GB236904A - Improvements in safety brakes for lifts and elevators - Google Patents

Abstract

236,904. Waygood-Otis, Ltd., (Assignees of Lindquist, D. L.). July 11, 1924, [Convention date]. Safety retaining-mechanism.-In safety apparatus of the kind in which jaw members are actuated by a governor to grip a stationary guide rail when the speed becomes excessive, each jaw member is mounted upon parallel rocking links arranged substantially at right-angles to the rail and spring supported from an abutment provided with means for adjusting the spring pressure. The brake comprises a pair of rollers 54 mounted on longitudinally movable rods 67, and jaw members 52, 53 which are supported by pivots links 62. Springs 63, 70 urge the members 52, 52 and rods 67 downwards. The rods 67 rest on cams 72 mounted on shafts 23 which are geared together and one of which is geared to a shaft 27. One end of a rope 32 is attached to an arm 31 on the shaft 27 and the other end is attached to a hitch 34 on an endless rope 35 which is held normally in a releasing carrier 51 on the cage. The rope 35 passes over a sheave 36 driving a centrifugal governor and between pivoted jaws 41, 42. An arm 44 on the jaw 41 is engaged by a spring- pressed catch 46 and connected by a link 45 to the governor. When the governor reaches the speed for which it is set to act, the arm 44 is released and raised, and the jaws 41, 42 close on the rope 35 and arrest its movement. As the cage continues to descend the hitch 34 is withdrawn from the carrier 51 and the shaft 27 is rotated. When the shaft 27 has turned through an angle of 90‹, the rollers 54 have been raised into contact with the inclined surfaces 77 of the members 52, 53 and the guide rail 16. The rollers move upwards until arrested by the stops 78, as shown in Fig. 4, and during their movement the members 52, 53 are moved upwards and outwards against the springs 63. The stops 78 act as brake shoes for the rollers 54 which roll on the rail 16. The brake pressure is varied by adjusting the springs 63. If the retarding force increases on account of the condition of the guide &c., the members 52, 53 move away from the guide and decrease the pressure on the rollers until it reaches the value for which the springs have been set. The mechanism is reset by releasing the jaws 41, 42 by hand, engaging the catch 46, and replacing the hitch 34 in the carrier 51. If the cage is then raised. the rollers 54 are returned to their lowest position, Fig. 3. In the operation of the brake, when the shaft 27 has turned through an angle of 90‹, the rope 32 draws the rope 35 through the jaws 41, 42 as the latter jaw can move horizontally against the resistance of the spring 50. The guide is reduced in thickness at such a position that the brakes are released at the time, or shortly before, the cage comes into contact with the buffers 21 at the bottom of the shaft. The braking device may be mounted on the counterweight 13 instead of on the cage. Specification 240,474 is referred to.