Hydraulic pressure booster having booster piston and valve mechanism associated with mechanically operated and electrically controlled pressure regulators

A pressure boosting device provided in a hydraulically operated system wherein the pressure boosting device is connected to a mechanically operated pressure control device, an electrically controlled pressure control device and a hydraulically operated actuator, said mechanically operated pressure control device producing a manually controlled hydraulic pressure whose level is regulated depending upon an operating force acting on the mechanically operated pressure control device, while said electrically controlled pressure control device producing an electrically controlled hydraulic pressure whose level is electrically regulated, said pressure boosting device comprises:

• a stepped booster piston for boosting said electrically controlled hydraulic pressure produced by said electrically controlled pressure control device, so that the boosted electrically controlled hydraulic pressure is applied to said hydraulically operated actuator;
• and
• a valve mechanism operated according to a movement of said booster piston, said valve mechanism having an open position in which said actuator communicates with said mechanically operated pressure control device, and a closed position in which said actuator is disconnected from said mechanically operated pressure control device and in which said booster piston is permitted to boost said electrically controlled hydraulic pressure, said valve mechanism being placed in said open position when said booster piston is placed in an original position thereof, and in said closed position when said booster piston is moved from said original position.