The switches of overspeed in order to lift and method of embodiment of a procedure of the control of overspeed

摘要

Speed detector (12), of e.g. centrifugal bob-weight type, is arranged to open primary switch contacts (14, 16) if lift speed exceeds e.g. 110% of nominal value. Set of contacts (16) is in series safety circuit sequentially connecting several contact pairs associated with different functions whose failure critically affects car safety, and controls main power supply and brake. Other (14) through relay (22) causes easily accessible secondary switch (18, 20) to open; this includes further contacts (18) in series safety circuit. After delay, to ensure switch is opened, detector unit (12) is automatically reset by local timer (24). Contacts may be duplicated at both locations to enhance security through redundancy. Secondary switch is located at conveniently accessible position, e.g. on landing, and can only be reset manually, by qualified person, for returning system to normal. An Independent claim is also included for the method of checking overspeed of lift system.