Patent Publication Number: US-8522763-B2

Title: Compound archery bow

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a compound, spring loaded archery bow and especially to an improved compound spring loaded archery bow having pre-adjustments for the compression spring and positioning of the compression spring housing to accommodate different archers. 
     The traditional archery bow is comprised of a riser having a hand grip and an arrow rest and a pair of resilient limbs attached to each end of the riser. The resilient limbs of the bow form a resilient spring. The bow string is attached to the free end of each resilient limb so that when the bow string is drawn back from its initial position by an archer to shoot an arrow, the resilient limbs flex to place the bow string under tension. The further the archer draws the bow string back, the more the resilient limbs of the bow are flexed which imparts greater tension to the bow string. When the bow string is released to shoot an arrow, the resilient limbs of the bow snap back to their original position to force the bow string back to its initial position to propel the arrow towards a target. These traditional bows are frequently made of strong composite materials but they do have drawbacks. For instance, once an archer selects a particular archery bow, he is restricted with that bow to a maximum drawing force so that the archer is unable to vary the poundage range for a particular bow. 
     A compound archery bow uses a levering system and typically has cams and pulleys on the limbs. The limbs which act as a release spring in a compound bow are usually much different than those of a traditional archery bow. Stiffness makes the compound bow more energy efficient than other bows so that they are too stiff to be drawn with a string attached directly to them. A compound bow attaches a bow string to cams or pulleys to give a mechanical level to the bow string. Thus, when you pull the cables on a compound bow, it causes the cams to rotate to bend the limbs of a bow. A compound bow has a rigid handgrip or riser having limbs attached to each end and have the sights and the like attached thereto. 
     Prior art compound bows have typically used limbs that form leaf springs while other compound bows have used other springs for loading the bow. An earlier spring loaded archery bow can be seen in the D. M. Holmes U.S. Pat. No. 428,912 in which each limb of the bow is connected to a central coil spring passing through a tube to give the back bow increased power. In U.S. Pat. No. 4,458,657 to Stockmar, a compound archery bow is a complicated structure with both a main frame and a handle grip and a bow string tensioning assembly located forward of the main frame. The bow string tensioning assembly is formed by exposed resilient tubes for tensioning the bow string which are stretched and placed in tension when the bow string of the bow is drawn. 
     In the York U.S. Pat. No. 7,201,161, a compound spring loaded archery bow has separate upper and lower spring tensioning assemblies and cam mechanisms for applying tension to the bow string of the bow. Separate upper and lower spring tensioning assemblies are contained within the upper and lower rigid limbs of the bow so that the bow retains the appearance of a traditional archery bow. In the Dieziger U.S. Pat. No. 6,055,974 a compound bow has a facilitated draw for allowing a bow string to be more easily drawn and uses a pair of coil springs. In the L. J. Mulkey U.S. Pat. No. 2,714,377, an archer&#39;s bow uses a pair of coil springs. The Guzzetta U.S. Pat. No. 4,756,295 is a compound bow which uses a toggle-like assembly to improve the accuracy and acceleration of the bow. It utilizes a single coil spring. 
     The present archery bow is spring loaded with a pair of coiled springs mounted to each limb of the bow, which coil springs are pre-adjustable for both pull and which also allows the spring housings to be adjusted for a particular archer. 
     SUMMARY OF THE INVENTION 
     A compound spring loaded archery bow has a riser having a handle portion with a grip thereon and a rigid limb attached to each end thereof. A spring housing is slidably mounted on the end of each limb and has a compression spring located in each housing. A crank is rotatably attached to each spring housing for rotation thereon and includes a crank arm having one end positioned against one end of the spring for compressing each spring when the crank is rotated. Each crank arm may have a roller on the end thereof for reducing friction on a spring cap covering the end of the coil spring when compressing and expanding the spring. The lever arm is attached to each crank and extends therefrom. A cam is rotatably attached to each lever arm for rotation thereon. A bow string is attached to each cam and extends therebetween for rotating each cam and each lever arm and crank to compress both compression springs when the bow string is pulled back for shooting an arrow. Each lever arm may be two lever arms forming a yoke for holding the rotatable cam therein. Timing cables are connected between the cams to synchronize the cams. The compound bow may have a threaded compression adjustment in each coil spring housing for preadjusting the compression of the spring therein. Each spring housing is slidably mounted in the end of one limb and can be locked in position for adjusting the position of the spring housing and cams for different users of the compound bow. The compound bow rotates a pair of cams and a pair of cranks to compress a pair of compression springs when shooting an arrow, which compression springs may be pre-adjusted for compression and in which the spring housings may be adjusted for different users. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features, and advantages of the present invention will be apparent from the written description and the drawings in which: 
         FIG. 1  is a side elevation of a compound bow in accordance with the present invention; 
         FIG. 2  is a side elevation of an archer pulling the bow string of the bow of  FIG. 1 ; 
         FIG. 3  is a side elevation in accordance with  FIG. 2  in which the archer has further extended the bow string; and 
         FIG. 4  is a partial cutaway perspective view of the compound bow of  FIGS. 1 through 3 . 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
     Referring to  FIG. 1 , a compound archery bow  10  has a riser  11  which is a central mount for the components of the bow and includes a handgrip for gripping the bow. The riser  11  has a limb  12  at each end thereof rigidly attached thereto. Each limb has a cylinder  13  attached to the end thereof, which cylinder has a spring housing  14  slidably positioned therein. The slidable spring housing may be locked in position with a lock down threaded screw  15 , as seen in  FIG. 4 . The spring housing  14  has a coil spring  16  mounted thereinside having an end cap  17  on one end thereof and also having a threaded bolt  18  at one end of the spring housing  14 , which threaded bolt can be threaded in or out to pre-compress the coil springs  16 . Each spring housing  14  has a yoke  20  rigidly attached thereto which has a crank  21  rotatably attached within the yoke  20  by an axle bolt  22 . The crank  21  is in a generally L-shaped configuration with an arm  23  having a roller  24  mounted on the end thereof and aligned so that rotation of the crank  21  in the yoke  20  attached to the spring housing  14  will drive the arm  23  in the roller  24  against the spring cap  17  to compress the coil spring  16 . Each crank  21  has a pair of lever arms  25  and  26  attached thereto and extending therefrom and has a cam  27  attached thereto with a shaft  28  extending between the arms  25  and  26  to rotatably hold the cam  27  therein. A bow string  30  is attached to each cam and wraps around a camming surface  31  so that pulling on the bow string  30  will rotate the cams  27  as well as pull the lever arms  25  and  26  and rotate the crank  21 . The crank  21 , arm  23  roller  24  is pushed against the coil spring cap  17  to compress the spring  16  to put a coil spring load onto the bow string  30 . A pair of timing cables  32  extend between the pair of cams  27 , each cable at one end having a loop  33  formed therein which attaches around a pulley  34  on each cam with the other end of each cable pinned with a pin  35  to the side of the cam  27 . 
     In operation, an archer, as seen in  FIGS. 2 and 3 , pulls the bow string  30  which begins to rotate a pair of cams  27  and which rotates the arms  25  and  26  to rotate the crank  21  which drives the roller  24  against the cap  17  to compress the spring in the spring housing  14 . Drawing the bow string  30 , as seen in  FIG. 3 , further rotates the cam  27  to further compress each coil spring  16  for shooting an arrow from the bow  10 . Since each archer  36  has a different physical built, the present compound bow is easily adjustable by loosening each lock down screw  15  to slide each spring housing  14  in and out of its sleeve  13  on the end of each limb  12  to adjust the bow for a particular archer. In addition, the coil spring  16  can be pre-adjusted by threading the pre-adjustable screw  18  into or out of the end of the spring housing  14  to adjust the compression of the coil spring  16  to adjust the amount of pull required on a bow string  30  by a particular individual archer  36 . 
     It should be clear at this time that a compound spring loaded archery bow has been provided which advantageously can be adjusted for individual archers both in terms of the positioning of the bow string relative to the riser and limbs as well as adjusting the force required to pull the bow string. However, the present invention is not to be construed as limited to the forms shown which are to be considered illustrative rather than restrictive.