Spool Valves Allow Soft Unloading

Most 2-position, 2-way screw-in cartridge pilot solenoid valves utilize a poppet style construction to satisfy low leakage requirements. Sun Hydraulics has adopted a different approach that utilizes a precision spool/sleeve design. Available in both 2-position, 2 and 3-way pilot solenoid cartridges, this approach produces leakage characteristics equivalent to poppet style designs.
softshift_techarticle2 Sun’s small pilot solenoid valves are used to unload larger main-stage elements remotely, or by directly integrating the pilot valve into the main-stage element. In this latter approach, unique to Sun, 12 different pilot valves (proportional, solenoid, hydraulic and pneumatic) can be integrated into a variety of main-stage elements.softshift_techarticle1

Since control volumes in pilot circuits are typically small, the lower gain characteristics of spool valves produce a softer unload. To further extend the operating rate, Sun offers a ‘Soft Shift’ option that adds an orifice in the valve’s armature to gain greater control of fluid displacement. Combining the benefits of a spool valve with the ‘Soft Shift’ option extends shift times, which can reduce the hydraulic shock generated when unloading main-stage elements. Sun’s “Soft Shift” option is offered on all of its spool-type solenoid valves.

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