A control valve (3) of a compressed air system of a vehicle has a control piston (22), guided in an axially movable manner in a housing cylinder (25), two pressure chambers (32, 34) separated from one another by the control piston (22), which is sealed by at least one sealing ring (37) arranged on the outer circumference of the control piston (22). The sealing ring (37) is a radial sealing ring having an axial length which substantially corresponds to the axial thickness of the control piston (22). The sealing ring (37) has, on each of the two axial edges thereof, one respective radially obliquely outwardly directed sealing lip (39, 40) which is in contact with the inner wall (38) of the cylinder (25), and that a plurality of guide members (50) distributed over the circumference and formed between the two sealing lips (39, 40) on the sealing ring (37).

A brake module for a hydraulically braked tractor coupled to a pneumatically braked trailer has a trailer control valve connected via hydraulic control inlet to a hydraulic pressure line leaving a master brake cylinder, and via pneumatic inlet to a compressed air reservoir. Hydraulic control pressure determines pneumatic output pressure level at a trailer control valve pneumatic outlet. The brake module has a break-off prevention module which, if the control line leaks or separates from the trailer control valve relative to the trailer brake system, closes a supply pressure coupling head supply line and causes trailer brake system venting. The break-off prevention module has a pneumatic supply pressure inlet and a pneumatic tear-off control pressure inlet connected to the air reservoir independently of trailer control valve pressure inlets. Supply pressure inlet supply pressure passes through the break-off prevention module and feeds to a trailer control valve pneumatic supply pressure inlet

A valve system includes an isolation check valve delivering pneumatic fluid as a supply pressure, a double-check valve adapted to deliver a braking demand control signal of the pneumatic fluid based on a higher of a first braking demand in a first pneumatic braking circuit and a second braking demand in a second pneumatic braking circuit, and a control module. The control module is adapted to receive the supply pressure as a control module supply pressure of the pneumatic fluid, receive a control module control pressure of the pneumatic fluid based on the braking demand control signal, and deliver a control module delivery pressure of the pneumatic fluid based on the control module supply pressure and the control module control pressure. A park control module selectively transmits the pneumatic fluid at the supply pressure based on a park brake control signal.

A valve system includes a control module on a tractor portion of a vehicle adapted to receive a supply pressure as a control module supply pressure of the pneumatic fluid, receive a control module control pressure of the pneumatic fluid, and deliver a control module delivery pressure of the pneumatic fluid based on the control module supply pressure and the control module control pressure. A park control module selectively transmits the pneumatic fluid at the supply pressure based on a park brake control signal. A supply glad-hand fluidly communicates the selectively transmitted supply pressure of the pneumatic fluid to supply a brake on an associated trailer portion of the vehicle. A control glad-hand fluidly communicates the control module delivery pressure of the pneumatic fluid to control the brake on the associated trailer portion of the vehicle. An exhaust valve, which fluidly communicates with both the selectively transmitted supply pressure and the control module delivery pressure, exhausts the control module delivery pressure of the pneumatic fluid from the control glad-hand.

An electropneumatic valve assembly is provided for actuating a parking brake function of an electropneumatic brake system of a commercial vehicle. The assembly includes a parking brake valve unit which receives supply pressure via a supply pressure path. A pneumatically self-holding trailer valve unit is connected to the supply pressure path and has a pneumatically switchable trailer supply valve. The supply valve provides a trailer supply pressure to a trailer supply port in dependence on an electronic trailer brake signal. The parking brake valve unit has a pilot valve unit and a main valve unit and the pilot valve unit outputs a parking brake control pressure at the main valve unit. The main valve unit outputs a parking brake pressure at a spring brake port. The valve assembly has a compensation valve to maintain the parking brake control pressure outputted at the main valve unit to compensate for valve leakage.