Abstract: The invention relates to a disc brake to be opened by torque, the disc brake being arranged between a drive shaft (3) and a driven shaft (11) and comprising a brake wheel (12) arranged on the driven shaft (3) non-rotatably in the peripheral direction; a friction surface (15) arranged to cooperate with the brake wheel (12); a spring device (14) arranged to press the brake wheel (12) axially against the friction surface (15) and means (19 to 21) causing, by the action of the torque and torsion of the drive shaft (3) and a possible counter-torque of the driven shaft (11), the brake wheel (12) and the friction surface (15) to drift axially apart and, accordingly, the braking coupling between them to loosen against the spring force of the spring device (14), whereby the drive shaft (3) and the driven shaft (11) are interconnected in such a way that they may turn a restricted rotational angle with respect to each other and that means for causing said axial displacement and for loosening the braking coupling compris

Abstract: A hydraulic braking system for a towed vehicle provides actuation of the hydraulic pump motor of the towed vehicle responsive to an electrical switch which is closed upon application of the brake pedal of the towing vehicle. However, even after actuation of the hydraulic pump, the towed vehicle brakes are only able to be applied in response to sensed relative movement of the towing and towed vehicle toward each other. A break-away switch sets the trailer brakes in the event of accidental separation of the towed vehicle from the towing vehicle. The control valve may be used in other situations to control a hydraulic pump and associated hydraulic braking system.