PURPOSE: To permit a control circuit to be replaced, by providing electric connection terminals with a switch box and a main body, respectively and mounting the switch box on the main body.

CONSTITUTION: There is provided on the surface of a main body 2 a control unit mounting recessed portion 3 for mounting a switch box 4 for controlling an air blasting unit. The switch box 4 comprises a circuit substrate 6 having a microcomputer 5, a switch button 8 and an electric connection terminal A9. The control unit mounting recessed portion 3 has a connection terminal B10 to be coupled with the connection terminal A9. As a result, a user can replace a control circuit with ease.