Hydraulic brake booster

Claim 1

In combination with a hydraulic brake booster for a vehicle having a brake activating means, a master cylinder for supplying pressure to the wheel cylinders of the vehicle, a hydraulic circuit for circulating pressurized fluid from a fluid pressure source to a reservoir by way of a hydraulic power control device comprising: a housing for interposition within said hydraulic circuit between said pressure source and said power control device said housing being provided therein with a cylindrical bore and thereon with an inlet port, an outlet port and a drain port respectively in communication with said pressure source, said power control device and said reservoir; a power piston reciprocable within said cylindrical bore of said housing for forming at one side thereof a power chamber and at the other side thereof a drain chamber in communication with said drain port, said power piston being operatively connectible at one end thereof with said master cylinder and being provided therein with a bore opening toward said power chamber; a control piston reciprocable within said bores of said housing and said power piston to control interconnection between said power chamber and said drain chamber, said control piston being operatively connectible to said brake activating means; a first passage means for connecting said inlet port to said power chamber through said bore of said power piston; a control means for selectively closing and opening the interconnection between said power chamber and said drain chamber in response to movement of said control piston; and means disposed within said first passage means for closing the communication between said power chamber and said inlet port when said power chamber is communicated with said drain chamber and opening the communication between said power chamber and said inlet port when said power chamber is isolated from said drain chamber by means of said control means; the improvement which comprises a second passage means for connecting said inlet port with said power chamber independently of said first passage means; a first flow regulating means disposed within said second passage means for throttling the flow of fluid supplied from said inlet port to said power chamber when said power chamber is isolated from said drain chamber by means of said control means in response to movement of said control piston; and a second flow regulating means disposed within said second passage means between said inlet port and said first flow regulating means for controlling the flow of fluid from said inlet port to said outlet port and the flow of fluid from said inlet port to said power chamber through said first flow regulating means.