Dual power brake booster

A brake booster assembly for power actuation by first and second independent power sources and comprising:

• a first power section for power actuation by the first power source and having a first input and first and second outputs and a first movable power wall connected to move said outputs as a unit under power in response to movement of said first input, and means for moving said second output relative to said first output by movement of said first input when said first movable power wall has insufficient power to move;
• a second power section for power actuation by the second power source and having second and third inputs, a second movable power wall, a third output movable by said second movable power wall, and valve control means including a valve for control of the power actuation of said second power section, said valve having one valve element on said second movable power wall and moving therewith and another valve element on said second input for controlling the application of power to said second movable power wall;
• said second output being connected to move said second input and said first output being connected to move said third input whereby said second power section valve is actuated by relative movement between said valve elements only when said second output and said second input are moved by said first input relative to said first output and said third output.

A brake booster assembly having an input member and an output member;

• a first power section having said input member as the input thereof;
• a second power section having said output member as the output thereof;
• said first power section having two parallel-acting outputs which are also inputs for said second power section;
• first control means for said first power section including first valve means controlling the actuation of said first power section in accordance with movement of said input member and subject to power provided thereto, said first control means having means mechanically transmitting force from said input member to one of said outputs and inputs upon run-out of power in said first power section to move said one output and input relative to the other of said outputs and inputs;
• second control means for said second power section including second valve means controlling the power actuation of said second power section in accordance with the movement of said second power section one input relative to said second power section other input as aforesaid and subject to power provided thereto, said second power section one input being operatively mechanically engageable with said output member in force transmitting relation to provide a mechanical drive path through said power sections from said input member to said output member upon run-out of power in said second power section.

In a brake booster having a power wall;

• valve means selectively controlling the pressure differential across said power wall to control said booster, said valve means including an input member;
• output mechanism slidably connected to said power wall;
• and reaction means connecting said output mechanism and said power wall and said input member in force transmitting relation whereby in power operation a minor portion of the total reaction force from said output mechanism is received by said input member and a major portion of the total reaction force from said output mechanism is received by said power wall;
• the improvement comprising:
• said output mechanism including a sleeve having one end slidable in said power wall and abutting said reaction means, and a plunger slidably received in said sleeve and having one end formed with a shoulder abutting said reaction means and a reduced section extending through said reaction means in abuttable force transmissible alignment with said valve means input member, the other ends of said sleeve and said plunger being outputs of said output mechanism;
• said sleeve and said plunger moving axially as a unit during powered movement of said power wall, said valve means input member engaging said plunger upon run-out of power and mechanically moving said plunger axially relative to said reaction means and said power wall and said sleeve upon further movement of said valve means input member.