From our earlier discussions, we have seen how a sequence valve can be used to create sequential operations in a hydraulic circuit.
The circuit depicted in Figure 10.6 contains a hydraulic system in which two sequence valves are used to control the sequence of operation of two double-acting cylinders.
When the DCV is shifted into its left envelope mode, the left cylinder extends completely and then the right cylinder extends. If the DCV is shifted into its right envelope mode, the right cylinder retracts fully followed by the left cylinder. This sequence of the cylinder operation is controlled by the sequence valves. The spring centered position of the DCV locks both the cylinders in place.
The best example of this circuit is the case of a production operation. The left cylinder should extend in order to accomplish the job of clamping a work piece with the help of a power vice jaw. The right cylinder extends to drive a spindle to drill a hole in the work piece. After the hole has been drilled, the right cylinder retracts first and then the left one. The sequence valve installed in the circuit ensures that these operations occur in a predefined fashion.