Patent Abstract:
The present invention provides a “third-axis” leveling block for use with an archery sight. The third-axis leveling block holds an archery sighting device (e.g., a scope or a pin sight) as know in the art. The leveling block adjusts the position of the sight in two axes by means of cams. One of the cams adjusts the sighting device to the archer&#39;s preferred cant. The other cam adjusts the angle of the sighting device with respect to the bow to keep the archer&#39;s cant consistent when the bow is raised or lowered for shooting at targets at any elevation, above, below, or on the same level as the archer.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 60/740,771, “A Third-Axis Leveling Block for a Bow Sight,” which was filed on Nov. 29, 2005, and which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to sights for archery bows and, more particularly, to devices for leveling sights for archery bows. 
     BACKGROUND OF THE INVENTION 
     Archery sights have long been available for use when the bow is held vertically and when the archer and the target are on the same level. As an example of a modern archery sight, please see U.S. Pat. RE 36,266 (“Bow Sight”). 
     However, these conditions are not always met in the field. First, while archers have long been told to hold their bows in a vertical plane, this orientation is not entirely natural to the human arm. Holding the bow in this vertical position places some rotational stress on the arm. “Canting” the bow, that is, holding it at a slight angle from the vertical plane, feels more natural and reduces the stresses acting on the archer and on the bow thus leading to more accurate shots. 
     Second, and relatedly, archers in some situations tend to change the cant at which they hold their bow. This change is noticeable when the archer and the target are not on the same level. While hunting in rough terrain, for example, the archer&#39;s best (or only) shot often presents itself when the target is either above or below the archer&#39;s level. When moving the bow to aim at a target above or below the archer&#39;s own position, the archer tends to change the cant of the bow. When using a traditional archery sight, this unconscious change in cant results in shots hitting to the right or left of the target. 
     For these and other reasons, there is a need for an archery sight that compensates for conditions beyond the idealized conditions of the archery range. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, the present invention provides a “third-axis” leveling block for use with an archery sight. The third-axis leveling block holds an archery sighting device (e.g., a scope or a pin sight) as know in the art. The leveling block adjusts the position of the sight in two axes by means of cams. By moving the cams, the archer adjusts the sight to the archer&#39;s natural cant and helps the archer to maintain a consistent cant when shooting at targets at any elevation, above, below, or on the same level as the archer. 
     In some embodiments, the leveling block attaches to an elevation block (possibly by a dovetail connector) of a traditional bow-sight structure. The leveling block in turn holds a traditional sighting device. The leveling block includes two cams to allow adjustments on two generally perpendicular axes. One of the cams adjusts the sighting device to the archer&#39;s preferred cant. The other cam adjusts the angle of the sighting device with respect to the bow to keep the archer&#39;s cant consistent when the bow is raised or lowered. 
     In some embodiments, part of the leveling block is made of one piece with the elevation block. In some embodiments, an additional cam (or two additional cams) is (are) added on an axis (axes) parallel to one (both) of the first two cams to allow linear adjustments of the sight. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view of a typical archery bow equipped with a bow sight; 
         FIGS. 2   a  and  2   b  are perspective views of a bow sight incorporating a third-axis leveling block according to the present invention; 
         FIG. 3  is an exploded assembly view of a third-axis leveling block; 
         FIGS. 4   a ,  4   b , and  4   c  are views of a cam usable with a third-axis leveling block; 
         FIGS. 5   a ,  5   b , and  5   c  are views showing the effects on a bow sight of a first cam adjustment of a third-axis leveling block; and 
         FIGS. 6   a ,  6   b , and  6   c  are views showing the effects on a bow sight of a second cam adjustment of a third-axis leveling block. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning to the drawings, wherein like reference numerals refer to like elements, the present invention is illustrated as being implemented in a suitable environment. The following description is based on embodiments of the invention and should not be taken as limiting the invention with regard to alternative embodiments that are not explicitly described herein. 
     A third-axis leveling block according to the present invention can be incorporated into the archery bow arrangement  100  shown in  FIG. 1 . Releasably attached to an archery bow  102  and extending outwardly from the archery bow  102  in the general direction of a target, is an elongated support bar  104 . Attached to the end of the elongated support bar  104  is a sighting frame  106  which often takes the form of a vertical C-shaped yoke. The sighting frame  106  can support various adjustment mechanisms, including the third-axis leveling block of the present invention (see  FIGS. 2   a  and  2   b ), that vary the spatial relationship between the archery bow  102  and the bow-sighting device  108 . Generally, an archer uses these adjustment mechanisms to compensate for various conditions, such as a distance from the archer to the target, wind, elevation of the target relative to the archer, and the archer&#39;s natural cant of the bow. For details of a possible archery bow arrangement  100 , please see U.S. Pat. RE 36,266 (“Bow Sight”), which is incorporated herein by reference in its entirety. While the archery bow arrangement  100  shown in  FIG. 1  is quite sophisticated, other arrangements are known in the art, and the present invention is not limited to any specific structural context. 
       FIGS. 2   a  and  2   b  are different views of a complete archery sight mechanism  200  that incorporates a third-axis leveling block according to the present invention. An attachment mechanism  202  releasably attaches the elongated support bar  104  to the archery bow  102 . (For clarity&#39;s sake, the archery bow  102  itself is not shown in these figures.) In the archery sight mechanism  200  shown in  FIGS. 2   a  and  2   b , the sighting frame  106  attached to the end of the elongated support bar  104  holds a rotatable lead screw  204 . The lead screw  204  holds an elevation block  206  (more easily seen in  FIG. 2   b ). When either elevation adjustment knob  208 , located at either end of the lead screw  204 , is turned, the elevation block  206  is raised or lowered to adjust for a distance from the archer to a target. U.S. Pat. RE 36,266 presents the details of one possible elevation block arrangement. 
     In some embodiments, the elevation block  206  supports a windage block  210  ( FIGS. 2   b ) on a rotatable lead screw (not shown). When the windage adjustment knob  212  is turned, the rotatable lead screw turns, and the windage block  210  moves horizontally, perpendicular to the possible movement of the elevation block  206 . The archer uses the windage block  210  to adjust for prevailing wind conditions. U.S. Pat. RE 36,266 presents the details of one possible windage block arrangement. 
     In the arrangement of  FIGS. 2   a  and  2   b , the windage block  210  supports a third-axis leveling block  214  according to the present invention. In one embodiment, the third-axis leveling block  214  includes two adjustment cams and, for each adjustment cam, a pivot.  FIG. 2   a  shows a first adjust cam  216  and its pivot  218 , while  FIG. 2   b  shows a second adjustment cam  220  and its pivot  222 . The structure of a possible embodiment of the third-axis leveling block  214  and its attachment mechanisms are shown in greater detail in  FIGS. 3 ,  4   a ,  4   b , and  4   c.    
     The third-axis leveling block  214  of  FIGS. 2   a  and  2   b  clamps a tube  224  ( FIG. 2   a ) that holds a rod  226  of a bow-sighting device  108 . Preferably, the tube  224  has a hexagonal outer cross section to prevent it from rotating within the clamps of the third-axis leveling block  214 . 
       FIG. 3  shows an exploded assembly of an embodiment of the third-axis leveling block  214 . In some embodiments, a mounting block  300  of the third-axis leveling block  214  includes a V-shaped notch  302 . This notch  302  forms a half-dovetail connector that attaches to a complementary half-dovetail connector in the windage block  210  (see  FIG. 2   b ). The two half-dovetail connectors are wedged tightly together when a screw (not shown) is tightened. This type of connector, described in U.S. Pat. RE 36,266, is preferred because it allows the mounting block  300  of the third-axis leveling block  214  to be tightly and precisely clamped to the windage block  210  via a single screw without putting excessive strain on that screw. In other embodiments, the mounting block  300  of the third-axis leveling block  214  is formed in one piece with the windage block  210 . In that case, a dovetail connector is preferred to connect the third-axis leveling block  214 /windage block  210  to the elevation block  206 . 
     Attached to the mounting block  300  is a top-hat block  304 . (A possible mechanism for connecting these two pieces is discussed below.) A clamp assembly  306 , shown in  FIG. 3  as consisting of two clamps, is in turn attached to the top-hat block  304 . (The present invention is not limited to the details of the specific clamp assembly  306  as shown in  FIG. 3 .) The clamp assembly  306  clamps the tube  224  (discussed above with reference to  FIG. 2   a ) which in its turn holds a rod of a bow-sighting device  108  (not shown in  FIG. 3 ). 
     The top-hat block  304  is mounted in such a manner that it can pivot relative to the mounting block  300 . The first pivot  218  is shown in  FIG. 3  as a screw that passes through a hole in the top-hat block  304  and screws into a first threaded hole in the mounting block  300 . In some embodiments, the first pivot  218  includes a friction-reducing element (such as a Teflon washer). A second screw  308  passes through an elongated hole in the top-hat block  304 , passes through a hole in the first cam  216 , and screws into a second threaded hole in the mounting block  300 . Again, a friction-reducing element  310  can be used. The first cam  216  includes a circular boss (shown in  FIGS. 4   a ,  4   b , and  4   c ) that fits into a countersunk portion of the second hole in the mounting block  300 . When the first cam  216  is rotated about that boss as it sits in the countersunk portion of the second hole in the mounting block  300 , the first cam  216  pushes on a countersunk area on the top-hat block  304  which causes the top-hat block  304  to pivot around the first pivot screw  218 . The elongated hole in the top-hat block  304  allows the top-hat block  304  to move relative to the second screw  308  and also limits the amount of such movement. 
     In some embodiments, the clamp assembly  306  is pivotably mounted to the top-hat block  304  in a manner similar to the mounting of the top-hat block  304  to the mounting block  300 . In the embodiment of  FIG. 3 , the second pivot  222  is a screw that passes through a hole in the top-hat block  304  and screws into a first threaded hole in the clamp assembly  306 . A second screw  312  passes through an elongated hole in the top-hat block  304 , passes through a hole in the second cam  220 , and screws into a second threaded hole in the clamp assembly  306 . The second cam  220  includes a circular boss (shown in  FIGS. 4   a ,  4   b , and  4   c ) that fits into a countersunk portion of the second hole in the clamp assembly  306 . When the second cam  220  is rotated about that boss as it sits in the countersunk portion of the second hole in the clamp assembly  306 , the second cam  220  pushes on a countersunk area on the top-hat block  304  which causes the clamp assembly  306  to pivot around the second pivot screw  222 . The elongated hole in the top-hat block  304  allows the clamp assembly  306  to move relative to the screw  312  and also limits the amount of such movement. 
     In a preferred embodiment, the axes of the pivot screws  218  and  222  are perpendicular to one another. This allows the bow-sighting device  108  (shown in  FIGS. 2   a  and  2   b ) to be pivoted independently on two axes with respect to the mounting block  300 . 
     In an embodiment not shown in  FIG. 3 , two additional cams are added that pivot around the screws  218  and  222 . This arrangement allows the top-hat block  304  to be linearly shifted with respect to the mounting block  300  by simultaneously shifting two parallel cams, the cam  216  around the screw  308  and the new cam around the screw  218 . In this arrangement, if one of a pair of parallel cams is held in place, then the other cam in the pair serves to pivot the top-hat block  304  as described above in the two-cam embodiment. Similarly, the cams  220  around the screw  312  and the new cam around the screw  222  allow the clamp assembly  306  to be moved linearly with respect to the top-hat block  304 . 
       FIGS. 4   a ,  4   b , and  4   c  are different views of a cam  216 ,  220  that can be used with the third-axis leveling block  214 . The circular boss  400  that fits into the countersunk portions of the holes in the mounting block  300  and in the clamp assembly  306  is clearly shown in all three figures. The dimensions are given in inches and are appropriate for one embodiment. Other embodiments may require other dimensions. The diameter of the hole through the cam  216 ,  220  should be large enough that the cam  216 ,  220  does not bind on the screw  308 ,  312  that passes through it. The offset of the hole to the center of the cam surface (0.62 inches in  FIG. 4   b ) and the outer diameter of the cam surface (0.265 inches in  FIG. 4   b ) determine how much movement is caused when the cam  216 ,  220  pivots. To ease the manufacture of the third-axis leveling block  214 , it is preferred that the two cams  216 ,  220  are identical. 
       FIGS. 5   a ,  5   b , and  5   c  show how pivoting the first cam  216  adjusts the position of the bow-sighting device  108 . In  FIG. 5   a , the first cam  216  is centered, and the bow-sighting device  108  is held horizontal. In  FIG. 5   b , the first cam  216  is rotated counterclockwise from the center position which lifts the bow-sighting device  108  relative to the archery bow  102  (not shown), while in  FIG. 5   c , the first cam  216  is rotated clockwise from the center position which lowers the bow-sighting device  108 . This adjustment allows the archer to keep the rod  226  of the bow-sighting device  108  parallel to the ground and the sighting spot  500  of the bow-sighting device  108  directly above the future flight path of an arrow even though the archery bow  102  is held at a cant. By consulting the level  502 , the archer can maintain a consistent cant when pointing the archery bow  102  uphill or downhill. 
       FIGS. 6   a ,  6   b , and  6   c  show how pivoting the second cam  220  adjusts the position of the bow-sighting device  108 . In  FIG. 6   a , the bow-sighting device  108  is at a median distance from the archer. In  FIG. 6   b , the second cam  220  is rotated counterclockwise which pivots the bow-sighting device  108  away from the archer, while in  FIG. 6   c , the second cam  220  is rotated clockwise which pulls the bow-sighting device  108  toward the archer. This adjustment keeps the bow-sighting device  108  aligned with the flight of an arrow even as the bow  102  twists under full draw. 
     In view of the many possible embodiments to which the principles of the present invention may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the invention. Those of skill in the art will recognize that some implementation details, such as the attachments to the windage block and to the bow-sighting device, are determined by specific situations. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.

Technology Classification (CPC): 5