Abstract:
A snowshoe has a pivoted mounting on its boot harness, for rotation about a pitch axis for a first degree of freedom in movement of the user&#39;s boot relative to the snowshoe; and provision for a second degree of freedom of motion along a roll axis, allowing the user&#39;s boot to tip from side to side, particularly for uneven or sidehill terrain. In both axes the boot preferably is spring-biased toward a neutral position. At the same time, freedom of movement is restricted and essentially prevented between the boot and snowshoe relative to a third axis, the yaw or vertical axis. Several different structural arrangements are disclosed in several types of snowshoes, for achieving the second degree of freedom.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to snowshoes, and more specifically is concerned with the freedom of movement afforded between the user&#39;s boot and a snowshoe. The invention provides for addition of some rotational freedom about a roll axis, i.e., within a frontal plane, to make more comfortable, safe and convenient the traversing of hillsides where the snowshoe cannot be planted flatly on terrain. 
     A considerable number of snowshoes provide for freedom of movement of the user&#39;s foot and boot relative to the snowshoe on a pitch axis, that is, a traverse horizontal axis below the boot. This aids in walking over terrain where the user naturally tends to tip the foot, toe-downwardly, as the opposite foot is advanced and as the foot is lifted and moved forward, and avoids tripping the toe end of the snowshoe in the snow. Such pivoting has been achieved by supporting the boot footbed on support straps, as in Atlas Snow-Shoe Company&#39;s U.S. Pat. Nos. 5,440,827, 5,687,491 5,699,630, and 6,256,908; and has also been accomplished with simple pivot bars, as in U.S. Pat. No. 5,946,829, for example. 
     When traversing a side hill path, a snowshoe user needs another degree of freedom for comfort and safety in full terrain engagement—rotation about a “roll” axis, which can be described as rotation within the frontal plane. This should be a limited freedom of movement, with spring loading effective to return the snowshoe to the normal position and to resist the roll rotation of the snowshoe more strongly as the degree of roll rotation increases. Such a freedom of movement will allow the snowshoe to tip along the roll axis when the user plants the snowshoe down against terrain which is uneven and particularly, terrain which slopes from one side to the other. The snowshoe would therefore follow the terrain and be planted more firmly, while also increasing comfort and safety to the user and reducing ankle and foot stress. 
     U.S. Pat. No. 5,946,829 discloses a snowshoe which is aimed at the above goal. The snowshoe has a frame of a convoluted configuration, not contiguous in a closed loop around the frame, and in which inner members of the frame near the rear turn forward to form a flexible, spring-biased mounting by frame twisting that allows some degree of torsional freedom along the roll axis, i.e., in the frontal plane. That type of snowshoe frame has some disadvantages compared to the present invention described below. 
     SUMMARY OF THE INVENTION 
     The invention described herein achieves a second degree of rotational freedom, for movement within the frontal plane or about the roll axis of the snowshoe, in an efficient manner which still provides the benefit of a relatively simple and straightforward snowshoe design. This second degree of freedom is combined with the typically permitted rotation about the traverse or pitch axis, also preferably spring-biased toward a pre-selected “zero” position. At the same time, the configuration of the invention substantially prevents any rotation of the snowshoe in the yaw direction, about a vertical axis, which rotation would tend to be unstable and awkward and would cause discomfort and instability. 
     The two degrees of rotational freedom can be achieved in several different ways. As one example, the footbed of the snowshoe harness can have a mounting which includes a transverse horizontal pivot, preferably with spring-biased torsional resistance tending to return a pivot frame back to a prescribed relationship with the snowshoe frame. An additional pivot can be made between the footbed and the pivot frame, via a roll pivot axis at the middle of the pivot frame, permitting the desired rotation in the frontal plane. Leaf springs or a torsion rod can be used as a spring to bias this second degree of rotational freedom back toward the normal, undeflected position. Coil springs can be used for the zero-biasing of the footbed if desired. 
     Another configuration allowing two degrees of freedom uses strap suspension, somewhat similar to the front harness binding shown in the above Atlas Snow-Shoe Company patents. In this case, however, the support straps support a longitudinally extending rod or mounting device along a roll axis rather than supporting the footbed itself. The footbed is then secured to the rod or other pivot mounting so as to allow for the desired roll rotation. The rod can be a torsion rod, providing the needed bias. In this way, a simple support mechanism provides two degrees of spring-biased rotational freedom. 
     Another configuration for achieving the desired two degrees of freedom utilizes a pair of torsion arms secured to the normal peripheral snowshoe frame, these arms extending generally parallel to the snowshoe frame and to one another and being positioned just inwardly of the frame members. The arms have a tightly biased flexibility, such that if a torsion rod or pivot rod is connected between their forward tips, some degree of biased roll rotation is permitted. The rod extending between these arms provides the normal pitch rotation, and if this is provided as a torsion rod, the desired biasing is included. 
     A variation of the above is achieved in a molded snowshoe, preferably of fiber-reinforced plastic. Integrally molded arms extend in a forward direction within the snowshoe body, cantilevered from back ends of the arms. The front ends of the arms allow spring-biased roll freedom when a footbed is secured via these forward arm ends. 
     Another form of the invention has a snowshoe frame which can twist and rotate at certain points to allow footbed tilt relative to terrain. 
     It is therefore among the objects of the invention to provide a relatively simple and reliable connection between the user&#39;s boot and a snowshoe, whereby two degrees of freedom of movement of the snowshoe relative to the user&#39;s boot are permitted, these two degrees of freedom being rotation about the normal pitch axis and also about a roll axis, preferably with both axes biased toward a normal position. These and other objects, advantages and features of the invention will be apparent from the following description of Preferred Embodiments, considered along with the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic prospective diagram indicating possible degrees of rotational freedom in a snowshoe having a frame of conventional construction. 
         FIG. 2  is a plan view showing a snowshoe frame with one form of boot binding support affording two degrees of rotation of freedom, in pitch and roll directions. 
         FIG. 2A  is a side elevation view of the snowshoe of FIG.  2 . 
         FIGS. 3 and 3A  are plan and side elevation views showing another structural configuration for affording the desired two degrees of rotational freedom in a snowshoe. 
         FIG. 3B  is a schematic perspective view showing a molded snowshoe providing the desired two degrees of freedom, in a manner similar to  FIGS. 3-3A . 
         FIGS. 4 and 4A  are an exploded view in perspective and a side cross sectional elevation view illustrating a pivot frame and footbed for implementing a further form of the invention to produce two degrees of rotational freedom. 
         FIGS. 5 ,  5 A and  5 B are exploded perspective and sectional views indicating a further form of the invention, with  FIGS. 5A and 5B  showing flexing of the footbed within the second degree of rotational freedom. 
         FIGS. 6 and 6A  are additional exploded perspective and sectional schematic views indicating a further form of the invention for achieving two degrees of rotational freedom. 
         FIGS. 7 and 7A  are further exploded perspective and cross-sectional views, indicating another variation of the invention for achieving the desired degrees of freedom. 
         FIGS. 8 and 8A  are exploded perspective and schematic cross-sectional views showing still another form of snowshoe footbed pivot arrangement according to the invention. 
         FIGS. 9 and 9A  are views generally similar to  FIGS. 8 and 8A , but show a variation. 
         FIGS. 10 and 10A  are exploded perspective and schematic sectional views showing a further variation of FIG.  8 . 
         FIGS. 11 ,  11 A and  11 B are similar setup drawings showing a further variation. 
         FIGS. 12 ,  12 A and  12 B are additional exploded perspective and cross-sectional views indicating another structural configuration of the invention for achieving the desired two degrees of rotational freedom. 
         FIGS. 13 ,  13 A and  13 B are further exploded perspective and schematic sectional views, showing a further variation affording the desired degrees of freedom in accordance with the invention. 
         FIGS. 14 ,  14 A and  14 B are exploded perspective and schematic sectional views showing a further form of snowshoe footbed suspension providing the desired degrees of freedom. 
         FIGS. 15 ,  15 A,  15 B and  15 C are views showing a further variation of the invention, with  FIG. 15C  schematically indicating a desired level for the rotational axis of the second degree of freedom relative to the user&#39;s foot. 
         FIGS. 16 ,  16 A and  16 B show a further variation of a two-axis snowshoe footbed support, in this case providing the axis of the second degree of freedom at an approximate optimal location. 
         FIGS. 17 ,  17 A and  17 B show another variation, wherein a snowshoe frame provides for limited rotation on the roll axis. 
         FIG. 18  is a perspective view from the bottom showing a molded plastic composite snowshoe having curved metal rails insert molded into the plastic material. 
         FIG. 19  is an enlarged view showing a portion of the snowshoe of  FIG. 18 , and indicating a footbed secured by WORD cables from the molded composite snowshoe body. 
         FIG. 20  is a perspective view showing the upper side of the molded composite snowshoe of  FIGS. 18 and 19 . 
         FIG. 21  is a schematic view in perspective showing a portion of a snowshoe and indicating a cable binding or footbed suspension in one embodiment. 
         FIG. 22  is a bottom perspective view schematically showing a portion of a snowshoe and indicating another embodiment of a cable suspension. 
         FIG. 23  is schematically similar to  FIG. 22 , showing a further embodiment. 
         FIGS. 24A ,  24 B, and  24 C are schematic diagrams indicating frontal plane rotation of the cable binding, i.e. rotation about a roll axis. 
         FIG. 25  is a schematic diagram in perspective, demonstrating resistance of cable binding embodiments of the invention to rotation about the yaw axis. 
         FIG. 26  is a schematic perspective view showing a portion of a snowshoe bottom and indicating a further embodiment of a cable binding or suspension. 
         FIG. 27  is a perspective view similar to  26 , indicating a further embodiment. 
         FIG. 28  is a schematic view showing a portion of a cable suspension to demonstrate the principle involved. 
         FIG. 29  is a schematic view similar to  FIG. 28 , but showing cables passing through a single hole. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  indicates conceptually the framework and principles of the invention, showing potential rotational axes of a snowshoe relative to the user&#39;s boot, or to a footbed  12  to which the user&#39;s boot is secured. These axes of rotation, as mentioned above, are a transverse horizontal axis  14 , or pitch axis, regarding potential rotation in the sagittal plane; the longitudinal horizontal axis  16  or roll axis, pertaining to rotation in the frontal plane; and the vertical axis or yaw axis  18 , regarding rotation within a horizontal plane. This latter rotation is wholly undesirable and leads to instability in use of the snowshoe. Rotation about the yaw axis is to be avoided as nearly as possible. 
     A rotation about the pitch axis, within the sagittal plane, is desirable as discussed previously, and has been provided for in numerous previous snowshoes of Atlas Snow-Shoe Company and others. In the schematic perspective view of  FIG. 1 , this rotation is indicated as occurring via a bar or pivot pin  20  which permits rotation of the footbed  12  relative to the snowshoe frame  22 . Such rotation has been provided on Atlas snowshoes via straps which secure the footbed to the frame, establishing the desired limited rotation and also a biasing force to return the footbed and snowshoe to a desired “zero” relative position. As discussed above, limited rotation about the roll axis is also desirable but has seldom been provided on snowshoes. U.S. Pat. No. 5,946,829 provides for some degree of rotation approximately on this axis, but this is accomplished via a special snowshoe frame which does not comprise a uniform peripheral frame  22  secured together at the rear (as at  24  in  FIG. 1 ) as typical of frame and flexible deck type snowshoes. The cited patent may also provide for some rotation in the undesirable direction, about the yaw axis  18 . 
       FIGS. 2 and 2A  show one embodiment of the invention for permitting the desired two degrees of rotational freedom without any substantial freedom of movement about the yaw axis. In this form of the invention, the snowshoe  25  has a snowshoe frame  26  about which straps  28 ,  30  are wrapped in the manner shown, which is similar to what is shown in Atlas Snow-Shoe Company U.S. Pat. No. 5,440,827, for example. These straps  28 ,  30  can comprise a single strap. In this case the straps are spread apart widely in the central portion of the snowshoe&#39;s boot harness area, for connection to a rod  32  as shown. See  FIGS. 2 and 2A . The rod  32  may be rigidly connected to the straps  28  and  30 , with the rod having torsional flexibility such that a footpad mounted near the center portion of the rod is afforded some degree of rotation along the center line of the rod. This provides the roll axis rotation described, preferably affording roll rotation of about 10° to 15° (or about 10° to 20°) each direction. Otherwise, the rod  32  can be mounted in bushings  34  at both ends, affording free rotation of the rod, with limitation to movement and biasing back to the “zero” position accomplished by other structure, such as coil or leaf springs. 
       FIG. 2A  shows the snowshoe  25  in elevation, indicating that the rod  32  has a zero position in which it is inclined forwardly/downwardly, to establish the pitch-axis bias position such that the toe end of the snowshoe is urged downwardly. 
       FIGS. 2 and 2A  show that the roll axis rotation (frontal plane rotation) of the snowshoe relative to the boot is achieved by rotation about the rod  32 , while pitch-axis rotation (about the sagittal plane) is provided by the twisting of the binding straps  28  and  30 , which effects a spring-like deflection of the snowshoe frame in the preferred situation in which the straps  28 ,  30  are not stretchable. Undesirable rotation about the yaw axis is resisted by the triangular geometry shown, by which the rod  32  is secured to the snowshoe frame via two triangles established with the straps  28  and  30 . 
     In  FIGS. 3 and 3A , a snowshoe  35  supports a footbed  36  for a user&#39;s boot  38  in a different manner, but again achieving two degrees of rotational freedom, about the pitch axis and the roll axis. Here, the snowshoe frame  40  supports a pair of torsion arms  42  via frame joint inserts or collars  44  (or other mechanical means) rigidly connected to the frame. The torsion arms  42  can be of metal or reinforced plastic, capable of deflecting sufficiently to allow the desired degree of roll-axis rotation, with biased return to normal position. Note that the left and right torsion arms  42  can deflect independently. A pivot rod  46  secured to and extending between ends of the torsion arms allows sagittal plane rotation, about the pitch axis. This rod can be freely rotating relative to the arms, or constructed as a torsion rod and rigidly secured to the arms. The latter will provide a return force to the normal pitch position. This rod can be either metal or elastomer construction. 
       FIG. 3B  shows a variation of what is shown in  FIGS. 3 and 3A , for a molded plastic composite snowshoe  50 . In this case, the snowshoe has no peripheral frame in the sense of that provided in  FIGS. 2-3A , and has no flexible decking suspended on such a peripheral frame, but instead the molded composite snowshoe  50  provides both a snowshoe decking  52  and, in essence, a frame which adds the needed rigidity (stiffener ridges can be included, not shown). The snowshoe  50  is integrally molded to provide a pair of torsion arms  54  which deflect angularly downwardly or upwardly and which function essentially the same as the torsion arms  42  in  FIGS. 3 and 3A . As shown, the torsion arms  54  extend forward from integral connection areas  56  to forward ends  58  of the arms, where they support a transverse rod  60  which can be similar to what is shown at  46  in FIG.  3 . The rod  60  can provide for pitch-axis pivoting, as in the earlier embodiment, and it can also be a torsion rod which provides the needed spring-like biasing force to return the snowshoe back to a desired normal pitch position relative to the binding or boot platform (not shown in FIG.  3 B). 
       FIG. 4  shows another preferred embodiment for achieving the two degrees of rotational freedom in a snowshoe binding as desired. Here, the two degrees of rotational freedom are achieved by a pivot frame  65 , to which is pivotally secured a footbed platform  66 . The snowshoe and its frame are not shown in  FIG. 4 ; the front of the snowshoe is generally to the left in  FIG. 4  as shown by the arrow  68 . The pivot frame  65  is secured to the snowshoe frame at end points  70 , which may be by rigid attachment or via a pivot. If a rigid attachment, the pivot frame  65  acts as a torsion bar, providing for limited rotation about the pitch axis, within the sagittal plane, and providing a return force. The pivot frame  65  includes a central pivot support with upturned flanges  72  as shown, for receiving the pivotal footbed via a torsion rod  74 . The torsion rod can be fixed to one of the flanges  72 , at an aperture  75 , as by welding, spline or other connection, and to the footbed aperture  76 , on the opposite side. In this way, the footbed is supported for pivoting movement along the roll axis (in the frontal plane), and the length of the torsion rod  74  is available for twisting to provide the spring action tending to return the snowshoe to the “zero” position relative to the footbed and the user&#39;s boot.  FIG. 4A  shows this arrangement in a side elevation cross sectional view. 
       FIG. 5  shows another configuration for achieving the same objective. In this form of the invention, a snowshoe frame  80  supports a binding strap or straps  82 , in substantially the manner in which Atlas Snow-Shoe boot bindings have been supported previously for rotation along on the pitch axis, as shown, for example, in Atlas U.S. Pat. No. 5,440,827. 
     As shown in  FIGS. 5-5B , the snowshoe in this embodiment achieves the desired second degree of rotational freedom about the roll axis through use of rubbery elastomeric bushings  84 . The showshoe&#39;s front cleat  86 , which also provides or is connected to a footbed for the user&#39;s boot, is secured to the binding strap or straps  82  via these elastomeric bushings  84  as indicated in the exploded view of FIG.  5 . This provides for side to side tipping of the snowshoe, i.e. deflection about the roll axis, through deformation of the bushings  84 . The transverse sectional elevation view of  FIG. 5A  shows the footbed/front claw  86  in the normal position, while the similar cross sectional view of  FIG. 5B  shows the footbed and the snowshoe in a position of maximum roll-axis rotation to one side. This allows the snowshoe to follow sloping terrain, i.e., a side hill condition, without over-stressing the user&#39;s foot, ankle and leg. 
       FIGS. 6 and 6A  show another arrangement, essentially a variation of FIG.  5  and also incorporating some of the features of  FIGS. 4-4A . In this arrangement, a pivot frame  88  is secured to the opposing bars of a peripheral frame (not shown), and this pivot frame can be mounted for rotation about the pitch axis (through the length of the pivot frame  88 ), with biasing restraint provided by appropriate forms of springs or other springable deflection devices, or the pivot frame can be fixed to the snowshoe frame, serving as a torsion bar as described relative to FIG.  4 . 
     In either event, the footbed platform  90  of this assembly, which can also be a front claw as in  FIG. 5 , is secured to the pivot frame  88  by elastomeric bushings  92  as in FIG.  5 . These are shown as being secured by a bolt and nut  94 ,  96 , through a central hole  97  in the pivot frame. As an alternative, the bushings  92  could be replaced with compression springs. 
       FIG. 6A  is a transverse cross sectional view showing deflection of the foot platform  90  about the roll axis, i.e., within the frontal plane. As shown in this schematic view, recesses  98  in the sides of the footbed  90  serve as rotation guides, these recesses riding over the pivot frame  88  and preventing yaw-axis rotation. The footbed platform  90  and pivot frame  88  are shown at maximum relative frontal plane rotation in one direction in FIG.  6 A. 
       FIGS. 7 and 7A  show another preferred embodiment of the invention, in a variation of FIG.  6 . Orientation relative to the snowshoe is the same. In this arrangement the pivot frame  100  takes a different form, but still is secured to the snowshoe frame (not shown) in a manner as described above, but with pivoting connections at left and right. 
     Here, the pivot frame has pivot support flanges  102 , on which a special footbed  104  is pivotally mounted via pivot ears  106 . The footbed preferably is formed integrally of a single piece of metal, with left and right spring leaves  108  as shown. These, as indicated in the transverse sectional view of  FIG. 7A , act as springs bearing down against the platform  110  of the pivot frame, tending to return the footbed platform  104  to the central, undeflected state about the roll axis  112  as shown in FIG.  7 A. 
       FIGS. 8 and 8A  show a further variation on the basic operation of several of the previously described embodiments. The orientation of the components in  FIG. 8  is the same as that in  FIGS. 6 and 7 , and  FIG. 8A  is a cross section similar to  FIGS. 6A and 7A . Here, the modified pivot frame  113  (secured to the snowshoe frame, not shown, in a manner as described above) has a pair of upstanding pivot ears  114  to pivotally support a foot bed or foot box  116 . This pivotal connection provides for rotation about the roll axis, similar to what is described above, but in this case the spring biasing toward the normal position is achieved in a different way. One or more coiled torsion springs  118  are secured about the pivot pin or rivets  120 , so as to spring-bias the rotatable footbed or foot box  16  toward the centered position. One way of anchoring the ends of the spring  18  is to place them underneath each of a pair of frame-integral fingers  122  as shown in  FIGS. 8 and 8A . The center  124  of the coiled torsion spring  118  passes around the rivet  120 . On left or right tilting of the platform  116 , one end or the other of the spring  118  is deflected downwardly. 
     The footbed or foot box  116  may be provided with holes  126 , for access to the inner ends of the rivets  120  during manufacture. 
       FIGS. 9 and 9A  show schematically another embodiment of a two degrees of freedom binding according to the invention, similar in principle to  FIG. 8  but achieving the spring biasing force in a different way. In  FIG. 9  a pivot frame  130  is somewhat similar to the frame  113  in  FIG. 8 , and may be secured to the snowshoe frame in the same manner as in generally similar earlier described embodiments. The front of the snowshoe is again to the upper left in the drawing, as indicated by the direction arrow  132 . 
     In this form of the invention the footbed or foot box  134  is again mounted for roll-axis pivoting on pivot support ears  136  and  138  of the pivot frame. In this case, the foot box  134  has left and right spring mounts or connections  140 , to which coiled tension springs  142  are secured. The opposite ends of these springs are secured to spring mounts  144  on the pivot frame, as indicated in FIG.  9  and as shown in the transverse sectional view of FIG.  9 A. These tension springs are afforded movement by slots  146  in the pivot frame, and they are shown in a deflected position, at approximate maximum tipping of the footbed  134  relative to the snowshoe frame, in FIG.  9 A. It is seen from  FIG. 9 and 9A  that the tension springs  142  tend to return the snowshoe and boot platform or footbed  134  back to a normal position of alignment. 
       FIGS. 10 and 10A  show another variation on a construction similar to  FIGS. 6 through 9 , in which a footbed component  148  is again connected to a pivot frame  150 . Here, the spring action biasing the footbed  148  back to normal position along the roll axis is provided by leaf springs  152  integral with the footbed or boot platform  148 . The schematic transverse sectional view of  FIG. 10A  shows rotational deflection in one direction about the roll axis, in which the left leaf spring  152  is deflected and exerts a force tending to return the footbed  148  back to normal relationship with the pivot frame  150 . 
       FIGS. 11 ,  11 A and  11 B show another scheme for achieving the second degree of rotational freedom, utilizing a pivot frame  155  which has ends  156  adaptable for securing to a snowshoe frame in the same manner as described for  FIGS. 6-10 . In this form of the invention, a coiled torsion spring and metal wire unit  158  provides the spring-biasing force to return a footbed  160  back to normal position, generally parallel to the pivot frame  155 . The footbed  160  can have a stamped bridge  162  that is secured to the central area of the spring and metal wire component  158 . This could be by welding, for example. The spring/metal wire element  158  is in turn connected to the pivot frame  155 , and this can be via integral tabs  164  of the pivot frame that receive angled ends  166  of the metal wire element by.  FIGS. 11A and 11B  show undeflected and maximum deflected positions of the pivot frame  155  relative to the boot footbed  160 . The spring/metal wire element  158  actually supplies the pivot for the footbed, not requiring an additional pivot rod. In the maximum deflected position as in  FIG. 11B , the footbed edge engages against the pivot frame as a stop. 
       FIGS. 12-12B  show another form of apparatus for obtaining the second desired rotational degree of freedom. The front of the snowshoe is again upper left as indicated by the direction arrow  170 . The normal sagittal plane rotation (about the pitch axis) is achieved by a rod or pivot pin  172  extending across the snowshoe and connected to the frame. Pitch is controlled by an appropriate form of biasing spring or elastic element, not shown. The roll-axis freedom of movement is achieved in this case by elastomeric bushings  174  which engage against the vertical stem portion  176  of a generally T-shaped footbed  178 . The elastomeric bushings  174  can be replaced by steel compression springs if desired. The assembled unit is shown schematically in  FIGS. 12A and 12B , the first figure showing the footbed in undeflected position relative to the pivot rod  172  and the second figure showing full deflection to one side. The bushings (or springs)  174  make a sandwich with the planar footbed stem  176  and the elastomeric material is deformed elastically in  FIG. 12B , allowing side tipping or roll-axis rotation between the footbed and the pivot shaft  172 , which remains aligned with the snowshoe frame. As can be seen in  FIGS. 12 and 12B , the footbed  178  has slots  180  in left and right depending flanges  182 , and these are positioned to saddle the pivot rod  172 . Thus, the slots act as guides for the footbed member when rotating about the roll axis, and they prevent undesirable yaw axis rotation, i.e. rotation within the generally horizontal plane between the user&#39;s boot and the snowshoe. 
       FIGS. 13-13B  show another form of the invention for achieving footbed rotation about the pitch axis and the roll axis. In this arrangement, a bent torsion rod  185  provides for the usual pitch rotation, the rod having ends  186  journalled for rotation in bearing brackets  188  secured to the snowshoe, whether the snowshoe is formed of a frame with flexible decking or comprises a molded composite snowshoe. The rod  185  is fixed to a boot footbed  190  at a front or rear position, such as at points  192  and  193 . At points  194  at left and right, however, the footbed has an integral sleeve connected around the rod but not fixed to the rod. This allows some twisting of the rod to afford some rotation about the roll axis  196  when needed, as shown in the transverse sectional views of  FIGS. 13A and 13B .  FIG. 13A  shows the flat, undeflected position in which the entire rod and the footbed lie in approximately the same plane. In  FIG. 13B  the snowshoe  198  has been placed on uneven or sloping terrain, such as in a sidehill condition, and the snowshoe has tipped relative to the footbed  190 . The rod  185  has twisted so as to allow the snowshoe&#39;s bearing bracket  188  to move downwardly while still being journalled onto the rod end  186 . 
       FIGS. 14-14B  show another variation which is in theory quite similar to the embodiment of FIG.  12 . In  FIG. 14  the front of the snowshoe is to the lower right, as indicated by the arrow  200 . A front claw and footbed  202  is secured on a pivot rod  204  which provides the normal sagittal-plane rotation (about the pitch axis), this rod being secured to the snowshoe for rotation and being biased toward normal in a manner as described above. The front claw/footbed assembly has integral side members  206  which include slots  208 , these members also serving as claws in a preferred embodiment. As in the arrangement of  FIG. 12 , the slots  208  ride over the rod  204  and provide a guide for roll-axis rotation, also preventing vertical-axis (yaw) rotation. A stretchable membrane comprising an elastomeric pad  210  is assembled below the pivot rod  204  as shown in the exploded view of FIG.  14  and also shown in the schematic transverse elevation views of  FIGS. 14A and 14B . Rivets  212  and rivet backing washers  214  secure this assembly together in a sandwiched arrangement.  FIGS. 14A and 14B  show that when roll-axis rotation occurs, the elastomeric pad  210  provides flexibility while still biasing the assembly back to normal position, thus the rod  204  (and snowshoe) is allowed to tip relative to the footbed  202 . 
       FIGS. 15-15C  show another form of the invention and a different theory of pivoting.  FIG. 15C  shows a foot  220  and indicates the most desirable location for roll-axis pivoting, i.e. about a pivot axis  222  located approximately at the ankle. This is for maximum comfort and safety and minimum stress to the snowshoe user. This desired or theoretical pivot axis  222  is also seen in  FIGS. 15A and 15B . In  FIG. 15  a pitch-axis rotation member  224  somewhat similar to the pivot frames shown in earlier embodiments is secured for rotation on the snowshoe, via ends  226  of this component. The typical sagittal plane rotation is achieved in this way, and can be biased back to zero position by springs or elastomeric members. In this case, however, the roll-axis rotation is achieved via a footbed  227  having an arcuate bottom surface  228 , for sliding or ball-bearing rotation in a concave arcuate saddle or recess  230  formed in the cross member  224 . A bearing race can be provided at  232 . To secure the footbed  226  to the cross member  224 , a bolt  234  and special, arcuate-bottomed nut  236  can be provided, to seat in an appropriately shaped recess  238  on the upper side of the footbed  226 . This provides for roll-axis pivoting about a high axis of rotation, approximately at the location  222  shown in  FIGS. 15A and 15B , indicating normal position and sidehill position. Bias back to the zero position is not shown but could be achieved with springs. 
       FIGS. 16-16B  show another arrangement for providing a high axis of roll rotation, following the same theory as in FIG.  15 . Again, the front of the snowshoe is down into the right in  FIG. 16. A  footbed frame  240  is connected to a frontal rotation frame  242 , and this can be via rivets or bolts and nuts  244 ,  246 . The user&#39;s boot is placed on the footbed  240  and, as shown in  FIGS. 16A and 16B , the snowshoe is permitted to assume a tipped position for sidehill situations. A transverse rod or cross number  248 , fixed to and a part of the frontal rotation plane  242 , provides the typical pitch-axis rotation, in a manner similar to that discussed above. This snowshoe assembly thus provides for two degrees of rotational freedom with maximum comfort and safety to the user. 
       FIG. 17  shows the two desired degrees of freedom achieved in a different way. Here, a special snowshoe frame  250  is deformable due to inserted rotational connections at  252  and  254 . These connections can include torsion bars as connectors, such that the aggregate snowshoe frame assembly is urged back to the normal position shown in  FIG. 17. A  footbed  256  is secured to this snowshoe frame via a rotational cross member or binding straps  258 , preferably providing the usual pitch rotation. When the user walks on normal, flat terrain, the snowshoe frame remains essentially in the normal position as shown in the front elevation schematic of FIG.  17 A. The user&#39;s boot  260  stays essentially parallel to the terrain and to the snowshoe. However, in  FIG. 17B  the user has encountered a sidehill situation, and the pivoted nature of the snowshoe frame allows the footbed to assume an angular position relative to the snowshoe and to the terrain. As indicated in these schematics, the footbed  256  is allowed pivoting movement at its connections at  262  to the frame, such as is permitted by binding straps  258 . Thus, the snowshoe frame deflects and elastically deforms as indicated schematically in  FIG. 17B , and this is reversed for the opposite sidehill situation. 
       FIGS. 18-28  show further embodiments of the invention for achieving two degrees of rotational freedom in a snowshoe binding. 
       FIGS. 18-20  show a molded composite snowshoe  300 , molded of a plastic material with fiber filling.  FIGS. 18-20  are somewhat schematic, not showing all fasteners involved in order to reveal important components. 
     As shown in  FIG. 18 , the molded composite snowshoe  300  has a pair of terrain engaging rails  302  that are insert molded into the plastic material. These rails are metal, preferably of steel, such as stainless steel, and have a plurality of points  304  which act as teeth to engage the terrain. The rails may have a scalloped shape such that between the points  304  the shape of the rail bottom undulates in a curving fashion as shown at  306 . 
     The metal rails  302  preferably have holes towards their upper sides, and these holes may be oval in shape, for increasing the bond with the plastic snowshoe molding by allowing the molten plastic material to flow through the holes. These holes are completely buried in the plastic and are not seen in the figures. 
     An important feature of the rails  302  is that they are curved. Each rail, as shown, has at least one curve, preferably curving inwardly toward the other rail and then back outwardly as shown in FIG.  18 . In the illustrated embodiment the both ends of the rails have a short reverse curve just before the forward termination point of the rail. The main curvature in the rails is important for providing fore and aft traction on hard snow or icy terrain, in addition to lateral traction and torsional traction. In addition, the curving rails provide torsional rigidity along the longitudinal axis, resisting warpage about this axis. 
       FIGS. 18 and 20  show that the metal rails may also serve the purpose of providing a pivot attachment support for a heel lift  308 . The heel lift, which is to lift the user&#39;s boot heel for steep uphill terrain, has inwardly bent ends  310  ( FIG. 18 ) which pass through holes in the metal rails to provide the pivot support mounting. As is known, such a heel lift is normally flattened against the snowshoe deck (rotated clockwise as seen in FIG.  20 ), but is flipped up into the position shown in  FIG. 20  when needed for steep terrain. The lift  308  can be moved forward to an “over center” position as shown, with elbows  312  resting against the snowshoe surface, to remain stable in the lifted position. 
       FIGS. 18-20  also show an important feature of the invention whereby a footbed  314  with metal front claw  316  is suspended by cables  318  secured to the claw and to the molded snowshoe body. The flexible cable  318 , which can comprise aircraft cable, is secured to the front claw  316  in an appropriate sturdy and robust manner. As indicated in these drawings, the cable is preferably secured by fasteners through the illustrated holes  320  in the footbed. Fasteners  322  are shown in  FIG. 20 , but are omitted for clarity in  FIGS. 18 and 19 . 
     The cable binding suspension in  FIGS. 18-20  is in a “diamond” configuration, in which the two cables on each side are spread apart widest at their connection to the footbed, and come close together as they enter the plastic snowshoe body. The cables are under high tension, as they support the weight of the user. In  FIGS. 18-20 , each cable enters the sides of the snowshoe, preferably passing through holes in the metal rails  302 , in a spaced apart relationship as shown. A spacing may be only a few millimeters, or up to about one centimeter or somewhat wider. The purpose of the spacing, as just seen in  FIG. 19 , is to provide a spring-loaded bias to the angle of the footbed relative to the snowshoe binding, on the pitch axis. As in other snowshoes of Atlas Snowshoe Company, the footbed preferably is biased in pitch to a toe-downward position as shown, and this is achieved here by the orientation of the holes  324  and  326  through which the cable passes as it enters a spring enclosure  328  at each side. 
     As is seen from these drawings, the metal rails  302  provide considerable strength and rigidity for this cable binding arrangement, especially as the metal rails are insert molded into the plastic of the snowshoe body. 
     FIG.  21  and  FIG. 28  illustrate the principle of operation of the cable binding arrangement shown in  FIGS. 18-20 . These drawings show that the cables  318  pass through the holes  324  and  326  and, on the other side of a wall  330  (which in  FIGS. 18-20  is the rail  302 ), they are subjected to spring tensioning. At the holes  324 ,  326  the cables may pass through a cable guide or grommet  332  seen in  FIG. 19 , which may be of a tough and relatively low friction plastic material, or which could be of metal. The spring, as shown in  FIGS. 21 and 28 , preferably is a compression spring  334  (metal or elastomer), with the cables  318  passing through the coils of the spring  334  and being secured by an end connector, such as a cable crimp device  336  bearing against a washer  338 . In  FIG. 28  the footpad plate or base is schematically represented at  316 , with a different form of connection than what is represented in  FIGS. 18 and 19 . In  FIGS. 18 and 19  the spring  334  is shown as encased in a housing  328 , although this is optional. In addition, a different type of spring can be used, such as a tension spring, and this could be encased within the housing  328 . 
     As can be seen from  FIGS. 21 and 28 , the essentially triangular of cables  318  tends to resist any rotation of the binding in the horizontal plane, i.e. about the yaw axis.  FIG. 25  also schematically indicates this effect. Both cables A and B in  FIG. 25  are linked together behind the spring, and they connect to the footpad at spaced apart locations, so that such undesirable rotation is resisted. 
     The illustrated binding suspension provides for rotation in the roll direction about a generally centered longitudinal axis. This is an important feature for comfort, efficient use of the snowshoe on cycle terrain, and prevention of ankle injury. If the pivot point for roll-axis rotation were at left or right, the function would be quite different. Thus, if the binding footbed  314  had a hard bottom position at left and right, but each side were allowed to tip upwardly when needed for sidehill terrain under the influence of a spring, this would not be center-axis roll rotation and would not have the benefits of the invention. 
     It is also seen from  FIG. 21  that the holes  324 ,  326  through which the cables  318  pass can be spaced apart a greater distance to provide a more forceful return to the “zero” position of the footbed, since the farther these holes are separated the greater the cable-pulling force required to rotate the footbed in pitch. The holes can be aligned in an angled arrangement in the wall  330  to establish a bias pitch as discussed above, which may be in the range of roughly 10° to 30° with the binding footbed  314  toe-down relative to the snowshoe frame or body. 
       FIG. 22  shows a variation of  FIG. 21 , wherein the cables  318  pass through holes in the snowshoe body wall and then pass through an approximate 90° turn so that the springs  334  can be housed in a greater longitudinal space. This requires low-friction grommets, as at  342 , and low friction cable guards or pulleys as represented at  344 . Again, the compression spring  334  can be a metal coil spring or an elastomer spring. As noted above, the cables can be tensioned by a tension spring if desired, rather than a compression spring as shown. A tension spring must be anchored at a distant end from the cables, and thus tends to require somewhat more space. Such space is easily provided via an arrangement similar to  FIG. 22 , although a sufficiently wide spacing between walls  330  and  330   a  in  FIG. 22  can also accommodate tension springs. 
       FIG. 23  shows a variation of  FIG. 21  wherein the spring force is provided by the metal rails  302   a  themselves. The rails  302   a  can be cantilevered from their insert mold areas as shown, so that a predetermined length of the metal rails (which may be of a spring steel) extends forward freely to form the cantilever. These cantilever springs could also be cantilevered plastic members. 
       FIGS. 24A ,  24 B, and  24 C demonstrate the rotation of the cleat-footbed  314  about the central roll axis as discussed above. In  FIG. 24A , the cleat/footbed is shown schematically in a normal position, not on sidehill terrain. The springs  334  are somewhat compressed under the weight of the user bearing down on the cleat  314 , and the cables  318  are shown slightly angled, approximately equally. In  FIG. 24B  the user has entered sidehill terrain and the cleat/footbed  314  is shown rotated in the counterclockwise direction relative to the snowshoe frame. This rotation is shown to occur generally about a central axis  346 . If these are considered frontal views, the user has entered hillside terrain which slopes down to the user&#39;s left, the boot and cleat  314  remaining generally horizontal. 
       FIG. 24C  shows the reverse situation, with the user on opposite sidehill terrain. Again, the springs  334  compress to accommodate rotation of the cleat/footbed  314  about a generally central axis  346 . This roll rotation is also referred to as rotation within the frontal plane of the user. 
       FIG. 26  shows a variation in which the cables  318  are not in the “diamond” configuration described relative to  FIGS. 18  et seq., but are generally in an “X” configuration. In this case the springs  334   a , here shown as metal coil on elastomeric compression springs, are mounted on the cleat  316  of the footbed assembly  314 . The cable holes  348 ,  350  may be provided through the side cleats  352  of the front claw or cleat  316  as shown, with the compression spring mounted immediately behind. The spacing and angular aligned relationship of the holes  348 ,  350  establish the strength of bias towards a normal pitch position, and the angle of bias of that normal pitch position. Here, the cables spread apart as they reach the rails or body  354  of the snowshoe. The snowshoe schematically depicted in this form of invention can be a metal rail or tubular frame snowshoe which supports a stretched decking, since the springs need not be accommodated in the peripheral areas of the snowshoe. Even the above embodiments can be incorporated on a tubular frame or rail type of snowshoe (rather than a molded composite snowshoe), but the location of the springs in the snowshoe periphery then tends to be somewhat more awkward. 
     The configuration shown in  FIG. 26  can also be modified to a single-hole form of suspension, in which the holes  348 ,  350  are replaced by a single hole. As noted above, this does not provide for biasing the footpad to a prescribed “zero” pitch angle and allows essentially pre-rotation in pitch. The single-hole form is schematically indicated in FIG.  29 . 
       FIG. 27  shows another modification, again with the “X” configuration of cables  318 , but in this case with the springs located in the snowshoe body in a manner generally similar to FIG.  22 . The metal coil or elastomer compression springs  334 , or tension springs, are shown positioned between molded plastic rails  358  and  360  of a molded composite snowshoe, with the spring located just beyond a bracing wall  362 . Alternatively, the walls  358 ,  360  could be metal, as a part of a pair of metal rails  364 . Again, as in  FIG. 22 , this arrangement provides additional space in the longitudinal direction for the spring, although low friction cable guides or pulleys are required at  366  and  368 . 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to this preferred embodiment will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.