Patent Document

BACKGROUND OF THE INVENTION 
     The present invention relates to skateboards and in particular to a skateboard truck providing improved stability and ride. 
     Riding skateboards is a very popular recreational activity among young people. Participants in extreme sports events perform acrobatic maneuvers involving jumps, twists, and turns requiring great skill and athleticism. Other events involve high speed runs down hills where speeds have reach 80 miles per hour. 
     The skateboards are supported by wheels connected to the skateboard by trucks. Known trucks include a base plate which is attached to a skateboard deck and a hanger connected to the base plate and carrying wheels. The hanger includes a pivot which engages the base plate at an angle and a kingpin which sandwiches a ring portion of the hanger between kingpin bushings. The kingpin bushings allow limited motion of the hanger with respect to the base plate, and the angled pivot couples rolling the skateboard deck along a deck centerline into turning the hanger left and right to steer the skateboard. 
     Unfortunately, the kingpin bushings allow horizontal motion of the hanger with respect to the base plate which results in altering the geometry of the truck causing instabilities and inconsistent handling, especially at high speeds and in radical maneuvers. Additionally, the kingpin bushings carry most of the riders weight resulting in transfer of compression from the upper kingpin bushing to the lower kingpin bushing. When additional weight is applied to the truck, the transfer of compression changes, and the handling characteristics of the board change because the ride height and hanger pivot angle are determined by the compressed bottom bushing length, resulting in unpredictable turning. The maximum length of the kingpin bushings is also limited by the change in geometry experienced when the kingpin bushings are compressed, limiting a rider&#39;s ability to turn. 
     Thus a need is present for a more stable skateboard truck. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing a skateboard truck which maintains truck geometry. The truck includes a support pin including a cylindrical end slideably engaging a cylindrical passage in a base plate, and a ball end residing in a socket in a hanger. A support pin bushing under the cylindrical end is compressible and both carries some of a rider&#39;s weight and holds the ball end in the socket providing a second pivot to the truck. The second pivot eliminates horizontal play of the hanger thereby facilitating consistent compression of the kingpin bushings and improved stability of the skateboard. Support pin travel allows off-center kingpin bushing compression for steering and improves shock absorption. Eliminating horizontal play allows lengthened kingpin bushings and use of the entire height of the kingpin bushings. The combination of kingpin bushing preload, and weight carried by the support pin, tends to equalize the compression of the top and bottom kingpin bushings improving stability. 
     In accordance with one aspect of the invention, there is provided an improved skateboard truck having a support pin providing a second pivot. The additional pivot provides horizontal stability and maintains consistent truck geometry in turns. 
     In accordance with one aspect of the invention, there is provided an improved skateboard truck having a support pin carrying part of the rider&#39;s weight. The kingpin bushings generally carry most of the rider&#39;s weight. During a turn, additional force is applied to the kingpin bushings compressing the lower kingpin bushing. Such compression alters the truck geometry and reduces predictability. The support pin carries some of the weight otherwise carried by the lower kingpin bushing, thereby retaining truck geometry and predictable handling. Further, due to maintaining consistent the truck geometry, somewhat longer kingpin bushings may be used which provide a better feel of resistance to the rider while turning and shock absorption when landing a jump. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1A  is a front view of a known truck. 
         FIG. 1B  is a rear view of the known truck. 
         FIG. 1C  is a bottom view of the known truck. 
         FIG. 1D  is a side view of the known truck. 
         FIG. 2A  shows a skateboard deck leaned to a left side to turn. 
         FIG. 2B  shows the known skateboard truck reacting to leaning the deck to turn left. 
         FIG. 3A  shows a skateboard deck leaned to a right side to turn. 
         FIG. 3B  shows the known skateboard truck reacting to leaning the deck to turn right. 
         FIG. 4A  shows a first perspective view of a skateboard truck according to the present invention. 
         FIG. 4B  shows a second perspective view of the skateboard truck according to the present invention. 
         FIG. 4C  shows a front perspective view of the skateboard truck according to the present invention. 
         FIG. 5A  shows a first exploded view of the skateboard truck according to the present invention. 
         FIG. 5B  shows a second exploded view of the skateboard truck according to the present invention. 
         FIG. 6  shows a side view of a support pin and support pin bushing according to the present invention. 
         FIG. 7  is a cross-sectional view of the support pin and the support pin bushing according to the present invention taken along line  7 - 7  of  FIG. 6 . 
         FIG. 8A  is a side view of the support pin bushing according to the present invention. 
         FIG. 8B  is a top view of the support pin bushing according to the present invention. 
         FIG. 9A  shown a side view of the truck according to the present invention with no compression of the support pin bushing. 
         FIG. 9B  shown a side view of the truck according to the present invention with partial compression of the support pin bushing. 
         FIG. 9C  shown a side view of the truck according to the present invention with full compression of the support pin bushing. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     To provide better views of the truck according to the present invention, the truck is shown inverted. 
     A front view of a prior art skateboard  10  having a skateboard truck  16  attached to a skateboard deck  11  is shown in  FIG. 1A , a rearview of the skateboard  10  is shown in  FIG. 1B , a bottom view of the truck  16  is shown in  FIG. 1C , and is a side view of the truck  16  is shown in  FIG. 1D . The truck  16  includes a base plate  18  attached to the deck  11 , a hanger  22  pivotally engaging the base plate  18  at a pivot end  22   a , axles  24  reaching laterally from the hanger  22  for mounting the wheels  14 , and a kingpin  26  holding the hanger  22  in place. Two kingpin bushings  20  reside on the kingpin  26  and sandwich a ring portion  22   b  of the hanger  22 . The kingpin  26  may be tightened or loosened (or harder or softer bushings may be selected) to adjust the turning responsiveness of the skateboard  10 . The pivot end  22   a  of the hanger  22  is tilted at an angle A and thereby couples leaning the deck  11  to the left or right with turning the hanger  16  to steer the skateboard  10  to the left or right. 
     The skateboard deck  11  is shown leaned to a left side to turn left in  FIG. 2A  and skateboard truck  16  is shown reacting to the leaned deck to turn left in  FIG. 2B . The skateboard deck  11  is shown leaned to a right side to turn right in  FIG. 3A  and skateboard truck reacting to the leaned deck to turn right in  FIG. 3B . The skateboard  10  is thus turned to the left or right by leaning the deck  11  to the left or right respectively, the leaning coupled to the turning by the trucks  16 . 
     A first perspective view of a skateboard truck  30  according to the present invention is shown in  FIG. 4A , a second perspective view of the skateboard truck  30  is shown in  FIG. 4B , and front perspective view of the skateboard truck  30  is shown in  FIG. 4C . The truck  30  functions in a manner similar to the truck  16 , but includes a support pin  50  which adds significant stability to the truck  30 , maintains the geometry of the truck  30 , and softens the ride of the truck  30 . 
     A first exploded view of the skateboard truck  30  is shown in  FIG. 5A  and a second exploded view of the skateboard truck  30  is shown in  FIG. 5B . The skateboard truck  30  includes a pivot  59  and a king pin  38  similar to prior art skateboard trucks. The pivot  59  is preferably a cylindrical metal member having one end press fit into the hanger  22  and an opposite end residing in a rubber tube in the baseplate, thus allowing slight movement relative to the baseplate. As with prior art skateboard trucks, the pivot  59  is angled to couple leaning the deck to the left or right with turning the hanger  32  to steer the skateboard. An upper (or roadside) king pin bushing  36   a  and a lower (or deckside) king pin bushing  36   b  are carried by the kingpin  38  and sandwich the hanger  32 . 
     The support pin  50  has a hollow cylindrical end  50   b  which resides in a cylindrical support pin passage  58  in the base plate  34 , and a ball end  50   a  which cooperated with a support pin seat (or support cup)  54  which resides in a recess  56  in the hanger  32 . The support cup  54  is preferably made from polyoxymethylene plastic (for example Delrin® made by Dupont in Parkersburg, West Va., or a similar material and is removable. The ball end  50   a  is free to pivot in the seat  54  and remains in the seat  54  during normal riding to provide a second pivot for the hanger. The provision of a second pivot provide stability to the truck  30  and maintains the geometry of the truck  30 . 
     Preferably, the support pin  50  is parallel with the kingpin  38 , providing a stronger design. If the support pin  50  is not parallel to the kingpin  38 , when the support pin  50  travels up and down in the base plate  34  during riding, friction and force are generated on one side of the support pin ball end  50   a . The embodiment described herein maintains a parallel relationship between the kingpin  38  and support pin  50  for up to approximately 45 degrees of skateboard deck roll. 
     The kingpin bushings  36   a  and  36   b  carry the majority of the rider&#39;s weight. On conventional trucks, as a rider articulates (i.e., leans) the deck to turn, weight transfers to the lower kingpin bushing  36   b  and distorts the geometry of the truck because the ride height and pivot angle are determined by the compressed lower kingpin bushing  36   b  length, and the force of the bushing seat is pushing on the upper bushing  36   a  and kingpin washer/nut. The kingpin nut  40  is preferably a locknut having a plastic locking portion, and is generally tightened to at least partially engage the plastic locking portion with threads on the kingpin stud  38 . 
     The support pin  50  holds the truck geometry during the articulation by keeping the hanger  32 , kingpin bushings  36   a  and  36   b , and base aligned  34 . The support pin  50  also carries some of the force otherwise carried by the lower kingpin bushing  36   b  during articulation, allowing the truck  30  to retain a substantial amount of pivot angle (or ride height), due to the support pin  50  providing resistance to compression of the lower kingpin bushing  36   b . The redistribution of force to the support pin  50  allows consistent side to side compression on the kingpin bushings  36   a  and  36   b  and consistent handling. The support pin  50  preferably has about 0.13 inches of travel. 
     Kingpin bushings are characterized by size and compressibility. Compressibility is measured in the unit of durometers, where the higher the durometer, the harder the material. For example, car tires have a durometer of around 40 a while a golf ball is around 100 a. Conventional kingpin bushings range from 70 a to 95 a. Preferred kingpin bushings  36   a  and  36   b  appear harder to a rider as compared to conventional trucks because of the added resistance to compression from the support pin  50  on the hangar  32 . Since the hangar  32  experience less compression (i.e., moving closer to the base plate  34  and reducing ride height) due to the support pin  50 , more of the leaning of the deck is transferred into the turning instead of reducing ride height. This creates a more consistent and steady turn compared to conventional trucks which allows you to use a harder kingpin bushings  36   a  and  36   b.    
     Different size kingpin bushings  36   a  and  36   b  may be used to create desired feelings of rider articulation throughout a turn. The two most accepted kingpin bushing designs are cone bushings and barrel bushings. Cone bushings are easier to articulate with a matching durometer in direct comparison to barrel bushings. Barrel bushings provide more urethane cushion compared to cone bushings and are the most widely used bushing in downhill skateboarding, while in typical street skating, cone bushings are predominant in the market. The trucks  30  preferably include slightly taller barrel bushings  36   a  and  36   b , for example, 0.75 inches in height, compared to the conventional height of 0.65 inches. The slightly taller kingpin bushings  36   a  and  36   b  give a better feel of resistance while articulating as well as more shock absorption when the rider lands at the end of a jump. 
     A side view of a support pin  50  and support pin bushing  52  according to the present invention is shown in  FIG. 6  and a cross-sectional view of the support pin  50  and the support pin bushing  52  is shown in  FIG. 7 . The support pin  50  is preferably rigid and more preferably a rigid metal material. The support pin bushing  52  is compressible allowing the support pin  50  to be pressed into the support pin passage  58  when axial force is applied to the support pin  50 , and resiliently return to an original position when the force is removed. 
     A side view of the support pin bushing  52  according to the present invention is shown in  FIG. 8A  and a top view of the support pin bushing  52  is shown in  FIG. 8B . A support pin bushing  52  resides partially in a bushing cavity  60  (see  FIG. 5A ) in the hollow cylindrical end  50   b . The support pin bushing  52  is preferably a hollow rubber tube with one closed hemispherical end. Preferably, the support pin bushing  52  is hollow to allow some pneumatic resistance to support pin bushing compression. Initially, as the support pin  50  receives weight from the rider, and the support pin bushing  52  compresses as the support pin  50  advances into the base plate  34 . As pressure increases inside the support pin bushing  52 , the support pin bushing  52  expand against inside walls  64  of the support pin passage  60 . After the support pin bushing  52  has expanded to the walls  64 , the mechanical characteristics of the support pin bushing  52  allow the support pin bushing  52  to bottom out at the bottom of the support pin passage  60  and resist further compression. 
     The support pin bushing  52  is preferably about 0.62 inches long, has an outside diameter of about 0.26 inches, and an inside diameter of about 0.1 inches. The support pin bushing  52  is preferably made of rubber having a hardness rating of 65 durometers (i.e., 65 a). 
     The easier initial compression of the hollow support pin bushing  52 , followed by greater resistance to compression, provides a consistent feeling of resistance while articulating the trucks. This overall effect provides a non-ridged suspension system for the skateboard truck  30 . Various springs, solid plastic, and solid rubber were tested, but the hollow characteristics of the rubber support pin bushing  52  provided the desired result for the support pin  50 . 
     A side view of the truck  30  showing no compression of the support pin bushing  52  against a support pin passage base  58   a  is shown in  FIG. 9A , a side view of the truck  30  with partial compression of the support pin bushing  52  is shown in  FIG. 9B , and a side view of the truck  30  with full compression of the support pin bushing  52  is shown in  FIG. 9C . The support pin  50  can slide axially within the support pin passage  58 , but cannot pivot (i.e., cannot move side to side or front to rear) within the support pin passage  58 . The support pin bushing  52  transitions from a cylindrical shape to a bulb forming in the support pin passage  58  below the support pin bushing  52 . The kingpin is at an angle A 1  typically selected from 20, 20, 490, and 45 degree. 
     The compressibility of the support pin  50  and support pin bushing  52  were determined through testing different bushings to obtain the desired characteristics of the truck. The resulting compressibility of the support pin  50  and support pin bushing  52  may be characterized by a set of measurements: 
                                                           force on support    support pin            pin (in pounds)   compression (in inches)                                        0   0           2   0.03           4.5   0.06           9   0.09           18   0.12           26   0.13           42   0.135           95   0.137                        
where all values are approximate. The compression is non-linear and has a compression of about 0.006 inches per pound of force up to about 20 pounds of force, and about 0.0001 inches per pound of force beyond about 20 pounds of force.
 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.

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