Guns for forming jets of particulate material

Claim 1

A gun for forming an abrasive jet of particulate abrasive material and liquid comprising: a body defining a bore therethrough, said bore having an axis and an opening at one end; means for connecting the other end of said bore to a conduit for supplying particulate abrasive material to said bore for ejection from said opening in the form of a jet of particulate abrasive material; a pair of nozzles which, when connected to a supply of high pressure liquid, provide a pair of high pressure liquid jets, each nozzle being shaped to provide a generally circular-section jets of liquid; means for connecting each nozzle to a supply of high pressure liquid; means for mounting said nozzles symmetrically relative to said axis of said bore with axes of said nozzles in a common plane including said axis of said bore and inclined towards said axis of said bore in the direction of flow of particulate material through said bore; a pair of guide surfaces each arranged in the path of the liquid jet from a respective one of said nozzles and symmetrically positioned relative to said axis of said bore, each guide surface being formed on an external surface of said body and having a part-cylindrical shape, the axes of the cylinders of said guide surfaces being parallel and perpendicular to said axis of said bore and disposed in a plane downstream of said opening of said bore, the central diametral plane of each part-cylindrical surface including said axis of the respective one of said nozzles, each said guide surface being so positioned relative to the respective nozzle that the jet issuing from said respective nozzle will impinge tangentially on said guide surface and said liquid jets will be flattened by said guide surfaces and will converge and intersect along a line parallel to said axes of said cylinders and on said axis of said bore to flatten the jet of particulate abrasive material issuing from said bore.