Abstract:
A cam is eccentrically journaled at one end of a compound archery bow and a pulley is journaled at the other end of the bow. A cable passes around the pulley to form a bowstring section and a second cable section, both sections forming a dual feed single cam compound bow. The amount of feed out to both ends of the bowstring is approximately the same. One embodiment of the cam provides a large radius cam groove and a smaller radius cam groove which are designed to synchronize the rate of cable feed out at both ends of the bowstring section during the drawing operation. An anchor cable is provided to tie the two limbs of the bow together during the flexing of the bow.

Description:
[0001]    This application claims the benefit of and is a continuation of application Ser. No. 10/934,630, filed Sep. 3, 2004, which is a reissue of application Ser. No. 09/160,983, filed Sep. 25, 1998, now U.S. Pat. No. 6,443,139, which is a continuation of application Ser. No. 08/047,481, filed Apr. 19, 1993, now U.S. Pat. No. 5,890,480, which is a continuation-in-part of application Ser. No. 07/875,748, filed Apr. 28, 1992, now U.S. Pat. No. 5,368,006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    In the past, most compound archery bows have used two cams, respectively mounted on the limb tips at opposite ends of the bow to provide the means to store more energy in the draw cycle and to reduce the force necessary to hold the bowstring in the full draw position. Examples of such compound bows are disclosed in the following U.S. patents. 
         [0003]    U.S. patent No. Issued To Date Issued U.S. Pat. No. 3,486,495 Allen Jun. 23, 1966 U.S. Pat. No. 3,890,951 Jennings, et al. Jun. 24, 1975 U.S. Pat. No. 4,060,066 Kudlacek Nov. 29, 1977 U.S. Pat. No. 4,079,723 Darlington Mar. 21, 1978 U.S. Pat. No. 4,112,909 Caldwell Sep. 12, 1978 U.S. Pat. No. 4,300,521 Schmitt Nov. 17, 1981. 
         [0004]    The early compound bows utilized cams consisting of eccentrically mounted circular shaped elements. As the desire for more stored energy and greater arrow velocities developed, special shaped cam elements were designed to provide these characteristics. These shaped cam elements, like the circular shaped elements, were mounted on the limb tips. It is well known in the art that to obtain the best bow performance, the cam elements at each end of the bow should be properly synchronized with each other. Patents disclosing various means to accomplish proper cam synchronization include the following: 
         [0005]    U.S. patent No. Issued To Date Issued U.S. Pat. No. 3,841,295 Hunger Oct. 15, 1974 U.S. Pat. No. 3,958,551 Ketchum May 25, 1976 U.S. Pat. No. 4,103,667 Shepley, Jr. Aug. 1, 1978 U.S. Pat. No. 4,178,905 Groner Dec. 18, 1979 
         [0006]    The more modern compound bows have reverted back to the more simplistic design of the original U.S. Pat. No. 3,486,495 Allen patent, but the requirement for cam synchronization is still present as noted, for example, by the teachings of the following patents: 
         [0007]    U.S. patent No. Issued To Date Issued U.S. Pat. No. 4,372,285 Simonds Feb. 8, 1983 U.S. Pat. No. 4,440,142 Simonds Apr. 3, 1984 U.S. Pat. No. 4,909,231 Larson Mar. 20, 1990 
         [0008]    It is obvious, of course, that the use of a single cam avoids the problem of cam synchronization and, in fact, there are single cam bows known in the prior art. One such bow, popularly referred to as the “DynaBo” was invented by Len Subber. The original Dynabo design had one working limb located at the upper end of the bow handle. A single cam element was mounted on a rigid pylori at the lower end of the bow. The single cam element functioned in the same manner as the cam elements on the previously mentioned two cam bows. As the Dynabo was drawn, one track of the cam element payed out line to the bowstring which was fixed to the upper limb tip and the other track on the cam element acted as a take-up reel for a second line that was also anchored at the tip of the upper working limb. 
         [0009]    Since there was only a single cam element, there was not a synchronization problem between two cams. There was, however, a problem in synchronizing the rate that the cam fed out cables to the bowstring at the lower end of the bow and the rate that the flexing of the upper limb feed out cable to the bowstring at the upper end as the bow was drawn. The result was a rather unpleasant feel to the bow as it was drawn and there was a drastic movement of the nocking point and the rear end of the arrow as the bow was drawn and released. This, in turn, made it very difficult to achieve good arrow flight from the bow under normal conditions. An early version of the DynaBo was described in the September 1976 edition of “Archery World” beginning at page 28. 
         [0010]    The Dynabo single cam concept was offered in at least three different versions from as many manufacturers during the 1970&#39;s, and at least one manufacturer, Graham&#39;s Custom Bows, employed the Dynabo concept, with two working limbs. A description of the Graham bow is contained in the June/July edition of “Archery World” magazine. The Dynabo bow, however, never did become an acceptable alternative to the two cam bows and, in fact, appears to have lost whatever popularity it had achieved by the late 1970&#39;s. 
         [0011]    Another known prior art device that had the capability of providing a solution to the previously mentioned problems of cam synchronization and synchronized bow string feed out (the latter being desirable to enable the nock end of the arrow to travel in a smooth, consistent path upon draw and release of the arrow) is set forth in U.S. Pat. No. 4,562,824 issued to Jennings. This patent teaches the use of a single multiple grooved cam mounted on a pylori attached to the bow handle. The cam had one string track feeding cable attached to an idler pulley mounted in the limb tip at one end of the bow and a second track feeding line to a second idler pulley mounted in the second limb tip at the other end of the bow. The cam also has two additional tracks, each of which are taking up line while the string tracks are feeding out line to the bow string. One take-up track is taking up a line which is anchored at one limb tip while the other take-up track is taking up a line which is anchored at the opposite limb tip. Thus, the &#39;824 patent teaches a highly complicated system, as compared to the present invention, that is composed of considerably more parts resulting in a compound bow having greater mass weight than the more conventional two cam compound bow. 
         [0012]    A single cam bow developed by Larry D. Miller in the late 1970&#39;s or early 1980&#39;s was the subject of a U.S. patent application titled “Archery Bow Assembly” (hereinafter referred to as the “Miller application”). The Miller application discloses the use of a single pulley, having two grooves thereon for feeding out line to the bow string. The primary groove is circular and concentric with the axle of the circular pulley. The secondary groove, also circular, may be slightly eccentric for the purpose of maintaining the nocking point of the bowstring perpendicular to the handle section of the bow. A third eccentric groove carries a take-up cable to provide the entire means of compounding (i.e. achieving the desired reduction in holding weight at full draw and storage of energy). 
         [0013]    The Miller application, the serial number of which is not known, may be considered material to the examination of the subject application. At least one bow was constructed which embodied the teachings of the Miller application, the applicant is unaware of the commercialization of any such bow. Thus, it is believed that the disclosure in the Miller application has been abandoned. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention embodies a simple, lightweight compound bow construction which solves the cam synchronization problem of two cam bows and overcomes the problems of synchronously feeding out cable to the upper and lower ends of the bowstring. The resulting bow has a smooth, desirable nocking point travel path which enables ease in matching arrows to the bow and provides consistency in performance. 
         [0015]    A cam is eccentrically journaled at one limb end of the bow and a pulley is journaled at the other limb end of the bow. A cable passes around the pulley to form a bowstring section and a second cable section, both sections forming a dual feed single cam compound bow. The amount of feed out to both ends of the bowstring is approximately the same. One embodiment of the drop-off cam provides a large periphery cam groove and a smaller periphery cam groove which are designed to synchronize the rate of cable feed-out at both ends of the bowstring section during the drawing operation. Other embodiments of the invention are also disclosed. 
         [0016]    An anchor cable is provided to tie the two limbs of the bow together during the flexing of the bow. The anchor cable may be fixed at one end to the axle of the concentric pulley and at the other end fixed in a groove in the cam to synchronize the flexing action of the bow limbs. 
     
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a side elevational view showing one embodiment of the invention; 
           [0018]      FIG. 2  is a side elevational view of the cam shown in  FIG. 1 ; 
           [0019]      FIG. 3  is the opposite side elevational view of the cam shown in  FIG. 2 ; 
           [0020]      FIG. 4  is a top plan view of the cam taken along line  4 - 4  of  FIG. 3 ; 
           [0021]      FIG. 5  is a rear elevational view of the upper limb tip portion of the archery bow of the present invention showing the anchor cable mounting on the concentric pulley axle; 
           [0022]      FIG. 6  is a view of the unassembled anchor cable of the present invention; 
           [0023]      FIG. 7  is a side elevational view, similar to the view, shown in  FIG. 2 , and showing an alternative embodiment of the cam of the present invention; 
           [0024]      FIG. 8  is a side elevational view, similar to the view shown in  FIG. 2 , and showing another embodiment of the cam of the present invention; 
           [0025]      FIG. 9  is a side elevational view, similar to the view shown in  FIG. 2 , and showing a still further embodiment of the cam of the present invention; 
           [0026]      FIG. 10  is the opposite side elevational view of the cam shown in  FIG. 9 ; 
           [0027]      FIG. 11  is a top plan view taken along line  11 - 11  of the cam shown in  FIG. 10 ; 
           [0028]      FIG. 12  is a side elevational view similar to the view shown in  FIG. 2 , and showing a still further embodiment of the cam of the present invention; 
           [0029]      FIG. 13  is the opposite side elevational view of the cam shown in  FIG. 12 ; 
           [0030]      FIG. 14  is a top plan view taken along line  14 - 14  of the cam shown in  FIG. 13 ; 
           [0031]      FIG. 15  is a side elevational view similar to the view shown in  FIG. 2 , and showing a still further embodiment of the cam of the present invention; 
           [0032]      FIG. 16  is the opposite side elevational view of the cam shown in  FIG. 15 ; and 
           [0033]      FIG. 17  is a top plan view taken along line  17 - 17  of the cam shown in  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    In  FIG. 1  of the accompanying drawings, an archery bow assembly B is illustrated which includes a central handle portion  10 , having a pair of limbs  12  and  14 , connected at their inner ends in fixed relation to the handle portion  10 . The limbs  12  and  14  provide the desired resistance to bending which determines the draw weight of the bow and the force with which the arrow is discharged. 
         [0035]    As shown in  FIGS. 1-4 , the outer ends of the bow limbs provide wheel receiving slots which define wheel mounting forks, respectively designated by the numbers  12   a  and  14   a , for mounting axle pins  15  and  16 . A pulley  17  is concentrically mounted on the axle pin  15 . In this form of the invention, the pulley  17  is provided with a single groove. As shown in  FIGS. 2-4 , an eccentric drop-off cam  18  is mounted on axle pin  16  and has three eccentrically oriented grooves,  18   a ,  18   b , and  18   c  formed in the outer periphery thereof to provide three separate cable groove paths. 
         [0036]    A cable  22  has a medial portion trained around concentric pulley wheel  17  to form a main cable section or bowstring  22   a  and a secondary or return section  22   b , both of which extend across the bow and terminate at the cam  18 . The ends  22   c  and  22   d  of the two sections  22   a  and  22   b  are respectively received in grooves  18   b  and  18   c  of the cam  18 . The end  22   c  and  22   d  of the sections  22   a  and  22   b  are anchored to the cam  18  as by the cable anchor pins  19   a  and  19   b  fixed in said cam  18 , as best shown in  FIG. 3 . In the form shown, three anchor pins  19   a  are provided to permit adjustment of the effective length of cable  22  and bowstring  22   a.    
         [0037]    An anchor cable  25  is anchored at one end  25   a  to the axle  15  (see  FIGS. 5 and 6 ) by loops  31  on sections  31   a  of anchor cable  25  encircling axle  15 . It is seen that loops  31  extend on both sides of pulley  17  to provide load balancing and thus prevent twisting of upper limb  12 . The other end of anchor cable  25  (as best shown in  FIG. 2 ) passes around the cam groove  18   a  on the take-up side of the cam  18  and has a loop  33  thereon which is attached to anchor pin  19   c  and positively ties the ends of the bow limbs  12  and  14  together to form a direct connection between the limbs  12  and  14 . 
         [0038]    The operation of the archery bow having the eccentric cam illustrated in  FIGS. 1-4  will next be described. When the archer draws the bowstring  22   a , cam  18  is caused to rotate in the counterclockwise direction as viewed in  FIG. 2  and bowstring  22   a  is fed out from cam  18  in the direction of the generally vertical arrow adjacent bowstring  22   a  in  FIG. 1 . Counterclockwise rotation of cam  18  likewise causes return section  22   b  to be fed out from cam  18  in the direction toward pulley  17 . Return section  22   b  moves upwardly to the take-up side of concentric pulley  17 , around and past the pulley  17  to become the second feed-out portion  22   a  of bowstring  22 . At the same time that the bowstring section  22   a  is fed out, counterclockwise rotation of cam  18  causes anchor cable  25  to be taken up in groove  18   a  of cam  18  to cause the synchronized flexing of the bow limbs  12  and  14 . 
         [0039]    Alternative forms of the invention are illustrated in  FIGS. 7 and 8 , but in each case the dual-feed-out cable sections  22   a  and  22   b  operate and extend outwardly from a drop-off cam unit mounted on the limb  14  of the bow in the same manner, as described for the embodiment shown in  FIGS. 1-4 . In the  FIG. 7  embodiment, an eccentric drop-off cam  27  is illustrated having the feed-out cable sections  22   a  and  22   b  extending outwardly therefrom toward the concentric pulley  17 . The cam  27  has a single groove  27   b  extending all around its complete periphery with the cable sections  22   a  and  22   b  received in the groove  27   b . The ends of the cable sections are anchored to an anchor pin  27   a  fixed to one side of the cam  27 . The anchor cable  25  is also received in groove  27   b  and securely anchored to the anchor pin  27   a , as shown in  FIG. 7 . 
         [0040]    Another alternative form of the cam is illustrated in  FIG. 8  which embodies eccentric drop-off cam  28  having a groove  28   b  thereon wherein cable sections  22   a  and  22   b  are received. A suitable anchor pin  28   a  is provided on the back side of the cam  28  as shown by dotted lines in  FIG. 8  and both ends of cable sections  22   a  and  22   b  are secured thereto in the same manner as previously described. The anchor cable  25  is trained in groove  29  of cam  28  and secured to the anchor pin  29   a  of cam  28  as shown in  FIG. 8 . Cam  28  is eccentrically mounted on axle pin  16  connected to the limb  14  of the bow. 
         [0041]    The embodiment of the cam shown in  FIGS. 9 to 11  also operates in the manner as the eccentric cam illustrated in  FIGS. 1 to 4 . In this embodiment, the eccentric drop-off cam  30  has the feed out sections  22   a  and  22   b  extending outwardly therefrom toward the concentric pulley  17  (not shown). Feed out section  22   a  is received in a first groove  32  of cam  30  and feed out section  22   b  is received in a second groove  34  of smaller periphery of cam  30  which is located on one side of groove  32  of cam  30 . Anchor cable  25 , as best seen in  FIGS. 9 and 11 , is located in groove  36  of cam  30 , which also is located on the side opposite of groove  32  from groove  34  of cam  30 . 
         [0042]    Feed out section  22   a , as best seen in  FIG. 10 , may be attached to either anchor pin  37  (as shown) or anchor pin  38  on cam  30 , and in this manner the effective length of feed out section  22   a  may be adjusted to change draw length. Feed out section  22   b , also as best seen in  FIG. 10 , is attached to anchor pin  40  on cam  30 . Anchor cable  25 , as best seen in  FIG. 9 , is attached to anchor pin  42  which is located on the side of cam  30  opposite anchor pins  36 ,  38  and  40 . As in the other embodiments, cam  30  is eccentrically mounted on the axle pin  16  connected to the limb  14  of the bow. 
         [0043]    The embodiment of the cam shown in  FIGS. 12 to 14  likewise operates in the manner as the eccentric cam illustrated in  FIGS. 1 to 4 . In this embodiment, the eccentric drop off cam  44  has the feed out sections  22   a  and  22   b  extending outwardly therefrom toward the concentric pulley  17  (not shown). Feed out section  22   a  is received in a first groove  46  of cam  44  and feed out section  22   b  is received in a second groove  48  of smaller periphery of cam  44  which is located outwardly of the center line of groove  46  of cam  44 . Anchor cable  25 , as best seen in  FIG. 12 , is located in groove  50  of cam  44 , which also is located outwardly of the center line of groove  46  of cam  44 . 
         [0044]    Feed out section  22   a , as best seen in  FIG. 13 , may be attached to either anchor pin  52  (as partially shown) or anchor pin  54  or anchor pin  56  on cam  44  and in this manner the effective length of the feed out section  22   a  may be adjusted. Feed out section  22   b , also as best seen in  FIG. 13 , is attached to anchor pin  58  on cam  44 . Anchor cable  25 , as best seen in  FIG. 12 , is attached to anchor pin  60  which is located on the side of cam  44  opposite anchor pins  52 ,  54 ,  56  and  58 . As in the other embodiments, cam  44  is eccentrically mounted on the axle pin  16  connected to the limb  14  of the bow. 
         [0045]    The embodiment of the cam shown in  FIGS. 15 to 17  operates in the manner as the eccentric cam illustrated in  FIGS. 1 to 4 . In this embodiment, the eccentric drop off cam  68  has the feed out sections  22   a  and  22   b  extending outwardly therefrom toward the concentric pulley  17  (not shown). Feed. out section  22   a  is received in a first groove  70  of cam  68  and feed. out section  22   b  is received in a second smaller periphery groove  72  of cam  68 . Anchor cable  25 , as best seen in  FIG. 16 , is located in groove  74  of cam  68 , which is located intermediate of grooves  70  and  72  of cam  68 . 
         [0046]    Feed out section  22   a , as best seen in  FIG. 15 , may be attached to either anchor pin  74  (as shown) or anchor pin  76  on cam  68  and in this manner the effective length of feed outsection  22   a  may be adjusted. Feed out section  22   b , as best seen in  FIG. 16 , is attached to anchor pin  78  on cam  68 . Anchor cable  25 , also as best seen in  FIG. 16 , is attached to anchor pin  80  which is located on cam  68 . As in the other embodiments, cam  68  is eccentrically mounted on the axle pin  16  connected to the limb  14  of the bow. 
         [0047]    It has been found that a desirable approach to designing the grooves in the cam is to initially have the groove which receives bowstring  22   a  (the “primary groove”) be approximately twice the peripheral size of the groove which receives the bowstring  22   b  (the “secondary groove”). The size of the primary groove may, for example, be the peripheral size of a cam on a standard bow having two independent cams. A starting point for the design of the groove which receives anchor cable  25  (the “take up groove”) for use on limbs having relatively low spring rates and relatively longer limb tip travel may be, for example, to have the size and shape of the take up groove be approximately the same size and shape as the primary groove. If, however, one desires limbs having a higher spring rate and desires to reduce limb tip travel, the take up cam size will be smaller than that of the primary feed cam for a given peak draw weight. Conversely, if one desires limbs having a lower spring rate and desires to increase limb tip travel, the take up cam size would be larger than that of the primary feed cam for a given peak draw weight. The final shape of the take up cam will depend on the energy storage characteristics that are desired. Adjustments of the peripheral size and shape will then be made to the secondary groove to assure that the nocking point travels in a smooth path during the draw cycle. To achieve this, the bowstring is drawn at discrete draw length intervals, for example, at draw length intervals of one inch and at each such interval the nocking point position and travel is analyzed and, if required, the secondary groove is made either peripherally larger or smaller to assure that the nocking point travels a smooth path between intervals. By continuing this process of modifying the size and shape of the secondary groove throughout the draw length, the resulting single cam compound bow will, among other desirable features, be provided with a smooth nocking point path of travel. It should be noted that the amount of stored energy will be directly related to the leverage ratios between the primary, secondary groove shapes and will depend on the combined effect of the two bowstring let off leverage arms as compared to the leverage arm of the bowstring take up side.