PURPOSE: To certainly and smoothly select a nozzle at a desired injection expanse degree, by mounting a nozzle pipe to the leading end of a jet pipe while mounting an eccentric plate to the outside thereof and fixing the nozzle to a nozzle holder to perform the multi-stage control of the injection expanse degree.

CONSTITUTION: A nozzle pipe 3 is mounted to the leading end of a jet pipe 1 in an inlaid state and an eccentric plate 5 is mounted to said jet pipe 1 so as to be fitted therearound while the eccentric plate 5 and a nozzle holder 7 are threaded by a nut 8. Nozzle orifices 6aW6d having different injection expanse degrees are provided to a nozzle 6 so as to pierce therethrough and brought into communication with a nozzle pipe 3 so as to be contacted therewith under pressure. The nozzle holder 7 is revolved around the center axis of the eccentric plate 5 at a constant angle to perform the injection of a liquid having a desired injection expanse degree.