Abstract: A freight brake control valve device having an improved quick service function achieved by providing an additional volume upstream of the quick service limiting valve with which the brake pipe fluid under pressure is equalized during the second stage of quick service to achieve an intensified secondary quick service reduction of brake pipe pressure. Further, a smooth and continuous local reduction of brake pipe pressure occurs without any time lag at the time of transition from preliminary to secondary stage quick service. In a first embodiment of the invention, an exhaust passage separate from the brake cylinder exhaust passage is provided to assure venting of this additional volume in the event the brake cylinder retainer valve is set up. In a second embodiment, the additional volume is vented via the brake cylinder exhaust passage.

Abstract: A two-pressure brake control valve for a single stage releasing indirectly acting airbrake particularly for railway vehicles has a service brake portion in which is a main control element to control a valve so as to subject a brake cylinder to the action of air from an auxiliary air reservoir in response to a decrease in pressure in the brake line per unit time below a predetermined value. An emergency brake portion has a main piston as a main control element and an auxiliary piston is mounted on this main piston. The main piston controls a second valve to further subject the brake cylinder to the action of air from an emergency brake reservoir in response to a decrease in pressure in the brake line per unit time exceeding the predetermined value. A service brake accelerator valve is actuated by the auxiliary piston in response to a variation of pressure in the brake line during a service braking operation when the main piston is in an inactive position.