Shell mold structures

Claim 1

IN A DESTRUCTIBLE SHELL MOLD, A SHELL-SHAPED STRUCTURE HAVING A THICKNESS OF AT MOST ABOUT 1/4 INCH AND AN INNER CAVITY SURFACE OF A SHAPE CORRESPONDING TO AN OBJECT TO BE CAST, COMPRISING AS SHELL INGREDIENTS A PREDOMINANT AMOUNT OF REFRACTORY PARTICLE MATERIAL AND AN INNER CAVITY SURFACE FORMING THE MOLD CAVITY HAVING REFRACTORY MATERIAL OF SUFFICIENTLY FINE PARTICLE SIZE TO PROVIDE A RELATIVELY SMOOTH CAVITY SURFACE, AT LEAST THE OUTER SHELL LAYER OF SAID SHELL MOLD CONTAINING AS AN INORGANIC RAISED-TEMPERATURE BINDER AN AMMONIUM PHOSPHATE IN THE FORM OF SMALL PARTICLES -150 MESH IN SIZE WHICH CONSTITUTE FROM .5% TO 5% BY WEIGHT OF THE SHELL INGREDIENTS AND DECOMPOSES AT INTERMEDIATELY HIGH TEMPERATURE BETWEEN ABOUT 150* AND 600*C. TO FORM PHOSPHORIC ACID AND WHICH AMMONIUM PHOSPHATE IS PRESENT IN AN AMOUNT TO PROVIDE AT THE DECOMPOSITION OF THE AMMONIUM PHOSPHATE A SUFFICIENT AMOUNT OF PHOSPHORIC ACID TO REACT WITH AND BIND THE REFRACTORY PARTICLES TOGETHER AT SAID INTERMEDIATE TEMPERATURES, SUBSTANTIALLY ALL OTHER SHELL LAYERS OF SAID SHELL MOLD ALSO CONTAINING AN INORGANIC RAISED TEMPERATURE BINDER CONSTITUTING .5* TO 5% OF THE SOLID SHELL INGREDIENTS THEREOF AND BEING EFFECTIVE AND SUFFICIENT IN AMOUNT TO BIND THE REFRACTORY PARTICLES OF SAID SHELL LAYERS AFTER HEATING TO A RAISED TEMPERATURE OF AT MOST 1200*C., AT LEAST THE INNER LAYER OF SAID SHELL MOLD BEING FREE OF PHOSPHORUS AND PHOSPHORUS COMPOUNDS, AND AN ORGANIC RESINOUS BINDER FOR THE REFRACTORY PARTICLES AND THE INORGANIC BINDER INGREDIENTS, WHICH ORGANIC RESINOUS BINDER HAS THE PROPERTY OF CAUSING THE REFRACTORY PARTICLES TO ADHERE TO A FROZEN MERCURY PATTERN AND OF BINDING THE REFRACTORY PARTICLES AND THE INORGANIC BINDER INFREDIENTS TOGETHER INTO A SELF-SUPPORTING SHELL MOLD AT TEMPERATURE RANGING FROM BELOW THE FREEZING TEMPERATURE OF MERCURY UP TO AT LEAST THE TEMPERATURE AT WHICH THE AMMONIUM PHOSPHATE PARTICLES DECOMPOSE TO FORM PHOSPHORIC ACID, SAID ORGANIC RESINOUS BINDER CONSTITUTING .25% TO 5% BY WEIGHT OF THE STRUCTURE INGREDIENTS AND BEING PRESENT IN AN AMOUNT SUFFICIENT TO BIND THE REFRACTORY AND AMMONIUM PHOSPHATE PARTICLES TOGETHER OVER SAID TEMPERATURE RANGE AND BEING CAPABLE OF BEING MODIFIED AT TEMPERATURES ABOVE THAT AT WHICH PHOSPHORIC ACID IS FORMED TO PROVIDE VAPORS WHICH EXUDE THROUGH THE SHELL MOLD STRUCTURE TO PROVIDE A POROUS MOLD.