An anti-skid apparatus for installation in a vehicle braking system between a master cylinder and a wheel brake cylinder. The anti-skid apparatus includes a hydraulic power pressure source connected to a fluid reservoir of the master cylinder to produce a hydraulic power pressure higher than a braking pressure applied to the wheel brake cylinder from the master cylinder, a regulator valve connected to the pressure source to control the power pressure in dependence upon a hydraulic pressure created in the master cylinder in braking operation, a first switchover valve disposed within a braking circuit connecting the master cylinder to the wheel brake cylinder and being arranged to be intermittently activated when a road wheel tends to be locked, the first switchover valve being connected to the reservoir to connect the wheel brake cylinder to the reservoir in its activated condition, a second switchover valve disposed within the braking circuit between the master cylinder and the first switchover valve and being arranged to be activated when the road wheel tends to be locked, a second switchover valve being connected to the regulator valve to interrupt the flow of pressurized fluid from the master cylinder and permit the flow of pressurized fluid from the regulator valve to the wheel brake cylinder through the first switchover valve.

An auxiliary-energy-operable hydraulic brake system for automotive vehicles, in which a valve device connected to a pressure medium source and to an unpressurized reservoir and controlling an actuating pressure is operable by an actuating element which, irrespective of its direction of actuation, may be pressurized by a reaction force depending on the actuating pressure. The valve device is operable electromagnetically and controllable by an electric switching device connected with the actuating element.

A parking brake system is provided which includes a dual solenoid operated valve located in series with the emergency brake control valve of a hydraulically operated brake system. The dual solenoid valve is operable to either one of two mechanical detent positions so that positioning of the valve is retained in the event of loss of power. The dual solenoid valve is controlled by the vehicle operator from the transmission console and removes fluid pressure from the brakes when actuated to a PARK position. An electronic control unit is provided for sensing the speed of the vehicle and the pressure in the hydraulic line to the brakes and provides a PARK enabling signal when the vehicle speed is below a predetermined amount. When a gear is selected at the console the dual solenoid valve is actuated to a position permitting fluid pressure to be applied to the brakes and effectively returns control of the brakes to the emergency brake control device. A pressure sensor is provided in the line to the brakes and is used to provide feedback to the driver and to control transmission shifting.

In a brake system having a master brake cylinder, in which at least one brake piston, which can be acted upon with brake pressure by a piston rod, forms a brake chamber from which a brake line leads to wheel brake cylinders, at least one valve is incorporated into the brake line for blocking the brake line upon anti-skid control, and at least one pressure chamber, formed by an additional piston, of an additional plunger for feeding brake fluid via a line communicates with the brake line. From the brake line upstream of the valve, a return line for the brake fluid upon anti-skid control leads to the brake chamber of the additional plunger. A valve, in particular a 2/2-way valve, is incorporated into the return line.