Abstract:
A skateboard truck comprising a base attachable to the underside of a skateboard and an arm carried by the base and rotatable relative to the base about a first axis. An axle having a pair of wheels mounted at opposite ends thereof is carried by the arm and the axle is rotatable relative to the arm about a second axis. A spring-loaded linkage is operatively connected between the base and the arm for limiting the rotational motion of the arm and biasing the arm towards a center position aligned with the skateboard&#39;s direction of movement. The first and second axes provide pivoting of the skateboard in two dimensions.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to an improved truck for a skateboard, all-terrain board or scooter, and more particularly to a truck having two independently spring-loaded pivoting members.  
         BACKGROUND OF THE INVENTION  
         [0002]    Conventional skateboards utilize steering mechanisms known as trucks. Typically a truck is mounted near each end of the skateboard, and include a pair of wheels at each end of their axles. The trucks provide some steering response, whereby when a skaterboarder shifts weight laterally across the board the axle twists, causing the board to turn. The trucks also serve, by means of a suspension system, commonly urethane bushings, to resiliently resist the skater&#39;s lateral tilt of the deck, thus stabilizing the board, and returning it to its normal position when the turn is completed. This lateral stability is crucial for both distance riding and aerial tricks where a firm platform is desired. Current trucks must sacrifice their ability to turn for lateral stability, thus becoming stiff and unresponsive when tightened sufficiently. Conversely, loosening the trucks so the board can turn easily makes it dangerously wobbly, especially at higher speeds. Furthermore, even in optimal conditions, the rate of turn provided by conventional trucks is very little.  
           [0003]    Previous attempts have been made to design a truck with increased maneuverability. One method utilizes a truck having a trailing castor that provides the skateboard with a second axis of rotation is described in U.S. Pat. No. 5,522,620 to Pracas.  
           [0004]    In this prior art device, the truck comprises a conventional truck mounted to a pivotal member. The pivotal member is coupled to the nose of the deck about a bearing member which rotates along a plane parallel to the direction of motion. A pair of stop members are shown that limit the pivotal movement between two extreme positions. Further, a locking member may be engaged to stop any rotation, thus returning the truck to a conventional configuration.  
           [0005]    Although the &#39;620 device provides a second pivot, the lateral plane of pivotal rotation merely provides the front of the skateboard with a side to side movement. Because the axis of rotation is parallel to the direction of motion, lateral weight shifting does not bear any leverage upon the pivotal member when the arm is near the center of its range. Further when the pivotal member rotates towards its extreme positions, the skaters&#39; lateral weight imposes exponentially more leverage upon the member causing overturning and loss of control. Additionally, the &#39;620 device does not regulate the torsional movement of the trailing castor. A strong bias to center is desired when performing aerial tricks so as to provide a predictable and stable landing. Further, regulating the rotational movement by a spring system is also important to stabilize the truck at higher speeds.  
           [0006]    Accordingly, a need exists for an improved truck that provides the user with more control over the torsional movement of the pivoting member and being adjustable for users of varying needs.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides an improved skateboard truck which pivots about two axes and provides a combination of adjustable lateral stability and enhanced turning abilities. Generally speaking, a truck according to this invention comprises an axle having a pair of wheels mounted at opposite ends thereof. A shaft extends through the center of the axle and is secured thereto on the side of the axle distal from the point of securing the truck to a skateboard. The truck further includes a resilient bushing circumferentially mounted on the shaft on the side of the axle proximal to the point of securing the truck to the skateboard for providing a first pivot axis about the axle, and a swivel connected to the axle and adapted to be pivotally attached to the underside of the skateboard about a second pivot axis. The swivel and the bushing are ganged together to provide pivoting of a skateboard in two dimensions.  
           [0008]    In a presently preferred embodiment of the invention the skateboard truck includes a base attachable to the underside of a skateboard and an arm carried by the base and rotatable relative to the base about a first axis. An axle having a pair of wheels mounted at opposite ends thereof is carried by the arm and the axle is rotatable relative to the arm about a second axis. A spring-loaded linkage is operatively connected between the base and the arm for limiting the rotational motion of the arm and biasing the arm towards a rest position aligned with the skateboard&#39;s direction of movement.  
           [0009]    The improved skateboard truck is preferably attached to the front of the skateboard, while a conventional truck is fastened to the rear. Because of the improved capabilities of the present invention the skateboarder is able to propel the skateboard by shifting the nose of the skateboard from side-to-side. Further, the present invention enables the rider to smoothly navigate the front of the skateboard to-and-fro and complete sharp turns at a rider controlled rate. As such, the skateboard closely simulates the dynamics of a surfboard on the water. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:  
         [0011]    [0011]FIG. 1 is an exploded perspective view of the skateboard truck of the present invention;  
         [0012]    [0012]FIG. 2 is a cross-sectional side view of the base plate of the truck in FIG. 1;  
         [0013]    [0013]FIG. 3 is a bottom view of the base plate in FIG. 2;  
         [0014]    [0014]FIG. 4 is a cross-sectional side view of the pivot member of the truck in FIG. 1;  
         [0015]    [0015]FIG. 5 is a cross-sectional side view of the assembled truck in FIG. 1;  
         [0016]    [0016]FIG. 6A is a top view of the truck in FIG. 1 mounted onto a skateboard, the view showing the arcing lateral movement of the nose of the skateboard as it moves to-and fro;  
         [0017]    [0017]FIGS. 6B and 6C are perspective views of the of the truck in FIG. 1 mounted onto a skateboard, the view showing the arcing lateral movement of the nose of the skateboard as it moves to-and fro;  
         [0018]    [0018]FIGS. 7A and 7B are simplified schematic views of the path of motion of a conventional skateboards;  
         [0019]    [0019]FIGS. 7C and 7D are simplified schematic views of the path of motion of the skateboard in FIG. 6; and  
         [0020]    [0020]FIG. 8 is a side view of an alternative embodiment of the truck in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    In a preferred embodiment of the invention, there is provided a skateboard truck  10  having two independently spring-loaded pivoting members. As shown in FIG. 1, the truck  10  comprises a baseplate  12 , a pivoting member  14 , and a hanger  16 .  
         [0022]    Referring to FIG. 1, the baseplate  12  comprises a casting forming a base  20 , a bearing platform  26 , and a housing  44 . The baseplate  12  can be of any suitable construction and made of any suitable material. In a preferred embodiment, the baseplate  12  is cast in A356 prime aircraft grade aluminum and heat treated to Rockwell T-6. In alternative embodiments the baseplate  12  may be cast or forged of any formable high strength metal or plastic. The base  20  is a substantially rectangular plate having a finite thickness, for example about {fraction (3/16)} inches, a rear tapered portion  25 , and plurality of apertures  22 . The apertures  22  are suitably configured for mounting the baseplate  12  onto the underside of the skateboard platform.  
         [0023]    Referring to FIGS. 2 and 3, the bearing platform  26  projects upward, and substantially oblique, from the one end of the base  20 . The platform  26  comprises a circular body having a recess  32  formed on its underside by a circular periphery  42  having an inner surface  34 . The recess  32  includes a pair of parallel and spaced apart ribs  40  which extend into the recess  32 . As shown in FIG. 2, the bearing platform  26  is defined by an upper surface  27 , which runs parallel to a bearing plane  28 . The bearing plane  28  is defined at an angle oblique to a lateral plane  24  of base  20 , preferably at about 10° to about 25°, more preferably at about 17°. The upper surface  27  comprises a central bore  30 , defining a first axis  36  substantially perpendicular to the bearing plane  28 , and a semicircular notch  38 .  
         [0024]    The housing  44  projects upward, and substantially perpendicular from the base  20 , and is integral with the bearing platform  26 . The housing  44  includes a plurality of sidewalls  48 ,  52 ,  54 , and  56 , and a top wall  49 , forming a cavity  46  in the housing  44  for retaining a spring system, as discussed in detail below. Sidewall  48  comprises a circular opening  58  for receiving a bolt.  
         [0025]    Referring to FIG. 1, the pivot member  14  comprises a casting forming a cylindrical pedestal  60  having a finite thickness, and an elongated arm  62 . The pivot member  14  can be of any suitable construction and made of any suitable material. In a preferred embodiment, the pivot member  14  is cast in A356 prime aircraft grade aluminum and heat treated to Rockwell T-6. In alternative embodiments the pivot member  14  may be cast or forged of any formable high strength metal or plastic. Referring now to FIG. 4, the pedestal  60  includes a circular notch  64  formed about its base portion, and an orifice  66 . A boss portion  70  supporting a link pin  72  extends downwardly from a base portion of the pedestal  60 . Referring back to FIG. 1, the arm  62  extends upwardly from the base  60  and comprises a pair of gussets  73  and a cantilevered body  74  having a proximal end  65  and distal end  67 . The gussets  73  are triangular in shape and disposed in parallel along the proximal end  65  of the body  74 . The gussets  73  are integrally formed with the pedestal  60 , forming a void  78  which defines a top surface  63  of the pedestal  60 .  
         [0026]    The body  74  is an arching structure extending from the gussets  72  at an acute angle  80  (see FIG. 4) relative a lateral pedestal base plane  68 , preferably at about a 17° angle. A lip  83  is formed along the top surface of the body  74 , forming a channel  85  with a bearing surface  87  and a plurality of stiffening ribs  95 , which extend into the channel  85 . Referring to FIG. 4, a groove  84  formed in the underside of the body  74  comprises a second series of stiffening ribs  86 , which extend into the groove  84 . The body  74  additionally includes a counterbore  92  defining a second axis  91  inclined at an angle preferably about 63° relative to the pedestal base plane  68 . Referring now to FIG. 1, the body  74  further includes a blind hole  88  lined with a urethane cup  90 . Referring back to FIG. 4, the blind hole  88  defines a third axis  89  inclined at an angle preferably about 40° relative to the second axis  91 .  
         [0027]    With reference to FIG. 1, the hanger  16  comprises a casting forming a body portion  100  and end portions  102  extending outwardly from the body portion  100  in opposite directions. The hanger  16  can be of any suitable construction and made of any suitable material. In a preferred embodiment, the hanger  16  is cast in A356 prime aircraft grade aluminum and heat treated to Rockwell T-6. In alternative embodiments the hanger  16  may be cast or forged of any formable high strength metal or plastic. The end portions  102  include a pair of concave channels on their undersides. Axle rod  104  extending from the end portions  102  carry the skateboard wheels mounted on threaded ends  106 . The hanger  16  further includes a pivot pin  108  extending downwardly from a central region of the body portion  100 . A platform  110  having a cut-out  109  and an eyelet  112 , extends laterally from a central region of the body portion  100 , opposite the pivot pin  108 . As would be recognized by one skilled in the art, the construction of the hanger body can be modified as desired.  
         [0028]    Referring to FIGS. 1 and 5, the hanger  16  is preferably mounted onto the arm  14  by a king pin  114  which passes through the eyelet  112  of the platform  110 . When assembled, the king pin  114  extends through a first bushing  120  disposed between the platform  110  and the arm body  74 . The king pin  114  further extends through a second bushing  122  and a flat washer  118  seated within the cut-out  109 , disposed between a fastening nut  116  and a top surface of the platform  110 . The king pin  114 , nut  116 , and washer  118  can be of any suitable type or construction and made of any suitable material. In a preferred embodiment, the king pin  114 , washer  118  and nut  116  are fabricated from steel having conventional dimensions, preferably about ⅜ inches in diameter. Referring to FIGS. 1 and 4, in a presently preferred embodiment, the first and second bushings  120  and  122  are urethane. The bolt head  124  of the king pin  114  is displaced on the underside  84  of the body  74 , between the plurality of ribs  86 , such that the king pin  114  does not rotate as the nut  116  engages a threaded portion of the king pin  114 . The pivot pin  108  engages the pivot cup  90  within the aperture  88  to align the hanger  16  relative to the arm  14 .  
         [0029]    The compliant properties of the bushings  120  and  122  allows the hanger  16  to pivot about a longitudinal axis  170  (see FIG. 5) in conventional fashion, when a sufficient load is applied to an end portion  102  of the hanger  16 . As such, the hanger  16  functions as a first resilient, or spring-loaded pivoting member. As will be recognized by one skilled in the art, the mounting of the hanger  16  to the arm  14  can be modified as desired. For example, a system using a pair of compression springs, as described in U.S. Pat. No. 5,263,725 to Gesmer et al., may be used instead of the urethane bushing system.  
         [0030]    The pivot member  14  is preferably mounted onto the baseplate  12  is by a pivot bolt  130  which passes through the pedestal orifice  66  of the pivoting member  14 . When assembled, the pivot bolt  130  extends through a nut  134 , a bronze bushing  136 , a pair of bearing plates  138 , a first bearing  140 , and a flat washer  142 . The pivot bolt  130 , nut  134 , and washer  142  can be of any suitable type or construction and made of any suitable material. In a preferred embodiment, the pivot bolt  130 , nut  134 , and washer  142  are fabricated from steel having conventional dimensions, preferably about ⅜ inches in diameter.  
         [0031]    The pivoting member  14  is assembled onto the baseplate  12  such that the boss  70  engages the semicircular notch  38 . The washer  142  and the first bearing  140 , which is sandwiched between a pair of bearing plates  138 , are displaced between the pivot bolt head  132  and the pedestal top surface  63 . The first bearing  140  can be of any suitable type or construction and made of any suitable material. In a preferred embodiment, the first bearing  140  is a steel needle thrust bearing having an outer diameter of about ⅞ inches and an inner diameter of about ½ inches. The bronze bushing  136  comprises an inner aperture suitable for receiving the pivot bolt  130  and is disposed within the aperture  66  to provide minimum friction between the pivoting member  14  and the pivot bolt  130 . A bearing assembly comprising a second bearing  146  sandwiched between a pair of bearing washers  144 , is disposed with the circular notch  64  in between the pedestal  60  and the baseplate bearing surface  27 . The nut  134  is disposed within the housing recess  32 , between the pair of ribs  40 , such that the nut  134  is confined and can not rotate as the nut  134  engages a threaded end portion of the pivot bolt  130 .  
         [0032]    The second bearing  146  can be of any suitable type or construction and made of any suitable material. In a preferred embodiment, the second bearing  146  is a steel needle thrust bearing having an outer diameter of about 2{fraction (3/16)} inches and an inner diameter of about 1½ inches. The bearings  140  and  146  function to provide smooth rotation of the pivot member  14 . In alternative embodiments, other means may be used to provide minimal friction between the arm  14  and the base  12 , such as ball bearings, oil impregnated bronze plain bearings, flexures (flexible structures), or the like.  
         [0033]    A spring system  50  retained within the housing  44  includes a link  152 , a link bolt  154 , a spring  158 , and a nut plate  156 . The link  152  comprises a resilient metal formed in an L-shape, having a first portion  151  extending substantially perpendicular from a second portion  157  that is substantially canted at its distal end. The link  152  is preferably formed from a sheet of stainless steel, but may be of any suitable material having similar material properties. The first portion  151  comprises a bolt opening  155  centrally displaced along the first portion  151 . The second portion  157  comprises a link pin opening  153  along its canted distal end.  
         [0034]    The spring system  50  is coupled to the housing  44  by passing the link bolt  154  through the circular and bolt openings  58  and  155 . In a preferred embodiment, the link bolt  154  is Grade  8  steel having a diameter of about ⅚ inches. A threaded portion of the link bolt  154  engages a threaded hole  160  centrally located within the nut plate  156 . The spring  158  is preferably a steel heavy-duty compression spring disposed between the nut plate  156  and the first portion  151  of the link  152 .  
         [0035]    The spring system  50  is coupled to the pivot member  14  by engaging the link pin  72  with the link opening  153  on the canted end of the link  152 . The spring system  50  functions to control the rotational movement of the pivot member  14 . The link  152  is spring-loaded to resist and control rotational movement of the pivot member  14 . By turning the link bolt  154  clockwise, the threaded portion of the bolt  154  engages the nut plate  156  and compresses the spring  158 . The spring  158  then applies a spring load to the first portion  151  of the link  152 , and further, stiffens the resilient movement or tension in the link  152 . Thus, if the threaded portion the link bolt  154  is fully engaged with the nut plate  156 , the tension in the link  152  will stiffen and the spring system  50  will constrain the pivot member  14  from rotational translation, thereby increasing the turning resistance. Likewise, as the threaded portion the link bolt  154  is disengaged from the nut plate  156 , the pivot member  14  is increasingly free to rotate about the perimeter defined by the semicircular slot  38 , as the spring system  50  would exert minimal spring load on the link pin  72 , thereby loosening the turning resistance.  
         [0036]    The frictionless properties of the bearings  140  and  146  allow the pivot member  14  to pivot about the first axis  36  in a plane oblique to the direction of movement when a sufficient side load is applied on the arm  62 . The spring system  50  applies a spring-load on the pivot member  14 , limiting the rotational translation of the pivot member  14 .  
         [0037]    In accordance with the preferred embodiments above, the hanger  16  functions as a first resilient or spring-loaded pivoting member. Similarly, the pivot member  14  functions as a second resilient or spring-loaded pivoting member. As would be recognized by one skilled in the art, the mounting of the pivot member  14  to the baseplate  12  and coupling the pivot member  14  to the spring system  50  can be modified as desired. For example, a urethane bushing, leaf spring or extension spring system with non-indexed centering properties may be used in place of the compression spring system.  
         [0038]    In operation, the present invention is ideal for turning a skateboard at a parabolic rate. To perform this function, the improved truck  10  is provided at the front of the skateboard while a conventional truck is provided at the rear. A example of such a conventional truck is provided in U.S. Pat. No. 3,945,655, the disclosure of which is incorporated herein by reference. The skateboard is navigated by a rider standing on its deck, by shifting his/her weight from side to side such that it moves in a forward direction. The rider can propel the skateboard forward without removing his/her feet from the deck. FIGS. 7C and 7D show the serpentine motion of the path of the front truck, which is depicted as  165 , as it weaves over the path of a conventional rear truck, depicted as  160 . It is this difference in frequency between the two sinusoidal paths that is the basis for forward propulsion of the skateboard. In accordance with the present invention, the rear truck becomes a relative point from which the front truck may pivot, and such dynamics acts to pull the board forward, as will be described in further detail later.  
         [0039]    The improved maneuvering capabilities of a skateboard incorporating the truck  10  is accomplished by the dual pivoting characteristics of the truck  10 . The resilient bushings  122  and  120  facilitate a first pivoting axis  170  inclined at approximately 30° to 60° relative to the plane of movement. The pivot member  14  provides a second pivoting axis substantially oblique to the plane of movement, and wherein the second pivoting axis is inclined relative the first pivot axis at an angle preferably at about 130° to about 160°, more preferably at 140°. The dual pivoting truck  10  enable the nose of the skateboard to move in a side-to-side motion.  
         [0040]    Referring to FIG. 7A, skateboards using a pair of “conventional” trucks  11  turn together at a constant rate along primary sinusoidal path  160 . Both front and rear trucks pivot in one dimension symmetrically and in fixed relation, as shown in FIG. 7B. A skateboard according to the preferred embodiments of the present invention, utilizes an improved front truck  10  in combination with a “conventional” rear truck  11 . According to this embodiment, as shown in FIGS. 7C and 7D, the rear “conventional” truck  11  turns on the primary path  160 , while simultaneously, the front truck  10  turns on a secondary sinusoidal path  165 . As such, the skateboard may trace a variable parabolic path. The front and rear trucks of the skateboard pivot asymmetrically, as the rear truck pivots in one dimension and the front truck pivots in two dimensions, in contrast to the fixed relation provided by a skateboard utilizing a pair of conventional trucks. The asymmetric properties of the improved skateboard enables the front and rear trucks to turn independently, allowing a skateboard rider to create a variable arc of turn with all wheels in contact with the ground, while propelling the skateboard forward.  
         [0041]    The angled configuration of the bearing plane  28  (see FIG. 5) defines the plane of movement of the nose of the skateboard to-and-fro as an arc illustrated in FIG. 6A-C. The arcing lateral movement of the nose provides secondary torquing on the pivot member  14 , in addition to the torque created by weight shift, allowing the rider to turn the skateboard with minimal effort. Additionally, the arcing lateral movement of the nose enables the rider to “carve” the skateboard in a forward serpentine motion as the users twists or shifts his/her weight back and forth. Increasing the angle of the plane  28  increases the amount of secondary torque that the rider can apply to the pivoting member  14  by shifting his/her weight from one side to the other. As such, the truck of present invention is improved over trucks of the prior art, as it balances the combination of torque upon the arm  14  created by the lateral weight shifting of the user during the side-to-side movement of the skateboard, so that the two movements can work smoothly together. Without the angled bearing plane, lateral weight shift from the center position would bear too little torque upon the rotation of the arm  14 . Conversely, lateral weight shift created upon the arm  14  in a turning position bears too much torque. This imbalance causes jerkiness and loss of turning control.  
         [0042]    In use, the truck  10  is attached to the skateboard platform such that the arm  62  of the pivoting member  14  extends rearward. This configuration causes the truck  10  to restore the truck wheels to their center position as the skateboard propels forward. Analogous to a shopping cart, where the wheels are behind the pivot point, the forward movement of the skateboard tends to align the pivoting member  14  with the direction of movement. Thus, the pivoting member  14  acts to automatically center, or self-correct itself, providing stability to the truck  10  as the skateboard travels at higher speeds.  
         [0043]    Referring to FIG. 5, the spring system  50  functions to provide the truck  10  with additional self-centering capabilities. The spring-loaded link  152  constantly acts upon the link pin  72  to return the truck  10  to its center position. As such, the spring system  50  creates a “non-indexing” center. In other words, the user can push the front of the board from one side to another smoothly past the truck&#39;s center position, mimicking the non-biased dynamics of a surfboard. Additionally, the spring system  50  creates a resistance against the arm  14  that correlates to the resistance against the hanger provided by the urethane bushings  120  and  122 . Furthermore, a rider performing an aerial trick, such as an Ollie, can return the board back to the ground confidently, as the spring system  50  returns the truck  10  firmly back to a conventional orientation upon landing of the board. Thus, the present invention further overcomes the inherent problems of pivoting trucks of the prior art.  
         [0044]    A user may adjust the amount of “freedom” of pivotal resistance of the truck  11  via the link bolt  154 . By tightening or loosening the link bolt  154 , the user can vary the tension of the spring  158  on the link  152 , which in turn, limits the rotational movement of the pivot member  14 . Thus, a beginner can fully engage the link bolt  154 , such that the skateboard becomes very stable. A more advanced rider, can loosen the link bolt  154  to provide more pivotal freedom and increased maneuvering. For example, the present invention enables an advanced rider to complete a sharp U-turn on a sidewalk of conventional dimensions.  
         [0045]    In alternative embodiments, the base plate of the truck can be altered to any suitable size or shape. An example of a modified embodiment is shown in FIG. 8. In other embodiments, the pivot member and hanger may be integrated into a single piece. In this embodiment, the integrated pivot member may include an axle resiliently mounted about an extended portion of the pivot member such that the axle may pivot relative to the pivot member.  
         [0046]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention.  
         [0047]    Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.