Yuken Sequence Valves
These valves control the sequential operation of two or more actuators. If the inlet pressure exceeds a preset level, they deliver effective pressure to the outlet side. The valves can serve as pressure holding valves to maintain hydraulic pressure in a circuit. When a sequence valve is installed between a directional control valve and a cylinder, it needs reversed free flow; therefore, the valve should contain a check valve. The sequence valves and counterbalance valves, described in the next section, are generally known as H/HC type pressure control valves, and how they are assembled determines the nature of the combined valve, either H or HC type.
Note that a sequence valve with an auxiliary pilot port can provide two-pressure control (high/low) by delivering the pilot pressure of the auxiliary pilot port to the pilot piston. Pressure required for this auxiliary remote control is approximately 1/8 of the adjustment pressure (approximately 1/16 when the adjustment pressure is 7 MPa (1 015 psi) or more). The example is shown in Fig. 3.10.
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