Patent GB-677106-A (GB)
Title: Reinforced abrasive wheels and a method of making the same
IPC: B24D18/00
Filed: 1950-04-27
Abstract: 677,106. Grinding wheels. BAY STATE ABRASIVE PRODUCTS CO. April 27, 1950 [May 12, 1949], No. 10417/50. Class 60. An abrasive wheel comprises abrasive grains' coated and bonded with natural or synthetic resin or rubber and one or more cords which are wound about the axis from the central portion to the periphery and will disintegrate under grinding action, the convolutions of the cord or cords being surrounded and spaced from one another by the grains and bond whereby the wheel is strengthened against fracture and has an open or porous structure at the grinding surface. The wheel may be made by fixing the grains and the bond on to the cord or cords, winding the latter in spiral form on a bobbin, and pressing the product. The grains may be fixed directly to the cord by the bond, or they may be coated initially with an adhesive, such as a resin plasticizing agent (e.g. furfural or cresylic acid), and then provided with a coating of the bond, in the form of a dry resin powder (e.g. the vinyl, glycerol phthalic anhydride, urea aldehyde, melamine aldehyde, or aniline aldehyde resins, or, preferably; the phenol-formaldehyde condensation product in the partially-converted B-stage). Alternatively, the grains may be coated by mixing them with the B-stage resin and then crushing the mass to provide individually coated grains. The coated grains may be secured to the cord by coating the latter with an adhesive such as furfural, acetone and alcohol, or cresylic acid. In another form, the abrasive grains may be coated with one or more coats of natural or synthetic rubber; and cemented to the cord by a phenolformaldehyde resin. The cord may be a monofilament, a single strand of twisted fibres, or two or more twisted strands, and may consist of cotton, linen, wool, nylon, or rayon. One or more of the treated cords are wound on a bobbin between confining flanges in spiral form, either in orderly or haphazard fashion; for a wide wheel, a plurality of cords may be wound spirally and in parallelism, or a single cord may be wound helically back and forth along the bobbin. The confining flanges of the bobbin may be inclined so as to produce a wheel which is of greater thickness at the periphery than at the centre. After winding on the bobbin, the wheel is pressed axially to its final form and heated. One or more additional cords may be wound with an abrasive coated cord, but the additional cords are not coated with the abrasive although they may be coated with the bond. A laminated wheel may be formed by pressing together, with one or more intervening layers of fabric, two discs each formed as described above. In a modification, the abrasive grains are provided with one or more coatings of a vulcanizable rubber compound and applied to a cord which has been treated with an adhesive such as the liquid A-stage phenol formaldehyde resin. In the arrangement shown in the drawing, three cords 16 are led from bobbins 24 over rollers 25 and are then coated with an adhesive by passage through one or more tanks 26; the thickness of the coating on the cords is determined by an adjustable roller 29. The cords then pass beneath a spout 34 where they pass through a stream of the coated abrasive grains, and any grains which do not adhere to the coated core fall into a lower spout 37 and are transferred therefrom to the upper spout 34 by a rotating vaned cylinder 35. From the spout 34 the cords are wound on to a bobbin 19 which is rotated by a motor 38.