Patent GB-805351-A (GB)
Title: Improvements in and relating to electrical control means for winders, hoists and the like
Inventor: WOODLIFF GEOFFREY EDMUND
IPC: B66B1/30
Filed: 1954-06-11
Abstract: 805,351. Control of D.C. motors; controllers; snap-action switches. BRITISH THOMSONHOUSTON CO. Ltd. May 31, 1955 [June 11, 1954], No. 17269/54. Classes 38 (3) and 38 (5). Control gear for a winder, hoist or the like, comprises a winding 1 which is connected to tappings in a potentiometer 2 supplied from a source of constant voltage. The winding 1 may be the field winding of a Ward-Leonard generator or of an exciter for such generator, the hoist motor then being connected in the Ward-Leonard system. During the major part of the travel of the cage, the driver's lever is effective to obtain the desired speed of the wind, the voltage applied to conductor 20 corresponding with the position of brush 19 which is coupled to the control lever. Assuming that the driver's lever is left in the maximum speed position with the brush 19 in contact with member 6, however, and that the cage is approaching a stopping-position, a two-way switch 13 is operated to disconnect the contact 6 from point a on the potentiometer and to connect it to the point b. The voltage applied to the winding 1 is thereby reduced, and further movement of the cage effects sequential operation of the switches 14-18 to decelerate the motor as it approaches the stopping- position. If, during the automatic retardation operation, the driver's lever is returned towards the " off " position so that the brush 19 engages a contact producing a speed lower than that permitted by the two-way switches, then the winder speed is reduced to the value determined by the driver's lever. The switches 13-18 may be actuated in turn by cams carried by a shaft operated by a depth indicator, and each switch remains in the position to which it is operated until the cage passes the corresponding point in the reverse direction. As shown, a shaft 29, the angular position of which is related to that of the cage, carries spaced operating arms 30-35 which cooperate with a similar number of two-way switches spaced apart in positions respectively in alignment with the arms and mounted on frame bars 36, 37, parallel with the shaft 29. As the cage enters the retarding zone, tip 57 enters notch 56 so that disc 50 moves clockwise and plunger 53 is shifted over-centre to actuate rocker arm 40 of the switch 13. Contact 43 disengages contacts 46, 47, to disconnect the member 6 from the tapping-point a, and con. tact 42 engages contacts 44, 46, so that the member 6 is now connected to the tapping- point b. The arm 40 is held in contact with a stop-pin 49 by means of spring 55. The other two-way switches are actuated in a similar manner and are returned to the position shown when the cage moves in the opposite direction. The potentiometer 2 may be replaced by other arrangements involving a plurality of voltage sources of different values. The winding 1 may be connected in series with a tachometer generator producing a voltage dependent on the speed of the winder so that the speed is proportional to the voltage derived from the potentiometer 2. The winder may be driven by an A.C. motor or steam engine, the winding 1 operating a suitable control device.