GB673216A - Improvements in or relating to blast guns - Google Patents

Abstract

673,216. Sand-blast. PANGBORN CORPORATION. Feb. 17, 1950, No. 4102/50. Class 60. A high velocity blast gun has secured on its nozzle in radially spaced relation thereabout a member which extends beyond the end of the nozzle and has a bore gradually tapering away from the nozzle end to a diameter greater than that of the nozzle outlet. A blast gun comprises a jet 26 disposed in a chamber 27 and projecting at high velocity a stream of liquid under pressure, such as water 28, from a pipe 29 into the nozzle 15. An abrasive, such as wet sand 30, is led into the chamber 27 through a pipe 31. The abrasive mixes with the liquid in chamber 27 and is projected through the nozzle 15. An elongated tubular member 11 has a rear end 14 larger than the outlet end of the nozzle 15 of the gun. The inner wall of the rear end 14 is provided with a group of inwardly projecting fins 16, secured to or integral with the rear end 14, and their inner edges 17 fit snugly about the outlet end of the nozzle 15. Shoulders 18 are provided within rear end 14 to engage the nozzle tip 19 when the latter is properly inserted in the rear end 14, thereby making it easy to dispose the member 11 or the nozzle in the proper relative position. The nozzle and member are held together in this relationship by a set screw 20. The spaces between the fins 16 are open to atmosphere through openings 21 and also communicate through openings 23 with the bore 22 of the discharge end 12. The bore 22 has a gradual taper from its rear to its forward tip 24 where the diameter is greater than that of the nozzle outlet 25. In operation, as the stream 13 of mixed liquid and abrasive from the nozzle lo passes through the bore 22, it induces a flow of air from the atmosphere through the channels between the fins 16; the indrawn air passes through the bore 22 and is trapped between its wall and the stream 13 passing therethrough. Since the cross-sectional area of the bore decreases toward its tip but is always greater than the nozzle outlet, the trapped air becomes more and more compressed, and the pressure created by 'the compression tends to maintain the liquid and abrasive stream in a concentrated state.