Patent GB-175793-A (GB)
Title: Improvements in or relating to electric hoists, lifts, inclined railways and the like
IPC: B66B1/48
Filed: 1920-12-02
Abstract: 175,793. Waygood-Otis, Ltd., (Otis Elevator Co.). Dec. 2, 1920. Electric plant; electric push -button systems.- In an electric lift, hoist. &c., the power supply is automatically interrupted at such a point before the landing position that with an average load the cage comes tu a stop level with the landing; when the load is such that the cage does not come to a level stop, a levelling device is automatically brought into action under the control of which the cage moves up or down as required until it is level with the landing. In the case ,shown, of a lift operated by a single motor which is controlled by a switch 7 in the cage. to move (say) from the first floor to the third, the switch is moved to the left. This closes a circuit from phase III to phase II through coil 16 of an auxiliary switch E and coil 18 of the up reversing switch C. The latter switch closes the circuits for the up motion and the cage starts. At the same time auxiliary contacts 22 on the switch C close a circuit for a magnet coil A which closes contacts 2, 2<1> and moves a roller 4 on the cage out of the range of cams 1 in the lift shaft. The contacts 2, 2<1> close a self-holding circuit for the coil of switch C and also a circuit for the coil of a levelling switch L. After the cage has passed the second floor the cage switch 7 is centred, the only immediate effect being the de-energizing of the magnet A, and the consequent moving outwards of the roller 4. As the cage approaches the third floor. the roller runs on the cam 1<1> and separates the contacts 2, 2<1>, opening the selfholding circuit and the coil circuit of switch L. All the switches return to their normal positions, causing the power supply to be interrupted and the brake 0 to be applied. The cams 1, 1<1> are so arranged with respect to each floor that with the most frequently-occurring load the cage comes to a level stop. If the cage underruns the landing roller 40 runs on a cam 42 and closes contacts 46. The contacts 46 close a circuit through the coil of a switch G which closes contacts 62 and completes a circuit for switch C. so that the motor is again started and moves the cage until the roller 40 runs off its cam 42. If the cage now overruns the landing, a roller 41 runs on a cam 43 and closes the circuit for the coil of a switch F which closes contacts 66 for the coil of the down reversing switch B, so that the motor is started in the reverse direction and moves the cage back to the landing. A series of oscillations may thus take place until the cage comes to a level stop. In a modification, in which a motor having two speeds is employed, the contacts 2, 2<1> are double so that when approaching a landing the low speed only is employed. In a further modification having a push-button system and two motors, the cage-switch 7 is replaced by push-button on the cage and landings, and a floor controller and floor magnets replace the roller 4 and cams 1. The levelling switch L in this case acts in conjunction with the rollers 40, 41 to control switches for the auxiliary motor. Specifications 107,356 and 108,274 are referred to.