Abstract:
A skate truck is disclosed which provides for a wide yaw angle for a hanger, minimal friction during yawing of the hanger, and a suspension that is dynamically stabilized based on a weight of a rider and a turn radius of a vehicle to which the skate truck is mounted. Additionally, a tension of the skate truck can be adjusted by preloading a spring which accommodates a wide weight ranger of riders. The truck may have a hanger supported between two bearings, namely, a sliding bearing system and a thrust bearing. The sliding bearings slide within grooves that define a pivot axis of the hanger. The grooves can also have various customized ramp profiles to provide a different feel during turning of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND 
     The present invention relates to a truck for a vehicle such as a skateboard or scooter. 
     Prior art skate trucks are fabricated in the following manner. A hanger of the skate truck pivots about a nose. The hanger is biased to the straight forward neutral position by an elastomeric member. However, the elastomeric member must be sufficiently rigid so that the rider&#39;s weight does not over power the bias force created by the elastomeric member. Additionally, the elastomeric member must be pre-tensioned to a specific amount to properly support the weight of the rider. These factors limit rotation of the hanger of the prior art skate truck to a narrow range. Moreover, there is a danger that the elastomeric member may bottom out as the rider progresses into a turn thereby inadvertently lifting the outside wheels of the skate truck. 
     Accordingly, there is a need in the art for an improved skate truck with a wide pivot range and a truck that can accommodate a wider weight range of riders. 
     BRIEF SUMMARY 
     The present invention addresses the needs discussed above, discussed below and those that are known in the art. 
     A stable skate truck that provides for a wide yaw angle and weight range of riders is provided. The skate truck has at least three (3) ball bearings that slide within grooves formed in one of either a base or hanger of the skate truck. The grooves match the ball bearings and have a ramp configuration to push the hanger away from the base as the skate truck progresses into a turn. The ramps of the grooves may have different profiles such as regressive, progressive, linear and combinations thereof to provide the rider a different feel as the rider progresses into a turn 
     A spring is preloaded and biases the hanger towards the base so that the truck is normally in the straight forward direction. As the skate truck progresses into a turn, the ball bearings slide within the grooves and the spring is compressed to urge the ball bearings back to the center of the ramps and to urge the truck back to the straight forward direction. The spring assists in stabilizing the vehicle. A second component that stabilizes the vehicle is the centrifugal force created as the rider progresses into a turn. The centrifugal force applies a variable downward force on a deck of the vehicle based on the turn radius. The centrifugal force is translated to the ball bearings and urges the ball bearing back to the center of the ramp further urging the truck back to the straight forward direction. Another component that stabilizes the vehicle is the weight of the rider. The weight of the rider also urges the ball bearings back to the center of the ramp. Since the weight of the rider urges the ball bearings back to the center of the ramp, the preload on the spring can be used for a wider weight range of riders. 
     More particularly, a suspension for a vehicle is disclosed. The suspension may comprise a base, a hanger and three ball bearings. The based may be mounted to a frame of the vehicle. The base may have three semi-circularly shaped grooves within a first common plane. The three semi-circularly shaped grooves may have a first center point. The three semi-circularly shaped grooves may have a radius r. The three semi-circularly shaped grooves may define a pivot axis perpendicular to the first common plane and located at the first center point. The pivot axis may be skewed with respect to a longitudinal axis of the frame of the vehicle. 
     Wheels may be mounted to the hanger so that the vehicle can roll on a surface. The hanger may have three mounting recesses within a second common plane. The three mounting recesses may define a second center point wherein a distance between the three mounting recesses and the second center point is r. The second common plane of the hanger may be disposed parallel to the first common plane of the base. The second center point may be positioned on the pivot axis. 
     The three ball bearings may be seated within the mounting recesses and traversable along the three semi-circularly shaped grooves when the hanger rotates about the pivot axis. 
     The suspension may further comprise a biasing member for urging the first and second common planes closer to each other so that the ball bearings slide within the grooves as the hanger rotates about the pivot axis. The biasing member may be a compression spring. 
     Each of the three semi-circularly shaped grooves may have a contact surface which defines a ramp profile. The ball bearings may slide against the contact surface and compress or decompress the compression spring as the ball bearings slide against the contact surface based on the ramp profile. The ramp profiles of the three semi-circularly shaped grooves may be identical to each other. The ramp profiles may be progressive, regressive, linear or combinations thereof. Also, the three semi-circularly shaped grooves may be symmetrically identical to each other. 
     The suspension may further comprise a thrust bearing disposed between the compression spring and the hanger to mitigate binding between the hanger and the spring as the hanger rotates about the pivot axis. 
     Moreover, a vehicle with the suspension system is disclosed. In particular, the vehicle may comprise a deck and a first suspension system. The deck may define a front portion, a rear portion, a bottom surface and a top surface. 
     The first suspension system may be mounted to the bottom surface at the rear portion of the deck. The first suspension may comprise a base, a hanger, and three ball bearings. The base may be mounted to a frame of the vehicle. The base may have three semi-circularly shaped grooves within a first common plane. The three semi-circularly shaped grooves may have a first center point. The three semi-circularly shaped grooves may have a radius r 1 . The three semi-circularly shaped grooves may define a pivot axis perpendicular to the first common plane and located at the first center point. The pivot axis may be skewed with respect to a longitudinal axis of the deck. 
     The hanger may be used to mount wheels so that the vehicle can roll on a surface. The hanger may have three mounting recesses within a second common plane. The three mounting recesses may define a second center point wherein a distance between the three mounting recesses and the second center point is r 1 . The second common plane of the hanger may be disposed parallel to the first common plane of the base. The second center point may be positioned on the pivot axis. 
     The three ball bearings may be seated within the mounting recesses and traversable along the three semi-circularly shaped grooves when the hanger rotates about the pivot axis. 
     The vehicle may further comprise a second suspension system mounted to the bottom surface at the front portion of the deck. The first and second suspension systems may be mounted in opposite directions to each other. The second suspension system may also comprise a base, a hanger and three ball bearings. The base may be mounted to a frame of the vehicle. The base may have three semi-circularly shaped grooves within a first common plane. The three semi-circularly shaped grooves may have a first center point. The three semi-circularly shaped grooves may have a radius r 2 . The three semi-circularly shaped grooves may define a pivot axis perpendicular to the first common plane and located at the first center point. 
     With respect to the second suspension system, the hanger may be used to mount wheels so that the vehicle can roll on a surface. The hanger may have three mounting recesses within a second common plane. The three mounting recesses may define a second center point wherein a distance between the three mounting recesses and the second center point is r 2 . The second common plane of the hanger may be disposed parallel to the first common plane of the base. The second center point may be positioned on the pivot axis. 
     With respect to the second suspension system, the three ball bearings may be seated within the mounting recesses and traversable along the three semi-circularly shaped grooves when the hanger rotates about the pivot axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a bottom view of a skate truck; 
         FIG. 2  is a cross sectional view of the skate truck shown in  FIG. 1 ; 
         FIG. 3  is an exploded bottom view of the skate truck shown in  FIG. 1 ; 
         FIG. 4  is an exploded view of a base and hanger shown in  FIG. 3  illustrating the assembly of the sliding bearings into grooves and mounting recesses; 
         FIG. 4A  is an exploded view of a base and hanger illustrating a reverse embodiment shown in  FIG. 4 ; 
         FIG. 5A  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a first ramp profile; 
         FIG. 5B  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a second ramp profile; 
         FIG. 5C  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a third ramp profile; 
         FIG. 5D  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a fourth ramp profile; 
         FIG. 5E  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a fifth ramp profile; and 
         FIG. 5F  is a graph illustrating spring force/ramp profile as a function of degree of rotation of the hanger illustrating a sixth ramp profile. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, a skate truck  10  is shown. The skate truck may be mounted to a bottom surface  12  of a deck  14  of a scooter, skateboard or like vehicle  16  (See  FIG. 2 ). When the deck  14  is rotated about its central longitudinal axis  18  (see  FIG. 2 ), a hanger  20  may be yawed about a pivot axis  22  (See  FIG. 3 ) to turn the vehicle left or right. The pivot axis  22  is defined by three semi-circularly shaped grooves  24   a - c  and three bearings  26   a - c  that slide within the grooves  24   a - c  (see  FIG. 4 ) as the hanger  20  rotates about the pivot axis  22 . The bearings  26   a - c  are seated within mounting recesses  28   a - c . The grooves  24   a - c  may have a ramp profile. The ramp profile may have left and right sides  29   a, b  (see  FIG. 4 ) which are identical to each other so that as the rider turns left or right, the response of the skate truck  10  is identical on the left and right sides  29   a, b . For each of the sides of the ramp profile, the ramp may push the ball bearings  26   a - c  further away out of the groove  24   a - c  as the rider progresses in the turn. This pushes the hanger  20  further away from the base  30 . As the hanger  20  is pushed further away from the base  30 , spring  32  is compressed to increase a spring force and stabilize the vehicle by biasing the vehicle  16 /truck  20  back to the straight forward direction. 
     Three components urge the hanger  20  back to its normal straight-forward position to stabilize the vehicle during turns and straight-forward motion. In particular, the spring force of the spring  32  urges the ball bearings  26   a - c  back to a center  31  of the ramp of the grooves  24   a - c . Additionally, the weight of the rider urges the ball bearings  26   a - c  back to the middle or lowest portion  31  of the ramp defined by the groove  24   a - c  to dynamically account for the weight of the rider. The third component is related to the centrifugal force created during turning of the vehicle  16 . When the rider turns, the centrifugal force applies a variable downward force based on the turn radius onto the deck  14  of the vehicle  16 . This downward force also urges the ball bearings  26   a - c  back to the center  31  of the ramp of the grooves  24   a - c.    
     The hanger  20  is supported by the bearings  26   a - c  and thrust bearing  34  and does not directly contact the base  30  or the spring  32 . Accordingly, the rotation of the hanger  20  does not cause the hanger  20  to rub against the spring  32  or the base  30 . The hanger does not bind against the base  30  and the spring  32  as the hanger  20  rotates about the pivot axis  22 . As such, turning of the vehicle is smooth and effortless. 
     Accordingly, the skate truck  10  disclosed herein provides for a stable platform which stabilizes the vehicle  16  toward the straight-forward direction and also dynamically accounts for the weight of the rider and the turning motion to further urge the skate truck  10  back to its normal straight-forward direction. Moreover, the hanger  20  rotates about pivot axis  22  and is disposed between two sets of bearings, namely, the sliding bearings  26   a - c  and the thrust bearings  34  so as to minimize friction, mitigate binding and promote smooth turning of the vehicle  16 . 
     More particularly, referring now to  FIG. 1 , the skate truck  10  includes the hanger  20  which is supported on both sides by thrust bearing  34  (e.g., needle thrust bearing) and sliding ball bearings  26   a - c  (See  FIG. 3 ). When the hanger  20  rotates about the pivot axis  22 , the thrust bearing  34  mitigates binding between the spring  32  and the hanger  20 . Additionally, the ball bearings  26   a - c  slide within grooves  24   a - c  which prevents contact between the hanger  20  and the base  30  to mitigate friction between the hanger  20  and the base  30  as the hanger  20  rotates about the pivot axis  22 . Accordingly, the thrust bearing  34  and the sliding bearings  26   a - c  mitigate friction and provide for effortless rotation of the hanger  20 . 
     Referring now to  FIG. 2 , the hanger  20  is biased toward the base  30  by way of spring  32 . A retaining pin  36  and a spring retainer  40  locates the spring  32 . Although a compression spring is shown for spring  32 , other types of springs are also contemplated. The retaining pin  36  may be threaded into the base  30  with threaded connection  38 . The pin  36  may have a central axis which is aligned to the pivot axis  22 . However, the pin  36  does not define the pivot axis  22  of the hanger  20 . The pin  36  merely holds the assembly together. The grooves  24  a-c (see  FIG. 3 ) formed in the base  30  define the pivot axis  22 . In support thereof, the ball bearing  26   a - c  remain fixed within the mounting recesses  28   a - c  (see  FIG. 4 ) of the hanger  20 . The mounting recesses  28   a - c  are all within a common plane. As the hanger  20  rotates about the pivot axis  22 , all of the ball bearing  26   a - c  contact the ramps of the grooves  24   a - c  at the same position. The ball bearings  26   a - c  move in unison with each other. When the hanger  20  rotates about the pivot axis  22 , the ball bearings  26   a - c  ride up and down on the ramps of the grooves  24  a-c at the same position. Since the ball bearings  26   a - c  track the grooves  24   a - c , the grooves  24   a - c  define the pivot axis  22 . The retaining pin  36  merely holds the ball bearings  26   a - c , hanger  20 , spring  32  and the spring retainer  40  together but does not determine the pivot axis  22  of the hanger  20 . To further show that the retaining pin  36  merely holds the assembly together and does not define the pivot axis, a gap  42  (see  FIG. 2 ) is shown between the retaining pin  36  and the interior surface  44  of a hole  46  (see  FIG. 3 ) formed in the hanger  20 . This illustrates that the retaining pin  36  does not guide rotation of the hanger  20  but only holds the assembly together. 
     Referring still to  FIG. 2 , a medial surface  48  of the hanger  20  is gapped  50  away from the medial surface  52  of the base  30  to mitigate rubbing friction between the hanger  20  and the base  30 . A nut  54  may be threaded onto the retaining pin  36  to compress spring  32  and hold the assembly together. The nut  54  may be a self locking nut or the threaded connection may be coated with a chemical thread locker to mitigate loosening due to vibration. The spring force of the spring  32  biasing the hanger  20  toward the base  30  may be adjusted by screwing the nut  54  further down the retaining pin  36  or up off of the retaining pin  36 . The nut  54  is adjusted to adjust the spring force of spring  32  to either stiffen or loosen the suspension provided by the skate truck  10 . The nut adjustment is made to account for the weight of the rider. For heavier riders, the spring  32  is proloaded to a greater amount compared to a lighter rider. Regardless, since the weight of the rider also biases the truck to the straight forward direction, the spring preload for a particular rider can be used for a greater range of rider weights. 
     Referring now to  FIGS. 5A-F , a spring force of the spring  32  as a function of degree of rotation of the hanger  20  is shown. Only one side of the ramp is shown in  FIGS. 5A-F . In particular, positive rotation of hanger  20  from the straight forward direction. The other side of the ramp (i.e., negative rotation) is identical to the side shown in  FIGS. 5A-F  but not shown for purposes of clarity. The graphs in  FIGS. 5A-F  represent various potential ramp profiles of the grooves  24   a - c . At zero degree rotation of the hanger  20 , the vehicle  16  is going straight-forward. For each degree of rotation, the ramps of the grooves  24   a - c  urge the ball bearing  26   a - c  up the ramp. As the ball bearings  26   a - c  are urged up the ramp, the ball bearing  26   a - c  push the hanger  20  away from the base  30  and the spring is deflected. Typically, total deflection or lift is about 0.200 inches. As the spring is deflected, the spring force increases linearly as the spring is deflected within its elastic range. The graphs (see  FIG. 5A-F ) show the spring force as a function of degree of rotation of the hanger  20  which correlates to the ramp profile of the grooves  24   a - c . As discussed above, the spring force of the spring  32  helps in stabilizing the vehicle  16  to bring the hanger  20  back to the straight-forward direction. As can be seen by the graphs, the spring force increases as the hanger  20  progresses into the turn. 
       FIG. 5A  illustrates a linear ramp profile. For each degree of rotation of the hanger  20 , the spring force is increased the same incremental amount until the hanger is fully rotated and the spring force is at its maximum. In  FIG. 5B , the ramp is initially linear during the first portion  56  of the hanger rotation. During the second portion  58 , for each additional degree of rotation of the hanger  20 , the spring force increases at a slower rate as shown by dash-line  60  which characterizes a regressive ramp profile. Alternatively, the ramp profile may be progressive in that for each additional degree of rotation of the hanger  20 , the rate at which the spring force increases may accelerate as shown by dash-line  62 . Referring now to  FIGS. 5C and 5D , the first portion  56  may be regressive as shown in  FIG. 5C  or progressive as shown in  FIG. 5D . The second portion  58  may be linear as shown by lines  64  or may continue on its regressive path  60  shown in  FIG. 5C  or may continue on its progressive path  62  as shown in  FIG. 5D .  FIG. 5E  illustrates a progressive ramp profile throughout the entire rotation of the hanger  20 . Oppositely,  FIG. 5F  illustrates a regressive ramp profile through the entire rotation of the hanger  20 . Accordingly, the ramp profile upon which the ball bearings  26   a - c  slide upon may have a linear profile, regressive profile, progressive profile or combinations thereof. The ramp profile can be customized to provide for a custom feel as the rider progresses through a turn on the vehicle  16 . 
     The skate truck  10  described above was shown as having three grooves  24   a - c . However, it is also contemplated that more grooves  24   d - n  may be incorporated into the skate truck  10 . For example, the skate truck  10  may have three or more grooves  24   a - n . These grooves  24   a - n  should be symmetrically formed about a point so as to define the pivot axis  22  so that the sliding bearings  26   a - c  apply even pressure to the ramps of the grooves  24   a - n . When three grooves  24   a - c  are formed in the base  30 , the grooves  24   a - c  can allow a +/− rotation of 60 degrees or less. Preferably, the grooves  24   a - c  are formed so as to allow for a +/− rotation of about 50 degrees. When four grooves  24  are formed in the base  30 , the grooves  24  are formed to allow for rotation of the hanger  20  to about +/−45 degrees or less. 
     Referring now to  FIG. 4 , the grooves  24   a, b, c  can have a radius of r 1 . The center of the radius r 1  defines the position of the pivot axis  22 . Also, the mounting recesses  28   a, b, c  can be positioned on a circle having a radius equal to r 1 . 
     As discussed above bearings  26   a - c  are seated within the mounting recesses  28   a - c . The bearings  26   a - c  are also disposed within the grooves  24   a - c . The bearings  26   a - c  do not roll on the ramps defined by the grooves  24   a - c . Rather, the bearings  26   a - c  predominantly slide on the ramp of the grooves  24   a - c . To facilitate sliding and not rolling of the bearings  26   a - c , grease can be disposed within the grooves  24  so that the sliding bearings  26   a - c  slides on the ramps defined by the grooves  24   a - c . Babbitt material (e.g., zinc) may be coated on the ramps of the grooves  24   a - c  and the bearings  26   a - c  may be chrome finished to protect the bearings  26   a - c  and the ramps of the grooves  24   a - c  from the pressure created between the bearings  26   a - c  and the ramps of the grooves  24   a - c    
     The grooves  24   a - c  may have a semi-circularly shaped cross section and be sized to fit the bearings  26   a - c  so that the bearings  26   a - c  contacts the grooves  24   a - c  along a line transverse to a curved length of the groove. The contact surface (i.e., line) sweeps or slides along the ramps of the grooves  24   a - c  as the hanger  20  is rotated about the pivot axis  22 . 
     Referring still to  FIG. 4 , the spring  32  assists in pushing the bearings  26   a - c  to the lowest most portion  31  of the ramps defined by the grooves  24   a - c . In other words, the spring  32  assists in biasing the hanger  20  so that the vehicle goes in the straight forward direction. The weight of the rider also helps in urging the bearings  26   a - c  down to the lowest most portion of the ramps defined by the grooves  24   a - c . This too helps in biasing the hanger so that the vehicle goes in the straight forward direction. A third component that helps in biasing the hanger so that the vehicle goes in the straight forward direction is the centrifugal force created when the rider of the vehicle  16  makes a left or right turn with the vehicle. As the rider progresses into a turn, a centrifugal force is created. The centrifugal force applies a force on the deck  14  of the vehicle  16  based on a turn radius. This centrifugal force is translated to the bearings  26   a - c  to bias the bearings  26   a - c  toward the lowest most portion of the ramps defined by the grooves  24   a - c.    
     The skate truck  10  can be mounted at the rear of the deck  14  in the orientation shown in  FIG. 2 . Arrow  66  shows the forward direction of the vehicle. The front of the deck  14  can be mounted with a second skate truck  10  mounted in a reverse orientation to the truck  10  shown in  FIG. 2  so that rolling of the deck  14  turns the vehicle left or right. Other configurations are also contemplated. For example, the skate truck  10  can be mounted at the rear of the deck  14  with a stationary or pivotable single or double front wheel with or without a handle bar. The skate truck can be mounted to the front of the deck  14  with a stationary or pivotable single or double rear wheel. A handle bar can still be mounted to the front of the deck  14 . 
     Referring now to  FIG. 4A , the grooves  24   a - c  may be formed in the hanger  20  and the mounting recesses  28   a - c  may be formed in the base  30 . 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including various ways of mounting the truck to the deck. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.