Patent Publication Number: US-11022398-B1

Title: Projectile launching device with self-timing and without cam lean

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a non-provisional patent application, which claims the benefit of provisional application No. 62/864,056, filed on Jun. 20, 2019. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to archery and more specifically to a shooting bow with a unique cable arrangement, which allows a portion of first and/or second cables to be slidably engaged to a first and second pulley, and the ends of each cable are anchored to the same cam. This arrangement enables the device to have self-timing. The present invention may alternately use components other than flexible limbs for storing energy prior to launching the projectile. 
     Discussion of the Prior Art 
     Historically, archery bows and crossbows have been used for war, survival, sport, and recreation. A specific component of a compound style shooting bow are the cables. Typically, each cable includes a power end and a control end. The manner in which the cables interact with the cams and limbs of the bow is of particular importance. Typically, the power end of the cable is coupled to the cam on one limb, and the control end of the cable is often coupled to the opposite limb or opposite cam. A very good way to accomplish efficiency is through a binary cam system, wherein the cables are connected to opposing cams, and as one of the cams wraps the cable on the power track, the opposite cam pays out cable from the control track. While all of these methods work to some extent, all have significant issues with performance related to cam lean, and/or assembly and cost. Due to the crossing of cables and the need to keep the cables from interfering with the flight of the arrow, the cables often are off-angle, which in turn creates twisting and torque in a cam axle, thus creating cam lean. 
     U.S. Pat. No. 4,457,288 to Ricord discloses a cam lever compound bow, where a bow utilizes single string wrapping pulleys journaled to the ends of the bow limbs, and the ends of the string are coupled to a cam device mounted upon the bow riser. Although, this method does remove the problem of the cables being in the way, it is very inefficient, and timing issues from one limb to the other is a factor. U.S. Pat. No. 7,637,256 to Lee discloses a compound bow, which provides a shooting bow that removes the issue of cables interfering with the flight of the arrow. However, the inefficient use of tensioning devices severely limits the potential of this device. U.S. Pat. No. 8,651,095 to Islas discloses a bowstring cam arrangement for compound crossbow, which provides a method of removing the cables from the path of the string. U.S. Pat. No. 9,494,379 to Yehle discloses a crossbow, where Yehle relies on four cables. Issues are created by having separate cables above and below the string track on each cam. If the cables are not of exact length, or if the upper cable stretches more than the lower cable, or visa-versa, the cables must be adjusted by the user to stay in time with each other. Timing of the cables can be a time consuming and a very difficult process. U.S. Pat. No. 9,759,509 to Kempf teaches a cable configuration wherein the cables are anchored to the cams, which allows for self-timing. More recently, Hoyt introduced a cable configuration wherein the ends of the cable are anchored to the cam, and a central portion of the cable passes through a sleeve. This system is beneficial, however still lacks the smooth passage of the cables to self-time, further there is no provision for the cams to rotate more than about 180 degrees. The present invention deals with the manner in which the cables are coupled to the cams of the bow or crossbow. 
     Accordingly, there is a clearly felt need in the art to provide a shooting bow, which allows a mid-portion of first and second cables to be slidably engaged on a first and second pulley, and the ends of the cables are coupled to the same cam, respectively, wherein the cam is allowed to rotate at least 200 degrees, up to at least 360 degrees. Historically with all prior art, cams that rotate more than 200 degrees up to about 300 degrees do not require the use of a wider cable track, as the cables are not required to stack upon themselves. The cables do not cross the centerline of the shooting bow. Additionally, the cams are allowed to rotate 360 degrees due to a wider upper and lower cable track, or alternately a divided helical cable track, which allows the cable to wrap adjacent to itself. 
     SUMMARY OF THE INVENTION 
     The present invention provides a self-timing cam and cable configuration for a projectile launching device. The present invention includes a pair of cables, wherein both ends of the same cable anchors to the same cam(s), and also reduces or eliminates cam lean. The projectile launching device with self-timing and without cam lean (projectile launch device) may be applied to either a crossbow or vertical bow. The projectile launch device preferably includes a first cam, a second cam, a launch string and two cables, collectively known as a harness system. This configuration allows opposing ends of a first cable to be anchored to a first cam, and opposing end of a second cable to be anchored to a second cam. Preferably, the first and second cables do not cross a centerline of the shooting bow. In a second preferred embodiment, the projectile launching device preferably includes a string latch housing, a bow riser, a rail, a first energy storing device (such as a first limb), a second energy storing device (such as a second limb), a first cam, a second cam, at least one bowstring, and two cables. 
     The term “limb” may refer to what are known as solid limbs, split-limbs, tube-limbs, or any other flexible energy storing component. The bow riser is enjoined with the rail. One end of the first limb extends from a first end of the bow riser and one end of the second limb extends from a second end of the bow riser. The first cam is pivotally retained on the first limb and the second cam is pivotally retained on the second limb. A first end of the launch string is retained by the first cam and a second end of the launch string is retained by the second cam. On an alternative embodiment, a first set of first and second cable posts are located on a first side of a centerline of the rail and a second set of first and second cable posts are located on a second side of the centerline of the rail. These cable posts may be used to anchor a secondary set of cables which support the cable pulleys. The first cam includes a first cam launch string track, an upper first cam cable track, located above the launch string track, and a lower first cam cable track, located below the launch string track. The second cam includes a second cam launch string track, an upper second cam cable track, located above the launch string track, and a lower second cam cable track, located below the launch string track. The first set of first and second cable posts are located above the plane of the launch string, and the second set of first and second cable posts are located below the plane of the launch string. 
     A first end of the first cable is coupled to the first cam first cable post; a segment of the first cable before a middle of the first cable partially engages the first cable pulley; the middle of the first cable partially wraps the first cable track; a segment of the first cable after the middle of the first cable partially engages the first cam second cable track; and a second end of the first cable is coupled to the first cable second cable post. A first end of the second cable is coupled to the second cam first cable post; a segment of the second cable before a middle of the second cable partially engages the second cam first cable track; the middle of the second cable partially wraps the second cable pulley; a segment of the second cable after the middle of the second cable partially engages the second cam second cable track; and a second end of the second cable is coupled to the second cable second cable post. 
     When the launch string is drawn from a rest position to a ready to fire position, the first cam rotates in a first direction and the second cam rotates in a second direction. As the first and second cams rotate, the launch string is unwound from the first and second launch string tracks. Simultaneously, the first and second cables wind into the first and second cable tracks of the first and second cams. 
     A unique feature of the present invention is that both ends of the first and second cables are firmly fixed to the same cam, and the middle portions “float” or slide relative to the first and second cable pulleys. The first and second cables are of one piece, and as the cable stretches, it self-centers itself about the cable pulleys. The term “pulley” is used as a general term for a component or feature engaging the cables to allow for the smooth transition of a segment of the cables from above the bowstring to below the bowstring, from a first side of the cams to a second side of the cams, wherein the component or feature (the cable retention transition) is coupled with the frame, structure, support, barrel, or riser, providing a slide-able retention position for the segment of the cables. The cable retention transition preferably has a curved shape, which the cable makes contact with, but other shapes may also be used. 
     Another unique feature of the present invention is the ability of the cam to rotate a full 360 degrees, such that as the cams are rotating, the upper and lower cable portions wrap the cable cams. 
     In a preferred embodiment, the launch string may be releasably retained in the ready-to-fire position by mechanisms known as a string latch assembly or a string release. 
     In a first preferred alternative embodiment, the launch string may be held in the ready-to-fire position and released by the users&#39; fingers. 
     In a second preferred alternative embodiment, a rail-less crossbow design may be used. 
     In a third preferred alternative embodiment, the same harness system configuration may be used on projectile launching devices utilizing energy storing components other than flexible limbs. These other types of energy storing components include spring(s), hydraulics, or pressurized cylinder(s). 
     For clarity, the word coupled is being defined as a way to connect an object, such as a bowstring or cable, with another object, be it directly or indirectly, such as directly to a post or pulley, or indirectly as in from the end of a string or cable, to an intermediate object, and then to a limb or axle. 
     Though the term “pulley” has been used throughout the application, “pulley” references the component used to slidably retain and transition the cables from a first side of the bowstring track to a second side of the bowstring track, any component fulfilling the same function may be utilized and may or may not be known as a pulley in the traditional sense, and may or may not function as a rotatable pulley, as rotation of the component is not a prerequisite to retention and transition of said the cables. 
     The term “rail” is used as a general term describing an elongated component that directly or indirectly supports the front of an arrow. “Rail-less” crossbows still have an elongated component that is coupled with a riser or other structure, wherein the elongated component directly or indirectly supports the front of an arrow. 
     The term “slidably” as used in the application as to reference how a segment of the cables engage the cable “pulleys”, in that the mid-segment of the cable is retained by, and not fixed to, the “pulley”. The first and second ends of the cables are anchored in a fixed position relative to each other, preventing the mid-segment of the cables from actually moving back and forth, or sliding. 
     Accordingly, there is a clearly felt need in the art for a projectile launching device with no cam lean, having a first cam, a second cam, a launch string and at least two cables, collectively known as a harness system, where both ends of the same cable are rigidly attached to the same cam, and the mid-portion of each cable at least partially wraps a cable pulley. 
     Further, there is a clearly felt need in the art to provide a shooting bow, which allows a mid-portion of first and second cables to be slidably engaged on a first and second pulley, and the ends of the cables are coupled to the same cam, respectively, wherein the cam is allowed to rotate at least 200 degrees up to about 300 degrees, and up to at least 360 degrees. Historically with all prior art, cams that rotate more than 200 degrees up to about 300 degrees do not require the use of a wider cable track, as the cables are not required to stack upon themselves. The cables do not cross the centerline of the shooting bow. 
     Finally, the cams may be allowed to rotate up to 360 degrees due to a wider upper and lower cable track, or alternately a divided helical cable track, which allows the cable to wrap adjacent to itself. 
     With reference to  FIGS. 4A-4D and 5A-5D , the mid-segment of the first and second cables  44 ,  46  “slidably” engage the first and second cable pulleys  215  and  216 , which allows the first and second cables  44 ,  46  to self-center themselves relative to a first side and a second side of the first and second cams  18  and  20 . The self-centering feature of the cables  44 ,  46  provides for automatic cable timing, which eliminates cam lean, and timing issues. As the launch string  22  is drawn, the launch string unwraps, or “pays out” from the first and second cams  18 ,  20 . Simultaneously, the first and second cables  44 ,  46  wrap the respective first cable tracks  70 ,  75  and the second cable tracks  72 ,  77 . 
     These and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a partial rear view of a vertical bow of the present invention, having a first and second cam, a first and second cable, and a string, wherein opposing ends of the same cable are anchored to the same cam, and a mid-portion of the cables partially wrap a cable pulley of the present invention. 
         FIG. 1B  is a partial rear view of a vertical bow of the present invention, having a first and second cam, a cable, and a string, wherein opposing ends of the same cable are anchored to the same cam, and a mid-portion of the cables partially wrap a cable pulley of the present invention. 
         FIG. 2A  is a top view of a conventional limb crossbow with inverted cams of the present invention in an at-rest position, having first and second cams; first and second cables; and a string, wherein opposing ends of the same cable are anchored to the same cam, and a mid-portion of the cables partially wrap a cable pulley of the present invention. 
         FIG. 2B  is a top view of a reverse draw crossbow of the present invention in an at-rest position, having first and second cams; first and second cables; and a string, wherein opposing ends of the same cable are anchored to the same cam, and a mid-portion of the cables partially wrap a cable pulley of the present invention. 
         FIG. 2C  is a perspective view of a crossbow with the string at rest where each end of a first cable is anchored to a first cam, each end of a second cable is anchored to a second cam, and first and second directional transition components are located between the cams and the cable pulley of the present invention. 
         FIG. 2D  is a first close up view of  FIG. 2C  of the present invention. 
         FIG. 2E  is a second close up view of  FIG. 2C  of the present invention. 
         FIG. 3  is a top view of a conventional limb crossbow with inverted cams of the present invention in an at-rest position, having first and second cams; first and second cables; and a string, wherein opposing ends of the same cable are anchored to the same cam, and a mid-portion of the cables partially wrap a cable pulley of the present invention. 
         FIG. 3A  is a side cut-away view of a second multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower cable track that is at least twice as wide as the width of the cables; opposing ends of the second cable are anchored to the same post on the second cam, and a mid-portion of said second cable partially wraps a second cable pulley, a string and second cable are illustrated with the cam of the present invention. 
         FIG. 4A  is a top view of a first multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4B  is a bottom view of a first multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4C  is a side cut-away view of a first multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower cable track, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4D  is an exploded side view of a first multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower cable track, and having first and second mirror image modules of the present invention. 
         FIG. 4E  is a side cut-away view of a second multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower cable track, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4F  is an exploded side view of a second multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower cable track, and having first and second mirror image modules of the present invention. 
         FIG. 4G  is a side cut-away view of a first multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower helical cable track, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4H  is an exploded side view of a first multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower helical cable track, and having first and second mirror image modules of the present invention. 
         FIG. 4I  is a side cut-away view of a second multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower helical cable track, a string and cable are illustrated with the cam of the present invention. 
         FIG. 4J  is an exploded side view of a second multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower helical cable track, and having first and second mirror image modules of the present invention. 
         FIG. 5A  is a top view of a second multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 5B  is a bottom view of a second multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 5C  is an exploded side view of a second multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower cable track that, and having a first and second mirror image modules of the present invention. 
         FIG. 5D  is a side cut-away view of a second multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower cable track; opposing ends of the second cable are anchored to the second cam, and a mid-segment of said second cable partially wraps a second cable pulley, a string and second cable are illustrated with the cam of the present invention. 
         FIG. 5E  is a top view of a first multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 5F  is a bottom view of a first multi-piece cam with non-circular cable tracks of the present invention, a string and cable are illustrated with the cam of the present invention. 
         FIG. 5G  is an exploded side view of a first multi-piece piece cam with non-circular cable tracks of the present invention having an upper and lower cable track, and having a first and second mirror image modules of the present invention. 
         FIG. 5H  is a side cut-away view of a first multi-piece cam with non-circular cable tracks of the present invention, having an upper and lower cable track; opposing ends of the first cable are anchored to the first cam, and a mid-segment of said first cable partially wraps a first cable pulley, a string and first cable are illustrated with the cam of the present invention. 
         FIG. 6A  is a top view of first and second multi-piece cams with non-circular cable tracks of the present invention; having an upper and lower cable track, modules have been removed for illustrative purposes; a string and cable are illustrated with the cam in a drawn position of the present invention. 
         FIG. 6B  is a bottom view of first and second multi-piece cams with non-circular cable tracks of the present invention, having an upper and lower cable, modules have been removed for illustrative purposes; a string and cable are illustrated with the cam in a drawn position of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings,  FIGS. 1, 1A and 1B  show views of a vertical bow-type projectile launching device  2 . The projectile launching device  2  preferably includes a bow riser  10 , a first limb  14 , a second limb  16 , a first cam  18 , a second cam  20  and a launch string  22 . One end of the first limb  14  is attached to a first end of the bow riser  10  and one end of the second limb  16  is attached to a second end of the bow riser  10 . The first cam  18  is pivotally retained on an opposing end of the first limb  14  with a first axle  31  and the second cam  20  is pivotally retained on an opposing end of the second limb  16  with a second axle  32 . 
     With more specific reference to  FIG. 1A , the disclosed embodiment illustrates a vertical bow  2  having a first cable  44  and a second cable  46 , wherein a first end of the first cable  44  is anchored to a first cable first post  210 , and a second end of the first cable  44  is anchored to a first cable second cable post  212 . A first end of the second cable  46  is anchored to a second cable first cable post  211  and a second end of the second cable  46  is anchored to a second cable second post  213 . A first cable spanner bar  82  is coupled to the riser  10  on a first side of the launch string  22 , and a second cable spanner bar  83  is coupled to the riser  10  on a second side of the launch string  22 . The cable spanner bars  82  and  83  displace the first and second pulley mounting cables  45  and  47  a distance away from the launch string  22  to allow clearance for an arrow  33 . 
     More specifically referring to  FIG. 1B , the disclosed embodiment illustrates a vertical bow  2 . The first spanner bar  82  is coupled to the riser  10  on the first side of the launch string  22 , and the second spanner bar  83  is coupled to the riser  10  on the second side of the launch string  22 . A first end of a first cable  44  is coupled to a first cam  18  first cable anchor  210 , a mid-segment of said first cable partially wraps a first cable pulley  215 , and a second end of said first cable anchors to a first cam  18  second cable post  212 . A first end of a second cable  46  is coupled to a second cam  20  first cable anchor  211 , a mid-segment of said second cable  46  partially wraps a second cable pulley  216 , and a second end of said second cable  46  anchors to a second cam  18  second cable post  213 . The first cable pulley  215  is coupled to a first pulley mounting cable  45  and first and second first pulley mounting cable post  24  and  26 . The second cable pulley  216  is coupled to a second pulley or transition mounting cable  47  and first and second second-pulley mounting cable post  25  and  27 . 
       FIGS. 2A and 2B  illustrate a crossbow  1  of the current invention. The bow riser  10  may be joined with the rail  12  in any method known to join two pieces, as well as the rail  12  and the riser  10  being formed together as a single unit. The projectile launching device  1  preferably includes the riser  10 , the rail  12 , a first limb  14 , a second limb  16 , a first cam  18 , a second cam  20  and a launch string  22 . 
     A first end of the first limb  14  is coupled to a first end of the bow riser  10  and a first end of the second limb  16  is coupled to a second end of the bow riser  10 . The first cam  18  is pivotally retained on an opposing end of the first limb  14  and the second cam  20  is pivotally retained on an opposing end of the second limb  16 . The crossbow  1  includes a first cable  44  and a second cable  46 . With reference to  FIGS. 2A and 2B , the first end of the first cable  44  is anchored to the first cable first post  210 , and the second end of the first cable  44  is anchored to the first cam second cable post  212 . The first end of the second cable  46  is anchored to the second cable first cable post  211 , and the second end of the second cable  46  is anchored to the second cable second post  213 . 
     The first end of the first pulley mounting cable  45  is coupled to a first cable pulley or the first cable retention transition  215  and a first pulley mounting cable first and second post  24  and  26  ( 26  not shown). The first end of the second pulley mounting cable  47  is coupled to a second cable pulley or the second cable retention transition  216  and a second pulley mounting cable first and second post  25  and  27  ( 27  not shown). 
       FIGS. 2C-2E , disclose a first and a second cable  44  and  46 , each cable having a first end and a second end; and a first and a second cam  18  and  20 . The first end of the first cable  44  is anchored to the first cam  18  and engages a first cable track of the first cam  18 ; the first cable  44  then spans to a first directional transition  408 , (A component that alters the direction of the span. The directional transition may be of any smooth-surface that retains the cable.) The first cable  44  then spans to and is retained by a first cable pulley  215 , the first cable  44  then spans to a second directional transition (not shown), then spans to engage a second cable track of the first cam  44 , and the second end of the first cable  44  is anchored to the first cam  18 . The first end of the second cable  46  is anchored to the second cam  20  and engages a first cable track of the second cam  20 ; the second cable  46  then spans to a third directional transition  402 , then spans to and is retained by a second cable pulley  216 , the second cable  46  then spans to a fourth directional transition  400 , then spans to engage a second cable track of the second cam  20 , and the second end of the second cable  46  is anchored to the second cam  20 . The first and second directional transitions are a mirror of the third and fourth directional transitions  400 ,  402 . The use of directional transitions allows for flexibility in design, and management of structural forces that would be impossible without them. 
     With reference to  FIG. 3 , a similar crossbow is shown as relates to  FIG. 2 , however the first and second ends of the first cable  44  are anchored to a first cam single cable post  217  on a first cam  18 , and the first and second ends of the second cable  46  are anchored to a second cam single cable post  218  on the second cam  20 .  FIG. 3A  shows a partial cross section view of the crossbow of  FIG. 3 , wherein the first and second ends of cable  46  are anchored to a first cam  18  first cam single cable post  217 . 
     Referring to  FIGS. 4A-4J , the first cam  18  includes a first launch string track  19 , a first cam upper cable track  40 , a first cam launch string post  61 , and a first cam lower cable track  41 . A first end of the launch string  22  is retained by the first cam launch string post  61 ; a portion of the span of the launch string  22  at least partially wraps around the first cam  18  in the first cam launch string track  19 ; a portion of the span of the launch string  22  at least partially wraps the second cam  20  in the second cam launch string track  21 , and a second end of the bowstring  22  is retained by the second cam launch string post  63 . 
     The first end of the first cable  44  is coupled to the first cam first cable post  210 ; a segment of the first cable  44  partially engages the first cam upper cable track  40 ; the middle of the first cable  44  is retained by the first cable pulley  215  (not shown); a segment of the first cable  44  partially engages the first cam lower cable track  41 ; and the second end of the first cable  44  is coupled to the first cam second cable post  212 . The first end of the second cable  46  is coupled to the second cam first cable post  211 ; a segment of the first cable  46  partially engages the second cam upper cable track  40 ; the middle of the first cable  46  is retained by the  216  (not shown); a segment of the second cable  46  partially engages the second cam lower cable track  41 ; and the second end of the second cable  46  is coupled to the second cam second cable post  213 . 
     With reference to  FIGS. 6A and 6B , when the launch string  22  is drawn from a rest position to a ready to fire position, the first cam  18  rotates in a first direction, and the second cam  20  rotates in a second direction. As the cams  18  and  20  rotate, the launch string  22  is unwound from the first and second launch string tracks  19  and  21 . Simultaneously, the cables  44  and  46  wind into the first and second upper cable tracks  40  and  42  and the first and second lower cable tracks  41  and  43  of the first  18  and second  20  cams. When the launch string  22  has been drawn to the ready-to-fire position, it may be held in this the position by an operably releasable catch located in a housing  56 . The first cable  44  is slide-able relative to the first cable pulley  215  and the second cable  46  is slide-able relative to the second cable pulley  216 . The upper cable track  40 , the lower cable track  41 , the upper cable track  42  and the lower cable track  43  may be generally circular, or non-circular. 
       FIGS. 4A-4D and 5A-5D  illustrate an embodiment of the first cam  18  of the current invention with string and cable(s), wherein the first cam  18  is constructed of a modular type construction. In this type of construction, the first and second side of the first cam  18  and the second cam  20  are mirror images of each other, and the first cam  18  is identical and interchangeable with the second cam  20 . The first cam  18  includes a first module  70  and a second module  75 . The first and second modules  70 ,  75  are mirror images of each other. The first and second modules  70 ,  75  are identical and are interchangeable with a first module  72  and a second module  77  of the second cam  20 . Specifically,  FIG. 4A  is a top view of the first cam  18 ,  FIG. 4B  is a bottom view of the first cam  18 ,  FIG. 4C  is a cut-away view of the first cam  18  with the string  22  and the cable  44 . The first module  70  and the second module  75  may be generally non-circular, or circular. 
       FIGS. 4G-4J  illustrate an alternate embodiment of the first cam  18  of the current invention with string and cable(s), wherein the first cam  18  is constructed of a modular type construction. In this type of construction, the first and second side of the first cam  18  and the second cam  20  are mirror images of each other, and the first cam  18  is identical and interchangeable with the second cam  20 . The first cam  18  includes a first helical module  70  and a second helical module  75 . The first and second helical modules  70 ,  75  are mirror images of each other. The first and second helical modules  70 ,  75  are identical and are interchangeable with a first module  72  and a second module  77  of the second cam  20 . 
       FIGS. 5A-5D  illustrate an embodiment of the second cam  20  of the current invention, with string and cable(s), wherein the second cam  20  is constructed of a modular type construction. In this type of construction, the first and second side of the second cam  20  and the first cam  18  are mirror images of each other, and the first cam  18  is identical and interchangeable with the second cam  20 . The first module  72  and the second module  77  are mirror images of each other, and the first and second modules  70  and  75  are identical and interchangeable with the first and second modules  72  and  77 . Specifically,  FIG. 5A  is a top view of the second cam  20 ,  FIG. 5B  is a bottom view of the second cam  20 ,  FIG. 5C  is a cut-away view of a second cam with the string  22  and the cable  46 . The first module  72  and the second cable module  77  may be generally non-circular, or circular.  FIG. 6A  illustrates a top view of the first cam  18  and the second cam  20 , in the drawn position.  FIG. 6B  illustrates a bottom view of the first cam  18  and the second cam  20 , in the drawn position.  FIGS. 6A and 6B  are identical to each other and not just mirror images, as described previously in  FIGS. 5A-5D . This feature allows for an easier method of manufacture and assembly. 
     A first end of the launch string  22  is anchored to the first cam string post  61 ; a segment of the launch string  22  partially wraps cam  18  in the string track  19 ; the string crosses the center of the riser  10 ; and partially wraps the second cam  20  in the string track  21 ; and the second end of the launch string  22  is anchored to the second cam string post  63 . 
     With reference to  FIGS. 4A-4D and 5A-5D , the mid-segment of the first and second cables  44 ,  46  “slide-ably” engage the first and second cable pulleys  215  and  216 , which allows the first and second cables  44 ,  46  to self-center themselves relative to a first side and a second side of the first and second cams  18  and  20 . The self-centering feature of the cables  44 ,  46  provides for automatic cable timing, which eliminates cam lean, and timing issues. As the launch string  22  is drawn, the launch string unwraps, or “pays out” from the first and second cams  18 ,  20 . Simultaneously, the first and second cables  44 ,  46  wrap the respective first cable tracks  70 ,  75  and the second cable tracks  72 ,  77 . 
     It is preferable that the second ends of the first and second cables  44  and  46  not be anchored to the same post. However the first and second cables  44 ,  46  will still function satisfactorily if anchored to the same post. 
     While the preferred embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.