| 摘要 |
A motor bus has a side door at its forward end which when opened accommodates laterally outward extension of a ramp from a normally stowed position below the floor of the bus, a portion of the ramp adjacent its outer end serving as a step for entering the bus when the ramp is in its stowed position. Extending longitudinally of the ramp and journalled therein at its outward end is a lead screw which is rotatively driven by a rotary power motor mounted to the inner end of the ramp. A nut threadedly engaging the screw is hingedly mounted to the lower end of a step riser which is hinged at its upper end to the bus floor so as to swing up to a position co-planar with the ramp when the ramp is fully extended. A bell crank having an arm underlying the ramp is actuatable by a fluid motor to swing the inner end of the ramp and lower end of the riser upwardly to their co-planar relation when the motor comes into abutment with the nut during outward extending movement of the ramp. |
