Preservative impregnation of wood

Claim 1

IN THE IMPREGNATION OF WOOD WITH A NORMALLY LIQUID, OIL-BORNE, PRESERVATIVE COMPOUND SOLUTION, THE METHOD OF REMOVING THE SOLVENT OIL COMPONENT OF SAID SOLUTION FROM THE IMPREGNATED WOOD, AND OF STRIPPING EXCESS PRESERVATIVE COMPOUND FROM THE SURFACE AND OUTER LAYERS OF SAID WOOD TO CLEAN THE SURFACE THEREOF AND TO LEAVE AN EFFECTIVE CONCENTRATION OF PRESERVATIVE DISTRIBUTED SUBSTANTIALLY UNIFORMLY THROUGHOUT THE CROSS SECTION THEREOF, WHICH COMPRISES HEATING THE IMPREGNATED WOOD IN A CLOSED SPACE BY INTRODUCING INTO SAID CLOSED SPACE HOT VAPORS OF SAID SOLVENT OIL AT A TEMPERATURE CORRESPONDING TO THE BOILING POINT OF SAID SOLVENT UNDER THE CONDITIONS IN SAID CLOSED SPACE, CONTINUING THE INTRODUCTION OF SAID HOT VAPORS SO THAT SAID WOOD IS HEATED IN SAID CLOSED SPACE BY THE VAPOR ATMOSPHERE THEREIN TO AN ELEVATED TEMPERATURE BUT NOT ABOVE ABOUT 320* F. SO THAT SAID HEATING IS CARRIED OUT SUBSTANTIALLY BELOW THE TEMPERATURE AT WHICH SAID WOOD WOULD BE DAMAGED BY HEATING, DRAINING FROM SAID WOOD AND THEN FROM SAID CLOSED SPACE CONDENSATE OF SAID SOLVENT OIL AS IT IS FORMED ON THE SURFACE OF THE IMPREGNATED WOOD DURING THE VAPOR HEATING OF SAID WOOD AND THEREBY CARRYING OFF EXCESS PRESERVATING COMPOUND AS AN EXTRACT WITH SAID CONDENSATE FROM THE SURFACE AND OUTER LAYERS OF THE HEATED WOOD DISCONTINUING THE INTRODUCTION OF SAID HOT VAPORS AND CREATING A VACUUM IN SAID CLOSED SPACE WHEREBY THE SOLVENT OIL COMPONENT OF SAID SOLUTION IS VAPORIZED FROM SAID HEATED WOOD AND RECOVERED FROM SAID CLOSED SPACE, AND ALTERNATELY REPEATING SAID VAPOR HEATING AND VACUUM TREATMENTS OF SAID IMPREGNATED WOOD UNTIL THE WOOD IS SUBSTANTIALLY FREE OF SAID SOLVENT OIL.