Wheel structure whose speed can be controlled

Abstract

A wheel structure includes a support rack having two ends each provided with a roller and a control device. The control device is mounted on the respective end of the support rack and is urged on the roller to reduce the rotational speed of the roller. Thus, the rotational speed of the wheel structure can be efficiently controlled to the optimum state, thereby greatly facilitating a learner or a kid employing the wheel structure.

What is claimed is:  
     
         1 . A wheel structure, comprising: 
 a support rack having two ends each provided with a roller and a control device; wherein:    the roller is rotatably mounted on the respective end of the support rack;    the control device is mounted on the respective end of the support rack and is urged on the roller to reduce the rotational speed of the roller.    
     
     
         2 . The wheel structure in accordance with  claim 1 , wherein the control device includes a cover, a circular plate, a push member, and an adjusting member, wherein: 
 the cover of the control device is secured on the respective end of the support rack and has a first side and a second side;    the circular plate has a first side rested on the second side of the cover and a second side formed with a tapered receiving recess;    the push member of the control device is movably mounted on the second side of the circular plate and has a first end formed with a tapered head rotatably mounted in the receiving recess of the circular plate and a second end extended through the circular plate and the cover;    the tapered head of the push member has a side formed with an urging face that can be moved to press a plane portion of the roller; and    the adjusting member of the control device is rotatably mounted on the first side of the cover and is combined with the second end of the push member for rotating the push member.    
     
     
         3 . The wheel structure in accordance with  claim 2 , wherein the cover of the control device has a periphery formed with a through hole for passage of the second end of the push member.  
     
     
         4 . The wheel structure in accordance with  claim 3 , wherein the receiving recess of the circular plate has a center formed with a through hole aligning with the through hole of the cover for passage of the second end of the push member.  
     
     
         5 . The wheel structure in accordance with  claim 2 , wherein the receiving recess of the circular plate has a periphery formed with at least one protruding rib, and the tapered head of the push member has a periphery formed with at least one guide slot for receiving the protruding rib of the circular plate.  
     
     
         6 . The wheel structure in accordance with  claim 2 , wherein each of the two ends of the support rack has a rectangular shape, and the first side of the cover has a center formed with a rectangular positioning hole mounted on the respective rectangular end of the support rack.  
     
     
         7 . The wheel structure in accordance with  claim 2 , wherein the circular plate of the control device is combined with the cover by a screw member.  
     
     
         8 . The wheel structure in accordance with  claim 2 , wherein the roller has an inner wall formed with a toothed portion, and the circular plate has an outer wall rested on the toothed portion of the roller.  
     
     
         9 . The wheel structure in accordance with  claim 2 , wherein the second end of the push member is formed with an outer thread, and the adjusting member is formed with an inner thread screwed on the outer thread of the second end of the push member.  
     
     
         10 . The wheel structure in accordance with  claim 1 , wherein each of the two ends of the support rack is provided with a shaft protruded outward therefrom, and the roller is rotatably mounted on the shaft of the respective end of the support rack.  
     
     
         11 . The wheel structure in accordance with  claim 10 , wherein the roller is rotatably mounted on the shaft of the respective end of the support rack by a bearing.  
     
     
         12 . The wheel structure in accordance with  claim 11 , wherein the roller is formed with a stepped recess for receiving the bearing.  
     
     
         13 . The wheel structure in accordance with  claim 11 , wherein the shaft of the support rack is formed with an outer thread, and a locking nut is screwed on the outer thread of the shaft of the support rack and is rested on the bearing, so that the roller is rotatably mounted on the shaft of the respective end of the support rack by the locking nut.  
     
     
         14 . The wheel structure in accordance with  claim 1 , wherein the roller has a side formed with an annular flange, the annular flange of the roller has a side formed with a plane portion and has an inner wall formed with a toothed portion.  
     
     
         15 . The wheel structure in accordance with  claim 2 , wherein the receiving recess of the circular plate is formed with a slit, so that the circular plate has a flexible feature and can be expanded outward when the receiving recess of the circular plate is compressed.  
     
     
         16 . The wheel structure in accordance with  claim 15 , wherein the circular plate can be expanded outward, so that the outer wall of the circular plate is urged on the inner wall of the roller.  
     
     
         17 . The wheel structure in accordance with  claim 1 , wherein the support rack is secured on a bottom of a shoe of a roller skate.  
     
     
         18 . The wheel structure in accordance with  claim 1 , wherein the support rack is secured on a bottom of a scooter.