| 摘要 |
An extendible ramp comprising: (i) a chassis; (ii) a first ramp slidable movable relative to the chassis and hingable connected to the chassis; (iii) a second ramp carried by the first ramp and movable relative to the chassis and the first ramp; (iv) means for extending and retracting the first ramp; (v) means for extending and retracting the second ramp; (vi) means for detecting whether the ramp abuts an obstruction when the ramp is being extended; and (vii) means for retracting the ramp if it abuts an obstruction during extension. |
