PLATE 3626308 - Caterpillar

Propel System Circuit In Neutral Position With Stop Control Off
(1) Propel hand control valve.(2) Automatic speed control block.(3) Brake valve group.(4) Brake control solenoid valve.(5) Line for charge oil from steering pump.(8) Hydraulic displacement control valve.(12) Propel pump.(16) Front (spring applied) brakes.(17) Rear drum (spring applied) brakes.(18) Brake and control line.Solenoid valve (4) becomes energized when the stop control on the dashboard is pulled up. Oil now flows across the spool valve from charge pump circuit line (5) into control line (18).The pressure oil releases parking brakes (16) and (17). At the same time, oil flows to control valve (1). With the lever in the neutral travel position, the oil remains blocked at the two spool valves inside the control lever unit.Charge pump oil passes through the rest of the circuit the same way as Neutral Position With Stop Control On. Forward Drive Position
Propel System Circuit In Forward Drive(1) Hand control valve.(2) Automatic speed control block.(4) Brake control solenoid valve.(8) Hydraulic displacement control valve.(9) Orifice (for pressure override relief).(10) Hydraulic servo.(11) Orifice (for Propel pump cooling).(12) Propel pump.(13F) Main (high pressure) relief valve for FORWARD.(14) Front propel motors.(15) Rear propel motors.(16) Front drum (spring applied) brakes.(17) Rear drum (spring applied) brakes.(18) Brake and control line.(19) Pressure override relief valve.(20) Flow to vibratory system.(21) Forward control valve.(22) Passage for control oil from forward control valve.(23) Adjustable orifice (for speed control balancing).(24) Check valve.(25) Rotary selector (for automatic speed control).(26) Orifice (for servo).(27) POR shuttle valve.(28) Servo control line.(29) Charge pump line.(30) High pressure loop line.(31) Low pressure (return) loop line.(32) Exchange (cooling) valve.With the engine running, and the stop control pulled up, forward movement of the propel control lever allows oil from control line (18) to pass through forward control valve (21) of propel hand control valve (1). The oil goes into passage (22). It then passes through adjustable speed control orifice (23). This passage sends the oil into check valve (24) and on to rotary selector (for automatic speed control) (25). With rotary selector (25) set at minimum speed, oil flow goes to the hydraulic tank. When the rotary selector is rotated clockwise, it restricts oil flow to tank and increases oil pressure in the control circuit going to hydraulic displacement control valve (8). The machine speed increases proportionately.Oil pressure in control circuit (22) is regulated by turning rotary selector (25) of automatic speed control block (2). Movement of the spool section of hydraulic displacement control valve (8) is proportional to the oil pressure found in control circuit (22).When rotary selector (25) is closed (turned fully clockwise), maximum pressure is found in control circuit (22). This corresponds to maximum spool movement of valve (8). The spool is shifted from position (D) to position (C). This allows oil to pass across the spool valve from charge pump line (29) into servo control line (28). The oil pressure moves hydraulic servo (10) which in turn increases the angle of the swashplate of pump (12) to its maximum. Pump (12) gives