| 摘要 |
This invention deals with a jack which can be incorporated in the length of a pit prop, can be used as a flat jack or can be used as a pulling jack. Essentially the jack is composed of a plunger held in a stirrup by a conical anvil and a pointed screw engaging in opposed conical recesses in the plunger. By turning the screw the stirrup is caused to move transversely to the plunger axis and at the same time the plunger moves up and down in the stirrup. If used as part of a pit prop, the plunger forms telescopic extension of the prop and the stirrup rests on an end of the prop. Acting as a jack the top of the plunger acts on one surface and the stirrup on another. For pulling purposes the plunger is attached to the element to be pulled. The device of the invention generates large forces, but is only suitable for small displacements.
|
