EDGE-CUTTING 4T6262 - Caterpillar

Introduction
A combined overspeed and low oil pressure safety shutoff is provided for industrial engines, but is available as an attachment on earlier marine engines.Later D398 and D399 Marine Engines are equipped with reversal protection in addition to overspeed. The reversal protection safety shutoff is available as an attachment for D379 Marine Engines.The safety shutoff (1) is mounted in the V of the engine at the rear of the governor housing with the control driven from the fuel pump and governor drive shaft.Engine lubricating oil pressure is used to actuate the low oil pressure shutoff control portion. The plug (2) provides for a connection of oil pressure to a water temperature shutoff control valve. The line (4) supplies engine oil pressure to the shutoff control.
SAFETY SHUTOFF CONTROL
1. Safety shutoff control. 2. Plug (pressure oil connection to water temperature shutoff). 3. Fuel rack shutoff. 4. Pressure oil line to shutoff control. 5. Reset button. 6. Emergency manual shutoff button.The overspeed shutoff portion of the control stops the engine mechanically in the event of engine overspeeding.Controls equipped with reversal protection are activated by low oil pressure in the event the engine runs in reverse.The emergency manual shutoff button (6) works in conjunction with the overspeed shutoff and provides the operator with an emergency shutoff.Reset button (5) is used to reset the control after the engine has been stopped by the control because of low oil pressure or high water temperature. It is not necessary to reset the control after a normal engine stopping.The shutoff mechanisms receive lubricating oil from leakage past the oil pressure shutoff piston. An internal drain is provided by two drilled holes in the bottom of the housing.Operation
Low Oil Pressure Shutoff and Water Temperature Shutoff
The oil pressure control will stop the engine should the lubricating oil pressure drop below the safe operating range, or when excessively hot water opens a shutoff control valve which simulates low oil pressure.Under normal engine operating conditions, engine lubricating oil is directed through supply line (4), see previous illustration, to cover (4). This oil is then directed against control piston (6).One end of worm slide follower (2) is piloted into guide (5). The follower is free to pivot about slide follower shaft (3) in the housing and is actuated by the movement of guide (5).
SHUTOFF CONTROL (Cross Sectional Side View; Normal Operation)
1. Worm shaft. 2. Slide follower. 3. Slide follower shaft. 4. Cover. 5. Guide. 6. Piston. 7. Spring. 8. Release rod.Worm shaft (1) is driven by the safety shutoff drive which is driven by the fuel pump and governor drive shaft thus rotating any time the engine is operating.When the engine oil pressure is within the safe operating range, the piston (6) is held against the guide (5) compressing the spring (7) and pivoting the slide follower (2) out of mesh with the worm shaft (1).Should the lubricating oil pressure drop below normal operating range, the oil pressure acting on piston (6) will also drop and spring (7) will force guide (5)