These valves can be operated by either AC or DC power. The flow control variety of valve generally selects an orifice which only allows a specified volume of flow to pass. The specified volume controls the speed of a cylinder or hydraulic motor.
Likewise, the pressure control type is used to select a particular pressure setting. Changing direction, flow or pressure during machine operation with these valves would require a separate individual valve for each direction, flow or pressure desired. The hydraulic circuit would become quite complex very quickly! The technological solution to these more complex circuits has been the development of proportional valves. These revolutionary valves allow infinite positioning of spools, thus providing infinitely adjustable flow volumes.
Either stroke-controlled or force-controlled solenoids are used to achieve the infinite positioning of spools. The other major benefit is when the circuit requires more than one speed. No additional hydraulic components are required! These proportional directional valves are controlled by DC power. The proportional controls, used with their associated electronic controls, also add the desirable features of acceleration and deceleration.
Dithering can cause issues with stable flow control. In contrast, our proportional valve uses a single armature design, which offers virtually frictionless performance. Precise flow control is acquired by proportionally moving the single valve armature away from the valve inlet orifice. The total travel distance of the valve armature is only thousands of an inch. A slight increase or decrease in the armature distance from the valve orifice will result in a variable outlet flow rate, avoiding friction and the need for dithering.
A defined trend in the valve industry is emerging: an increased difficulty in differentiating between proportional valves and servos. They were mass produced, whereas servos needed meticulous and precise manufacturing, which made them up to 10 times more expensive. Proportional valves also had wider clearance, so they tolerated contamination more than servo valves. All of that will quickly become a thing of the past as proportional valves start to outperform servos. For example, closed loop proportional valves that function just like servo valves are available in many places.
Using high force, continuous action solenoids with minimum friction moving parts and quick response electronics, proportional valves have servo-like performance without the contamination and high pressure drop of conventional valves.
Proportional valves control flow, actuator position, velocity, toque, and they can synchronize the action of many different cylinders. They work well for applications such as press systems, molding machines, and traditional servo markets like flight simulators and airframe testing. Also, they prove ideal in areas that already use proportional valves but need a performance upgrade with a closed loop system.
If the current is increased, the magnet solenoid moves further against the spring, until the forces are balanced again. Consider that the magnet is attached to a spool in a valve, the pressure or flow can be controlled in proportion to the current applied to the solenoid. Proportional valves are particularly suited to applications where the output pressure or flow is required to vary, either during a process or from one process to the next. They are dependable, cost-effective and give fast response and consistent control.
Proportional valves can help reduce cycle times by quickly achieving a stable pressure or flow. Dependent on the type of proportional valve an electric, or pilot air, supply will be required, with appropriate control.
Air may need to be supplied at a given quality, requiring the correct filtration. Feedback sensors are necessary for the valve to control any particular process, for example, pressure and temperature mentioned above. The proportional valve will need to be connected into the system, so fittings and tubing are essential.
Browse our range of proportional valves to find out more. What is a proportional valve. What is a Proportional Valve?
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