GB1042553A - Improvements in or relating to speed limiting apparatus for lifts and hoisting gears - Google Patents

Abstract

1,042,553. Overspeed-prevention devices for lifts. INVENTIO A.G. July 2, 1964 [July 30, 1963], No. 27282/64. Heading B8L. [Also in Division F2] A speed limiting device for lifts and hoists consists of a braking arrangement including a rotating carrier, e.g. in the form of a pulley wheel 2, which is connected by a cable 3 to the lift cage or a stopping device on it, at least one centrifugal body pivoted on the carrier for outward movement into contact with a stationary drum 1.3 against the force of a spring, when a predetermined speed is exceeded, and a stop limiting inward movement of the body, the body being arranged to pivot during such outward movement, whereby the spring is adapted to go over-centre and thus exert a reverse torque on the body on contact of the latter with the drum, which maintains such contact. The body preferably has a self-wrapping effect upon contact with the drum so that the carrier is locked to the drum. In the embodiment shown, four bodies 6, 7, 8 and 9 are pivoted on the carrier, two being arranged to lock the carrier in each direction of rotation. Each such pair of bodies are linked by a respective loosely mounted ring 24, 25 on a shaft 4, by which the pulley 2 is journalled in the casing 1.2 of the stationary drum 1.3, each ring being connected to the associated bodies by links 20, 21 and 22, 23 respectively. Adjustable stops 6.2, 7.2, 8.2, 9.2 engage abutments 10, 11 secured to the carrier to fix the inner positions of the bodies. Springs 12, 13, 14, 15 normally keep the bodies against the stops and their lines of action are arranged to pass through the positions of the body pivots prior to engagement of the bodies with the drum, i.e. pass " over-centre " and thus cause the carrier to be permanently locked once the predetermined speed has been exceeded. In a modification (Figs. 4 and 5, not shown), employing only two bodies 40, 41 which lock the carrier in one direction of rotation corresponding to downward movement of the lift cage, a re-setting arrangement for the bodies is provided comprising a knob 49 adapted to be manually rotated to act via a transverse pin 50 and slots in ring 46 which interconnects the bodies, so that the bodies can be brought back, after outward locking movement, into contact with abutments 42, 43 on the carrier 34. Also, in this embodiment, the pulley wheel 36 is separate from the carrier and coupled with it through a slipping clutch.