Patent GB-878880-A (GB)
Title: Improvements in or relating to electrical control apparatus for moving bodies
IPC: B66B1/26
Filed: 1959-02-09
Abstract: 878,880. Automatic speed control systems. WESTINGHOUSE ELECTRIC CORPORATION. Feb. 9, 1959 [Feb. 13, 1958], No. 4437/59. Class 38 (4). [Also in Group XXXVII] A lift-motor 1 is supplied from a Ward- Leonard generator G having its field windings GF1, GF2 connected in a bridge circuit with resistors GR1, GR2. The speed of the motor is determined by means of a control lever 215 pivoted at point 217, and a force representing the desired speed of the motor 1 is provided by a motor PM comprising a stator winding 227 and a movable cup 229 carrying windings PM1, PM2. The force due to the motor PM is opposed by one dependent upon the speed of the liftmotor and provided by a motor-driven conductive disc 231 co-operating with a magnet 237. Deflection of the lever 215 controls the excitation of the generator G through rheostats 239, 241, which are actuated by pusher arms 243, 245. Resistor 239R is connected in series with the primary winding of a transformer 247 whose secondary output is rectified at rectifier 253 for energizing the field windings GF1, GF2, with the proper polarity for down-travel of the liftcar. Similarly, resistor 241R and the primary winding of a transformer 255 are connected in series, the output of this transformer being rectified by rectifier 256 providing upward travel of the car. The winding PM2 is linked with an anti-hunting winding 257. When the car is started in an upward direction, an armature UMA is displaced from coil UMC so that the impedance of unit UM is at a minimum, and, consequently, substantial current is supplied to the winding PM 1 for accelerating the lift until the desired speed is reached. When the car approaches a floor at which it is to stop, the armature UMA moves towards the coil UMC to increase the impedance of the coil and to decelerate the lift. As the car further approaches the floor, the unit UM is rendered ineffective and a unit EU becomes operative for registering the car with the floor. When the unit EU is midway between the ends of a plate P, the output of rectifiers 267, 271, is such that the resultant voltage across resistor 273 is zero. If the unit EU is displaced from this position a voltage is developed across resistor 273 and is applied to winding PM1 whereby the excitation of the generator G is in a proper direction to move the car level with the floor. Since the unit EU is mounted on the car whilst the plate P is mounted in the hoistway, accurate levelling is obtained. An auxiliary brake relay BR maintains the brake released as long as the winding PM1 is energized. A unit DM, similar to the unit UM, is effective during downward operation of the car. The disc 231 and the magnet 237 may be replaced by the driving and driven portions of a fluid coupling. For establishing the magnetic field in the disc 231, either two or four permanent magnets may be employed, or electromagnets may be used. The disc 231 may be replaced by a hollow cylinder which is driven directly from the lift motor. The control lever then carries a C-shaped permanent magnet having pole faces shaped to define an air gap within which a portion of the cylinder is located. The armature UMA may be mounted on a member forming part of a floor selector and moving in synchronism with the car, whilst the coil UMC is mounted on another member which is coupled to the first but allowed to move relatively thereto. Specification 527,839 is referred to.