting slot top     34  slide guide slot     36  height measuring shoulder (saddle height)     37  height measuring shoulder (centre height)     40  scale markers (saddle height)     41  scale indicia (saddle height)     42  scale markers (centre height)     43  scale indicia (centre height)     50  slide     52  large saddle (30 mm)     53  saddle bottom     54  height measuring shoulder (saddle height)     55  height measuring shoulder (centre height)     56  small saddle (1″)     57  saddle bottom     58  height measuring shoulder (saddle height)     59  height measuring shoulder (centre height)     60  guide     64  guide nut     70  thumb screw     80  scope height tool (second embodiment)     82  mounting slot (dovetail)     90  firearm     92  Picatinny rail     94  sighting scope     200  scope height tool (further embodiment)     250  slide extension     255  scope centre height measuring shoulder (for 1″ scopes)     259  scope centre height measuring shoulder (for 30 mm scopes)   

     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description of the invention refers to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration. 
     The present invention provides a tool that allows the correct height scope rings to be chosen for a particular firearm and scope combination. The tool fits in place of scope rings, allowing a scope to be temporarily mounted on to a firearm. The tool is then adjusted to a particular ring height for evaluation or adjusted for best scope fit and then the required ring height is read from the tool. The drawings depict the tool in use with a rifle, however it is to be understood that the tool is suitable for any firearm to which a scope may be fitted. 
     The tool is discussed primarily for use with Picatinny rails as defined in standard MIL-STD-1913, but will also work with Weaver rails on which the Picatinny standard is based. The tool works with rails that are either integral to the firearm or fitted to one. A further embodiment of the invention is suitable for use with dovetails that may be cut into the top of a firearm. For the sake of brevity the tool will be primarily discussed in conjunction with a Picatinny rail, however this is to be understood to be applicable to other types of rails and mounts as discussed above which will be generically referred to as “mounting rails”. 
     A first embodiment of a firearm scope height tool according to the present invention is shown as  20  in front perspective view in  FIG. 1 , front on in  FIG. 2  and in a rear perspective view in  FIG. 3 . The tool comprises a generally u-shaped frame  30  and a slide  50  which can move up and down with respect to the frame. Thumb screws  70  serve to secure the slide at the desired height. The frame includes a mounting slot  32  that attaches the tool to a Picatinny rail on the top of a firearm (as seen in  FIG. 13 ) and the slide provides a saddle  52  to support the barrel of a sighting scope. 
     The movement of slide  50  is restrained by guides  60  that are retained by slots  34  in the frame  30 . The combination allows only vertical movement of the slide. Screws  70  pass through holes in the guides to engage with nuts  64  embedded in the slide  50 . The screws serve to retain the slide to the frame and when tightened also prevent vertical movement of the slide. The slide is set in a desired position, or its position measured with aid of scale markers  40 ,  42  and scale indicia  41 ,  43 . The screws  70  also indicate the position on the scales. The scales are in imperial units as most scope rings are made to imperial measurements. In further embodiments metric scales or both types of scales are used. The tool incorporates two scales:  40 ,  41  to measure the distance from the top of the mounting rail to the bottom of the saddle; and  42 ,  43  to measure the distance from the top of the mounting rail to the centre of the scope sitting in the saddle  52 . The height to the centre of the scope is more commonly used and corresponds with the height of the scope rings needed to mount a scope at the same height as achieved when using the tool. The scales are provided in increments of ¼″ and can be readily interpolated by eye for intermediate values. If a more precise measurement is required, a ruler or callipers can be used to measure the distance between height measuring shoulders  36  and  54  for the saddle bottom height and between height measuring shoulders  37  and  55  for the sight centre height. Shoulders  36  and  37  are provided on the frame and align with the top  33  of the mounting slot. Shoulder  54  is provided on the slide and aligns with the bottom  53  of the saddle  52 , whilst shoulder  55  aligns with the centre of a scope sitting in the saddle  52 . 
     A second embodiment of the tool is shown as  80  in  FIG. 4  from a perspective view and in  FIG. 5  from front on. The tool  80  differs from the tool  20  in having a mounting slot  82  suitable for use with a dovetail (as opposed to the mounting slot  32  for use with Picatinny rails). 
       FIGS. 6 and 7  show the frame  30  of the tool in isolation from front and rear perspective views. 
       FIGS. 8 and 9  show the slide  50  of the tool from front and rear perspective views. The slide may be used in a first orientation (as shown) with the large saddle  52  uppermost, or rotated by 180° in which case the smaller saddle  56  is uppermost. The tool may consequently be used with two different sizes of scopes. Saddle  52  is for use with 1″ scopes and saddle  56  is for use with 30 mm scopes, but may also be used with other sized scopes in which case a suitable offset will need to be added to the measured height. The height measuring shoulders  54  and  58  align with the respective saddle bottoms  53  and  57 , whilst the height measuring shoulders  55  and  59  align with the respective centres of the scopes sitting in the saddles. 
       FIGS. 10 to 12  illustrate how a scope may be fitted to a firearm with the aid of the tool in order to determine the appropriate height of scope rings for the particular scope and firearm combination.  FIG. 10  shows a firearm  90  with a Picatinny rail  92 . Two of the tools  20  are then slid onto the Picatinny rails as shown in  FIG. 11 . The scope  94  is then placed onto the tools  20  as shown in  FIG. 12 . The height of the scope is then checked by the shooter to ensure that it clears the barrel of the firearm and is at comfortable height for use, preferably with the scope as close as possible to the barrel of the firearm. The height of the tools is either set to a particular value before the scope is fitted, allowing the suitability of particular scope rings to be checked, or adjusted until the scope is at a desired height, after which the height is read or measured from the tool. If the height thus determined does not correspond to an available ring height then a higher or lower available ring height can be selected. The shooter then has the option of adjusting the tool to the available heights to see which is preferred. Subsequently there will be no unpleasant surprises for the shooter when they buy and fit actual scope rings as they will mount the scope at exactly the same height as was tested with the tool. 
       FIGS. 13 and 14  provide close up views of the tools fitted to a Picatinny rail, without ( FIG. 13 ) and with ( FIG. 14 ) a scope fitted. 
     A further embodiment of the invention is shown as  200  in  FIGS. 15 to 17  including a slide extension  250  to provide a second shoulder  255  at scope centre height. The further embodiment is seen in front perspective view in  FIG. 15 , rear perspective view in  FIG. 16  and in an exploded view in  FIG. 17 . The slide extension  250  is similar in structure to the first slide  50 , and is attached to the rear of the slide  50  via the thumbscrews  70 . The slide extension still allows the slide to be fitted in a first orientation for 1″ scopes and an inverted orientation for 30 mm scopes in which case the second scope centre shoulder  259  comes into play. 
     The invention also encompasses mechanical equivalents of the exemplary embodiments presented above. In one further embodiment (not shown) the indicia and scale are provided on the slide and a pointer on the body to measure the ring height. In a yet further embodiment (not shown) the position of the guides and guide slots are reversed between the body and the slide. 
     The reader will now appreciate the present invention which provides a tool for temporarily fitting a scope to a firearm to accurately determine the height of scope rings to use with a particular firearm/scope combination. 
     Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in this field. 
     In the present specification and claims (if any), the word “comprising” and its derivatives including “comprises” and “comprise” include each of the stated integers but does not exclude the inclusion of one or more further integers.