Parker Hannifin VO40 Open-Center Directional Control Valve, Technical Information, Operation

Catalog HY17-8505/UK	Open-Center Directional Control Valve
Technical Information	VO40
General Description

The VO40 is an open-center directional control valve with the flexibility of sectional construction. Consis- tent with this technology, it is simple in its application, reliable, easy to troubleshoot, and cost effective. The global design reflects the performance and quality ex- pected by today’s machine designers. Spools have me- tering notches in the three critical areas – open- center, parallel path and tank, which optimizes simultaneous metering. Contemporary honing technology is used to deliver low work port to tank leakage. Additionally, each work section has a transition check to ensure that a load does not “dip” during simultaneous operation. All of these features, plus those listed below, were intend- ed to take machine controllability to the next level.

Operation

The VO40 incorporates traditional open-center technol- ogy. It is usually interfaced with a constant flow pump, whose flow is routed directly to tank when the spools are in neutral. When one or more spools are selected, flow is directed to the actuators. The throttling of that flow depends upon the spool position and the design of the metering notches. Spool notches can be designed to accommodate resistive loads (meter-in) and nega- tive loads (meter-out). To accommodate multiple pump circuits, split flow and combined flow mid inlets are available.

Benefits

•Enhanced metering – especially during simultaneous operation, this is accomplished by having notches in the three critical areas of the spool: open center, parallel path and tank.

•Improved simultaneous metering – having a transition check in each work section ensures that a load does not “dip” downward when metering two or more work-sections.

•Repeatability – consistent metering from valve to valve is achieved by flycutting all of the critical cast lands. This means that the notch position relative to the spool stroke is controlled and predictable. The result is consistent machine control.

•Reduced operator fatigue – the open-center core is a split wing or “Y” core design, which provides for a consistent lever force when selecting the spool from neutral to both power positions.

•Reduced function drift – low internal leakage accomplished thru the use of contemporary honing technology. Also, for those functions requiring near zero drift, pilot-operated checks are available.

•Small footprint – port accessories are installed vertical to the spool, allowing the handle to be positioned closer to the valve body.

•Ease of service – the bottom two stud assemblies are slotted, enabling a work section to be replaced without completely disassembling the valve assembly. This is accomplished by loosening the top tie bolt and then lifting the section out of the assembly. Downtime is minimized.

•Easy conversion from a left-handed to a right-handed section – the work section housing and spool are symmetrical, which enables the spool to be inserted in either end of the housing.

•Improved spool seal life – the enclosed handle assembly protects the spool and spool seal area from contamination and the potential corrosion.

Parker Hannifin Corporation