Controlled Pressure Clamping Circuit
The circuit shown in Figure 9-15 provides an example of sequencing plus a controlled clamping pressure, which can be held while the work cylinder is feeding and retracting.
Energizing solenoids “b” of valves G and H causes the delivery of hydraulic pump C to be directed through valves D, E , F, and G to the cap end of the clamp cylinder J. The cylinder J extends until the work piece is fully clamped. When the work piece is clamped and pressure builds up to pre-set limits of the sequence valve E, part of the pump’s output will be directed from valve E through directional control valve Hand into the cap end of work cylinder K, causing it to extend. Valve E ensures minimum pressure, equal to its setting, during operation of cylinder K. Reducing valve F limits the maximum pressure on the cap end of clamping cylinder J.
De-energizing solenoid H-b and energizing solenoid H-a causes delivery of the hydraulic pump C to be diverted through valves E and H to the rod end of the work cylinder K. This causes the work cylinder to fully retract. Solenoid G-b is then de energized and G-a energized. Delivery from the hydraulic pump is then directed through valves E, F, and G to retract clamp cylinder J.