PROBLEM TO BE SOLVED: To configure a fixing means so that an operation of extending a spray pipe for extending the travel distance of a chemical agent to be blown out of a nozzle at a front end of the spray pipe can be performed only by pulling out an extension pipe relative to a main pipe without rotating operation of a fastening nut during spraying operation, and the extension pipe is prevented from dropping out of a core cylinder even when the chemical agent is supplied to the spray pipe at high pressure.SOLUTION: A pressure receiving surface z for receiving the pressure of the chemical agent supplied into the spray pipe is formed on the rear end side of the core cylinder 5 having a cone-like fastening cylindrical portion 5a having a slit provided along the axial direction on the front end side, the core cylinder being slidably fitted to the extension pipe 2. The core cylinder 5 is pushed to a slide lock member 7 fixed to a main pipe 1 by the pressure of the chemical agent supplied into the spray pipe to perform fastening operation.
