The two, 2-port, 2-position valves in the meter-out circuit shown here provides two independently adjustable cylinder-extend speeds and two independently adjustable retract speeds. Therefore, the operator can select fast or slow extend modes and fast or slow retract modes; each of the four can be set at a different speed.
|This circuit provides four different speeds — two for extension and two for retraction — which can all be set independently. |
To illustrate how the circuit works, the flow and signal lines for fast extend are shown in color in the drawing. First, solenoid a of 4-port valve A is energized. This produces slow extend. Then, 2-port solenoid valve B is energized, which results in fast extend.
Note that for fast extend, oil flows through both flow control valves C and D. Thus, the ratio of fast flow compared to slow flow can be quite large.
This circuit is from the archives of Bud Trinkel, deceased, and long-time contributor to Hydraulics & Pneumatics.