ARCHERY BOW MODULAR CAM SYSTEM

Abstract

A modular cam system for an archery bow or crossbow includes swappable cams that change the maximum draw weight of the archery bow or crossbow. Moreover, the modular cams can be affixed to a rotatable member in a number of orientations to set the desired draw length without changing the limbs, tightening or loosening limb bolts, or disassembling the bow. Further, the maximum draw weight of the bow remains substantially similar throughout a large portion of the draw length adjustment for a specified cam module.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. patent application Ser. No. 16/831,418, filed Mar. 26, 2020, which is a continuation of U.S. patent application Ser. No. 15/788,694, filed Oct. 19, 2017, which is a continuation of U.S. patent application Ser. No. 13/629,388, filed Sep. 27, 2012, which claims the benefit of and priority to U.S. Provisional Patent Application No. 61/539,885, filed Sep. 27, 2011, the entire contents of all of which are hereby incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

This invention relates generally to archery bows and more specifically to compound bows having cam adjustability.

Various types of compounding archery bows are generally known in the art. Compounding archery bows generally include a plurality of rotatable members, at least one of which comprises a cam. The cam desirably provides for a reduction in the draw weight when the bow is fully drawn, allowing an archer to hold the bow in a drawn position with less fatigue.

Some compounding bows include at least one rotatable member having a cam, wherein at least a portion of the cam is either adjustable with respect to the rest of the rotatable member or can be removed entirely and replaced with another cam module having a different shape.

U.S. Pat. No. 4,461,267 teaches a bow wherein interchangeable modules having different cam shapes are used to change the draw length of the bow. The bow's peak draw weight was determined solely by the spring rate or stiffness of the bows limbs, which were generally fixed in the bow handle. The Bear Delta V bow, which embodied the invention of U.S. Pat. No. 4,461,267, was marketed in one of two different fixed draw weights. The draw length of the bow was determined by a cam module, which represented one module from a set of modules that could be attached to the rotatable member body.

U.S. Pat. No. 4,461,267 teaches that each of the available draw length modules are very similar to one another through the initial portion of the draw length, until the draw force reaches its peak (represented by point “C” in FIG. 2 of U.S. Pat. No. 4,461,267). The various draw weight modules result in the same peak draw weight with that draw weight dropping off more rapidly with each progressively shorter draw weight module.

One of the first patents to introduce draw length module cams mounted on the ends of the bows limbs was U.S. Pat. No. 4,515,142. This patent basically applied the teaching of the previous '267 patent to cams at the bows limb tips rather than to cams mounted on pylons extending from the handle of the bow. In the '142 patent, it is taught that a main cam body can be designed such that it can accept individual modules that can be designed to provide a specific draw weight and the draw length of the bow can be changed by interchanging a replaceable module. The main short coming of this concept is that each module only provides a single draw force profile capability; therefore it would require a multitude of different designed modules to cover all of the normal draw weight and draw length combinations encountered in market place.

Larry D. Miller's U.S. Pat. No. 4,519,374 teaches a modular cam concept that is similar to Nurney's '142 concept in that it requires a different set of attached modules to provide a specific draw force profile. Miller's concept is intended to provide some of the same benefits as the Nurney concept. However, the '374 concept is even more complex in that it can require a number of add on plates or modules to arrive at a single given draw force configuration.

U.S. Pat. No. 4,774,927 issued to Marlow Larson teaches a different type of modular cam concept that is designed to provide variability in the let-off performance of the bow. In particular, by adjusting the modules, the user can change the cam ratio of the bow in the segment of draw after peak weight. In combination, by adjustment of the modules, the user can select the ultimate draw length. Having selected the desired let-off (holding weight), the '927 concept offers the ability to make small incremental rotations of the module which in turn results in an incremental change in the bows draw length, as illustrated in FIGS. 11 and 12 and explained in the body of the '927 patent. While this concept requires only one module on each cam that is not readily replaceable or subject to loss, the resulting system is limited in that it does not offer draw weight change capability.

Larson U.S. Pat. No. 5,678,529 is a continuation-in-part of a series of patents including the '927 patent. This patent is a variation on the rotating module concept, emphasizing the design of a rotating module that is capable of maintaining somewhat consistent peak draw weight while being adjustable in six, not necessarily uniform, draw lengths. FIG. 21 and the corresponding table included in this patent shows some of the limitations of this concept, which is also somewhat complex.

Additionally, Published Application No. US 2010/0147276, listing inventors Dennis Wilson and Rex F. Darlington, discloses a “Compound Archer Bow With Replaceable Draw Length Adjustment Modules”. Mr. Darlington has been a prolific inventor in the area of compound bow cam design, and Publication No. 2010/0147276 embodies one of his latest concepts utilizing replaceable modules. This Publication teaches the use of modules as a means to affect the draw length of the bow, with a given module pair applied to the main cams in order to arrive at a specific draw length.

U.S. Pat. No. 7,721,721, directed to a “Reversible and Adjustable Module System for Archery Bow”, teaches the use of interchangeable modules that can be attached to the main cam body. The concept is to provide the dealer with a single bow and provide that bow to an archer with a total of eighteen selected values for draw weight and length.

All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.

Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.

A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.

BRIEF SUMMARY OF THE INVENTION

In some embodiments, an archery bow comprises a riser and opposed limbs, and each limb supports a rotatable member. At least one rotatable member comprises a body and a cam module. The body defines a bowstring payout track and the cam module defines a power cable take-up track. The cam module is adjustable with respect to the body between first and second orientations. The draw length of the bow in the first orientation is different from the draw length of the bow in said second orientation. A maximum draw force of the bow in the first orientation is substantially similar to a maximum draw force of said bow in said second orientation. In some embodiments, the bow has at least a 45% let-off draw force in both the first and second orientations. In some embodiments, the cam module is rotated at least 10 degrees with respect to the body between the first and second orientations. In various embodiments, the cam module is rotated at least 20, 30, 40 or 50 degrees with respect to the body between the first and second orientations.

In some embodiments, the cam module is a first cam module of a first size and the bow further comprises a second cam module that is shaped differently from the first cam module. The first cam module can be replaced with the second cam module. A maximum draw force of the bow using the second cam module is greater than a maximum draw force of the bow using the first cam module. In some embodiments, the second cam module is larger than the first cam module.

In some embodiments, the second cam module is adjustable with respect to the body between first and second orientations. A draw length of the bow using the second cam module in the first orientation is different from a draw length of the bow using the second cam module in the second orientation. A draw force of the bow using the second cam module in the first orientation being substantially similar to a draw force of the bow using the second cam module in the second orientation.

In some embodiments, an archery bow comprises a riser and opposed limbs, and each limb supports a rotatable member. At least one rotatable member comprises a body and a cam module. The body defines a bowstring payout track and the cam module defines a power cable take-up track. The cam module is adjustable with respect to the body between plurality of orientations including a maximum draw length orientation and a minimum draw length orientation. A draw length of the bow in the maximum draw length orientation is at least six inches greater than a draw length of the bow in the minimum draw length orientation. A draw force of the bow is substantially constant over at least 60% of the range of adjustability between the maximum draw length orientation and the minimum draw length orientation. The archery bow has at least 45% let-off in draw force both the maximum and minimum draw length orientations.

In some embodiments, a draw length of the bow in the maximum draw length orientation is at least eight inches greater than a draw length of the bow in the minimum draw length orientation.

In some embodiments, a draw force of the bow is substantially constant over at least 75% of the range of adjustability between the maximum draw length orientation and the minimum draw length orientation.

In some embodiments, a draw force of the bow is substantially constant over all of the range of adjustability between the maximum draw length orientation and the minimum draw length orientation.

In some embodiments, an archery bow comprises a riser and opposed limbs, and each limb supports a rotatable member. At least one rotatable member comprises a body and a cam module. The body defines a bowstring payout track and the cam module defines a power cable take-up track. The cam module is adjustable with respect to the body between first and second orientations

In some embodiments, an archery bow comprises a riser and opposed limbs, and each limb supports a rotatable member. At least one rotatable member comprises a body and a cam module. The body defines a bowstring payout track and the cam module defines a power cable take-up track. The cam module is rotatably adjustable with respect to the body between first and second orientations. The cam module is removable from the bow without precompressing the limbs or relaxing the tension on the limbs of the bow. In some embodiments, the cam module comprises a hook that engages a portion of the rotatable member body. In some embodiments, the hook comprises a semi-circular portion that abuts a semi-circular portion of the rotatable member body.

In some embodiments, an archery bow kit comprises a riser and opposed limbs. Each limb supports a rotatable member. At least one rotatable member comprises a body and a first cam module. The body defines a bowstring payout track and the first cam module defines a power cable take-up track. The kit includes a second cam module that is suitable for replacing the first cam module. Each of the cam modules comprise a let-off portion and a peak weight portion, the peak weight portion of the second cam module being larger than the peak weight portion of the first cam module. A peak draw force of the bow using the first cam module is less than a peak draw force of the bow using the second cam module, and the let-off portion of the first and the second cam modules each producing at least 45% let-off in draw force.

In some embodiments, a method comprises providing parts for an archery bow including at least one rotatable member body and a plurality of cam weight modules. Each cam weight module is attachable to the rotatable member in one of a plurality of orientations, wherein each orientation results in a different draw length. Each cam weight module results in a different draw force and provides at least a 45% let-off in draw force. The method further comprises selecting a cam weight module based upon a desired draw force and assembling the parts to form the archery bow, including attaching the selected cam weight module to the rotatable member body.

These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference can be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there are illustrated and described various embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the invention is hereafter described with specific reference being made to the drawings.

FIG. 1 shows a side view of an embodiment of an archery bow in a brace condition.

FIG. 2 shows an embodiment of a rotatable member.

FIGS. 3A-3D show embodiments of cam modules.

FIGS. 4A-4D show alternative embodiments of cam modules.

FIG. 5A shows a side view of an embodiment of an archery bow in a drawn condition.

FIG. 5B shows a detailed side view of the archery bow of FIG. 5A.

FIG. 6 shows draw force curves for an embodiment of a cam module at several different draw length orientations.

FIG. 7 shows draw force curves for an embodiment of a second cam module at several different draw length orientations.

FIG. 8 shows draw force curves for an embodiment of a third cam module at several different draw length orientations.

FIG. 9 shows draw force curves for an embodiment of a fourth cam module at several different draw length orientations.

FIG. 10 shows draw force curves for embodiments of four different cam modules, each module set at a first draw length orientation.

FIG. 11 shows draw force curves for embodiments of four different cam modules, each module set at a second draw length orientation.

FIG. 12 shows draw force curves for embodiments of four different cam modules, each module set at a third draw length orientation.

FIG. 13 shows draw force curves for embodiments of four different cam modules, each module set at a fourth draw length orientation.

FIG. 14 shows examples of two cam modules attached to a rotatable member, the cam modules oriented in a first draw length orientation.

FIG. 15 shows the cam modules of FIG. 14 in a second draw length orientation.

FIGS. 16A-16D show embodiments of cam modules.

FIG. 17 shows a graph that compares a moment arm of the force applied by the power cable with peak draw weight.

FIG. 18 compares embodiments of cam modules.

FIG. 19 shows a graph that compares bow axle displacement with peak draw weight.

FIGS. 20-24 each show embodiments of cam modules on a rotatable member at a given draw length orientation.

FIG. 25 shows a graph that compares a moment arm of the force applied by the power cable with draw length setting/orientation.

FIG. 26 shows a graph that compares a cam ratio with draw length setting/orientation.

FIG. 27 shows an embodiment of a crossbow.

FIG. 28 shows a detailed, exploded view of a rotatable member of the crossbow of FIG. 27.

FIG. 29 shows a detailed, exploded view of a rotatable member of the crossbow of FIG. 27.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.

For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated.

The archery bow concept described herein presents a new dimension in cam design that incorporates the use of a limited number of adjustable cam modules to provide a wide variety of compound bow offerings.

FIG. 1 shows an embodiment of a bow 10 that comprises a riser 12 that supports a first limb 14 and a second limb 16. Each limb 14, 16 is attached to the riser 12 with a fastener 15 (e.g., limb bolt), and may also be held by a limb cup 17. The first limb 14 supports a first rotatable member 20 and the second limb 16 supports a second rotatable member 22. In some embodiments, each limb 14, 16 supports an axle 24, which in turn supports the rotatable member 20, 22. In some embodiments, a central axis of the axle 24 comprises a rotation axis for the given rotatable member 20, 22.

The bow 10 illustrated in FIG. 1 is a dual cam bow, wherein each rotatable member 20, 22 comprises a cam 30. As shown, each cam 30 comprises a cam module that can be detached from the rotatable member 20, 22. In some embodiments, the two rotatable members 20, 22 are geometrically similar to one another.

A bowstring 18 extends between the rotatable members 20, 22. The bow 10 comprises two power cables 26a, 26b, wherein each power cable 26 extends from one limb 14, 16 to the cam 30 of the opposite rotatable member 20, 22. Each power cable 26 can be considered to have an anchor end 27, wherein the power cable 26 is anchored to the limb 14, 16, and a cam end 28, wherein the power cable 26 interacts with the cam 30. In some embodiments, the anchor end 27 of the power cable 26 terminates on the axle 24, for example comprising a split yoke straddling the axle 24.

FIG. 2 shows an embodiment of a rotatable member 20 in greater detail. The rotatable member 20 comprises a bowstring feed out track 42 extending about at least a portion of its periphery. A portion of the bowstring 18 is generally oriented in the bowstring feed out track 42 when the bow is in the brace condition, and bowstring 18 is fed out from the bowstring feed out track 42 as the bow 10 is drawn. The cam 30 comprises a power cable take up track 44 extending about at least a portion of its periphery. As the bow 10 is drawn, a portion of a power cable 26 is taken up by the power cable take up track 44.

In some embodiments, the rotatable member 20 comprises a capstan 21 and a terminal post 23. The power cable 26b wraps around the capstan 21 in a direction (e.g. clockwise) that is opposite from the direction of rotation of the rotatable member 20 during draw (e.g. counter-clockwise) as the power cable 26b is traversed along its cam end 28 around the capstan 21 toward the terminal post 23. This reverse wrapping concept is further described in U.S. patent application Ser. No. 12/895,610, titled “Archery Bow Cam”, filed Sep. 30, 2010, with inventor Mathew A. McPherson, the entire disclosure of which is hereby incorporated herein in its entirety.

An orientation of the cam 30 is adjustable with respect to the rotatable member 20, thereby changing the draw length of the bow 10. Desirably, the cam 30 can be attached to the rotatable member 20 in one of several rotational positions. In some embodiments, the rotatable member 20 comprises a plurality of apertures 32, and a fastener 34, for example in the form of a cap screw or machine screw, is used to secure a fastening location 31 of the cam 30 in alignment with a given aperture 32. Rotating the cam 30 with respect to the rotatable member 20 in the direction that the rotatable member 20 rotates during draw will shorten the draw length. Rotating the cam 30 with respect to the rotatable member 20 opposite the direction that the rotatable member 20 rotates during draw will increase the draw length. Thus, the rotatable member 20 can comprise an aperture 32a that represents the shortest draw length, and an aperture 32z that represents the longest draw length.

Desirably, a peak draw weight of the bow will remain substantially constant throughout the various draw length orientations of the cam 30 with respect to the rotatable member 20. This is true while all other aspects of the bow 10 remain the same. For example, the limbs 14, 16 are not changed, the limb fasteners 15 are not adjusted, etc.

The bow 10 disclosed herein allows for a greater amount of draw length adjustment at substantially the same draw weight than has been achieved in prior bows. For example, the various cam 30 orientations provided for in FIG. 2, specifically the apertures 32 ranging from 32a to 32z, will allow a draw length adjustability of approximately nine inches. FIG. 2 shows a first plurality 50 of apertures 32 aligned on an arc of constant radius from the center of rotation 25, wherein apertures 32a and 32z are positioned on opposite ends of the first plurality 50 of apertures 32. As shown, the first plurality 50 of apertures 32 includes a total of nine apertures 32, wherein the first aperture 32a provides for a shortest draw length, such as 22 inches, and the last aperture 32z provides for a longest draw length, such as 30 inches. Each intermediate aperture 32 provides for a 1 inch incremental change in the draw length.

In some embodiments, the rotatable member 20 further comprises a second plurality 52 of apertures 32 aligned on a second arc. Desirably, all apertures 32 in the second plurality 52 are aligned on an arc of constant radius from the center of rotation 25. Desirably, the apertures 32 in the second plurality 52 are rotationally staggered with respect to the apertures 32 in the first plurality 50. The cam 30 further comprises a second fastening location 33, wherein the second fastening location 33 can be aligned with apertures 32 in the second plurality 52. The fastener 34 can be removed from the first fastening location 31 and used in the second fastening location 33 with apertures 32 of the second plurality to achieve a greater degree of draw length adjustability. In some embodiments, the fastener 34 is threaded into the fastening location 33. As shown in FIG. 2, the second plurality 52 of apertures 32 includes a total of eight apertures 32, wherein each aperture 32 provides for a 1 inch incremental change in the draw length. The second plurality 52 of apertures 32 is staggered to provide for draw length adjustments that fall between the draw lengths achieved with the first plurality 50 of apertures 32. Thus, the two pluralities 50, 52 of apertures 32 allow for adjustment of the draw length from 22 inches to 30 inches in half-inch increments.

In at least some embodiments, the large draw length adjustability provided by the bow 10 disclosed herein, while maintaining substantially the same peak draw weight, stems from a cam 30 design wherein the bow 10 reaches peak draw weight as the power cable 26 is taken up at a predetermined peak weight location 46 of the power cable take up track 44, regardless of the particular draw length setting. Desirably, the draw force progressively increases from brace orientation until the draw orientation where peak weight is reached (i.e. when the power cable 26 is taken up at the peak weight location 46), after which the draw force will decrease. This is different from prior art rotatable draw length modules, which generally resulted in inherent significant adjustment of peak weight as an undesirable side effect of adjusting draw length.

From FIG. 2, it can be seen that if the cam 30 were adjusted to the shortest draw length (e.g. aperture 32a being used), the power cable 26 is taken up into the peak weight location 46 quickly upon draw. If the cam 30 were adjusted to the longest draw length (e.g. aperture 32z), the rotatable member 20 must rotate a greater amount before the power cable 26 is taken up into the peak weight location 46.

In some embodiments, the power cable 26 does not contact the cam 30 when the bow 10 is in the brace condition. In some embodiments, the power cable 26 does not contact the cam 30 when the bow 10 is in the brace condition, for any rotational orientation of the cam 30. In some embodiments, the power cable 26 does not contact the cam 30 when the bow 10 is in the brace condition for some of the rotational orientations of the cam 30, but does in other(s).

Although FIGS. 1 and 2 show an embodiment where the cam 30 comprises a fastening location 31 and the rotatable member 20 comprises a plurality of apertures 32, any suitable mechanism can be used to attach the cam 30 to the rotatable member 20 in a plurality of orientations. For example, in some embodiments (not illustrated), a rotatable member 20 can comprise a fastening location, and the cam 30 can comprise a plurality of apertures.

In some embodiments, a bow 10 can be provided with multiple cam 30 modules, wherein each module provides for a different peak draw weight. In some embodiments, each cam module 30 can be arranged in a plurality of orientations with respect to the rotatable member 20 to adjust draw length as described above.

FIGS. 3A-3D show several embodiments of cam 30 modules that can be used with the bow of FIG. 1. A first cam module 30a, as shown in FIG. 3A, will produce a first peak draw weight, such as 40 pounds. Shown in FIG. 3B, a second cam module 30b will produce a second peak draw weight, such as 50 pounds. Shown in FIG. 3C, a third cam module 30c will produce a third peak draw weight, such as 60 pounds. Finally, shown in FIG. 3D, a fourth cam module 30d will produce a fourth peak draw weight, such as 70 pounds. Desirably, each cam module 30 provides for a particular peak draw weight when used in the bow 10, while all other aspects of the bow 10 remain the same. For example, the limbs 14, 16 are not changed, the limb fasteners 15 are not adjusted, etc.

It should be noted that prior art bows are generally constructed having the limbs and riser as separate pieces, which allows the limbs to be changed, for example to adjust draw weight. When using the rotatable member 20 and cam 30 disclosed herein, in some embodiments, the riser 12 and limbs 14, 16 can comprise a single, unitary assembly of components. Further, in embodiments of the bow 10 disclosed herein that utilize separate limbs 14, 16 and limb fasteners 15, the fasteners 15 can also be adjusted to adjust (e.g. fine tune) the draw force of the bow 10.

Desirably, a peak draw weight of the bow 10 will remain substantially constant throughout the various draw length orientations of the cam 30 with respect to the rotatable member 20.

The terms “substantially constant” or “substantially similar” as used herein when referring to peak draw weights means that there is less than 5% variation in the peak draw weight, as described below. It should be noted that a greater range of draw length adjustability generally results in a greater variation in the actual peak draw weight of the bow.

“Let-off” as used herein refers to a reduction in the draw force of the bow that occurs after peak draw force as the bow is drawn. Let-off is generally accomplished via the bow's compounding action.

The “draw lengths” referred to herein are generally directed to “full” draw lengths of the bow.

In some embodiments, the peak draw weight of the bow does not change more than 5 pounds over at least 60% of the entire draw length adjustment range. In some embodiments, the peak draw weight of the bow does not change more than 4 pounds over at least 60% of the entire draw length adjustment range. In some embodiments, the peak draw weight of the bow does not change more than 5 pounds over at least 75% of the entire draw length adjustment range.

Each successively larger cam module 30 is sized relative to the previous, lower draw weight, cam module 30 to provide for a greater amount of power cable 26 take up during a given span of draw length, when compared to a smaller module. Thus, the power cable take up track 44 is longer in the larger cam modules 30. A greater amount of power cable 26 take up results in a greater amount of limb 14, 16 flex, and more force is required to draw the bow.

As further shown in FIGS. 3A-3D, each cam module 30 comprises a let-off portion 36 and a high weight portion 38. As the bow 10 is drawn from brace condition, the power cable 26 is first taken up in the high weight portion 38 of the cam module 30. As the bow 10 reaches full draw, the power cable 26 is taken up in the let-off portion 36 of the cam module 30. In order to achieve the desired draw force reduction/let-off at full draw, the power cable 26 must move closer to the center of rotation 25 of the rotatable member 20/cam module 30 at full draw (thus reducing the length of the moment arm of the force applied to the rotatable member 20 by the power cable 26, reducing the torque applied to the rotatable member 20 by the power cable 26 and also reducing the bowstring 18 draw force necessary to counteract that torque to retain full draw). Therefore, the power cable take up track 44 at the let-off portion 36 is oriented close to the center of rotation 25 in all cam modules 30a-30d. In some embodiments, a distance between the center of rotation 25 and the let-off portion 36 is the same for all cam modules 30a-30d.

In some embodiments, the let-off portion 36 can be considered to be the portion of the power cable take up track 44 that is closest to the center of rotation 25. In some embodiments, a maximum let-off portion is the portion of the power cable take up track 44 that is closest to the center of rotation 25.

A distance d between the power cable take up track 44 at the high weight portion 38 and the center of rotation 25 decreases with each successively smaller cam module 30. In some embodiments, the distance d of the third cam module 30c is approximately 84% of the distance d of the fourth cam module 30d. In some embodiments, the distance d of the second cam module 30b is approximately 80% of the distance d of the third cam module 30c. In some embodiments, the distance d of the first cam module 30a is approximately 76% of the distance d of the second cam module 30b.

In embodiments of the bow 10, wherein a given cam module 30 is rotatable with respect to the rotatable member 20 to adjust draw length, the distance d between the center of rotation 25 and the take up track 44 at the high weight portion 38 will be substantially constant across a predetermined arc length 40 (see e.g. cam module 30a in FIG. 3A). The arc length 40 required will depend on the range of adjustability of the cam module 30 with respect to the rotatable member 20. For example, one end of the arc length 40 represents a contact location for the power cable 26 as the bow 10 reaches peak draw weight in the shortest draw configuration, and the other end of the arc length represents a contact location for the power cable 26 as the bow reaches peak draw weight in the longest draw configuration. For embodiments of lower weight cam modules 30 and bows 10 that provide a lesser amount of draw length adjustability, the distance d is more likely to be constant across the arc length 40. For embodiments of bows 10 that provide for a greater amount of draw length adjustability, it is more likely that the distance d may be adjusted slightly across the predetermined arc length 40 (e.g. at one end of the arc length 40), especially in the largest cam module 30d, to achieve the desired draw force results.

FIGS. 4A-4D show alternative embodiments of cam modules 30as-30ds that further comprise a rotation stop 60 extension of the power cable take up track 44. The shape of the high weight portion 38 of each cam module 30as-30ds in FIGS. 4A-4D is similar to that of the corresponding cam module 30a-30d in FIGS. 3A-3D. Each rotation stop 60 comprises an extra portion of power cable take up track 44 that extends beyond the let-off portion 36 of the cam module 30 and is oriented to stop rotation when the power cable 26 enters the power cable take up track 44 in the rotation stop 60, for example as illustrated via the dashed line in FIG. 4D. In some embodiments, a rotation stop 60 comprises a straight extension of the power cable take up track 44 beyond the let-off portion 36.

FIGS. 5A and 5B show an embodiment of a bow 10 at a full draw orientation. The second rotatable member 22 comprises a third cam module 30c, for example as shown in FIG. 3C. The first rotatable member 20 comprises a third cam module 30cs that comprises a rotation stop 60, for example as shown in FIG. 4C. A power cable 26 is in contact with the rotation stop 60 such that further rotation/draw is prevented. The cam module 30c of the second rotatable member 22 does not have a portion that stops rotation—thus, only one mechanism to stop rotation is included on the bow 10. A bow 10 having a single rotation stop 60 mechanism is generally more comfortable to draw than a bow having dual rotation stops, as the dual stops tend to accentuate a slight difference in cam synchronization. A bow 10 having a rotation stop 60 as a portion of the cam 30 is more comfortable to draw than other types of rotation stop mechanisms (such as an extension of the rotatable member that hits a limb 14, 16 to abruptly stop rotation) because the stop 60 is relatively soft due to give in the power cable 26.

Thus, in some embodiments, a bow 10 comprises a first cam 30c and a second cam 30cs, wherein the power cable take up tracks 44 of the cams 30c, 30cs are largely similar to one another through substantially all of the draw length (thus being a dual or twin cam bow), but the second cam 30cs comprises a rotation stop 60 and the first cam 30c does not.

In some embodiments, a bow 10 can include cam modules 30 on both rotatable members 20, 22 that are identical. Thus, in some embodiments, both cam modules 30 can include a rotation stop 60, and in some embodiments, neither cam module 30 includes a rotation stop 60.

It should also be noted that cam modules 30 can be used that are similar with respect to their functional areas, but can be dissimilar with respect to any non-functional areas.

Turning to FIG. 18, this figure shows a comparison of embodiments of four cam modules 30a-30d, wherein each module 30 is suitable to produce substantially the same peak draw weight at a plurality of draw length orientations. A peak weight location 46 is shown for each cam module 30. Specifically, the peak weight location 46 indicated is the location that the given cam module 30 reaches peak draw weight when oriented on the rotatable member 20 in the maximum draw length orientation. It can be seen that the distance from a center of rotation 25 to the peak weight location 46 progressively increases as the modules increase in peak weight. Further, the distance at issue continues for a predetermined distance portion of the cam 30, resulting in a cable take up track 44 that comprises an arc γ having a substantially constant radius from the center of rotation 25. In FIG. 18, the arc γ is indicated for the largest cam module 30d.

In some embodiments, a cam module 30 comprises a groove 35 that comprises a first engagement location with the rotatable member body 20. A second engagement location comprises the fastening location 31 (FIG. 3A). In some embodiments, the groove 35 is asymmetrical. In some embodiments, the groove 35 comprises a hook arranged to engage the body of the rotatable member 20. In some embodiments, the groove 35 comprises an arcuate surface 37 arranged to engage the body of the rotatable member 20. In some embodiments, the arcuate surface 37 of the cam module 30, and a corresponding arcuate surface of the body of the rotatable member 20, are semicircular. In some embodiments, the arcuate surface 37 comprises a peak that is located opposite said fastening location 31 (FIG. 3A). Thus, in some embodiments, a cam module 30 is engaged to a rotatable member 20 body using only the arcuate surface 37 and a single fastening location 31/fastener 34. This can allow the cam module 30 to be changed quickly and easily, without disassembly of other portions of the bow 10.

FIG. 6 shows a plurality of draw force curves as related to draw length for an embodiment of a bow 10 using a first size cam module 30a. FIG. 6 indicates true draw length, whereas archery bows are often sold with an Archery Trade Association (ATA) draw length specification. ATA draw length is generally 1.75″ longer than true draw length. Therefore, a true draw length of 28.25″ on FIG. 6 would be sold as a bow having a 30″ ATA draw length.

In FIG. 6, the desired peak draw weight for the given cam module 30a is approximately 40 pounds. A draw force curve is provided for each of nine rotational orientations of the cam module 30 with respect to the rotatable member 20 (e.g. a curve is provided for each of the nine apertures 32a-32z included in the first plurality 50 of apertures 32 as shown in FIG. 2). As previously noted, a greater amount of draw length adjustability generally leads to greater variation in peak draw weight. For example, the six longest curves, which correspond to draw length adjustment ranging from 30″ to 25″, have a peak weight variation ranging from greater than 41 pounds to approximately 42.5 pounds—a variation of only 1.5 pounds.

It can also be noted that, in some embodiments, the shortest draw length orientations tend to result in a lower draw force. In some embodiments, adjustment of draw length near the longer draw length orientations results in very little actual draw weight change, whereas adjustment of draw length near the shorter draw length orientations results in a larger amount of actual draw weight change. In some embodiments, this is desirable because archers requiring a shorter draw length (e.g. children) may also prefer a slightly lower peak draw force.

As further illustrated in FIG. 6, at each length adjustment setting, the bow has a significant let-off. In some embodiments, the let-off is at least 25%; in some embodiments, the let-off is at least 40% and, in some embodiments, at least 45%, 50%, 55%. In some embodiments, the let-off is at least 60% and, in some embodiments, at least 65%.

FIG. 7 shows a plurality of draw force curves similar to FIG. 6, but for an embodiment of a bow 10 using a second size cam module 30b. In FIG. 7, the desired peak draw weight for the given cam module 30b is approximately 50 pounds.

As further illustrated in FIG. 7, at each length adjustment setting, the bow has a significant let-off. In some embodiments, the let-off is at least 25%; in some embodiments, the let-off is at least 40% and, in some embodiments, at least 45%, 50%, 55%. In some embodiments, the let-off is at least 60% and, in some embodiments, at least 65%.

FIG. 8 shows a plurality of draw force curves similar to FIG. 7, but for an embodiment of a bow 10 using a third size cam module 30c. In FIG. 8, the desired peak draw weight for the given cam module 30c is approximately 60 pounds.

As further illustrated in FIG. 8, at each length adjustment setting, the bow has a significant let-off. In some embodiments, the let-off is at least 25%; in some embodiments, the let-off is at least 40% and, in some embodiments, at least 45%, 50%, 55%. In some embodiments, the let-off is at least 60% and, in some embodiments, at least 65%.

FIG. 9 shows a plurality of draw force curves similar to FIG. 8, but for an embodiment of a bow 10 using a fourth size cam module 30d. In FIG. 9, the desired peak draw weight for the given cam module 30d is approximately 70 pounds. As previously noted, a greater amount of draw length adjustability generally leads to greater variation in peak draw weight. For example, the six longest curves, which correspond to draw length adjustment ranging from 30″ to 25″, have a peak weight variation ranging from approximately 72 pounds to approximately 74 pounds—a variation of only 2 pounds.

As further illustrated in FIG. 9, at each length adjustment setting, the bow has a significant let-off. In some embodiments, the let-off is at least 25%; in some embodiments, the let-off is at least 40% and, in some embodiments, at least 45%, 50%, 55%. In some embodiments, the let-off is at least 60% and, in some embodiments, at least 65%.

In some embodiments, for all modules at all length settings, the let-off is at least 40%, 45%, 50%, 55%, 60% and, in some embodiments, at least 65%.

FIG. 10 shows a plurality of draw force curves as related to draw length for multiple cam modules 30a-30d, each at a similar draw length setting, specifically a setting corresponding to a draw length of approximately 24 inches.

FIG. 11 shows a plurality of draw force curves for multiple cam modules 30a-30d, each at a similar draw length setting, specifically a setting corresponding to a draw length of approximately 26 inches.

FIG. 12 shows a plurality of draw force curves for multiple cam modules 30a-30d, each at a similar draw length setting, specifically a setting corresponding to a draw length of approximately 28 inches.

FIG. 13 shows a plurality of draw force curves for multiple cam modules 30a-30d, each at a similar draw length setting, specifically a setting corresponding to a draw length of approximately 30 inches.

The archery bow 10 system described herein combines the desirable attributes of rotatable cam modules 30 and interchangeable cam modules 30 in such a manner that a single bow 10 provided with a limited number of module sizes is able to fill the needs of the majority of the consumer market. Previously, a single bow could not be adjusted to be suitable for all the draw lengths and draw weights described herein merely by changing a cam module. For example, draw weights have traditionally been adjusted by providing a bow with different limbs. Often a unique cam design was required for each available strength of bow limb. Thus, in order to provide bows for a range of consumers, a bow supplier was required to stock several versions of cams and several versions of limbs for a given bow model. The bow 10 described herein provides for the same range of adjustability while requiring only one limb type, one rotatable member type, and a few cam modules 30. This concept can lower manufacturing costs, drastically reduce the inventory required of retailers and provide the consumer with a product that can be adjusted to meet changing needs.

Design Example

An example of a design procedure for developing the various cam modules 30 is discussed below.

It should be noted that early compound bows were shaped quite differently from current compound bows. Early compound bows were much longer (e.g. longer axle-to-axle length) and had smaller rotatable members. A portion of their draw length was provided by limb flex and a corresponding reduction in axle-to-axle length. Conversely, current bows achieve a greater amount of draw length by feeding greater amounts of bowstring out from larger rotatable members. This evolution in bow design allows the cam module concept disclosed herein to be easier to achieve, whereas such a system may not have been possible in older compound bow designs.

Referring again to FIGS. 1 and 2, in general, the bowstring feed out track 42 of a rotatable member 20 should be a size and length that enables a sufficient amount of bowstring to feed out, to achieve the desired maximum draw length for the bow 10. The power cable take up track 44 of a cam 30 is sized and shaped to take up an appropriate amount of power cable 26, causing an appropriate amount of limb 14, 16 flex to achieve the desired draw weight for that cam 30. Further, a cam ratio exists between the rotatable member 20 and the cam module 30, as discussed in greater detail below. The cam ratio controls the forces in the power cable 26 and bowstring 18 (specifically between points that are tangent to the power cable and tangent to the bowstring relative to the center of rotation 25) at any position of the draw cycle. This cam ratio determines the draw force profile and the effort that is required to draw the bow.

A basic concept of a compound bow is that at some point during draw, the amount of force that must be applied to the bowstring 18 to draw the bow increases to a maximum and subsequently decreases. Generally, the force required to draw the bowstring 18 beyond the position at which maximum draw force is achieved is either constant or is decreasing as the bowstring 18 is drawn to the full draw length. This concept can be seen in FIGS. 6-13 as the draw force curves reach a maximum and then let off.

Each specific set (e.g. pair) of cam modules 30 provides a given maximum draw weight. Simultaneously, each set of cam modules 30 can be adjusted to achieve a plurality of predetermined draw lengths. Due to the range of draw lengths, it is desirable that peak draw weight be achieved early in the draw cycle, allowing the desired peak weight to be achieved even for the shortest possible draw length.

For the main example bow described herein, the shortest desired draw length is approximately 24 inches, based on the Archery Trade Association (ATA) guidelines. A 24″ (ATA) draw length translates to a true draw length of approximately 22.25″. Using this draw length in a bow having a brace height of approximately 7″, the power stroke of the bow would be approximately 15.25″ (22.25″-7″). It is often pleasurable if a bow reaches peak draw weight at or before half way through the power stroke. Thus, a good starting design goal would be to reach peak weight around 7-8″ into the power stroke. This translates to a desire to reach peak weight at approximately 15″ (ATA) draw length. Thus, there is a design goal to reach peak draw weight at approximately 15″ (ATA) draw length for each specific cam module 30 set. In the main example bow 10 described herein, the modules are designed to achieve approximately 40 #, 50 #, 60 # and 70 #peak draw weights.

By way of example, using a rotatable member 20 as shown in FIG. 1 and one of the above cam modules 30 attached to the rotatable member 20 in the longest draw length orientation, the rotatable member 20 rotates approximately 50 degrees from brace position to its position when the bowstring reaches 15″ (ATA) draw length. Desirably, at this point the bowstring 18 reaches the aforementioned extreme and the bow 10 has achieved maximum draw weight. This in turn establishes a datum point baseline from which to design successively sized cam modules 30.

Because the same rotatable member 20 and bowstring feed out track 42 are used regardless of the specific cam module 30a, b, c, d, the relationship of bowstring draw length to rotational position of the rotatable member 20 is very nearly the same for any given draw length selection. Thus, at the desired 15″ True draw length, the moment arm of the rotatable member 20 is constant, and tension in the bowstring (i.e. draw force) is directly related to the moment arm of the module 30. Specifically, the moment arm associated with the power cable 26 is defined as the distance between the power cable 26 and a line extending from the center of rotation 25 parallel to the power cable 26, for example as shown in FIG. 14 and labeled ACm for module 30a and DCm for module 30d. Stated differently, the moment arm associated with the power cable 26 is the distance, measured perpendicular to the point of tangency, between the power cable 26 and a line extending from the center of rotation 25. This point of tangency can define one end of the arc length 40 described with respect to the first module 30a of FIG. 3A. If the cam module 30 radius (e.g. distance din FIGS. 3A-3D) is increased at this point of tangency, the load in the bowstring 18 must increase proportionately to keep the system in balance. This increase forms the basis for designing cam modules 30 that result in the desired peak draw weight for a given cam module 30.

In starting to build a set of cam modules 30, it is suggested to start with either the lowest draw weight or the highest draw weight desired, and position the selected cam module 30 in the maximum draw length configuration.

FIG. 14 shows a rotatable member 20 in a partially drawn orientation, wherein the bow 10 is drawn to the 15″ True draw length position described above, wherein peak draw weight is desired. FIG. 14 shows a first cam module 30a and a fourth cam module 30d, each oriented in a maximum draw length configuration. In the brace condition, the power cable 26 is tangent to point T₁ when the first cam module 30a is used. In the rotational position of FIG. 14, the power cable 26 is tangent to point P₁. Thus, from brace condition to the orientation of FIG. 14, the rotatable member 20 has rotated an amount shown by angle Φ.

With the rotatable member 20 in this position of FIG. 14, the force required to hold the bowstring has reached maximum draw weight. Tension in the bowstring 18 acts on the rotatable member 20 through moment arm Bm, which is perpendicular to bowstring 18. This force is counteracted by the force applied by the power cable 26 at point P₁, which is a torque amounting to the tension in the power cable 26 multiplied by the moment arm ACm.

Point P₁ is significant because during draw from brace condition until the rotational orientation of FIG. 14, wherein the power cable 26 reaches point P₁, the force necessary to draw the bowstring 18 is progressively increasing. Once the contact point between the power cable 26 and the cam module 30 passes point P₁, the draw force is either constant or is decreasing until the desired draw length is reached. The profile of the cam module 30a on either side of P₁ is dictated by these increasing and then decreasing draw force requirements.

FIG. 14 shows similar tangent points for an example of a largest cam module 30d. T₂ represents the power cable 26 tangent point at brace condition, and P₂ represents the power cable 26 tangent point at the rotational orientation of FIG. 14. Just as the moment arm ACm from the center of rotation 25 to the point P₁ on the first cam module 30a determines the peak draw weight for the first cam module 30a, the same is true for the fourth cam module 30d. The force applied to the rotatable member 20 by the power cable 26 at point P₂ is a torque amounting to the tension in the power cable 26 multiplied by the moment arm DCm. This force must be counteracted by the bowstring 18, for example by increasing tension/draw force in the bowstring because bowstring moment arm Bm is unchanged when modules 30 are swapped. The result is that the peak draw weight has been increased to the desired amount by the larger cam module 30d.

Additional cam module 30 moment arms can be considered to result in additional cam modules 30 that will result in any desirable peak draw force.

While the above explanation helps to determine the location of certain portions of the cam modules 30 (e.g. P₁, P₂) to achieve desired peak draw force, another design goal of at least some embodiments of a bow 10 is that each cam module 30 can be adjusted with respect to the rotatable member 20 to achieve a large number of draw lengths. In some embodiments, each cam module 30 is adjustable to achieve a draw length adjustment range of at least seven inches, while still maintaining a substantially constant peak draw weight.

FIG. 15 shows the rotatable member 20 in the same rotational orientation of FIG. 14, specifically the 15″ True draw orientation that achieves the maximum draw weight. The cam modules 30a, 30d have been repositioned to achieve a draw length that is 7″ shorter than that of FIG. 14. For example, the cam modules 30a, 30d are affixed to aperture 32x, which is the 7^th aperture in the first plurality 50 of apertures 32. FIG. 15 shows that each cam module 30 is designed such that the power cable moment arms ACm, DCm are of sufficient length, in this orientation, so the power cable 26 creates the same (or substantially similar) force as in FIG. 14, resulting in the bow reaching the maximum draw weight at this point in the draw cycle. For example, the first cam module 30a maintains a substantially constant moment arm ACm from point P₁ (peak draw weight in FIG. 14) to point R₁ (peak weight in FIG. 15). In this case, the moment arm ACm of the first cam module 30a remains substantially constant over an angular range of α, causing the maximum draw weight of the bow 10 to be substantially constant over the entire range of draw lengths between the draw length of FIG. 14 and the draw length of FIG. 15.

The situation is slightly different in the case of the fourth cam module 30d (e.g. the largest draw weight module). As the cam modules 30 get larger and the forces in the bow increase, the moment arm DCm of the relatively large cam modules 30 may require some adjustment at an end of the rotational adjustment range. Because the high weight portion 38 of the fourth cam module 30d is scaled up as compared to other modules, it takes up more power cable 26 during rotation. This causes greater limb flex and increased tension in the power cable 26. This increase in power cable 26 tension requires that the power cable moment arm DCm be reduced slightly to maintain peak draw weight at levels similar to other orientations of the fourth cam module 30d. The result is that the profile of the larger cam modules 30 are more likely to have a compound curvature over the angular span 3, which spans from P₂ to the tangent point R₂ of the power cable 26 in FIG. 15.

FIGS. 16A-16D show example design specifics for embodiments of cam modules 30a-30d, when oriented in the longest draw length setting with respect to the rotatable member 20. In such an orientation, the angular rotation Φ of each cam module 30, as the bow is drawn from brace condition, represented via T_c, to the point of maximum draw weight P_w is approximately 50 degrees, and the total cam rotation from brace to full draw is approximately 215 degrees.

In particular, the point of tangency P_w between the power cable 26 and the cam module 30 when maximum draw weight is attained during the draw cycle, is shown. Also shown is the radius R40, R50, R60, R70 from the center of rotation 25 to that tangent point P_w at maximum draw weight for each module. This radius R40, R50, R60, R70 increases as cam module 30 increases with bow weight. Further, the amount of power cable 26 that is taken up by the periphery of the module as the bow is drawn is represented by U. In particular, in some embodiments, for the maximum draw length configuration, U_d is approximately 3.5″ for the 70 #module U_c is approximately 3.0″ for the 60 #module; U_b is approximately 2.6″ for the 50 #module; and U a is approximately 2.2″ for the 40 #module.

FIG. 17 shows a graph plotting the radius R40, R50, R60, R70, in inches, from FIG. 16 against the peak draw weight of the given module 30. When a linear fit line is added to the plot, the relationship between the fit line and the plotted line yields a correlation coefficient of 0.9997. Therefore, the scaling from one draw weight module to another is a straight forward process relative to their radius at the point of tangency when maximum draw weight is attained in the draw cycle. In other words, if a bow having a max draw weight of 45 # is desired, for example, the radius can be determined according to the linear fit line, as depicted.

Another method to approximate scaling up or down of cam module 30 sizes is to compare the amount of power cable 26 take up that would be required on the next module 30 based on the amount of power cable 26 take up in the present module. FIG. 19 shows a near linear relationship between power cable 26 take up and peak draw weight. In FIG. 19, the specific values for power cable 26 take up are approximated as half of the axle-to-axle displacement, in inches, upon draw (e.g. the power cable take up results in axle-to-axle displacement).

FIGS. 20-24 show an embodiment of a rotatable member 20 with cam modules 30a-30d arranged at different draw lengths. In each instance, the bow is at its peak draw weight. The bowstring moment arm is indicated by Bm and power cable moment arms are indicated specifically in FIG. 20 by ACm, BCm, CCm, and DCm and, more generally in FIGS. 21-24 by PCm. Further, the tangent points are illustrated via Pwa, Pwb, Pwc, and Pwd for the respective cam modules 30a, 30b, 30c, and 30d.

FIG. 20 shows the 22″ ATA draw length at peak weight.

FIG. 21 shows the 24″ ATA draw length at peak weight.

FIG. 22 shows the 26″ ATA draw length at peak weight.

FIG. 23 shows the 28″ ATA draw length at peak weight.

FIG. 24 shows the 30″ ATA draw length at peak weight. Values from these Figures are shown in charts 1 and 2, below.

CHART 1
Power Cable Moment Arm (PCm) at Peak
Draw Weight (in inches)
	40#	50#	60#	70#
30″	0.656	0.828	1.011	1.187
28″	0.659	0.831	1.016	1.191
26″	0.66	0.823	0.995	1.137
24″	0.624	0.765	0.897	0.994
22″	0.569	0.657	0.751	0.805

CHART 2
Bowstring Moment Arm (Bm) at
Peak Draw Weight (in inches)
30″ 1.314
28″ 1.320
26″ 1.320
24″ 1.315
22″ 1.319

FIG. 25 shows a graph created using data from chart 1, mapping the draw length against the power cable moment arm PCm. FIG. 25 shows the relationship of the power cable moment arms across the multiple module 30 sizes. When one module size is known, this relationship can be used to calculate the basis for other module sizes.

A cam ratio between the bowstring moment arm Bm and the power cable moment arm PCm is shown in the chart below for each module 30a-30d at various draw length orientations. The cam ratio is calculated by dividing the bowstring moment arm, Bm, by the power cable moment arm, PCm.

CHART 3
Cam Ratio Calculation at constant bowstring
moment arm Bm
	40	50	60	70
30	2.008	1.591	1.303	1.110
28	1.998	1.585	1.296	1.106
26	1.995	1.600	1.324	1.158
24	2.111	1.722	1.468	1.325
22	2.315	2.005	1.754	1.636

FIG. 26 shows a graph of the data of chart 3.

In some embodiments (e.g. the bow of the design example described above), each of the three smaller modules 30a, 30b, 30c do not contact the power cable 26 when the bow 10 is in the brace condition, regardless of the draw length orientation of the module. The largest module 30d tends to have some contact with the power cable 26 due to its larger size/radius, wherein a portion of the power cable 26 is oriented in a portion of a groove that extends around the periphery of the module 30d (e.g. the power cable track). The contact is very slight, wherein the power cable 26 is not displaced from its orientation at brace due to the module—e.g. the power cable 26 is not loaded in a lateral direction by the module 30d when the bow is in the brace condition.

In some embodiments, the peak draw weight of the bow changes less than 5% of the desired peak draw weight over at least 75% of the entire draw length adjustment range. Stated differently, for the 40 #module with an adjustment range from 22″-30″ ATA draw length settings shown in FIG. 6, for example, the peak draw weight changes by 2 pounds or less (5% of 40 pounds) over at least the 24″-30″ ATA draw length settings.

In some embodiments, the peak draw weight of the bow changes less than 4% of the desired peak draw weight over at least 75% of the entire draw length adjustment range. With regard to FIG. 7, for example, for the illustrated 50 #module, the peak draw weight changes by 2 pounds or less (4% of 50 pounds) over at least the 24″-30″ ATA draw length settings.

Further relationships are shown for the 60 # and 70 #modules in FIG. 8 and FIG. 9. Additionally, it will be appreciated that, in some embodiments, the peak draw eight of the bow changes less than 3% of the desired draw weight over at least 60% of the entire draw length adjustment, for example where the draw length can be adjusted between 22″ and 30″ ATA. With reference to FIG. 9, for example, the peak draw weight changes by 2 pounds or less for the 25″-30″ ATA draw length settings.

Further, in some embodiments, for example where the module is designed to be adjustable between a more limited range of draw length settings, the peak draw weight of the bow changes less than 3% of the desired draw weight for the entire draw length adjustment range. Stated differently, in some embodiments, the modules are adjustable, for example, only between 25″ and 30″ ATA draw length settings. With reference to FIG. 9, then, the difference in maximum draw weight between the 25″ setting and 30″ setting is approximately 1.5 pounds. 1.5 pounds divided by the desired maximum draw weight of 70 pounds yields a variation of approximately 2.1%, which is less than 3%. Therefore, where the module is limited to adjustability between 25″ and 30″, the variation in peak draw weight is confined to a narrower range.

Moreover, in some embodiments, the peak draw weight of the bow changes less than 3% of the desired draw weight (e.g., 40 #, 50 #, 60 #, 70 #) for the entire adjustment range. For example, when fitted with 40 #, 50 #, 60 #, or 70 #modules, each being adjustable between 25″ and 30″ ATA ranges, the peak draw weight of the bow changes less than 3%.

Although the bulk of this disclosure is directed to dual cam bows, the module 30 concept described herein can be applied to any suitable type of bow, such as single cam bows, cam-and-a-half bows, CPS bows, twin cam bows, dual sync or binary cam bows, etc.

The bow 10 concept described herein can be combined with a power cable force vectoring anchor, for example as described in U.S. Pat. Nos. 7,946,281 and 8,020,544, the entire disclosures of which are hereby incorporated herein in their entireties.

The cam module 30 concept can also be applied to crossbows, allowing a crossbow owner to vary the draw weight of the crossbow at will by changing a module. This concept can allow a crossbow to be more of a versatile sporting device than strictly a hunting device. The consumer can adjust the draw weight to a value that is no greater than necessary for the specific shooting need. Thus, the crossbow can be adjusted to be more pleasurable for recreational target shooting, for example.

Turning to FIG. 27, an example of a suitable crossbow 110 is shown. The crossbow 110 comprises a bow portion 113 and a stock portion 115, which are securely attached to one another. The bow portion 113 comprises a first limb 114, a second limb 116, and at least one rotatable member 120. The rotatable member 120 comprises a cam module 130, an example of which is shown in greater detail in FIGS. 28 and 29.

The stock portion 115 comprises a trigger 148 and a latch 147, which is released by pulling the trigger 148, to fire a bolt or arrow (not shown). The bow portion 113 further comprises a prod 119. Further details of a crossbow structure can be found in U.S. Application No. 61/699,244, titled, “Self-Aligning Crossbow Interface,” with inventor Mathew A. McPherson, filed on Sep. 10, 2012, the contents of which are herein incorporated by reference.

With regard to FIGS. 28 and 29, a cam module 130 is shown therein. The cam module 130 is designed for a predetermined maximum draw weight. The cam module 130 can be swapped for a cam module which produces a greater or lesser maximum draw force, as discussed above with respect to bow 10 and cam 30. In this way, the crossbow 110 can be suited as desired by the user simply by swapping cam modules 130.

Further, it will be appreciated that the draw length of the crossbow 110 remains the same when one weight cam module is replaced with another, thus eliminating the added complexity of incorporating the adjustable draw length feature in the crossbow application.

Finally, in some embodiments, the cam module 130 is attached to the rotatable member 120 with one or more fasteners 134. In some embodiments, the fastener(s) 134 comprise screws that are threaded into the cam module 130.

The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this field of art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to.” Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.

Claims

1. An archery bow comprising:

a riser, a first limb supporting a first rotatable member and a second limb supporting a second rotatable member;

the first rotatable member comprising a body comprising a bowstring track and a first cam module attached to the body, the first cam module comprising a power cable track;

a bowstring extending from the first rotatable member to the second rotatable member;

a power cable arranged to contact the first cam module; and

a second cam module interchangeable with the first cam module;

wherein the first cam module and the second cam module each comprise a high weight portion and a let-off portion, the high weight portion of the first cam module shaped differently from the high weight portion of the second cam module, the let-off portion of the first cam module shaped similarly to the let-off portion of the second cam module.

2. The archery bow of claim 1, wherein a peak draw force provided by the high weight portion of the first cam module is different from a peak draw force provided by the high weight portion of the second cam module, and a reduction in draw force provided by the let-off portion of the first cam module is similar to a reduction in draw force provided by the let-off portion of the second cam module.

3. The archery bow of claim 1, the high weight portion of the first cam module comprising an arc having a first radius, the high weight portion of the second cam module comprising an arc having a second radius different from the first radius.

4. The archery bow of claim 1, the first cam module attachable to the body in a first orientation to provide a first draw length, the first cam module attachable to the body in a second orientation to provide a second draw length different from the first draw length.

5. The archery bow of claim 4, wherein the second orientation comprises a rotation of the first orientation.

6. The archery bow of claim 4, the second cam module attachable to the body in a first orientation to provide a first draw length, the second cam module attachable to the body in a second orientation to provide a second draw length different from the first draw length.

7. The archery bow of claim 1, the first cam module comprising a draw stop.

8. The archery bow of claim 7, the draw stop arranged to contact the power cable.

9. The archery bow of claim 1, further comprising a third cam module interchangeable with the first cam module, the third cam module comprising a high weight portion shaped differently from the high weight portion of the first cam module and shaped differently from the high weight portion of the second cam module, the third cam module comprising a let-off portion shaped similarly to the let-off portion of the first cam module.

10. The archery bow of claim 1, the power cable comprising a first power cable, the first cam module comprising an upper first cam module, the archery bow further comprising a second power cable, the second rotatable member comprising a lower first cam module arranged to contact the second power cable, the lower first cam module comprising a high weight portion shaped similarly to the high weight portion of the upper first cam module.

11. The archery bow of claim 10, the lower first cam module comprising a let-off portion shaped differently from the let-off portion of the upper first cam module.

12. An archery bow kit comprising:

a riser and opposed limbs, each limb supporting a rotatable member;

at least one rotatable member comprising a body and a first cam module, said body defining a bowstring payout track, said cam module defining a power cable take-up track;

said kit further comprising a second cam module suitable for replacing said first cam module, each of said cam modules comprising a let-off portion and a peak weight portion, the peak weight portion of said second cam module being larger than the peak weight portion of said first cam module;

wherein a peak draw weight of said bow using said first cam module is less than a peak draw weight of said bow using said second cam module and the let-off portions of said first and said second cam modules each produce at least 45% let-off in draw weight.

13. The bow kit of claim 12, wherein said first cam module is adjustable with respect to said rotatable member body between first and second orientations, a draw length of said bow with said first cam module in said first orientation is different from a draw length of said bow with said first cam module in said second orientation, a peak draw weight of said bow with said first cam module in said first orientation is substantially similar to a peak draw weight of said bow with said first cam module in said second orientation.

14. The bow kit of claim 13, wherein said draw length changes at least six inches between said first orientation and said second orientation.

15. The bow kit of claim 13, wherein said second cam module is adjustable with respect to said rotatable member body between first and second orientations, a draw length of said bow with said second cam module in said first orientation is different from a draw length of said bow with said second cam module in said second orientation, a peak draw weight of said bow with said second cam module in said first orientation is substantially similar to a peak draw weight of said bow with said second cam module in said second orientation.

16. The bow kit of claim 15, wherein said draw length changes at least six inches between said first orientation and said second orientation.