What is in this article?:
- BOOK 2, CHAPTER 10: Flow control circuits
- Types of flow-control circuits
- 3-speed meter-in circuit
- Meter-in flow control of a running-away load
- When meter-in circuits are necessary
- Action of a meter-in air circuit with a varying load
- Meter-out flow controls
- Three-speed meter-out circuit
- Meter-out pneumatic circuit with a variable load
- Bleed-off or bypass flow controls
- Three-speed bleed-off circuit
- Different locations for flow controls
- Heat generation in hydraulic flow-control circuits
- Motor-type flow-divider speed control
- Another motor-type flow-divider speed control
- Controlling speed of hydraulic motors
- Three-port flow control
Another motor-type flow-divider speed control
Figures 10-60 through 10-63 show a different type of motor flow-divider circuit for variable speed. This circuit uses a smaller pump, electric motor, and tank to give the same speed but less force at high speed. Notice there is a 3-gpm pump feeding one section of the flow divider. As this section of the flow divider turns, the other two sections turn and pump fluid directly from the tank. In Figure 10-60 the two right-hand sections of the flow divider are only circulating oil. All pump flow is going to the cylinder, which is operating at slow speed. In this condition, the cylinder is capable of generating its highest tonnage. Notice the cylinder requires 300 psi to move it and the pump is showing 300 psi.
Fig. 10-60. Meter-in flow-control circuit with motor-type flow divider (to minimize heat) – cylinder extending at slow speed.
The cylinder speeds up when solenoid C2 on the left-hand 3-way valve is energized, as in Figure 10-61. Now, one flow-divider section sends its oil to the cylinder along with pump flow. The cylinder goes to mid speed and pump pressure climbs to 600 psi.
Fig. 10-61. Meter-in flow-control circuit with motor-type flow divider (to minimize heat) – cylinder extending at middle speed.
Fig. 10-62. Meter-in flow-control circuit with motor-type flow divider (to minimize heat) – cylinder extending at fast speed.
To get full speed from the cylinder, energize solenoid C1 on the right hand 3-way valve, as shown in Figure10-63. Now all three sections of the flow divider feed the cylinder. The cylinder strokes at fast speed and pump pressure climbs to 900 psi.
If the pressure required to move the cylinder to the load is low, this system works well. There is enough flow to move rapidly at low pressure and enough pressure at low flow to do the work.
Note: Standard gear-motor flow dividers are noisy. In the two circuits just discussed, the flow divider runs continuously. The high noise level may be detrimental in some locations.
Fig. 10-63. Meter-in flow-control circuit with motor-type flow divider (to minimize heat) – cylinder retracting at fast speed.