Patent ID: 8245484

Claim:
A bag opening method for use in bag filling and packaging in which a bag is gripped at its laterally opposite side edges with a pair of gripping members and moved along a predetermined path to open said bag and to fill an article to be packaged into said bag, said method comprising the steps of: moving a pair of suction cups which are facing each other from respective mutually spaced standby positions to respective closest positions at which said suction cups are closest to each other; applying a vacuum to said pair of suction cups to adhere to outer surfaces of opposite side walls of said bag at said closest positions; retracting said suction cups away from each other to respective intermediate positions between said closest positions and said standby positions while moving said gripping members toward each other in synchronism with movement of said suction cups to the intermediate positions; keeping said suction cups stopped at said intermediate positions for a predetermined period of time; measuring the vacuum being applied to said suction cups at some point during a time period which starts immediately before said suction cups reach said intermediate positions and ends at a termination of the period of time during which said suction cups are stopped at said intermediate positions; retracting said suction cups from said intermediate positions to said standby positions, respectively; stopping application of the vacuum to said suction cups at a time between a time after the measurement of vacuum and a time immediately after starting of movement of said suction cups to said standby positions; comparing the vacuum measured to a preset reference value to judge whether or not said bag has been opened satisfactorily; and changing positions of said intermediate positions according to a width of the bag.