Patent GB-538168-A (GB)
Title: Improvements in control devices, especially suitable for controlling internal combustion engines
IPC: B61C17/12
Filed: 1940-01-19
Abstract: 538,168. Fluid-pressure servomotors. GANZ & CO., Ltd. Jan. 19, 1940, No. 1214. Convention date, Jan. 19, 1939. [Class 135] A fluid-pressure servomotor control system, which is especially applicable for controlling the fluid supply to internal conbustion engines on trains where multi-unit engines are simultaneously controlled by a master controller and which is of the kind in which a number of pistons act in sequence upon a control member, is constructed with an auxiliary control means which has the function of limiting or modifying the stroke of at least one of the pistons, and the fluid supply' is controlled by the selective operation of one or more pistons of the group. As shown in Figs. 1 and 2, the movement of a shaft 1, which controls the oil supply, is governed by means of four cylinders A, B, C, D screwed to a casing 13 and fitted with piston rods 3a, 3b, 3c, 3d which act in sequence upon a crankarm 2 formed with arms 4a to 4d, provided with stops 5a to 5d upon which the rods 3a to 3d act in sequence. The crank-arms are of different length and by operating the pistons of the cylinders A, B, C in sequence the shaft 1 is moved. to different positions. The fourth position is obtained by supplying compressed air to cylinder D and the extension of the piston rod 3d is controlled by the auxiliary control device 7 shown in Fig. 2. This comprises a cam 8 freely mounted on the shaft 1 and provided with arms 9a, 9b, 9c, fitted with adjustable screws which can engage the piston rods 3c, 3b, 3a, in this sequence, the cam 8 and the arms being moved counter-clockwise under the action of a roller 17 on a bell-crank lever 12 which rotates under the action of the piston 3d on a roller 18 on the bell-crank as the piston 3d is extended. The shaft 1 is thus moved to four positions the control device 7 being halted first by the rod 3c, and then in other positions due to the successive evacuation of the cylinders C, B, A in this order. This apparatus may be simplified by the omission of one cylinder. In a further modification, Fig. 3, the fuel supply is controlled by a shaft 1 controlled by a spring 31 and fitted with a crankarm 2 provided with a stop surface 19a, and adjustable stop surfaces 19b, 19c, and 22a, which are adapted to be acted upon by rollers 17a, 17b, 17c on piston rods 3a, 3b, 3c, arranged in cylinders A, B, C, which can be put under pressure singly to give three of the required positions of adjustment. The auxiliary control mechanism in this case comprises a lever 24 pivoted to a fixed pivot 23 and carrying a further lever 26 fitted with abutments 26a, 26b which may be engaged by abutment pieces 18a, 18b on the piston rods 3a, 3b, and the lever 24 has an abutment 24c which may be engaged by an abutment piece 18c on the piston rod 3c. These abutments cause two intermediate adjustments if after all three cylinders are put into compression first the cylinder A and then the cylinder B is put into evacuation. A sixth position may be obtained by employing an extension 24a to the lever 24 and causing this to actuate a lever 28 provided with a roller 29 which can act on the adjustable stop 22a. The lever 28 is actuated when both the cylinders A. B are put under pressure.