1. Field of the Invention
This invention relates to a turning bar draw-off device for a tubular film extrusion installation, with a plurality of turning bars which can be rotatingly driven around a common axis of rotation or in reverse by rotary drive mechanisms.
2. Discussion of Related Art
Turning bar draw-off devices for tubular film extrusion installations are known, for example as taught by German Patent Reference DE 21 56 079 C2. They are used for repeatedly changing the direction of tubular films previously extruded in the tubular film extrusion installation and conveyed to the turning bar draw-off device, and to move them off to a following winding device, wherein the repeated changing of the direction of the tubular film path occurs successively over the turning bars. As a result of the rotary or reversing movements of the turning bars, generated by rotary drive mechanisms, around a common axis of rotation, which customarily coincides with the axis of the supplied tubular film, tolerances in the thickness of the extruded tubular film are evenly distributed over the width thereof in the wound state, to assure a uniform winding result.
While the turning bar draw-off devices known are satisfactory with regard to their functioning, their mechanical structure is extremely elaborate and cost-intensive because of turning bars which must be driven with partially different rotary or reversing speeds, so that this appears to be worthy of improvements.