Electronic emergency brake load weigh device

摘要

An electronic load weigh device is used with a railcar truck control unit. A relay valve provides to a brake cylinder a pressure proportional to the pressure impinging upon its control port. A first feedback signal is indicative of the pressure at the control port. A second feedback signal is indicative of the load borne by the truck. A pressure switch opens when pressure within a trainline changes to a level indicative of an emergency. By controlling the opening and closing of application and release magnet valves, a controller controls the pressure impinging on the control port and thereby service braking of the wheels of the truck. The load weigh device includes (i) circuitry for electronically compensating for the load during braking and (ii) a mechanism for granting the circuitry exclusive control over the magnet valves. Should such emergency occur, the mechanism responds to such emergency by disconnecting the controller from the magnet valves. This gives the circuitry exclusive control over the magnet valves. The circuitry compensates for the load borne by the truck during emergency braking by selectively opening and closing the magnet valves, according to predetermined criteria using the feedback signals, thereby controlling the magnitude of the pressure impinging upon the control port. Absent such emergency, the mechanism responds to such absence by connecting the controller to the magnet valves whereby such service braking on the truck is normally controlled, yet the circuitry is still enabled to compensate for the load during such service braking.