Mechanical guns and projectors – Spring – Bow
Reexamination Certificate
2000-05-25
2001-06-26
Ricci, John A. (Department: 3712)
Mechanical guns and projectors
Spring
Bow
C124S900000
Reexamination Certificate
active
06250293
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to archery bows and, more particularly, to an adjustable cam for an archery bow.
2. Description of the Related Art
Compound archery bows are well known and may utilize one or more cams to more efficiently store energy in the bow limbs as a drawstring of the bow is drawn. Additionally, a compound bow provides a let-off or reduction of the force required to pull the drawstring during a portion of the draw, and may be adapted to limit the maximum draw length of the bow. Both improve the performance and ease of use of the bow. Compound bows may utilize a single cam and an idler wheel on opposed limbs of the bow or a pair of cams, one at the free end of each limb of the bow.
Some archery bows utilize one-piece unitary cams that have one or more grooves formed therein to receive the strings of the bow and one or more posts to which the free end of a bowstring may be attached. To change the characteristics of the bow, such as the draw length, location in the draw and intensity of the let-off of the draw, the user of the bow must completely disassemble the bow and replace the existing cams with replacement cams having different characteristics. Notably, the bow must be disassembled with the use of a bow press to safely remove the bowstring from the limbs which are all under tension. After changing, the cams, the bow must be reassembled and readjusted to enable and optimize its use with the new cams. Further, the new cams are just as inflexible as the old cams in that they have fixed characteristics that cannot be readily altered by a user. Thus, the one-piece cams are very limited, difficult and expensive to change, and very costly to manufacture as several distinct cams must be manufactured for the various draw lengths and let-offs desired by consumers.
So-called modular cams have also been used on archery bows. These modular cams have a one-piece main body as in prior cams, and a plurality of individual modules which can be mounted one at a time onto the cam body with each having a different shape and hence, different characteristics in use. Each individual module is distinct from one another and may be individually fixed to the cam in a single location to provide the desired characteristics to the cam and hence the archery bow. For example, modules having different profiles or contours may be placed on a cam to change the intensity of the let-off, which is usually stated as a percent of the draw weight, or the location in the draw where the let-off is initiated. Thus, to vary the let-off within a range of intensity of let-offs, a plurality of independent and distinct modules must be used.
Additionally, to limit the draw length of the bow, some cams have been adapted to receive “draw stops” which engage either a string or a limb of the bow at the maximum draw length of the bow to prevent the bow from being overdrawn. Conventional draw stops are typically small knobs attached to the cam by a screw. Such draw stops may vibrate loose from the cam and be lost during use. Still further, the engagement of the small knob with the limb or a bowstring provides a very abrupt stop and a “jerky,” unsmooth feel to the bow that is undesirable to consumers. Still further, movement of the draw stop relative to the cam, or to a module on the cam, can undesirably change the performance, efficiency and accuracy of the bow. An incorrectly placed draw stop can reduce the efficiency of the bow, cause a loss in accuracy of an arrow shot from the bow and result in a decrease in speed of an arrow shot from the bow.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a cam for a compound archery bow. The cam may include an adjustable draw cam and a draw stop arm each releasably and adjustably carried by the cam to permit rapid adjustment of the draw length and let-off characteristics of the cam without having to completely disassemble the bow, i.e., without having to replace either of the adjustable draw cam or draw stop arm with different components. Therefore, a plurality of draw lengths as well as let-offs may be achieved by the consumer without having to completely disassemble the bow or purchase a plurality of different, specialized parts. Advantageously, the number of different parts needed to produce a wide range of draw lengths and let-offs is drastically reduced to greatly facilitate the economical manufacture of cams for archery bows.
Preferably, the draw stop arm is an elongated arm releasably carried by the cam. The draw stop arm engages a bowstring during at least a portion of the rotation of the cam during the draw of the bow, and is movable between a plurality of positions to alter its engagement with the bowstring. Repositioning the draw stop arm affects the draw length and magnitude of the let-off of the bow. The draw stop arm may include an elongated track or groove therein that receives the bowstring at the end of the draw. Preferably, as the bowstring is drawn, it increasingly engages the draw stop arm to provide a softer or more controlled limit to the draw length of the bow. If desired, the groove or track in the arm may have a radius or may be generally arcuate to further control engagement of the bowstring with the arm to provide an improved feel to the user. The draw stop arm may be of substantially any shape and may even comprise more than one piece so long as at the maximum draw length of the bow the string of the bow is engaged by the draw stop over a distance of at least ¼ of an inch and preferably ½ of an inch or more.
In the preferred embodiment, the arm is pivotally carried at one end on the cam for pivotal movement about an axle that mounts the cam on the limb of the bow with the other end of the arm movable and releasably securable to the cam in a plurality of positions. Desirably, each position relates to a specific increment of draw length ranging from {fraction (1/16)} of an inch up to 1 inch or more as desired. This provides tremendous flexibility to the user of the bow by enabling them to choose between a wide range of draw lengths and let-offs without having to disassemble the bow.
The adjustable draw cam is also releasably carried by the cam. The adjustable draw cam engages the bowstring during the draw of the bow and is movable between a plurality of positions on the cam to vary the draw length of the bow and the locations of and optionally, the intensity of the let-off. The adjustable draw cam may include a track or groove that receives the bowstring. Preferably, the adjustable draw cam includes a comer or radius around which the bowstring is wrapped as the cam rotates during the draw of the bow. A portion of the corner or radius extends generally tangentially to the axle of the cam and defines the point on the cam wherein the let-off begins and which may be referred to as a “break over radius.” After the bowstring engages and wraps around this corner or break over radius, the let-off is initiated to reduce the force needed to pull the drawstring further or to hold the drawstring. The adjustable draw cam may be generally circular and may be axially or eccentrically mounted on the cam. Alternatively, the draw cam may have an irregular shape contoured to maximize the performance and versatility of the bow. By changing the position of the same adjustable draw cam relative to the cam, the position of the break over radius is changed, thereby changing the location at which the let-off is initiated and, in part, the draw length of the bow.
Desirably, both the draw stop arm and draw cam are independently movable between a plurality of positions to greatly increase the flexibility of the bow by enabling a consumer to rapidly and easily change the draw length and let-off characteristics. Advantageously, a single cam with a draw stop arm and a draw cam may be used in place of a plurality of one-piece cams or a plurality of differently shaped modules. This greatly simplifies and decreases the number of parts required to provide a wide range of draw lengths a
High Country Archery
Ricci John A.
Warn, Burgess & Hoffman, PC
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