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GATE-OPEN 4644972 - Caterpillar



4644972 GATE-OPEN Caterpillar parts GATE
Rating:
41
Alternative (cross code) number:
CA4644972
464-4972
4644972
Caterpillar 4644972 GATE-OPEN
Weight: 0.28 pounds 0 kg.

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Low Pressure Standby
When piston pump (1) produces flow, the system pressure begins to increase because the oil flow from pump outlet (5) is blocked at the closed center implement control valves.The supply pressure from pump outlet (5) is felt at the bottom end of margin spool (13). The supply pressure from pump outlet (5) is greater than the combined pressure of load sensing oil pressure, boost pressure (11), and margin spring (10). The flow compensator spool moves upward against the margin spring. This permits system oil to flow to actuator piston (3) .When the pressure on actuator piston (3) increases, the force of bias spring (2) is overcome and swashplate (18) is moved to a slight angle.Piston pump (1) produces enough flow in order to compensate for normal system leakage when swashplate (18) is at a slight angle. Also, the piston pump has sufficient pressure in order to provide instantaneous response when an implement is activated.Pressure at pump outlet (5) is called "low pressure standby". The low-pressure standby is higher than the margin pressure due to additional load sense boost pressure. The higher pressure is needed to improve implement response time.When piston pump (1) is at low-pressure standby, the supply pressure from pump outlet (5) raises margin spool (13) higher. This will further compress margin spring (10). An increased amount of supply oil from pump outlet (5) will flow to actuator piston (3). This will slightly destroke the hydraulic pump.The low-pressure standby can be adjusted by changing the setting of margin spring (10) .Upstroke
Illustration 2 g03716819
Implement pump (upstroke) (1) Piston pump (2) Bias spring (3) Actuator piston (4) Passage (5) Pump outlet (6) Passage to actuator piston (7) Orifices (8) Orifice (9) Adjustment screw (10) Margin spring (11) Load sensing oil pressure and boost pressure combined. (12) Compensator valve (13) Margin spool (14) Cutoff spool (15) Line to the control valve group (16) Pump inlet (17) Piston and barrel assembly (18) Swashplate (19) Shaft (20) Load sensing relief valveWhen an implement hydraulic circuit requires flow, the pressure from pump outlet (5) is reduced. The force of margin spring (10), boost pressure, and load sensing oil pressure (11) is greater than supply pressure from pump outlet (5). The overall force is on the top end of margin spool (13). The load sensing boost is used to improve implement cycle time.The spool moves down. The spool blocks the flow of oil to actuator piston (3). Oil that is in the chamber for actuator piston (3) is vented to the case drain across margin spool (13) allowing bias spring (2) to move swashplate (18) to a greater angle.The pump now produces more flow. This condition is known as "upstroking".The following conditions can result in upstroking the pump:
If an implement hydraulic circuit is initially activated from low-pressure standby, the load sensing oil increases the pump output flow. This increased pump output flow is routed to the position of a main control spool of a hydraulic control


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