Patent GB-442075-A (GB)
Title: Improvements in mechanism for reversing internal combustion engines
IPC: F01L13/00
Filed: 1934-07-24
Abstract: 442,075. Reversing; starting; stopping. HEMMINGSEN, T. V., 4, Otto Ruds Vej, Copenhagen. July 24, 1934, No. 21603. [Class 7 (v)] A reversing-gear for two-stroke or other marine engines having compressed-air or other starting means is of the kind employing the same variable-phase cam controlling mechanism for driving the fuel-pump actuating gear and/or the valve gear for both ahead and astern running, and in which the phase relationship of the controlling mechanism to the engine crankshaft is changed, for reversing, by temporarily arresting rotation of driven elements when the engine is being started. When the relative rotation of the driving and driven elements has been completed, the arresting device automatically becomes inoperative independently of rendering the starting means inoperative. As shown, the cam shaft 1 carries exhaust cams 100 and is driven through a gear wheel or chain wheel 2 rotatable on a hub 3 secured on the shaft 1 and provided with radial carrier arms 4 forming bearings for two crankshafts 5. The crank-pin of each shaft 5 passes through a block 7 sliding in a slotted guide 8 in the wheel 2 and allowing the shaft 5 to turn through 180‹. Gear wheels 9 on the shafts 5 drive toothed rims 10 on rotatable sleeves 11, 11<a> carrying cams 12 for actuating the fuel-injection pumps. The sleeves 11, 11<a> are connected through gearing 13 ... 16, and the sleeves 11<a> are connected to the cam shaft 1 by a lost-motion coupling comprising claws 17 on the sleeves coacting with claws 18 on the shaft. Rattling of the coupling is prevented by spring-pressed levers or pawls engaging in recesses in the sleeves. The device for arresting the sleeves 11, 11<a> until adjustment of the phase relationship of the sleeves and the cam shaft of the wheel 2 has been completed, comprises a brake cylinder 23 containing a piston 24 acting through a spring 25 on a roller 26, which engages a toothed rim 27 on the sleeve 11 when compressed air is admitted to the cylinder 23. For this purpose, the cylinder 23 is connected by a pipe 32 to a valve 33 adapted to connect the pipe 32 either to a starting-air pipe 35 or to relief ports 37 open to the atmosphere. A starting- air distributer 39, Fig. 7, comprises ahead and astern cams 40<b>, 40<f> on a sleeve 41 displaceable axially by a bell-crank 42, actuated from a reversing lever 50 through links 43, 45 47, 49 and levers 44, 46, 48. The bell-crank lever 48 carries a sector 51 having slots 52b, 52f coacting with an arm 53 on an engine control lever 54, which can only be moved from the " stop " position ST when the reversing lever 50 is in its "ahead" or " astern " position. Mounted on the cam shaft 1 adjacent to the sleeve 11 is a hub 55 on which is threaded a nut 56 displaced axially by relative rotation between the sleeve 11 and shaft 1. A lever 59 engaged by the nut 56 rocks a shaft 60 carrying a bell-crank 61 connected by linkage 62 . . 65 to a lever 66 rotatable on the shaft 69 and formed with a sector 67 having slots for register with the arm 53 on the lever 54. The pivot 70 connecting the links 64, 65 is connected by a link 71 with the reversing lever 50. The arm 61<a> of the lever 61 is connected by a link 73 to a pivoted toothed sector 74 meshing with a bevel wheel 77 on the shaft 78 of a segment 79, which coacts with a pawl 80 on a lever 81 pivoted at 82 on the connection between the lever 44 and link 45. The free end of the lever 81 acts through a lever 84 on the spindle of the valve 33. To reverse the engine, the lever 54 is brought to the " stop " position ST, Figs. 7 and 8, releasing the reversing lever 50. The latter is brought to the position B, moving the cam sleeve 41 to the " astern " position and the linkage 42-49 to the position shown in dotted lines, Fig. 7. The pawl 80 on the lever 81 engages the segment 79 and lifts the valve 37, connecting the brake cylinder 23 to the starting- air pipe 35. The admission of air to the pipe 35 and cylinder 23 takes place only when the lever 54 is moved to the starting position SL, whereupon an arm 86 on the lever acts through a rod 88 and lever 89 to lift a valve 91, Fig. 9, supplying starting air to the pipe 35 and to the distributer 39. The engine is thus started astern. The brake roller 26 engages the toothed rim 27 and holds the sleeves 11, 11<a> until the phase relationship of the sleeves 11, 11<a> and the cam shaft 1 to the wheel 2 has been automatically adjusted; at the same time, the axial movement of the hub 56 turns the shaft 60, whereby the segment 79 is brought into the position shown in dotted lines in Fig. 7, releasing the pawl 80 and allowing the valve 33 to shut off the starting-air inlet 34 and open the relief ports 37. Pressure in the brake cylinder 23 is thus released and the sleeves 11, 11<a> are free to rotate with the cam shaft 1. The rotation of the shaft 60, throught the linkage 62-66, brings the sector 67 into such a position that the lever 54 can be moved beyond the starting position to a running position in which fuel is supplied to the engine and the starting-air valve 91, Fig. 9, is allowed to close. The relative rotation between the cam shaft 1 and sleeve 11 may be utilized to effect, by means of a lever 101, Fig. 1, the reversal of the scavenging pump, lubricating pump &c. When the engine is running, stopping and starting may be effected by the lever 54 without affecting the brake cylinder 23. In modifications : (1) the brake cylinder acts by means of a band brake on a disc on the sleeve 11 ; (2) the brake is actuated mechanically from the lever 54 ; (3) the toothed rim 27 and roller 26 are replaced by a toothed wheel and a pair of pawls or latches disengageable so that only one is active at a time. In two-stroke engines in which exhaust takes place through piston-controlled ports or a valve-controlled extension of the cylinder, the exhaust cams 100 and the means for effecting their angular displacement are omitted.