Bag opening method and apparatus for use in bag filling and packaging

Abstract

A bag opening method and apparatus for use in bag filling and packaging in which a bag B is gripped at its laterally opposite side edges with a pair of gripping members and moved along a predetermined path. A pair of suction cupsdisposed facing each other at respective mutually spaced standby positions are moved to respective closest positions at which a vacuum is applied to the suction cups to cause them to adhere to the outer surfaces of the opposite side walls of the bag. The suction cups are retracted away from each other to respective intermediate positions between the closest and standby positions. The suction cups having reached the intermediate positions are stopped there for a predetermined period of time. Thereafter, the suction cups are retracted from the intermediate positions to the standby positions, respectively. The vacuum acting upon the suction cups is measured at some point during a time period which starts immediately before the suction cups reach the intermediate positions and ends at the termination of the period of time during which the suction cups are stopped at the intermediate positions. The application of the vacuum to the suction cups is stopped at a time between a time after the measurement of the vacuum and a time immediately after the starting of movement of the suction cups to the standby positions. The measured vacuum is compared to a preset reference value to judge whether or not the bag has been opened satisfactorily. The positions of the intermediate positions are changed according to the width of the bag.