SEAL DETECTION METHOD IN PACKING BOX AND DETECTOR USED THEREFOR

PURPOSE:To surely detect a seal without being influenced by the pattern of the seal, etc., by detecting a seal, etc., inserted into a packing box in a packing process before sealing the box and by removing a defective packing box. CONSTITUTION:A detecting port for detecting whether there is any seal 3 is lowered whenever a packing box 2 arrives, a positive pressure is injected from the detecting port, and the presence of the seal 3 is detected by the change of the back pressure of said positive pressure. When the detecting port is wider than the width dimension of a product, air leaks from the space between products if there is no seal so that the presence of a seal is detected by the change of air pressure. A seal detector is provided in the supply process of packing boxes 2 before packing, where a plurality of products are accommodated in parallel, and is constituted by a detection end composed of a hollow tube being simultaneously lowered whenever the packing box 2 arrives from above the products arranged in parallel, a pressure detector 23 for detecting the back pressure in the hollow and a compressed air supply source for supplying positive pressure.