Patent Document

FIELD OF INVENTION  
         [0001]    The invention relates generally to sleds, and in particular, to steering a sled.  
         BACKGROUND  
         [0002]    When riding a sled down a hill, a rider is often required to make rapid turns. The conventional way to make a turn is to lean into the direction of the turn. This tends to increase frictional forces on one side of the sled so that the sled slowly turns in that direction.  
           [0003]    A difficulty arises when the sled is on an icy surface. Under these conditions, the coefficient of friction is so low that even when one leans into the turn, there is not enough friction to turn the sled. Moreover, the sled will tend to skid.  
         SUMMARY  
         [0004]    A sled incorporating the invention includes features for assisting the rider in turning the sled as the sled slides on a sliding surface.  
           [0005]    In one aspect, the sled includes a hull having a bow end and a stern end defining a longitudinal axis therebetween, a bottom portion having a bottom surface for contacting the sliding surface, and a side portion. A ledge integral extends in a direction parallel to the longitudinal axis and forms a discontinuity separating the bottom portion and the side portion.  
           [0006]    In some embodiments, the ledge includes an outboard edge extending along the longitudinal axis. This outboard can be reinforced with a sharpened metal edge.  
           [0007]    Other embodiments include those in which the ledge is oriented such that a vector normal to the ledge points toward the sliding surface, those in which the distance between the ledge and the bottom surface is constant along the ledge, and those in which the distance between the ledge and the bottom surface varies along the ledge.  
           [0008]    Among these latter embodiments are those in which the ledge includes a first end and a second end and the distance between the ledge and the bottom surface has a minimum between the first and second end. This includes embodiments in which the ledge defines an arc between the first end and the second end.  
           [0009]    Another aspect of the invention includes a method for controlling a sled by providing a ledge extending in a direction parallel to the longitudinal axis between a bottom portion and a side portion of a hull of the sled and causing the sled to move forward along a sliding surface. The sled is then made to bank so that the ledge engages the sliding surface, thereby changing the acceleration vector of the sled.  
           [0010]    These and other features and advantages of the invention will be apparent from the following detailed description and the figures, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIGS. 1 and 2 are top and side views of a hull for a sled;  
         [0012]    [0012]FIG. 3 is a cross-section of the hull shown in FIGS. 1 and 2;  
         [0013]    FIGS.  4 - 5  show a snow-brake mounted at the rear of the hull shown in FIGS.  1 - 3 ;  
         [0014]    [0014]FIG. 6 shows the snow-brake of FIGS. 4 and 5 in use;  
         [0015]    FIGS.  7 - 9  show a configuration for attaching a strap to the hull;  
         [0016]    [0016]FIG. 10 is a side view of a shin pad attached to the hull; and  
         [0017]    FIGS.  11 - 13  show different rib configurations and footprints for the shin pad of FIG. 8.  
         [0018]    [0018]FIG. 14 is a shin pad with ribs of varying height;  
         [0019]    [0019]FIG. 15 is a detail view of the shin pad of FIG. 14;  
         [0020]    [0020]FIG. 16 is an isometric view of the shin pad; and  
         [0021]    FIGS.  17 - 19  are views of an alternative hull.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    A downhill racing sled suitable for incorporating the features of the invention is described with particularity in Sellers, U.S. Pat. No. 4,666,171, the contents of which are herein incorporated by reference.  
         [0023]    As shown in FIGS.  1 - 3 , the sled includes a one-piece elongated molded hull  10 , preferably of vacuum-molded thermoplastic. The hull  10  has a bow or front-end, which is on the right as viewed in FIGS. 1 and 2, and a stern, or rear-end, which is on the left as viewed in FIGS. 1 and 2.  
         [0024]    The hull  10  presents a generally crescent-shaped profile, best seen in FIG. 2. An upper outwardly rolled molded edge of the hull  10  forms continuous railings or gunwales  12  surrounding the hull  10 . The gunwales  12  are raised at the bow to afford handholds and to protect against the intrusion of snow. The bottom of the hull  10  while generally curved in profile as shown in FIG. 2, includes certain features that enhance the sled&#39;s performance in deep snow.  
         [0025]    In FIG. 3, a cross-section of the hull  10  reveals a pair of generally flat parallel runners  14 ,  16  defined by molded downwardly protruding parallel ribs  18 ,  20 ,  22 ,  24 . Flat areas  26 ,  28  between the pairs of ribs act like wide skis to support the hull  10  as it moves through the snow. The ribs  18 ,  20 ,  22 ,  24  guide the hull  10  in a straight path and enhance tracking in packed snow.  
         [0026]    In FIG. 3, a pair of steps formed on the sides of the hull  10  define a pair of generally flat steering runners  44 A-B integral with the hull  10 . The steering runners  44 A-B define a downwardly extending arc, best seen in FIGS. 2 and 19, that is positioned high enough on the hull  10  so that when the hull  10  is level, the lowest points of both steering runners  44 A-B are above the level of the snow. However, when the rider banks the hull  10  beyond a critical angle, a sharp edge  46  of one steering runner  44 B contacts the snow. A downward component of the combined weight of the rider and sled is thus concentrated on the relatively small surface area of the edge  46 . The extent of this downward component, and hence the pressure on the edge  46 , depends on the extent to which the rider banks the hull  10 , as well as on the slope of the prevailing terrain.  
         [0027]    When the edge  46  contacts the snow, the force acting on the edge  46  generates drag. Since only one of the two steering runners  44 A-B is in contact with the snow at any time, this drag tends to turn the hull  10 . In this way, the steering runners  44 A-B assist the rider in executing sharp turns.  
         [0028]    The steering runners  44 A-B are of particular use in icy or crusty conditions. Under these conditions, the pressure exerted by the edge  46  of a steering runner  44 B enables it to bite into hard, icy surfaces. To further enhance this ability, a sharpened steel edge can be fastened onto the steering runner  44 A-B.  
         [0029]    Between the two runners  14  and  16 , a main central channel  30  extends longitudinally from the bow to the stern of the hull  10 , with progressively increasing depth as shown in FIGS. 2 and 3. The inside ribs  20  and  22  define the edges of the channel  30  and are slightly outwardly flared with gradually increasing spacing at both ends of the hull  10 . Inside the hull  10 , the molded channel  30  forms a large longitudinal central rib or keel-like hump  32  running down the center of the hull  10 . Because of the increasing depth of the snow channel  30  toward the rear of the hull  10 , the hump  32  becomes more pronounced toward the rear as shown in phantom in FIG. 2.  
         [0030]    An outwardly molded stern portion of the hull  10  extends into a rear-facing lip  48 , hereafter referred to as a “snow brake,” that rolls downward, as shown in FIGS. 4 and 5. The snow-brake  48 , which wraps around the stern portion of the hull  10 , includes a rear portion  50  and two side portions  52 A-B. The greatest extension of the snow-brake  48 , both rearward and downward, is at its rear portion  50 . The extent to which the snow-brake  48  projects outward and downward progressively decreases along the two side portions  52 A-B until the snow-brake  48  merges smoothly with the gunwale  12 .  
         [0031]    To use the snow-brake  48 , a rider leans back, as shown in FIG. 6. This causes the hull&#39;s bow to rise and its stern to sink. As the stern sinks, the rear portion  50  of the snow-brake  48  comes into contact with the snow and creates drag. The extent of this drag depends on the extent to which the stern sinks. This, in turn, is controlled by the extent to which the rider leans back.  
         [0032]    By leaning backward and sideways at the same time, the rider can cause one side of the hull  10  to sink and the other to rise. As one side sinks, the side portion of the snow-brake  48  comes into contact with the snow and also creates drag. This drag, which only acts on one side of the hull  10 , causes the hull  10  to turn swiftly in that direction. The snow-brake  48  can thus be used as a type of rudder as well as a brake.  
         [0033]    Optional gripping aids  54  can extend downward from the edges of the snow-brake to provide additional drag in icy conditions. These gripping aids can include teeth, as shown in FIGS.  17 - 19 , studs, or claws, as shown in FIG. 4. The gripping aids  54  can be integral with the snow-brake  48  or formed on a metal plate which is then attached or fastened to the rim of the snow-brake  48 .  
         [0034]    A side-mounted snow-brake  49  can also be mounted on the gunwale  12  at the side of the hull  10  as shown in FIG. 19. Such a snow-brake  49  is formed by outwardly rolling the gunwale  12  so that it projects outward and downward part-way toward the snow.  
         [0035]    The side-mounted snow-brake  49 , steering rails  44 A-B, and ribs  18 ,  24  collectively provide the rider with three progressively more effective ways to brake the sled when the sled is oriented in a direction having a component transverse to the fall line. The rider can lean sideways into a skid using the edges of the ribs  18 ,  24  for mild braking action, or the rider can lean further to engage the steering rails  44 A-B for more effective braking. If necessary, the rider can lean far enough to engage the side-mounted snow-brake  49  and bring the sled to an abrupt stop.  
         [0036]    Referring now to FIG. 7, side portions of the gunwale  12  are rolled outward to form a lip  56 . This lip  56  curls downward to form a rim portion  58  parallel to the hull  10  and separated therefrom by a gap  60 . An outboard hole  62  through the rim portion  58  is aligned with an inboard hole  64  through the hull  10 . Molded retaining walls  66 A-B, seem in isometric view in FIG. 8 flank the inboard hole  64  and extend outward from the hull  10 , part way across the gap  60 .  
         [0037]    A knee strap  36  has a grommet  68  at each of its two ends, one of which is shown in FIG. 9. To attach the knee strap  36  to the hull  10 , a grommet hole  70  defined by the grommet  60  is aligned with the inboard hole  64 . Then, a threaded {fraction (1/2)} inch bolt  72  is passed through the grommet hole  70  and through the inboard hole  64 . The bolt  72  is long enough to extend through the inboard hole  64  and all the way to the outboard hole  62 . Preferably, the bolt  72  extends approximately {fraction (3/16)} inches beyond the outboard hole  62  to ensure adequate support by the edge of the outboard hole  62 .  
         [0038]    A nut  74  is then threaded onto the bolt  72  to secure the bolt  72  to the hull  10 . When the nut  74  is fully tightened, it comes to rest snugly between the retaining fins  66 A-B, as shown in FIG. 8. The retaining fins  66 A-B thus limit rotation of the nut  74  in response to torque transmitted by the strap  36 . By doing so, the retaining fins  66 A-B reduce the likelihood that the nut  74  will loosen during use.  
         [0039]    Because of its strength, metal is typically used for making the nut  74  and bolt  72 . However, other materials such as plastic can be used.  
         [0040]    A shear force exerted on the strap  36  is transmitted to the hull  10  by the bolt  72 . However, the hull  10  supports the bolt  72  at two different points, namely at the edge of the inboard hole  64  and also at the edge of the outboard hole  62 . As a result, the strap-anchoring configuration shown in FIGS.  7 - 9  resists the tendency of the bolt  72  to pivot about a single support in response to a shear force. It does so by resisting shear force using shear resistance provided by the hull  10  at two different support points.  
         [0041]    By concealing the nut  74  and bolt  72  from view, the rim portion  58  of the lip provides the hull  10  with a more attractive and streamlined appearance. This appearance can be enhanced by coloring the end of the bolt  72  or by extending the end of the bolt  72  slightly beyond the rim portion  58  so it can be capped.  
         [0042]    In addition, by covering the nut  74  and bolt  72 , the rim portion  58  also prevents the nut  74  and bolt  72  from snagging on nearby objects, such as the rider&#39;s clothing.  
         [0043]    Referring back to FIG. 1, a pair of optional contoured shin pads  40  are used in combination with the knee strap  36  to maintain the axial position of the rider constant relative to the hull  10 .  
         [0044]    A shin pad  40 , a cross-section of which is shown in FIG. 14, is a unitary structure having a raised front portion that functions as a knee stop  76  and a raised back portion that functions as a foot stop  78 . Between the foot stop  78  and the knee stop  76  is a ribbed portion  80  having transverse ribs  82  for gripping the rider&#39;s shin. A typical rib  82  has a vertical face that faces the rear of the hull  10  and a curved face that faces the front of the hull  10 . In one embodiment, shown in FIG. 15, the heights of the ribs  82  vary to conform to the radius of curvature of the rider&#39;s shin. FIG. 16 shows an isometric view of the shin pad  40 . The dimensions given in FIGS.  15 - 16  are selected to conform to typical adult dimensions (in inches).  
         [0045]    The shin pad  40  slopes downward from the foot stop  78  to the front end of the ribbed portion  80 . Past the front end of the ribbed portion  80 , the shin pad  40  slopes upward to form the knee stop  76 .  
         [0046]    When a rider kneels on the shin pad  40 , as shown in FIG. 10, the rider&#39;s knee rests on the knee stop  76  and the front of the rider&#39;s foot rests on the foot stop  78 . During sudden deceleration of the sled, deformation of the knee stop  76  and foot stop  78  absorb the rider&#39;s momentum and thereby restrain continued forward motion of the rider.  
         [0047]    In response to the rider&#39;s weight, the ribs  82  deform. In their deformed state, the ribs  82  exert a force that tends to restore them to their undeformed state. This restoring force, when transmitted to the rider&#39;s shin, tends to grip the shin. Although the restoring force exerted by any one rib  82  is small, the collective restoring force exerted by all the ribs  82  is significant.  
         [0048]    The gripping force exerted by the rib  82  is further enhanced by providing the rib  82  with a vertical leading face  84 . In a rib  82  having a sloped leading face, the rider&#39;s shin has a tendency to slide forward over the rib  82 . In contrast, the vertical leading face  84  of each rib  82  tends to resist this forward-sliding tendency of the shin.  
         [0049]    The gripping force exerted by each rib  82  depends, in part, on the extent of its deformation. This, in turn, depends in part on the force exerted by the shin on the rib  82 . This force has two components: one arising from the rider&#39;s own weight and another arising from any deceleration of the sled. Thus, one advantage of the shin pad  40  is that this gripping force increases momentarily when the sled rapidly decelerates or comes to a sudden stop.  
         [0050]    Other embodiments of the shin pad  40  include those having ribs  82  that extend in directions other than the transverse direction. For example, the shin pad  40  may include ribs  82  oriented in a herring-bone pattern, as shown in FIG. 11, or diagonally, as shown in FIG. 12. These configurations provide resistance to tangential forces that result when the sled changes turns. In addition, the shin pad  40  can have an oval footprint, as shown in FIGS. 11 and 12, or a rectangular footprint, as shown in FIG. 13.  
         [0051]    The shin pad  40  is made of a resilient material such as a closed cell foam. However, it can also be made of a molded plastic The material used to make the shin pad  40  should be one that enables the ribs  82  to deform in response to the rider&#39;s weight but to resist deformation enough to grip the rider&#39;s shin. In addition, the material should be sufficiently resilient to return to its original shape even after repeated and sustained deformation.  
         [0052]    When manufactured out of closed cell foam, the ribs  82  of the shin pad  40  are cut out with a heated wire. However, other methods of cutting the ribs  82  of the shin pad  40 , for example, with high-pressure water jets, can also be used. In other embodiments, the shin pad  40  can be molded out of a suitably resilient plastic.  
         [0053]    The invention has been described in the context of a specific recreational racing sled. However, the various features of the invention can readily be incorporated other types of recreational sleds.

Technology Category: 7