PURPOSE: To enable a highly reliable switching action by providing a means of imparting a recovery force cyclically varying in the direction of releasing a switch to a system between a slight force detection point and a switch action point.

CONSTITUTION: A slight force detection mechanism 20 is composed of an initial end detection lever 21, a lever rotating shaft 22, an actuator 23 and a microswitch 24. When the initial end 10a of a paper hits a detection point A of a detection lever 21 to press it by a slight force F0, the lever 21 turns to actuate a microswitch 24 at the action point B through an actuator 23. This ensures accurate execution of actions such as stoppage of a conveyor 13, the stoppage of the rise in a table and the starting of the lowering thereof with a control circuit.