GB1424896A - Jet forming apparatus - Google Patents

Abstract

1424896 Blasting B E HART 5 June 1974 [25 May 1973] 25254/73 Addition to 1403528 Heading B3D A method of operating a particulate material jet forming apparatus comprises producing a jet of particulate material and liquid at an outlet nozzle of a gun 1, the material and liquid being drawn into the gun from a supply means 14 by vacuum created in the path of the mixture by a high pressure jet of liquid 8 around the path thereof, and diverting at least some of the liquid forming the jet into the path of the mixture flowing to the gun adjacent the outlet of the supply means 14 therefor. The gun 1 is as described in Specification No. 1,403,528 with the valve assembly 2 rotated through 90 degrees relative to sand and water mixture flow passage 3. Depression of handle 5 operates valve 2 so that water at a pressure between 2000 and 5000 p.s.i. passes through passages 11, 7 and impinges on a tapered surface 8 to form a conical jet which, in turn, creates a vacuum drawing a mixture of sand and water in hopper 14 through passages 19, 20, flexible hose 12 and passage 3 to the nozzle, an extension 9 of a tubular member 10 forming passage 3 protecting the surface 8 from abrasion by the sand and water mixture. To prevent a deposit of sand in passage 3 when the valve assembly is closed, the return port 4 of valve assembly 2 is coupled by a flexible hose 16 to a passage 22 in the outlet 13 of the hopper, and a bleed port in passage 11 is connected by a flexible hose (17, Fig. 2, not shown) to a passage 24 in the outlet 13 having a nozzle 25. When the apparatus is in use, the water which passes through the bleed port and is formed into a jet by the nozzle 25 assists the vacuum created by the conical jet in drawing the mixture of sand and water from the hopper 14. When the apparatus is not in use, the water from the supply passes along hose 16, passages 22, 20 and passage 3 to clear the gun of sand. The back pressure of the water in hoses 16, 12 prevents the mixture of sand and water leaving the hopper and may cause turbulence, and hence mixing, of the mixture in the hopper. In an alternative arrangement, the supply to nozzle 25, instead of coming from the bleed port, is from the pump outlet.