Electrically heated vacuum furnace

Claim 1

AN ELECTRICALLY HEATED VACUUM FURNACE PARTICULARLY FOR FUSING DENTAL CERAMICS AND COMPRISING IN COMBINATION, A BASE HOUSING, AN INVERTED CUP-SHAPED FURNACE CHAMBER SUPPORTED ABOVE SAID BASE WITH THE ENTRANCE FACING SAID BASE, A VACUUM PUMP CONNECTED BY CONDUIT MEANS TO THE INTERIOR OF SAID FURNACE CHAMBER, THE SIDES AND THE TOP OF THE FURNACE CHAMBER BEING INSULATED FOR HEAT RETENTION, A CHARGE ELEVATOR MOVABLE IN OPPOSITE VERTICAL DIRECTIONS ABOVE SAID BASE HOUSING TOWARD AND FROM THE ENTRANCE IN THE BOTTOM OF THE FURNACE CHAMBER AND PROVIDED AT ITS UPPER END WITH A CHARGE CARRYING HORIZONTAL TABLE ADAPTED TO FIT AGAINST THE ENTRANCE OF THE FURNACE VESSEL TO SEAL THE ENTRANCE OPENING TIGHTLY WHEN THE TABLE IS LIFTED INTO ENGAGEMENT WITH THE SAID APERTURE, THE LOWEREND OF SAID CHARGE ELEVATOR HAVING A PISTON SLIDABLY MOVABLE WITHIN A VERTICAL CYLINDER FOR MOVEMENT IN OPPOSITE DIRECTIONS, AN AIR CONDUTI CONNECTED TO THE LOWER END OF THE SAID CYLINDER, A BALL CHECK VALVE MOUNTED ON SAID CONDUIT, SAID CONDUIT HAVING BETWEEN THIS VALVE AND THE SAID CYLINDER A BLEEDER HOLE OF A DIAMETER SUBSTANTIALLY LESS THAN THAT OF SAID CONDUIT, THE OTHER END OF SAID AIR CONDUIT BEING CONNECTED TO THE PRESSURE SIDE OF THE SAID VACUUM PUMP, A CONDUTI EXTENDING FROM SAID AIR CONDUIT TO RECEIVE AIR UNDER PRESSURE THEREFROM AND HAVING A VALVE SEAT AT THE OUTER END THEREOF, ANOTHE BRANCE CONDUIT EXTENDING FROM SAID VACUUM CONDUIT INTERCONNECTING THE VACUUM PUMP AND THE SAID FURNACE VESSEL AND HAVING A VALVE SEAT AT THE FREE END THEREOF, AND VALVE MEANS OPERABLE RELATIVE TO SAID VALVE SAEATS CUSSESSIVELY FIRST TO CLOSE SAID VALVE SEAT IN SAID FIRST-MENTIONED BRANCH CONDUIT TO CAUSE AIR PRESSURE TO RAISE SAID PISTON AND CHARGE-CARRYING TABLE AGAINST SAID ENTRANCE OF SAID FURNANCE TO CLOSE IT AND SAID VALVE MEANS THEN BEING MOVABLE TO CLOSE SAID VALVE SEAT IN SAID SECOND MENTIONED BRANCH CONDUIT TO CLOSE SAID VACUUM CONDUIT TO SAID FURNACE CHAMBER TO MAINTAIN SAID TABLE AGAINST SAID FURNACE ENTRANCE WHIE SAID AIR PRESSURE IS RELEASED FROM SAID PISTON.