Patent GB-743804-A (GB)
Title: Improvements relating to the braking of mine winders, hoists and the like
Inventor: EVANS OWEN THOMAS
IPC: B66D5/26
Filed: 1953-06-16
Abstract: 743,804. Winding mechanism. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. May 26, 1954 [June 16, 1953], No. 16595/53. Class 103 (1). In a braking system for mine winders, hoists and like equipment of the kind incorporating a fluid-operated braking engine coupled to the brake through a suitable linkage and arranged to operate the brake in at least one directioneither to apply or to release the brake by appropriate application of pressure fluid to the engine, operation of the brake in the other direction being effected either by appropriate application of pressure fluid to the engine to cause such reverse operation or by virtue of a spring or other bias against which the engine acts when operating the brake in the firstmentioned direction, a " slugging " valve, which limits the speed at which the brake can be applied, for the braking engine is coupled to the main brake linkage through a secondary linkage whereby the degree of movement transmitted through the secondary linkage and thus the extent of the " slugging effect produced by the valve on the brake may be varied. In the general arrangement illustrated, the brake is applied by a spring or other bias 5 which actuates main linkage constituted by a main lever 2 fulcrumed at 3 to actuate the brake shoes through two connecting rods 4a and 4b. The brake is released by movement of the axially movable link rod 1 in the direction of the arrow, against the action of the spring 5, which actuates the piston of a single acting hydraulic braking engine (not shown) and subsequent re-application of the brake is effected by opening the braking engine cylinder to exhaust, this arrangement providing the advantage that should the hydraulic system fail, the brake will be applied. In order to limit the speed of application of the brake so as to prevent the brake being applied too fiercely, a " slugging " valve 7 is coupled with the main linkage, through a secondary linkage described below, for progressively restricting the exhaust pipe as the brake is moved towards its fully applied position. In operation, when the winding cage is in a position in the shaft other than in the region of the top or bottom of the shaft, a follower roller 33, a cam 34 and an intermediate lever and auxiliary link rod 32 and 31 respectively govern the actuation of an intermediate link rod 18 to keep its end provided with a transverse pin 26 to the right hand end of an arcuate slot 27 in an intermediate lever 19, which is provided at its other end with a counterbalance weight 24, and fulcrumed at 20. At the remote end of the intermediate lever 19, a transverse pin 21 slides with " lost motion " in an elongated slot 22 provided at one end of a link rod 23 which is pivoted at its other end to the main braking lever 2 as shown in the Figure and as described in Specification 743,805. Thus, in the position of the transverse pin 26 in the arcuate slot 27 in the " off " position of the brake illustrated, when the brake is applied by opening the braking engine cylinder to exhaust, the intermediate lever 19 swings in a clockwise direction to actuate the secondary linkage and operate the " slugging " valve 9 to limit the speed of application of the brake. However, in order to have full effective braking when the cage is approaching the top or bottom of the shaft, cam 34 is provided with two protuberances which correspond to these positions so that on approaching these positions the follower roller 33 actuates the lever 32 and link rod 31 to actuate the intermediate link rod 18 and swing the transverse pin 26 to the left-hand end of the slot 27 so that the axis of the pin is coincident with the fulcrum axis of the intermediate lever 19 and thereby no action is transmitted to the " slugging " valve 7 so that instantaneous braking is available at the top and bottom of the shaft.