sequencing of two double-acting hydraulic cylinders

SEQUENCING OF TWO DOUBLE-ACTING HYDRAULIC CYLINDERS

1. Functional and Operational Requirements

As we know sequence valves are used extensively for sequencing operations when two or more cylinders are involved. These valves which are usually spring loaded, have been described already in Chapter 6, Section 6.19. The following circuit shows the use of a sequence valve in a two double-acting cylinder.

2. Circuit

Fig. 8.10 illustrates a circuit that uses two sequence valves to control the sequence of operations of two double-acting cylinders.

This circuit has a manually-operated, spring-centered 4/3 DC valve, two sequencing valves, two check valves, and a pressure relief valve. Let us take that cylinder-1 is used to clamp the workpiece and cylinder-2 is to perform punching; and the sequence of operation as clamping first and then punching.

3. Operation

Left mode position: When the 4/3 DC valve is shifted manually to the left envelope flow path configuration, the cylinder-1 extends completely and the workpiece is clamped. Once the cylinder-1 reaches its end of the stroke, pressure is increased and sequence valve 1 opens and the oil starts to flow into the cylinder-2. Now the cylinder-2 extends to drive a spindle to do punching operation in the workpiece.

Right mode position : When the 4/3 DC valve is shifted to the right mode, the cylinder-2 retracts. Once the cylinder-2 retracts completely, the sequence valve 2 opens and the oil starts to flow into the cylinder-1. It causes the cylinder-1 to retract and hence the unclamping of workpiece is achieved.

Spring-centered position: When the 4/3 DC valve is shifted to the spring-centered position, the oil drains back to the tank through the pressure relief valve. Thus during the spring-centered position, both cylinders are hydraulically locked.