Patent GB-208993-A (GB)
Title: Improvements in levelling means for lifts and the like
IPC: B66B1/42
Filed: 1923-07-17
Abstract: 208,993. Waygood-Otis, Ltd., (Otis Elevator Co.). July 17, 1923. Electric plant. - A levelling switch for electrically-driven lifts is operated by cams upon two coaxial rotary members carrying rampengaging arms for engaging fixed ramps in the lift shaft, the rotation of the rotary members putting the arms into register with the ramps when the power is cut off, the operation of the rotary members by the ramps then manipulating two switches in succession, one to reduce the speed and the other to effect a final stoppage at the landing. Figs. 1, 2, 7, and 8 show one construction in which an electromagnet C is used as the operating means. Four switches 3 - - 6 are mounted in line in a casing and are held open against the action of closing springs by crank arms. Crank arms 16, 17, Fig 1, controlling the switches 3, 4 are mounted on a sleeve connected to the upper ramp-engaging roller 22, while the crank arms 18, 19 are connected directly to the shaft 14 connected to the lower roller 22. In addition to these direct cam controls, the middle switches 4, 5 are crossconnected and operated by additional cams 31, 33, the tail pieces of which are controlled by the electromagnet C. During the running of the lift the electromagnet C is energized and the raising of the core 26 rotates the shaft 14 and the sleeve so that the switches 3, 6 are closed, the cams 17, 18 are moved out of engagement with the switch arms 12, but the middle switches 4, 5 are still held open through the crossconnection with each other by the levers 31, 33. The rollers 22 are thus held in a vertical position clear of the ramps. The closing of the switches 3, 6 is immaterial at this stage, since the circuits thev control are broken at other points. The cutting off of the power near a floor, for example from a descending cage, de-energizes the magnet C, and frees the tail pieces controlled thereby. At this stage the lower roller 22 is engaged by the ramp, and in consequence the tail piece attached to the shaft is now controlled by the ramp and roller, while that attached to the sleevefalls and opens the switch 3, also re-positioning the main cam 17 to open the switch 4 which is however already held open by the crossed arm 31. This rotation of the sleeve also rotates the cross arm 33 and allows switch 5 to close. The closed switches 5, 6, then establish circuits which vary the running conditions to reduce the spead. As the roller runs on to the lower incline of the ramp, the shaft 14 gets sufficient play for the main cam to open the switch 6 under the influence of the weighted tail lever, thereby breaking the circuit and causing a further reduction in speed. Finally, on leaving the ramp, the roller allows the switch 5 to be opened, thereby varying other circuits to bring the car to rest. Should the roller arm 21 by any means not be in position for engaging the ramp 23, the car will overrun the landing, but in that case the other roller on the arm 20 will contact with the ramp 24 and bring the car to rest below the landing, thus indicating to the operator that the lift is out of order. A modified arrangement is described in which the tail pieces of the switch arms are actuated by a motor instead of an electromagnet. The embodiment of the apparatus in a system of lift control also is described.