Patent ID: 7159953

Claim:
A reaction device for use in a servomotor for an assisted braking, comprising a substantially incompressible reaction disk and a housing for receiving said reaction disk, first means driven by a brake pedal to initiate a brake application, second means including an output push rod with a head thereon for applying a reaction force application to said reaction disk, said output push rod having an annular bearing surface thereon and third means including a pneumatic piston driven motive means for generating a braking assistance force that is applying through said reaction disk to output push rod to effect a brake application, characterised in that said housing for receiving said reaction disk comprises an elastically deformed cap defined by a first cylindrical inlet having a first diameter D 1 for receiving a first end on a input push rod of said first means such that a first gap is present between said first end and the reaction disk, a second cylindrical inlet having a second diameter D 2 for receiving an second end on an output distributor plunger that constitutes said first force-applying means such that a second gap is present between said annular bearing surface and a face on the second diameter and a third diameter D 3 located between said first and second inlets with D 3 >D 1 >D 2 , said input push rod responding to an actuation force by moving to close said first gap and bring said first end into engagement with said reaction disk activating a valve to develop an operational force for said motive means, said operational force being applied to said cap to initially directly move said output push rod by acting through the reaction disk until a reaction force compresses said reaction disk causing said cap to deform and allow said face on said second diameter to engage said bearing surface on said output push rod and close said second gap such that a ratio of input force to output force is a function of the ratio of D 2 and D 1 to each other and to D 3 .