Method and means for continuous control of etching rate

Claim 1

IN THE ETCHING OF METAL SIMULTANEOUSLY FROM A SUCCESSION OF ARTICLES, ARRANGED IN A CONTINUOUS SERIES THROUGH THE ETCHING ZONE OF AN ETCHER, THE IMPROVED STEPS COMPRISING: SETTING THE ARTICLES IN MOVEMENT AT A GIVEN RATE OF SPEED OVER A PATH IN THE ETCHER LEADING THROUGH AND PAST THE ETCHING ZONE; FEEDING A PORTION OF A CONTINUOUS CONTROL ELEMENT OF METAL INTO A PATH OF EXPOSURE TO THE ETCHANT OF THE ETCHER WHEREBY, UNDER SUSTAINED ATTACK OF THE ETCHANT, THE ETCHANT DISSOLVES THE METAL OF THE CONTROL ELEMENT UNTIL A POINT OF DISCONTINUITY IS REACHED AS A MEASURE OF THE EACH RATE STRENGTH OF THE ETCHANT; SENSING THE POINT OF DISCONTINUITY IN COMPARISION WITH THE POINT AT WHICH THE DISCONTINUITY IS ATTAINED CORRESPONDING TO A REFERENCE RATE OF ATTACK; AND AUTOMATICALLY ADJUSTING THE MOVEMENT OF THE ARTICLES IN A SPEED DECREASING DIRECTION IN RESPONSE TO SENSING THAT THE POINT OF DISCONTINUITY IS BEING REACHED AT A POINT CORRESPONDING TO A RATE OF ATTACK SLOWER THAN THE REFERENCE VALUE.