GB617161A - Method and apparatus for sand blasting - Google Patents

Abstract

617,161. Sand-blast. MEAD, W. H. Aug. 29, 1945, No. 22282. [Class 60] Apparatus for sand-blasting surfaces comprising means for applying a stream of air mixed with particles of sand against the surface and means for impeding movement of sand beyond a confined area, is characterized in that the latter means permit the air from the surrounding area to flow therethrough. The operating head 31, Fig. 1, has an inner shell 72, Fig. 4, through which the sand-blast passes on to the work, and an outer casing 75 connected to a suction line 45; the rim 79 of the casing is spaced from the work surface by adjustable feet 83. A brush or other porous, easily flexed, maze-like baffle member 84 bears on the work surface; a flexible boot 85 may also be provided. This arrangement serves to confine spent abrasive and debris to the working zone; they are carried up the tube 45 to a cyclone separator 41, debris being collected in container 44, abrasive in a hopper, and dust in a filter 39. Abrasive can pass from the hopper to chamber 30 through a valve 65 which normally opens under its own weight plus that of the abrasive; compressed air is supplied through pipe 26 to the top of the chamber 30 to maintain the abrasive therein under pressure to assist its feed into the compressed air stream. Pressure air also passes through connection 29 to hold the valve 65 closed. The compressed air passes through a slidable tube 50, Fig. 2, urged by a spring against a fitting 47, thus scouring out the pipes and blast nozzle; pressure passes through a bleed port 63 in the tube 50 and when it has built up sufficiently, moves the tube 50 back against the spring, thus opening up a gap for the i admission of sand. The compressed air is controlled by a valve 23 electrically controlled by a switch 71 on the operating head 31 and by a switch which is normally opened but which is closed by contact of the operating head with the work surface.