Wrapping machine and method

Abstract

A wrapping machine which includes a film former for shaping a continuous film of packaging material into a continuous tube, a film drive for drawing the continuous film of packaging material past the former and past a cutting and sealing station, a product infeed drive for feeding products to be packaged through the former into the continuous tube of packaging material so that the products are spaced apart from one another in the tube, and a motor-driven rotary cut/seal head at the cutting and sealing station for cutting and sealing the continuous tube of packaging material as each product moves through that station. The wrapping machine also includes independent closed-loop servo-control circuits for the film drive, the product infeed drive, and the cut/seal head drive, each of which is responsive to a desired velocity control signal. The wrapping machine also includes a first encoder on the shaft of a roller driven by the moving film a second encoder coupled to the product infeed drive, and a resolver coupled to the cut/seal head drive. A microprocessor-based controller (MBS) is coupled to the encoders, the resolver, and the servo loops for the infeed, film feed, discharge and cut/seal head drives. It derives a desired infeed velocity signal and a cut/seal head velocity profile signal based upon a film drive motor tachometer and outputs these desired velocity signals to the respective servo loops for the product infeed drive and the cut/seal drive. The controller is further responsive to the film travel encoder, film eyespot sensor, infeed travel encoder and pusher sensor outputs to adjust the product infeed velocity to maintain proper orientation of the products relative to the film. The controller is likewise responsive to the sensor inputs to adjust the cut/seal head velocity to maintain proper orientation of cutting and sealing relative to the film and product positions.