Patent GB-726753-A (GB)
Title: Emergency shutdown controls for diesel engines
IPC: F01M1/24
Filed: 1953-07-21
Abstract: 726,753. Engine stop-gear. CATERPILLAR TRACTOR CO. July 21, 1953 [May 11, 1953], No. 20192/53. Class 122 (4). An emergency stop gear for a Diesel engine comprises a cylinder having disposed therein pistons 28, 38 which are urged apart by a spring 50 and together by supplying engine lubricating oil under pressure to one end of the cylinder and oil under pressure to the other end, whereby should the engine lubricating oil pressure fail one piston 38 is forced toward its cylinder end by the spring 50 and actuates a member 14 to shut off the fuel supply to the engine. Output of the fuel pumps 15 is controlled by the member or rack bar 14 which is connected at one end through a normal speed governor lever 12 to a hand lever 10 and movement of the rack bar to the right increases the engine speed and movement to the left decreases engine speed and eventually stops the engine. The other end of rack bar 14 contacts one arm of a bell crank 16 journalled on a hollow stub shaft 36 having also mounted thereon a bifurcated lever 35 which embraces a pin 37 attached to the piston 38 and slidable in a slot 39 in the cylinder. A pin 40 passes through a hole 41 in the bell crank 16 and underlies lever 35 being urged thereagainst by a torsional spring 42 which also urges the bell crank 16 toward a fixed stop 43. The pin 40 is secured to a link 44 attached to one end of a shaft 45 which passes through the stub shaft 36 and has secured to its other end a hand lever 46 which provides a manual means of stopping the engine or resetting the overspeed device described later. The piston 28 and a further piston 29 are housed in the top portion 26 of an elongated cylinder having a central portion 25 and a lower portion 27 housing the piston 38. The spring 50 is located between the piston 28 and a retainer 51 slidable on a screw 52 threaded in the piston 28. A spring 30 is disposed between the central portion 25 and the piston 28. Two separate engine-driven pumps 60 and 61 are provided. The pump 60 draws oil from the engine crankcase 62 and delivers it through a manifold 64, conduit 65, and a spring-loaded valve 66 to the lower cylindrical portion 27 whilst the pump 61 supplies oil from a reservoir 67 through a metering orifice 68 to the upper cylindrical portion 26. Before starting the engine the rack bar 14 is moved to the right by hand lever 10, the crank 16 and lever 35 being thus rotated clockwise and the piston 38 raised to the position shown in Fig. 4. When the engine starts pressure oil from pump 61 flows to an annulus 70 around piston 28 and then through an orifice 71 to the space 72 above the piston to urge it downwardly until it reaches its lower limit when excess oil from pump 61 escapes through a relief valve 207. At the same time engine lubricating oil supplied by pump 60 to the space 73 below the piston 38 maintains it in position against the action of spring 50. If the lubricating oil pressure fails, check valve 66 is moved to the right and allows oil in space 73 to escape via conduit 62a and spring 50 moves the piston 38 down to rotate bell crank 16 counter-clockwise and move the rack bar 14 to the left to stop the engine. Pump 61 consequently stops and a valve 69 is opened by its spring 75 to allow oil to drain from space 72, piston 28 thereupon moving upward under the influence of spring 30 to the position required for resetting the mechanism. To permit operation of the engine and stop gear in the event of failure of pump 61, a connection 80 is provided between an outlet 81 in the lower cylindrical portion 27 and an inlet 82 in the upper cylindrical portion. In its upper position piston 38 partly uncovers outlet 81 and allows oil to flow to the space 83 above piston 29 and, in normal conditions, the oil pressure in space 72 holds the piston 29 at the top of the cylinder. If pump 61 fails, piston 29 moves down to hold piston 28 in its lower or normal position and also closes the inlet from pump 61 to space 72. If the lubricating oil pressure also fails, piston 38 moves downwardly as before to stop the engine and a port 84 in the piston registers with outlet 81 and oil in space 83 drains through slot 39. An overspeed trip mechanism is also provided comprising engine driven flyweights 90 which in response to engine speed, urge a spring- loaded sleeve 94 to the right and, at a predetermined speed, the sleeve contacts a pin 96 and causes it to press against one end of a pivoted lever 95 and thereby release the other end of the lever from a notch in a pivoted pawl 98 having on its top side a latch 100 which normally engages a shoulder 101 on a spring- loaded plunger 102 abutting the bell crank 16. When the latch 100 is released the plunger 102 is forced to the left by its spring 105 and swings the bell crank 16 counter-clockwise and moves the rack bar 14 to its shut-off position. To reset the overspeed mechanism the bell crank 16 is moved counter-clockwise by means of the hand lever 46 and as the plunger 102 moves to the right a shoulder thereon contacts a tang 108 on pawl 98 and pivots it clockwise until the notch therein is again engaged by lever 95; the rack bar is returned to its operating position by the governor spring 11.