GB1263246A - Improvements in or relating to methods of machines and apparatus for treating workpieces - Google Patents

Abstract

1,263,246. Blasting. ABRASIVE DEVELOPMENTS Ltd. 13 May, 1969 [16 April, 1968], No. 17774/68. Heading B3D. Apparatus for treating workpieces, e.g. by abrasive blasting, comprises a cabinet into which workpieces may be introduced, a conduit having one end open to atmosphere and the other arranged to direct air and treatment material at the workpiece in the cabinet, means to introduce treatment material into the conduit and to withdraw air from the cabinet, the air and material being caused to impinge on the workpiece solely by the removal of air. The material may be abrasive, either in a dry form, or in the form of a slurry with water, and which may contain chemicals such as a rust inhibitor and/or a mould release agent. A cabinet 10 contains means to support a workpiece; the means may move the workpiece, e.g. rotate it or move it through a given series of positions. The lower part of the cabinet is formed as a sump 11 connected by a pipe 12 to a first cyclone 13 connected to a second cyclone 14 connected by a pipe 15 to suction means 100. The lower end of the cyclone 13 delivers through an upper hopper 16, a middle hopper 17 and a lower hopper 18 into a primary air conduit 19 having one end 20 open to atmosphere, the other end opening within the cabinet 10 via a nozzle 21. The lower ends of the upper and middle hoppers 16, 17 are provided with flap valves 22, 23 each of which opens and closes in dependence on the difference in pressure between the two hoppers which it separates and on the weight of any material acting on the valve; the middle hopper is alternately placed at atmospheric pressure or at suction pipe pressure via a pipe 24 either as described in Specification 1,070,233 and by the automatic valve as described in Specification 1,246,132. When the suction means 100 is started, primary air is drawn into the cabinet along the conduit 19 and entrains material at 25 from the hopper 18. The material is directed by the nozzle 21 at the workpiece. The cabinet is capable of being completely sealed except for the inlet conduit 19 and the outlet pipe 12. Abrasive impinges on the workpiece and then falls into the sump 11 whence it is returned to the first cyclone 13 wherein reusable abrasive is separated from dust and detritus, the latter passing to the second cyclone 14 and to a dust-box 26. The reusable abrasive passes from the first cyclone 13 through the hoppers 16, 17, 18 to be entrained again at 25 in the primary air stream. Apertures 27 in the conduit 19 immediately outside the cabinet 10 allow secondary air to enter. This enables the speed of the primary air stream to be kept slow to minimize wear, except adjacent the nozzle when the air stream will be accelerated. The cabinet may have an air lock to enable workpieces to be introduced into and removed without completely destroying the vacuum.