Patent GB-707244-A (GB)
Title: Improvements relating to the control of electrically operated mine hoists and the like
Inventor: GREAVES REGINALD DOUGLAS
IPC: B66B1/12
Filed: 1951-05-10
Abstract: 707,244. Mine hoists. METROPOLITANVICKERS ELECTRICAL CO., Ltd. April 29, 1952 [May 10, 1951], No. 11048/51. Class 78 (5) [Also in Group XXXVII] A manual/automatic control system for electrically driven hoists and the like has a speed controller 2, which may be of the Ward-Leonard type, adjusted during manual operation by the movement of a control lever 1 in either direction from a central position according to the required direction of the wind, and during automatic operation by the action on cam-followers 8, 9 of cams 10, 11, which are driven by the winding drum. An auxiliary lever 4 is adjustable to three positions representing manual, semi-automatic, and fully-automatic operation of the hoist, and, when this lever is in a position for automatic control a cam-follower is biased into contact with its cam and the manual control lever 1 is disabled. Movement of the lever 4 to the position for manual control disengages the camfollowers from the cams, the manual control lever being solidly coupled with the speed controller and relieved of the biasing force. The force for applying the cam-followers to the cams is controlled by weighted rocking levers 14, 15 loosely mounted on a shaft 16 but normally engaging stops 19, 20, on the shaft so that the arrangement is in. equilibrium. If either one of the rocking levers is lifted, the other lever will tend to descend so applying a turning-moment to the shaft which acts through mechanical linkage to bias a cam-follower against its respective cam and to actuate the speed controller. Solenoids 31, 32, are provided for lifting the respective levers and are energised in accordance with the required direction of wind. For manual operation, both levers are lifted away from engagement with the shaft so that no turning moment is applied to the shaft, the solenoid plungers being supported in their raised position by member 40. The movement of the lever 1 is transmitted to the controller 2 through a mechanical linkage including a pivoted lever 46, the arrangement being such that, when the lever 4 is in the manual position, the pivot of the lever 46 is locked. When the lever 4 is in the fullyautomatic or semi-automatic position, however, the pivot is left floating so that the movement of the control gear under the influence of the camfollowers is not transmitted back to the manual control lever which, during automatic operation, is placed in the full speed forward position and maintained therein. The auxiliary lever 4 actuates an auxiliary change-over switch 7 for controlling the solenoids 31, 32, and also operates a main change-over 6 which modifies the control circuit for semi-automatic operation, transfer ring the reversing control from the master controller 3 to a starting contactor. Transmission from semi-automatic to fully-automatic operation by the lever 4 is permitted by spring-link 58, the switch 6 being further adjusted to make additional modifications of the control circuits. The cams 10, 11 provide initial acceleration and final deceleration control in either direction, and means may be provided by virtue of which the cams are rotated only during the periods of changing speed and remain stationary through the full-speed portion of the wind. The cam drum is prevented from rotating by means of bias weights during full-speed operation, and as the winding proceeds, a flange fixed to a driving shaft is moved by means of a square thread until the engagement of two lugs causes the cam drum to turn through an appropriate angle until the terminal point of the wind is reached, Fig. 4 (not shown). Two sets of cam followers may be mounted on a crankshaft which is lockable in three positions respectively oorresponding to ore-winding operation, man-winding operation, and disengagement of the sets of camfollowers. Specifications 707,245 and 707,246 are referred to.