Importance

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Abstract

A bag forming apparatus passes a hemmed web through a rotating edge notcher and related units to form a taped hem in the web which is passed through an intermittently operated bag making machine. A web supply unit includes a web take-up unit to maintain a constant tension in the continuously moving web to the bag making machine. The web notches are phased with the bag making machine to locate the notches centrally of each bag. During starting and stopping, the web take-up unit changes the web length moving through the notching unit at normal full web speed operation and the web length variations are minimal. A programmable notch controller actuates a stepper motor to rotate the notcher. The controller responds to a control signal to form a notch. A programmable switch is coupled to the bag making machine to generate a first control signal for each bag cycle and is phased with the full web speed to locate the notch centrally of the bag. A web driven encoder is coupled to the web upstream of the notcher and generates a pulse train connected to a counter for generating a second control signal for each web length corresponding to the length between notches.

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First Claim