Abstract:
An improved skateboard or roller-skate truck is disclosed containing a novel yoke, base, grommet, wheel and bearing combination which delivers high precision steering, advanced steering control and more precise wheel alignment. The truck comprises a base plate and a yoke having a body portion with an aperture through it. There is a bearing member in the yoke next to the aperture. A post is mounted in the base plate and extends through the aperture in the yoke. A novel resilient grommet with a bearing surface on its face is mounted on the post and engages the bearing member in the yoke to restrict arcuate movements of the yoke. A novel wheel bearing is also disclosed which incorporates paired ball bearing casings with bell-shaped members on the outside of each casing slideably meeting each other inside a skate wheel where the bells self adjust the bearings to accommodate imperfections in the bearing seat levelness, bearing seat spacing, axle diameter and axle straightness.

Description:
[0001]    This application is a division of U.S. patent application Ser. No. 13/506,749 filed May 15, 2012, and pertains to assemblies for mounting wheels to the underside of a skateboard deck or roller skate boot. More specifically, it relates to a novel yoke, base, grommet, wheel and bearing combination in a skate truck to deliver high precision steering, advanced steering control, and more precise wheel alignment. Applicant claims, under 35 U.S.C. §§120, 121, the benefit of the priority of his parent application, the entire contents of which is incorporated herein by reference. 
     
    
       [0002]    Conventional skateboards and roller skates are equipped with steering mechanisms known as trucks. The trucks are mounted on the underside of the board or boot opposite to each other, one in the front and one in the rear. Each truck carries two wheels, one at each end of the truck&#39;s axle. Each wheel is fitted with two bearings that fit into pockets integrated into the wheel body. The bearings are separated by a small gap in the middle of the wheel. This gap may be filled with a metal spacer that partially stabilizes and aligns the bearings. 
         [0003]    Competition-level skateboarding and roller skating takes many forms, such as streetstyle, ramp riding, bowl riding, freestyle, slalom racing, and downhill racing. The equipment used by advanced skaters must meet exacting performance requirements. The truck or wheel chassis determines many of the most crucial performance characteristics. 
         [0004]    Skate trucks serve four main purposes: 1) to connect the wheels to the deck or boot; 2) to provide wide-ranging steering response, whereby the wheel axles swivel to create a finite turning radius when, by means of lateral weight shifts, the skater tilts the deck or boot about its longitudinal axis; 3) by means of a resilient suspension system, to smoothly and predictably resist the skater&#39;s varying lateral weight shifts, thus stabilizing linear rolling motion and providing control over the steering response; and 4) by means of the same resilient suspension system, to return the deck or boot to the neutral, non-turning position after the skater discontinues a lateral weight shift. Skate wheel bearings serve the obvious purpose of aligning the wheels to the axles and minimizing rolling resistance. 
         [0005]    Conventional skate trucks follow a basic design in which an axle pivots about an arm attached at one end to the center portion of the axle. The other end of this pivot arm is loosely fitted, at angles typically measuring 30° or 45°, into a plastic pivot cup mounted in a baseplate, thus forming a ball-like joint. A pair of doughnut-shaped grommets, usually made of rubber or urethane plastic of varying hardnesses, is mounted on a kingpin fixed at various angles in the baseplate on the side of the axle opposite the plastic cup. These grommets grasp a ring within, or extending from, the axle body so that the axle is suspended between the ball joint and the grommets. By adjusting the kingpin, the tension on the grommets may be increased or decreased, thereby varying the balance between turning stability and turning ease. Examples of this standard design are shown in U.S. Pat. No. 3,862,763, issued Jan. 28, 1975, to Gordon K. Ware; and in U.S. Pat. No. 4,109,925, issued Aug. 29, 1978 to Williams et al. 
         [0006]    In these standard designs, the kingpin and the grommets do not precisely stabilize the axle body about the steering axis theoretically defined by the pivot arm rotating inside the plastic cup. The angle of the pivot axis tends to deteriorate as the axle tilts, so that tight turns may be difficult to achieve. The axle body is also substantially free to waiver sideward in response to side loads encountered during turns or straight-ahead riding. Steering control, range and overall performance are thereby compromised. 
         [0007]    Furthermore, the standard design for the flexible plastic grommets results in poor steering control. Skaters control the tilt angle of the deck or boot, and thus the size of the turns they make, via lateral weight shifts of varying degree. Regardless of their hardness and no matter how they are adjusted, the conventional donut-shaped grommets do not offer an optimal or consistent pattern of resistance to such weight shifts. The result is that skaters cannot easily predict or measure how far to shift their weight to achieve turns of varying radii. 
         [0008]    Finally, the bearings used in standard skate wheels require tolerance between their inner races and the truck axles. This means they are free to sit or rock out of alignment if one or more of the following conditions are met: the wheel bearing seats are not perfectly level; the wheel bearing seats are not precisely spaced; the spacer between the bearings is not perfectly dimensioned; no bearing spacer is used; the axle nut is not properly tensioned; and/or axle diameter and straightness are flawed. Bearings manufactured with an extended inner race element have been repurposed for skate wheels to partially address the aforementioned issues. But even these can sit or rock out of alignment if: the wheel bearing seats are not perfectly level; the wheel bearing seats are not precisely spaced; the axle nut is not properly tensioned; and/or axle diameter and straightness are flawed. The alignment distortion that may result can compromise bearing performance and longevity, directly impacting wheel rolling speed and traction. 
       SUMMARY OF THE INVENTION 
       [0009]    In the present invention a high level of precision is provided to the trucks&#39; steering action. This is accomplished by way of a cylindrical bearing which is seamlessly integrated between the axle hanger, i.e., the yoke which supports the axle on which the truck&#39;s wheels are mounted at either end, and novel grommets. The “positive” or male portions of the cylindrical bearing are formed on the grommet seats of the axle body, and to save weight this portion is made hollow, like a tube, between the pivot tip and the axle (See  FIG. 5 ). The “negative” or female portions of the cylindrical bearing are formed on the surfaces of the two grommets that meet the hanger. These portions may be formed directly on the main body of the grommets, or else formed as separate elements, preferably using low friction material, and then joined to the main body of the grommets. The cylindrical bearing assembly constrains the axle body to pivot very precisely about the axis defined by the pivot arm and cup, with minimal up-down or side-to-side wavering. 
         [0010]    The present invention improves steering control of the skateboard with novel contouring and construction of the grommets. The grommets do not feature the round doughnut shape with flat faces that is typically seen. Rather, they incorporate a substantially hexagonal shape and significantly more material on the sides, as well as a taper from broader faces that meet the hanger to narrower faces that meet the base plate and the tension nut, respectively, of a truck assembly. In addition, the narrower faces have beveled sides and join to hard end caps. Throughout a skater&#39;s turning stroke, these beveled contours constrain compressive forces to act in a substantially perpendicular orientation along the grommets&#39; tapering outside walls, which are wider, taller and more voluminous compared to the side portions of conventional doughnut-shaped grommets. This ensures more direct and orderly resistance to compressive forces, as well as a longer compressive stroke and thus a larger steering range. In addition, the grommet&#39;s tapering sides minimize excessive “packing” of the flexible grommet material so as to create a more optimal steering control profile. 
         [0011]    Empty pockets may be optionally formed within the grommet assemblies, for example between the grommet body and the end caps or along the sides of the female bearing portion, to further refine the steering resistance profile. Resilient elements such as wave springs may be optionally molded within the grommet bodies to enhance rebound or energy return. Laterally-flexing features may be optionally added between the female bearing elements and the grommet bodies to provide controlled speed-sensitive steering, whereby the increased side loads encountered during high speed turns will gradually move the hangers into positions of less steer. 
         [0012]    The hard end cap joined to the lower grommet forms a mechanical lock with the contours of its seat on the base plate, thus eliminating the need for the separate round cap washer which is conventionally seen. The beveled interface between the hard end caps and the main grommet body also discourages the compressible material from flexing over the sides of its seat. 
         [0013]    The present invention also includes bearings with integral half-spacers ending in wide flat flanges which square up and self-stabilize inside the wheels. The wide flat flanges form a self-aligning system which corrects flaws in bearing seat levelness, bearing seat spacing, axle diameter and axle straightness. The superior alignment results in reduced friction within the bearings, longer bearing life, faster rolling, and enhanced wheel grip. 
         [0014]    Other objects and advantages of this invention will become apparent from a consideration of the following drawings and detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    For a more complete understanding of this invention, reference should be made to the accompanying drawings in which: 
           [0016]      FIG. 1  is a perspective view of the underside of a skateboard, partially broken away, including a depiction of the trucks of the present invention mounted on the underside of the board and movable to various positions including the positions shown in phantom; 
           [0017]      FIG. 2  is an elevational view of the skateboard shown in  FIG. 1  when a skateboarder&#39;s weight is moved toward the viewer of  FIG. 2  and showing the trucks with the foreground wheels moved closer to the deck of the skateboard to accomplish a right turn of the skateboard; 
           [0018]      FIG. 3  is a perspective view of the rear truck assembly shown in  FIGS. 1 and 2 , viewing the axle hanger upwardly from underneath the skateboard deck and showing the wheels of the truck aligned in a straight ahead position; 
           [0019]      FIG. 4  is an enlarged, exploded view of the rear truck assembly shown in  FIG. 3 , with the wheel portions partially broken away; 
           [0020]      FIG. 5  is an enlarged view, partially in perspective, of an assembled portion of the rear truck assembly shown in  FIG. 5  sectioned in the direction of the arrows  5 - 5  shown in  FIG. 4 ; 
           [0021]      FIG. 6  is an enlarged and partially assembled view of the base plate and grommet assembly of the rear truck assembly shown in  FIG. 4 , with the axle hanger assembly omitted; 
           [0022]      FIG. 7  is an exploded view of elements of the axle hanger assembly of the rear truck assembly shown in  FIG. 4 ; 
           [0023]      FIG. 8  is an exploded and perspective view of central portions of the rear truck assembly shown in  FIG. 4  engaged on a portion of the skateboard in a form of mounting which is an alternative to the form of mounting shown in  FIG. 1 ; 
           [0024]      FIG. 8A  is an enlarged portion of the rear truck assembly and skateboard portion shown in  FIG. 8 ; 
           [0025]      FIG. 9  is an enlarged and exploded view, partially broken away, of a wheel portion of the rear truck wheel assembly shown in  FIG. 4 ; 
           [0026]      FIG. 10  is a perspective view, partially broken away, of the wheel portion of the rear truck assembly shown in  FIG. 9  after the wheel portion has been assembled; 
           [0027]      FIG. 11  is an enlarged perspective view of the assembled bearings in the wheel portion shown in  FIG. 10 ; 
           [0028]      FIG. 12  is a perspective view of one of the wheel bearings shown in  FIG. 11 , broken away along the line  11 - 11  shown in  FIG. 11 ; 
           [0029]      FIG. 13  is a head on view of the broken-away face of the wheel bearing shown in  FIG. 12 ; and 
           [0030]      FIG. 14  is an elevational view of a roller skate with truck assemblies of the present invention mounted on the underside of the boot. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    In the drawings, one preferred embodiment of the invention is shown which is a skateboard  10  supported upon a pair of novel trucks  12  and  14 . While the preferred embodiment is a skateboard, it should be understood that the invention, including its various elements, will also be applicable to other rolling platform vehicles, such as a roller skate, which are powered by the rider, or by gravity, or by some combination thereof. Also, in the following paragraphs the truck  12  which is mounted toward the rear of the skateboard will be the truck principally described, but it will also be understood that the truck  14  which is mounted toward the front of the skateboard has an identical construction. 
         [0032]    However, the kingpin, or post,  20  on which the rear truck wheels  22  articulate has a longitudinal axis extending toward the rear end, or tail,  24  of the skateboard deck  26 . The kingpin, or post  30  in truck  14  mounted toward the front, or nose  32  of the skateboard has a longitudinal axis which extends toward the nose of the skateboard, and the front truck wheels  34  articulate on this post. The front and rear trucks,  14  and  12  respectively, are thus oppositely disposed to each other. 
         [0033]    As shown in  FIG. 1  in solid lines, wheels  22  and  34  of the rear truck  12  and front truck  14 , respectively, are in a straight-forward attitude when the axles, such as axle  36  of the rear truck  12 , are normal to a straight-line path incorporating the longitudinal axis of the skateboard  10 . The skateboarder&#39;s weight, if one were present on top of the skateboard, would normally be equally distributed toward both outer edges of the skateboard. As shown in phantom in  FIG. 1 , and in solid lines in  FIG. 2 , the trucks are turned to execute a right turn, with a skateboarder&#39;s weight predominantly on the side of the skateboard closest to the viewer in  FIG. 2 . With the skateboarder&#39;s weight thus distributed, the weight on the right side of the skateboard pressing downwardly in the direction of arrows  42  causes the wheels on the right side of the skateboard to move closer together. The nose of the board swings in an arc toward the right and the tail of the skateboard swings in an arc out to the left to orient the longitudinal axis of the skateboard deck in a right turn. 
         [0034]    Rear truck  12  is illustrated in  FIG. 3  in its assembled state with wheels  22  mounted on axle  36 . An exploded view of the truck  12  is shown in  FIG. 4 . A yoke, or hanger,  44  supports the axle  36  and connects the entire truck and wheel bearing assembly to the skateboard  10 . The body portion  46  of the yoke is supported on its pivot tip  50  in a pivot cup  52  which is, in turn housed in a pocket in one end of truck base plate  54 . The pivot cup is usually made of a lubricious plastic so that the pivot tip  50  can easily turn in a multitude of directions within it as the yoke  44  moves in an arcuate path about the base plate  54  to dispose the wheels  22  from one position to another. 
         [0035]    A first aperture  56  is formed in a central portion of the yoke  44 , spaced apart from the pivot tip  50 , so that the yoke  44  may also be mounted on the kingpin  20 . A cylindrical bearing member  60 , which is part of the yoke, is located adjacent to the first aperture. The size of the opening through that aperture is somewhat larger than the diameter of the kingpin, or post,  20  so that the yoke  44  is able to be fitted to the post during assembly and tilted in various attitudes while the yoke is maintained on the post. As shown in  FIG. 5 , the post  20  has a head portion  62  lodged in the base plate  54  and extends through the first aperture  56  to a distal end  64  where it is engaged by a tension nut  66 . Preferably, the tension nut is threadably engaged on the post&#39;s distal end  64  so that pressure on the elements of the yoke mounting assembly between the head of post  20  and its distal end  64  can be adjusted. 
         [0036]    A resilient first grommet  70  is engaged on the post  20  and the bearing member  60  on the underside of the yoke  44 . Grommet  70  has a first face  72  which is engaged on the cylindrical bearing member  60  adjacent the first aperture  56 . The outer surface of the bearing member  60  is cylindrical, and a cylindrically shaped groove bearing surface  73  in first face  72  is configured for complementary engagement with the cylindrical surface of the bearing member  60  in the yoke. Such an engagement precisely regulates and restricts the arcuate movement of the yoke. The bearing member is able to rotably slide through its interface with the first face of the grommet as the flat surface adjacent the bearing member  60  compresses the flat surface on the grommet adjacent the bearing groove  73 . 
         [0037]    In the body portion  46  of yoke  44  there is a recessed area  74  which has perimeter walls adjacent to the bearing member  60 . A collar section  76  of the first grommet is sized and configured to be fitted within those walls, and thus the walls of the recess grasp and hold the grommet in place. Preferably, the configuration of the walls forms a hexagonal recess, but similar configurations of the walls which intercept the collar section  76  may be used. 
         [0038]    The first grommet  70  has sides which taper from a larger end of the grommet adjacent to the first face  72  to a smaller end adjacent to a second face  80 . Those sides form a cone from the first face  72  at the larger end of the grommet which is configured for engagement with the bearing member  60  to the second face  80  at the smaller end of the grommet which is configured for proximate engagement with the tension nut  66 . Preferably the second face  80  is beveled. An end cap  82  which has a beveled surface  84  complementary to the second face  80  is interposed on post  20  between the grommet and the tension nut. The end cap  82  is also made of a harder material than grommet  70 , thus forming a hard, stable point of connection for the grommet at its second face  80 . The sides of the grommet are provided with external fissures  86 , and on the interior, as will shortly be described, the sides are internally hollow. 
         [0039]    These configurations of grommet  70  produce improved results for a skater. The contours of the beveled second face  80  constrain compressive forces to act in a substantially perpendicular orientation along the tapering outside walls, which are wider, taller and more voluminous compared to the side portions of conventional doughnut-shaped grommets. This insures more direct and orderly resistance to compressive forces, as well as a longer compressive stroke and thus a larger steering range. The tapering sides minimize excessive packing of the flexible grommet material so as to create a more optimal steering control profile. 
         [0040]    In the first face  72 , the cylindrical bearing member  60  may be formed directly on the main body of grommet  70 , or else formed as a separate element, preferably using low friction material, and then joined to the main body of the grommet. The cylindrical bearing assembly constrains yoke  44  to pivot very precisely about the axis defined by the pivot tip  50  and the pivot cup  52  with minimal up-down or side-to-side wavering. At the same time the cylindrical bearing assembly resists the increased side loads encountered during high-speed turns more progressively compared to conventional constructions. As side loads increase, the female bearing portion of the bearing in the first face, i.e., cylindrically shaped groove  73 , will gradually, rather than suddenly, flex under pressure from the male bearing portion in the yoke, i.e., cylindrical bearing member  60 , thereby allowing the yoke  44  to gradually move into positions of progressively slower steering, which is a desirable speed-sensitive steering effect. 
         [0041]    As shown particularly in  FIG. 5 , the cylindrical bearing member  60  includes a cylindrical side  60   a  across the aperture  56  from the first grommet  70 . Side  60   a  of the cylindrical bearing faces the base plate  54 . A second grommet  90 , which is quite similar to first grommet  70 , has a cylindrically shaped bearing surface  92  with which the second grommet engages the bearing surface  62   a . There is a recessed area  94  on the base plate side of the yoke into which a first face  96  of the second grommet fits in a non-rotating manner like the first grommet does on the other side of yoke  44 . When first face  96  is so inserted, the second grommet engages its bearing surface  92  with the bearing  60 . 
         [0042]    As shown in  FIGS. 4 and 6 , fissures  100  are formed on the outside walls of the second grommet, and the interiors of the grommet walls are hollowed out as at hollows  102 . A second face  104  on the second grommet, spaced apart from the second grommet&#39;s first face  96 , contains a plurality of first locking members  106 . An end cap  110 , which is disposed on post  20 , has a plurality of second locking members  112  arranged for complementary engagement with the first locking members  106 . The surfaces of the locking members may be ridged, and the surfaces  114  of the second grommet and  116  of the end cap  110  which engage each other beveled, as illustrated in  FIG. 6 . The end cap  110  also includes a face  118  opposite the second locking members  112  which can be fixed on the base plate  54 , as by incorporating a cup  120  which is arranged to match the configurations  122  on the base plate. 
         [0043]    The second grommet, like the first, incorporates a substantially hexagonal shape and significantly more material on the sides, as well as a taper from broader faces that meet the yoke to narrower faces that meet the base plate. The narrow second face has beveled sides that join the hard end cap. Throughout a skater&#39;s turning stroke, these beveled surfaces constrain compressive forces to act in a substantially perpendicular orientation along the second grommet&#39;s tapering walls, which are wider, taller and more voluminous compared to the side portions of conventional doughnut-shaped grommets. This insures more direct and orderly resistance to compressive forces, as well as a longer compressive stroke and thus a larger steering range. In addition, the grommet&#39;s tapering sides minimise packing of the flexible grommet material so as to create a more optimal steering control profile. 
         [0044]    The end cap  110  forms a mechanical lock with the contours of its seat on the base plate, thus eliminating any need for a separate round cap washer in an assembly that is conventionally seen. The beveled interface between the end cap and the second grommet body also discourages compressible material from flexing over the sides of its seat. 
         [0045]    A normal type of mounting for a truck such as truck  12  onto the underside of a skateboard is shown in  FIG. 1 , that is, to fasten the flanges  126  to the underside of deck  26  with screw or bolts inserted through the mounting holes  128  in the flanges. An alternative type of mounting is shown in  FIG. 8A , known as a “dropthrough” mounting. In that alternative, skateboard deck  132  is provided with an opening  134  which is arranged to fit the footprint of a truck structure beyond the flanges, i.e., a socket into which the superstructure of the truck fits. Truck  136  is mounted this way in  FIG. 8A . The superstructure  138  of the truck extends through the deck  132 , leaving flanges  140  on the other side, i.e., the top side of the deck. The truck is fastened in place using one or more bolts  142 . The deck-engaging surfaces of flanges  140  feature a convex contour to provide complementary engagement in the “dropthrough” mounting on the top surface of the deck, which normally has a concave contour. Small circular flat areas are preserved in the corners of the base plate&#39;s top surfaces to form stable seats for the mounting nuts when the truck is assembled onto the deck in the normal manner shown in  FIG. 1 . 
         [0046]    The wheel bearing assembly  150  shown in  FIGS. 9 through 13  is also an important part of the entire truck  12  for accomplishing smooth and improved control of a skateboard or roller-skate. In wheels  22 , shown in an enlarged, broken-away view in  FIG. 9 , first and second ball bearings are enclosed in casings  152  and  154 . On the first casing,  152 , there is a bell  156  on the exterior of the casing, and on the second casing  154  there is a second bell  160 . The bells  156  and  160  meet, as shown in  FIGS. 10 and 11 , when the casings  152  and  154  are assembled on axle  36  and disposed in their respective housings  164  and  166 . The bells  156  and  160  are slideably disposed on each other but may also be positively joined inside the wheel. 
         [0047]    More particularly, the wheel bearing assembly  150  for wheel  22  on axle  36  incorporates a first ball bearing casing  152  which has an inner casing portion  170  for bearing balls in a first race  172  and an extension section  174  beyond the first race. At the extremity of the extension section there is a first flange  176  which extends outwardly from axle  36  when the axle is disposed in channel  180  through the bearing. The second ball bearing casing  154  mirrors casing  152 , with an inner, second race and culminating in a flange beyond the second race which extends outwardly from axle  36 . The first and second flanges are disposed against each other within the wheel when they are assembled in their housings, or bearing seats, and disposed on axle  36 . When so disposed, the two flanges square up and self-stabilize. They form a self-aligning system which compensates for flaws in bearing seat levelness, bearing seat spacing, axle diameter and axle straightness. Thfs assembly results in reduced friction within the bearings, longer bearing life, faster rolling, and enhanced wheel grip. 
         [0048]    As shown in  FIG. 14 , the truck and wheel bearing assembly more particularly described above may be mounted on the underside of a roller-skate deck  184  to which a skater&#39;s boot  186  is affixed. Rear truck  12 A and front truck  14 A are illustrated with their rear and front wheels  22 A and  34 A, respectively, turned in the same attitude as the wheels illustrated in  FIG. 2  are turned beneath a skateboard. 
         [0049]    Those skilled in the art will readily see that while numerous detailed variations of the above-described embodiments if this invention may be made, the true scope of the invention is to be determined by the following claims