Apparatus for heating undrawn yarn for drawing

Claim 1

IN AN APPARATUS FOR CONTINUOUSLY DRAWING MULTIFILAMENT YARN, OF CRYSTALLIZABLE SYNTHETIC LINEAR POLYMER, WHICH INCLUDES FEED ROLLS FOR SUPPLYING THE YARN AT A UNIFORM RATE, MEANS FOR HEATING THE YARN TO A DRAWING TERMPERATURE ABOVE THE CRYSTALLINE SECOND ORDER TRANSITION TEMPERATURE OF THE POLYMER, DRAW ROLLS FOR APPLYING DRAWING TENSION TO THE HEATED YARN, AND SNUBBING MEANS LOCATED BETWEEN SAID FEED AND DRAW ROLLS FOR MAINTAINING THE YARN TO THE DRAWING TEMPERATURE IN A PERIOD OF 0.06 TO 3 SECONDS SO THAT THE YARN WILLDRAW EVENLY TO HAVE UNIFORM DYEING PROPERTIES WHICH COMPRISES, A PAIR OF FREELY-ROTATING SMALL IDLER ROLLERS MOUNTED TO PASS THE YARN BACK AND FORTH OVER THE ROLLS FOR SEVERAL WRAPS, A HEATING SHOE EXTENDING BETWEEN THE IDLER ROLLERS, THE SHOE HAVING SLIGHTLY CONVEX SURFACES TERMINATING TANGENTIALLY TO THE ROLLER SUFACES FOR GUIDING THE YARN SMOOTHLY FROM ROLLER TO ROLLER, SAID SHOE SURFACES BEING MATTE FINISHED WITH AN AVERAGE SURFACE DEVIATION OF AT LEAST 25 MICROINCHES TO PROVIDE A TOTAL FRICTIONAL DRAG ON THE YARN OF 10% TO 40% OF SAID DRAWING TENSION, AND HEATING MEANS FOR MAINTAINING THE SHOE SURFACES AND ROLLERS AT SAID DRAWING TEMPERATURE.