Pneumatic booster with floating reaction disc and dynamically cancellable reaction

A pneumatic brake booster comprising:

• a rigid casing;
• a moving partition for delimiting in a leaktight manner said rigid casing into a front chamber and a rear chamber, said from chamber being subject a first a front chamber and a teat chamber being selectively connected to said front chamber to receive said first pressure or a second pressure, said second pressure having a higher pressure than said first pressure;
• a pneumatic piston moving with said moving partition;
• an axial operating rod moving in said pneumatic piston as a function of an input force selectively resisting a reaction force and oriented in an axial actuating direction pointing toward said front chamber, said reaction force urging said operating rod toward a return position while the input force urges said operating rod toward an actuating position;
• a plunger slidable within said pneumatic piston by said operating rod;
• a three-way valve connecting said rear chamber to said front chamber when said operating rod is in a position of rest and subjecting said rear chamber to said second pressure when actuated by movement of said operating rod toward an actuating position;
• and
• force transmitting means for receiving and passing at least a portion of said input force transmitted by a front face of said plunger and a boost force exerted by a front face of said pneumatic piston when said three-way valve is actuated, said three-way valve comprising:
• a pushrod having a first end adjacent said plunger capped by a cup which houses a reaction disc, said reaction disc having a first face for receiving said input force and boost force and a second face for bearing against said cup;
• and stop means for limiting the sliding of said plunger with respect to said cup to a predetermined travel;
• said force transmitting means being characterized by an intermediate member mounted to slide axially with respect to said plunger with respect to said pneumatic piston and driven by said plunger with respect to said piston over a driven distance which exceeds said predetermined travel, said intermediate means being at least partially inserted between said front face of said piston and said first face of said reaction disc for passing said boost force to said reaction disc;
• and stop means borne by said plunger and said intermediate member comprising a snap ring secured to said plunger and mounted to slide in a groove of said intermediate member to define a maximum excursion of the plunger with respect to said intermediate member.