Inflatable core tube for molding concrete

Claim 1

AN INFLATABLE TUBE CONSTRUCTION HAVING A LENGTH OF THE ORDER OF ABOUT 30 FEET AND TRANSVERSE DIMENSIONS OF A LOWER ORDER, SAID TUBE CONSTRUCTION BEING USED TO PROVIDE LONG PASSAGEWAYS THROUGH CONCRETE SLABS DURING THE CASTING THEREOF AND REQUIRING A HIGH DEGREE OF PRECISION WITH REGARD TO MAINTAINING AT A CONSTANT VALUE THE TRANSVERSE DIMENSIONS OF THE TUBE THROUGHOUT THE LENGTH THEREOF SO THAT THE PASSAGES THROUGH THE SLABS REMAIN CONSTANT THROUGHOUT THEIR LENGTH, SAID TUBE COMPRISING A TUBULAR BODY OF WOVEN FABRIC WITH THE THREADS RUNNING CIRCUMFERENTIALLY AND LONGITUDINALLY OF THE TUBE, SAID CIRCUMFERENTIAL THREADS BEING OF ELASTIC NYLON, SAID FABRIC HAVING FLEXIBLE MATERIAL BONDED THERETO ON OPPOSITE SIDES THEREOF FOR SEALING THE FABRIC, SAID MATERIAL HAVING THE CHARACTERISTIC OF BEING SUBSTANTIALLY UNAFFECTED BY TEMPERATURES OF THE ORDER OF ABOUT 150*F. AND HIGH HUMIDITY AND BEING RESISTANT TO ABRASION, SAID TUBE HAVING END WALLS WITH AT LEAST ONE END WALL PROVIDED WITH MEANS FOR PERMITTING FLUID FLOW TO PASS BETWEEN THE OUTSIDE AND THE INSIDE OF THE TUBE, SAID TUBE BEING OTHERWISE SEALED SO THAT IT MAY BE EXPANDED BY FLUID PRESSURE WITHIN THE TUBE, THE TRANSVERSE EXPANSION CHARACTERISTIC OF SAID TUBE UNDER FLUID PRESSURE BEING INDEPENDENT OF ANY SIGNIFICANT CHANGE IN LONGITUDINAL DIMENSIONS AND SAID TUBE BEING CHARACTERIZED BY SUBSTANTIALLY UNIFORM ELASTICITY THROUGHOUT THE EFFECTIVE LENGTH THEREOF UNDER CONCRETE CURING CONDITIONS WITH THE FABRIC ELASTICITY DETERMINING SUBSTANTIALLY COMPLETELY THE ELASTICITY OF THE TUBE.