PURPOSE:To make it feasible to prevent gap between conveyor platform bars from being plugged as well as to reduce conveyance resistance by providing a presser member, which is inserted into the gap between and makes a linking motion with a conveyor platform bars which makes a reciprocating movement back and forth by means of a crank shaft driven by a motor. CONSTITUTION:A conveyor platform 2 makes a reciprocating movement back and forth in parallel to an interlocking member 5 by means of the rotation of a crank shaft 7 driven by a motor. A cam case and a cam plate make displacement toward the same 'a' direction linking with the conveyor platform 2. This causes a cam surface portion 12a of the cam plate 12 to push a roller 14 of an actuating arm 13 and increase the inclination angle. The actuating arm 13 then inclines toward the 'b' direction fulcruming an axis P4 while the interlocking member 5 makes a parallel movement to the conveyor platform 2 in the 'c' direction opposing to the direction of the conveyor platform 2 movement. When the conveyor platform 2 makes displacement up to the limited position toward the front, the actuating arm 13, slipping out of the cam plate 12 by virtue of the cam surface 12c, returns to its vertical posture. Thus the interlocking member 5 returns to the front and the presser member 4 returns from a standing-by posture to a colliding posture but solid substances can be moved forward in the distance the conveyor platform advanced.