Return spring arrangement for brake booster

Abstract

A brake booster (,) having a housing (,) with a control valve (,) located in an axial bore (,) of a hub (,) carried by a movable wall (,). The movable wall (,) separates the interior of the housing into a first chamber (,′) and a second chamber (,′). The control valve (,) in a first mode communicates the first chamber (,′) with the second chamber (,′) to provide for equal pressures therein and in a second mode communicates the second chamber (,′) with a surrounding environment to create a pressure differential across the movable wall (,). A reaction member (,) carried by the movable wall (,) communicates an operational force created by the pressure differential into an output push rod (,). After the operational force overcomes a return spring arrangement (,), the output push rod (,) moves pistons (,) in a master cylinder (,) to correspondingly pressurize fluid therein which is supplied to wheel brakes to effect a brake application. The brake booster (,) is characterized by the return spring arrangement (,) having a first spring (,) with a right hand spiral and a second spring (,′) having a left hand spiral. The first spring (,) is secured to a base (,) of a retainer (,) and to an end cap (,) to hold the second spring (,′) in a concentric relationship between the end cap (,) and base (,). A housing (,) of a master cylinder (,) engages the end cap (,) to compress the return spring arrangement (,) to an installation height such that the movable wall (,) is located in a ready rest position.