| 摘要 |
A jack in which a base plate is pivotable on an upright to a bottom surface. A supporting arm is also pivotable on the upright, and is actuated for being pivoted. The base plate is held in a predetermined position by a spring which has two sections. A first section of the spring rests against the upright and the base plate, whereas the second section of the spring rests against the base plate and an end of the supporting arm when this arm is completely folded up against the upright. The second section of the spring, furthermore, generates a spring torque which is directed opposite to the spring torque that is generated by the first spring section. The spring torque of the second spring section, moreover, exceeds the spring torque of the first spring section.
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