| 摘要 |
<p>The skate board or roller skate can be moved without removing the foot from the board. It has a pedal on the top of the board which, when pressed down by the foot, presses a nylon shoe on to a chain. This moves an intermediate free wheel which is joined to the front wheel by another chain and increases its speed. When the foot is taken off the pedal this is returned to a raised position by a spring (9). A pumping action on the pedal gives a continual movement of the skate board.</p> |
