| 摘要 |
A wedge member has a front end and diverges in direction rearwardly therefrom. The wedge member is hydraulically displaceable in longitudinal direction and has a pair of opposite outer surfaces. A pair of spreading members which are fixed with respect to the longitudinal displacement of the wedge member, overlie the outer surfaces thereof in engagement with them so that they spread radially when the wedge member is displaced forwardly. Mating tongues and grooves are provided in the wedge member and the spreading members and matingly interengage when the wedge member is rearwardly displaced. |
