GB802867A - Improvements in and relating to electric protective gear for mine hoists and the like - Google Patents

Abstract

802,867. Mine - hoist protective gear. BRITISH THOMSON-HOUSTON CO., Ltd. May 27, 1955 [June 16, 1954], No. 17723/54. Class 78 (5). [Also in Group XXXVII] As shown, a two-cage mine hoist is driven by an induction motor M having forward and reverse contactors F, R, with operating coils OCF, OCR, and a rotor rheostat C controlled by driver's lever DL through a servo device SM. Movement of the driver's lever in any forward position causes contact FA to engage contacts 7, 8, in series with coil OCF, a contact RA similarly closing contacts 7, 9, in circuit with coil OCR during reversal. The circuits of coils OCR, OCF, are completed through contacts S1, S2, of safety relays OCS1, OCS2, and a releasing solenoid BS for an emergency brake is controlled by contacts S1B, S1C, and S2B, S2C, of these relays. When one of the cages approaches within a predetermined distance of the bank at the bottom of the shaft, either a switch DI1 or a switch DI2 will be open according to the direction of the wind. Contacts LC1 shunt switches DI1, DI2, and are closed in the " off " position of the controller and during a range of movement in either direction, such range corresponding to an increase of torque to a predetermined value. The safety relays have holding contacts S1H, S2H, shunted by contacts MC1, closed in the " off " position of the controller, and contacts Bl, closed when the brake is applied. The safety circuit is thus automatically re-set when the controller is returned to the zero position and the brake applied. When either of the depth switches DI1 or DI2 are opened, the safety circuit is maintained by the contacts LC1 provided that the control lever is not moved to a position applying to the winder a torque greater than the predetermined value. Interruption of the safety circuit de-energizes the motor and applies the brake so that the speed at which a cage approaches the stop at the bottom of the shaft is limited. After one of the cages has reached the bottom of the shaft movement of the cage in the opposte direction is not prevented, since, although in the case of a forward wind the switch DI1 will have been opened, for example, when the lever DL is moved in the reverse direction, the contacts C2 will shunt the contacts DI1. The contacts C1 operate similarly with respect to the switch DI2. A switch OS may be closed when the hoist is not being used for carrying personnel. The hoist may be driven by other types of motors, electric or non- electric.