Patent GB-532533-A (GB)
Title: Improvements in or relating to control devices for steam locomotives
IPC: B61C17/12
Filed: 1939-07-24
Abstract: 532,533. Fluid-pressure servomotors; valves. SCHNEIDER & CIE. July 24, 1939, No. 21481. Convention date, Nov. 19, 1938. [Class 135] [Also in Group XXVI] The control devices of several turbines driving independent axles of a locomotive are operated by oil pressure. To bring the turbines into action, an independent pump 2, Fig. 1, is started which supplies oil to the high-pressure oil line 1, later this pump is stopped and the oil is supplied by pumps 4 on the turbine shafts. Oil from the line 1 energizes an injector 5 which supplies oil from the well 3 to the lubricating oil line 6. It also energizes an injector 11 which transfers oil from the turbine sump back to the well 3. The line 14 supplies oil to the control devices and receives oil at a constant pressure from the line 1 through a pressure-reducing valve 13. The controls are effected by varying the oil pressure and this is done by the combination of fixed throttling devices and controlled leakage. An emergency control device 9 receives oil direct from separate pumps 8 on the turbine shaft. The main steam valve comprises a main valve 38, Fig. 2, and a pilot valve 34, operated in turn by means of a piston 48. On starting the pump 2, the oil pressure in the line 14 rises and presses a piston 53 towards the left. This cuts the connection via 60, 61 to the waste pipe 62 and admits oil from the pipe 14 to the cylinder 47. The pressure on the piston 48 is sufficient to open the pilot valve 34 but not the valve 38 so long as it is unbalanced. In the warming up period, the turbine valves are fully open and steam passes through holes 37 in the valve 38 and through the valve 34 but does not materially increase the pressure below the valve. Afterwards, the turbine valves are closed and the steam pressure under the valve 38 rises until the oil pressure under the piston 48 is able to open the valve 38. When the pressure in the pipe 14 fails the piston 53 moves back to the right, the cylinder 47 is connected to the waste pipe 62 and the piston 48 falls. The final movement of the piston is damped. The piston 48 and cylinder cover 52 are shaped to produce a dash-pot effect as. the piston returns to its lowest position. The load on a leakage valve 71 produced by a spring 73 increases as the spindle 41 rises and the consequent variation of the oil pressure in the pipe 76 is used as a gauge at the control station to indicate the position of the valves 34, 38. When the pipe 59 is opened by the safety regulator, the oil pressure fails and the steam valves shut. The sequence valves 123, 124, 125, Fig. 9, of each turbine for forward running and the valve 132 for reverse running are operated by servomotors of the kind described in Specification 532,390, which respond to variations in the oil pressure obtaining in the pipe 119 and those variations are produced by the devices shown in Fig. 3. For forward running, the hand-wheel 27, Fig. 1, is turned and a cam depresses the spindle 97 to open a valve 102 fully. This admits pressure oil from the pipe 101, which is connected to the line 14, to a chamber 109 and thence through a choke 117 to a valve 111. The valve 111 is pressed on to its seat by a spring 113 which' is increasingly compressed as a spindle 96, in the continued rotation of the hand-wheel 27, is depressed by a snail cam. The leakage of oil past the valve 111 diminishes as this pressure increases and the operating pressure in the pipe 119 correspondingly increases. The opposite rotation of the hand-wheel from its initial position similarly affects the oil pressure in the pipe 120 by which the reversing valve 132 is controlled. The lower portion 130 of the reversing valve is resiliently secured to the remainder by means of a disc 131 clamped at the centre to the body 132 and secured at the rim to the portion 130. The emergency control comprises a number of piston valves 185, Fig. 16, one for each turbine, any one of which can connect the pressure oil supply 59 of the main steam valve to the waste pipe 189. The valves are subjected as pistons to the oil pressures generated in centrifugal pumps 180 on the turbine shafts. Each piston has a choke passage 187 and the oil, passing through, returns by a pipe 190 to the pipe 181 feeding the centrifugal pumps. A turbine which exceeds a safe speed produces an oil pressure sufficient to raise it associated piston valve and thereby connect the pipes 59, 189. The pipe 59 may also be connected to a waste pipe 199 by an overriding hand-operated control 26, Figs. 1 and 16, which includes a valve 193. A pin 195 rides in a slot in the valve and when the valve is drawn to the left and rotated the pin 195 prevents the return of the valve.