GB840781A - Improvements in or relating to replaceable facings for surfacing tools and to methods of forming such facings - Google Patents

Abstract

840,781. Grinding tools. AMERICAN OPTICAL CO. Nov. 22, 1957 [Jan. 18, 1957], No. 36545/57. Class 60. An abrading tool for surfacing a lens blank, to a desired shape, comprises a replaceable facing 13, Fig. 2, of relatively thin foraminous material which is contoured into engagement with the body 11 of the tool and provided with means either forming part of the sheet or by a separate clamp for retaining it in position. The facing, which may be of soft galvanised steel, bronze or nickel wire mesh, is initially sprayed on one side with a thin layer of slowsetting waterproof adhesive to which, before it has set, short lengths of synthetic or natural fibrous material 15, Fig. 4, such as rayon or cotton are applied ; this material is then subjected to electrostatic or like treatment to cause the major portions of the fibres to stand away from the adhesive coating. The facing 13 is secured to body 11 of the tool by applying a second adhesive coating 16 to either the facing 13 or the tool ; the latter may be of cast-iron, sintered metal or plastic and its surface may be convex or concave of substantially the desired curvature to be formed on the blank. In another embodiment, the facing is coated with a heatsensitive adhesive, such as a mixture of 75% rosin and 25% hydrogenated methyl ester or rosin, and bonded to the tool which is heated sufficiently to soften the adhesive ; alternatively, a pressure-sensitive adhesive may be used. In a further embodiment, the facing is cut large enough to overlap the sides of the tool and retained in position by a spring-type clamp 18, Fig. 6, or other suitable clamping means. In use, the tool is mounted on an oscillating arm 19, Fig. 7, and the lens blank 20, which is adhesively-attached to a holder 20a, describes, by means of alignment-retaining means 21 and a crank spindle 22, a path of movement relative to that of the tool so that a scrubbing action takes place on the surface of the blank while an abrasive slurry 23 is applied to the facing of the tool. A plastic polishing pad of substantially the same thickness as the wire mesh facing may be used to replace the latter during polishing of the lens blank.