Patent GB-800407-A (GB)
Title: Improvements in or relating to control systems for electric motors
Inventor: FRIEDLANDER ERICH SIEGFRIED
IPC: B66B1/12
Filed: 1955-06-10
Abstract: 800,407. Control of motors; controllers. GENERAL ELECTRIC CO., Ltd. June 6, 1956 [June 10, 1955; Aug. 3, 1955; Dec. 2, 1955], Nos. 16798/55. 22302/55 and 34622/55. Class 38 (3). When an electrically-driven winder cage is moved upwardly between two stopping-points, the winder motor first accelerates to maximum speed and then operates at constant speed until the cage reaches a point which is a predetermined distance from the upper stopping-point. The cage then decelerates to creep speed and remains at that speed until a mechanical brake is applied. When the cage is travelling at maximum speed, silvered contact surfaces 1, 2 on a stationary drum 10 are engaged by a motordriven contact 8 whereby the full voltage across potentiometer 5 is applied to a motor control circuit through terminals V, S. As soon as contact surfaces 2, 3 are engaged by contact 9, and the surfaces 1, 2 no longer bridged by contact 8, deceleration of the winder motor is prepared for since the voltage signal is derived from the negative end of the potentiometer 5 and a motor-driven contact 6 rotating over segments 7. When the contact 8 leaves surface 1 and contact 9 engages surface 3, contact 6, which is driven at a higher speed than the contacts 8 and 9, is positioned to provide a maximum voltage signal. Rotation of the contact 6 over the segments 7 decelerates the motor to creep speed. After the winder motor reaches a stopping-point and a change of direction is indicated, a torque motor 23 rotates the contact 6 over the potentiometer segments away from the creep-speed portion of the potentiometer 5. Thus, a pattern of acceleration different from the pattern of deceleration is provided. A link 19 allows rotation of shaft 17 relative to the driving-shaft 20 of the winder motor. Switch contacts 26, 27 are positioned as shown for manual control with automatic supervision, a hand lever 28 being provided which actuates a movable contact 29 of a pattern speed potentiometer 30 in parallel with potentiometer 5. A balance relay 31 gives preference to that potentiometer contact 6 or 29 which demands the lower of two speeds, the relay having opposed coils 32, 33, each connected between the negative pole of the potentiometers and the respective moving contacts thereof. Thus, if the manual controller is adjusted to a position corresponding to a speed in excess of a predetermined value for the position of the load, coil 33 preponderates and contact 35 engages contact 34 for switching over to the automatic control circuit. In a modification, a polarized relay is adapted to energize a pilot motor and to engage a clutch for coupling the pilot motor to the manual controller when the speed of the winder motor exceeds the predetermined value. In this manner, the manual controller is actuated by the pilot motor to adjust the speed of the winder motor to the predetermined value. In this arrangement, the pattern speed signal is always derived from the potentiometer associated with the manual controller, Fig. 2 (not shown). A load weighing device controls the position of a movable contact 50 on a resistor 51 in parallel with a section of the potentiometer 5. The initiation of deceleration of the winder motor is thus made to be dependent upon the load. The automatic control system may be adapted to multiple-level push-button control. As many sets of potentiometer segments are provided, and as many fast rotating contacts (equivalent to contact 6), as there are different levels at which the winder is adapted to be stopped for each direction of wind. A pair of slow rotating contacts (equivalent to contacts 8, 9) are retained. Contact surfaces 1 and 3 are sub-divided whilst surface 2 remains as before. The fast rotating contacts have their shafts clutched for correct positioning and switches are provided for rendering the appropriate sets of potentiometer segments effective at the correct times, Fig. 3 (not shown). In order to provide a, fine deceleration or acceleration control operation at the low speed end of the deceleration or acceleration periods, a second potentiometer is provided having its contact driven by the winder motor at a speed higher than that of the first potentiometer 5. Although the second contact is continuously moved over its associated segments during movement of the load, the voltage signal is derived from the second potentiometer only when the first potentiometer contact is on a predetermined number of its segments during acceleration or deceleration of the winder motor. Thus, one voltage step on the first potentiometer is divided into many steps by means of the additional potentiometer, thus providing fine control. Specification 785,478 is referred to.