Packaging machine with continuous sealing jaw movement

Abstract

An apparatus for cross sealing a continuously moving plastic tube, such as to form bags for packaging in a form-fill-seal packaging machine is disclosed, along with a related method. The tube is fed continuously between a pair of opposed sealing jaws that move toward and away from each other in a polygonal path. Substantially continuous sealing pressure is provided between the jaws during a sealing pattern of movement along the path, with the remainder of the path including a return pattern of movement away and back towards the sealing zone. Each sealing jaw is carried on a bridge extending between dual gear assemblies. The sealing pattern of movement along the path is substantially linear so as to provide highly efficient sealing. The polygonal path is established by an offset point on an output shaft/pinion; the locus defining the path being selected from the group of hypotrochoids and epitrochoids. To provide the hypotrochoidal path, each gear assembly preferably employs a pinion rotating around the inside of a ring gear with an integer gear ratio, such as 3:1-5:1. For the epitrochoidal path, the pinion is rotating about a fixed sun gear with an idler in between, and may establish the same integer gear ratios. Sliding guide rods between the sealing jaws maintain the jaws parallel during the sealing and return patterns of movement.