Hydraulic boosting apparatus in braking system

Claim 1

A hydraulic boosting apparatus in a braking system comprising, a housing, a booster cylinder in said housing and having an inner surface, a booster piston movably disposed in said booster cylinder at the center thereof, a first chamber defined between one end surface of said booster piston and the inner surface of said booster cylinder, a first bore disposed in said housing coaxially of said booster cylinder, a free spool disposed for movement in said first bore coaxially with said booster piston, said free spool having a portion at one end thereof extending into said booster cylinder, an operating spool movable with respect to said free spool and coaxially disposed in said first bore, a second chamber defined in said first bore between said free spool and said operating spool, said first chamber being out of fluid communication with said second chamber at all times, a valve means disposed in a second bore in said housing and having first and second operating chambers at the opposite ends thereof, said first operating chamber being in open communication with said first chamber for biasing the valve means in one direction and said second operating chamber being in open communication with said second chamber for biasing the valve means in a direction opposite to said one direction, and an accumulator means containing pressurized hydraulic oil and connected to said first chamber through said valve means when the pressure in said second operating chamber is sufficiently higher than the pressure in said first operating chamber, thereby causing said valve means to move in said opposite direction.