Level control for cryogenic liquid

Claim 1

A LIQUID LEVEL CONTROL FOR USE WITH A CRYOGENIC LIQUID VESSEL COMPRISING, IN COMBINATION, A FIRST SENSING UNIT HAVING A FIRST BELLOWS AND A FIRST TUBE SEALINGLY COUPLED THERETO AND ENCLOSING A FIRST VOLUME OF GAS, SAID FIRST TUBE HAVING AND END SITUATED IN SAID VESSEL AT THE LOWER LEVEL LIMIT THEREIN AN ELECTRIC SWITCH OPERATED BY EXPANSION OF SAID FIRST BELLOWS AND BEING CONNECTED TO INITIATE THE FLOW OF ADDITIONAL CRYOGENIC LIQUID TO SAID VESSEL, A SECOND SENSING UNIT HAVING A SECOND BELLOWS AND A SECOND TUBE SEALINGLY CONNECTED THERETO AND ENCLOSING A SECOND VOLUME OF GAS, SAID SECOND TUBE HAVING AN END SITUATED IN SAID VESSEL AT THE UPPER LEVEL LIMIT THEREOF, MENAS OPERATIVELY COUPLING SAID SECOND BELLOWS TO SAID SWITCH TO TERMINATE THE FLOW OF CRYOGENIC LIQUID TO SAID VESSEL WHEN SAID SECOND BELLOW CONTRACTS, A THIRD BELLOWS COUPLED TO SAID FIRST TUBE THROUGH A FLOW RESTRICTION CAUSING EXPANSION OF SAID THIRD BELLOWS TO BE DELAYED RELATIVE TO EXPANSION OF SAID FIST BELLOWS WHEREBY SAID THIRD BELLOW DOES NOT EXPAND IF SAID END OF SAID FIRST TUBE IS PROMPTLY RE-COOLED BY SAID FLOW OF ADDITIONAL LIQUID TO SAID VESSEL, AND MEANS SENSING EXPANSION OF SAID THIRD BELLOWS TO DETECT A CONDITION WHEREIN SAID LIQUID LEVEL IS NOT PROMPTLY RAISED ABOVE SAID LOWER LIMIT.