Importance

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Abstract

A tandem brake booster having a housing with a first front chamber separated from a first rear chambers by a first wall and a second front chamber separated from a second rear chamber by a second wall. The first and second front chambers are connected to the first and second rear chambers through passages in a hub which retains a control valve. In a first or ready mode of operation, the first and second front and rear chambers have a substantially identical first fluid pressure while in a second or actuation mode of operation, the control valve responds to an input force to allow a second fluid pressure to be communicated to the first and second rear chambers and create a pressure differential with the first fluid in the first and second front chambers. The pressure differential develops an output force which moves the first and second walls as a function of the input force applied to the control valve. The control valve on termination of the input force returns to the first mode of operation as the second fluid pressure is replaced in the first and second rear chambers by the first fluid pressure. The hub member which retains the control valve has an axial bore. A junction is formed within the axial bore with first and second passages which connect the first front chamber with the first rear chamber to define a first flow path and with third and fourth passages which connect the second front chamber with the second rear chamber to define a second flow path. The first and second flow paths independently allow the second fluid pressure to be simultaneously evacuated from the first and second rear chamber as the control valve returns to the first or ready mode of operation.

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First Claim