GB705007A - Metal cones for cathode ray tubes - Google Patents

Abstract

705,007. Making pipes and tubes ; stamping. RADIO CORPORATION OF AMERICA Feb. 19, 1952 [Feb. 24, 1951], No. 4406/32. Classes 83 (2) and 83 (4). [Also in Group XL (a)] A metal cone for a cathode-ray tube has a circular flanged smaller end for sealing to the tube neck and a rectangular rimmed larger end for sealing to a face plate, the cross-section of the cone tapering gradually and continuously from one end to the other. The flat blank is keyed on to the small end of a rotatable frustum or mandrel and is spun with the aid of external rollers into an oblate circular blank 17, Fig. 4, which has the grain extending in the direction of the minor axis, and is provided with a hole 18 for fitting on to an arbor projecting from the frustum, with holes 19 which register with pins thereon, and with one or more holes 22 to indicate the direction of the grain. The spun frustum 25, Fig. 5, is annealed, coated with a soap lubricant, and stamped into the required shape between a punch 26 and a die 21 mounted on the lower end of a hydraulic or mechanically operated piston 24. A 500 ton stamping mill is required for a blank having a wall thickness of 0.10 inch and consisting of an iron alloy containing 17 per cent of chromium. The punch may carry a cylindrical cutter 27 which in conjunction with the die socket 28 may be used for forming the opening 23, Fig. 4. Alternatively, the opening 23 may be formed by a subsequent operation. Irregularities produced in the surface of the larger flange may be eliminated by the use of a further punch and die, parts of which are cut away to clear the smaller flange and the intermediate portion. This operation may follow a further annealing. A fringe which may be produced on the flange may be eliminated by grinding or by a band saw to which the fringe may be fed progressively by rotating the frustum ; the burr produced by the saw is removed by an abrasive. In another form, the blank 20, Fig. 6, has the apertured lower end closed by a rubber gasket 33, secured by a washer 34, nut 35 and bolt 32, the head of which guides the frustum into the die which is closed by a cover 36 through a rubber sealing ring 37. The frustum is expanded by oil from the pump 39. The die may be modified so that the larger flange may be flat or provided on all, or on only two opposite edges, with upturned flanges.