Patent GB-645183-A (GB)
Title: Method and apparatus for electro-plating
IPC: C25D7/10
Filed: 1946-10-10
Abstract: 645,183. Work support for electrolytic deposition of metals. CLEVELAND GRAPHITE BRONZE CO. Oct. 10, 1946, No. 30268. Convention date, June 29. [Class 41] A uniform layer of metal is electrodeposited upon a concave surface of a semi-cylindrical article such as a bearing surface; by placing the article in a closed box mounted vertically in an electrolyte and having a relatively narrow slot disposed centrally and vertically of the side facing the concave surface of the article, the slot being provided with inwardly extending flanges at the inner edge thereof. As shown, a box 28 of insulating material for instance of hard rubber has a slot 6 relatively narrow compared to its length, disposed centrally in the side which faces the concave surface of the article 1, e.g. a stack of bearing shells when placed: in position within the box and centrally with respect to the slot. The slot is bounded by flanges 20 (see Fig. 4), extending inwardly towards the article 1. The width A of the slot the internal depth B of the flange and the width C of the flange are critically related to obtain a deposit in which the variation in thickness from side to side is not more than 5 per cent. For normal voltage, viz. 6-12 volts, the dimensions of the flanges in terms of percentages of the bearing shell diameters are A=25-38 per cent, B=3-4 per cent, C=6-10 per cent. The slot 6 terminates at a distance just short of the end of the stack or bottom of the box (see Fig. 5), so as to leave a slight ledge 18 to prevent " end effect '' in the electrodeposition process. With the above values of A, B and C, the height of the ledge is 2-8 per cent of the shell diameter. At the top of the box 28 the slot 6 is flush with the upper edge 9, the article 1 or an insulating plate may rest on the top of the article and extend through the slot. To prevent a heavier deposit on the lower 4¥ inches of the shell 1 a shadow is inserted in that portion of the slot 6, and may be in the form of a right-angled triangle on either side the slot 6, causing the slot to taper so as to restrict the area of the slot in the lower portion thereof by approximately 10 per cent. The shells 1 are maintained in the stacked relationship by means of a contact brought into position against a blank half shell mounted on the top of the stack and pressed down by spring 55 and current is fed to the contact plate by conductor 27. The box may be suspended in the bath by a hook 30. A removable cover 24 is held in place by a ring 29 engaging an extending portion at the bottom and by a spring 40 and releasing cam 31 at the top. A thief electrode or robber element 32 located between the shells 1 and the cover 24 prevents deposition of metal on the convex surface of the shells. The metal may be deposited at a current density of 20 amps./sq. foot, voltage 6-8 volts from a bath consisting of the following, given in grams/litre. Lead 100 to 110, hydrofluoric acid 40 to 50, total tin 8 to 12, resorcinal 1 to 5 copper, in the form of soluble salts, 1 to 3, and gelatine 0.1 minimum. The anode may be composed of 10 per cent tin with remainder lead, the anode bars being placed around the periphery of the plating bath. Specification 627,294 is referred to.