Patent GB-1476298-A (GB)
Title: Brake apparatus
IPC: B66D5/26
Filed: 1974-09-20
Abstract: 1476298 Winch drum brakes BLACKS EQUIPMENT Ltd 20 Sept 1974 [4 Oct 1973] 46425/73 Heading B8B [Also in Division F2] A brake apparatus of a mine hoist comprises a winding drum 10 whose opposite ends are formed as braking surfaces 11, 12, each surface 11, 12 having a respective pair of brake shoes 13A, 14A and 13B, 14B associated therewith, and each pair of brake shoes having two respective spring rests 26A, 26B and 26C, 26D which act independently to bias the shoes 13A, 14A or 13B, 14B into braking engagement with the surfaces 11 or 12 but whose bias is relieved by a hydraulic system including four cylinders 28A, 28B, 28C, 28D having respective pistons 27A, 27B, 27C, 27D acting on the respective spring devices. The system also includes relief valve means (i.e. a single relief valve or as shown two relief valves 41A, 41B) for maintaining a residual fluid pressure in the system when all four shoes are applied partially to effect the force of the devices 26A-26D, and by-pass valves 62A, 62B arranged to by-pass the relief valve means 41A, 41B in the event of a mechanical failure associated with one of the spring rests to exhaust the cylinders 28A-28D to allow increased braking force to be applied by the other three spring rests. As seen in Figs. 1, 2 each pair of brake shoes 13A, 14A and 13B, 14B has two tie rods 21A, 21B and 21C, 21D and two bell crank levers 22A, 22B and 22C, 22D interconnecting the shoes. Four separate abutments 23A, 23B, 23C, 23D are provided for the respective spring rests. The hydraulic system shown in Fig. 5 has a major pump 35 and a minor pump 36 with a valve 37 which changes from pump 35 to pump 36 after the brake take-off pressure has been achieved. The valves 41A, 41B have their inlet ports connected to a pressure line 34 via non-return valves 41D, 41E and their outlet ports are connected to a line 53. The valves 41A, 41B are in a hydraulic circuit including pressure switches 45A, 45B which operate electrical contacts 46A, 46B in a circuit containing warning lights 47A, 47B, which indicate that the respective valve 41A, 41B is opening correctly. The system also includes two fail-safe trip valves 50A, 50B normally held closed by electro - magnets 51A, 51B through levers 55A, 55B but if these are de-energized due to overspeed or overwind, the valves are opened by springs 52A, 62B to exhaust pressure from cylinders 28A, 28D via line 53. The valve members 56A, 56B of these valves connected to a lever 58 connected to a contact member 59 associated with an electrical circuit 60 connected with a warning light and/or safety circuit. Each by-pass valve 62A, 62B has one port connected to the pressure line 34 and one port connected to an exhaust line 42. The spools of valves 62A, 62B have actuating rods 63A, 63B carrying abutments 64A, 64B which are engageable by abutments 23A, 23B and 23C, 23D in the event of a tie rod failure associated with one spring rest to open valve 62A or 62B. Braking is normally effected by operation of a driver's valve 41 which exhausts pressure from cylinders 28A-28D down to a selected residual pressure determined by relief valves 41A, 41B ; this also occurs if either of the valves 50A, 50B is tripped. If a tie-rod breakage now occurs when any of the valves 41, 50A, 50B is actuated, the abutment 23A-23D associated with the broken tie rod will operate valve 62A, or 62B to exhaust cylinders 28A-28D completely. To check the operation of valves 62A, 62B a bar can be inserted between abutments 64A, 64B and 23A-23D. If desired another exhaust line 65 can be provided with a non-return valve 66 to enable valves 41A, 41B to be by-passed to apply a full braking force.