Patent Publication Number: US-7708001-B2

Title: Bow

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to an improved bow and particularly to a bow having an improved powerstroke. 
   2. Description of the Prior Art 
   Bows are well known in the art. Over the past several decades, bows have been consistently improved with technological innovations which have dramatically increased performance. One improvement has been the provision of cams on the bow to increase the mechanical advantage associated with the draw of the bowstring. One drawback associated with such cams is the requirement that cams be “synchronized” to prevent lateral travel of the rear of the arrow during launch. Accordingly, the prior art has utilized a single cam arrangement in association with a pulley, such as that described in McPherson, U.S. Pat. No. 6,267,108, which substantially reduces the problem associated with “synchronization” and rear travel of the arrow. 
   For climbing into trees and hunting in thick woods, it is desirable to have a small, lightweight bow. However, reducing the length of the bow risers, and/or sweeping the risers in a more rearward orientation, often reduces the draw length and powerstroke of the bow. Reducing the powerstroke simultaneously sacrifices speed and increases the draw weight required to obtain the desired performance. Accordingly, it would be desirable to provide a lightweight, compact bow with an increased powerstroke, greater speed and reduced draw weight. The difficulties encountered in the prior art discussed hereinabove are substantially eliminated by the present invention. 
   SUMMARY OF THE INVENTION 
   In the advantage provided by this invention, a bow is provided which is of a low-cost, simple manufacture. 
   Advantageously, this invention provides a bow of a compact, lightweight construction. 
   Advantageously, this invention provides a bow with an increased powerstroke. 
   Advantageously, this invention provides a bow which reduces the force required to draw the bowstring. 
   Advantageously, in the preferred embodiment of this invention, a bow is provided with a pair of limbs extending upwardly and rearwardly from a riser. A pulley is coupled to one riser while a cam is coupled to the other. A first string is coupled between the pulley and cam, as is a second string which is located on the side of the pulley and cam closest to the riser. An arrow is notched to the second string, which is drawn and fired. By utilizing the second string to launch the arrow, and drawing the second string from the forward portion from the cam and pulley, the powerstroke is increased, thereby allowing increased speed of the arrow with a reduction in the effort required to launch the arrow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings in which: 
       FIG. 1  illustrates a side elevation of the improved bow of the present invention; 
       FIG. 2  illustrates a side elevation of the cam associated with the improved bow; 
       FIG. 3  illustrates a side elevation of the improved bow of  FIG. 1 , shown drawn with an arrow; and 
       FIG. 4  illustrates a top elevation of an alternative embodiment utilizing the present invention in the form of a crossbow. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A bow according to the present invention is shown generally as ( 10 ) in  FIG. 1 . The bow ( 10 ) includes a riser ( 12 ) provided with a handle ( 14 ) in a manner such as that known in the art. Coupled to the riser ( 12 ) is a first limb ( 16 ) and second limb ( 18 ). A pulley is journaled to the first limb ( 16 ) with an axle ( 20 ) which acts as journal point. The pulley ( 22 ) has an outer track ( 24 ) and an inner track ( 26 ). The pulley ( 22 ) is preferably journaled to the first limb ( 16 ) in a manner which positions a portion of the pulley ( 22 ) rearward and outward of the space defined between the limbs ( 16 ) and ( 18 ). As shown in  FIG. 1 , a second string guide, which in the preferred embodiment is a cam ( 28 ), is journaled to the second limb ( 18 ) at a second journal point ( 30 ). The cam ( 28 ) is journaled to the second limb ( 18 ) so that at least a portion of the cam ( 28 ) extends rearward and outward of the area defined between the limbs ( 16 ) and ( 18 ). The cam ( 28 ) is preferably constructed as shown in  FIG. 2 , having an outer track ( 31 ) and an inner track ( 33 ), but may be constructed in any manner known in the art. If desired, an additional cam (not shown) synchronized with the cam ( 28 ) may be used in place of the pulley ( 22 ). 
   The cam ( 28 ) and pulley ( 22 ) may be coupled to a bowstring ( 32 ) and, if desired, one or more cables( 34 ) in any manner known in the art, but the bowstring ( 32 ) is preferably located, as shown in  FIG. 1 , forward of the first axle ( 20 ) and second axle ( 30 ). When the bowstring ( 32 ) is drawn, as shown in  FIG. 3 , the bowstring ( 32 ) contacts the pulley ( 22 ) and cam ( 28 ) at points located between the first axle ( 20 ) and second axle ( 30 ). 
   As shown in  FIG. 1 , the foregoing orientation of the pulley ( 22 ), cam ( 28 ), cable ( 34 ) and bowstring ( 32 ) in the rest position between the axles ( 20 ) and ( 30 ), and the riser ( 12 ). When it is desired to utilize the bow ( 10 ) of the present invention, an arrow ( 36 ) having a shaft ( 38 ), flights ( 40 ), a head ( 42 ) and a nock ( 44 ) is provided. The nock ( 44 ) is coupled to a nock point ( 46 ) provided in the bowstring ( 32 ). The shaft ( 38 ) of the arrow ( 36 ) sits upon the arrow rest ( 48 ) provided on the riser ( 12 ). The arrow ( 36 ) is thereafter drawn rearward by the nock ( 44 ) as shown in  FIG. 3 . By threading the bowstring ( 32 ) across the forward and upward portion of the pulley ( 22 ) and forward and downward portion of the cam ( 28 ), the draw length of the bow ( 10 ) is increased over a prior art bow, thereby increasing the powerstroke and speed of the arrow ( 36 ) upon release, while decreasing the effort required to draw the arrow ( 36 ) to the full draw length ( 50 ). Once the full draw length ( 50 ) has been obtained, the nock ( 44 ) may be released, thereby launching the arrow ( 36 ) at the desired target. 
   An alternative embodiment of the present invention is shown generally as a crossbow ( 52 ) in  FIG. 4 . The crossbow ( 52 ) is provided with a frame ( 54 ) which includes a stock ( 56 ) and a rail ( 58 ). Although the stock ( 56 ) and rail ( 58 ) may be of any type known in the art, in the preferred embodiment, the stock ( 56 ) is of a composite material construction and the rail ( 58 ) is constructed of aluminum. Alternatively, the crossbow ( 52 ) may be of a “rail-less” design, such as those known in the art. 
   The crossbow ( 52 ) is provided with a pivotable foot stirrup ( 60 ) to facilitate cocking of the crossbow ( 52 ). As shown in  FIG. 4 , the crossbow ( 52 ) is also provided with a pair of risers ( 62 ) and ( 64 ) secured to the rail ( 58 ). The risers ( 62 ) and ( 64 ) are preferably constructed of aluminum to reduce weight. Coupled to the risers ( 62 ) and ( 64 ) are a first limb ( 66 ) and a second limb ( 68 ). The limbs ( 66 ) and ( 68 ) are constructed and coupled to the risers ( 62 ) and ( 64 ) in a manner such as that known in the art. Journaled to the first limb ( 66 ) at a first journal point ( 70 ) is a pulley ( 72 ). Journaled to the second limb ( 68 ) at a second journal point ( 74 ) is a cam ( 76 ). As described above, the crossbow ( 52 ) is provided with a bowstring ( 78 ) coupled to the pulley ( 72 ) at a position located between the first journaled point ( 70 ) and the riser ( 62 ). Similarly, the bowstring ( 78 ) is coupled to the cam ( 76 ) at a position located between the second journal point ( 74 ) and the riser ( 64 ). By locating the bowstring ( 78 ) forward and inward of the both the pulley ( 72 ) and cam ( 76 ), the powerstroke ( 80 ) of the crossbow ( 52 ) is increased, which increases the speed of a bolt ( 82 ) launched by the crossbow ( 52 ), and decreasing the draw weight associated with cocking the crossbow ( 52 ). 
   As shown in  FIG. 4 , when it is desired to operate the crossbow ( 52 ), the foot stirrup ( 60 ) is engaged and the bowstring ( 78 ) is pulled to engage the bowstring ( 78 ) with the catch mechanism ( 84 ). The bolt ( 82 ) is then placed upon the rail ( 58 ). A trigger assembly ( 86 ) such as that known in the art is thereafter actuated to release the catch mechanism ( 84 ) and cause the bowstring ( 78 ) to propel the bolt ( 82 ) along the rail ( 58 ) and toward the desired target. 
   Although the invention has been described with respect to a preferred embodiment thereof, it is also to be understood that it is not to be so limited, since changes and modifications can be made therein which are within the full, intended scope of this invention as defined by the appended claims. As an example, the bow ( 10 ) of the present invention may be utilized in association with two cams. Another alternative anticipated by the present invention is a bow having the riser and limbs integrally formed of a single unit.