| 摘要 |
A flow control device incorporates a flow sensor and a flow control circuit responsive to the output signal of the flow sensor. The flow control circuit operates, via a servo, a flow control valve. The flow sensor incorporates a self-heated thermistor located in the divergent discharge throat of a nozzle in the flow stream. Two unheated thermistors are also located in the fluid, at arbitrary points distant from the nozzle, and incorporated in the control circuit for temperature compensation. The valve controls the flow of fluids therethrough by the distention of an integral seal tube into a cavity formed in an anvil inset into the seal tube. The cavity is conical in shape and the elastomeric seal tube is pressed thereinto by means of a ball. Two orifices issue into the cavity and terminate in the flow channel at the upstream and downstream ends of the valve. With the ball at the inmost limit of its travel, the seal tube blocks the exits of both orifices into the cavity and prevents flow in the channel.
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