| 摘要 |
Each nozzle unit includes one or more blowing nozzles (76, 78) and one or more air extraction nozzles (82, 84) of greater cross section. In the discharge region, each extraction nozzle has a closure- and cleaning unit. Preferred features: A plunger (76) performs both cleaning and closure duties, when introduced into the discharge region of the extraction nozzle. The plunger drives contaminants out. It is constructed as a blasting nozzle (76). The unit is constructed in a cylindrical nozzle casing (50) (like a boiler dome), set against the drum (12) and communicating with its interior, through the nozzle openings. A piston (28) in the nozzle casing moves back and forth, to operate the cleaning and closure unit. The medium for blasting, moves the piston into the closure position. A branch line supplies the blast nozzles with the blasting medium. The piston is spring-loaded away from closure. The piston carries the plunger used in the closure and cleaning operation, which closes the air extraction openings. Each nozzle unit carries a number of blasting and air extraction nozzles. The extraction nozzle is formed by a hole which widens away from the plunger introduced into it. The nozzle casing carries a perforated insert (80) with a pattern of air extraction holes; the piston carries a corresponding pattern of rod-shaped blasting nozzles. |
