GB447909A - Improvements in electrolytic etching machines - Google Patents

Abstract

447,909. Electrolytic etching machines. BRITISH INSULATED CABLES, Ltd., Prescot, Lancashire, S. D. SYNDICATE, Ltd., 31, Earl Street, London, HARTEL, E. G., The Hollies, The Drive, Wembley Park, Middlesex, and BRISLEE, F. J., Wayside, Rupert Road, Huyton, and BLACKBURN, R., Deans House Hotel, Prescot, both in Lancashire. Nov. 24, 1934, No. 33843. [Class 41] The cathode consists of a curved grid or open structure through which electrolyte is propelled to or from the anode, the centre of the cathode lying nearer to the anode than outlying parts ; in this way excessive etching at the edges of the anode is avoided. In the apparatus shown, the plate 3 to be etched rests on rubber-faced ledges on carrier strips 7 extending the width of the tank, these being adjustably mounted on bars 5 to accommodate different sizes of plate. The strips 7 which extend downwards to near the cathode also serve to limit the etching of the edges. Connection to the anode is made by a recessed disc 10 resting on it, the disc having an insulating casing 11. The cathode consists of a perforated cylinder 13 mounted on a shaft 4 and in communication with enlarged perforated insulating drums 21. Electrolyte is drawn into the cathode and discharged from the drums by centrifugal action. Stationary supplementary cathodes may be mounted on either side of the cvlinder 13 for further control of the current distribution. In a modification, the cylindrical cathode is built of metal rings interleaved with rings of insulating material, the metal rings decreasing in diameter from the centre towards the ends ; by this means distance between anode and cathode increases from the centre outwards in two directions at right angles. In this form the drums 21 are dispensed with and the centrifugal flow is outwards through the cathode. In another modification, the cathode consists of a stationary grid of semicircular bars with their convex sides presented to the anode ; the bars are of equal diameter, but are spaced further apart at the ends, the distribution of current density in two directions being thereby controlled. An independent rotating agitator is mounted beneath the cathode. All metal parts in contact with the electrolyte should be of the same metal as that being etched.