Hydraulic unit and electric power tool to which the hydraulic unit is incorporated

Abstract

A hydraulic unit ( ) includes a case ( ) having an axially slidable top cap ( ) at the rear end thereof The hydraulic unit further includes a spindle ( ) having communicating holes ( ) axially formed therein and a column ( ) which is inserted into the case. The column of the spindle includes a through-hole ( ) formed therein and is rotatably supported by the top cap's closed-end hole ( ). A pair of fluid chambers ( ) and another pair of fluid chambers ( ) are defined between the case and the spindle. The communicating holes ( ) are capable of placing the fluid chambers ( ) in communication with a bottom surface ( ) of the closed-end hole ( ) via the through-hole ( ) when the fluid pressure in the fluid chambers ( ) reaches or exceeds a threshold. Additionally, a disk spring ( ) and a top nut ( ) are fitted around the cylindrical connector ( ) such that the biasing force of the disk spring presses the top cap toward a liner of the case ( ) so as to seal the fluid chambers ( ) and determine the aforementioned threshold as desired.