10. The method of preventing packing in a sand hose and sand feeder conveying a sand and water sluurry to a hydraulic blast gun which comprises admitting clear water under pressure to the system at such a point that sand is forced backwardly from the feeder and forwardly from the hose and gun,copper ore crusher for sale said water under pressure being admitted before the blast gun is shut off and its admission being continued until no more sand is projected from the blast gun, the gun then being shut off before the clear water is shut off.
11. In a hydraulic sand blast gun, a gun body provided with three nozzles in tandem, means to project a high pressure liquid stream through said three nozzles, valve means to admit air between the rear nozzle and the middle nozzle, and means to admit abrasive particles mixed with water between the middle nozzle and the front nozzle.The combination with the supply pipe of a hydraulic, abrading gun, of means for feeding a slurry of abrading material to the supply pipe, Ssaid means comprising an apertured chamber adapted to be embedded in the wet abrading material, said supply pipe extending into said chamber in spaced relation to the inner periphery thereof, and means to admit a substantially sand free fluid to the feeder between the supply pipe and the chamber wall for washing abrading material from the supply pipe and chamber.
13. In a device of the class described, a gun, a sand supply system comprising a sand supply conduit connected to said gun, a feeder connected to the conduit, said feeder adapted to be inserted in a tank of wet sand to feed a sand slurry therefrom; and means to admit a substantially sand free fluid to the feeder in such a position Sthat sand is washed from the feeder, supply conduit, and gun.In a hydraulic sand blasting device, the combination comprising: an elongated body member having water intake and discharge ends, means to project a high pressure liquid stream through said body member, needle...