Abstract:
A retention and release mechanism and ski boot for mitigating injury to a skier when the rearward loads, potentially injurious to the user, are imparted to the boot. The mechanism includes a first linkage arm, a latch, and a second linkage arm. The latch is connected to a first end of the first linkage arm, and is configured for direct or indirect pivotal connection to a first portion of the boot (e.g., an upper portion), which is pivotally connected to a second portion of the boot (e.g., a lower portion). The second linkage arm is pivotally connected to a second end of the first linkage arm at a pivot point, and is configured for pivotal connection to the second portion of the boot. The mechanism provides stable orientation of the first portion to the second portion in a “ski” position, and allows rotation of the first portion relative to the second portion in a “release” position, the “release” position being established upon imposition of a predetermined level of rearward force on the boot. A tension adjustment assembly allows for adjustment of the predetermined level of rearward force. The latch may be releasable from the boot to allow rotation of the first and second boot portions relative to each other for facilitating a relatively normal waking motion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part application of U.S. application Ser. No. 09/091,390, filed Jun. 19, 1998 now U.S. Pat. No. 6,131,313 the teachings of which are incorporated herein by reference. 
     Field of the Invention 
     The present invention relates to a retention and release mechanism for ski boots, and, more particularly, relates to a mechanism and ski boot construction which allows for a safe and biomechanically natural rearward articulation of a user&#39;s foot for thereby substantially reducing the risk of severe injury. 
    
    
     BACKGROUND OF THE INVENTION 
     There is an inherent and known risk of injury associated with the sport of downhill skiing. A significant source of injury is the rigid association between a user and prior art skis and ski boots. In view of this, various prior art devices have been proposed for reducing the risk of injury in the sport of downhill skiing. The vast majority of these disclosures relate to improvements in the ski binding, i.e. the mechanism affixed directly to the ski for receiving the ski boot. 
     In addition, there have been attempts to modify the ski boot itself. Generally, however, ski boot modifications have been directed to providing a mechanism for the wearer to more readily step into and out of the boot. For example, in U.S. Pat. No. 5,136,794 there is reported a ski boot consisting of a lower part and of a shaft, in the form of a collar, which is articulated on the lower part and provided with at least one closing buckle. The shaft includes, at the rear, a rocker that interacts with a stop that is integral with the lower part in order to lock the shaft in a position inclined forwards. The rocker is held in inactive position upon opening of the uppermost buckle by means of a cable and a spring. Thus, the shaft is not inadvertently locked during walking. 
     Attention is also directed to U.S. Pat. No. 5,127,171 and art cited therein, which reports a ski boot with a shell having a shaft in two parts, the rear part of which is connected, on the one hand, to the shell and, on the other hand, to the front part of the shaft by two pair of links. The axes of articulation on the rear part are situated, in the closed position of the boot, on the sides of the plane containing the axes of articulation on the shaft and the front part of the shaft. It is possible to open the shaft wide for putting the boot on, while having only a limited rearward tilting of the rear part. The upper connection can be associated with a closing lever. 
     In U.S. Pat. No. 5,107,608, there is reported a ski boot for reducing the incidence of knee injuries wherein the boot is said to exert a forward directional force on the skier&#39;s leg. A releasing means changes the rigid support position for the foot and the lower leg on application of a predetermined level of force by the boot on the wearer. The ′608 patent further reports that rearward pressure of the person&#39;s lower leg against the rear leg element of the boot can be sensed by force sensors producing electrical outputs by the use of piezoelectric material. In addition, as illustrated in FIG. 7 therein, a mechanical latch assembly employing a tension spring is disclosed. The tension spring is described as urging or maintaining the device in ski position, and, when spring force is overcome, a release position is obtained as shown in FIG.  8 . 
     U.S. Pat. No. 5.283,964 discloses a boot device for front-to-back immobilization of the upper, which acts on an oscillating level capable of being supported against a stop on the shell base. The device is constituted by a rectilinear motion control mechanism. The mechanism includes an external control device having an inner part which actuates, via a cam, a sensing device associated with the oscillating lever, thereby imparting to the latter an angular rotating movement around its pin toward a locked or release position in relation to the stop formed on the shell base. 
     Attention is also directed to following foreign patent documents: WO 92/05718 and 0514762A2. More specifically, in WO 92/05718 there is disclosed a ski boot for enhancing the safety of skiing. Finally, reference is made to EP-375-604-A, which discloses a ski boot with a stop holding the leg forward, and French Patent 2647-649-A, which discloses a ski boot with an articulated leg locked in a forward position. The leg has a clip at the back that pivots around the horizontal axis. 
     All of the above, however, are distinct from the present invention, in that they collectively fail to provide, in the boot itself, a practical and effective mechanism for mitigation of knee injuries while used in skiing. There is, therefore, a long-felt need in the art for a ski boot retention and release mechanism that specifically reduces potentially injurious forces to the anterior cruciate knee ligament (ACL). 
     Accordingly, it is an object of the invention to provide a ski boot design that restricts the rearward movement of the rigid upper of a ski boot by allowing rearward travel of the same after a selected level or predetermined threshold of force has been obtained. 
     Another object of the invention is to provide a ski boot design having a mechanism to affect upper displacement when appropriate to create a safer environment and enhanced safety to the user. 
     Yet another object of the invention is to provide a ski boot design having a retention and release mechanism to for improving safety. 
     Another object of the invention is to provide a ski boot that allows the potentially damaging rearward forces at the upper section of a ski boot to be absorbed or transduced. 
     A further object of the invention is to provide a ski boot design which prevents or mitigates the severity of injuries to the anterior cruciate knee ligament and to provide a more safe natural biomechanical rearward articulation in the boot for the user thereof 
     A further object of the invention is to provide a ski boot with a walk position combined with a release mechanism to improve safety. 
     Yet a further object of the present invention to provide ski boot design which prevents or mitigates the severity of injuries to the anterior cruciate knee ligament that can be cost-effectively mass produced. 
     These and other objects of the present invention will become apparent from a review of the description provided below. 
     SUMMARY OF THE INVENTION 
     The present invention is organized about the concept of providing a ski boot having a retention and release mechanism for mitigating injury to the skier&#39;s anterior cruciate knee ligament when the skier exerts rearward loads, potentially injurious to the knee, to the boot shaft upper. The mechanism extends between the lower portion of the ski boot and the upper portion of the boot, which is pivotable with respect to the lower portion. In a “ski” position, the mechanism maintains stable orientation between the upper and lower portions of the boot. Upon imposition of a predetermined level of rearward force, i.e. in the event of a rearward fall, the mechanism moves to a “release” position wherein rearward rotation of the upper relative to the lower portion is allowed to reduce the risk of injury. 
     Recovery from the “release” position to the “ski” position is possible via user stance adjustment in the boot to impart a forward force on the upper. In the event that such a stance adjustment cannot be immediately achieved, the mechanism reduces the moment arm of the ski with respect to the skiers&#39; center of gravity thereby reducing forces to the knee while still providing support of the leg and thereby permitting the skier to continue skiing until recovery or falling. In the case of falling, rearward contact with the snow over the ski tail requires less derangement and force loading of the knee joint. The mechanism is releasable from the ski boot to allow free rotation of the upper relative to the lower in a “walk” position to facilitate a relatively natural walking motion. 
     More particularly, a release and retention mechanism for a ski boot consistent with the invention includes: a first linkage arm having a first end and a second end; a latch connected to the first end of the first linkage arm, the latch being configured for direct or indirect releasable connection to a first portion (e.g., an upper portion) of the boot which is pivotally connected to a second portion of the boot (e.g., a lower portion); and a second linkage arm having a first end and a second end, the first end of the second linkage arm being pivotally connected to the second end of the first linkage arm at a pivot point, and the second end of the second linkage being configured for pivotally connection to the second portion of the boot. The mechanism is configured to provide stable orientation of the first portion to the second portion in a first position, and to allow rotation of the first portion relative to the second portion in a second position, the second position being established upon imposition of a predetermined level of rearward force on the boot. 
     The mechanism may include a plate affixed directly to the first portion and a locking pin affixed to the plate. The latch may be releasably securable to the first portion through the locking pin. The latch may be disposed within a central opening in the first linkage arm, and the latch and the first linkage arm may have corresponding slots for receiving the locking pin. 
     A compression spring may be disposed between the latch and the first linkage arm. The compression spring biases the latch axially outward from the opening to a locking position wherein a portion of the latch is positioned in the slot in the first linkage arm to prevent engagement of the locking pin with the latch when the latch is released therefrom, and to prevent release of the latch from the locking pin when the locking pin is disposed in the corresponding slots. 
     A tension adjustment assembly may be provided for establishing the predetermined level of rearward force. The tension adjustment assembly may include a tension spring, the tension spring establishing a bias force to bias the first linkage arm against the second linkage arm to establish the predetermined level of rearward force. The adjustment assembly may also include an adjustment screw fixed in the mechanism relative to the tension spring and an adjustment nut threadably engageable with the adjustment screw, the nut having a surface disposed on the tension spring for compressing the spring upon threading of the screw into the nut. The tension adjustment assembly may be disposed within a central opening in the first linkage arm, with the screw being accessible through the central opening to permit rotation of the screw by a tool. A visual tension indicator may be positioned adjacent a viewing slot in the first linkage arm, the nut being viewable through the viewing slot for comparison against the visual tension indicator. 
     A mounting bracket may be affixed directly to the second portion of the boot, and the second end of the second linkage arm may be pivotally secured to the mounting bracket through a pivot pin. A torsion spring may be provided for biasing the second linkage arm for rotation about the pivot pin in a direction toward the second portion. Rearward rotation of the first linkage arm relative to the second linkage arm may be limited by contact between the first and second linkage arms. Forward rotation of the first linkage arm relative to the second linkage arm may be limited by contact between the first and second linkage arms. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of the present invention, together with other objects, features and advantages, reference should be made to the following description of the preferred embodiment which should be read in conjunction with the following figures wherein like numerals represent like parts: 
     FIG.  1 : is a perspective view of an exemplary retention and release mechanism consistent with the present invention; 
     FIG.  2 : is an exploded view of the retention and release mechanism illustrated in FIG. 1; 
     FIG.  3 : is a front view of the retention and release mechanism illustrated in FIG.1; 
     FIG.  4 : is a sectional view of taken along lines  4 — 4  in FIG. 3; 
     FIG.  5 : illustrates an exemplary retention and release mechanism and ski boot consistent with the invention with the mechanism in a “ski” position; 
     FIG.  6 : illustrates an exemplary retention and release mechanism and ski boot consistent with the invention with the mechanism in a “released” position; 
     FIG.  7 : illustrates an exemplary retention and release mechanism and ski boot consistent with the invention with the mechanism in a “walk” position; 
     FIGS.  8 A- 8 C: illustrate successive positions of upper and lower arm linkages of an exemplary retention and release mechanism consistent with the invention as the linkages travel from a “ski” position to a “release” position; and 
     FIG.  9 : illustrates a “ski” position for another exemplary embodiment of a retention and release mechanism consistent with the invention. 
    
    
     DETAILED DESCRIPTION 
     With reference now to FIGS. 1 and 2, there is shown an exemplary embodiment of a retention and release mechanism  10  consistent with the invention. As shown, the mechanism generally includes a plate  12 , a release latch  14  disposed over a compression spring  16 , an upper arm linkage  18  housing a tension adjustment assembly  20 , a lower arm linkage  22  having a first end pivotably attached to an end of the upper aim linkage by a pivot pin  24  and a second end pivotably attached to a mounting bracket  26  by a pivot pin  30 , and a torsion spring  28  for creating a bias force tending to rotate the lower arm linkage  22  in an inward direction, i.e., toward a ski boot as shown, for example, in FIG.  5 . The tension adjustment assembly  20  generally includes a threaded release tension adjustment screw  32 , a corresponding tension adjustment nut  34 , a tension spring  36 , a retainer pin  38  and a stop  40 . 
     The plate  12  is adapted to be affixed to a ski boot. Those skilled in the art will recognize that there are a variety of means by which the plate  12  may be affixed to the boot. In the illustrated exemplary embodiment, however, the plate includes a first bore  50  on a tab  52  and a second bore  54  at an opposite end of the plate. The tab  52  may be bent at a 90 degree angle relative to the plate, e.g. at line  56 , and inserted into an opening (not shown) in the upper of the ski boot. The tab may be further bent to position the end of the tab and the bore  50  against the interior surface of the upper. Fasteners (not shown) may be passed through the bores  50 ,  54  and into the boot to secure the plate  12  thereto. 
     The plate also includes a pair of spaced, opposed tabs  58 ,  60  extending outward at a 90-degree angle from the back surface  68  of the plate. The tabs  58 ,  60  include aligned lock pin bores  62 ,  64  therein for receiving opposite ends of a lock pin  66 . As will be described in detail below, the lock pin is dimensioned to be removably received within corresponding transverse slots  70 ,  80  in the release latch  14  and upper linkage arm, respectively. 
     The release latch  14  has a head portion  72  and a shaft portion  74 . With reference also to FIGS. 3 and 4, the end of the shaft portion distal from the head is received within central opening  76  in the upper arm linkage  18 . As shown particularly in FIG. 4, the compression spring  16  is positioned between a shelf  90  on the interior of the latch and an opposing shelf  92  on the interior of the upper arm linkage  18 . A pair of tabs  94 ,  96  extends radially outward from the latch and into corresponding aligned slots, e.g. slot  98  formed in the sides of the upper arm linkage. The release latch is thereby captured within the upper arm linkage and biased outward from the linkage by the compression spring  16 . 
     Axial travel of the latch within the opening in the linkage arm  18  is limited by engagement of the tabs  94 ,  96  with the ends of the slots, e.g. slot  98 . In an at rest position, the compression spring biases the tabs against the upper ends of the slots, and the transverse slot  70  in the latch extends into the opening in the upper linkage arm defined by the slot  80  therein, as shown, for example, in FIG.  7 . In this position, the lock pin may be captured in the slots  70 ,  80  by a lip  100  on the latch. The latch may, however, be depressed against the force of the spring  16  until the tabs contact the bottoms of the slots, and until the slot  70  aligns with the slot  80  to permit entry or exit of the lock pin  66  into the slots  70 ,  80 . 
     The upper arm linkage  18  provides a housing for the tension adjustment assembly  20 . With continued reference to FIG. 4, the adjustment screw  32  has a head portion  102 , which extends through a bore in the shelf  92 . The head is secured within the bore with a radially extending flange  104  positioned against a bottom surface of the shelf  92 . The head is secured within the bore to prevent axial movement of the screw  32 , while allowing rotation of the screw. 
     FIGS. 2 and 4 show alternative exemplary embodiments, i.e.  34 ,  34   a , respectively, of the adjustment nut. The nut  34  in FIG. 2 includes a head portion  106  that rests on a top of the compression spring  36  and a shaft portion  108 , which is adapted for extending into a central opening  110  of the compression spring. The nut  34   a , as shown in FIG. 44, has a simple flat construction. A bottom surface  112  of the nut  34   a  rests on the top of the compression spring. 
     In any embodiment, however, the nut includes a threaded bore for meshingly engaging the threads on a shaft  114  adjustment screw. The head  102  of the screw is exposed at the top surface of the shelf  92  to permit access to the head by a tool (not shown) extending through the opening  116  in the latch from the top thereof and through the central opening  118  of the spring  16 . The head is adapted to receive the tool so that the tool may be manipulated to rotate the head of the screw. For example, in the illustrated exemplary embodiment, the head includes a transverse slot  120  therein for receiving the end of a standard screwdriver. The end of the screwdriver may be passed through the top of the latch  14  and through the spring  16  to engage the slot  120 . 
     Rotation of the screw by the tool causes translation of the adjustment nut  34 ,  34   a  on the shaft  114  of the screw. The tension spring  36  is trapped between the bottom surface  112  of the nut  34   a  (or the bottom of the flange of the nut  34  in FIG. 2) and the flange  122  on the retainer pin  38 . The retainer pin is fixed within the upper linkage arm  18  with a bottom surface the flange  122  disposed against the annular stop  40 , which is fixed around the pivot pin  24 . In the illustrated embodiment, the retainer pin includes a shaft portion  124  that extends into the central opening  110  of the spring to stabilize the spring and the pin within the upper linkage arm. As will be described in more detail below, with the spring trapped between the nut  34   a  and the pin  38 , translation of the nut caused by rotation of the screw results in corresponding compression/relaxation of the compression spring depending on the direction of rotation. 
     The upper linkage arm is pivotably connected to the lower linkage arm  22  by the pivot pin  24  extending through slots  126 ,  128  in clevis plates  130 ,  132  formed on the upper linkage arm and corresponding bores  134 ,  136  in devises  138 ,  140  formed on the lower linkage arm. The slots permit limited axial movement of the upper linkage arm relative to the lower linkage arm to facilitate pivotal movement the upper arm relative to the lower arm. The lower linkage arm includes a transverse bore  142  in the bottom portion thereof. The arm is pivotally secured to the mounting bracket  26  by the pivot pin  30  extending through the bore and corresponding aligned bores  144 ,  146  in the mounting bracket  26 . Bores  148 ,  150  in the mounting bracket are provided to facilitate affixation of the bracket  26  to the ski boot by fasteners, e.g. screws, extending through the bores and into the boot. 
     The torsion spring  28  is positioned around the pivot pin  30  and has a first end  152  captured by the lower linkage arm and a second end  153  captured the mounting bracket. The spring thereby biases the linkage arm for rotation about the pivot pin in a direction toward the boot. In this non-release position, as shown for example in FIGS. 1,  3  and  4 , the bottom edge  156  of the upper linkage arm is positioned adjacent the upper edge  160  of the lower linkage arm at a point which is offset from the axis of the pin  24 . 
     In a release position rotation (i.e., in a direction toward the boot) of the upper arm  18  relative to the lower arm  22  is limited by contact of the rear surface  162  of the upper arm against the contact points, e.g. point  164 , on both sides of the lower linkage arm, as shown, for example, in FIG.  6 . This limit may also be obtained by interference of the boot upper with the lower portion, or by means of a dash pot or stop(s) that coacts with the one or more parts of the retention and release mechanism or another portion of the boot upper. In any event, the secondary “stop” or arrest mechanism should limit rearward travel of the upper to less than approximately 20 degrees rearward from vertical. 
     The operation of an exemplary release and retention mechanism consistent with the invention, along with additional structural features, will now be described. With reference also to FIGS. 5-7, the plate  12  is secured to the rigid upper  200  of the ski boot  202 , while the mounting bracket  26  is secured to the lower portion  204  of the boot. In the “ski” position, as shown in FIG. 5, the locking pin  66  is disposed within the slot  70  in the latch and the slot  80  of the upper linkage arm. The lip  100  on the latch extends upward at the front of the slot  70 . The compression spring  16  biases the latch against the locking pin  66  and the lip prevents removal of the pin  66  from the slots  70 ,  80  absent depression of the latch  14  by a user. 
     With the mechanism in “ski” position, the lower linkage arm  22  is biased toward the boot  202  by the torsion spring  28 . With reference also to FIG. 8A, the tension spring  36  biases the upper linkage arm against pivot pin  24  into the bottom  127  of the slot  126 - 128 . In this position, the axes  17 ,  19  of the two linkages are not aligned, and the linkages contact the contact point A between the end  156  and the edge  160 . The engagement of the locking pin with the release mechanism provides a rigid structure that resists rearward rotation of the upper  200  relative to the lower portion  204  of the boot about the pivot point  206 . 
     The level of resistance before releasing against rearward rotation of the upper  202  is adjustable through the tension adjustment assembly  20  to provide a suitable level of resistance for a particular user, e.g. depending on the user&#39;s physical characteristics and skiing style. A tool may be passed through the top of the latch to rotate the adjustment screw, as described above. In one direction of rotation, the rotation of the screw causes axial motion of the nut  34   a  tending to compress the spring  36  and increase the resistance to rearward rotation by increasing the force against the lower linkage arm  22  through the pivot pin  24 . In an opposite direction of rotation, the nut translates in an opposite direction to relax the spring  36  and decrease the resistance to rearward rotation of the upper  202 . 
     The level of releasing resistance established by the tension adjustment assembly may be indicated on a visual tension indicator  208 . As shown, for example, in FIG. 2, the indicator may mount on a front of the upper linkage arm, and may have a slot  210  that aligns with a corresponding slot  212  in the linkage arm. The position of the top of the adjustment nut, e.g. nut  34 , may be observed through the slots  210  and compared against a scale (not shown) provided on the face of the tension indicator  208 . An appropriate level of resistance/tension based on the scale may be recommended for a particular user. 
     With the mechanism in the “ski” position, as shown in FIG. 5, a user may ski normally with the upper and the lower portion of the boot in a stable relationship to each other and the user. In the event of a rearward fall, however, the user would lean back in the boots, generating a rearward rotational force on the upper relative to the pivot point  206 . Advantageously, this force would transfer to the mechanism  10  and would overcome the resistance provided by the tension adjustment assembly  20  and the bias force of the torsion spring. During the rearward rotation of the upper  202 , the force F causes downward travel of the upper linkage arm  18  in a direction of force F with the pivot pin  24  travelling toward the top  129  of the slots  126 - 128 . During travel, the two linkages rotate in a direction away from the boot around the point of contact A between the end  154  and the edge  160 . 
     At the predetermined level set by appropriate adjustment of the tension spring, as illustrated in FIG. 8B, the axes  17 ,  19  of the two linkages are aligned and the end  156  and the upper edge  160  contact at point A, which is offset by a distance d from the axis  23  (FIG. 3) of the pivot pin  24 . At this point, with only an incremental increase in the force F, the upper linkage  18  travels downwardly, and, due to the offset point of contact A from axis  23 , creates a component P of force which urges the mechanism to open toward the release position, as illustrated in FIG.  8 C. 
     In another exemplary embodiment of the invention, the two linkages may be already aligned in the rest position, as illustrated in FIG.  9 . In this embodiment, the two linkages are not in contact from the beginning. During rearward rotation of the upper  202 , the upper linkage arm travels downwardly. At the predetermined level of force, the two linkage arms come in contact at the point A, as illustrated in FIG. 8B, and then open toward a release position as shown, for example, in FIG.  8 C. 
     The release and retention mechanism thus moves to the “release” position, in which the upper may be substantially vertically disposed, as shown, for example, in FIG.  6 . The rearrangement of the upper and lower arm linkages in this manner allows the upper to rotate rearwardly until travel is arrested by contact of the rear surface of the upper link arm  162  against the contact points  164  of the lower link arm. This arrest may occur, for example, when the angle θ between the upper and lower linkage arms reaches approximately 90 degrees to correspond to rotation of the upper of approximately 20 degrees rearward from the vertical “ski” position. When the skier recovers from the fall and is able to rotate the upper forward again, the upper and lower arm linkages will rearrange into the stable “ski” position with the assistance of the torsion spring  28 . 
     Another advantageous feature of a retention and release mechanism consistent with the invention is illustrated in FIG. 7, wherein the mechanism is illustrated in “walk” position. It is well known that normal walking motion is severely restricted by prior art boot designs wherein the upper  200  is rigidly fixed relative to the lower portion  204  of the boot. According to the present invention, however, a user may release the latch  14  from the locking pin  66  by depressing the latch and rotating the mechanism rearwardly away from the locking pin. In this “walk” position, the retention and release mechanism is disconnected from the upper, thereby allowing rearward rotation of the upper during walking to allow a more natural waking motion. In the “walk” position, the torsion spring  28  biases the mechanism toward the boot to prevent undesired motion of the mechanism relative to the boot, and the lip  100  prevents inadvertent engagement of the latch with the pin  66 . When the user desires to continue skiing, the mechanism may be returned to the “ski” position simply by depressing the latch  14  to allow entry of the locking pin into the slots  70 ,  80 , and then releasing the latch to capture the locking pin. 
     Thus, according to the present invention there is provided a release and retention mechanism which, in a “ski” position, provides a stable relationship between a user and the upper and lower portions of a ski boot. When the user falls rearward, however, the mechanism releases to a “release” position at predetermined level of rearward force as established by the user through a tension adjustment assembly. In the “release” position the upper is allowed limited rearward rotation, thereby significantly reducing damaging forces on the knee joint and the likelihood of injury to the anterior cruciate ligament. When the user recovers control after the fall the user rotates the upper forwardly to return the mechanism to the “ski” position. Alternatively, if the skier cannot recover control after the mechanism is forced into the “release” position, the mechanism has the effect of shortening the effective moment arm of the ski tail to the knee, thereby increasing the likelihood that the skier will fall over the tail of the ski without damaging knee ligaments. The invention, therefore, functions to absorb potentially injurious forces before the forces are sustained by the wearer&#39;s knee joint. 
     The embodiments described herein are but some of the several which utilize this invention and are set forth here by way of illustration but not of limitation. For example, a latch consistent with the invention may take a variety of forms, and may be permanently or releasably securable to the boot, either directly or through other elements such as a locking pin. Also, the orientation of a mechanism consistent with the invention relative to the upper and lower portions of the boot could be reversed. It is obvious that many other embodiments, which will be readily apparent to those skilled in the art, may be made without departing materially from the spirit and scope of the invention as defined in the appended claims.