GB483503A - Improvements in marking metal articles - Google Patents

Abstract

483,503. Electrolytic printing-apparatus. CROSSE & BLACKWELL, Ltd., CLAYTON, W., and SUMNER, C. G. Oct. 28, 1936, No. 29242. [Class 41] Metal articles are treated over localized areas so as to form a pattern by applying thereto a unit comprising an electrode and means to carry a charge of electrolyte, the article constituting the second electrode. The electrolytic treatment may consist in etching, formation of an oxide film by anodic treatment or electrodeposition of metal; in each case it is carried only so far as to produce visible contrast without substantial formation of reliefs or recesses. The invention is particularly applicable to the coding of metal cans, whether empty or full, in rapid sequence ; the apparatus may form an attachment to a can seamer of the double rotary turret type. The marking apparatus may comprise an electrode in the form of a letter or pattern covered by porous material impregnated with the electrolyte ; the porous material may be in the form of an endless band which is passed through a vessel containing electrolyte between successive operations. Alternatively the covering material may comprise porous parts in the form of a pattern separated by non-porous parts or it may consist of porous material partially covered by non-porous material. Another form of apparatus comprises an insulating body with recesses in the form of a pattern to receive a pasty electrolyte, the electrode members being mounted within the recesses. Another apparatus comprises a hollow electrode having an insulated and perforated base through which a pasty electrolyte is forced by a plunger when the apparatus is brought over the work. The apparatus shown comprises an electrolyte container 1 having an insulated base provided with perforations normally obturated by insulating members 4 on a plunger 3 carried by the electrode 2. On engagement of the apparatus with the work the members 4 are raised and allow electrolyte to pass through, the rate of flow being controlled by a valve 5. In a modification the obturating members do not pass through the apertures, the plunger being actuated by external means. For anodic oxidation of tin the electrolyte may consist of sodium carbonate, hydroxide or citrate, ammonium carbonate, Rochelle salt, disodium hydrogen phosphate, potassium dihydrogen phosphate or an equimolecular mixture of the last two, in concentrations of 1 per cent or more. For anodic etching a 5-10 per cent solution of sodium or ammonium chloride or ammonium nitrate is employed. Tartaric or citric acids or their alkali metal salts are preferably added to redissolve precipitated tin compounds. For electrodeposition of copper a bath containing 0À2-0À3 per cent of CuSO4.5H2O in alkaline tartrate or citrate solutions is employed.