Pressure process for impregnating wood

Claim 1

IN A PROCESS FOR IMPREGNATING UNSEASONED WOOD IN WHICH THE WOOD IS FIRST DRIED BY HEATING WITH STREAM FOLLOWED BY DRAWING A VACUUM ON THE THUS TREATED WOOD AND THEN IMPREGNATED WITH A LIQUID IMPREGNANT THE METHOD WHEREBY UNSEASONED PINE HAVING A SPECIFIC GRAVITY LESS THAN 0.45 MAY BE EFFECTIVELY IMPREGNATED WHICH COMPRISES; IN THE IMPREGNATING STEP CONFINING THE DRIED, UNSEASONED WOOD AND IMPREGNATING LIQUID UNDER FLUID PRESSURE IN A CLOSED PRESSURE VESSEL AND PUMPING ADDITIONAL IMPREGNATING LIQUID INTO THE SO-CLOSED VESSEL AT A SUBSTANTIALLY CONSTANT RATE OVER SUBSTANTIALLY THE ENTIRE PERIOD OF THE IMPREGNATION, SAID RATE BEING LESS THAN 3-4.5 POUNDS OF IMPREGNATING LIQUID PER CUBIC FOOT OF WOOD PER HOUR WHEREBY EACH INCREMENT OF IMPREGNATING LIQUID PUMPED INTO THE FILLED TREATING VESSEL NECESSARILY IS FORCED INTO THE WOOD AND THE PRESSURE IS A FUNCTION OF THE RESISTANCE THE WOOD OFFERS TO THE FLOW OF IMPREGNATING LIQUID INTO ITS INTERIOR.