Patent GB-666067-A (GB)
Title: Improvements in or relating to braking and jacking systems for vertical shaft rotating machines
IPC: H02K15/16
Filed: 1948-05-27
Abstract: 666,067. Hydraulic lifting jacks. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. May 27, 1948. [June 2, 1947] No. 14340/48. Class 78 (iii). [Also in Group XXXIV] In a dynamo-electric machine having a vertical-shaft rotor supported by a thrust bearing and a plurality of hydraulic jacks provided with brake shoes and operable axially to engage the rotor for braking or lifting, selectively operable liquid pressure producing and control devices are adapted to supply the jacks with liquid at two pressure ranges, i.e. a lower pressure for braking and a higher pressure for lifting the rotor from its bearings, the lower liquid pressure being produced by supplying compressed air to a closed liquid reservoir while the higher pressure is produced by a liquid pump connected between the reservoir and the jacks. Valve-controlled slow and fast connections are provided between the jacks and the reservoir, the former connection permitting the rotor to be lowered gently onto its bearing after a lifting operation. The dynamo-electric machine shown comprises a stator 1 (Fig. 1), and a rotor 2 carried on a vertical shaft 33 supported by a thrust bearing 4, 5 immersed in an oil chamber 6, and guided by bearings 8, 9. Annularly disposed hydraulic jacks fitted with brake shoes 13 are adapted to engage a brake ring 11 on the rotor 2 to brake the rotor, to raise it slightly to separate the bearing 4, 5 for lubrication before starting, -or to raise it appreciably for inspection etc. As shown in Fig. 2, the jacks BC1-8 are supplied with liquid from a reservoir 17 either by means of a liquid pump P through a check valve V-CK or by admitting air at pressure to the reservoir 16 through a conduit 19, the liquid then passing through a valve 24, 25 to the jacks. A relay circuit (not shown) is described by which the operation of the jacks is controlled by push buttons. Thus when an upper push button LS (Fig. 1) is pressed to lift the rotor slightly for lubrication, air is admitted by a magnetically controlled valve V3 to the reservoir 16, a motor M driving the pump P is started and liquid is supplied through the valves V-CK and 24, 25 to the jacks. The valve 24, 25 is biassed by a spring 27 so that at low pressures it permits passage of liquid in both directions but at high pressures it operates as a check valve permitting flow of liquid to, but not from, the jacks. A solenoid V2 is operated on depression of the upper button LS to overcome the bias of the spring 27 and cause the valve 24, 25 to operate as a check valve even at low pressures. Thus when the jacks take the load from the bearing 4, 5 and the pressure rises above that of the air-pressure source, the valve 24, 25 prevents flow of liquid from the jacks and liquid is supplied to the jacks by the pump P alone. When the rotor has been raised by the' requisite amount (about 0.3 in.) a limit switch shuts off the motor M and de-energizes the solenoid V2, the valve 24, 25 continuing to act as a check valve by reason of the high pressure in the jacks. To lower' the rotor from this position lower button LS (Fig. 1) is depressed to release the upper button, so that the valve V3 is allowed to return to exhaust position and a valve VI is opened to allow a slow flow of liquid from the jacks through a throttling connection 22R to the reservoir 16. When the jacks are lowered far enough to return the rotor onto its bearings 4, 5 the consequent fall in the pressure in the jacks permits a switch PS to open, so closing the valve V1, and the spring 27 opens the valve 24. 25 to permit a more rapid exhaust of liquid from the jacks. The valve 24, 25 is closed again by the solenoid V2 to trap liquid in the jacks when jack limit switches BL1-8 are operated near the lower limit of the stroke of the jacks. To brake the rotor an upper button BS (Fig. 1) is depressed to cause the valve V3 to admit air under pressure to the reservoir 16. The valve V3 is returned to the exhaust position by depressing a lower button BS. A control station 37 (Fig. 1) is provided on a platform 38 under the generator for controlling the lifting of the rotor for inspection etc. Before this operation can be carried out a key-controlled unlocking button KB-J must be operated. If then an upper button JH-J is depressed the same lifting operation as is obtained by pressing the button LS takes place, but the operation is not stopped by any limit switch until the rotor has been raised through about 0.7 in. or, if this switch fails, by a further limit switch at 0.8 in. The operation may be stopped before this by depressing a lower button JB-J which releases the upper button. To lower the rotor from this position an upper button RB-J is operated (or the switch KB-J released) to cause a lowering operation similar to that provided by the lower button LS. The lowering may be stopped at any time by depressing a lower button RB-J to release the upper button. Governor controlled switches in the relay circuit set maximum speeds at which some of the operations described may be initiated and coloured lights on a panel 35<SP>1</SP> (Fig. 1) indicate the condition of the apparatus. A manually controlled valve V4 (Figs. 1 and 2) controls the braking action should the automatic control fail. The operation of the jacks may be interlocked with the operation of the machine so that the latter cannot be started until the rotor has been raised to lubricate the bearing : a light extinguished by a time-delay circuit may be lit when the rotor is so raised and the time delay circuit may prevent the machine from being started more than a predetermined time after a lubricating operation. The several pushbutton controlled operations are interlocked by the controlling relay circuits so that only one can be operated at a time. A further interlock may prevent the machine from being started with the jacks extended.