PURPOSE: To detect whether it is a new article or not when the parts to be exchanged are exchanged by providing a switch operating part, which operates a switch at the time of first mounting and is turned to a switch operation disabled state in response to that switch operation, at the prescribed position of parts and continuously keeping the switch operation disabled state of that switch operating part.

CONSTITUTION: A limit switch 1a for new article detection is provided at the prescribed position of a main body 1 of device and a first section 3a and a projecting part 3d are provided at the prescribed position of exchangeable parts 2 as the switch operating part which operates the limit switch 1a at the time of first mounting and is turned to the switch operation disabled state in response to that switch operation. The switch operation disabled state of these first section 3a and projecting part 3d is continuously kept by a recessed part 4b as a holding part. Thus, when the parts 2 to be exchanged are exchanged, whether it is the new article or not can be surely detected.