Image Number 10 for United States Patent #4159755.
A safety hydraulic brake system for automotive vehicles which includes a control cylinder having an inlet connected to a hydraulic pressure source, and first and second outlets connected to brake cylinders at front and rear wheels, respectively. A valve is located at each outlet and normally allows pressurization of the front and rear wheel cylinders upon actuation of the hydraulic pressure source. First and second pistons, each having a by-pass valve, are slidable in the control cylinder. The pistons and by-pass valves are operable, when there is a loss of brake pressure in the lines to one set of brake cylinders, to effect closing of the control cylinder valve to that brake cylinder set. This allows brake pressure to be maintained at the other set of wheel cylinders and the vehicle to be safely braked. In addition, for heavy vehicles such as buses and trucks, an additional control cylinder device can be incorporated providing separate braking systems for each of the rear wheels so that loss of brake pressure to one rear wheel does not affect brake pressure at the other. Further, the system is designed to accomodate ready air bleeding from the brake lines.