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US 4,135,548 AGranted
Liquid nitrogen level controller
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorDaniel Sears
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Abstract
The liquid nitrogen level in a flask is controlled by the degree of immersion of two sensing coils of copper wire in the liquid nitrogen activating a solid state switching circuit which controls a liquid nitrogen inlet flow valve. Manual override and sensor fault indication is provided.
Claims1
A liquid nitrogen level controller for maintaining the level of LN.sub.2 in a flask within a determined range comprising:
- a. a source of LN.sub.2 ;
- b. means including a LN.sub.2 valve for conducting LN.sub.2 from the said source to the said flask;
- c. a first LN.sub.2 sensor;
- d. a second LN.sub.2 sensor;
- e. means for positioning the said first and second LN.sub.2 sensors in a substantially vertical upper and lower relationship, respectively, within the said flask;
- f. means including a dual NAND Schmitt trigger circuit and a four-bit latch circuit cooperating with the said first and second sensors and the LN.sub.2 valve for opening the said LN.sub.2 valve when the said LN.sub.2 level in the flask is below the said lower sensor and closing the said LN.sub.2 valve when the LN.sub.2 level is above the said upper sensor.
3 more elements
Dependencies are inferred from the claim text.