Abstract:
A molded or plastic composite snowshoe is formed of two assembled sections, in a way that imparts flexibility to the snowshoe, allowing some degree of torsional twisting or warping flexibility so that the snowshoe adapts to uneven terrain. In a principal embodiment the molded snowshoe is divided into forward and aft sections along a line slightly behind the nose area and near the pivot axis in the case of a pitch-pivoting binding. Joints between sections are in narrow rims at left and right, at opposed sides of a large central opening for the crampon/binding and boot. The joints are designed to securely hold the forward and aft molded sections together but to allow a degree of torsion between them when needed. Steel structural traction rails extend across the joints but are constructed and secured to the snowshoe sections in a manner that preserves the desired flexibility.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns snowshoes, particularly snowshoes of molded plastic or composite material, and the invention encompasses a molded snowshoe with improved ability to adapt to uneven terrain. 
     Traction and stability on a varied terrain are valuable attributes for a snowshoe. One way to allow enhanced traction and stability is to provide a snowshoe structure which can adapt to various surface contours to effect better contact with the surface, and thus enhanced traction and stability. This invention provides a structure with improved ability to adapt to and make contact with the snow or ice surface on which the snowshoe is used. 
     Typical snowshoes provide flotation, traction and stability by the incorporation of flotation means (primarily a deck), traction means (cleats or rails), and a means to attach the user&#39;s foot to a relatively rigid structure (a boot binding). 
     The traditional frame based snowshoe has a peripheral framed structure that is essentially rigid. This is required to suspend and support the traditional flotation surfaces that consist of flexible members such as rawhide strips, coated fabrics or thin plastic sheets. Traction elements are attached to the underside of this construction for improved traction on ice and snow surfaces. A binding of some type is attached to the structure to receive the user&#39;s foot. The traditional framed snowshoe construction thus teaches the need for a rigid frame surrounding the periphery of the snowshoe, and a flexible decking material suspended within the frame. The flexible decking is inherently too flexible to bear the flotation loads of the snowshoe without the support of the peripheral frame. 
     It can be advantageous with such a construction to allow the traction elements attached to the snowshoe structure to conform to the contours of the snow and ice surface by providing some level of relative flexibility or suspension from the generally rigid structure of the snowshoe. The flexible decking snowshoe suspends some traction elements on the deck, and suspends the binding (with toe cleat) somewhat, and thus adapts to some extent to the terrain. Other prior approaches using this concept include the use of various suspension systems such as in K2 Snowshoes U.S. Pat. No. 6,898,874, which provides adaptation to side terrain. There have been other approaches for suspending the snowshoe binding and the traction elements attached to the underside of the snowshoe bindings, which allow some degree of relative motion or flexibility between the overall snowshoe structure and the binding with its attached traction means. 
     More recently, constructions of snowshoes have been developed that consist of flotation surfaces formed of materials such as injection molded plastic, of a thickness and stiffness such as not to require peripheral frames to help resist and support the flotation loads associated with snowshoeing. One such prior art example can be found in the MSR Denali model snowshoe made of a molded one piece surface comprising the flotation surface of the snowshoe. Additional structure is provided in the form of two steel rails running longitudinally along the lower side of the molded decking surface, which also serve as traction elements. This prior art teaches the importance of structural rigidity through the combination of the structure of the longitudinal metal rails, along with structural channels molded into the decking structure of the snowshoe. See, for example, MSR U.S. Pat. Nos. 5,469,643, 5,517,773 and 5,921,007. 
     In the described MSR snowshoe, the binding of the snowshoe was attached to the longitudinal traction rails in a pivoting fashion. A certain degree of structural flexibility of the overall structure is obtained by this arrangement. However, the structural rigidity of this construction is also somewhat limiting on the degree to which the structure can conform to the underlying contours. Further, the need to use one material for the entire deck surface for such constructions can be a limitation in the selection of materials to meet the various requirements of the snowshoe structure. 
     The above are examples of ways in which the prior art has achieved the required flotation and structure required of a snowshoe combined with contact and traction with the underlying terrain surface. 
     The prior art also discloses a compound deck snowshoe, with an additional piece of deck structure or “tail extender” that can be added or taken off the snowshoe body by the user, as a means to alter the degree of flotation of the snowshoe, as in U.S. Pat. Nos. 5,517,773 and 6,195,919; see also U.S. Pat. Nos. 6,006,453 and 6,226,899. While such prior art does disclose a deck comprised of two or more pieces, it does not teach any method for substantially affecting the overall structural flexibility of the snowshoe structure, for adaptation to terrain. Further, the loads that can be imparted into the second decking section in U.S. Pat. No. 6,195,919 are limited by the absence of any substantial structural member spanning the mating region. 
     There is a need for a molded or composite snowshoe that has a deck rigidity sufficient for the needed flotation while also affording a torsional (warping) flexibility that allows the traction elements or cleats on the snowshoe bottom to contact uneven terrain. 
     SUMMARY OF THE INVENTION 
     A molded snowshoe construction in accordance with the invention includes a decking surface constructed of a material and of such thickness that support from a peripheral frame is not needed. A typical such snowshoe decking can be formed of molded plastic materials of approximately 3 mm thickness, or molded fiber reinforced composite of somewhat lesser thickness. 
     The molded snowshoe of the invention is constructed in a way so as to allow the cleats or traction elements of the snowshoe to contact the underlying terrain surface contours even when the surface is uneven, greatly improving traction. This is achieved by improving the structural flexibility of the snowshoe by forming the deck of the molded snowshoe in two or more separate pieces connected together. These pieces are molded of materials and of a thickness such they are able to bear the flotation loads required by the snowshoe. Structural integrity of the snowshoe is obtained by the use of elongated structural members, such as metal rails on the snowshoe bottom, which extend continuously through a joint between the deck segments, but the design affords torsional flexibility of the snowshoe. 
     Preferably the multi-section deck structure is formed with a fore deck section and an aft deck section. The joint preferably is at two locations, both being narrow outer rims at left and right, adjacent to a large central opening in which the snowshoe binding is suspended. The sections are joined in these narrow regions in a way that allows for torsional flexibility of the snowshoe, improving flexibility to accommodate deformation so that the cleats or traction elements at the bottom of the snowshoe can better adapt to uneven terrain, to improve traction. The positioning of the joints is designed to allow conforming deformation in a way that will optimally adapt to terrain. 
     In a preferred embodiment two main longitudinal structural elements span the region where the two deck sections meet. These structural elements advantageously comprise metal rails extending through most of the length of the snowshoe and serving also as traction elements on the underside of the snowshoe. Further, the boot binding can be supported by the metal rails, which applies the load from the user directly to these elongated metal structural elements that also preferably serve as traction rails. 
     The compound molded deck structure of the invention has the further advantage that the fore deck and aft deck sections can be formed of materials with different properties, such that each section, and portions within each section (via thickness variation), can be tailored to achieve a degree of local flexibility which serves the objective of the overall structure. 
     Accordingly, it is among the objects of this invention to achieve in a molded snowshoe a better ability to adapt to uneven terrain and to make good traction with the terrain, while still maintaining the strength, needed flotation and structural integrity of a molded snowshoe. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a molded snowshoe body according to the invention, shown without binding. 
         FIG. 2  is a bottom view of a somewhat modified snowshoe body. 
         FIG. 3  is a perspective detail view showing one of a plurality of joints in the snowshoe body, between sections. 
         FIGS. 4 and 4A  are enlarged perspective views again showing a portion of the snowshoe body and a joint between the sections, partially separated in these views. The two views are from different angles. 
         FIG. 5  is a perspective detail view showing the same region of the snowshoe, revealing a metal with reinforcing rail, and with one of the snowshoe sections removed. 
         FIG. 6  is another perspective view, showing the same structure from an opposite side. 
         FIG. 7  is a side elevation view showing another form of joint between snowshoe body sections and rail sections. 
         FIG. 8  is a bottom view showing the construction of FIG.  7 . 
         FIG. 9  is a perspective view showing a different embodiment of a joint between snowshoe sections, according to the invention. 
         FIG. 10  is another view of the joint construction shown in  FIG. 9 . 
         FIG. 11  is a perspective view showing a snowshoe of the invention exhibiting torsional flexibility and deflection. 
         FIG. 12  is a detailed elevation view showing a pivoted connector of a crampon/binding assembly to a traction rail in the snowshoe. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a snowshoe body  10  of the invention, in one preferred form. The snowshoe body  10  is molded of plastic material, preferably injection molded of an uncrosslinked polymer such as polypropylene, nylon or urethane. The plastic may be without reinforcing fibers, or it can be reinforced if desired. A compression molded thermoset resin reinforced with fibers such as glass could be used. 
     In this form of the invention the snowshoe body has a large central opening  11  for a crampon/boot binding assembly, in this case a boot binding that includes a heel support area (as opposed to snowshoes that allow the boot heel to rest on a rear deck area, such as in  FIG. 2 ). As seen in the drawing, the snowshoe body has a fore section or fore deck  12  and an aft section or aft deck  14 , these being secured together at a joint comprised of left and right junctures or joints  16  and  18  in narrow outer rim regions  20  and  22  of the snowshoe body structure. At each joint connection  16 ,  18  the width of the narrow neck or rim may be about 1½″ (or between about 1″ and 2″), or each rim may have a width in the range of about 15% to 20% of the overall width of the snowshoe. A typical overall width of the snowshoe (at widest point) is about 8″; typical width of the opening is about 5¼″; typical overall snowshoe length is about 24″. 
     As the drawings indicate, the joint formed by the connections  16  and  18  preferably is behind a snowshoe nose portion  24  and generally in a region where a snowshoe binding (not shown) will be supported for pitch pivoting movement. 
       FIG. 1  also shows a traction rail  26  included on each side, preferably extending from the nose back to a snowshoe tail  28 . These rails  26  act as structural members as well, adding flexure strength, and are further discussed below. They can support the binding, such as by supporting a pivot shaft. 
       FIG. 2  shows a different snowshoe body  30 , with a smaller central opening  32  for a binding, not shown. In this design the user&#39;s boot will rest on the snowshoe deck, in a region generally indicated at  34 . This view shows the snowshoe bottom, including the metal traction rails  26  at each side. The rails may be sinuous in shape to accommodate the shape of the snowshoe, or they could be linear, based on snowshoe configuration. The sinuous shape helps in achieving traction. It is important that these metal rails extend through the joint connections  16   a  and  18   a  for strength and integrity of the snowshoe. They act as spars that take the load that bears on the snowshoe. The nose of this snowshoe is indicated at  24   a , and the tail at  28   a.    
       FIGS. 3 ,  4 ,  4 A and  5  show one preferred structure of a joint as at  16  or  18  in  FIG. 1 . All are viewed from the outside edge of the snowshoe.  FIG. 3  shows the joint  16  as secured together, revealing the metal traction rail  26  extending from the bottom of the snowshoe body.  FIG. 4  shows the joint  16  opened prior to full assembly, with the fore deck section  12  separated and spaced slightly away from the aft deck section  14 . The outside of the snowshoe is visible nearest in  FIG. 4 . As illustrated, the structural rail  26 , which is generally a vertically-disposed member, with traction teeth such as shown in  FIG. 1 , includes generally horizontal connecting flanges such as seen at  26   b  in the drawing. These are also visible in the embodiment in  FIG. 2 , shown with securement holes  26   c . These connection holes on the rail are not seen in  FIG. 4 , but mating fastener holes  36  and  38  are seen in the aft deck section  14  and fore deck section  12  in this narrow rim region where the joint  16  occurs. The fastener openings  36 ,  38  are shown with countersink recesses  36   a  and  38   a  for the heads of rivets, machine bolts or other fasteners. See also  FIGS. 4A ,  5  and  6 . 
       FIGS. 4 ,  4 A and  5  also show that the narrow connecting portions of the fore deck section  12  and the aft deck section  14  are formed with an overlapping joint for a secure connection. The overlapping joint construction includes an inner flange or ridge  40  that extends forward from the aft section, at a laterally inward, receded position as shown. This member, which is shaped and curved generally in accordance with the outer shape of the narrow region of the two sections  14  and  12 , fits into a complementarily shaped socket  42  formed inward of an outer edge flange  43 ; the socket  42  extends around this region of the fore section  12 , as illustrated particularly in  FIG. 4A , to form a tight joint. As seen in  FIG. 4A , this joint connection can include a further, inner connector flange  44  on the fore section  12 , to further overlap in the joint, just inside the flange  40  of the aft section  14 . Thus, the connected joint  16  is composed of three overlapping layers, a layer or ridge  40  protruding from the aft deck section  14  extending between two layers  43  and  44  in the fore deck section  12 . This produces a high integrity joint, but one which can allow some relative twisting motion at the joint. 
       FIGS. 5 and 6  show fastener holes  26   c  in the metal rail  26 , for receiving fasteners through the fastener holes  38  in the fore section  12  ( FIG. 5) and 36  in the aft deck section  14  ( FIG. 6 ). Rivets or machine bolts (not shown) pass through the fastener holes  36 ,  38  and through the rail holes  26   c  to secure the two deck sections to the rail  26  at the joint. The aft deck section  14  is shown in  FIG. 6 , along with the metal rail  26 , again viewed from the outside edge of the snowshoe. The traction edge  26   d  extends down at the inner side of its narrow rim at the joint, that is, adjacent to the central opening  11  in the snowshoe. Again, a fastener, not shown, extends through the fastener opening  36  and through the fastener hole  26   c  in the rail, the latter being below the hole  36  bit not seen in  FIG. 6 . 
       FIGS. 7 and 8  show a side view of a snowshoe  50  having a joint  52  between a fore snowshoe body section  54  and an aft snowshoe body section  56 . The joint  52  can be made generally as described above, with both fore and aft sections  54  and  56  being bolted or riveted to a metal structural rail  58  that also serves as a traction element, as shown, with teeth  60  extending downward toward terrain.  FIG. 8  (bottom plan) shows that the metal rail/traction element  58  has several horizontal flanges  58   b  for fasteners  62  to secure the rail member to the fore and aft molded plastic sections.  FIGS. 7 and 8  show a pin connection  64  that connects a footbed/crampon mounting  66  to the metal structural rail  58  to allow pivoting of the footbed/crampon assembly within a central opening of the snowshoe, such as the opening  11  or  32  shown in  FIG. 1  or  2 . 
       FIGS. 9 and 10  show another form of rail joint wherein the joint is made flexible through an angled connection. In this joint the two snowshoe sections  70  and  72  joined via obliquely angled horizontal deck joint edges  74  and  76 , as shown in both  FIGS. 9 and 10 , and via abutting vertical plates  78  and  80  that are integrally molded with the sections. In  FIG. 10  the vertical plates  78 ,  80  are shown abutted in contact, and they can be secured together by a fastener through those abutted plates (not shown). 
       FIG. 11  shows a snowshoe of the invention being subjected to torsion by a person applying a twisting moment, such that the forward end or nose  24  is twisted relative to the aft end  28 . The crampon/binding assembly  82  is seen in this view, pivotally connected to the traction rail at each side. In a preferred embodiment, a torsional force applied to the snowshoe by uneven terrain and from a user of average weight (150 to 170 pounds) will create an angular deflection of about 15° to 20° or more in the snowshoe, between forward and aft ends. As explained above, this is achieved through the joints that connect fore and aft sections, as well as by the material and thickness of material used. The structural traction rails allow this torsional flexibility while acting as load-bearing spars for flexure strength for the length of the snowshoe. 
       FIG. 12  shows schematically a part of the snowshoe including a portion of the molded deck rim  20 ,  22  and a structural traction rail  26 , secured to the underside of the deck. The drawing shows a metal portion  84  of the crampon/binding assembly  82 , where this crampon assembly is secured to the rail  26  via the pin connection  64 . The metal portion  84  extends away from the rail  26 , which is inward of the snowshoe (toward the viewer in  FIG. 12 ), as indicated by the sectioned region  86 . This drawing indicates one method for rotation-limiting the crampon/binding assembly. A tab  88 , which is fixed to the rail (which can be an extension of a protruding end  90  of the tab into a hole in the rail), co-acts with the pivoting crampon/binding structure  84  to allow rotation only through an arc as defined by an arcuate cutout area  92  in the metal piece  84 . 
     The joints  16 ,  18  provide for the torsional flexibility of the snowshoe in combination with the flexibility of the snowshoe molded deck sections themselves, a function of material and thickness and any reinforcing patterns molded into the deck. The two deck sections can be of different materials, not only for torsional flexibility or rigidity but to provide one section with higher strength or toughness requirements than the other. Properties can be tailored; colors can be different. 
     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 these preferred embodiments 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.