| 摘要 |
<p>A foot receiving member (3) has a spring member (5) detachably attached to the bottom surface thereof. The spring member includes a top, arched, layer (7) and a bottom arched, layer (9) and a strap (11) disposed between the two arched layers. The arched layers are attached, at their ends, to a corresponding end of the strap (11) in such a manner that the spring member (5) will be automatically disassembled under the influence of an extraordinary lateral force. <IMAGE></p> |
