Patent ID: 6520064
Filing Date: 2003-02-18
Classification: B60T

Abstract:
A pneumatic servomotor for an assisted braking having a housing with a first variable-volume chamber and a second variable volume chamber therein, said first chamber being connected to said second chamber, said first chamber having a first fluid pressure therein, a control rod driven by travel of an input force on a brake pedal to effect a brake application, tight sealing means responding to travel of said control rod for allowing a first flap to move and isolate said first chamber from said second chamber and a second flap to move and allow a pressurised assist fluid with a second pressure to be communicated to said second chamber to creating a pressure differential between said first chamber and said second chamber, a pneumatic piston being driven by said pressure differential to effect a brake application on movement of said control rod, and means for slowing down an initial travel of said pneumatic piston at the beginning of said brake application without interfering with the efficiency of subsequent assisted braking during a brake application, characterised in that said means for slowing down said initial travel of said pneumatic piston comprises a lip that defines at the beginning of a brake application a radially-inner initial thrust chamber that receives said pressurised assist fluid and after a predetermined travel of said pneumatic piston allows communication of said pressurised assist fluid with said second chamber in the creation of said pressure differential, said with lip providing a one-way isolation permitting the discharge of said assistance fluid from second chamber on termination of said input force being applied to said brake pedal.