Patent Publication Number: US-2005127629-A1

Title: Skateboard Steering Assembly

Description:
BACKGROUND OF INVENTION  
      1. Field of the Invention  
      This invention relates to steering devices for skateboards, roller skates, inline skates, street luges and other recreational, professional and commercial devices which use traditional truck type steering apparatus.  
      2. Related Art  
      Existing skateboards typically utilize pivoting truck assemblies as shown in U.S. Pat. No. 5,853,182, Finkle, attached to a solid wood riding deck. The truck assemblies consists of a shaft, cups, elastomeric bushings, washers, mounting plates, a single axle, bearings, two elastomeric wheels and fasteners. The skateboard rider steers the skateboard by leaning and applying pressure to opposite lateral sides of the skateboard deck which in turn causes the truck assembly to pivot and rotate the single truck axle about a single axis perpendicular to the skateboard deck. While providing a fairly rugged and reliable assembly, truck assemblies currently suffer from a number of disadvantages including: 
          a) the turning ability of existing skateboards is very limited due to existing truck designs. Existing truck assemblies typically consist of two wheels attached to a single axle. This arrangement allows only small axle rotation resulting in very limited skateboard turning capability. To execute tight turns, the rider must perform the awkward maneuvers of forcing the back end of the skateboard down which lifts the forward truck assembly off the surface on which it is riding and rotating the skateboard about the rear truck assembly. Less experienced skateboard riders must sometimes stop the skateboard, lift the skateboard off the ground and reposition it in its new direction. This is especially true around very tight turns. While some improvement in skateboard turning capability is possible by changing the truck&#39;s elastomeric bushing material and shaft tightness, this improvement typically has the undesirable effect of causing skateboard wobble and instability.     b) existing skateboards have no provision to adjust steering response to the amount of angle and pressure the rider applies to the deck. For every degree of deck rotation the rider applies, a fixed amount of turning radius results. If for instance a rider wants very large changes in steering radii with relatively small changes in initial deck rotation and then smaller changes in steering as more deck rotation is applied, existing skateboards cannot satisfy this need. Existing skateboards provide only a fixed, linear steering output in relation to skateboard rider input.        

      3. Objects and Advantages  
      Advantages of this invention include: 
          a) to provide a truck assembly which permits very tight, small turning radius capability without the need to lift the forward truck assembly or the entire skateboard from the surface on which it is riding. To provide a truck assembly which maintains stability and eliminates wobble for all truck settings and adjustments.     b) to provide a truck assembly which permits variable and adjustable steering response. Adjustability can be utilized for instance to allow small deck rotations to provide large changes in skateboard steering radii or vice verse to allow large deck rotations to make small changes in steering radii.        

      Further objects and advantages of this invention will become apparent from a consideration of the drawings and ensuing description.  
     SUMMARY OF INVENTION  
      In accordance with the present invention, a skateboard steering assembly or truck is provided which has the characteristics of common automobile steering assemblies. The truck can use the automobile characteristics of steering axis inclination, caster, camber, pivot radius and Ackerman steering geometries. These characteristics provide enhanced turning and steering, stability and preferentially return to null skateboard position with no applied input forces.  
      The truck consists of a pivoting beam assembly attached to and rotating about a deck aligned longitudinal shaft which is attached to the skateboard deck. The pivoting of the deck by the skateboard rider rotates a cam or other linkage which forces a follower to optionally rotate a second cam which optionally forces a second follower. The first or second follower forces a tie rod to translate normal to the longitudinal shaft. A rack and pinion assembly may be used in place of the tie rod. The tie rod rotates independent wheel axle assemblies providing steering to the skateboard. The cam-follower(s) or other linkage (s) can be adjusted and replaced to provide variable output/input steering characteristics for the skateboard. Additional cam-follower(s) may be utilized in series and parallel to modify output/input characteristics. Gears or other linkages may be used in place of cams.  
      The truck also consists of specialized wheels which permit the axle pivot axis to be located within the wheel. This eliminates deck rotation in response to forces applied to the wheel assemblies. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  shows various aspects of the skateboard truck assembly with a deck attached for reference.  
       FIG. 2  shows various aspects of the skateboard truck assembly.  
       FIG. 3  shows the specialized wheel assembly.  
       FIG. 4  shows the follower-cam assembly.  
       FIG. 5  shows the tie rod assembly.  
       FIG. 6  shows the truck mounting block and first cam.  
       FIG. 7  shows the beam assembly.  
       FIG. 8  shows the axle assembly.  
       FIG. 9  shows the shaft.  
       FIG. 10  shows various aspects of a skateboard truck assembly which utilizes gears in place of cam-followers. 
    
    
     DETAILED DESCRIPTION  
      A preferred embodiment of the skateboard truck assembly of the present invention is illustrated in  FIG. 1  with the skateboard deck attached and  FIG. 2  perspective view with the skateboard deck not shown. The truck assembly consists of a mounting block  46 , a shaft  21  and a beam  26 . The mounting block and beam are attached to and allowed to rotate freely about the shaft. The skateboard rider pivots the block by applying pressure to the left side of the skateboard deck, to turn left and right to the right side of the skateboard deck to turn right. The mounting block contains a cam  22  in which a follower  29  rides. When the block is rotated in response to rider input the follower drives and rotates an optional second cam assembly  47  in which an optional second follower  24  rides. Rotation of the first or optional second cam assembly forces a translation in the first or optional second follower which is attached to a tie bar  27 . The tie bar may be attached to the first cam. The tie bar translates and is attached to a drive pin  FIG. 8, 39  on the left and right hand axle assemblies  40 . The drive pin rotates the axle assembly about pivot bearing axes  FIG. 8, 38 . In addition to the drive pin the axle assemblies contain an axle  28  on which a wheel  30  rides. The rotation of the axle assembly causes the wheels to rotate about the pivot bearing axes. Because the pivot bearings are located inside the wheel assembly, forces applied to the wheel assembly as the skateboard is ridden over rough surfaces are not translated into the truck assembly. The wheel contains an elastomeric tread  25 .  
       FIG. 3  illustrates the wheel assembly. The wheel assembly contains a pair of ball bearings assemblies  31 , elastomeric tread  25  and wheel  30 . The axle assembly  FIG. 8  is located inside the wheel assembly for torque balance. Forces applied to the wheel assembly as the skateboard is ridden over rough surfaces are not translated into the truck assembly or the skateboard deck. This results in a smooth ride for the skateboarder.  
       FIG. 4  depicts the first follower  29  cam  23  assembly. This assembly translates deck input rotation from the mounting block cam  22  into tie bar translation. This assembly also variably amplifies deck rotation into wheel rotation. The amplification can be used to produce very tight skateboard turning capability.  
       FIG. 5  illustrates the tie bar assembly. The tie bar  27  contains a cam follower  24  and two bearing holes  33  which attach to the drive pins of the axle assembly  FIG. 8, 39 . The tie bar translates in response to rotational inputs from the follower and drives the drive pins which rotate the axle assemblies and wheels.  
       FIG. 6  depicts the truck mounting block  46  and first cam  22 . The truck mounting block rigidly attaches to the skateboard deck and pivots about the shaft  21 ,  FIG. 9 . The shaft fits in the sleeve bearing  35 . The truck mounting block  46  also contains the driving cam  22  which drives the follower  29  of the cam assembly  23 ,  FIG. 4 .  
       FIG. 7  depicts the beam assembly  26  on which the axle assemblies  40 ,  FIG. 8  ride. The beam assembly contains a sleeve bearing  36  which contains and rotates around the shaft  21  as the skateboad rider rotates the deck about the shaft. The beam assembly also contains sleeve bearings  37  in which the axle assembly  40  bearing shaft  38  rotate.  
       FIG. 8  illustrates the axle assembly  40 . The axle assembly contains a drive pin  39  which attaches to the tie bar assembly,  FIG. 5 . The axle assembly contains a bearing shaft which mounts in the beam assembly sleeve bearings  38 ,  FIG. 7 . The axle assembly pivots in response to tie bar translation causing the wheel axles  28  to rotate. Axle rotation causes the skateboard to turn.  
       FIG. 9  depicts the shaft  21 . The shaft fits in the beam assembly,  FIG. 7 , sleeve bearing  36  and the truck mounting block,  FIG. 6  sleeve bearing  35 .  
       FIG. 10  illustrates an alternate approach which utilizes gears  41 ,  42 ,  43 ,  44 ,  45  in place of cams.