Patent GB-823397-A (GB)
Title: Apparatus for treating surfaces of workpieces
IPC: B24C3/30
Filed: 1956-04-16
Abstract: 823,397. Abrasive blasting ; tumbling. WALKER, L. M. April 16, 1956, No. 11538/56. Class 60. Apparatus for treating work-piece surfaces comprises a rotatable impeller adapted to hurl a stream of surface-treating particles upwardly towards a work-piece region, an impeller casing partially enclosing the impeller and having an opening through which the stream of upwardly hurled particles can pass and a roof member for excluding downwardly falling particles from the region of downwardly-moving impeller portions, and recycling hopper means for collecting such downwardly falling particles and having a shoot-like outlet for directing such collected particles to the impeller to be hurled upwardly thereby. The apparatus has a main outer housing 10 to prevent escape of particles and dust ; extremely fine dust is removed by a blower 11 connected to an opening 13 with baffle plates 15. The work pieces are tumbled within a barrel 16 comprising a drum of wide mesh wire 23, the barrel is mounted upon trunnions 17, 18 and rotated by a motor 19. Alternatively the workpieces may be turned as upon a spit, moved in succession into and out of the stream, supported in the stream on a turntable or held stationary on a wire mesh table. Two impellers 24, 25 are provided, their planes of rotation being substantially in coincidence, and preferably parallel to but slightly offset to one side of the axis of rotation of the barrel 16. The impeller 24 comprises flat metallic strips 24<SP>a</SP>, 24<SP>b</SP>, e.g. of steel, adjustably secured by plates 29, 30 to a hub 27 on a rotatable shaft 28 driven by an electric motor 33 ; the impeller 25 is similarly constructed and is rotated by the same motor or by a separate motor 34. Each impeller has a box-like casing with substantially one upper quadrant removed for the upward escape of the particle stream. The casing 35 for impeller 24, which is identical with casing 36 for impeller 25, comprises vertical side plates 37, 38 and a roof member 35a mounted between them. Particles are fed into the casing 35 through openings 40, 41 located near the lower level of the path of movement of the impeller 24 and controlled by valve plates 42, 43. The particles are fed through the openings 40, 41 from primary hoppers 45, 46 ; the hopper 45, which is identical with hopper 46, is formed by the side plate 37 and an inclined plate 47 ; the hopper is charged with particles through a removable window 48. The rotating impeller strikes particles accumulated in the bottom region 49 of the casing 35 and also creates a vacuum which causes particles to be thrown upwardly into the path of the impeller blades. Spent particles fall into recycling hopper means comprising secondary hoppers 50, 51 above the primary hoppers 45, 46. The hopper 51 which is identical with the hopper 50, is constituted by an inclined plate 52 which directs the particles downward toward an opening 53 through which they pass on to a shoot 54; the opening 53 is formed in a plate 38<SP>a</SP> ; to assist the particles to reach the opening 53 a second inclined plate 55 is provided. The shoot 54, which is adjustable, directs the particles into the impeller path at about the level of the impeller shaft 28 and near the latter. The impeller casing is removable as a unit through an opening in the housing 10 ; it comprises wear plates 62, 65 and 66 which may be removably secured to the casing for replacement. The particles may be organic, e.g. pulverized husks or shells or inorganic, e.g. emery, pumice, marble dust, silicon carbide or divided metal; steel shot or carborundum globules may be used. The patricles may range from very fine powder up to 8/16in. in diameter, and may be mixed with a liquid to form a slurry.