GB194974A - Improvements in multiple control apparatus for electric railways - Google Patents

Abstract

194,974. Akt.-Ges. Brown, Boveri, et Cie. April 1, 1922, [Convention date]. Controllers, pneumatic actuating mechanism; master control systems.-Multiple unit controllers on electric trams are operated by compressed air cylinders a<1>, a<2> furnished with electromagnetically-operated valves d, e which admit compressed air to a cylinder when the corresponding magnet is energized and exhaust the cylinder when the magnet is de-energized. A master controller S co-operating with hunting-switch brushcontacts i, h, k causes a rack b to be moved any selected number of steps to the left from the zero position shown, the main controller being driven through a pinion c. The stoppage at the selected position is brought about by the agency of the hunting-switch contacts, which results in the admission of compressed air to the cylinder a<2> without exhausting the compressed air from the cylinder a<1>. When the master controller is turned to zero, all the valve magnets are de-energized, but the valve e is kept down by a separate spring-piston q so that compressed air in the cylinder a<2> returns the rack to the position shown. One double-acting cylinder may replace the two single-acting cylinders. Automatic control of the rate of starting may be obtained by arranging the hunting-switch contacts in conjunction with a current-limit relay which interrupts the step-by-step movement of the rack until the motor current is sufficiently reduced. In addition, a push button relay may be provided to allow the driver to continue the movement of the rack in single steps.