SEAT GP 1772308 - Caterpillar

Pedal Control
LOCATION OF THE GOVERNOR CONTROL PEDALS ON 637D AND 639D
1. Pedal for tractor engine. 2. Pedal for scraper engine. 3. Governor control valve (under pedal).The speed of the tractor engine is controlled by pedal (1), which is mechanically connected to the tractor engine governor. The scraper engine is controlled by pedal (2), which activates governor control valve (3) for the scraper engine. The governor control valve sends air pressure to air chamber (4) and causes it to activate. The air chamber controls the movement of scraper governor control lever (5) which controls the engine speed.
LOCATION OF THE AIR CHAMBER FOR THE SCRAPER ENGINE GOVERNOR
4. Air chamber. 5. Scraper governor control lever.Governor Control Valve For the Scraper Engine
The governor control valve is under the floor plate of the cab. It is activated by the governor control pedal for the scraper engine. The pedal is against the screw in plunger (1) of the governor control valve.The governor control valve for the scraper engine uses pressure air to control the rpm of the scraper engine. Pressure air is sent from the governor control valve to an air chamber on the scraper engine. The air chamber is connected to the control lever on the engine governor. With the scraper engine running and the governor control pedal released, no pressure air is in the line from the governor control valve to the air chamber. The scraper engine will run at low idle rpm.When the governor control pedal is pushed, plunger (1) is moved down. Plunger (1) puts spring (3) in compression. The force of spring (3) will move piston (4) and retainer (7) down to valve (8). This closes passage (9) to exhaust passage (6). The movement of piston (4) and retainer (7) will then move valve (8) down against the force of springs (10) and (12). Valve (8) will move off of the seat in retainer (13). Pressure air can then go from supply passage (14) to delivery passage (11) and to the air chamber on the scraper engine.When the pressure air in delivery passage (11) and the force of springs (10) and (12) becomes more than the force of spring (3), valve (8), piston (4) and retainer (7) will move up against the force of spring (3) until valve (8) again comes in contact with the seat in retainer (13). This stops the flow of air through supply passage (14). Valve (8) is in contact with piston (4), so passage (9) to exhaust passage (6) is still closed. The governor control valve is now in balance and pressure air is held in the line to the air chamber.When the pedal is pushed down fully, retainer (2) puts spring (5) in compression. The pressure air in delivery passage (11) will now have to become approximately 36 psi (250 kPa) before springs (10) and (12) can move valve (8), piston (4) and retainer (7) up to close supply passage (14).If the pedal is lifted a small amount, the mechanical force above piston