PATENT ABSTRACT
Improved compound bows which are smaller, more compact, lighter, and more easily handled and serviced than compound bows of conventional construction but are nevertheless capable of propelling an arrow at an equal or higher velocity and with comparable or greater accuracy than a conventional bow. The improved bows are quieter than those of conventional construction and less apt to snag on brush or other obstacles. They have a rigid riser with ends to which string cams are rotatably mounted and cam-associated power units mounted to and towards the ends of the riser. Each power unit has a component which is elastically deformed to store potential energy as the bow is drawn and a power cable connecting the power storing component to the associated string cam. A bow string extends between and is connected at its opposite ends to the string cams. As the bow is drawn, the string cams are rotated in counter directions, pulling on the power unit cables and thereby elastically deforming and storing potential energy in the power unit components. When the bow string is subsequently released, the elastically deformable power unit components restore to rest configurations, this converting the stored potential energy to arrow propelling kinetic energy. A timing cable arrangement insures that the cams are synchronized to rotate in unison, avoiding the unwanted nock travel that might otherwise occur; and the power units have an adjustment feature which allows the force required to fully draw the bow to be changed.

PATENT DESCRIPTION
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention relates to novel, improved, compound archery bows.  
       BACKGROUND OF THE INVENTION  
       [0002]     The compound bow is a relatively recent development. It has been reported that the first patent on a compound bow is U.S. Pat. No. 3,486,495 issued 30 Dec. 1969.  
         [0003]     Modern compound bows are instruments of considerable sophistication and not insignificant complexity.  
         [0004]     A bow of this type has a rigid riser with a grip for the archer and flexible limbs extending in opposite directions from the two, opposite ends of the riser. A rotatable cam and a wheel (single cam bow) or two rotatable cams (double cam bow) are mounted to and move with the extreme ends of the flexible bow limbs as the bow is drawn and as the bow string is subsequently released.  
         [0005]     A bow string is connected between the cams, which rotate in opposite directions when the bow is drawn. As the bow is drawn, the bow string moves away from the limb/riser assembly of the bow. This displacement is the greatest at the location where the arrow is nocked to the bow string.  
         [0006]     Modern compound bows typically have cam surfaces with a let-off segment contacted by the bow string for that part of the draw ending with the bow being fully drawn. The let-off reduces the force required to draw the bow over that part of the draw where the let-off is in play. Also, the force required to hold the bow at full draw is reduced, which is of obvious benefit to the archer.  
         [0007]     When a conventional, double cam, compound bow is drawn, the two cams of the bow tend to rotate at different rates. As a result, one cam can reach the beginning of its let-off before the other cam does. If this happens, the cam that is lagging behind will overpower the cam which reaches let-off first. This causes the leading cam to rotate backwards, i.e., in the same direction as the lagging cam. As a result, the nock position of the arrow becomes unstable and moves up (or down) from the centered position. A conventional compound bow of the type under consideration is not self-centering, and this movement of the nock position away from the centered position continues until full draw is reached. This displacement of the nock position makes an accurate shot unlikely, if not impossible.  
         [0008]     A relatively complicated and expensive buss system is conventionally employed to ensure that the two cams of a double cam, compound bow rotate in unison and that the two cams accordingly reach let-off simultaneously, even though the buss system adds complexity and cost to a bow. A typical buss system has buss cables which extend between the string cams of the bow and are connected to the string cams and the limbs of the bow; a cable guide; and a riser-mounted support for the cable guide.  
         [0009]     Aside from its complexity and cost, the buss system of a conventional bow has the disadvantage that the buss system cables are moved sideways to clear the arrow path as the bow is drawn. This puts sideways pressure on the bow limbs, which causes them to drift sideways. When the arrow is released, the bow limbs snap back into alignment. This sudden movement also contributes to the inaccuracy of a shot made from a conventional compound bow.  
         [0010]     The bow is drawn by pulling on a bow string which is anchored to the cams (or cam and wheel) of the bow. When the bow string is released, the flexible limbs of the bow restore toward their rest configurations; and the potential energy stored in the limbs is converted to kinetic energy, rapidly displacing the bow string to its rest configuration and launching an arrow nocked to the bow string.  
         [0011]     A conventional compound bow has a large mass in motion when an arrow is released, due in large part to the moving mass of the bow limbs and cams as the limbs restore from the stressed configurations they have at full draw to their rest configurations. When the limbs and other moving bow parts reach their rest configurations, they slam to a stop; and shock and vibration are set up in the bow and transferred by way of the bow riser to the archer. The shock and vibration can cause the archer to flinch because of the sting felt when the arrow is fired. Flinching leads to a wild shot.  
         [0012]     Another disadvantage of many compound bows is that they are noisy, in large part due to the vibration-caused rattling and other movements of bow components as they move to and reach their rest positions. Particularly in the case of a close shot, a game animal can clearly hear and locate the bow noise and react fast enough to move before the arrow reaches the animal. This may result in a wounded animal or a missed shot.  
         [0013]     Also, the flexible limbs of a conventional compound bow are susceptible to breakage, especially if a bow is dry fired; i.e., discharged without an arrow. The repair and other problems a broken bow limb can cause a hunter in the field are obvious, and a breaking bow limb can fly into and seriously injure the archer.  
       SUMMARY OF THE INVENTION  
       [0014]     Novel, improved bows which are free of the disadvantages identified above and which have other significant benefits have now been invented and are disclosed herein.  
         [0015]     The novel bows of the present invention have an elongated, rigid riser. This riser may be of a skeleton construction, desirably reducing the weight of this component and making the bow aesthetically pleasing.  
         [0016]     Like a conventional compound bow, those disclosed herein have string cams to which the opposite ends of a bow string extending in the direction of the riser&#39;s axis of elongation are attached. However, these cams are rotatably mounted to opposite ends of the rigid riser rather than to the ends of flexible limbs as they are in a conventional compound bow. Consequently, the cams rotate as the bow is drawn and upon bow string release, but the cams do not otherwise move during the bow drawing/bow string release cycle.  
         [0017]     The force for propelling an arrow is generated in bows embodying the principles of the present invention by string cam-associated power units. These power units are also mounted at the ends of the rigid riser and, like the string cams, they do not, as a whole, move during the bow drawing/bow string release cycle.  
         [0018]     Each of the cam string-associated power units includes an elastically deformable power-generating component which is anchored at one end and free to move at the second, opposite, component end. The free end of each power-generating component is fixed to a power cam which rotates with the associated string cam by a power cable or other force/motion transmitting mechanism. Therefore, when the bow is drawn by pulling on the bow string at the midpoint of that component, the string cams are rotated (in opposite directions), concomitantly rotating the power cams and pulling on the power cables, thereby elastically deforming the power-generating components and storing potential energy in those components. When the bow string is subsequently released, the force-generating components restore to their rest positions, converting the stored potential energy to kinetic energy for propelling an arrow from the bow.  
         [0019]     As in the case of a conventional bow, it is important that the string cams of a bow embodying the principles of the present invention rotate in unison to eliminate (or at least drastically reduce) nock travel and the degradation in accuracy attributable to that phenomenon. The buss system employed in a conventional bow and the problems associated with such a system are eliminated by using a simple timing cable which is fixed at its opposite ends to riser-mounted timing wheels. These wheels rotate with the string cams as the bow is drawn and after the bow string is subsequently released.  
         [0020]     Another of the important advantages of the bows disclosed herein is that they have low residual energy; i.e., there is very little energy left in the bow after the arrow leaves the bow. In contrast, a conventional compound bow has high residual energy because of the substantial mass of the bow components moving to their rest positions when an arrow is released and the large displacements of those components. These components include the long and relatively heavy limbs of a conventional bow; the weighty, limb-mounted string cams, which move forwardly and outwardly through considerable distances at the ends of the bow limbs; and the components of the buss system including its cables and the slide used to keep the buss cables out of the path of the arrow as it is propelled from the bow.  
         [0021]     The residual energy in a typical compound bow is so high that the bow actually shakes as the moving bow components reach their rest positions and come to a stop. All of this residual energy is converted to noise and other vibrations and ultimately to heat. One important adverse effect of high residual energy is the degradation in accuracy attributable to the bow shaking. Another is that a conventional bow with its high residual energy is inefficient because a significant part of the energy generated when the bow string is released remains in the bow instead of being transferred to the arrow propelled from the bow.  
         [0022]     In contrast, the bows disclosed herein have only low residual energy because: (a) the string cams rotate but do not otherwise move relative to the riser of the bow at arrow launch; (b) the deformable, force-producing components of the power units are small and light and move through only small distances (typically not more than 1.5 inches) to their rest positions; and (c) there are no buss system components contributing to the residual energy. Thus, essentially the only residual energy is that generated by rotation of the string cams, the movement of the bow string and a timing cable to their rest configurations, and the small amounts of energy generated by the restoration to their rest configurations of the force-producing power unit components. The remaining energy is transmitted to the arrow as it leaves the bow. This results in a higher initial arrow velocity with a corresponding increase in accuracy and other performance factors.  
         [0023]     Thus, a bow embodying the principles of the present invention is very efficient. Because the residual energy is low, there is little noise or vibration; and the bow is smooth, quiet, and efficient.  
         [0024]     Also, as the string cams are fixed relative to the riser in a bow as disclosed herein instead at the ends of relatively long and flexible limbs, the cams do not flail around when an arrow is released as they do in a conventional, compound bow. This further contributes to the accuracy of the bow because the bow shoots straighter and the operation of the bow remains consistent from shot to shot.  
         [0025]     A further gain in accuracy is realized by elimination of the buss system employed in a conventional compound bow. The cables of a conventional buss system pull the string cams of a bow off center, torquing or twisting the limbs to which the cams are mounted. This both reduces the accuracy of a specific shot and reduces the repeatability of a conventional bow from shot to shot.  
         [0026]     The elimination of the buss system in the bows disclosed herein essentially, if not completely, eliminates the side torque effect unavoidable in many conventional compound bows. Furthermore, any small torquing effect that might be present is negated because the cams are mounted to a bow component —the bow riser—which is rigid and does not twist like the cam-supporting limbs of a conventional compound bow do.  
         [0027]     Yet another important advantage of the present invention is realized by elimination of the buss system employed in a conventional compound bow. This system has buss cables fixed to the extreme ends of the bow; specifically, at the outermost ends of the flexible bow limbs and to buss cams which rotate with the string cams. When the bow is drawn, the buss cables place the bow&#39;s riser, especially its central, hand grip segment, under a very large load, creating a correspondingly large bending moment in the riser. The elimination of a buss cable system in the bows disclosed herein eliminates such stress, allowing the riser to be made significantly lighter than a riser of conventional construction because the only load placed on the riser is that of the bow string. At the same time, the riser is less susceptible to distortion, even if lighter; and the precision with which an arrow can be shot is correspondingly increased.  
         [0028]     The force-generating components of the power units employed herein may be attached with a simple adjusting screw mechanism which both allows the bow to be readily disassembled for string and component replacement, even in the field, and makes it equally simple to adjust the force required to draw the bow from essentially zero up to the typical maximum of 70 pounds. No bow press is needed, and the force-generating components are so small that spares can be slipped into an archer&#39;s pocket. These are significant practical advantages, especially to a bow hunter.  
         [0029]     Because they are so small and are elastically deformed to only a very limited extent, even at full draw of the bow in which they are incorporated, the force-generating components disclosed herein are highly resistant to breakage, even if the bow is dry fired or the bow string is cut in the course of loading a broadhead or other sharp arrow; and these force-generating components can be easily shrouded so that, in the unlikely event one breaks, parts which come loose will be contained instead of flying around and possibly hitting and injuring the archer. This eliminates a serious drawback of conventional compound bows which, when a limb breaks, may leave parts of the limb flying like a missile or flailing around on the bow string. The bows of the present invention are therefore safer to shoot than conventional compound bows are, and product liability is significantly less of a problem for manufacturers and sellers. Also, because they are shrouded, the power-generating components are unlikely to catch or snag on brush or other obstacles, a recurring problem experienced by hunters using conventional compound bows.  
         [0030]     Another important advantage of the novel bows disclosed herein is that an arrow release need not be used, even though the bow may be very short. In a conventional compound bow of short length, the limbs bend toward the midpoint of the bow as the bow is drawn; the string cams move closer together; and the angle between the two bow string segments on opposite sides of the nocked arrow becomes very steep, making it impossible to securely grasp the bow string with one&#39;s fingers. Also, because of this severe or sharp angle, short bows of conventional construction are twitchy and hard to shoot accurately.  
         [0031]     Because they are riser-mounted, this distance between the strings cams of the bows disclosed herein does not decrease as the bow is drawn; and the angle between bow string segments is less severe, even at full draw, allowing the string to be securely grasped without an arrow release. This feature is preferably enhanced by employing string cams eccentrically mounted off center relative to the bow riser such that the distance between the locations at which the bow string is attached to the cams significantly increases between zero and full draw. In addition, because of the eccentric mounting of the string cams, the ends of the bow string lie well above and behind the riser of the bow, creating a much more gradual angle between bow string segments than is possible in a short compound bow of conventional construction. Thus, while there may typically be only a 32 inch span between the axles of the string cams, a bow embodying the present invention will shoot like a long, 40 inch conventional compound bow because of the increasing distance between cam/string points of attachment as the bow is drawn. This makes the bow very forgiving and easy to shoot accurately.  
         [0032]     Instead of a buss system for synchronizing string cam rotation, the bows disclosed herein employ a  FIG. 8  timing cable stretched between and anchored to timing cams which rotate with the string cams of the bows. Because they are thus fixed to the riser of the bow instead of to the limbs, which move rearwardly over a considerable distance as a conventional compound bow is drawn, the imposition of significant bending moments on the bow riser and the drawbacks appurtenant to such moments is avoided.  
         [0033]     Other important objects, advantages, and features of the invention will be apparent to the reader from the foregoing and the appended claims and as the ensuing detailed description and discussion of the invention proceeds in conjunction with the accompanying drawings.  
       PRIOR ART  
       [0034]     U.S. Pat. No. 2,116,650 to Zima discloses a bow which has a “primary bow-leaf of wood . . .” Arrow propelling energy is generated by “a helical tension spring located at the middle of the bow-leaf.” 
         [0035]     U.S. Pat. No. 2,307,021 to Cordrey et al. discloses a bow with a frame  1 . Elastic tubes  15  are mounted on the frame and employed: “for propelling . . . [an] arrow” from the bow.  
         [0036]     U.S. Pat. No. 3,518,980 to Hamm discloses a bow with “an elongated bow frame member  12 .” Member  12  houses tension springs which are used to generate the energy for propelling an arrow from the bow.  
         [0037]     U.S. Pat. No. 3,595,213 to Storer discloses a bow with an elastic band  46  for generating arrow propelling energy.  
         [0038]     U.S. Pat. No. 3,744,473 to Nishioka discloses a bow with “resilient tensioning springs”  26  and  27 .  
         [0039]     U.S. Pat. No. 4,903,677 to Colley et al. discloses a bow with a “flat wound power spring . . . [ 91 ] mounted on a frame . . .” 
         [0040]     U.S. Pat. No. 4,989,577 discloses a bow with a mouse trap type spring for generating arrow propelling force.  
         [0041]     U.S. Pat. No. 5,054,463 to Colley et al. discloses a bow with “flat wound power springs”  80  and  81  ( FIG. 10 ).  
         [0042]     U.S. Pat. No. 5,638,804 to Remick et al. discloses a bow with “energy storage limbs”  86  and  87 .  
         [0043]     U.S. Pat. No. 6,698,413 discloses a bow with a “variably compressible power coil spring.” 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]      FIG. 1  is an isometric view of a compound bow constructed in accord with, and embodying, the principles of the present invention;  
         [0045]      FIG. 2  is an isometric view of one end of the  FIG. 1  bow; this figure is drawn to an enlarged scale to better show operating components of the bow;  
         [0046]      FIG. 3  is a side view of the  FIG. 1  bow; this view is partially sectioned to show power units with elastically deformable, potential energy storing components at the two, opposite ends of the bow; deformation of the power units followed by restoration of those units to their rest configurations provides kinetic energy for propelling arrows from the bow;  
         [0047]      FIG. 3A  is a fragment of  FIG. 3  drawn to an enlarged scale to better show a mechanism employed in the  FIG. 3  power unit to hold an elastically deformable component of the power unit in place and to change the pull required to draw the bow;  
         [0048]      FIG. 4  is a fragment of  FIG. 3  drawn to an enlarged scale to better illustrate one of the two, like power units employed in the  FIG. 1  bow and the relationship of the power units to other bow components; bow components are shown in their “rest” positions and configurations;  
         [0049]      FIG. 5  is a view similar to  FIG. 4  but with: (a) the bow string drawn to rotate a cam to which the illustrated end of the bow string is attached, (b) thereby shortening the effective length of a motion/force transmission power cable connected between the cam and the elastically deformable power unit component to (c) elastically deform and thereby store that potential energy which is converted to arrow propelling kinetic energy when the bow string is subsequently released;  
         [0050]      FIG. 6  is a view similar to  FIG. 4  but is taken from the opposite side of the  FIG. 1  bow to show a timing cable mechanism provided to insure that the two string cams at the opposite ends of the bow rotate in unison;  
         [0051]      FIG. 7  is a view similar to  FIG. 6 ; this view shows how elements of the timing cable mechanism move as the bow is drawn to synchronize the rotation of the two riser-mounted string cams;  
         [0052]      FIG. 8  is a side view of a timing system wheel; one such wheel is mounted at each end of the riser of the  FIG. 1  bow;  
         [0053]      FIG. 9  is a view of the  FIG. 1  bow which is oriented at a right angle to the  FIG. 1  view;  
         [0054]      FIG. 10  is a side view of a second compound bow constructed in accord with, and embodying, the principles of the present invention;  
         [0055]      FIG. 11  is a fragmentary side view of the  FIG. 10  bow with the bow components in their “rest” positions and configurations; this view is drawn to an enlarged scale and partially sectioned to show one of two power units located at opposite ends of the bow; the power units provide energy for propelling arrows from the bow;  
         [0056]      FIG. 11A  is a fragment of  FIG. 11  drawn to an enlarged scale to better show a mechanism employed in the  FIG. 11  power unit to keep an elastically deformable power unit component in place and to adjust the pull required to draw the  FIG. 10  bow;  
         [0057]      FIG. 12  is a view similar to  FIG. 11  but with: (a) the bow string drawn to rotate a riser-mounted cam to which the upper end of the bow string is attached, (b) thereby shortening the effective length of a cable connected between the string cam and the power unit to (c) elastically deform and store potential energy in the power unit;  
         [0058]      FIG. 13  is a fragmentary, partially sectioned side view of a bow constituting a third embodiment of the invention; this bow has riser-mounted timing system idlers and is shown with the bow components in their “rest” relationships and configurations; and  
         [0059]      FIG. 14  is a view like  FIG. 13  but showing the bow components in the relationships and configurations they assume when the bow is drawn.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0060]     Referring now to the drawings,  FIGS. 1 and 2  depicts a compound archery bow  20  constructed in accord with and embodying the principles of the present invention. The major components of bow  20  include an elongated, rigid riser  22 ; string cams  24  and  26  at the upper and lower ends  28  and  30  of riser  22 ; a timing system  32  (see especially  FIGS. 6-8 ), including a timing cable  34  for synchronizing the counter rotation of string cams  24  and  26  suggested by arrows  36 / 38  and  40 / 42  in  FIG. 1 ; and riser-mounted power units  44  and  46  (see especially  FIGS. 3-6 ) which store arrow propelling energy in potential form as bow  20  is drawn. A bow string  48  extends between and is connected at its opposite ends  50  and  52  to the upper and lower string cams  24  and  26 . With the components of bow  20  in their rest configurations and positions, bow string  48  lies along a straight line located to the rear of riser center section  54 . When bow  20  is fully drawn, bow string  48  is configured as shown in phantom lines in  FIG. 1  and in full lines in  FIG. 3 .  
         [0061]     The rigid riser  22  of bow  20  has an elongated configuration defined by the just-mentioned center section  54  and integral, upper and lower arms  56  and  58 , which are oriented at equal angles to, and extend rearwardly toward the archer from, the bow string side  60  of riser  22 . A hand grip  62  is formed in riser center section  54  at a location between the junctures  64  and  66  of: (a) the riser center section  54  and riser upper arm  56  and (b) center section  54  and lower riser arm  58 .  
         [0062]     Riser  22  may be skeletonized as is perhaps best shown in  FIGS. 1-3 . This desirably reduces the weight of bow  20  and gives the bow an esthetically pleasing appearance.  
         [0063]     Because riser  22  is a fairly large component, it is preferably fabricated from a material which is lightweight, strong, and rigid. At the present time, conventional carbon composites are the materials of choice. This is not intended to be limiting, however, as a variety of other materials may instead be employed. These include, without limitation, aluminum and titanium alloys, fiber-reinforced polymers, carbon-reinforced polymers, and glass-loaded polymers. Also, a combination of materials such as an aluminum alloy and a carbon composite may be employed with selected elements of the riser being made of the alloy and the rest of the riser from the carbon composite.  
         [0064]     Similarly, a variety of manufacturing techniques may be employed to fabricate the riser. In the case of a carbon composite, molding with a bladder that can be expanded to produce a hollow cavity in the may be employed.  
         [0065]     The string cams  24  and  26  at the upper and lower ends  28  and  30  of riser  22  are like components. Accordingly, only the upper cam  24  will be described in detail with the understanding that this description also applies to lower cam  26 .  
         [0066]     Upper cam  24  is mounted to the upper arm  56  of riser  22  between riser limbs  67  and  68  at the free end  69  of riser arm  56  for rotation on an axle  70  about a transverse axis  71 . Axis  71  is offset from the center of cam  24 , the cam accordingly rotating upwardly and to the rear as bow  20  is drawn (compare  FIG. 5  with  FIG. 4 ).  
         [0067]     This eccentric mounting of string cams  24  and  26  is an important feature of the present invention. In a representative bow embodying the principles of the present invention, the axle-to-axle span of the bow; i.e., the distance  72  between upper string cam axle  70  and lower string cam axle  74  is only 32 inches; and bow  20  is accordingly, and desirably, very compact. However, because the cams are mounted so far off center, they rotate upwardly and back as described above when bow  20  is drawn to the extent that the bow shoots more like a 40-inch bow when it is fully drawn; and the string angle  75  is much smaller than that of a conventional short (e.g., 32 inch) bow. As a consequence, an arrow release is not needed, the bow can be drawn with the archer&#39;s fingers; and the bow is very forgiving and easy to shoot accurately.  
         [0068]     It was pointed out above that a timing system  32  is employed to synchronize the rotation of upper and lower cams  24  and  26 : (a) as the bow is drawn and the upper and lower cams counter rotate in the arrow  36  and  38  directions, and (b) when bow string  48  is subsequently released to launch or propel a nocked arrow from the bow, the upper and lower string cams  24  and  26  counter rotating in opposite, arrow  40  and  42  directions in this part of the shooting cycle. Referring specifically to  FIGS. 6-9 , timing system  32  comprises the above-mentioned timing cable  34 ; a dual track, upper timing wheel  76 ; and a lower, also dual track timing wheel  78  ( FIG. 3 ). The details of the upper timing wheel  76  and its association with and relation to timing cable  34  are shown in detail in  FIGS. 6 and 7 ; and the ensuing discussion will be directed to the components shown in those figures with the understanding that the discussion is equally applicable to the timing wheel arrangement at the lower end of bow  20 .  
         [0069]     Focusing then on  FIGS. 6 and 7 , timing wheel  76  is mounted to upper string cam  24  and rotates with that cam in the arrow  36  direction as bow  20  is drawn and the upper segment  80  of the bow string attached at upper bow string end  50  to string cam  24  moves in the arrow  82  direction to rotate the cam. Timing wheel  76  rotates with string cam  24  in the opposite direction to its rest position when the bow string  48  is subsequently released to shoot a nocked arrow from the bow.  
         [0070]     Timing cable  34  is guided through an aperture  83  in riser arm  56  and is fashioned into the illustrated  FIG. 8  configuration so that the two runs  84  and  85  of the timing cable will move in the opposite directions indicated by arrows  86  and  87  when bow  20  is drawn, thus providing for the counter rotation of upper and lower string cams  24  and  26  in the opposite, arrow  36  and  38  directions.  
         [0071]     Timing cable runs  84  and  85  are pinned or otherwise attached in outer and inner tracks  88 - 1  and  88 - 2  of upper timing wheel  76  at the locations indicated by arrows  89  and  90  in  FIG. 8  and are similarly affixed to lower timing wheel  78 . Consequently, when bow  20  is drawn and the two cable runs  84  and  85  are displaced in the opposite, arrow  86  and  87  directions by the counter rotation of upper and lower timing wheels  24  and  26 , the two timing wheels  76  and  78  are constrained to rotation in unison, synchronizing or matching the rotation of the string cams to which the timing wheels are fixedly mounted. It is important, in this regard, that timing cable  34  be inextensible, though flexible, so that the counter rotation of string cams  24  and  26  will be precisely synchronized during the bow drawing and arrow launching parts of the shooting cycle.  
         [0072]     Absent restraint, timing cable  34  would lay along the path identified by reference character  100  in  FIG. 9  and would consequently interfere with the fitting of an arrow to the bow and with the flight of the arrow when bow string  48  is released. To avoid these problems, timing cable  34  is held to the side and away from the arrow flight path by routing it through features or fixtures  102  and  104  integrated with the center section  54  of bow riser  22  on opposite sides of hand grip  62 . As a nocked arrow lays slightly to the right of path  100  with bow  20  oriented as shown in  FIG. 9 , fixtures  102  and  104  keep timing cable  34  well away from the arrow path.  
         [0073]     It was pointed out above that the power or energy for propelling or launching an arrow from bow  20  is generated by small, lightweight, compact components of power units  44  and  46  rather than by the long, heavier, cumbersome flexible bow limbs utilized for this purpose in a conventional compound bow. Upper power unit  44  will now be described in detail with reference especially to  FIGS. 3-5  and with the understanding that the discussion is also equally applicable to the like lower power unit  46 .  
         [0074]     Power unit  44  includes a small, elongated, riser-mounted component  106  which is elastically deformed (see  FIG. 5 ) as bow  20  is drawn, storing potential energy in the component. When bow string  48  is subsequently released, component  106  restores to the rest configuration depicted in  FIG. 4 ; and the stored potential energy is converted to kinetic energy for launching or propelling a nocked arrow from the bow.  
         [0075]     Power unit  44  also includes a power cam  108  and an anchor  110 , both fixed to and rotatable with, upper string cam  24  and a power cable  112 . The power cable  112  is fixed at its opposite ends  114  and  116  to the free end  118  of elastically deformable power unit component  106  and to anchor  110 , the power cable  112  wrapping around power cam  108  as bow  20  is drawn. As this occurs (see  FIG. 5 ), upper bow string segment  80  moves in the arrow  124  direction, rotating string cam  24  in the arrow  36  direction because of the connection between the bow string  48  and the string cam  24 , The rotation of cam  24  and consequent wrapping of power cable  112  around power cam  108  moves the power cable in the arrow  126  direction, elastically bending deformable component  106  of the power unit as indicated by arrow  128  in  FIG. 5  thus, as discussed above, storing in that component potential energy which is converted to arrow propelling kinetic energy when bow string  48  is subsequently released and bow string  48 , string cam  24 , power cable  112 , and elastically deformable power-generating component  106  restore to the rest configurations depicted in  FIG. 5 .  
         [0076]     As is shown in  FIGS. 1-5 , the power-generating component  106  of power unit  44  is housed in a pocket  130  at the juncture between the upper end  131  of riser center section  54  and the lower, forward end  132  of integral riser arm  56 . Thus, the riser  22  surrounds and shrouds power unit component  106  and, in the highly unlikely event that component  106  should break, keeps parts of the component from flying around and possibly injuring the archer. Also, the shrouding of component  106  minimizes the chances of bow  20  hanging up on brush or other obstacles.  
         [0077]     As is best shown in  FIG. 5 , power cable  112  is housed over the major portion of its length in upper riser arm  56 . This further reduces the possibility that bow  20  might hang up and also makes it unlikely that power cable  112  might fly around and perhaps injure the archer if it breaks.  
         [0078]     At its lower end  136 , elastically deformable power unit component  106  is anchored to bow riser  22 . Specifically, lower component end  136  is trapped between a riser-integrated lug  138  on one side of the component and complementary, also riser-integrated, lugs  140  and  142  on the opposite side of component  106 . Component  106  is kept from slipping out of riser  22  by a screw  144  threaded through an integral riser fitting  146  in which a screw-receiving dowel  147  is installed for increased strength. The inner end (or tip)  148  of screw  144  is trapped in a dimple  150 , which is formed in a plate  152  bonded or otherwise attached to power unit component  106  ( FIG. 6A ).  
         [0079]     Also, by threading screw  144  in and out of integral fitting  146 , the biasing force exerted by power unit component  106  can be changed, allowing the pull required to draw bow  20  to be varied from near zero to the maximum for which the bow is designed (typically on the order of 70 lbs.).  
         [0080]     The elastically deformable, energy-storing components  106  of power units  44  and  46  may be fabricated from a variety of materials with carbon composites currently being preferred because of the low weight and precision-providing rigidity of such materials as well as their ability to accommodate the severe bending of the elastically deformable power unit components  106  as bow  20  is drawn. Other materials that may be employed include, but are not limited to, composites of S-glass fibers and other glassy reinforcements in epoxy, Nylon, and other polymeric matrixes; carbon reinforced polymers; metallic glasses; and alloys of aluminum and titanium.  
         [0081]     There is a variable ratio—typically from 3:1 at rest to a very high 10:1 at full draw—between the power cable track  154  of power cam  108  and the string cam track  156 . This high cam track ratio maximizes the amount of energy transmitted to the arrow and minimizes the residual energy remaining in the bow when the arrow is shot, both desirable attributes of bows embodying the principles of the present invention. These goals—a maximum transfer of energy to the arrow and low residual energy in the bow—are furthered by preloading the bow, typically to a force on the order of 200 pounds.  
         [0082]     Referring still to the drawings,  FIGS. 10 and 11  depict a second bow  180  constructed in accord with and embodying the principles of the present invention. Like components of bows  20  and  180  are identified in the drawings by the same reference characters.  
         [0083]     Bow  180  differs from the bow  20  discussed above in one respect in the character of its upper and lower, riser-mounted power units (the upper power unit is shown in  FIGS. 11 and 12  and identified by reference character  182 ). Power unit  182  has an elastically deformable, energy-storing component  184  with a curved, integral segment  186  extending from the free end  188  of the component toward the opposite, anchored, component end  190 . This configuration keeps the free end or tip  188  of component  184  perpendicular to the power cable  192  of power unit  182  as bow  180  is drawn (compare the tip/power cable relationships shown in  FIGS. 11 and 12 ). Power cable  192  is thereby kept from pulling off of component tip  188  when bow  180  is drawn. That this be done is important as the bow would cease to function if power cable  192  pulled off the tip  188  of power unit component  184 ; and, in the worst case, the bow would break.  
         [0084]     The power unit  182  of bow  180  also differs from the corresponding unit of bow  20  in the particulars of the mechanical arrangement or mechanism employed to mount power unit component  184  to the riser  194  of bow  180 . Specifically, a threaded component  196  with a head  198  extends through a washer  200  and the anchored end  190  of power unit component  184  and is threaded into an integral fitting  202  of riser  194  with the tip  204  of component  196  threaded into or through a dowel  206  ( FIG. 11A ). Dowel  206  is made of a material with the strength needed to keep the threaded component  196  from pulling out of the fitting.  
         [0085]     With bow  180  preloaded for the purposes discussed above in conjunction with bow  20 , the anchored end  190  of elastically deformable power unit component  184  is biased away from riser fitting  202  as suggested by arrow  208  in  FIG. 12 . Consequently, by advancing and backing off threaded component  196 , the pull required to draw bow  180  can be changed due to the connections between elastically deformable component  184  and bow string  48 .  
         [0086]     In addition, bow  180  differs from above-discussed bow  20  in its bow riser construction. This riser does not have the skeletonized construction of the riser  22  of bow  20 . Instead, apertures collectively identified by reference characters  210  and  212  are formed in the integral upper and lower arms  214  and  216  of the riser to reduce the weight of the bow.  
         [0087]      FIGS. 13 and 14  depict yet another compound archery bow  230  constructed in accord with, and embodying, the principles of the present invention. Like components have again been identified by the same reference characters.  
         [0088]     Bow  230  is much like the bow  180  depicted in  FIGS. 11 and 12  but differs from the latter in that timing system idlers are rotatably mounted near the upper and lower ends of the bow riser  194 . The idler mounted to upper riser end  231  is shown in  FIGS. 13 and 14  and identified by reference character  232 .  
         [0089]     Run  85  of timing cable  34  is trained around idler  232 . As bow  230  is drawn, string cam  24  rotates in the arrow  234  direction from the position shown in  FIG. 13  to the position shown in  FIG. 14 . Idler  232  increases the angle through which timing cable run  85  is wrapped around upper timing wheel  76  from approximately 200 to about 230 degrees as bow  230  is drawn. This provides the approximately 210 degrees of wrap required to ensure that timing cable  34  will not inhibit the clockwise, arrow  234  rotation of string cam  24  as bow  230  is drawn plus a significant safety margin. Adequate string cable wrap is important because interference with the rotation of string cam  24  would, of course, keep bow  230  from operating properly, if at all.  
         [0090]     The principles of the present invention may embodied in forms other than those specifically disclosed herein. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced herein.