Abstract:
A ski binding heel employs a low-mass, spring-loaded interface between the heel and/or toe release mechanisms of the heel and or toe pieces of the binding and the ski boot, i.e., fast-response heel and toe cups. The low mass or lightweight fast-response heel and toe cup interfaces follows the dynamics of the ski to retain the boot during events that could cause inadvertent release (IR) in a conventional release binding. A biased, or spring loaded member engages, the boot heel/toe for mitigating loads and for absorbing sub-injury loads and compensating for movement between the boot and ski. The spring loaded members are biased toward the boot heel and toe for absorbing loads and compensating for displacements that might otherwise result in an inadvertent release. The spring loaded toe/heel cups permit movements of the boot relative to the ski flexing and counter flexing that might have otherwise resulted in an IR

Description:
RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent App. No. 61/914,577, filed Dec. 11, 2013, entitled “SKI BINDING HEEL,” incorporated by reference in entirety. 
     
    
     BACKGROUND 
       [0002]    Conventional ski bindings prevent ski injuries by releasing the skier&#39;s leg from relatively stiff communication with the ski when forces deemed to be injurious are applied to the ski, as in a ski fall. Early ski bindings held the ski boot, and thus the leg and ankle of the skier, in firm communication. It was soon realized that the twisting loads that the ski can apply to a falling and tumbling or rolling skier can be substantial. So called “safety bindings,” which maintain communication, i.e., transmit loads, between boot and ski only up to a predetermined threshold force, and are intended to release the ski before a lower-extremity equipment-related (LEER) injury occurs, have been the norm for more than forty years. 
         [0003]    Modern ski bindings have a heel and toe pieces for retaining corresponding portions of a ski boot (boot), typically in spring loaded cam devices with toe and heel cups adapted to engage a protrusion on the boot heel and toe. The spring loaded cam systems allow the toe and heel cups to rotate and release the boot to prevent the transmission of potentially injurious loads to the skier. Typically, rotation of the ski boot out of alignment with the toe of the ski occurs from pivoting or rotating movement of the cups on the binding toe or heel pieces. The toe and heel pieces are set to retain the boot in engagement with the ski, typically by preloading the release spring in a spring-cam biased retention system. When certain bending, twisting or rotation loads exceeding certain predetermined loads occur, the binding heel piece allows the heel cup to rotate up, and on some bindings laterally as well, or the binding toe piece allows the toe cup to pivot right or left, and on some designs up as well, to allow the boot to release from the ski and binding, typically from a downed skier rolling or tumbling across the snow surface. The threshold release loads for the toe and heel pieces, however, need to be identified, adjusted and calibrated in an adjustment window order to prevent injuries from loads that do approach the injury thresholds and to prevent inadvertent releases from skiing maneuvers, such as recoveries, that might produce loads that are larger than usual but still do not approach the potentially injurious, or harmful, loads. 
       SUMMARY 
       [0004]    Many ski bindings transmit loads from the skier&#39;s leg to the ski by engaging a pair of bindings fixed to the skis at the heel and toe of the ski boots worn by the skier. The ski bindings therefore operate as an interface between the skier and the ski for transmitting loads to control the ski. Many ski bindings also maintain a spring biased release mechanism to disengage the boot from the ski by one of two strategies: if loads either approach an injury threshold deemed to be approaching those which would be potentially harmful to the skier&#39;s lower extremity or if they exceed the highest loads required for skiing still below those approaching injury, which might typically be generated in a sudden stop or turn or in some kind of dynamic recovery maneuver. Usually the release threshold is met during a fall or failed recovery maneuver, when a rolling or tumbling movement of the skier causes the ski to transmit forces approaching a potentially harmful magnitude to the skier. 
         [0005]    Configurations herein are based, in part, on the observation that ski bindings implement a release designed to disengage the boot, and thus the skier, from attachment to the ski to prevent transmission of potentially injurious loads during a fall, or an overly aggressive maneuver, when the loads transmitted through the ski approach a magnitude that could potentially cause injury. 
         [0006]    Unfortunately, conventional approaches to ski binding release mechanisms suffer from the shortcoming that conventional release mechanisms employ a release system which disengages the boot not only upon an application of loads deemed to be approaching those that could be potentially injurious, but also responsive to forces that mimic harmful scenarios to result in an inadvertent release. This can occur under certain dynamic situations when the ski is flexing and counter flexing, or when the binding does not have enough displacement to adsorb certain loads or shocks. In the latter case loads or shocks can be absorbed by work done on the boot binding system. This can be evident by displacement of the boot relative to the ski under load. The combined load and displacement represent energy adsorbing work done on the binding. This energy adsorbing displacement of the boot and binding relative to the ski can occur without risking LEER injuries in an appropriately designed and functioning ski-boot-binding system. Devices which extend the displacement in the system before release of the boot by the binding, without dangerously increasing the loads on the leg, will provide superior binding performance though reducing the risk of inadvertent release while not increasing the risk of injury. 
         [0007]    Conventional approaches to testing release functions are usually based on quasi-static loads applied to the boot, and are calibrated based on a boot engaged in bindings on a stationary ski, recording only the peak loads, with no simultaneous measure of displacement of the boot relative to the binding. Conventional approaches to testing do not measure the work to release nor do they anticipate or address dynamic loads and shocks encountered during skiing and the flexing and counter flexing of a ski in use. Therefore they cannot detect if a binding might be especially susceptible to inadvertent release or particularly good at avoiding it. 
         [0008]    The only way most skiers currently think that they might avoid inadvertent release is to increase the DIN or visual indicator settings that indicate the preloads on the larger springs in the bindings that control release, thereby increasing the loads prior to release and reducing or eliminating the margin where the release should be set between release loads and injury loads. Increasing the settings for the release loads puts the skier at greater risk of a lower extremity equipment related (LEER) injuries. 
         [0009]    Conventional bindings typically have relatively heavy springs in the spring-cam system that control the release loads. These springs compress against cams to allow the toe cup and heel cups, which provide the interface between the binding and the boot, to rotate, or pivot, to release the boot. The toe cup rotates laterally and in some cases vertically as well. The heel cup rotates vertically and in some cases laterally as well. The preload on these springs, which control the release, can be adjusted to account for the individual skier, usually by a system that can include the skier&#39;s weight, height, boot sole length, age and skiing style. 
         [0010]    Conventional bindings also have a relatively light spring that pushes the heel piece forward on a track in order to capture the boot between the toe and heel piece firmly, or snuggly, to avoid perceptible motion between the boot and binding under loads lighter than those where motion for release is initiating. This spring, often referred to as the forward-pressure spring, needs to be partly compressed when the boot is inserted in the binding. This need for compression limits the stiffness of the forward-pressure spring. If the forward pressure is too stiff it could be difficult or impossible to put the ski on, especially in soft snow. The forward-pressure spring is further compressed when the ski flexes. And the forward-pressure spring should push the heel piece forward to retain the boot, so that the heel cup remains engaged with the boot heel and the boot is thereby retained, when the ski un-flexes and counter-flexes and there is no risk of injury. However due to the weight of the heel piece, resistance to motion on the heel track and the requirement that the forward-pressure spring cannot be too stiff, the response of the heel piece can be too slow relative to the flexing, un-flexing and counter flexing of the ski and inadvertent releases occur in these situations. 
         [0011]    Accordingly, configurations herein substantially overcome the above described shortcoming of susceptibility to inadvertent release (IR) by disposing the fast-response toe and heel cups which are slideably mounted and spring-loaded. These fast-response toe and heel cups are spring biased components with relatively small masses that provide a fast-response shock-absorbing interface between the relatively large primary mass of the main heel and toe pieces of the binding and the boot that is robust with respect to the accommodating flexing of the ski and other loading and displacements which could cause inadvertent release. The main heel and toe pieces house the relatively heavy springs and cams that provide the normal, controlled and intentional release, and the boot. The fast-response toe and heel cups, being lighter, have a faster response for the same stiffness springs, than does the heavier entire binding with the conventional, intentional release mechanism. A binding with the fast-response heel and/or toe cups is therefore better adapted for the dynamic loads experienced during recovery maneuvers turning or stopping, particularly on firm snow or ice. 
         [0012]    Configurations herein dispose fast-response toe and heel cups comprising interfaces with the toe and heel of the boots slideably attached with the main-heel and main-toe pieces which are the primary masses of the ski binding. The fast-response toe and heel cups have a lighter mass and has a higher response frequency for the same stiffness forward pressure spring than does the current heel piece, thus it responds more quickly than the conventional binding alone. The fast-response heel and toe cups are biased by a spring or other resilient elastic compression member, and the lower mass so that even with the same spring stiffness as the current forward pressure springs they results in a combination that better maintains communication for retaining the boot in situations that might result inadvertent release (IR) in current bindings. The toe and/or heel cups also faithfully transmit control loads between the skier and ski through the binding and the boot required for executing maneuvers. 
         [0013]    It should be noted herein that the ski binding pieces (toe and heel) and the toe and heel cup, are often referred to as “tensioned” to address the force holding them against the boot by a spring. While, strictly speaking, this may be described as a compression force, as the biasing results from a compressed spring, the tension so described refers to this bias, as the binding and toe/heel cups themselves cannot really be “compressed.” 
         [0014]    In particular configurations discussed below, these fast-response heel and toe cups secure a ski boot to the main heel and toe pieces, and include binding boot-heel and boot-toe receptacles, adapted to engage a heel and toe of a ski boot for transmitting control loads and are shaped so as to not to interfere with displacement during release. In this manner, the main bodies of the toe and heel pieces of the binding are mounted on a ski and have attached to them fast-response heel and toe cups, which are slideably mounted on main bodies of the heel and toe pieces. In a particular configuration, the fast-response heel and toe cups are disposed between the main bodies of the heel and toe pieces and the boot heel and toe and biased by compression springs against the heel and toe of the boot. The mass of the fast-response heel and toe cups is less than the mass of the entire heel piece for allowing faster dynamic responses. 
         [0015]    The fast-response heel and toe cups, in the example arrangement, take the form of spring loaded members, which are responsive to loads exerted by the boot heel against the binding heel piece, and by the boot toe against the toe piece, such that the system permits movement of the spring loaded member relative to the main portions of the toe and heel piece. The spring loaded member, depicted herein as a toe or heel cup, has an engaging surface for engaging the boot heel and is slideably attached through rods to compresses a spring on an opposed side for attachment to the main bodies of the heel and toe pieces of the binding, and the spring or other compressible component or system (e.g., pneumatic, hydraulic or electro-magnetic) is attached between the binding heelpiece or toepiece and the spring loaded member. Alternately or additionally, the spring loaded members could pivot or slide on an arc with the boot heel or toe on an appropriate axis (e.g., parallel to the main rotational axis for release) to retain the boot heel or toe through greater movement prior to release. By spring loaded pivoting or sliding on an arc to counter the release pivot, by straight or curved extension of the heel or toe cups, the system would thereby increase the displacement of the boot relative to the ski before release, and the therefore energy that can adsorbed by the binding, without increasing the loads on the skier to those that might cause injury with a stiffer coupling or higher release setting, and adsorbing energy that might otherwise cause injury or result in a release. 
         [0016]    It is not necessary to have these moveable heel cups, which are described above, on both the toe and heel to receive some of the benefits described above. The redundancy on the toe and heel could help in situations where the boot for any reason remains biased toward either the toe or heel piece during flexing, unflexing and counter flexing of the ski so that the boot would escape in a situation where there is no risk of injury. 
         [0017]    In addition by adsorbing energy by displacement and loads below those that could potentially cause injury the ski can remain attached, without putting the skier in danger of injury, in situations where it would otherwise have had to release had the coupling been stiffer, i.e, less compliant, as the potentially injurious loads are approached. This sock adsorbing function serves to limit loads seen by the skier without releasing the boot from the binding. 
         [0018]    Additional configurations include a guide pin or pins and guide pin receptacle(s), in which the guide pin extends from the spring loaded member for engaging the guide pin receptacle in the binding heel or toe, and the movement is restricted to be along an axis, possible curved, of the guide pins for limiting lateral movement away from the guide pin axis. The pins can have a verity of cross sections including round or rectangular or oval. 
         [0019]    Alternative configurations can also include sliding shells with appropriate bevels or rubbery, possibly accordion-like, covers that cover the gap between the main bodies of the heel and toe pieces and the movable extensions of the fast-response toe and heel cups. This arrangement would serve to keep snow and ice and dirt out of the mechanisms and interfaces and prevent pinching of fingers in the interfaces. 
         [0020]    In an alternate configuration, by controlling the pressure required to hold the boot firmly and snuggly between the fast-response toe and heel piece, with springs or other pressure means in the toe and heel cups, the track and spring under the heel piece can be eliminated. This reduces the weight and allows this space to be eliminated or used for adsorbing vertical loads with a spring system perhaps preloaded to prevent significant motion during normal loading, that could respond and protecting the ACL from boot induced anterior (BIAD) loads or allow the heel piece and boot heel to be lowered relative ski, or allow for lowering of the entire boot relative to the ski. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The foregoing and other objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0022]      FIG. 1  is a graph of load-displacement in a conventional ski binding depicting the normal control, release and injury thresholds; 
           [0023]      FIG. 2  shows a distribution of energy/work in a binding as in  FIG. 1  pending a release; 
           [0024]      FIG. 3  shows the energy and work for initiating a binding release according to  FIG. 2 ; 
           [0025]      FIG. 4  shows boot heel retention in a conventional prior art binding; 
           [0026]      FIGS. 5   a - 5   e  show oscillating movement, or chatter, leading to inadvertent release (IR); 
           [0027]      FIGS. 6   a - 6   c  show flexing of a ski resulting in IR; 
           [0028]      FIG. 7  shows a binding according to configurations herein; 
           [0029]      FIG. 8  shows an alternate configuration of a binding according to configurations herein; 
           [0030]      FIG. 9  shows a unitary pivot configuration in the binding of  FIG. 8 ; 
           [0031]      FIG. 10  shows a complementary toe binding corresponding to a heel binding as in  FIGS. 8 and 9 ; 
           [0032]      FIG. 11  shows a dual pivot configuration in the binding of  FIG. 8 ; and 
           [0033]      FIG. 12  shows an alternate configuration employing similar protections for both the heel and toe bindings. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Generally, ski bindings are installed in a heel and toe pair, each with separate but corresponding preloads in a spring-cam system defined to retain the skier for ordinary skiing and recovery maneuvers below the injury threshold. The preloads are commonly indicated on the housing of the binding and referred to as visual indicator or DIN settings. Toe pieces pivot sideways or have a toe cup that pivots side ways around an approximately vertical axis approximately normal to the plane of the ski, and disengage the boot toe sideways. In some cases the toe piece or toe cup can also pivot upwards. Heel pieces, in conventional approaches, release by pivoting upwards or have a heel cup which pivots upward about an axis parallel to the plane of the ski and perpendicular to the length, such that the boot heel exits upwards. In both cases, skiing maneuvers generate loads that operate against the biasing force holding the boot engaged in the binding, and displace to release the boot once the threshold force is reached. 
         [0035]    The toe and heel piece could have two or more movable fast-response toe and heel cup systems to convert release motions in different directions, thus retaining the boot through greater release rotation of the heel and toe cups and delay release, by increasing the displacement for retention prior to release, allowing for more energy to be adsorbed by the binding before release and improving retention without increasing the loads on the leg to potentially injurious levels when the systems, including preloads on the springs, are adjusted properly. The fast-response heel and toe cups, can thereby mitigate the loads that would otherwise have caused injury or release. Alternatively, or in addition, the fast-response elements could be included on boot toe and heel extensions that engage the binding. 
         [0036]    The geometry of the heel cup facing the boot should be such that the upper ledge of the boot toe and heel are appropriately engaged through the sliding and release movements of the binding system and the lower portion of the boot toe and heel are generally not contacted during the movements intended to provide retention. The heel cup could have the conventional treadle that would normally be engaged by the sole of the boot heel to enter the binding. 
         [0037]    Conventional ski bindings, however, employ a single, forward pressure spring system, which can be loaded dynamically through the movement of the mass defined by the weight of the heel piece of the binding and in any case acts through the heel piece pushing forward towards the toe piece, at the heel, in order to hold the boot firmly and snuggly in the toe and heel cups. The release threshold is represented by the compression of the larger springs in the main bodies of the toe and heel pieces, and these preloads are set to release the boot below injury thresholds, representing transmitted loads of a magnitude approaching those sufficient to potentially cause injury. The release thresholds, however, are tested by quasi-static loads, torques or forces, applied to the ski binding, and most tests do not encompass dynamic loads experienced during skiing. These dynamic loads can cause inadvertent release of the bindings even when a skier is not out of control, or is able to recover control or is not experiencing a fall or exigent circumstances which could lead to LEER injuries. Such inadvertent releases (IR) can also cause injury by the resulting fall from the loss of control because of the disengaged ski, which can result in the skier going off the trail and/or into a stationary object such as a tree or structure, or falling off a steep grade or ledge, or colliding with another person. 
         [0038]    IR situations may occur during high speed, aggressive maneuvers such as those in competitive skiing, but can also occur in less intense contexts. Studies have shown that the incidence of IR affects a significant portion of competitive skiers, and may also be difficult to track because it can be difficult to determine if the binding release caused the fall or vice-versa and there is no system for reporting and tracking IR. 
         [0039]    In particular, one scenario that can be prone to cause IR events is a rapid cyclic flexing or oscillation of the ski that may occur during high speed turns, particularly on hard snow or ice, colloquially known as “chatter.” A chatter situation causes the ski to rapidly flex and counter flex between concave and convex positions, and is most notable during slow motion views of competitive skiing. When chatter occurs, the straight-line distance between the attachment points of the heel and toe piece of the bindings vary as the ski flexes. Since the bindings attach to the boots slightly above the plane of the ski, a convex arc tends to draw the heel and toe bindings outward, while a concave arcing pulls them together. A high speed oscillation of the ski may occur faster than the spring loaded binding can respond, and cause the boot to disengage as the attachment point of the binding is drawn out of communication with the heel piece or toe piece and disengages. 
         [0040]    Static testing cannot address chatter situations because the ski remains unflexed, and conventional ski binding tensioning (or release/retention setting, commonly referred to as a “DIN” setting) is applied to a stationary ski. Dynamic loads such as chatter are assumed to be compensated by the fairly rigid arrangement of the ski binding mass and spring biased loading, however. Inadvertent release in chatter situations can result because the ski has a higher natural frequency than the binding, and the spring and mass of the binding cannot respond quickly enough to prevent an IR, causing the ski and boot to disengage and resulting in the fall and possible injury that the binding was expected to prevent. 
         [0041]      FIG. 1  is a graph of load-displacement in a conventional ski binding depicting the normal control loads, release loads and injury thresholds. Referring to  FIG. 1 , a load axis  10  indicates forces against the binding tending to cause release, such as from a skier executing a turn at high speed. A displacement axis  12  corresponds to movement of the binding until release. A control load limit  14  approximates forces within normal controlled skiing, and an injury threshold  16  defines a force injurious to the skier, and prior to which the binding should disengage the ski. During ski maneuvers, force applied against the binding follow the line  20  as the binding begins to displace. At point  22 , after the control threshold, displacement occurs more rapidly along line  24 , until displacement is sufficient to disengage the boot from the ski, as line  24  crosses a disengagement threshold  26 , prior to the injury threshold  16 . The intersection  28  occurs when the work performed is sufficient to displace the binding to the point of disengagement with the boot. The area under the curve  18  defines the work to trigger release, as computed by a skiing load force exerted on the binding through a distance for displacing the binding sufficient to release. In a modern ski binding, which may have a relatively small protrusion to secure a boot into engagement with a heel receptacle on the binding, the displacement required to disengage is small, increasing the frequency for IR. 
         [0042]      FIG. 2  shows a distribution of energy in a binding as in  FIG. 1  pending a release. The curve  30  shows the energy available to do work on the binding; in other words, the acting forces which displace the binding through a distance until release. As will be discussed further below, a release threshold  32  denotes release. As the release threshold  32  increases, meaning that increased energy is required to trigger a release, the probability of inadvertent release decreases, as shown by the area  34 . Small increases in the work required to cause a release have a large impact on reducing an IR situation. 
         [0043]      FIG. 3  shows the energy and work for initiating a binding release according to  FIG. 2 . Since the release threshold  26  is more properly defined as a force through a distance (i.e. work), rather than simply a threshold force, the IR protection as defined herein characterizes binding release as a quantity of work to release. Referring to  FIGS. 1-3 , the area  18 ′ represents additional work required (such as binding movement due to chatter) until binding release, depicted by improved release threshold  26 ′. In other words, as chatter and similar, relatively minor forces displace the binding, an IR is avoided as these forces are absorbed by the secondary mass and pressure springs in the toe and heel cups, rather than combining at an inopportune time to complete the relatively small quantity of work  18  triggering release, depicted in  FIG. 1 . 
         [0044]      FIG. 4  shows boot heel retention in a conventional prior art binding  50 . Referring to  FIG. 4 , the binding  50  includes a heelpiece  52  defining a mass  54  and a mounting  56 . The mounting  56  slideably engages a track  58  biased by a spring  59 , and the track  58  attaches the binding  50  to a ski  60 , typically by bolts, screws, or other fixed attachment. The spring  59  biased binding  50  applies force forward towards a boot  70 , engaged between upper and lower protrusions  72 - 1  . . .  72 - 2  ( 72  generally), as shown by arrow  62 . A pivot  64  allows angular displacement of the heelpiece  52  from the mounting  56 , and is also biased by the spring  59 . Alternatively, a separate spring may bias the heelpiece  52 . Upon a release event, the heelpiece  52  displaces upward, around pivot  64 , as shown by arrow  66 . IR occurs, in part, because the boot  70  displaces according to an opposite rotation, centered at the toe, as shown by arrow  68 . IR potential is exacerbated because protrusions  72  are often undersized and permit boot  70  release after only a small angular travel  74 . 
         [0045]      FIGS. 5   a - 5   e  show oscillating movement, or chatter, leading to inadvertent release (IR).  FIG. 5   a  shows a skier  100  navigating a turn. As the skier cuts into the turn, the ski  60  flexes upward, defining a concave deformation of the ski  60 . The boot  70  remains engaged in the binding as the ski  60  flexes oppositely, shown by the convex arc in  FIG. 5   b . In  FIG. 5   c , the ski  60  flexes back to the convex deformation, and back to concave in  FIG. 5   d . At  FIG. 5   e , the flexing of the ski  60  displaces the binding  50  away from the ski due to chatter, and the ski detaches in an IR situation as the spring biased binding cannot recover quickly enough to the convex arc of the ski  60 . 
         [0046]      FIGS. 6   a - 6   c  show a side view flexing of a ski resulting in IR, as depicted in  FIGS. 5   a - 5   e . In  FIG. 6   a , the ski  60  remains at rest as the boot  70 , engaged between a heel (rear) binding  50 - 1  and toe (front)  50 - 2  binding ( 50  generally). As the ski  60 ′ flexes in a concave manner, a distance  80  between the bindings  50  shortens as the deformation draws the bindings  50  together. As the ski deforms oppositely to a convex shape  60 ″, the bindings  50  are drawn apart and the linear distance  82  increases to the point where the bindings  50  cannot engage the boot  70 , resulting in an IR. 
         [0047]      FIG. 7  shows a binding according to configurations herein. Referring to  FIG. 7 , the ski binding  150  as disclosed herein includes a heelpiece  152  pivotally attached to a mounting  156  at a pivot  164 . The mounting  156  defines a mass  154 , which may be spring  159  biased via a track  158  to the ski  60  or may optionally be mounted directly to the ski  60 . 
         [0048]    Configurations herein dispose fast-response heel and toe cups (a secondary mass) between the main body of the binding (primary mass) and the ski boot  70 , for enabling a biased (spring loaded or similar) response to high frequency loads and other loads which tend to induce IR. Accordingly, discussed further below is a ski boot attachment interface for engaging a ski boot  70  to a ski  60 , including one or more tensioned masses disposed between a ski boot and a mounting on a ski, such that each of the masses is biased against the ski boot  70 . The tensioned masses further include the primary mass  154  biased against the ski boot for securing the boot to the ski against a threshold force indicative of injury, and a secondary mass defined by a heel cup  210  (secondary mass) disposed between the primary mass  154  and the ski boot  70  and biased to exert a different force than the primary mass  154 , such that the secondary mass  210  engages the ski boot  70  for absorbing a load less than the threshold force for preventing inadvertent release (IR). The threshold force defines a displacement of the primary mass  154  sufficient to release the ski boot  70  from the engagement with the ski  60 , and the secondary mass  210  is configured for displacement at a lesser force than the threshold force for absorbing displacement corresponding to an IR without disengaging the ski boot  70  from the ski  60 . In the example configuration, the secondary mass  210  is configured to absorb a load for increasing work required for triggering a release by disposing the primary mass against a threshold force indicative of injury, as depicted in the graphs above. 
         [0049]    In an alternate configuration, to provide the so-called forward pressure to hold the boot firmly, or snuggly, between the toe and heel pieces, particular configurations may employ only the fast-response heel and/or toe cups, in lieu the forward pressure spring forcing the main-housing of the heel piece forward in a track. In such an embodiment, the main-toe-piece and main-heel-piece can remain in a fixed position mounted on the ski. The fast-response heel and/or toe cups simply respond(s) according to the higher natural frequency of their smaller masses for addressing elastic deformations of the ski caused by chatter and other dynamic loads. Such a configuration also allows the main-heel piece to be mounted closer to the ski since the track and forward pressure spring mechanics are not needed. In this configuration, a fixed heel piece defines the primary mass, and the secondary mass is defined by a fast-response-heel or toe cup with lighter mass than the fixed heel piece, the fast-response-heel-cup adapted to respond to and follow relative displacements between the binding toe and heel pieces resulting from dynamic loadings. 
         [0050]    The heelpiece  152  includes one or more pins  200  biased by corresponding springs  202  to a heel cup  210 . The heel cup  210  defines a secondary mass having a faster response than the primary mass  154  defined by the mounting  156 , to align with the natural frequency of the ski  60  during chatter and other IR inducing scenarios. The heel cup  210  includes protrusions  172 - 1  . . .  172 - 2  ( 172 , generally) defining a receptacle  176  for engaging a boot  70  heel. 
         [0051]    The pins  200  define a linear response to loading the springs  202  biased against the boot  70 , and may include any suitable number of pins or similar elongated members for linear biasing against the heel cup  210  for maintaining engagement with the boot  70 . A larger, unitary shaft, preferably shaped to prevent rotation, may also be employed as a sleeved arrangement, which guards against snow and other materials from potentially interfering with the spring  202  and pin  200  biasing. 
         [0052]    Therefore, configurations herein include at least one spring  202  for biasing the secondary mass  210 , such that the spring  202  provides a tensioning force less than that exerted by the primary mass  154 . An alternate to the spring  202  may include a tensioning member between the primary mass  154  and the boot  70 , such that the tensioning member is for biasing the secondary mass  210  and has a higher natural frequency than the primary mass  154 , in which the tensioning member includes at least one of a spring, hydraulic plunger, pneumatic plunger, elastic material or other deformable material. 
         [0053]    The primary  154  and secondary mass  210  therefore define a ski binding for controlled attachment and detachment with the ski boot  70  under static conditions and disengage in response to dynamic conditions sufficient to displace the primary mass  154 , as the dynamic conditions (such as a ski fall) force the binding beyond the release threshold. In such an arrangement, configurations herein also include a complementary binding (e.g. toe or front) engaging an opposed end of the boot  70  from the binding  150 . In the examples above, the binding  150  is a heel binding, and the binding assembly also includes the toe binding at the opposed end of the ski boot from the heel binding. The toe binding and the heel binding further including a receptacle for engaging a corresponding lip on the ski boot  70 . 
         [0054]      FIG. 8  shows an alternate configuration of a binding according to configurations herein in engagement with a boot. Referring to  FIGS. 7 and 8 , the heel cup  210  slideably engages a receptacle  220  in the heelpiece  152 . The receptacle  176  in the heel cup  210  engages a heel protrusion  71  on the boot  70 . An arc or lip  173  on the upper protrusion  172 - 1  ensures that boot  70  contact occurs as far forward as possible on the heel protrusion  71 . The spring  202  may be unitary or multiple springs may be used, as the spring  202  biases or forces the receptacle  176  in the heel cup  210  toward the boot  70  while slideably engaged in the heelpiece  152 . A second spring  159 ′ independently biases the mounting  156 , while the spring  159  tensions the primary mass  154  of the mounting  156  according to the release threshold. The arc or lip  173 , provides a concave or similar protrusion and edge on the receptacle  176 , such that the edge contacts the lip at a point nearest the boot  70  on the boot protrusion  71 . 
         [0055]      FIG. 9  shows a unitary pivot configuration in the binding of  FIGS. 7 and 8 . Referring to  FIGS. 7-9 , the heel cup  210  pivotally attaches to the heelpiece  152  at a heel pivot  165 , biased in an arcuate direction by spring  202  and curved pin  200 ′, as shown by arrow  230 . The number and shape of the pins  200 ′ may vary, as straight pins may be employed if tolerances between the heel cup  210  and heelpiece  152  allow. The arcuate engagement  230  offsets the arcuate movement of the boot  70  and heel protrusion  71  as the heelpiece  152  pivots upward around pivot  164 . Therefore, the heelpiece  152  includes a pivotal linkage  165  between the primary mass  154  and the secondary mass  210  for offsetting angular displacement the primary mass  154  toward engagement of the secondary mass  210  with a heel protrusion  71  on the boot  70 . 
         [0056]      FIG. 10  shows a complementary toe binding corresponding to a heel binding as in  FIGS. 8 and 9 . In the disclosed configurations, the secondary mass provided by the heel cup  210  biased by the spring  202  mitigates IR from chatter and other scenarios. The toe binding  350  is spring biased to pivot outward, around axis  352 , in the event of harmful forces against the boot  70 . A complementary spring  302  and pin  300  assembly may be disposed in a toe binding  350  for engaging the boot  70  and securing a toe of the boot against the biasing force of the heel binding  150 . The complementary spring  302  offsets displacement of the spring  202  to absorb movement and ensure that the boot remains engaged between the heel cup  210  and toe binding  350 . The toe binding further provides an additional secondary mass  310 , or complementary mass, for engaging the boot  70  toe while biased against the complementary spring  300 . The toe binding therefore defines a complementary mass at the opposed end, such that the complementary mass  310  is biased toward the boot  70  for absorbing movement of the secondary mass  210  and maintaining engagement of the ski boot  70  during displacement of the secondary mass  210 . 
         [0057]      FIG. 11  shows a dual pivot configuration in the binding of  FIG. 9 . Referring to  FIGS. 9 and 11 , a dual pivot arrangement allows the heel cup  210  to engage the boot protrusion  71  at a constant angle even as the heelpiece  152  displaces upwards. In  FIG. 11 , as the pivot  165  allows the heel cup  210  to pivot downward  230  as in  FIG. 9  to offset upwards pivoting around the pivot  164  (arrow  163 ). A heel pivot piece  210 ′ maintains a separate pivot  231  around an upper pivot  167 , thus allowing the heelpiece  152  to maintain the same angle of engagement to the heel protrusion  71 . Particular configurations, therefore, employ the dual pivot for disposing the secondary mass  210  against the boot  70  at a constant angle. 
         [0058]      FIG. 12  shows an alternate configuration employing similar protections for both the heel and toe bindings. The disclosed approach may also be extended to provide complementary operation at both the heel and toe. Referring to  FIGS. 10 and 12 ,  FIG. 10  shows the secondary mass  154  extended to the toe binding.  FIG. 12  shows similar functionality of the toe binding applied to the rear binding. As indicated in  FIG. 10 , disengagement at the toe generally involves an outward pivot of the toe binding  350  around an axis  352 , as the boot  70  toe displaces right or left, as shown by arrows  356  and  358 , respectively. As shown in  FIG. 12 , this pivoting relieves strain around an axis  352 ′ defined by the ankle of the skier. Similar capability can be applied to the heel binding  150  to prevent valgus loads (twisting) often associated with ACL (Anterior Cruciate Ligament) injury. Valgus loads result from a pivoting of the skier&#39;s ankle about an axis  362 ′ defined by a toe of the skier. A pivoting of the heel binding  150  about an axis  362 ′ absorbs these valgus loads, by permitting the heel binding  150  to pivot or rotate around the axis  362  to disengage the heel protrusion  71 . In such a configuration, both the heel and toe bindings further include a secondary mass  210  for absorbing cyclic high frequency loads and pivotal rotation about an axis normal to the plane of the ski  60  for absorbing torsional loads. 
         [0059]    While the methods and apparatus defined herein have been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.