Crossbow

Abstract

A crossbow including a center rail including a rail body and a riser, a first flexible limb coupled to the riser, a second flexible limb coupled to the riser, and a first cam mounted to the first flexible limb and rotatable around a first cam axis. The first cam including a first draw string journal defining a first draw string plane of rotation perpendicular to the first cam axis, and a first power cable take-up journal extending in a direction perpendicular to the first draw string plane of rotation. The crossbow further including a second cam mounted to the second flexible limb and rotatable around a second cam axis. The second cam including a second draw string journal defining a second plane of rotation perpendicular to the second cam axis, and a second power cable take-up journal extending in a direction perpendicular to the second draw string plane of rotation.

What is claimed is: 
     
         1 . A crossbow comprising:
 a center rail including a rail body and a riser;   a first flexible limb coupled to the riser;   a second flexible limb coupled to the riser;   a first cam mounted to the first flexible limb and rotatable around a first cam axis, the first cam including:
 a first draw string journal defining a first draw string plane of rotation perpendicular to the first cam axis, and 
 a first power cable take-up journal extending in a direction perpendicular to the first draw string plane of rotation; 
   a second cam mounted to the second flexible limb and rotatable around a second cam axis, the second cam including:
 a second draw string journal defining a second plane of rotation perpendicular to the second cam axis, and 
 a second power cable take-up journal extending in a direction perpendicular to the second draw string plane of rotation; 
   a draw string received in the first draw string journal and in the second draw string journal and secured to the first cam and the second cam;   a first power cable received in the first power cable take-up journal with a first end of the first power cable attached to the first cam and a second end of the first power cable attached to the second cam; and   a second power cable received in the second power cable take-up journal with a first end of the second power cable attached to the second cam and a second end of the second power cable attached to the first cam,   wherein the first cam and the second cam are configured so that the draw string unwinds from the first drawstring journal and the second draw string journal as the crossbow is moved from a released configuration to a drawn configuration,   wherein the first cam is configured to rotate more than 270 degrees about the first cam axis as the crossbow is moved from the released configuration to the drawn configuration,   wherein the second cam is configured to rotate more than 270 degrees about the second cam axis as the crossbow is moved from the released configuration to the drawn configuration,   wherein the first power cable take-up journal of the first cam is configured to displace the first power cable away from the first draw string plane of rotation as the crossbow is moved from the released configuration to the drawn configuration, and   wherein the second power cable take-up journal of the second cam is configured to displace the second power cable away from the second draw string plane of rotation as the crossbow is moved from the released configuration to the drawn configuration.   
     
     
         2 . The crossbow of  claim 1 , wherein the first cam is configured to rotate 360 or fewer degrees about the first cam axis as the crossbow is moved from the released configuration to the drawn configuration, and
 wherein the second cam is configured to rotate 360 or fewer degrees about the second cam axis as the crossbow is moved from the released configuration to the drawn configuration.   
     
     
         3 . The crossbow of  claim 2 , wherein the first power cable take-up journal defines a length that accommodates between 270 degrees and 360 degrees of rotation of the first cam, and
 wherein the second power cable take-up journal defines a length that accommodates between 270 degrees and about 360 degrees of rotation of the second cam.   
     
     
         4 . The crossbow of  claim 1 , wherein the first power cable take-up journal includes a first portion and a second portion spaced apart from the first portion in the direction perpendicular to the first draw string plane of rotation, and
 wherein the second power cable take-up journal includes a first portion and a second portion spaced apart from the first portion in the direction perpendicular to the second draw string plane of rotation.   
     
     
         5 . The crossbow of  claim 4 , wherein the first power cable has a first power cable width and the first portion of the first power cable take-up journal is spaced apart from the second portion of the first power cable take-up journal by a distance greater than the first power cable width in the direction perpendicular to the first draw string plane of rotation, and
 wherein the second power cable has a second power cable width and the first portion of the second power cable take-up journal is spaced apart from the second portion of the second power cable take-up journal by a distance greater than the second power cable width in the direction perpendicular to the second draw string plane of rotation.   
     
     
         6 . The crossbow of  claim 1 , wherein the first power cable has a first power cable width and the first power cable take-up journal is configured to displace the first power cable away from the first draw string plane of rotation a distance greater than the first power cable width in the direction perpendicular to the first draw string plane of rotation, and
 wherein the second power cable has a second power cable width and the second power cable take-up journal is configured to displace the second power cable away from the second draw string plane of rotation a distance greater than the second power cable width in the direction perpendicular to the second draw string plane of rotation.   
     
     
         7 . The crossbow of  claim 1 , wherein the first draw string plane of rotation and second draw string plane of rotation are coplanar. 
     
     
         8 . The crossbow of  claim 1 , further comprising:
 a first axle mount fixedly attached to the first flexible limb, wherein the first cam is rotatably coupled to the first axle mount so that the first cam axis is offset from a first limb end by a fixed offset, and   a second axle mount fixedly attached to the second flexible limb, wherein the second cam is rotatably coupled to the second axle mount so that the second cam axis is offset from a second limb end by a fixed offset.   
     
     
         9 . The crossbow of  claim 1 , wherein the first cam axis passes through the first flexible limb and wherein the second cam axis passes through the second flexible limb. 
     
     
         10 . A method of operating a crossbow including a center rail having a rail body and a riser, a first flexible limb coupled to the riser, a second flexible limb coupled to the riser, a first cam mounted to the first flexible limb and rotatable around a first cam axis, the first cam including a first draw string journal defining a first draw string plane of rotation perpendicular to the first cam axis and a first power cable take-up journal extending in a direction perpendicular to the first draw string plane of rotation, a second cam mounted to the second flexible limb and rotatable around a second cam axis, the second cam including a second draw string journal defining a second plane of rotation perpendicular to the second cam axis and a second power cable take-up journal extending in a direction perpendicular to the second draw string plane of rotation, a draw string received in the first draw string journal and in the second draw string journal and secured to the first cam and the second cam, a first power cable received in the first power cable take-up journal with a first end of the first power cable attached to the first cam and a second end of the first power cable attached to the second cam, and a second power cable received in the second power cable take-up journal with a first end of the second power cable attached to the second cam and a second end of the second power cable attached to the first cam, the method comprising the steps of:
 rotating the first cam and the second cam more than 270 degrees to unwind the drawstring from the first drawstring journal and the second draw string journal as the crossbow is moved from a released configuration to a drawn configuration;   wrapping the first power cable onto the first power cable take-up journal and displacing the first power cable away from the first draw string plane of rotation as the crossbow is moved from the released configuration to the drawn configuration; and   wrapping the second power cable onto the second power cable take-up journal and displacing the second power cable away from the second draw string plane of rotation as the crossbow is moved from the released configuration to the drawn configuration.   
     
     
         11 . The method of operating a crossbow of  claim 10 , further comprising rotating the first cam and the second cam 360 or fewer degrees to unwind the drawstring from the first drawstring journal and the second draw string journal as the crossbow is moved the a released configuration to the drawn configuration.