GB1070234A - Improved method and apparatus for abrading - Google Patents

Abstract

1,070,234. Blasting. ABRASIVE DEVELOPMENTS Ltd. Feb. 25, 1964 [Feb. 27, 1963; Nov. 15, 1963], Nos. 11815/64 and 11816/64. Divided out of 1,070,233. Heading B3D. A surface on a workpiece is abraded by forming an enclosure with the surface as a wall thereof, applying suction to the enclosure, inducing the flow of primary air into the enclosure by the removal of the air in the enclosure by suction while restricting the entry of secondary air from the surrounding atmosphere into the enclosure around the periphery of the surface, entraining abrasive in the primary air prior to the latter entering the enclosure, directing the abrasive entering the enclosure against the surface and entraining the spent abrasive in the air being removed from the enclosure by suction. An embodiment (Fig. 1) for abrading the flat surface of a workpiece (12) is identical with the apparatus described in Specification 1,070,233 with reference to Fig. 1 thereof. The seal (13) around the edges of the opening (11) in the portable blasting chamber (10) restricts the entry of air into the chamber from the surrounding atmosphere, either completely (if the seal is a rubber or similar skirt) or incompletely (if the seal is bristles). The pressures used are such that the chamber may be moved over the surface of the workpiece. If the chamber is lifted off the surface of the workpiece the feeding of abrasive to the chamber is automatically cut-off. When the workpiece surface is not plane, the opening and the seals may be shaped to conform to the surface; alternatively or additionally the seals may be sufficiently deformable to conform to the surface. An embodiment, Fig. 2, for abrading the internal surface of a tubular workpiece 50, comprises end members 51, 52 embracing the ends of the workpiece in an air-tight manner and held in position by clamps 53. End member 51 has a nozzle 54 and is connected to the conduit 16 through which air with entrained abrasive is drawn by the suction in the pipe 20 to which the end member 52 is connected. An embodiment (Figs. 3, 4) for abrading the external surface of a cylindrical tube (56) comprises a cylindrical chamber (55) of diameter approximately twice that of the tube. An entry (57) and an exit (58) for the tube are formed in the ends of the chamber and furnished with seals (59, 60). An outlet (61) for connection to suction extends radially from the chamber adjacent the exit. Six radial pipes (62) extend from the chamber adjacent the entry to a circular manifold (63) provided with an inlet for air and entrained abrasive. Mounted in each tube (62) is a nozzle (64) having a main cylindrical portion (65) and a convergent outer portion (66); the inner ends of the nozzles project into the chamber. The workpiece is moved longitudinally through the chamber. In a modification (Figs. 5, 6) pipes (71) with their nozzles are arranged so that the outlets lie upon the path of a helix coaxial with the chamber. Three pipes are connected to a manifold (73) and the other three pipes to a manifold (75), the manifolds being connected to an inlet conduit for air and abrasive.