PURPOSE: To correctly set the insertion timing of a blanking plate and the insertion timing for temporary receiving of paper by installing a cam and a rotary encoder which revolves by one time during the time from the start of lowering of a guide rail to the start of lowering of the next guide rail, onto an endless chain driving shaft.

CONSTITUTION: A gear 32 is installed onto the driving shaft 18 of an endless chain, and the revolution is transmitted to a rotary encoder 38 directly connected with a cam 41 and a cam shaft 37 through the gear 36 of the cam shaft 37. The rotary encoder 38 and the cam 41 are revolved by one turn during the time when a guide rail lowers by one pitch. The cam 41 is operated by the contact with a limit switch 43. Therefore, the inserting timing of a blanking plate and the insertion timing of the temporary receiving for obtaining a constant load can be set correctly by the cam 41, counter for counting the generated pulse of the rotary encoder, and a digital switch in which the loading quantity is set. Therefore, dispersion of the loading quantity and the excessive loading can be prevented.