Abstract:
The center point of an ice skate rocker with respect to the plane of the skater&#39;s foot, in a skating position, is adjusted without changing the contour or profile of the skate blade. This is done by adjusting the angular position of the foot inside the skating boot with a shim placed under the heel or under the ball of the foot.

Description:
BACKGROUND OF INVENTION 
       [0001]    The present invention relates to improvements in ice skates such as used by skaters in hockey, figure skating and long-blade skating. 
         [0002]    Ice skating is achieved by a skater wearing a boot attached to a manufactured blade,  FIG. 1 . The blade is often contoured in two perpendicular planar directions. In the plane of principal motion (xy plane),  FIG. 2 , the blade generally has a large radius of curvature, generally called the rocker. In the plane perpendicular to the direction of principal motion (yz plane),  FIG. 3 , the blade has a small radius of curvature, generally called the radius-of-hollow,  FIG. 4 . The ratio of rocker to radius-of-hollow is generally in the range of 8 to 13 for figure skates, 10 to 18 for hockey skates or zero for longblade skates (flat radius of hollow). 
         [0003]    The blade is most often made from a metal. If the blade material is machinable, then the center of the rocker can be changed, relative to the foot position in the skating boot, by machining (“contouring”) the blade. Alternatively, a change of rocker center point can be achieved by repositioning the blade in the x-y plane relative to the boot. A change can be made based on the preference of the skater. The preference is generally based on the skater&#39;s anatomy and the skater&#39;s flexibility limitations: the more proficient the skater is, the more the skater has awareness of rocker center point. 
         [0004]    It would be desirable if the center of the rocker could be changed relative to the foot position without having to machine the blade or repositioning the blade relative to the foot. 
       SUMMARY OF INVENTION 
       [0005]    An object of this invention is to provide improvements in an ice skate which readily permit the center of the rocker relative to the foot position to be changed. 
         [0006]    A further object of this invention is to permit such shifting of the center of the rocker to be made in a simple low cost manner. 
         [0007]    The invention provides the ability to adjust the center point of the rocker with respect to the plane of the skater&#39;s foot, in a skating position, without changing the contour or profile of the skate blade to improve skating performance. This is done by adjusting the angular position of the foot inside the skating boot with a shim placed under the heel or under the ball of the foot. 
         [0008]    In a preferred practice of the invention the shim is readily insertable in and removable from the boot of the skate. 
     
    
     
       THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of an ice skate which could be used in accordance with this invention; 
           [0010]      FIG. 2  is a side elevational view of the ice skate shown in  FIG. 1 ; 
           [0011]      FIG. 3  is a rear elevational view of the ice skate shown in  FIGS. 2-3 ; 
           [0012]      FIG. 4  is an enlarged view of the detail for  FIG. 4  of  FIG. 3 ; 
           [0013]      FIG. 5  is a side elevational view in section of the ice skate shown in  FIGS. 1-4  in accordance with this invention; 
           [0014]      FIG. 5   a  is a top plan view showing a set of shims which may be used in accordance with this invention; 
           [0015]      FIG. 5   b  is a side elevational view of the shims shown in  FIG. 5   a;    
           [0016]      FIG. 5   c  is a side elevational view showing a pair of stacked shims of the type shown in  FIGS. 5   a  and  5   b;    
           [0017]      FIG. 6  is a geometrical showing of the relationships resulting from the use of a shim in an ice skate in accordance with this invention; 
           [0018]      FIG. 7  is a cross-sectional view in elevation along the mid-plane of an ice skate showing the use of a heel shim in accordance with this invention; 
           [0019]      FIG. 7   a  is an enlarged view of the detail for  FIG. 7   a  of  FIG. 7 ; 
           [0020]      FIG. 8  is a view similar to  FIG. 7  with a ball-of-foot shim in an ice skate in accordance with this invention; and 
           [0021]      FIG. 8   a  is an enlarged view of the detail for  FIG. 8   a  of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  is a perspective view of a skate  10  which may be used in the practice of this invention. As shown therein skate  10  includes a boot  12  having a blade holder  14  which mounts the blade  16  to the boot  12 . Skate  10  would be worn on one foot. A similar skate would be worn on the other foot. 
         [0023]    As shown in  FIG. 2  the blade  16  is contoured in its plane of principle motion (xy plane) to have a large radius of curvature  18  generally referred to as the rocker. 
         [0024]    As shown in  FIGS. 3-4  the blade  16  is also contoured in the yz plane perpendicular to the direction of principle motion. The blade  16  has a small radius of curvature  22  generally called the radius-of-hollow. 
         [0025]    The skate  10  illustrated in  FIGS. 1-4  and in other figures herein could take any known conventional form of construction and would include an inner sole at the bottom of the boot upon which the foot would be directly placed. In accordance with this invention the rocker center point with respect to the plane of the foot is shifted by inserting a shim on the inner sole at either the heel or the ball of the foot portions of the inner sole. 
         [0026]    Performing trigometric and geometric analyses shows that a radial line from the center of the rocker, perpendicular with respect to the foot, can be moved without actually machining the blade. The radial line can also be changed with a change of foot position relative to that of the blade in the xy plane: either transitionally along the blade in the x direction or rotationally about the z axis. These methods of changing the position of the rocker with respect to the foot are achieved without altering the blade. 
         [0027]    This invention allows the change of rocker center point with respect to the foot by a rotation of the foot plane in the z direction through the use of ball-of-foot shims or heel shims made of any suitable material (soft or hard, pliable or non-pliable). 
         [0028]      FIG. 5  illustrates a heel shim  24  removably placed on the inner sole  26  inside the boot  12 . The shim  24  functions to elevate or change the angle of the plane of the foot at the heel. Generally, as shown in  FIG. 5   a , shim  24  would have a shape that corresponds to the size and shape of the user&#39;s heel and would snuggly but removably fit in the heel portion of boot  12  on inner sole  26 . Any suitable thickness could be used to achieve the intended purpose. Preferably, the shim thickness of shim  24  and ball-of-foot shim  28  would be no greater than ½ inches thick and more preferably no greater than 3/16 inch thick. Other suitable thicknesses include 1/16 inch and 1/32 inch. The shim could also be as thin as 1/64 inch. Preferably, the shim is at least 1/16 inch thick and no greater than 3/16 inch. The shim thickness results in a corresponding elevation of the heel or ball of the foot.  FIG. 5   b  illustrates a single shim  24 . If the thickness of the single shim is not sufficient, two or more shims  24  of the same of differing thicknesses could be stacked atop each other to achieve the desired thickness, such as illustrated in  FIG. 5   c . Similarly,  FIGS. 5   a ,  5   b  and  5   c  illustrate corresponding ball-of-foot shims  28 . 
         [0029]    In the preferred practice of this invention the total shim thickness, whether singularly or stacked is no greater than 3/16 inch. Preferably the shim is flat in the xz plane and provides a uniform thickness throughout the xy plane. The invention could be practiced where the shims are “generally” flat and could include slight contours or tapers. The main objective is to elevate generally uniformly the entire heel or the entire ball of the foot in the xy plane. 
         [0030]      FIG. 6  illustrates the geometric considerations resulting in a shifting of the rocker center point with respect to the foot. In those discussions reference to plane of the foot is intended to mean a plane that is parallel to the transverse plane of the foot when a person is standing with feet parallel to the ground. When a person has a shim under the heel, then the plane of the foot would be defined by a single point and a line. The point is on the surface of the foot under the center of the heel. The line is on the surface of the foot underneath and coplanar to a line drawn between two joints: the first joint is between the first metatarsal and the big toe, the second joint is between the fourth metatarsal and the fourth toe. This line would be considered the “ball of the foot”. 
         [0031]    As shown in  FIG. 5   a , heel shim  24  is shaped to have a generally straight inner edge  23  which would extend transversely across the boot/inner sole. The inner edge connects to side edges  25  extending rearwardly and merging into an arcuate outer edge  27  which extends transversely across the boot/inner sole to conform to the size and shape of the rear heel end of the boot/inner sole. The ball-of-foot shim  28  would have a shape similar to that of heel shim  24  to conform to the size and shape of the front toe/ball of foot end of the boot/inner sole. Preferably shim  28  is shaped as shown in  FIG. 5   a  to have the arcuate front end  29  to support the toes and conform in size and shape to the front end of the boot/inner sole. Shim  28  would also have straight inner edge  31  and side edges  33 , 33 . This shape assures proper placement of shim  28  in boot  12 . 
         [0032]    Preferably, the heel shim  24  would have a length in the x direction which is greater than 20%, but less than 50% of the total length of the foot (or inner sole) measured along the line in a plane parallel to the sagittal plane of the foot. The ball-of-foot shim  28  would have a similar length. 
         [0033]    From the geometry of  FIG. 6  with further reference to  FIG. 5 , a heel lift from heel shim  24  would cause the radial line from the rocker center point with respect to the foot inside the skate boot, to move rearward, along the line of the plane of the foot in the skate boot, a distance of: 
         [0000]    
       
         
           
             
               
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         [0000]    where:
 
q n ≡distance, in the xy plane with heel shim  24 , between ball-of-foot  30  and radial line  32  of the rocker that is perpendicular to plane of foot  34  with a heel shim  24  (xz plane rotated through the angle φ (PSI))
 
q o ≡distance, in the xy plane, between ball-of-foot  30  and radial line  36  of rocker that is perpendicular to plane of foot (xz plane)  38  (with no shim)
 
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         [0034]    A ball-of-foot shim  28  would likewise have an equivalent movement, but in the opposite direction. The above equations would be valid if P (PSI) were negative. 
         [0035]    While the rocker radial lines were 90 degrees to the foot plane in  FIG. 6 , any rocker radial line making an angle PSI with the foot plane will shift in the same direction as shown in  FIGS. 7 ,  7   a ,  8  and  8   a . These rocker radial lines intersecting the foot planes with the angle PSI represent the normal force (pressure) felt by the skater. 
         [0036]      FIGS. 7 and 7A  illustrate a shifting of the radial line to the rocker center resulting from the use of a heel shim  24 . As shown therein, the foot plane  38  is illustrated where there is no shim. By inserting the heel shim  24 , the foot plane is then elevated at an angle to the position shown as foot plane  34 . As a result, the radial line  20  to the rocker center where there is no shim would be shifted to the location  44 . 
         [0037]      FIGS. 8 and 8A  similarly show how the radial line  20  to the rocker center is shifted forwardly to position  48  when a ball-of-foot shim  28  is used which results in the foot plane  38  (when there is no shim) being moved to the foot plane  46  with the shim  28 . Thus,  FIG. 7  shows that a radial line  20  from the rocker center point will shift backward to position  44  with a heel shim  24 , if the same angle is maintained between the plane of the foot and the radial line. Similarly,  FIG. 8  shows that a radial line  20  from the rocker center point will shift forward to position  48  with a ball-of-foot shim  28 , if the same angle is maintained between the plane of the foot and the radial line. 
         [0038]    The range of values for the heel or ball-of-foot lift and range of values for typical blade rockers make the thickness of the shims fit easily into most known skate configurations. 
         [0039]    The drawings illustrate and the corresponding description discusses a single skate  10 . In practice, the skater would wear such a skate on each foot. In the preferred practice of this invention if a heel shim  24  is worn in one skate, an identical heel shim would be worn in the other skate. Similarly, if a ball-of-foot shim  28  is worn in one skate, an identical shim  28  would be worn in the other skate. It is to be understood, however, that the invention can also be practiced where a shim in one skate differs in thickness from the shim in the other skate. The invention can also be practiced where a heel shim  24  is worn in one skate and a ball-of-foot shim  28  is worn in the other skate. Further, the invention could be practiced where a shim is worn in only one skate. As noted, the preferred practice is to have the same type of shim in each skate so that there is a uniform shifting of the rocker center line in both skates. 
         [0040]    The invention can be practiced in any manner by the use of some mechanical structure which would elevate the heel or the ball of the foot to adjust the foot plane angle. For example, it is not necessary to use a shim confined to the heel or to the ball of the foot area. Thus, an insert could be used in the skate boot extending beyond those areas and even extending the entire length of the foot. Such insert could have a raised portion at the heel or at the ball of the foot. The thickness of the raised portion might even be adjustable. With such insert, the raised portion would be considered as a shim. Other practices could utilize the boot, itself, to cause such elevation and change of foot angle. Thus, instead of having a removable insert or shim, an inflatable bladder could be provided at the heel or at the ball of the foot portion of the boot which would be inflated a suitable amount to cause the desired elevation and change in plane of the foot angle. It might even be possible to provide flaps hinged to the inside of the boot which could be pivoted downwardly to create an elevation. Another variation would be to provide a key or other actuating member accessible on the outside of the boot, which upon turning or manipulation would cause some form of elevation inside the boot in the area of the heel or the ball of the foot. All of these examples of elevations could be broadly considered as different forms of shims which result in an adjustment of the plane of the foot.