Patent Abstract:
A bow string release has a housing encasing a battery, circuit board, mechanical linkage, and a trigger to actuate the mechanical linkage. The trigger and circuit board operatively energize an electro-mechanical device such as a solenoid, which produces linear motion. A roller terminating the solenoid engages a pivotal drive cam to convert the linear motion into rotary motion. A follower link couples the pivotal drive cam to a string hook. Proper arrangement of the linkages ensures a slight over-center biasing of the linkages to securely hold a bow string, while also ensuring that only a minimal force generated by the solenoid will be required to release the string.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. provisional patent application 61/937,418 filed Feb. 7, 2014 of like title and inventorship, the teachings and entire contents which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to mechanical guns and projectors, and more particularly to electrical trigger or releasing mechanisms designed for archery. 
     2. Description of the Related Art 
     In the field of archery, a bow has a frame or body that might, for exemplary purposes, comprise a flexible piece of wood or fiber composite. A string spans some portion of the frame. Traditional bow frames may be simple single pieces of wood that are relatively straight or slightly curved, and then bent further under the tension of a string extending generally from tip to tip. The bending of the wood provides a force opposed to the string tension. When the string is drawn, the wood flexes, with the wood acting as a simple spring. Consequently, as the string is drawn, the tension in the string increases progressively. This type of bow, which is still well known and used today, may typically require relatively great draw force. Further, holding the bow at full draw can require great strength and endurance. 
     There have been many types of bows that have been developed since the advent of the first straight bows, including recurve bows, reflex bows, decurve bows, deflex bows, and the much more recent compound bows. Likewise, there have been many materials used in the fabrication of bows over the years, including but not limited to wood, metal, laminates, and composites. These bows may be designed to have different draw forces and draw lengths. The draw force may range from only a few pounds for a small child&#39;s bow to one or even several hundred pounds for very powerful and specialty bows. 
     A common requirement among many of the bows is the need to manually grasp the bow string when drawing the string, and then to release the string to shoot the arrow. The relatively large draw forces and the relatively small diameter bow string combine to stress the relatively softer and more tender finger tips of the archer, particularly where a bow must be drawn and held for longer time periods. Archers through time have commonly employed various finger coverings such as leather to reduce the direct wear, abrasion, and disruption of circulation in their fingers. 
     Further, the release of the arrow has also been a form of art. A clean string release will allow the arrow to travel straight and true. However, if the archer slides the string sideways during release, the arrow flight may be slightly distorted, making the shot direction less predictable, reliable, and repeatable. 
     One slightly divergent technology is that of the crossbow, which addresses several of the challenges that archers may have with other bow types. One advantage of a crossbow is that there is typically some type of nut or other apparatus that is used to hold and eventually release the string. This means that the archer may hold the shot indefinitely without physical fatigue. Further, there is no abrasion to the fingers. In addition, when properly designed, a bolt, arrow, or other projectile will predictably release from the string, since the archer does not directly grasp the string. 
     Another challenge faced by archers is commonly referred to as target anxiety. This target anxiety may be manifested by an archer flinching or moving just as the string is being released, leading to inaccurate shots. Target anxiety can affect even the most highly skilled and experienced archers. 
     Over the years, a number of highly skilled artisans have devised various apparatus to effect better holding and release of the bow string. Exemplary mechanical devices, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 2,977,952 by Gabriel et al, entitled “Archery bow trigger”; U.S. Pat. No. 3,800,774 by Troncoso, entitled “Archery bow string release device”; U.S. Pat. No. 3,845,752 by Barner, entitled “Combined bowstring draw and trigger release mechanism for use in archery”; U.S. Pat. No. 4,009,703 by Cunningham, Sr., entitled “Bow string trigger release mechanism”; U.S. Pat. No. 4,672,945 by Carlton, entitled “Archery trigger release mechanism”; U.S. Pat. No. 4,881,516 by Peck, entitled “Adjustable grip and trigger bow string release”; U.S. Pat. No. 6,484,710 by Summers et al, entitled “Archery finger trigger release with cocking slide”; U.S. Pat. No. 8,402,957 by Clark, entitled “Release device for archery”; and 2013/0174820 by Jones, entitled “Archery release”. One of the significant challenges of a string release is the desire for a minimum movement by the archer, with minimal force applied, to effect the string release. While the aforementioned patents represent a significant advancement over the technology in place prior thereto, these prior art mechanical systems simply do not offer sufficiently minimal force and movement by the archer. 
     Recognizing the need for an improved string release, a few artisans have designed electrical solenoid string releases. Exemplary patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 4,674,469 by Peck, entitled “Bow string release”; U.S. Pat. No. 5,243,957 by Neilson, entitled “Archery apparatus”; U.S. Pat. No. 5,494,023 by Kolak, entitled “Bow string releasing apparatus”; and U.S. Pat. No. 5,575,269 by Harklau, entitled “Bowstring release mechanism”. Two additional patents, illustrating electrically driven releases but without a solenoid, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 6,247,467 by Siegfried, entitled “Bowstring release mechanism”; and U.S. Pat. No. 6,766,794 by Bently, entitled “Device for hands-free firing of projectile device”. 
     Many of the prior art releases have a pivoting member that is locked in place prior to release, and then allowed to rotate freely upon release. Unfortunately, with the substantial force and rapid movement of the bow string, this can and often does lead to a slapping or slamming of the pivotal member when it reaches a stop or rotary limit. Exemplary of the prior art is the Peck &#39;469 patent incorporated by reference herein above. In Peck, the sear 22 has a “j” shape, and pivots about pin 24. When plunger 26 is moved out of the way, sear 22 will rotate with violent force. Not only is this additional sound undesirable, since it can forewarn and thereby spook game, it can lead to undesirable wear and damage of the apparatus over a relatively short period. 
     Another issue is the relatively large force that is applied by the string to the release. This force will be coupled through linkages that, under load, may bind or wear excessively. Once again, the Peck &#39;469 patent incorporated by reference herein above is exemplary of the prior art. On the longer finger 20 of Peck&#39;s sear 22, the bow string will be pulling. This force is offset by a force between the shorter leg of Peck&#39;s sear 22 and plunger 26. As may be recognized, this causes significant friction between Peck&#39;s sear 22 and plunger 26, the friction making it harder to release plunger 26 and also leading to galling and wear of both Peck&#39;s sear 22 and plunger 26. Similar deficiency is found in both Harklau and Kolak. 
     Further, many of these prior art devices are not automatically resetting. Again referencing the Peck design, the archer must activate the solenoid, pivot the sear 22 into place around the spring, and then release the solenoid. This resetting sequence is an undesirable, unnecessary and challenging test of manual dexterity. Once again, similar deficiency is found in both Harklau and Kolak. 
     Neilson in FIGS. 13-15 illustrates a different type of string release, using a solenoid and cam to wedge between two pivoting arms. This causes the arms to either open when not wedged, or close when wedged by the solenoid cam. Unfortunately, the greater the draw force, the more likely the string is to accidentally release. Further, not only are manufacturing tolerances an issue, so is wear to the various components, which will worsen the ability of the device to hold a bow string. Consequently, Neilson has the potential for accidental and unintended releases that can be very dangerous in the field. 
     In addition to the foregoing patents, Webster&#39;s New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein. 
     SUMMARY OF THE INVENTION 
     In a first manifestation, the invention is a bow string release. A housing anchors a drive cam fixed pivot. A drive cam is rotatable about the drive cam fixed pivot. A linear motor is operatively actuated by a trigger. A reciprocating piston has a first end coupled with and moved by the linear motor, and a second end distal to the first end is adapted to operatively couple with the drive cam and adapted to operatively rotate the drive cam about the drive cam fixed pivot, responsive to the piston first end being moved by the linear motor. A string hook fixed pivot is also anchored to the housing. A string hook is adapted to operatively engage a bow string and transmit a draw force to the bow string. A follower link has a first floating pintle pivotally coupling adjacent a first end to the drive cam and a second floating pintle pivotally coupled adjacent a second end distal to the link first end to the string hook. The string hook is rotated about the string hook fixed pivot responsive to the piston first end being moved by the linear motor. 
     In a second manifestation, the invention is a bow string release having a housing. A string hook is adapted to operatively engage a bow string and transmit a draw force to the bow string. An electrical power source is coupled with an electrical solenoid having a reciprocating piston and an electromagnetic coil. The electrical solenoid is adapted to operatively generate reciprocating mechanical movement of the reciprocating piston when the electromagnetic coil is energized by the electrical power source. The reciprocating piston is coupled to the string hook and adapted to operatively pivot the string hook and thereby discharge a bow string therefrom. A trigger is adapted to operatively selectively connect the electrical power source with the electromagnetic coil. The reciprocating piston has a roller on a first end most nearly adjacent to the string hook, and distal to the reciprocating piston first end, a shoe bottom is adapted to engage with the housing to limit travel of the reciprocating piston towards the solenoid electromagnetic coil. 
     In a third manifestation, the invention is a method of releasing a bow string. The method includes the steps of: detecting a trigger pull representative of an intent to release the bow string; determining a firing option from the group of fire on trigger pull, fire on trigger release, and random delay; and energizing an electro-magnetic actuator operative to trigger bow string release after a time interval subsequent to trigger pull detection, the time interval adjusted based upon the firing option determination. 
     OBJECTS OF THE INVENTION 
     Exemplary embodiments of the present invention solve inadequacies of the prior art by providing a bow string release having a housing encasing a battery, circuit board, mechanical linkage, and a trigger to actuate the mechanical linkage. The mechanical linkage has a plurality of pivotal couplings that permit low-friction and smooth operation. The trigger and circuit board operatively energize an electro-mechanical device such as a solenoid, which produces linear motion. A roller terminating the solenoid engages a pivotal drive cam to convert the linear motion into rotary motion. Proper arrangement of the linkages ensures a slight over-center biasing of the linkages to securely and reliably hold a bow string, while also ensuring a minimal force to release the string. The present invention and the preferred and alternative embodiments have been developed with a number of objectives in mind. While not all of these objectives are found in every embodiment, these objectives nevertheless provide a sense of the general intent and the many possible benefits that are available from embodiments of the present invention. 
     A first object of the invention is to provide smooth, uniform, reliable, controlled and silent or very quiet string release. A second object of the invention is to provide a simple to use, easy to engage, auto-resetting, ambidextrous string release that provides both right and left-handed archers with the ability to hold a string in drawn position. Another object of the present invention is to enable an archer to hold a string without significant abrasion or disruption of circulation in the finger tips. A further object of the invention is to provide a bow string release having a release sensitivity independent of bow pull force, string characteristics and other similar variable parameters. Yet another object of the present invention is to provide an archer the option to select string release on trigger pull, string release on trigger release, or delayed string release to help reduce target panic. An additional object of the invention is to provide a small, rugged and reliable, light weight, easily carried upon a lanyard, and economical to manufacture bow string release. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, advantages, and novel features of the present invention can be understood and appreciated by reference to the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a preferred embodiment bow string release designed in accord with the teachings of the present invention from a projected view. 
         FIG. 2  illustrates the preferred embodiment bow string release of  FIG. 1  with the top portion of the clamshell housing removed to reveal inner components, and with a select few other components removed, from a projected view similar to that of  FIG. 1 . 
         FIG. 3  illustrates a first alternative embodiment bow string release similar to that of  FIG. 2  from top view and with the top portion of the clamshell housing removed, and with a select few other components removed. 
         FIG. 4  illustrates the first alternative embodiment bow string release of  FIG. 3  from a rear projected and enlarged view. 
         FIG. 5  illustrates the first alternative embodiment bow string release of  FIG. 3  from an enlarged top view, showing only the string hook, follower link, drive cam, and pivots there between. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a preferred embodiment of the invention illustrated in  FIGS. 1 and 2 , and with particular reference to  FIG. 1 , a bow string release  1  is comprised of a housing  10  that may be readily manually grasped, such as the clamshell housing  10  illustrated therein, though any suitable housing may be provided. The top and bottom portions of clamshell housing  10  are secured to each other using a plurality of socket head cap screws  18 , though any suitable fasteners, including permanent fasteners and adhesives, may be used. 
     A trigger  30  may be provided at any suitable location, though in the preferred embodiment, trigger  30  is located at a position that will be conveniently actuated by a thumb or finger. A string hook  52  will engage the bow string, while a drive cam  54  and follower link  58  will move string hook  52  from a string-retaining position as shown in the drawing figures to a string-release position and back again. Trigger  30 , which may be of any geometry or structure, is used by an archer to selectively control the movement of string hook  52 . Consequently, any apparatus that detects an intent by an archer to release the string will be understood herein to be a trigger in accord with the teachings of the present invention. 
     A lanyard connection  12  or the like is preferred. As will be understood, a bow string release such as illustrated herein may be accidentally dropped. While it may be possible to construct all of the components sufficiently to withstand a drop onto a hard surface, a lanyard will be much less expensive and generally very convenient for most archers. A lanyard connection  12  may be provided at any suitable location, and in the preferred embodiment is located at an end of bow string release  1  distal to string hook  52 . 
     A battery cap  16  will preferably provide closure about and access to a battery compartment  14  visible in  FIG. 2 .  FIG. 2  illustrates bow string release  1  with one side of clamshell housing  10  removed, but with battery cap  16  still in place. Within battery compartment  14  are a pair of battery connectors  15  that allow relatively simple battery connection and disconnection. In the preferred embodiment of  FIGS. 1 and 2 , a relatively large battery  20  is provided, though it will be understood that any suitable source of electrical energy may be used. Battery  20  may be easily accessed separately and independently from the remaining components by removal of battery cap  16 , though there is no requirement that this be the case. 
     When a person operates trigger  30 , they will do so by pivoting trigger  30  about trigger pivot  32 , which in turn applies a compressive force to micro-switch actuator  36 . Sufficient trigger rotation will actuate micro-switch  34 , producing an indication that the archer would like to initiate a string release cycle. Trigger  30  will preferably not be attached loosely, and so may be securely coupled to micro-switch actuator  36 . A secure coupling might be a direct bonding or affixing of trigger  30  to micro-switch actuator  36 . In a first alternative, the range of rotation of trigger  30  may be set such that trigger  30  cannot rotate away from micro-switch actuator  36 . In a further alternative, there may be provided a relatively soft spring biasing trigger  30  towards micro-switch  34 . In the case of a soft spring, the bias spring must be of lower force than necessary to actuate micro-switch  34 . 
     Micro-switch  34  is mounted upon and electrically coupled to circuit board  40  provided in the preferred embodiment bow string release  1 . Circuit board  40  will preferably be populated with various electronic components that enable various electrical and electronic control functions to be implemented. These components may take many forms and configurations, as is known in the electrical arts, implemented as electronic hardware, software stored on a computer readable medium and executable by a processor, or combinations of both. The various functions described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a reduced instruction set computing processor (RISC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, micro-controller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints. 
     In the preferred embodiment, an archer may select when string hook  52  will release. This is preferably achieved through an interaction between trigger  30 , circuit board  40 , and mechanical linkage  50 . A first option is to trigger release of the string from string hook  52  when trigger  30  is pulled, which corresponds with the closing of micro-switch  34 . A second option is to trigger the release of the string from string hook  52  when trigger  30  is released subsequent to being pulled. Third and fourth options are to trigger the release of the string at some delayed time interval after either the pull or alternatively the release of trigger  30 . Yet another set of options include the triggering at random time intervals subsequent to the pull or release of trigger  30 . Where an archer is simply preserving their fingers, they may opt for immediate release of the string responsive to either the pull or release of trigger  30 , depending upon their personal preference. However, where target anxiety is a factor, a delay time interval or a random delay time interval may be preferred by the archer. 
     Electrical control of the release of the string from string hook  52  occurs through a combination of a source of electrical energy such as a battery  20  located within battery compartment  14 , electrical circuitry on circuit board  40 , and an electro-mechanical device such as solenoid  62  converting the electrical energy to mechanical motion. When electrically activated, solenoid  62  will drive solenoid piston  64  forward from the solenoid toward string hook  52 . The amount of time that solenoid  62  is energized is referred to as the dwell time. In the preferred embodiment, the dwell time is adjustably controlled by the electrical circuitry on circuit board  40 , and so may be set or adjusted to accommodate the needs of particular mechanical components, bow draw force, and any other factors that might affect how much dwell time is required. For exemplary purposes, and not solely limiting the present invention thereto, the dwell time may only be a few milliseconds as will be further explained herein below. 
     After solenoid  62  has been energized, solenoid piston  64  in turn pushes on drive cam  54 , and, as may be appreciated from  FIG. 2 , drive cam  54  will rotate about drive cam fixed pivot  56 . Fixed pivot  56  is described as a fixed pintle owing to the actual anchoring or fixing into housing  10 . Drive cam  54  is coupled to follower link  58  through a floating pin  61  that permits rotation there between. Floating pin  61  is not anchored to housing  10 , and so is free to move or float relative thereto. 
     In the process of rotating, drive cam  54  will then move follower link  58  in an arc about drive cam fixed pivot  56 . This motion causes follower link  58  to pull on a floating pivot  60  that couples follower link  58  to string hook  52 , in turn causing string hook  52  to rotate about string hook fixed pivot  53 . This rotation of string hook  52  is what ultimately releases the bow string from string hook  52 . In this preferred embodiment, an arrow nocked on the bow string will be pulled and released generally in a direction parallel to the longitudinal axis of the preferred bow string release. 
     In the preferred embodiment, solenoid piston  64  is always in contact with drive cam  54 . However, the invention is not solely limited thereto. Instead, in an alternative embodiment a stop could, for exemplary purposes, be provided to limit the rotation of drive cam  54 . In this case, then the retraction of solenoid piston  64 , which can be initiated either by return spring  68  or by a return spring internal to solenoid  62 , can lead to the formation of a gap between piston roller  65  and solenoid piston  64 . A drawback of this alternative embodiment is the tendency for solenoid piston  64  to slap when driven into contact with drive cam  54 . However, slap can be mitigated through sound-dampening materials. The benefit of this alternative embodiment is the additional kinetic energy from the momentum of solenoid piston  64  that can generate a greater initial force upon drive cam  54 . 
     In the preferred embodiment, each of the four pintles, including string hook pivot  53 , drive cam fixed pivot  56 , and floating pivots  60 ,  61  create a center of rotation, which in turn defines an axis of rotation. All four axes are preferably parallel to one another, which prevents interference and binding that might otherwise occur. 
     When a bow string  51  illustrated in  FIG. 5  is pulled upon by string hook  52 , the force vector  70  of string  51  if unopposed would cause string hook  52  to rotate in a clockwise direction about string hook pivot  53  and release the string. However, with proper dimensioning, in the position illustrated in  FIG. 3  floating linkages  60 ,  61  and drive cam fixed pivot  56  are not quite in line. As best illustrated in  FIG. 5 , there is a slight “V” shape. A plane  72  contains the rotational axes of pivots  56 ,  60 . However, the axis of rotation  69  of floating pivot  61  is slightly offset from plane  72  in a direction closer to solenoid  62 . This means that force vector  70  generated upon string hook  52  by the pull upon bow string  51  will produce a force vector  71  tending floating pivot  60  towards drive cam fixed pivot  56 . Since drive cam fixed pivot  56  is fixed with respect to housing  10 , this generates an opposed force vector  73 . Any rotation of string hook  52  will then drive the axis of rotation  69  of pivot  61  to move closer to solenoid  62 , shifting in the direction of and with a force defined by force vector  74 . However, from  FIGS. 2 and 3 , it will be apparent that in the string holding position of the figures, drive cam  54  is not free to rotate. 
     In the de-energized position shown in the figures, piston  62  is fully retracted. Since solenoid piston  64  is boot shaped, the bottom of the boot simply presses against features formed in housing  10  as best viewed in  FIG. 2 . Since solenoid  62  is fully retracted and housing  10  prevents solenoid piston  64  from moving, solenoid piston  64  will generate an equal and opposite force vector to oppose force vector  74 . This creates a static and strong holding force, to securely hold the bow string  51 , even with extremely high draw forces. Consequently, as long as follower link  58 , drive cam  54 , solenoid piston  64 , and housing  10  are all sufficiently durable, then a bow string release designed in accord with the teachings of the invention can be used to draw against an enormous draw force. While a boot shape is illustrated for solenoid piston  64 , it will be understood that any geometry which will engage and stop at an appropriate feature in housing  10  is suitable. For exemplary purposes, and not solely limiting the invention thereto, a bell-shaped solenoid piston or other similar flared geometry would readily be substituted for boot shaped solenoid piston  64 . 
     As understood from the foregoing, there is no electrical energy or spring force required to hold string hook  52  in the string pull position illustrated in the Figures. As long as the angle between a first line segment from the center of pivot  56  to the center of pivot  61  is offset from parallel with a second line segment from the center of pivot  60  to the center of pivot  61 , and shifted so that the center of pivot  61  is slightly closer to solenoid  62  than a line from the center of pivot  56  to the center of pivot  60 , then the draw force alone will hold string hook  52  in place. 
     When solenoid  62  is fired, it must drive axis of rotation  69  across plane  72  and closer to bow string  51 . Once axis of rotation  69  crosses plane  72 , then string hook  52  may rotate in a clockwise direction, essentially unopposed, for a very rapid release. The only restriction on the speed of rotation is a low-force return spring  66  shown in  FIG. 3 , and it is return spring  66  that will then automatically reset string hook  52  to the position of the Figures, once string  51  is released. 
     Consequently, solenoid  62  pushing piston roller  65  against drive cam roller face  57  must generate a force great enough to overcome force vector  74 . Noteworthy here is that the closer axis of rotation  69  is to plane  72 , the smaller force vector  74  will be. In other words, and again only for exemplary purposes, if axis of rotation  69  were exactly within plane  72 , then all of the force opposing string hook  53  rotation will come entirely from drive cam fixed pivot  56  through force vector  73 . Only in this exact case where axis of rotation  69  is exactly within plane  72 , then force vector  74  is zero, meaning there is no additional force pushing back against solenoid  62 . Even when axis of rotation  69  is close to plane  72 , then force vector  74  will be near zero. This is important, because the amount of force required of solenoid  62  to release the bow string  51  is primarily determined by the magnitude of force vector  74 . In other words, solenoid  62  can be much smaller and will draw less power if axis of rotation  69  can be kept close to plane  72 . In such case, then not only is less force required, but the amount of time that solenoid  62  needs energized, referred to herein above as dwell time, is also very small. The benefit of a smaller solenoid  62  is obvious in size, weight, and cost. Not only can solenoid  62  be smaller, but the shorter dwell time also allows battery  20  to be much smaller while still providing good battery life. 
     At the time of design of the bow string release, the precise length of follower link  58  and the exact dimensions of drive cam  54  and string hook  52  will be determined. Furthermore, the tolerances and any play within the floating pivots  60 ,  61  and at the drive cam fixed pivot  56  and string hook pivot  53  will be determined. Those skilled in the arts of physics and engineering can then determine how much offset between axis of rotation  69  and plane  72  is required to ensure a safe and secure holding of bow string  51 . In other words, in the hypothetical example above where axis of rotation  69  is within plane  72 , a small jolt could lead to an accidental release. By providing a small force  74 , accidental releases are easily prevented. Then those same persons skilled in the art of physics and engineering can easily calculate the magnitude of this force  74  for a given force vector  70 , and so an appropriate solenoid  62  and battery  20  may be selected based upon the known dimensions and manufacturing tolerances. 
     With reasonably sturdy construction, there is no practical limit to the draw force that the invention may be used with. Instead, the limiting factor will normally be the force required to be generated by the solenoid to push axis of rotation  69  across plane  72 . In order to push axis of rotation  69  across plane  72 , there will be a slight counterclockwise rotation of string hook  52  just prior to string release. 
     As noted above, manufacturing tolerances will directly affect the strength of solenoid required. This is because the return spring will ideally lock string hook reliably and repeatedly into the position shown in the Figures. Any loose fittings or dimensional deviations will increase the amount that axis of rotation  69  must be shifted form plane  72  and still work reliably. As outlined above, the greater the shift of axis of rotation  69  from plane  72 , the more powerful a solenoid that is also required. 
     A significant feature of each of the embodiments of the present invention is that the string hook  52  self-resets. In other words, in the preferred and first alternative embodiment bow string releases  1 ,  2  of  FIGS. 1-4 , one or more additional return springs such as return spring  66  and solenoid piston return spring  68  may be provided, such as illustrated in  FIG. 3 . This is necessary because solenoid piston  64  is not affixed to the remaining linkage, and instead uses piston roller  65  to provide smooth, substantially reduced friction connection between piston roller  65  and drive cam  54 . Return spring  66  is anchored at a first end to return spring fixed anchor pin  67  that is rigidly affixed into housing  10 . A second distal end of return spring  66  is coupled to return spring anchor pin  55 , which is rigidly affixed into drive cam  54 . The arrangement of drive cam  54 , drive cam roller face  57 , anchor pin  55 , solenoid piston  64 , piston roller  65 , and fixed anchor pin  67  is best illustrated in  FIG. 4 , which has been illustrated without return springs  66  and  68  to enable better viewing. Piston roller  65  rolls against the slightly curved drive cam roller face  57 , while a slot adjacent thereto in drive cam  54  enables return spring  66  to engage with anchor pin  55 . 
     In one alternative embodiment, solenoid piston  64  may be coupled through a floating pivot such as a pin or the like to drive cam  54 . In this alternative embodiment, a return spring which is commonly a part of an electrical solenoid will pull the solenoid piston  64  back into solenoid  62  when solenoid  62  is de-energized. Return of solenoid piston  64  will reset string hook  52  to the position such as illustrated in  FIG. 1 , ready to be easily hooked onto a bow string and used again to draw and release the bow string. 
     Solenoid piston  64  may be constructed as a single integral component, typically having a cylindrical portion within the body of solenoid  62 , or may be fabricated from several discrete components that are coupled together, such as in the embodiments of  FIGS. 1-4 . One or more piston guide pins  63  may be provided, and if so, corresponding slots are formed in solenoid piston  64  to permit solenoid piston  64  to reciprocate towards and away from drive cam  54 . 
     String hook  52  rotates about string hook pivot  53 , and when moving from the string retaining position of  FIG. 3 , will rotate in a clockwise direction about string hook pivot  53  to release an archery string. Bow string release  2  illustrated in  FIGS. 3 and 4  is similar to bow string release  1  of  FIGS. 1 and 2 , and has a similar micro-switch  34 , trigger pivot  32 , circuit board  40 , solenoid  62 , solenoid piston  64 , drive cam  54 , follower link  58 , and string hook  52 . The battery  20  and housing  10  have been changed slightly, and trigger  30  is not separately illustrated. However, the string travel vector, which corresponds to the arrow travel, matches force vector  70  of  FIG. 5  and is approximately in line with the longitudinal axis of first alternative embodiment bow string release  2 , and operation is very similar to that of preferred embodiment bow string release  1 . Nevertheless, other variants are also contemplated herein, such as a string travel vector and associated arrow travel perpendicular to the longitudinal axis of the bow string release. 
     From the foregoing figures and description, several additional features and options become more apparent. First of all, a bow string release designed in accord with the teachings of the present invention may be manufactured from a variety of materials, including metals, resins and plastics, ceramics or cementitious materials, or even combinations, laminates or composites of the above. The specific material used may vary as will be determined by a designer at design time. In addition, where electrical components are illustrated and preferred, it is further contemplated herein that mechanical components may be substituted therefor. One such component that is contemplated herein is the solenoid, which is contemplated as being replaced with a mechanical energy storage device, such as a spring and sear that permits a plunger to be manually drawn back and then held in place by the sear. Upon release of the sear, the plunger may then be propelled forward by the energy stored in the spring, to drive the cams and follower links, to in turn pivot the string hook about. Likewise, while a single string hook is illustrated and preferred, which permits rapid attachment to a bow string simply by hooking the string, other apparatus may be substituted therefor, such as a set of scissors-motion jaws or other apparatus. 
     While the foregoing details what is felt to be the preferred embodiment of the invention, no material limitations to the scope of the claimed invention are intended. Further, features and design alternatives that would be obvious to one of ordinary skill in the art are considered to be incorporated herein. The scope of the invention is set forth and particularly described in the claims herein below.

Technology Classification (CPC): 5