Finwheel servo drive for packaging machine

Abstract

In a horizontal packaging machine for wrapping and sealing articles with flexible films, a servo control system for maintaining synchronism between the finwheel drive, the in-feed conveyer and the cut-off knife assembly so that proper registration of the graphic art work on the packaged article is achieved. The finwheels are driven by a D.C. motor whose armature windings are connected to the output of a servo amplifier. A master tachometer driven by the horizontal wrapper's drive motor provides a voltage which is directly proportional to the angular velocity of that drive motor. The output from the master tachometer is passed through a calibrating network and into a first input of the servo amplifier circuit. A second tachometer is coupled to the finwheel shaft and produces a feedback signal proportional to the angular velocity of the finwheels. The feedback signal is applied to the second input of the servo amplifier and functions to control the D.C. current driving the finwheel drive motor. The system also includes a digital logic network which senses a reference mark on the film from which the package is formed along with the rate at which the end-seal cutting blade is rotating to produce a supplemental or vernier control signal for adjustment of the rotational speed of the finwheel.