Brake pressure-difference warning system for vehicles

A brake pressure-difference warning system operatively associated with a dual master brake cylinder having two independent brake lines, which comprises:

• a housing provided with an axial bore defined therein;
• a stepped piston slidably disposed within said bore and provided with a small diameter portion and a large diameter portion;
• a proportioning valve assembly disposed within one of said brake lines;
• a first fluid chamber defined within said housing at one end of said small diameter portion of said stepped piston;
• a second fluid chamber defined within said housing and within said one brake line;
• a third fluid chamber defined within said housing at one end of said large diameter portion of said stepped piston and disposed within the other brake line;
• said first fluid chamber being in fluidic communication with said second fluid chamber through means of said proportioning valve assembly, said proportioning valve assembly thereby controlling pressurization of said first chamber and said piston at said one end thereof;
• a seal member provided upon said small diameter portion of said stepped piston and interposed between said first and second fluid chambers;
• switch means operatively connected to said stepped piston for indicating a fluidic failure within one of said brake lines;
• said stepped piston having a predetermined configuration, and the stepped portions thereof having a predetermined area ratio with respect to each other, such that said stepped piston is axially movable within said bore when each of said first, second and third fluid chambers is subjected to a fluidic failure;
• and
• when said proportioning valve is inoperatively seated upon its valve seat and said second and said third fluid chambers are not subjected to a fluidic failure, whereby the hydraulic pressure within said first chamber is lower than the normal pressure supplied to said second chamber, said switch means is actuated and fluid communication between said first and said second fluid chambers is established without passing through said proportioning valve assembly.