Apparatus for the corona discharge treatment of thermoplastic films wherein the discharge electrode has a plurality of knife edges

Claim 1

IN APPARATUS FOR IMPROVING THE ADHESION CHARACTERISTICS OF POLYOLEFIN FILM THROUGH CORONA DISCHARGE TREATMENT, INCLUDING ELECTRODE MEANS FOR GENERATING A CORONA DISCHARGE ACROSS A GAP AND UPON THE FILM BEING TREATED, MEANS FOR SUPPLYING HIGH FREQUENCY ALTERNATING ELECTRIC CURRENT TO SAID ELECTRODE MEANS, A GROUNDED BACK-UP MEMBER AND A DIELECTRIC LAYER INTERPOSED BETWEEN SAID ELECTRODE MEANS AND SAID BACK-UP MEMBER, THE IMPROVEMENT WHICH COMPRISES ELECTRODE MEANS CONSTITUTED BY AT LEAST ONE RIGID ROD-LIKE MEMBER EXTENDING TRANSVERSELY ACROSS THE WIDTH OF THE FILM BEING TREATED, SAID ELECTRODE MEANS INCLUDING A CORONA DISCHARGE SURFACE CONSTITUTED BY A PLURALITY OF UNIFORMLY AND CLOSELY SPACED PARALLEL KNIFE EDGES DISPOSED TRANSVERSELY WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID ROD-LIKE MEMBER AND EXTENDING INTO CORONA DISCHARGING SPATIAL RELATIONSHIP WITH RESPECT TO SAID BACK-UP MEMBER, THE MAXIMUM DISTANCE BETWEEN ADJACENT KNIFE EDGES BEING NO GREATER THAN THE GAP OVER WHICH THE CORONA DISCHARGE TRAVELS, THE WIDTH OF THE GAP BEING ON THE ORDER OF 0.060 OF AN INCH AND THE NUMBER OF KNIFE EDGES ON SAID RIGID ROD-LIKE MEMBER BEING ON THE ORDER OF 16 TO 18 EDGES PER INCH.