GB1442652A - Braking systems for electrically operated escalators - Google Patents

Abstract

1442652 Emergency brakes HITACHI Ltd 1 Oct 1973 [29 Sept 1972 28 March 1973] 45683/73 Heading F2E A braking system for an electrically-operated escalator includes apparatus for selecting the direction of travel of the escalator, brakes for frictionally stopping the escalator driving mechanism in response to a signal from an emergency switch, and braking-pressure control-apparatus for applying a first braking pressure in the event of downward travel, and a second braking pressure, which is less than the first, in the event of upward travel. In Fig. 4, component 13 is part of a pivoted arm on the right of which is secured a brake shoe (not shown) co-operating with the exterior of a drum on the shaft of a motor driving an escalator. Component 15 is a brake-applying spring; a solenoid (not shown) mounted between the end of arm 13 beyond its pivot and the end of a similar spring-loaded brake arm is energized to pivot the arms against their springs to release the brake. A controlling circuit, (Fig. 5, not shown), includes an emergency switch and a two-way switch, the latter being used to govern the direction of travel (up or down) of the escalator. In operation of the escalator, the emergency switch is first closed, and the two-way switch is closed to drive the escalator in, for present purposes, the upward direction; in consequence, the brake solenoid is first energized, releasing the brake, and the drive motor is started inro tation in the appropriate direction; then a servomotor 21, Fig. 4, is energized, thereby driving gears 22, 19, which permit spring 15 to expand and push seat 18 and gear 19 to the left until bracket 26 on spring seat 18 operates a limit switch 34 to de-energize the servomotor. (If the gears &c. had been in this position initially, the servomotor would not have been energized). To effect an emergency stop, the emergency switch is opened, whereupon the driving motor is de-energized and the brake solenoid is de-energized. Then because spring 15 has been decompressed, the deceleration is not excessive even when the escalator is fully loaded. On the other hand, for arrest of downward movement, the spring is in the compressed condition of Fig. 4, so the deceleration is greater. In Fig. 11 a main solenoid 1130 when energized forces apart levers 1116, 1118 about pivots to release brake shoes 1114 from drum 1112, against the force of a spring 1124. If the escalator is travelling upwards when the emergency switch is opened, solenoid 1130 is immediately de-energized, permitting brake application by spring 1124; after a delay an auxiliary solenoid 1132 on the other side of the lever pivots is deenergized, whereupon springs 1160, 1162 act on the levers to increase the braking pressure. If the escalator is travelling downwards both solenoids are immediately de-energized for emergency stopping. In Fig. 6 (not shown) a main and an auxiliary solenoid are mounted between the levers on the same side of the drum.