PLANETARY GP 7G4635 - Caterpillar

Illustration 1 g00942531
(1) Valve bridge
(2) Rocker arm
(3) Pushrod
(4) Valve rotator
(5) Valve spring
(6) Valve guide
(7) Valve
(8) Valve lifter
(9) Camshaft lobe The crankshaft gear drives the camshaft gear through an idler gear. The camshafts must be timed to the crankshaft in order to get the correct relation between the movement of the piston and movement of the valves.The camshafts have two camshaft lobes (9) for each cylinder. As the camshaft turns, the camshaft lobe causes valve lifter (8) and pushrod (3) to move up and down.The pushrod moves rocker arm (2). Movement of the rocker arm causes valve bridge (1) to move up and down on a dowel in the cylinder head. This movement operates valves (7) in valve guides (6). The valve bridge enables one rocker arm to operate two valves simultaneously. There are two inlet valves and two exhaust valves for each cylinder.Valve rotator (4) turns the valve during engine operation. The rotation of the valves keeps the deposit of carbon on the valves to a minimum. This provides longer service life for the valves.When valve lifters (8) move downward, valve spring (5) closes the valve.