| 摘要 |
A winch intended for mounting at ground level over a vertical shaft communicating with an underground duct, and for drawing equipment through the duct using a chain, comprises a pair of rams (10, 12) coupled together in a parallel spaced apart relationship by a first chain gripper assembly (16) mounted on the ram cylinders, and a second gripper assembly (22) mounted on the ends of the ram pistons (20). Each gripper assembly (16, 22) has a central passageway for receiving a chain disposed between and parallel to the rams (10, 12), each passageway having associated therewith a respective pair of pivotable clamping jaws which act to prevent relative downward movement of the chain but to allow relative upward movement of the chain. When the rams (10, 12) are reciprocated first one, then the other gripper assembly clamps the chain so that with repeated reciprocation the chain is caused to move upwards in a stepwise manner. A pivotal mounting device (14) defining two axes of rotation with respect to the supporting base structure allows the rams (10, 12) automatically to take up a position parallel to the chain obviating the need for accurate positioning of the winch. |
