The present invention pertains to archery bows and more particularly to archery bows having modules attachable to cams for adjusting draw weight and draw length.
Archery bows must be customized to fit each specific archer; particularly, each archer has a unique desired draw length and is usually limited to a particular maximum draw weight. Manufacturers and dealers of archery bows thus must produce a variety of bows each having a particular draw weight or draw length so that the archery bow is properly matched to the individual archer. Draw length and draw weight can be changed by archery dealers but such changes are usually limited and require dedicated equipment to accomplish the modifications. Further, such modifications are time consuming and require skill to properly make changes to the draw weight and draw length to fit a particular archer.
The present invention incorporates the utilization of modules that are attachable to the cams of a compound bow. In the example chosen for illustration, the bow is a dual cam bow; however, the same concept is applicable to a one cam bow. The modules are attachable to the faces or surfaces of a cam and are positionable by translational movement. The modules provide a groove for contacting the cable or cables of the archery bow and include dual profiles along the periphery of the module to permit the module to be reversed or “flipped” to permit the engagement of an opposite surface of the module with the mounting surface of the cam. In the “flipped” position, a different peripheral portion of the cable-engaging groove is presented to the cable during draw. The peripheral profiles of each portion is different with respect to each other such that a draw length provided by one sector on the periphery of the module is different than the draw length provided by the second peripheral sector of the module when the module has been flipped.
Referring to
Referring to
In
The module is formed having parallel opposing flat surfaces 50 and 51 (
Draw length adjustment using modules such as module 40 is accomplished by changing the amount the cam 20 rotates before reaching a stop position at full draw. Typical cam rotation during draw is in the range of 140° to 220° from brace height to full draw. The reversible module 40 relies upon cam rotation that is a fixed amount less than or greater than 180° and which rotation can be combined into a single module 40. For example, module 40 can be configured to create two distinct draw lengths depending on which flat surface of the module is placed in contact with the corresponding flat surface of the cam. For example
Bow limbs act as energy storage springs and are governed by the basic linear spring equation F=kx (where F=Force, k=spring constant and x=spring deflection). The draw force on the bowstring is directly related to the forces generated by the bow limbs and the mechanical advantage provided by the cam at each rotational position. Bow draw weight changes may be made by adjusting the effective spring constant (k) of the limb to change the draw force (F). Minor adjustments may be made by turning the limb screw bolt 17 in or out, although such adjustments must be limited to prevent accidental dislodgement of the bolt if backed out too far. Adjusting module position acts to increase or decrease both the limb force and the leverage in the draw cycle. At the same time the limb movement is increased or decreased, the mechanical advantage of the cam is inversely decreased or increased. The combination of increased limb movement with decreased leverage changes the effective peak draw weight. Referring to
This interrelationship of the guide slot and guide permits sliding translational movement of the modules over the cam surface. It may be noted that the module does not change its angular position with respect to the cam 20 but merely translates by movement along the slot 56. This translational movement provides insurance against rotational relative movement between the module and the cam and also assists the archer in selecting the appropriate position of the module. Further, the interaction of the guide member 59 and guide slot 56 may permit transmission of torque forces transmitted from and between the cam and module.
Thus it may be seen that a pair of modules, one each for the upper and lower cams of a dual cam bow, may be used as in the example given above. That is, each module may be attached to a corresponding cam to provide a selected draw length; that same cam may be positioned on the corresponding cam by sliding/translational movement to a desired draw weight position. Thus, the individual modules permits the selection of two draw lengths combined with a selection of three draw weights for each selected draw length. Thus, an archery dealer having an inventory of selected bows may provide a prospective purchaser with a bow of the characteristics chosen by the purchaser together with a set of attachable modules to permit the purchaser to customize the bow. The combination of available draw lengths and draw weights permits the purchaser to select the appropriate weight and draw length while permitting the dealer to stock fewer bows since each bow can be customized over a broad range of draw weights and draw lengths.
As an example of the implementation of the present invention, the following chart provides a selection of module sizes together with the available draw lengths and weight settings available with the respective modules. Assuming for example, the archer desires a 28″ draw length. From the chart below it may be seen that he would select module C″. If the archer desired an approximate 65 pound peak draw weight, the archer would select the medium or “M” translational position of the module on the cam. With the module thus in the proper position on the cam, the module is then secured to the cam with two screw fasteners that are aligned with corresponding threaded holes in the cam. Minor weight adjustments may subsequently be made by turning the limb screw bolts to “fine tune” the desired weight.
Thus, it may be seen that the dealer may stock a single bow and provide that bow to an archer with a total of eighteen selected values for draw weight and length.
The present invention has been described in terms of selected specific embodiments of the apparatus and method incorporating details to facilitate the understanding of the principles of construction and operation of the invention. Such reference herein to a specific embodiment and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications may be made in the embodiments chosen for illustration without departing from the spirit and scope of the invention.
The present application claims priority to a provisional application filed Sep. 28, 2006 under Ser. No. 60/827,311 entitled “REVERSIBLE AND ADJUSTABLE MODULE SYSTEM FOR ARCHERY BOW”.
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