| 摘要 |
The invention relates to a platform (1) having a platform (1) and at least three legs (2) movable in vertical direction with respect to the platform (1), the legs (2) being connected to the platform (1) by a lifting and locking mechanism (8,9,17,18,14) having locking bars (8,9) for holding the platform (1) with respect to the legs (2) and lifting jacks (17,18,14) for moving the legs (2) with respect to the platform (1) both locking bars and lifting jacks having elements (8,9,17,18) which can move in and out of engagement with the legs with clearance in vertical direction in recesses (11), safety structure being provided to check the completion of the movements of the elements, the safety structure having a time relay (t1,t2) in the control circuit of the jack system which relay (t1,t2) interrupts the circuit when after a set time which is shorter than the time needed to traverse the clearance in recesses (11), said elements ( 8,9,17,18) have not reached their final positions, while a recorder (12,13,19,20) of all final positions of the elements (8,9,17,18) also interrupts the circuit when the elements (8,9,17,18) have reached their final positions and also switches off the time relay (t1,t2). |
