Memory metal: miniature proportional valve uses technology

Paul Boughton

A new type of miniature proportional valve that helps designers to meet the familiar objectives of 'make it smaller, lighter and more energy-efficient' has been developed by Lee Products. The Lee proportional valve is said to offer important advantages when compared with traditional solenoid-type proportional valves, namely saving space, weight and power consumption in analytical machines.

Unlike most of the miniature solenoid valves typically available, the Lee proportional valve uses shape memory wire technology to vary flow and provide actuation, as opposed to a spring. When a current is applied the shape memory alloy wire heats up in the valve and changes shape, this causes deformation and results in the valve opening in proportion to the current applied.

This innovative design eliminates the need for a magnet, coil wire or steel armature typically used in traditional miniature solenoid valves, so it is smaller and lighter. These characteristics will be especially appreciated by designers of portable, hand-held, battery powered instruments such as gas detectors used in OEM, medical, laboratory and other similar applications - for example, mass flow controllers, blood pressure cuff monitors, ventilators and oxygen concentrators.

These Lee proportional valves are suitable for use on air or gases that are clean or dry, non-corrosive and non-flammable.

Other key features of these two-way, normally-closed valves are a weight of 1.2g, a maximum voltage of 1.5V DC (battery powered) and a current draw of 600mA.

The valves have a flow capacity of 8SLPM at 15psig, an operating pressure of 15psig and an operating temperature range of 4 to 40 degrees C (40 to 105 degrees F). They are constructed from FKM elastomer with wetted materials including polycarbonate, brass, elastomer, PEEK, 316 stainless steel, Flexinol and epoxy.

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