Method and apparatus for producing dielectric layer on the surface of an aluminum foil

Claim 1

A PROCESS FOR FORMING A DIELECTRIC LAYER ON THE SURFACE OF AN ALUMINUM FOIL TO BE USED IN AN ELECTROLYTIC CAPACITOR COMPRISING THE STEPS OF FEEDING A WEB OF THE ALUMINUM FOIL THROUGH AN ELECTROLYTIC BATH IN WHICH THE SURFACE OF THE ALUMINUM FOIL IS SUBJECTED TO ANODIZATION BY A FLOW OF CURRENT TO FORM AN OXIDE LAYER ON THE SURFACE OF THE ALUMINUM FOIL, FROM WHICH BATH VAPORS ARE EVOLVED WHICH TEND TO IMPART UNDESIRABLE INITIAL OXIDATION TO THE FOIL BEFORE IT ENTERS THE BATH AND IN THE UPPER REGION OF WHICH ELECTROLYTIC BATH GAS BUBBLES TEND TO CONCENTRATE JUST BELOW THE SURFACE, THE WEB BEING INTRODUCED INTO THE ELECTROLYTIC BATH FROM ABOUT, ISOLATING THAT PORTION OF THE OIL ABOVE THE ELECTROLYTIC BATH FROM PREMATURE OXIDATION CAUSED BY OXIDIZING VAPORS, INCLUDING VAPORS EVOLVED FROM THE ELECTROLYTIC BATH, ISOLATING A LENGTH OF THE ALUMINUM FOIL BENEATH THE SURFACE OF THE BATH FROM PREMATURE OXIDATION AND THE EFFECT OF THE FLOW OF CURRENT UNTIL IT HAS DESCENDED BENEATH THE SURFACE OF THE ELECTROLTYIC BATH AND BELOW THE CONCENTRATION OF GAS BUBBLES NEAR THE SURFACE OF THE ELECTROLYTIC BATH TO A DEPTH AND TO A REGION WITIN THE ELECTROLYTIC BATH AT WHICH THE FOIL IS SURROUNDED BY FULL STRENGTH ELECTROLYTE, AND SUBJECTING THE ALUMINUM FOIL WHEN IT REACHES SAID DEPTH AND SAID REGION AT WHICH IT IS SURROUNDED BY AND IN THE PRESENCE ONLY OF FULL STRENGTH ELECTROLYTE, AND NOT BEFOREHAND, TO THE FULL CURRENT FLOW IN UNDILUTE ELECTROLYTE, SO THAT THE INITIAL ANODIZATION OF THE FOIL IS BY FULL CURRENT FLOW IN FULL STRENGTH ELECTROLYTE.