| 摘要 |
An actuator for a power chuck has a hollow actuator housing having a rearwardly extending housing tube that is centered on an axis and that has a closed rear end. This tube is formed with a pair of axially spaced and radially inwardly open grooves both having axial lengths equal at least to a predetermined axial distance, and the tube is further formed at these grooves with respective radially throughgoing apertures. A piston subdivides the interior of the housing into a pair of compartments and has a stem extending axially rearwardly in the tube. This piston is axially displaceable in the housing through an axial stroke at most as long as the distance corresponding to the axial lengths of the grooves. The piston is formed with a pair of throughgoing passages each having one end opening at the stem into a respective one of the grooves and another end opening into a respective one of the compartments. The piston is provided with a pair of check valves set up so as to prohibit flow between the ends of the passages except when either of the passages is pressurized from the respective one end. A collar surrounds this tube and is rotatable thereon about the axis. This collar is formed with a pair of angular inwardly open grooves respectively aligned with the apertures and is provided with a pair of connections respectively opening into the inwardly open grooves of the tube. |
