PURPOSE: To constitute the press piece of a switch compactly and to eliminate an unnecessary shock to the push botton of the the switch by pressing the push button by one end part of a U-shaped plate spring when a cover is closed, and releasing the push button when the cover is opened.

CONSTITUTION: The switch 10 is sandwiched between brackets 13 and 14 and fixed with a screw 15. The U-shaped plate spring 16 abuts on the push button 11 of the switch 10 and a spring 16 is clamped between a screw 17 screwed in the bracket 13 and a surface 18 and never falls out. When the cover is closed, a support 9 moves as shown by an arrow 24 to press one end 25 of the spring 16 while pressing the push button 11 by the other end. When the cover is opened, the push button is released. Consequently, the press piece of the switch is designed compactly and an unnecessary shock to the push button is eliminated.