Method of uniformly coating a tubular lamp envelope with phosphor

Abstract

Abstract THE PHOSPHOR PAINT IS FLUSHED THROUGH THE VERTICALLYPOSITIONED ENVELOPE AND THE VAPORIZED SOLVENT IS REMOVED FROM THE ENVELOPE OIN SUCH A MANNER THAT SETTING AND DRYING OF THE COATING IS ACCOMPLISHED AT A RATE WHICH DEPOSITS A LAYER OF PHOSPHOR PARTICLES ON THE INNER SURFACE OF THE ENVELOPE THAT IS MORE UNIFORM THAN THAT ACHIEVED WITH CONVENTIONAL COATING METHODS. IN THE CASE OF A WATER-BASE PHOSPJHOR PAINT, REMOVAL OF THE WATER VAPOR IS ACHIEVED BY PASSING HEATED AIR (APPROXIMATELY 155*F.) DOWNWARDLY THROUGH THE COATED ENVELOPE AND VARYING THE VELOCITY OF THE AIR FLOW (WITHIN A RANGE OF 250 TO 650 FEET PER MINUTE) DURING THE DRYING OPERATION. WITH PHOSPHOR PAINTS HAVING AN ORGANIC SOLVENT (XYLENE OR BUTYL ACETATE), THE SOLVENT VAPORS ARE FIRST FLUSHED OUT WITH AIR THROUGH THE TOP OF THE COATED ENVELOPE BY CLOSING THE LOWER END OF THE ENVELOPE, THE INJECTION OF AR IS THEN STOPPED AND THE LOWER END OF THE ENVELOPE IS OPENED TO ALLOW THE HEAVIER-THAN-AIR SOLVENT VAPORS TO FLOW OUT OF THE ENVELOPE THROUGH ITS LOWER END, AND AIR AT A LOW VELOCITY (150 TO 200 FEET PER MINUTE) IS THEN PASSED THROUGH THE ENVELOPE TO COMPLETE THE DRYING CYCLE. THE COATED BUBLS IN EACH CASE ARE LEHRED IN AIR AT A TEMPERATURE OF FROM ABOUT 1200* TO 1250*F. FOR ABOUT 2 MINUTES TO VOLATILIZE AND REMOVE THE ORGANIC BINDER FROM THE PHOSPHOR LAYER.

Inventors

• 👤 R Repsher

Bibliographic Details