Patent GB-807492-A (GB)
Title: Emergency shutdown control for internal combustion engines
IPC: F01M1/24
Filed: 1957-04-08
Abstract: 807,492. Engine stop-gear. CATERPILLAR TRACTOR CO. April 8, 1957 [Jan. 17, 1957], No. 11345/57. Class 122 (4). An emergency stop-gear for an internal combustion engine comprises a spring- loaded plunger C connected to the fuel control member 11 and held, under normal engine - operating conditions, by a latch D which, in the event of lubricating oil pressure failure, is tripped by pressure-responsive means, including a delay mechanism to shutoff the fuel supply and stop the engine. The latch D pivots on a pin 22 and has a toe 21 to engage under a flange 14 of the plunger C. A shaft 12 driven from the engine drives a worm 28 and worm-wheel 29 to rotate a lead screw 27 fixed to the worm-wheel. A finger 31 pivotally and slidably mounted on a shaft 32, parallel to the screw 27, has an arcuate notch 33 threaded to engage the screw and a projection 34 that engages in a groove 36 in a block 37 slidable on pins 38 and urged by springs 49 into contact with the rod 43 of a piston 42 which is subjected to the pressure of lubricating oil supplied through a connection 47. Under normal conditions; oil pressure acting on the piston 42 forces it and the block 37 to the right as seen dotted in Fig. 3, to pivot the finger 31 free of engagement with the lead screw 27. When the oil pressure falls below a predetermined value the piston and block 37 are moved to the left by springs 49 and the finger 31 engages the lead screw and is moved axially along the shaft 32 against a spring 51. If the low oil pressure condition prevails for a sufficient time to allow the finger to traverse the length of the lead screw a pin 52 on the projection 34 engages and trips the latch D to free the plunger C to move downwards and thereby shut down the engine. A delay period is thus provided which is longer at slower engine speeds and allows time to motor the engine, when starting, with subnormal oil pressure. The stop-gear also includes an overspeed safety device comprising a shaft 56 driven from the shaft 12 through a gear train 26 and having an enlarged portion 57 containing a weight 58 which is normally held in position by a spring 59 but moves outwardly at excessive speeds to trip the latch D and thus stop the engine. The latch may be tripped manually by rotating the head 64 of the pin 22. The overspeed control may also be operated manually by depressing a rod 66 having a tapered head 68 engaging a corresponding taper 71 on the weight 58. A manual reset for the oil pressure control may be provided in the form of a plunger slidably mounted in the cylinder head 46 and by means of which the piston 42 may be manually moved to the right to disengage the finger 31 from the lead screw 27, the finger then being returned to the position shown in Fig. 1 by the spring 51. The stop gear may also be operated by a thermostat in the engine cooling system which, when the cooling water temperature exceeds a predetermined value, operates a relief valve in the lubricating oil system, thereby simulating an oil pressure failure condition which shuts down the engine as described above.