Patent GB-1183400-A (GB)
Title: Mine Hoist Control System
IPC: B66B1/24
Filed: 1967-10-06
Abstract: 1,183,400. Lift control systems. NORDBERG MFG. CO. 6 Oct., 1967 [3 Feb., 1967], No. 45868/67. Heading B8L. [Also in Divisions F2, G3 and H2] A mine hoist comprises skips positioned respectively in a pair of mine shafts associated with hoist drums 31, 33 driven by an induction motor 37 having a wound rotor and controlled by drum switch 41. Each drum has brake shoes 45 biased into engagement therewith by weight 47 on lever 49. A brake cylinder 55 is supplied by pump 61 through valve 63 which is linked with a manual control lever 69 and is also coupled with the lever 49. Each brake shoe has a compression spring 73, and a weight-loaded hydraulic accumulator 74 replaces the pump 61 if the latter fails. The skips are designed to transfer material from three loading-levels ,to storage bins at the top of the shafts. Two proximity switches are provided near each loading level, one switch being at and the other above the level at a point where a loaded skip is free to be accelerated or an empty skip is slowed to a creep speed. The proximity switches are actuated by magnets mounted on the skips, the upper switches being direction-sensitive. The brake-valve 63 is controlled by actuator 101, the operating rod 105 being coupled to pistons in hydraulic cylinders 115, 117, the former acting as a telescoping link when unpressurized to permit manual operation by the lever 69. De-energization of solenoid-operated valve 119 bleeds the fluid from cylinder 115 to disengage the actuator 101, whilst de-energization of the solenoid 121 reverses the flow of fluid to the cylinder 117 whose piston takes up the clearance between the brakes and the hoist drums. The actuator 101 is controlled by governor 125 which compares a D.C. signal, representing the speed of the motor, derived from magnetic pick-up 173 monitoring a pulse gear 131, with a ramp voltage indicating a desired speed for a skip at a particular location in the shaft. Skipposition sensing units 104 each comprise a motor-driven carriage for a micro-switch cooperating with rotatable arms for initiating deceleration of the hoist when a skip is a predetermined distance above a loading-level. A programme panel 103 is used to control the starting acceleration, deceleration, and stopping operations of the motor. The actuation of a push-button which places the hoist under automatic control causes the panel 103 to reset to its home position and transfers control from the drum switch 41. A level selector switch, forming part of controller 102 may be turned to a third level and a pushbutton operated for moving the skips. The motor is energized and, when its current reaches a sufficient value, the brake is released to allow operation at creep speed until a proximity switch 97 is actuated by passage of the skip. The programme panel is stepped on until the motor runs at full speed and the brake is fully released. When the third loading level is approached the accelerating relays are de-energized by unit 104, the governor 125 is disconnected, and the actuator 101 causes deceleration of the skips at a linear rate to a creep speed. Proximity switches 85, 87, further decelerate the motor and finally stops it with one skip at the third loading level and the other at the loading hopper. A time relay then returns the programme panel to its home position, ready for a new cycle of operations. When the first or second loading levels are selected rather than the third, the programme panel skips a number of steps and the slow-down operation by the unit 104 is modified accordingly. Should either of the loading hoppers become full, the cycle in progress may be completed but a subsequent cycle cannot be initiated. Inching operation is controlled by a timing relay. An over-speed detector 175 is connected to an emergency stop relay which is also associated with emergency stop-buttons at the various loading-levels. A test switch allows the automatic cycle to be followed with the aid of indicator lights.