Servomotor for braking assistance

Claim 1

A braking assistance servomotor comprising: a casing, a piston structure dividing said casing internally into two chambers, distribution valve means situated in a tubular valve body firmly fixed centrally to said piston structure and actuated by an input member to create selectively a pressure differential between said chambers, said distribution valve means comprising: a plunger mounted so as to slide axially in said valve body, coupled to said input member and defining at one end a movable valve seat; a valve body seat formed internally by said valve body, concentric with said movable valve seat; a valve member mounted in said valve body and resiliently biased toward said valve body seat and movable valve seat; a return spring supported in said valve body and biasing said input member in a direction away from said valve body and movable valve seat, and further comprising a retaining member having a first portion extending into a radial recess in said valve body for cooperation in abutment with a peripheral shoulder of said plunger and a second portion outside said valve body for cooperation with a stationary component in fixed relationship relative to said casing, said retaining member having the second portion pivotingly supported on said valve body by shaft means mounted in said valve body and extending perpendicular to a direction of sliding of said plunger, said radial recess having an axial extension such that, when said retaining member is pivoted about said shaft means in a direction toward said valve member under the effect of said return spring, a zone of said first portion of said retaining member comes into abutment with a corresponding radial end surface of said radial recess adjacent said valve member and remote radially from said shaft means, so as to determine for said plunger a position of maximum retraction relative to said valve body seat, said retaining member comprising a plate shaped so that said first portion has a U-shaped configuration with a free end cooperating in abutment with said peripheral shoulder of said plunger and said second portion also has a U-shaped configuration with arms extending about each side of said valve body and beyond said free end of said first portion, said arms having free arm ends journaled on said shaft means mounted in said valve body, and said second portion of said retaining member formed centrally with a finger bent substantially perpendicular to the general plane of the plate and in said direction toward the valve member for abutment with said stationary component.