Crossbow utilizing cams

Abstract

A crossbow includes a frame including a riser, a first and a second cam, a first and a second flexible limb, a first power cable, a second power cable, and a drawstring. Each cam has a larger diameter portion and a smaller diameter portion. The first power cable has a first end attached to a mounting position on the riser and a second end attached to the smaller diameter portion of the first cam. The second power cable has a first end attached to a mounting position on the riser and a second end attached to the smaller diameter portion of the second cam. The drawstring is attached to the larger diameter portion of the first cam and the larger diameter portion of the second cam. The drawstring wraps at least one full wind around the larger diameter portions of the cams when the crossbow is undrawn.

1 - 28 . (canceled) 
     
     
         29 . A crossbow, comprising:
 a frame defining a projectile axis;   a first cam and a second cam, the first cam and the second cam each coupled to the frame, each of the first cam and the second cam having a larger diameter portion and a smaller diameter portion, the first cam positioned to a first side of the projectile axis and rotatable about a first axis, the second cam positioned to a second side of the projectile axis and rotatable about a second axis, the first axis fixed relative to the frame, the second axis fixed relative to the frame;   a first flexible limb and a second flexible limb, each of the first flexible limb and the second flexible limb having a first end and a second end, the first end of the first flexible limb coupled to the frame positioned to the first side of the projectile axis, the first end of the second flexible limb coupled to the frame and positioned to the second side of the projectile axis;   a first power cable having a first end and a second end, the first end of the first power cable coupled to the frame at a first mounting position on the frame, the second end of the first power cable coupled to the smaller diameter portion of the first cam;   a second power cable having a first end and a second end, the first end of the second power cable coupled to the frame at a first mounting position on the frame, the second end of the second power cable coupled to the smaller diameter portion of the second cam; and   a drawstring coupled to the larger diameter portion of the first cam and to the larger diameter portion of the second cam and configured to move between an undrawn position and a drawn position;   wherein the drawstring is wound more than one full rotation around the larger diameter portion of the first cam and the larger diameter portion of the second cam with the drawstring in the undrawn position.   
     
     
         30 . The crossbow of  claim 29 , wherein each of the first flexible limb and the second flexible limb are in an unloaded position when the crossbow is undrawn and a loaded position when the crossbow is drawn. 
     
     
         31 . The crossbow of  claim 29 , wherein the first power cable is engaged with the first flexible limb, wherein the second power cable is operatively engaged with the second flexible limb. 
     
     
         32 . The crossbow of  claim 29 , wherein the larger diameter portion and the smaller diameter portion of each of the first cam and the second cam are integrally formed. 
     
     
         33 . The crossbow of  claim 29 , further comprising a first pulley and a second pulley, the first pulley coupled to the frame and positioned to the first side of the projectile axis, the second pulley coupled to the frame and positioned to the second side of the projectile axis, wherein the first power cable is routed from the smaller diameter portion of the first cam to the first pulley, wherein the second power cable is routed form the smaller diameter portion of the second cam to the second pulley. 
     
     
         34 . The crossbow of  claim 29 , wherein, during operation with the drawstring in the drawn position, the first power cable and the second power cable respectively wrap at least one full rotation around each the smaller diameter portion of the first cam and the smaller diameter portion of the second cam. 
     
     
         35 . The crossbow of  claim 29 , wherein each of the first power cable and second power cable respectively wrap around the smaller diameter portion of the first cam and the smaller diameter portion of the second cam less than one full rotation with the drawstring in the undrawn position and more than one full rotation with the drawstring in the drawn position. 
     
     
         36 . A crossbow comprising:
 a frame defining a projectile axis;   a first cam and a second cam each coupled to the frame, each of the first cam and the second cam having a larger diameter portion and a smaller diameter portion, the first cam configured to rotate about a first axis that is fixed relative to the frame, the second cam configured to rotate about a second axis that is fixed relative to the frame;   a first flexible limb and a second flexible limb, each of the first flexible limb and the second flexible limb having a first end coupled to the frame and a second end;   a first power cable having a first end coupled to the smaller diameter portion of the first cam;   a second power cable having a first end coupled to the smaller diameter portion of the second cam;   a drawstring having a first and a second end, the first end of the drawstring coupled to the larger diameter portion of the first cam, the second end of the drawstring coupled to the larger diameter portion of the second cam, the drawstring movable from an undrawn position to a drawn position; and   a drawstring carrier slidably engaged with the frame and configured to move the drawstring from the undrawn position to the drawn position;   wherein (i) the drawstring is wound more than one full rotation around the larger diameter portion of the first cam and the larger diameter portion of the second cam and (ii) the first power cable and second power cable are wound less than one full rotation with the drawstring in the undrawn position.   
     
     
         37 . The crossbow of  claim 36 , wherein the first power cable is operatively engaged with the first flexible limb, wherein the second power cable is operatively engaged with the second flexible limb. 
     
     
         38 . The crossbow of  claim 37 , wherein the second end of the first power cable is coupled to a first side of the frame, wherein the second end of the second power cable is coupled to a second side of the frame. 
     
     
         39 . The crossbow of  claim 36 , further comprising a first pulley and a second pulley, the first pulley coupled to the frame and positioned to a first side of the projectile axis, the second pulley coupled to the frame and positioned to a second side of the projectile axis, wherein the first power cable is routed from the smaller diameter portion of the first cam to the first pulley, wherein the second power cable is routed form the smaller diameter portion of the second cam to the second pulley. 
     
     
         40 . The crossbow of  claim 39 , wherein the second end of the first power cable is coupled to the first side of the frame, wherein the second end of the second power cable is coupled to the second side of the frame. 
     
     
         41 . The crossbow of  claim 39 , the frame defining a front end and a rear end, wherein the first pulley is positioned between the first cam and the rear end, wherein the second pulley is positioned between the second cam and the rear end. 
     
     
         42 . The crossbow of  claim 36 , wherein first power cable and the second power cable are positioned vertically below the drawstring. 
     
     
         43 . The crossbow of  claim 36 , wherein, during operation with the drawstring in the drawn position, the first power cable and the second power cable respectively wrap at least one complete rotation around each the smaller diameter portion of the first cam and the smaller diameter portion of the second cam. 
     
     
         44 . A crossbow comprising:
 a frame including a riser, the frame defining a projectile axis;   a first cam and a second cam each coupled to the riser, each of the first cam and the second cam having a larger diameter portion and a smaller diameter portion, the first cam positioned to a first side of the projectile axis and rotatable about a first axis, the second cam positioned to a second side of the projectile axis and rotatable about a second axis, the first axis fixed relative to the riser, the second axis fixed relative to the riser;   a first flexible limb and a second flexible limb, each of the first flexible limb and the second flexible limb having a first end coupled to the frame and a second end;   a first power cable having a first end coupled to the smaller diameter portion of the first cam and a second end coupled to the frame and positioned to the first side of the projectile axis, the first power cable operatively engaged with the second end of the first flexible limb;   a second power cable having a first end coupled to the smaller diameter portion of the second cam and a second end coupled to the frame and positioned to the second side of the projectile axis, the second power cable operatively engaged with the second end of the second flexible limb;   a drawstring having a first and a second end, the first end of the drawstring coupled to the larger diameter portion of the first cam, the second end of the drawstring coupled to the larger diameter portion of the second cam, the drawstring movable from an undrawn position to a drawn position; and   a drawstring carrier slidably engaged with the frame and configured to move the drawstring from the undrawn position to the drawn position;   wherein the drawstring is wound more than one full rotation around the larger diameter portion of the first cam and the larger diameter portion of the second cam.   
     
     
         45 . The crossbow of  claim 44 , wherein the larger diameter portion of first cam and the larger diameter portion of the second cam respectively include a helical groove to wind the drawstring more at least two full rotations with the drawstring in the undrawn position, wherein the first axis and the second axis are substantially perpendicular to the projectile axis. 
     
     
         46 . The crossbow of  claim 44 , further comprising a first pulley and a second pulley, the first pulley coupled to the frame and positioned to the first side of the projectile axis, the second pulley coupled to the frame and positioned to the second side of the projectile axis, wherein the first power cable is routed from the smaller diameter portion of the first cam to the first pulley, wherein the second power cable is routed form the smaller diameter portion of the second cam to the second pulley. 
     
     
         47 . The crossbow of  claim 44 , wherein each of the first power cable and second power cable respectively wrap around the smaller diameter portion of the first cam and the smaller diameter portion of the second cam less than one full rotation with the drawstring in the undrawn position and more than one full rotation with the drawstring in the drawn position. 
     
     
         48 . The crossbow of  claim 47 , wherein first power cable and the second power cable are positioned vertically below the drawstring.