Patent ID: 6901843

Claim:
A pneumatic brake-booster comprising: a casing having a front chamber ( 1 ) connected to a source of vacuum ( 2 ) and a rear chamber ( 3 ) selectively connected to a high-pressure inlet ( 5 ); a sealed moving partition ( 6 ) located between said front chamber and said rear chamber to provide an output force; a brake rod ( 9 ); a hydraulic braking circuit ( 10 ) for receiving said output force to effect a brake application; a first reaction device ( 24 , 25 ) carried by said moving partition ( 6 ) for receiving a reaction force from said hydraulic braking circuit ( 10 ) during a brake application; a moving gear ( 8 ) being located between said first reaction device ( 24 , 25 ) and said hydraulic braking circuit ( 10 ) a device ( 4 ) through which a high-pressure fluid is communicated into the rear chamber ( 3 ) to move said sealed moving partition ( 6 ) and effect a desired brake application; and a second reaction device ( 29 - 34 ) for carrying the moving gear ( 8 ) along with the moving partition ( 6 ) and characterized by first spring ( 34 ) and a second spring ( 32 ) that are located in series between said hydraulic braking circuit ( 10 ) and the first reaction device ( 24 , 25 ), said moving gear ( 8 ) being mechanically connected to said second reaction device ( 29 - 34 ) such that during a brake application a reaction force received by said first reaction device ( 24 , 25 ) opposes an input force applied to said brake rod ( 9 ) by being communicated through said first spring ( 34 ) until a predetermined reaction force compresses said first spring ( 34 ) and said second spring ( 34 ) is moved into engagement with said moving partition ( 6 ) such that a portion of said input force is directed into the moving partition ( 6 ) such that the corresponding output force is increased to effect said desired brake application.