ENGINE AR 2350300 - Caterpillar

When the upper structure or implements are operated during machine travel, straight travel control valve (2) will maintain straight travel of the machine. This makes combined operations easier. Examples include laying pipe and clearing timber.When the machine travels without swing operation or implement operation, oil from right pump (7) goes into the right travel motor through straight travel control valve (2) and right travel control valve (1). Oil from left pump (8) goes to the left travel motor through straight travel control valve (2) and left travel control valve (3) . Because the travel circuits are separated, the machine continues to travel straight, unless a difference in travel resistance occurs between the right and left tracks. Without the straight travel system, swing operation or implement operation while travelling would cause right pump (7) and left pump (8) to supply varying amounts of pump oil to the track motors. This would cause the right travel motors and left travel motors to rotate at different speeds. This would cause the machine to turn, and straight travel would be impossible.The straight travel system controls the machine travel in order to provide straight travel of the machine while other circuits are operated at the same time. The following actions occur when pilot oil pressure activates straight travel control valve (2) .
Left pump oil flows only to the right and left travel motors. The pump oil drives both motors in parallel.
Part of the right pump oil flows into the swing and the implements. The swing and the implements do not use much of the pump oil because the swing and implements move at low speed. This maintains the stability of the machine as the machine travels. The remaining right pump oil is supplied to the right and left travel motors.Travel and Implement Operation
Illustration 3 g00680472
Hydraulic schematic of straight travel operation (1) Main control valve (2) Pilot passage (3) Pilot passage (4) Pilot passage (5) Stick I control valve (6) Swing control valve (7) Left travel control valve (8) Center bypass (9) Straight travel control valve (10) Right travel control valve (11) Passage (12) Boom I control valve (13) Bucket control valve (14) Passage (15) Center bypass (16) Passage (17) Passage (18) Pilot passage (19) Pilot passage (20) Passage (22) Parallel feeder passage (23) Passage (24) Parallel feeder passage (25) Pilot passage (26) Pilot oil manifold (27) Line (28) Line (29) Drain line (30) Hydraulic tank (31) Right pump (32) Left pump (33) Pilot pumpMoving the control lever to the BOOM RAISE position during forward travel causes the following actions: Pilot oil from the boom pilot control valve and the travel pilot control valve is supplied to pilot passages (4), (3), and (2). Boom I control valve (12), right travel control valve (10), and left travel control valve (7) are activated. Passage (11) is closed. The pressure in pilot passages (18) and (19) increases, and straight travel control valve (9) is activated. Stick I control valve (5), swing control valve