Patent GB-838565-A (GB)
Title: Reinforced abrasive products
IPC: B24D5/04
Filed: 1958-01-29
Abstract: 838,565. Abrasive articles. REXALL DRUG CO. Jan. 29, 1958, No. 2942/58. Class 60. An abrasive article comprises bonded abrasive grains and a substance which is associated with a fibrous reinforcing material in fibre form and will ignite at the heat of grinding whereby the reinforcing material will be disintegrated at the grinding surface of the article. When the article is an abrasive wheel, the reinforcing material may be in the form of disc or annular-shaped plies of woven, non- woven or felted construction or of individual separate threads disposed radially, helically, spirally or arbitrarily and consist of metallic or non-metallic, organic or inorganic, natural or synthetic material, such as fine steel wire, nylon yarn or glass fibre yarn, The ignitable substance may be aluminium, magnesium, silicon or zirconium, and a chemical oxidizing agent, such as potassium chlorate, may be used as or with the ignitable substance. When in the form of aluminium wire the ignitable substance may be twisted or entwined with the fine steel wire and the composite strand used as the reinforcing material. The reinforcing material may be in one or more layers such as is shown in Fig. 4, whereiri the strands are laid in three layers 7, 8, 9, on an open network of fine cotton fibres 11, the strands of each layer being at 120 degrees to those in the other layers, each strand being of glass fibre yarn coated with a magnesium powder or other ignitable material adhered to the yarn by adhesive such as starch or phenolic resin or the like. Alternatively, the cotton network may be dispensed with and the strands of one ply wound upon a rotating mandrel and those of the others wound at 120 degrees to the first and to each other. In forming a cut-off wheel, half the volume of the organic resin or rubberbonded abrasive grain is spread in a mould, the reinforcing material with the ignitable substance placed in the bond, and the remainder of the material evenly, distributed over the reinforcing, the wheel then being compacted by pressure and cured' at a suitable temperature. During use, the heat of the grinding operation ignites the ignitable material which causes the reinforcing material 15, Fig. 2a, to disintegrate to a depth of up to 1/32 in. below the surface 16 of the wheel and serves to introduce additional sharp cutting edges to the grinding surface. In the embodiment shown in Fig. 3, the reinforcing material 20 may be formed in layers from one or more continuous helical strips. The wheel may be produced by positioning the reinforcing material in a mould and injecting the abrasive grains and bond into the mould by centrifugal force, or by coating one or both sides of the reinforcing material with abraisive grains, placing a continuous length of the material in a mould, and compacting the wheel under pressure. In wheels comprising a plurality of layers of abrasive-coated sheets, such as described in Specifications 562,851 and 673,334, the reinforcing layers may be embedded within the wheel adjacent the side faces. Cup-shaped wheels and other abrasive products may be similarly reinforced.