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The automation of production equipment and processes with the aid of electronic
regulation and control equipment requires interfaces between the electronic
and fluidic control loops.
The valve described below for regulating the flow rate of liquids and gases
represents such an interface. Fluids are mainly delivered and isolated by
solenoid actuated on-off valves. However, the way they and manually actuated
throttle valves operate does not meet certain flow requirements. Therefore,
wherever exact adjustment to the actual requirement is needed, one of the wide
range of motorised valves on offer is used. Depending on the application and
accuracy required, it is possible to chose between an extremely wide variety
of control element and drive design principles.
This is a rotary valve, with two oxide ceramic throttling discs which resist
dirt and do not wear.
The maintenance free electrical servodrive consists of powerful reversible
motors; with a choice between DC, synchronous and stepper designs to suit
the type of control system available.
The backlash free gearing, which is positively connected to the drive shaft
in order to rotate the control disc, guarantees a reproducible defined control
characteristic. The limit - i.e. valve closed or fully open - is detected by
two separate, floating microswitches. As a result of the low power consumption
of between 1.5 and 5W, the electronic regulator can operate certain types of
motor directly.
For controlling the motorised valve, various regulators and electronic
components are offered, which in combination with the valve allow simple
control through to complex regulation problems to be solved, e.g. flow and
temperature regulation or electronic control cards like servo-amplifier or
stepper motor controller.
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Description of operation:
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Control discs:
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One of these discs opens two opposite triangular flow apertures in the other
continuously, over an angle of rotation of 90°. The matching geometry of the
pair of disks achieves a virtually linear flow characteristic. The particular
throttle cross section adopted is retained if the control voltage is switched
off. Positive overlapping tight enough to prevent dripping is ensured in the
closed position.
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