Abstract:
A compound archery bow comprising a body having first and second flexible ends. A bowstring has at least a portion of itself trained about a rotational assembly and is anchored to a cam assembly. In addition, an anchor cable has a first cable end fixed to the first end of the bow and a second cable end secured to the cam assembly. The cam assembly has a bowstring anchor projection and an anchor cable anchor projection for anchoring the bowstring and the anchor cable, respectively and an anchor cable track for taking in the anchor cable as the bow is being drawn. The cam assembly also has a bowstring track for letting out bowstring cable as the bow is being drawn and a mechanical linkage permitting limited relative motion between the bowstring cable track and the anchor cable track.

Description:
BACKGROUND  
         [0001]    In a traditional archery bow, an archer must pull back with increasing force as he pulls the bowstring further back. Consequently, a great deal of strength may be needed to shoot an arrow with the full force of such a bow. This problem has been addressed with the advent of the compound bow, which employs at least one cam to create a draw force characteristic that actually decreases as the bowstring is pulled back past a certain point. The first compound bow had a cam at both the top and bottom of the bow to evenly leverage the draw force against the bow limbs. Unfortunately, with this arrangement it was difficult to keep the movement of the two cams synchronized as the bowstring was pulled back over repeated uses. To correct for this problem, a bow has been devised in which a single cam having a number of eccentric tracks is mounted at one end of the bow. Both ends of the bowstring cable are anchored to this cam and a grooved wheel is provided at the other end of the bow, around which the bowstring cable is looped. In this manner, there is no way for the bowstring cable feed out to be desynchronized as both ends of the cable are fed out by tracks that are rigidly fixed in place relative to one another on the single cam.  
           [0002]    Unfortunately when an arrow is shot a compound bow, whether of the one cam or two-cam variety, loses a portion of the energy stored in the bow limbs to kinetic energy of the rotational members, which are accelerated rapidly to a swift rotation. This kinetic energy, in turn, causes the bow to ring at the end of the arrow shoot.  
         SUMMARY  
         [0003]    In a first separate aspect the present invention is a compound archery bow comprising a body having first and second flexible ends. A rotational assembly and a cam assembly are rotatably mounted on the body and spaced apart from each other. A bowstring has at least a portion of itself trained about the rotational assembly and is anchored to the cam assembly. In addition, an anchor cable has a first cable end fixed to the first end of the bow and a second cable end secured to the cam assembly. The cam assembly has a bowstring anchor projection and an anchor cable anchor projection for anchoring the bowstring and the anchor cable, respectively and an anchor cable track for taking in the anchor cable as the bow is being drawn. The cam assembly also has a bowstring track for letting out bowstring cable as the bow is being drawn and a mechanical linkage permitting limited relative motion between the bowstring cable track and the anchor cable track.  
           [0004]    In a second separate aspect, the present invention is an archery bow cam assembly, including tracks for receiving cables, which may be placed into a first state wherein the tracks are in a first arrangement relative to one another or a second state wherein the tracks are in a second arrangement relative to one another. Mechanical energy is stored as the cam assembly is placed in the second state from the first state and is released as the cam assembly changes into the first state from the second state.  
           [0005]    The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1A is a side view of an archery bow, in rest position, according to the present invention.  
         [0007]    [0007]FIG. 1B is a side view of an archery bow, in drawn position, according to the present invention.  
         [0008]    [0008]FIG. 2 is a perspective view of a cam assembly similar to that of the archery bow of FIG. 1, except for that it is in mirror image form laterally.  
         [0009]    [0009]FIG. 3A is a front view of the cam assembly of FIG. 2.  
         [0010]    [0010]FIG. 3B is a front view of a variant of the cam assembly of FIG. 2.  
         [0011]    [0011]FIG. 3C is a front view of an additional variant of the cam assembly of FIG. 2.  
         [0012]    [0012]FIG. 3D is a front view of a further variant of the cam assembly of FIG. 2.  
         [0013]    [0013]FIG. 4 is a perspective view of the cam assembly of FIG. 2, rotated 180° from the view of FIG. 2.  
         [0014]    [0014]FIG. 5 is an exploded view of the cam assembly of FIG. 2.  
         [0015]    [0015]FIG. 6 is an exploded view of the cam assembly of FIG. 2, rotated 180° from the view of FIG. 5  
         [0016]    [0016]FIG. 7 is an exploded view of the cam assembly of FIG. 2, reoriented with respect to the exploded views of FIGS. 5 and 6.  
         [0017]    [0017]FIG. 8 is a perspective view of an alternative embodiment of a cam assembly according to the present invention.  
         [0018]    [0018]FIG. 9 is a front view of the cam assembly of FIG. 8.  
         [0019]    [0019]FIG. 10 is a perspective view of the cam assembly of FIG. 8, rotated 180° from the view of FIG. 8.  
         [0020]    [0020]FIG. 11 is a perspective view of an additional alternative embodiment of a cam assembly according to the present invention.  
         [0021]    [0021]FIG. 12 is a perspective view of the cam assembly of FIG. 10, rotated 180° from the view of FIG. 10.  
         [0022]    [0022]FIG. 13 is a rotated and exploded perspective view of the cam assembly of FIG. 11.  
         [0023]    [0023]FIG. 14 is a rotated and exploded perspective view of the cam assembly of FIG. 11, rotated 180° from the view of FIG. 13.  
         [0024]    [0024]FIG. 15 is a rotated and exploded perspective view of the cam assembly of FIG. 11, rotated 180° from the view of FIG. 14.  
         [0025]    [0025]FIG. 16 is an exploded side view of the cam assembly of FIG. 11.  
         [0026]    [0026]FIG. 17 is a side view of the cam assembly of FIG. 11.  
         [0027]    [0027]FIG. 18 is an exploded side view of an additional alternative embodiment of a cam assembly according to the present invention.  
         [0028]    [0028]FIG. 19 is an exploded perspective view of the cam assembly of FIG. 18.  
         [0029]    [0029]FIG. 20A is an alternative preferred embodiment of an archery bow according to the present invention and having a matching cam assembly on either limb.  
         [0030]    [0030]FIG. 20B is a side view of the archery bow of FIG. 2A, in drawn position.  
         [0031]    [0031]FIG. 21A is a side view of an alternative preferred embodiment of an archery bow according to the present invention, and having a matching wheel assembly on either limb.  
         [0032]    [0032]FIG. 21B is a side view of the archery bow of FIG. 21A, in drawn position.  
         [0033]    [0033]FIG. 22 is a front view of the cam assembly used in the archery bow of FIG. 20.  
         [0034]    [0034]FIG. 23 a  is a side view of an additional alternative embodiment of an archery bow according to the present invention.  
         [0035]    [0035]FIG. 23 b  shows the same view of the same bow as FIG. 23 a , but with the bowstring drawn.  
         [0036]    [0036]FIG. 24 is a front view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0037]    [0037]FIG. 25 is a front view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0038]    [0038]FIG. 26 is a front view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0039]    [0039]FIG. 27 is a side view of the cam assembly of FIG. 26.  
         [0040]    [0040]FIG. 28 is a side view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0041]    [0041]FIG. 29 is a front view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0042]    [0042]FIG. 30 is a front view of a further additional alternative embodiment of a cam assembly according to the present invention.  
         [0043]    [0043]FIG. 31 is an exploded side view of the cam assembly of FIG. 30.  
         [0044]    [0044]FIG. 32 is an exploded side view of an additional alternative cam assembly.  
         [0045]    [0045]FIG. 33 is an exploded perspective view of the cam assembly of FIG. 32.  
         [0046]    [0046]FIG. 34 is an exploded perspective view of the cam assembly of FIG. 32, rotated from the view of FIG. 33.  
         [0047]    [0047]FIG. 35 is a side view of the cam assembly of FIG. 32. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0048]    In gross form as shown in FIGS. 1A and 1B, an archery bow  10  according to a first preferred embodiment of the present invention is similar to some prior art archery bows. A top resilient limb  12  and a bottom resilient limb  14  are operatively joined together by way of a handle or riser  16 . The resilient limbs  12  and  14  are split at their distal ends into a top mounting fork  18  and a bottom mounting fork  20  respectively, supporting a top axle  22  and a bottom axle  24  respectively. A pulley  26 , having a single rim track, is rotatably mounted on top axle  22 . A cam assembly  40  having a primary cam  42  and a secondary cam  44  (FIGS.  2 - 7 , in lateral mirror image form, for a right-handed bow as opposed to the left-handed bow of FIG. 1), both of is eccentrically mounted on bottom axle  24 .  
         [0049]    A bowstring cable  50  is anchored to the primary cam  42 , looped about the pulley  26  and then also anchored to the secondary cam  44 . The section of bowstring cable  50  from the primary cam  42  to the pulley  26  is designated as a bowstring  52  and the section from the pulley  26  to the secondary cam  44  is designated as a return cable section  54 . In addition, an anchor cable  56  is anchored by a split yolk to the two ends of top axle  22  and is anchored at bottom to the secondary cam  44 . As an archer draws the bowstring  52 , the primary cam  42  and the secondary cam  44  both let out bowstring cable  50 . In turn, however, anchor cable  56  is taken up by primary cam  42  and helps to pull limbs  12  and  14  towards each other.  
         [0050]    Referring now to FIGS.  2 - 7 , for a more detailed description of a preferred embodiment of a cam assembly  40 , cams  42  and  44  are mounted to bottom axle by way of mounting holes  58  and  59  respectively. Bowstring  52  meets cam  42  at a bowstring receiving projection  60  and is threaded onto a bowstring track  43 . The bowstring track  43  wraps around primary cam  42  and the bowstring  52  is finally anchored at a bowstring pin or projection  62 . Return cable section  54  is taken up by the secondary cam  44  at a return projection  64 , winds about the secondary cam  44  on a return section track  47  and is anchored at a return section pin or projection  66 . Finally, anchor cable  56  is threaded through an anchor cable track  67  defined by a module structure  68  of secondary cam  44  and is anchored at an anchor cable pin  70 .  
         [0051]    A limited amount of movement is permitted between primary cam  42  and secondary cam  44  by means of a limiter pin  80  (FIG. 4), which projects outwardly from secondary cam  44  and fits into a limiter slot  82  of primary cam  42 . A mechanical energy storage device  84 , such as a spring, is compressed as the bowstring is pulled; thereby storing energy that is released after the bowstring is released. This avoids some of the friction losses encountered in other compound bows in the far portion of the draw. Consequently, there is a more consistent push to the arrow, after the bowstring is released and a resultant increase in for the arrow velocity.  
         [0052]    FIGS.  3 A- 3 D show a number of variants for mechanical energy storage device  84 . FIG. 3A shows a coil spring  84 , FIG. 3B shows an elastomer spring  84 ′, FIG. 3C shows an air or gas cylinder spring  84 ″ and FIG. 3D shows a torsional elastomer inserted between cams  42  and  44 .  
         [0053]    In one preferred embodiment, a polymer spacer  86  is fitted through a spacer aperture  88  of primary cam  42 , protruding slightly on the side of cam  42  that faces cam  44 , thereby separating cams  42  and  44  and providing a low friction surface to facilitate their relative motion.  
         [0054]    In an additional preferred embodiment, shown in FIGS.  8 - 10 , the tension on spring  84  is adjustable by way of a first setscrew  90 . In addition the range of travel possible between cams  42  and  44  is adjustable by way of a second setscrew  92 .  
         [0055]    It should be noted that although spring  84  is shown as a coil spring, any form of mechanical energy storage device that would fit in the prescribed volume could be used.  
         [0056]    Referring to FIGS. 11 through 17 in a second preferred embodiment of a cam assembly  140  (like elements with the first embodiment are given the same element number plus  100 ) an island boss  113  projects laterally outwardly from primary cam  142  and is free to move relative to the secondary cam  144 . This arrangement avoids the problem of friction between the secondary cam  144  and the anchor cable  56  when the bow is drawn.  
         [0057]    In addition, an axle bushing  115  is provided to facilitate movement of cam assembly  140  about the bottom axle  24 . Moreover, primary cam  142  is mounted at a round opening  158  about an axle boss  117  of the secondary cam  144 . Axle boss  117  defines a through-hole  159  to permit mounting about axle  24 . A circular separator  121  provides a low friction surface to facilitate relative movement between cams  142  and  144 .  
         [0058]    Referring to FIGS.  17 - 19 , in a third preferred embodiment, the anchor cable pin  270  has been moved from the primary cam onto the secondary cam  244 . With this embodiment, there is no friction between secondary cam  244  and anchor cable  56  when the secondary cam  244  moves relative to the primary cam  242 , as there is in the first preferred embodiment. Moreover, in the second preferred embodiment there is some potential for friction between the island boss  113  and the secondary cam  144 . As the island boss  113  is eliminated in the third preferred embodiment, there is no potential for this type of friction either.  
         [0059]    Referring to FIGS. 20A, 20B and  21 , a fourth preferred embodiment includes an identical cam assembly  340  on either split limb of an archery bow  310 . In this instance, the primary cam  342  feeds out the bowstring  352  as the archery bow  310  is being drawn and while the secondary cam  344  pulls in the anchor cable  356 . There is no return cable section, such as return cable section  54  of the first embodiment. Again, however, there is a limited freedom of movement between cams  340  and  342  and a mechanical energy storage device  384  which stores energy diverting the draw and releases energy on the shoot.  
         [0060]    Referring to FIGS. 22A and 22B, a fifth preferred embodiment of an archery bow  410  is quite similar to bow  310  but includes round wheel assembly  440  mounted on either end of the bow, instead of cam assemblies  340 . Similar to the previous embodiment, a primary wheel  442  and a secondary wheel  444  are allowed limited rotational freedom of movement relative to each other. This freedom of movement is resisted as the bow is being drawn by a spring  484 , which releases the energy stored on the shoot.  
         [0061]    Referring to FIGS. 23 a  and  23   b , a sixth preferred embodiment of an archery bow  510  includes a first cam assembly  540  mounted to the bottom mounting fork  520  and a second cam assembly  540 ′ mounted on a mounting fork  523  attached to the riser  516 . A bowstring cable  550  is anchored at first cam assembly  540  in the same manner as with cam assembly  40  in the first preferred embodiment, extends about primary cam  542  and upwards to the pulley  526  (this portion is designated as the bowstring  552 ), which it is trained about. Cable  550  then extends downwardly in a return cable portion  554 , which is anchored in like manner to second cam assembly  540 ′. In addition, a first anchor cable  556  extends from a top mounting fork  518  to anchor pin  570 ′ on second cam assembly  540 ′. In addition a second anchor cable  556 ′ extends from pin  570 ″ to pin  570  on first cam assembly  540 . A first spring  584  stores energy between first primary cam  542  and second secondary cam  544  and a second spring  584 ′ stores energy between second primary cam  542 ′ and second secondary cam  544 ′.  
         [0062]    Referring to FIG. 23 b , when archery bow  510  is drawn, cam assembly  540  rotates in a clockwise direction and cam assembly  540 ′ rotates in a counterclockwise direction. Accordingly bowstring cable  550  is let out by both cam assembly  540  and cam assembly  540 ′ and first anchor cable  556  is reeled in by cam assembly  540 ′. The second anchor cable  556 ′ is reeled in by both cam assembly  540  and cam assembly  540 ′.  
         [0063]    FIGS.  24 - 28  detail various different mechanical storage type and placement variants. It must be emphasized that the full range of mechanical storage types fit within the scope of the invention. This includes, but is not limited to, coil springs, torsional springs, neoprene springs and gas cylinders. FIG. 24 shows a cam assembly  640  having a spring system including a central spring  684  and a pair of outrigger springs  685  designed to dampen the vibrations by the release of central spring  684 . FIG. 25 shows a cam assembly  740  having a spring system made up of a primary spring  784  designed principally for energy storage and a secondary spring  785  designed principally to dampen the vibrations caused by the rapid release of primary spring  784 . FIG. 26 and  27  show a cam assembly  840 , that is similar to cam assembly  140 , but mounting a pair of coiled torsional springs  884  that are also mounted at either tyne of bottom mounting fork  20 . In this variant energy is stored in the rotation of cams  742  and  744 . In a slight variant shown in FIG. 28, coiled torsional springs  884  are replaced by elastomeric torsional springs  887 .  
         [0064]    [0064]FIG. 29 shows an embodiment in which a primary cam  942 , a secondary cam  944  and a module  968  (defining an anchor cable track  967 ) are all permitted a limited freedom of movement relative to one another. This is a departure from the first embodiment in which the secondary cam  44  included the module  68  as a fixed element. A first spring  984  stores energy as the secondary cam  944  is moved relative to the module  968  during the bowstring draw and a second spring  987  stores energy as the primary cam  942  is moved relative to the module  968 , also during the bowstring draw.  
         [0065]    Referring to FIGS.  30 - 31 , in a further alternative preferred embodiment of an archery bow cam  1012 , a dead blow assembly  1077 , including a dead blow element  1079  and two damping elements  1081 , is fitted within a coil spring  1084  to dampen cam vibrations at the end of an archery bow shoot.  
         [0066]    Referring to FIGS. 32 through 35, an additional alternative preferred cam assembly  1140 , quite similar to the second embodiment, which is shown in FIGS.  17 - 19 , includes a retainer element  1111 , to prevent the separation of primary cam  1142  from secondary cam  1144 . A retainer bolt  1113  connects with a protruding cam annulus  1115  on secondary cam  1144 , to rigidly connect the retainer element  1111  to the secondary cam  1144 . The retainer element includes an inner, protruding annulus  1117 , which makes contact with the protruding cam annulus  1115 , so that when cam assembly is not installed into an archery bow, the retainer element  1111  does not make contact with the outer face of primary cam  1142 , but is separated from this face by 125 microns (5 mils). When the cam  1140  is installed in a bow, however, the pressure of the bowstring on primary cam  1142  has a tendency to bend or rotate primary cam  1142  outwardly away from secondary cam  1144 . Under these conditions contact is made between retainer element and the outer face of cam  1142 . So that the relative motion of cams  1142  and  1144  is not impeded, retainer element is made of a low friction material such as brass or bronze, or even a Teflon coated or low friction composite material. In one preferred embodiment  660  bronze is used.  
         [0067]    Another feature of the embodiment of FIGS.  32 - 35  are thrust washers  1121  and  1127 , which work in cooperation with bushings  1123  and  1125 . This feature will be discussed with reference to elements  1121  and  1123 , with the understanding that elements  1125  and  1127  function in exactly the same manner. Thrust washer  1121  is wide enough so that neither bushing  1123  nor cam  1144  touches the bottom mounting fork (not shown but similar to bottom mounting fork  20  of bow  10 ). As a result, bushing  1123  is permitted to rotate in an almost frictionless state inside thrust washer  1125 . Ideally, thrust washer  1121  is made of a low-friction material, such as a low friction polymer or ceramic.  
         [0068]    There is a definite rational for including a mechanical storage device in an archer bow cam assembly. As noted in the background of the invention section, as an arrow is shot a portion of the potential energy stored within the bow limbs is converted into kinetic energy of the rotational members on the bow limbs, which are quickly accelerated to a considerable rotational velocity. After the arrow leaves the bow, this kinetic energy tends to make the bow ring with vibrations. By placing a mechanical energy storage device in a cam assembly (or assemblies) some potential energy is stored in the cam assembly itself. Rather than being converted to kinetic energy in the spinning rotational members (any cam assembly or wheel), this energy is more readily imparted to the bowstring at the end of the shoot, giving a final push to the arrow. As a result, the arrow leaves the bow with a greater velocity and more force, which is highly desirable for archers using compound bows.  
         [0069]    The terms and expressions which have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.