Patent Publication Number: US-6981710-B2

Title: Wheel assembly for skateboard

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a wheel assembly, more particularly to a wheel assembly for a skateboard. 
   2. Description of the Related Art 
   Referring to  FIGS. 1 and 2 , a conventional skateboard  7  includes a footboard  8  and a wheel assembly  9  fixed on a bottom side of the footboard  8 . The wheel assembly  9  includes a positioning seat  91 , a wheel set  92  mounted below the positioning seat  91 , and an adjustment seat  93  mounted pivotally on the positioning seat  91  through a shaft  94  and disposed below the footboard  8 . When the center of gravity of a skater changes from left to right or right to left during use of the skateboard  7 , the positioning seat  91  and the wheel set  92  rotate about the shaft  94  relative to the adjustment seat  93  so as to turn the footboard  8 . Then, through coordination of a screw rod  96 , an L-shaped plate  97 , a packing ring  98 , and a coil spring  99 , which are all mounted in a receiving space  95  of the adjustment seat  93 , with a circular rod  90  that is fixed on the positioning seat  91  and that extends through an opening  951  in the adjustment seat  93 , the foot board  8  is restored to its original state. 
   However, during mounting of the screw rod  96 , the L-shaped plate  97 , the packing ring  98 , and the coil spring  99  in the receiving space  95  of the adjustment seat  93 , it is necessary that the coil spring  99  and the packing ring  98  be placed first in the receiving space  95 . Then, the L-shaped plate  97  is placed in the receiving space  95  so as to cover the coil spring  99  and the packing ring  98  and to cause the circular rod  90  to extend through a hole  971  in the L-shaped plate  97 . Afterwards, the screw rod  96  is passed through a hole  931  in the adjustment seat  93 , through another hole  972  in the L-shaped plate  97 , and through the coil spring  99  so as to engage threadedly a screw end  961  of the screw rod  96  with a screw hole  981  in the packing ring  98 . Assembly, as such, is difficult since the screw rod  96  has to be threaded through the holes  931  and  972  and inserted into the coil spring  99  after the coil spring  99  and the packing ring  98  are covered by the L-shaped plate  97 . Moreover, the coil spring  99  is different from an ordinary spring because the coil spring  99  must be stiff enough to provide a high restoring force such that the cost of producing the skateboard  7  is increased. 
   SUMMARY OF THE INVENTION 
   Therefore, the object of the present invention is to provide a wheel assembly for a skateboard that is easy to assemble and that is relatively inexpensive. 
   According to this invention, a wheel assembly for a skateboard comprises a positioning seat, a wheel set, an adjustment seat, a positioning post, and a pair of opposite resilient plates. The wheel set is mounted on the bottom side of the positioning seat. The adjustment seat is mounted on the top side of the positioning seat, and includes a first portion, a second portion opposite to the first portion, and a receiving space. The first portion and the positioning seat are interconnected pivotally so as to permit relative movement between the positioning seat and the adjustment seat. The positioning post is mounted on the positioning seat, and extends into the receiving space. The resilient plates are positioned on the adjustment seat within the receiving space, and are disposed on opposite sides of the positioning post. Each of the resilient plates has a fixed end disposed proximate to the second portion, and an abutting end opposite to the fixed end. The abutting ends of the resilient plates abut against the positioning post. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
       FIG. 1  is a fragmentary schematic view of a conventional skateboard; 
       FIG. 2  is a partly exploded perspective view of a wheel assembly of the conventional skateboard; 
       FIG. 3  is a perspective view of a skateboard incorporating the preferred embodiment of a wheel assembly of the present invention; 
       FIG. 4  is an enlarged perspective view of the preferred embodiment; 
       FIG. 5  is a schematic top view of the preferred embodiment; 
       FIG. 6  is a view substantially similar to  FIG. 5 , but with a wheel set and a positioning seat turned relative to an adjustment seat; and 
       FIG. 7  is a view substantially similar to  FIG. 5 , but with an adjustable piece operated to adjust the restoring force of resilient plates. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 3 to 5 , the preferred embodiment of a wheel assembly  3  according to the present invention is shown to be mounted on each of the front and rear ends of a footboard  2  of a skateboard  1  in opposite directions. Each of the front and rear ends of the footboard  2  is assembled with the wheel assembly  3  in this embodiment. However, when the front and rear ends of the footboard  2  are turnable, the turning directions of the front and rear ends should be opposite. Therefore, if the wheel assembly  3  is disposed only on the front end, the rear end can be assembled with an ordinary wheel assembly that does not function to control the direction of the footboard  2 . 
   The wheel assembly  3  of the present invention comprises a positioning seat  31 , a wheel set  32 , an adjustment seat  33 , a positioning post  34 , a pair of resilient plates  35 , and a resiliency adjustment device  36 . 
   The wheel set  32  is mounted fixedly on the bottom side of the positioning seat  31  in a conventional manner, and includes a wheel axle  321  and two roller wheels  322  journalled to the wheel axle  321 . 
   The adjustment seat  33  is mounted on the top side of the positioning seat  31 , and is fixed on a bottom surface of the footboard  2  in a conventional manner. The adjustment seat  33  includes a first portion  331 , a second portion  332  opposite to the first portion  331 , and a receiving space  333 . The receiving space  333  extends from the second portion  332  toward the first portion  331 , and has an opening  334  at the top side of the adjustment seat  33 . The first portion  331  and the positioning seat  31  are interconnected pivotally through a spindle  37  (see  FIG. 4 ) so that the positioning seat  31  and the adjustment seat  33  can move relative to each other. 
   The positioning post  34  is mounted fixedly on the top side of the positioning seat  31 , and extends into the receiving space  333  in the adjustment seat  33 . 
   The resilient plates  35  are positioned on the adjustment seat  33  within the receiving space  333 , and are disposed on opposite sides of the positioning post  34 . Each of the resilient plates  35  has a fixed end  351  proximate to the second portion  332 , and an abutting end  352  opposite to the fixed end  351 . The abutting ends  352  of the resilient plates  35  are curved ends that abut against the positioning post  34 . 
   The resiliency adjustment device  36  is mounted on the adjustment seat  33 , and includes an adjustable piece  361 , a screw rod  363 , a first vertical post  364 , a spring member  365 , a C-shaped ring  367 , and a second vertical post  368 . 
   The adjustable piece  361  is mounted slidably on the resilient plates  35  between the fixed ends  351  and the abutting ends  352 , and is formed with two non-parallel grooves  362  for insertion of the resilient plates  35  respectively therethrough. The grooves  362  extend upwardly from a bottom surface of the adjustable piece  361 . When the adjustable piece  361  is moved toward or away from the fixed ends  351  of the resilient plates  35 , the effective length of the resilient plates  35  can be changed so that resiliency of the latter is adjusted. When the adjustable piece  361  is moved away from the fixed ends  351 , that is, proximate to the positioning post  34 , the resilient plates  35  are placed closer to the positioning post  34 . 
   The screw rod  363  extends into the receiving space  333  through the second portion  332  of the adjustment seat  33 , and is located between the resilient plates  35 . The screw rod  363  extends threadedly through the adjustable piece  361  so as to permit adjusting of the latter. One end of the screw rod  363 , which is located externally of the second portion  332  of the adjustment seat  33 , is provided with an adjustment knob  369  for rotating the screw rod  363 . 
   The first vertical post  364  is mounted fixedly within the receiving space  333  in the adjustment seat  33 , is sleeved on the screw rod  363 , and is located between the adjustable piece  361  and the positioning post  34 . 
   The spring member  365  is sleeved on the screw rod  363 , and has two ends  366  (see  FIG. 5 ) abutting respectively against the adjustable piece  361  and the first vertical post  364 . 
   The C-shaped ring  367  is sleeved on the other end of the screw rod  363 , which is located proximate to the positioning post  34 , so as to clamp the screw rod  363 . The screw rod  363  is therefore limited and prevented from being released from the first vertical post  364 . 
   The second vertical post  368  is sleeved on the screw rod  363  opposite to the first vertical post  364 . The second vertical post  368  and the second portion  332  of the adjustment seat  33  cooperate to define two clamp holes  360  (see  FIG. 5 ) for receiving the fixed ends  351  of the resilient plates  35 , thereby positioning the fixed ends  351  on the adjustable seat  33 . 
   When a skater on the footboard  2  is in a balanced state, the positioning seat  31  is aligned with the adjustment seat  33 , and will not rotate about the spindle  37 , as illustrated in  FIG. 5 . 
   When the center of gravity of the skater changes to the left or right, the positioning seat  31 , along with the wheel set  32  and the positioning post  34 , pivot about the spindle  37  relative to the adjustment seat  33  to a state shown in  FIG. 6 . At this time, the abutting end  352  of one of the resilient plates  35  is pushed by the positioning post  34  so as to store a force that will restore the positioning seat  31 , the wheel set  32 , and the positioning post  34  to their original states shown in  FIG. 5 . 
   Through the adjustable piece  361 , the screw rod  363 , the first vertical post  364 , the spring member  365 , the C-shaped ring  367 , and the second vertical post  368  of the resiliency adjustment device  36 , the resiliency of the resilient plates  35  on the positioning post  34  can be adjusted, thereby adjusting the restoring force of the resilient plates  35 . The resilient plates  35  are shown in  FIG. 5  to be in a loosened state. At this time, the adjustable piece  361  is located at the leftmost end and abuts against the second vertical post  368  so that the effective length of the resilient plates  35  is longest and the resiliency, hence the restoring force, of the resilient plates  35  is smallest. 
   Referring to  FIG. 7 , when the adjustment knob  369  is rotated so as to rotate the screw rod  363 , the adjustable piece  361  moves simultaneously away from the fixed ends  351  of the resilient plates  35  and compresses slowly the spring member  365  so that the abutting ends of the resilient plates  35  abut tightly against the positioning post  34 . In this situation, the effective length of the resilient plates  35  is shortened and the restoring force is increased. 
   As mentioned hereinabove, the wheel assembly  3  of the present invention not only provides the footboard  2  with a restoring force, but also permits adjustment of the restoring force as desired. 
   From the aforementioned description of the preferred embodiment, since the adjustment seat  33  is mounted pivotally on the positioning seat  31 , and since the positioning post  34  and the resilient plates  35  abut against each other and are fixed respectively on the positioning seat  31  and the adjustment seat  33 , when the positioning seat  31  and the adjustment seat  33  pivot relative to each other, the positioning post  34  pushes one of the resilient plates  35  so that the resilient plate  35  can store a force that will restore the positioning seat  31  and the adjustment seat  33  to their original positions. Furthermore, the degree of the restoring force can be adjusted as desired. Moreover, since the L-shaped plate  97  (see  FIG. 2 ) of the conventional wheel assembly is dispensed herewith, assembly of the wheel assembly  3  of the present invention is easier to conduct. Additionally, the cost of the resilient plates  35  is lower than that of the coil spring  99  (see  FIG. 2 ). 
   While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.