Compound archery bow

The present apparatus is for 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.

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'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.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Referring toFIG. 1, a compound archery bow10has a riser11which is a central mount for the components of the bow and includes a handgrip for gripping the bow. The riser11has a limb12at each end thereof rigidly attached thereto. Each limb has a cylinder13attached to the end thereof, which cylinder has a spring housing14slidably positioned therein. The slidable spring housing may be locked in position with a lock down threaded screw15, as seen inFIG. 4. The spring housing14has a coil spring16mounted thereinside having an end cap17on one end thereof and also having a threaded bolt18at one end of the spring housing14, which threaded bolt can be threaded in or out to pre-compress the coil springs16. Each spring housing14has a yoke20rigidly attached thereto which has a crank21rotatably attached within the yoke20by an axle bolt22. The crank21is in a generally L-shaped configuration with an arm23having a roller24mounted on the end thereof and aligned so that rotation of the crank21in the yoke20attached to the spring housing14will drive the arm23in the roller24against the spring cap17to compress the coil spring16. Each crank21has a pair of lever arms25and26attached thereto and extending therefrom and has a cam27attached thereto with a shaft28extending between the arms25and26to rotatably hold the cam27therein. A bow string30is attached to each cam and wraps around a camming surface31so that pulling on the bow string30will rotate the cams27as well as pull the lever arms25and26and rotate the crank21. The crank21, arm23roller24is pushed against the coil spring cap17to compress the spring16to put a coil spring load onto the bow string30. A pair of timing cables32extend between the pair of cams27, each cable at one end having a loop33formed therein which attaches around a pulley34on each cam with the other end of each cable pinned with a pin35to the side of the cam27.

In operation, an archer, as seen inFIGS. 2 and 3, pulls the bow string30which begins to rotate a pair of cams27and which rotates the arms25and26to rotate the crank21which drives the roller24against the cap17to compress the spring in the spring housing14. Drawing the bow string30, as seen inFIG. 3, further rotates the cam27to further compress each coil spring16for shooting an arrow from the bow10. Since each archer36has a different physical built, the present compound bow is easily adjustable by loosening each lock down screw15to slide each spring housing14in and out of its sleeve13on the end of each limb12to adjust the bow for a particular archer. In addition, the coil spring16can be pre-adjusted by threading the pre-adjustable screw18into or out of the end of the spring housing14to adjust the compression of the coil spring16to adjust the amount of pull required on a bow string30by a particular individual archer36.

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.