Fluid pressure operated servo-devices

Claim 1

A fluid pressure motor device comprising a casing having a movable wall therein dividing it into two chambers to provide differential fluid pressures therein to move said wall and actuate a vehicle braking mechanism, said movable wall including a rigid disc portion, a first push rod member connected thereto to move said rigid wall, said rigid disc portion having a central recess therein, an annular plate member disposed in said recess, a second push rod member connected to the inner end of said plate member for actuating the master cylinder of a vehicle braking system, the outer circumferential portion of said plate member being sandwiched between a stop means and a compressible elastomeric ring member disposed in said recess, a plurality of radial levers disposed in said recess, and held against the bottom of said recess by said elastomeric ring member, said annular plate member having an arcuate surface extending in a direction toward said radial levers, said elastomeric ring member having a predetermined thickness of sufficient dimension to maintain said plate member out of contact with said radial levers until said first push rod member is moved a predetermined distance to compress said ring member and move said second push rod member a predetermined distance to apply a braking operation on a vehicle.