Dry investment mold and method

Claim 1

IN THE METHOD OF MANUFACTURING AN INVESTMENT MOLD FOR PRECISION CASTING WHEREIN A SUITABLY SHAPED, EXPENDABLE PATTERN OF LOW MELTING POINT MATERIAL IS COVERED WITH A THIN SHELL OF REFRACTORY MATERIAL BY DIP COATING THE PATTERN UP TO TWO TIMES WITH A CERAMIC SLURRY AND STUCCOING AFTER EACH DIP COATING, AND THE COATED PATTERN THEN DISPOSED WITHIN A FLASK AND A REFRACTORY INVESTMENT MATERIAL PACKED INTO SAID FLASK AROUND SAID COATED PATTERN TO SUPPORT SAID COATED PATTERN DURING AND AFTER REMOVAL OF THE EXPENDABLE PATTERN MATERIAL AND FIRING OF THE MOLD, THE IMPROVEMENT COMPRISING PACKING INTO THE FLASK AND AROUND THE COATED PATTERN, A DRY INVESTMENT COMPOSITION CONSISTING OF FROM 90 TO 99 PERCENT BY WEIGHT OF AT LEAST ONE REFRACTORY MATERIAL SELECTED FROM THE GROUP CONSISTING OF SAND, FIRE BRICK, AND ALUMINA, FROM 0.5 TO 6 PERCENT BY WEIGHT OF AT LEAST ONE LOW TEMPERATURE BONDING AGENT SELECTED FROM THE GROUP CONSISTING OF SODIUM CHLORIDE, BORAX, LEAD BORATE GLASS, SODIUM METASILICATE, AND AMMONIUM PHOSPHATE, AND FROM 0.5 TO 8 PERCENT BY WEIGHT OF AT LEAST ONE HIGH TEMPERATURE BONDING AGENT SELECTED FROM THE GROUP CONSISTING OF FELDSPAR, SODIUM ALUMINATE, LITHIUM CARBONATE, AND PETALITE, AND THEN BURNING OUT THE EXPENDABLE PATTERN AND FIRING THE MOLD TO EFFECT BONDING OF THE REFRACTORY MATERIAL.