Patent GB-451001-A (GB)
Title: Improvements in electrolytic etching machines
IPC: C25F7/00
Filed: 1935-06-11
Abstract: 451,001. Electrolytic etching machines. BRITISH INSULATED CABLES, Ltd., Prescot, Lancashire, S.D. SYNDICATE, Ltd., 31, Earl Street, Finsbury, London, HARTEL, E. G., The Hollies, The Drive, Wembley Park, Middlesex, and BRISLEE, F. J., Wayside, Rupert Road, Huyton, and BLACKBURN, R., Deanes House Hotel, Prescot, both in Lancashire. June 11, 1935, No. 16787. [Class 41] A zinc or other metal plate to be etched is mounted as anode parallel to a flat cathode the effective part of which is smaller both in width and length than the anode byapproximately the same distance on all sides; by this means excessive etching at the edges of the plate is avoided. A large cathode may be employed, its effective area being limited by barriers which are adjustable for use with various sizes of anode. In the apparatus shown, the cathode consists of a perforated plate 38. Over this at one corner are mounted two insulating barriers at right angles, one of which is shown in section at 41. These are provided with rubber-faced ledges 43 on which two adjacent sides of the anode 3 rest. The barriers 41 are inclined in section so as to mask the cathode to an outline within that of the anode. A third edge of the anode rests on a ledge on a barrier 45 slidably mounted on a rod 46. The fourth barrier is constituted by a plate 49 sliding at one end in a groove in the barrier 45 and resting at the other end on a ledge in one of the fixed barriers. This is connected by transverse members 51 to a plate 50 of somewhat smaller width provided with a rubber cushion 52. By bringing the plate 50 into contact with the fourth edge of the anode the corresponding edge of the cathode is masked by the plate 49 to the required extent. The plate 49 is connected to a rubber sheet anchored at 54 hanging in a loop 53 to form a shield to prevent current flow to the back of the anode. The electrodes are mounted at a slight inclination to facilitate escape of gas. Electrolyte is drawn into a perforated cylinder 39 mounted beneath the cathode and ejected by centrifugal action from enlarged perforated ends 23 mounted in side pockets. Metal sludge from the anode collects beneath a perforated screen 40. Connection to the anode is made by a recessed disc 10 resting on it. In a modification, two parallel sliding barriers are provided. In another modification, the barrier corresponding to the plate 49, is constituted by an endless rubber band which may be moved over end-wheels, part of the band extending the full width of the cathode and the remainder over the edges only. In this form no electrolyte agitator is provided but a perforated insulating plate is mounted over the cathode and is reciprocated by hand to remove deposits. All metal parts exposed to the electrolyte, including the cathode, should be of the same metal as that being etched. According to the Provisional Specification the electrolyte may be propelled across the electrodes by a paddle-wheel at one end of the cell working on a horizontal axis above the surface of the liquid. Oscillatory movement of the electrolyte may be produced by rocking the cell or by displacers mounted at the ends of a rocking beam, and working vertically in wells at opposite ends of the cell.