GB1247701A - Improvements in or relating to abrading machines - Google Patents

Abstract

1,247,701. Blasting. ABRASIVE DEVELOPMENTS Ltd. 20 June, 1969 [21 March, 1968; 17 Dec., 1968], Nos. 13666/68 and 59973/68. Addition to 1,070,234. Heading B3D. [Also in Division B2] The apparatus described in Specification 1,070,234 in which a primary air inlet conduit is connected to one end of a blasting chamber, abrasive is entrained in the primary air flowing through the conduit upstream of its entry into the chamber, a workpiece closes aperture means in the wall of the chamber, suction is applied to draw the primary air and abrasive into the chamber and remove air and spent abrasive therefrom when the aperture means is closed by the workpiece, means direct the abrasive entering the chamber against the surface of the workpiece, and means restrict the entry of secondary air into the chamber around the periphery of the aperture means when the latter is closed by the workpiece, is modified by providing the primary air inlet conduit upstream of and adjacent its entry into the blasting chamber with means allowing tertiary air to join the primary air and abrasive flowing along the conduit. In an embodiment for cleaning wire or bar stock, the blasting chamber 10, Fig. 2, is tubular and consists of two channel-shaped parts 14, 15, Fig. 3, part 14 being fixed to a base structure 18 and part 15 being carried by arms 24 rockable about pivots 22 by hydraulic cylinders 30 to move the part from a closed, operative position to an open position, shown dotted, to enable the wire to be threaded into the chamber. Inlet and outlet housings 31, 32, each formed in two parts, are secured to the parts 14, 15 and are provided with conical wear resistant linings for guiding the wire into and through the chamber. Each housing has a replaceable insert 37, 42 which acts as the means for restricting the flow of secondary air into the chamber around the periphery of the apertures through which the wire passes into and out of the chamber and a flap valve 38, 44 which closes the chamber when a workpiece is absent. The means for directing the abrasive against the surface of the wire consists of two helical rows 50, 51 of nozzles which extend into a helical rib 52, Fig. 4, within the chamber. Each nozzle is connected to a conduit 65 through which the primary air and abrasive is supplied and consists of a ceramic tube 58 and a steel tube 54 having a lining 55 of synthetic rubber formed with a convergent passage 56. Holes 62 adjacent the lining and separated by vanes 64 allow for the entry of the tertiary air which joins the primary air and abrasive to cause acceleration thereof at the nozzle and permit the primary air and abrasive to move at a lower velocity in the conduits 65. The tubular blasting chamber 10 is connected by a suction conduit 20 to a connection 76, Fig. 1, in a cyclone 75 for separating reusable abrasive material which is returned by the conduits 65 to the nozzles. The cyclone 75 is connected by a pipe 77 to a second cyclone 78 which collects dust in a box 79 and is joined by a pipe 80 to a bag filter 81 which collects the residual dust in a box 82. A pipe 83 joins the bag filter to an extracter fan 84 which applies suction via the filter and cyclones 81, 78, 75 and conduit 70 to the blasting chamber 10. The reusable abrasive in cyclone 75 is deflected by a baffle 86 into an upper hopper 87 through a valve 90 to a middle hopper and through a valve 96 into a lower 95 open to atmosphere. The lower hopper has a deflector 94 for directing the abrasive to metering apertures connected to the primary air conduits 65. The valves 90, 96 are responsive to the pressure differences in the hoppers and weight of abrasive and are controlled by a valve 89 so as cyclically to place the middle hopper at the pressure of the lower hopper and the upper hopper to open and close the valves 90, 96 to pass the abrasive from the upper hopper to the lower. In another embodiment for cleaning strip 153, Fig. 9, the chamber is cylindrical 150 with wing-like portions 152 provided with guides 154 for the material. Nozzles 155, as described above, and a suction conduit 156 are connected to the chamber which may be coated internally opposite the nozzles with soft resilient material.