Aspects of the present invention deal with archery bows, and in particular deal with fittings that may be used with a cable arrangement on a bow.
Compound bows are archery bows that use a system of cables and cams to bend the limbs of the bow to generate potential energy that is transferred to an arrow or bolt. In addition to a bowstring, many compound bows include a system of power cables that extend between the cams and act to pull the limbs together as the cams are rotated. Aspects of the present disclosure address a different type of attachment method for the power cables.
In certain embodiments, a fitting is illustrated which can be used with a cable arrangement on a compound type of bow such as a crossbow or a vertical compound bow. The cable attachment fitting may include an inner arm and an outer arm. The inner arm is offset from the outer arm, forming a limb opening. The outer arm may include a cable anchor and a cable guide. A guide surface may extend from the cable anchor.
The cable arrangement may include cables with yokes that allow the cable to be mounted to a cam axle on both sides of a cam. A cable attachment fitting may be attached to the cam axle on each side of the cam to receive an end of the yoke. Each of the cable attachment fittings has a height and/or radial length that offsets [the cable]??? from the cam.
In some embodiments, the cable angles from the joint of the yoke toward a cable fitting, where the cable passes through a cable passage. The cable then runs along a guide surface and is secured to an anchor. In some embodiments, the cable is substantially parallel to the cam as it travels along the guide surface. The height offset due to the height of the cable attachment fitting and the radial offset due to the length of the guide surface help provide clearance between the cable and the radius of the cam during rotation of the cam and bending of the limbs.
Additional objects and advantages of the described embodiments are apparent from the discussions and drawings herein.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
Compound archery bows use a system of cables and rotatable pulleys or cams to bend the limbs of the bow and produce potential energy that is transferred to a fired arrow or bolt as kinetic energy. A let-off feature of the compound bow reduces the draw-force required to draw the bowstring as the bowstring progresses to being fully drawn. Cables extend between the cams and act to pull the limbs of the bow together as the cams are rotated when the bowstring is drawn. Both vertical bows, which typically have vertically oriented limbs, or crossbows, which typically have horizontally oriented limbs, may be compound archery bows and include a system of cables and pulleys.
Although a crossbow is shown as a representative example in
In compound bow arrangements, cross-cables or power cables sometimes have one end mounted to a cam axle. Often, a cable transitions to a y-shaped yoke at a cable joint so that the cable is anchored to the axle on both sides of the cam, balancing the cable to minimize torque loads on the cam. Certain embodiments shown in
In configuring a crossbow, the power cable arrangement needs to maintain sufficient clearance from the cams during the entire draw and release cycle. Simultaneously, as the bow is drawn and the limbs are bent, the power cable joints are each drawn toward the rail and stock, and particularly toward the slot or cable guide opening. Preferably, the power cable lengths including the spacing between the opening and the joints are configured so that the joints do not intersect or enter the opening, even at full draw. In an arrangement without cable fittings, to provide sufficient cam clearance, the yoke would form a narrower/deeper “V” profile between the opposing axle ends and the joint. In contrast, when cable fittings are used, the wider divergence angle forms a wider/shallower “V” profile. This enables the joints to be spaced closer to the cam and further from the stock opening than would be achievable without the fittings.
In certain alternate embodiments the clearance provided by the fittings allows a larger radius cam to be used while maintaining the joint in approximately the same place. A larger cam radius allows more cable track length for the bowstring and/or the power cable arrangement, which can be useful in providing a mechanical advantage.
Each fitting has a height or width which offsets the cable connection along the axle away from the cam along the axis of the axle. Correspondingly, an axle length may need to be used which extends a sufficient height or width beyond the limbs. The end of the cable is anchored to the fitting at the offset height. The fittings then each have a lateral or radial length, generally parallel to the plane of the cam, with a guide surface which supports an end length of the cable for a short distance. The guide surface holds that end length away from the cam, for example in a parallel spacing. The cable then angles toward the joint of the y-yoke from a divergence point at the distal end of the fitting, spaced from the axle by the lateral or radial length. The fitting may include a guide mounting, such as a passage, groove, or opening, to prevent the cable from falling off of the guide surface. The length of the guide surface is calculated to ensure sufficient clearance between the cable and the cam radius during use of the bow, including during rotation of the cam and bending of the limbs.
A side of the fitting proximal the axle may define an opening in a fork arrangement, for example between a pair of arms. The arms are pivotally mounted to the axle. A limb tip may be arranged on the axle within the opening, allowing the fitting to straddle that portion of the limb tip. The inner arm, closer to the cam, may extend laterally inward to clear the limb tip, and then toward the outer arm, forming a support portion which assists in bracing the outer arm against inward tension applied by the cable. The support portion may be slanted at an angle approaching perpendicular to the diverging cable portion of the yoke as it approaches the fitting.
A riser assembly 20 may extend from stock 12. A pair of archery bow limbs 25 is mounted to extend from opposing ends of the riser assembly. A rotatable element such as a cam 35 is positioned at the end or limb tip of each limb 25 and pivotally secured to a respective limb 25 by a cam axle 36 defining a pivot axis. In some embodiments, the rotatable element may be an eccentric cam, in which the center of rotation of cam 35 is different from the geometric center of cam 35. In alternate embodiments the rotatable element may be a pulley, wheel or cam with a central axle axis. In some embodiments, limbs 25 are made as split or “quad” limbs formed by two pairs of limb portions, namely limb portion 26 and a limb portion 28, one pair extending from each opposing end of the riser assembly. Alternately, each limb may be one piece with a slot defined at the limb tip to receive a rotatable element. A bowstring cable 40 extends from each rotatable element, for example it can be partially wrapped around each of the cams 35 and extends between limbs 25. The bowstring cable can be directly anchored to the cams and/or extends into a bowstring track on one or both cams. A power cable arrangement 45 also extends between limbs 25.
As shown in
Upper cable 51 and lower cable 52 each attach to a respective axle end via a respective cable attachment fitting 60. Upper cable 51 and lower cable 52 are non-linear as they extend from the joint to the axle. Upper cable 51 attaches to a cable attachment fitting 60 that is attached to cam axle 36 and located on one side of cam 35, and lower cable 52 attaches to a cable attachment fitting 60 that is attached to cam axle 36 on the opposite side of cam 35.
Upper cable 51 and lower cable 52 may be of equal length between a cable joint 47, 49 and opposing ends of axle 36. Alternately, upper cable 51 and lower cable 52 may be of different real or effective lengths, which can be configured to balance their respective applied loads on cam axle 36 to minimize the introduction of any cant or lean to the cam. For example as illustrated in
Cable attachment fitting 60, shown in more detail in
One end of outer arm 62 may include a cable anchor 64. The other end of outer arm 62 may include a cable guide 70, for example that defines a cable passage 71. A guide surface 63 may extend between cable anchor 64 and cable passage 71. As illustrated, the guide surface 63 is parallel to and spaced on an opposite side of the limb tip from cam 35. In some embodiments, guide surface 63 may include guide features for preventing a cable from falling off guide surface 63. For example, guide surface 63 may be textured to increase friction between a cable and guide surface 63, or guide surface 63 may include a track, groove or passage.
Outer arm 62 defines an outer axle opening 65. In some embodiments, outer axle opening 65 may extend through cable anchor 64. Inner arm 66 defines an inner axle opening 67 that is aligned with outer axle opening 65 to allow a cam axle 36 to pass through fitting 60.
In use on a crossbow, as shown in
The limb tip of limb portion 26 is positioned in limb opening 61 of upper fitting 160. Correspondingly, the limb tip of limb portion 28 is positioned in limb opening 61 of lower fitting 260. Cam axle 36 extends through the outer axle opening 65 of upper fitting 160, limb portion 26, and the inner axle opening 67 of upper fitting 160. Cam axle 36 then extends through an axle opening defined by cam 35, and into inner axle opening 67 of lower fitting 260, limb portion 28, and outer axle opening 65 of lower fitting 260. Axle clips, washers, bearings, and/or spacers may be placed along the axle as desired.
Yoke 50 includes where cable 46 transitions at cable joint 47 to upper cable 51 and lower cable 52. Upper cable 51 follows a non-linear path. An initial portion of upper cable 51 is angled upward from joint 47 toward upper fitting 160 and may engage cable guide 70. Upper cable 51 bends when it contacts the cable guide and continues with a horizontal portion that extends along outer arm 62 across guide surface 63 to cable anchor 64 where upper cable 51 is secured to upper fitting 160. For example, cable 51 may terminate in a loop which encircles cable anchor 64. In some embodiments, as the upper cable 51 extends along outer arm 62, the horizontal portion of upper cable 51 is substantially parallel to cam 35. In certain alternate embodiments, upper cable 51 and lower cable 52 can terminate adjacent the distal end of guide surface 63, for example being anchored to cable guide 70. Force applied to cable guide 70 is then carried through the cable guide structure to the axle.
Lower cable 52 extends downward toward lower fitting 260 and may engage cable guide 70. Similarly, lower cable 52 follows a non-linear path. An initial portion of lower cable 52 is angled downward from joint 47 toward lower fitting 260 and may engage cable guide 70. Lower cable 52 bends when it contacts the cable guide and continues in a horizontal portion that extends along outer arm 62 across guide surface 63 to cable anchor 64 where lower cable 52 is secured to lower fitting 260. For example, cable 52 may terminate in a loop which encircles cable anchor 64. In some embodiments, as lower cable 52 extends along outer arm 62, the horizontal portion of lower cable 52 is substantially parallel to cam 35. A symmetric setup to what is shown in
In certain alternate embodiments, upper cable 51 and lower cable 52 can terminate adjacent the distal end of guide surface 63, for example being anchored to cable guide 70. Force applied to cable guide 70 is then carried through the fitting to the axle.
As shown in
When the fittings are not used, to maintain sufficient clearance between the yoke and the cam, upper cable 51′ and lower cable 52′ must be arranged with longer lengths that diverge/converge at a relatively narrow joint angle α, forming a narrow “V” profile in the yoke. In comparison, when cable attachment fittings 60 are used, upper cable 51 and lower cable 52 can have lengths which diverge/converge at a wider joint angle θ, forming a wider “V” profile. In certain embodiments, with the wider angle arrangement the axes of cables 51 and 52 do not intersect the pivot axis of axle 36 within the length of axle 36. The extra clearance provided by fittings 60 allows joint 47 to be placed closer to cam 35 while maintaining sufficient cam clearance. In turn, cable 46 can have a longer length extending between opening 18 and joint 47. This enables a longer distance where cable 46 can translate during the draw and release cycle without joint 47 entering opening 18.
As representative embodiments for purposes of illustration, the height separation S of the axle ends and respective guide surfaces 63 can be approximately 2.4 inches. In the arrangement of
When the fittings are not used, to maintain sufficient clearance between the yoke and the cam, upper cable 51″ and lower cable 52″ diverge/converge at a relatively narrow joint angle α, forming a narrower “V” profile in the yoke. In comparison, when cable attachment fittings 60 are used, upper cable 51 and lower cable 52 extending from the same joint position diverge/converge at a wider joint angle δ, forming a wider “V” profile. As illustrative embodiments, in certain embodiments the height separation S of the axle ends and respective guide surfaces 63 can be approximately 2.4 inches, and joint 47 can be located at distance Y3 approximately 5.9 inches inward horizontally from the axle in a crossbow with an axle-to-axle width W of 17 or 18 inches. In the arrangement of
In certain embodiments, the joint angle of the “V” profile when a pair of cable fittings are used is approximately equal to or greater than 30 degrees. In further embodiments the joint angle is approximately equal to or greater than 35 degrees.
As shown in
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.
The present application claims the benefit of provisional application Ser. No. 62/236,261 filed on Oct. 2, 2015, which is incorporated herein by reference.
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Number | Date | Country | |
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20170097206 A1 | Apr 2017 | US |
Number | Date | Country | |
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62236261 | Oct 2015 | US |