| 摘要 |
The furniture has a lower chassis including a drive and steering wheel (15) and a support (17) provided with a push arm (19) that is rotatably mounted around a vertical rotational axis (Y). The arm is elastically stressed towards the bottom using a helical spring (23) and co-operated with locking units (31) for attaining two predetermined positions that are angularly shifted to 90 degree. The wheel is co-operated with a ramp (35) that is situated above one of the positions, for permitting the arm to attain a third predetermined position at which the wheel is disengaged from ground. |
