Patent GB-401255-A (GB)
Title: Improvements in or relating to diesel locomotives having pneumatic transmission systems
IPC: B61C9/22
Filed: 1932-02-02
Abstract: 401,255. Compressing air. SOC. ANON. BREVETTI ZARLATTI, 11, Via Tibullo, Rome. Feb. 2, 1932, No. 3151. Void [Abridged as open to inspection under Sect. 91 of the Acts, Feb. 3, 1932]. [Class 8 (i).] In a Diesel-engine locomotive with a compressed-air and steam transmission system in which the engine and compressor are controlled automatically in accordance with the air pressure in a reservoir situated between the compressor and the locomotive cylinders, the engine and compressor control is effected by a regulating fluid, such as oil, the pressurevariations in which are produced by pressurevariations in the working medium in the reservoir. In the construction shown a Diesel engine 1 drives a compressor 3 supplying air through a reservoir 6 and a regulating valve 8 to the cylinders 10 driving the locomotive. A reversing lever 11, similar to that of a steam locomotive is provided, and the driver controls the normal running of the locomotive by this lever only, the pressure in the reservoir 6 being maintained approximately constant and the engine output being automatically controlled. A pump 12 driven by the engine or by a separate motor circulates oil constantly from a tank 13 through a circuit 16, 17, a throttle valve 52 inserted in this circuit being controlled by a diaphragm 50 acted upon by the pressure in reservoir 6. In the example described it is arranged that when the low-pressure limit of 14 (atmospheres) exists in the reservoir 6 the oil pressure is 1 ; as the pressure in 6 rises the oil circulation is throttled by the valve 52 and the oil pressure rises accordingly at the rate of 1 atmosphere for each half atmosphere in 6, so that when the reservoir pressure is 16 the oil pressure is 5. The oil circuit is connected by a pipe 18 to a relay 23 acting on the engine governor 20. and by pipes 29 to relays 30 acting on the inlet valves 4 of the compressor. When the reservoir pressure is 14 and the oil pressure is 1 the governor relay piston 23 is at the bottom of its stroke and the governor sets the engine to its full speed, say 480 r.p.m. The automatic control may be considered to take place in the following stages. (1) If the load decreases the reservoir pressure will rise to, say, 14¢, and the oil pressure will thereby be gradually raised to 2, the piston 23 will be raised and the load on the governor varied so that the engine speed will be gradually lowered to half speed, and the total output will be halved. (2) At the oil pressure of 2 the piston 31, 32 of relay I will be raised against the action of its spring 33 and its top piston 41 will open a passage from reservoir 6 along pipes 43, 19 to a piston 46 which will be raised by the air pressure behind it and will hold the corresponding inlet valve 4 off its seat, so that one end of one compressor cylinder will be out of action. The springs 33 of the other relays are stronger and come into action only at successively higher pressures. As the double piston 31, 32 of relay I rises it admits oil from the pipe 29 through pipe 34 to a cylinder 35 containing a piston 36 which is thus forced out until a smaller piston 38 throttles the oil passage from pipe 18 to piston 23. The oil pressure behind the piston 23 is thus reduced and the piston is partially depressed by its spring 24 to an extent determined by the throttling effect of the piston 38 which may be adjusted by a screw 39. As the piston 23 descends the engine speed increases from 240 to 320, say, to avoid a sudden alteration of power output due to the putting out of action of one cylinder end. (3) A further rise of reservoir pressure to 15 and of oil pressure to 3 will cause the piston 23 to be gradually raised again until the engine speed drops to its minimum of 240 and the power output is three-eighths of the maximum. (4) At the oil pressure of 3 the relay II is actuated, a second air inlet valve 4 is half open, and the second throttling piston 36, 38 is actuated to throttle the pipe 18 still more and to cause the piston 23 to descend so that the engine speed rises somewhat to correspond to the raising of the inlet valve. (5) and (6) A further rise of reservoir pressure will first lower the engine speed again, and then, when the last relay III is actuated, and another inlet valve left open, the engine speed is again raised. A still further rise in the reservoir and oil pressures causes a final reduction in engine speed. The relay pistons 31, 32 are formed with different diameters so that after the pistons have been raised part way the oil pressure acts on the larger area and causes a final sudden movement. The engine governor 20 acts in the usual manner through a lever 54 on the fuel pump, but the relay piston 23 may act directly on the fuel pump instead of on the governor. Instead of acting on the inlet valves the compressor may be cut out in stages by other means such as lifting the delivery valves or including auxiliary clearance spaces. The rods 40 of the relay pistons 31, 32 may also act on valves controlling the admission of steam or the injection of water into the compressor cylinders, so that this action will be stopped whenever the inlet valve of that cylinder is held open. The oil pressure, instead of increasing with the air pressure, may be arranged to diminish as the air pressure increases, the valve 52 in this case opening the flow as it moves downwards instead of throttling it.