hooked to the holder 36b via a tension spring 40 and the other end secures the corona wire 35 to the holder 36a with a vis 37 as shown in fig2 the bottom of a second protrusion section 102 of the charger wire holder 36a at the front side of the device is shaped as a elastically deformable claw which allows it to be hooked to a holder hooking section a second engagement section 32a provided in the base plate 31 a front frame 38 which comprises a first sidewall 42 is secured to the front side of the base plate 31 the frame 38 has a guide port for guiding the transferring charger unit 9 to a given position provided in the first sidewall 42 near this guide port is an opening section 44 which allows the release of a second protrusion section 102 of the charger wire holder 36a from the engaging hook section 32a of the base plate 31 by a press rod 39 as shown in fig2 two springs 33 are inserted between the base plate 31 and charger case 34 so that the transferring charger unit 9 may be pressed upward while being set to be engaged with the base plate 31 being in the state where the second protrusion section 102 of the holder 36a at the front side of the device is hooked to the second engagement section 32a and the first a protrusion section 101 of the holder 36b at the.