GUARD AS 2278802 - Caterpillar

Illustration 1 g00737979
(1) Start valve
(2) Lubricator
(3) Starting motor
(4) Relay valve
Illustration 2 g00811855
Air starting motor (typical example)
(5) Air inlet
(6) Vanes
(7) Rotor
(8) Pinion
(9) Spring
(10) Piston
(11) Reduction gears The air from the supply goes to relay valve (4). The air flow is stopped by the relay valve until start valve (1) is activated. When the start valve is activated, pressurized air is supplied to piston (10). The air pressure behind the piston compresses spring (9). The spring moves the drive shaft and pinion (8) in order to engage the flywheel ring gear.The air flow goes through lubricator (2). A tube in the body of the lubricator provides a vacuum above the oil in the bowl. Oil from the bowl enters the body's chamber that is attached to the air line. The lubricated pressurized air flows through air inlet (5).The air pressure against vanes (6) turns rotor (7). The rotor turns the drive shaft and pinion (8) through reduction gears (11). The pinion rotates the flywheel ring gear and the crankshaft. The pressurized air is exhausted through the air outlet at the bottom of the starting motor.When the engine starts to run, the flywheel will begin to turn faster than pinion (8). The design of the drive shaft for the pinion allows the pinion to move away from the flywheel in order to disengage from the flywheel ring gear. This prevents damage to the starting motor and the flywheel ring gear.When start valve (1) is released, relay valve (4) stops the air flow to the starting motor. The air pressure to piston (10) stops. Spring (9) retracts the piston, the drive shaft, and pinion (8).