Patent GB-901903-A (GB)
Title: Improvements in and relating to the starting and stopping of free-piston engines
IPC: F02C5/08
Filed: 1959-03-17
Abstract: 901,903. Free-piston engines and gas generators; starting; stopping. SOC. D'ETUDES ET DE PARTICIPATIONS EAU GAZ, ELECTRICITE, ENERGIE S.A. March 17, 1959 [April 9, 1958], No. 9269/59. Classes 7(1) and 7(5) A free-piston engine including a device for stopping and starting the engine the device comprising a source of fluid under pressure arranged to act under the control of a manually operable control element on the one hand upon the injection pump to stop the injection thereby of fuel into the power cylinder and on the other hand upon a positioning member co-operating with the free piston assembly and displaceable by the pressure of the fluid acting in a cylinder separate from the cushion in such a manner as to move the free piston assembly into its starting position is characterized by a second control element arranged to be actuated by an impulse generated automatically when the engine stops and also serving to cause the fluid under pressure to prevent injection of fuel by the injection pump and to effect the displacement of the positioning member. The control of starting is effected by pressing the button on member 83. The resulting closure of the switch 68 closes an electric circuit comprising branches C and NA connected by the lines Pa and Pb. The coil 50a is energized and the movable part 54 of the valve 50 descends against the action of the spring 54a the effect of which is to apply fluid pressure to the right-hand face of the piston 53. The rack 47 moves to the left driving the toothed wheel 48 through a quarter of a revolution by co-operation of the pawl 4a and tooth 45 of the ratchet wheel 44 in engagement with the pawl. This rotation of 90 degrees of the spindle 34a has the effect of opening the valve 41 by means of the boss 37a bearing on the pushrod 40. The compressed air of the cylinder 38 thus passes by way of pipeline 39 to the branch 39a and owing to the new position of the valve 35 to the pipeline 26 and cylinder 21 compressed air then fills the starting tank 18. At the same time the displacement of the movable part 46 in the direction of the arrow F and the rotation of the spindle 34a in the direction of the arrow F have the effect of opening the circuit Pa NA PbC at the switches 62 and 58, this circuit remaining broken when the pressure on the button 83 is released. The actuation of the valve 50 however has closed the contactor 57 which has energized the holding circuit M which remains energized until the movable part 46 reaches its limiting left-hand position (corresponding to a quarter of a revolution of the spindle 34a). When this position is reached (i.e. when the spindle 34a occupies the position of Fig. 2) the switch 59 is opened by the rack 47 and under the action of the spring 54a the movable part 54 of the valve 50 resumes the position shown in the Figure. Thus the piston 53 is moved in a direction opposite to that of the arrow F until it closes the switch 58 all the switches and contactors are then in the positions which they originally occupied with the exception of switch 62 which remains open, rendering inoperative the starting members 83 and 84 acting on the branches NA and Na which are interrupted by the opening of switch 62. As long as the distribution valve member 34 is in the position shown in Fig. 2 the tank 18 remains charged with air under pressure. When the pressure necessary for starting the engine has been reached in tank 18 this pressure acts through the pipe line 91 on the servc-contactor 92 and closes the contactor 65. Closing of this contactor has the effect of acting on the valve 50 and consequently of causing the rack 47 to move to the left until the member 34 has again rotated through 90 degrees. It should be noted that as in the preceding position the holding circuit M rapidly replaced the aforesaid circuit which is broken first by the opening of 58 then as soon as the pressure has dropped in the tank 18 by the opening of 65. During this rotation of member 34 through 90 degrees from the position of Fig. 2 the compressed air in the cylinder 21 has escaped into the open air by pipeline 26 and valve 35. This results in the opening of valve 20 and consequently the transfer of compressed air from tank 18 to compartment 2b. When the member 34 has rotated 180 degrees from its original position the switch 59 is opened by the rack 47 causing the movable part 46 to return to the position of Fig. 1. When the piston or pistons have been set in motion by the compressed air the engine rapidly assumes its normal conditions, the pressure in the cylinder 32 having been released by the pipeline 33 being put into communication with the atmosphere a when the cock 36 was in the position shown in Fig. 4. Under working conditions with the member 34 rotated 180 degrees from its original position the valve 41 is shut, switch 62 is open while switch 63 is closed. Finally switch 61 (which up to this time had been ineffective due to the opening of switch 63) is open owing to the fact that the operating indicator has moved the movable part 72a of the valve 72 to the right. Stopping of the engine may be brought about at will by pressing the button or member 69 but it may also occur unintentionally for example if there is a device (not shown) for interrupting the operation of the engine when the stroke of the free piston exceeds a certain amplitude. In the first case closing of the switch 66 closes the circuit N energizing the coil 50a by lines Pa, Pb and branches C and NC. In the second case when the piston 3-4 ceases to move in the cylinder 2 the piston 74 moves to the left to attain the position shown and the contactor 61 which had been opened when the engine commenced to work is closed. The circuit N is then established. Closing of the aforesaid circuits has the effect of producing the movement in the direction of the arrow F of the piston 53 and a fresh rotation of the member 34. When the member 34 has turned through 270 degrees from the position of Fig. 1 compressed air is sent via valve 36 to the cylinder 27 the effect of which is to force the piston 28 downward and bring piston 3-4 into the starting position. When the piston 3-4 has reached the starting position compressed air passes to the pipeline 93 and closes the contactor 64. This produces a fresh rotation of the member 34 through 90 degrees which member re-occupies the position shown in Fig. 1. When it is desired that automatic restarting should take place as the result of an unintentional stoppage it is merely necessary to press button 84 to close switch 67. In these conditions following an unintentional stoppage of the engine the member 34 is moved from the position of Fig. 1 through 180 degrees to the running position. When insufficient pressure prevails in the safety oil circuit s switch 90 is open and this prevents any fresh restarting. Means may be provided for ensuring immediate starting of the engine when required by previous filling of the starting tank 18 the discharge of this tank into the part 2b of cylinder 2 taking place only at the moment desired by the attendant. As shown in broken lines in Fig. 1 these means may comprise:- A switch 101 and a device limiting the pressure in the starting tank 18, this device comprising a cylinder 102 in which moves a piston 104 which piston acts upon a cock or valve 107. In a modification the various circuits instead of being electric circuits could be circuits for the distribution of a fluid (air, oil, &c.) under pressure the other parts being modified as necessary. The operating indicator device 73 is similar to that described in Specification 753,924. The invention applies more particularly but not exclusively to free-piston gas generators.