Heat sealing apparatus for a strapping machine, heat control means and filter apparatus for use in such a machine.

摘要

There is disclosed a strapping machine for applying a plastic strap around an object, tensioning the strap and heat-sealing together overlapping portions of the strap, including a retractable heating member movable between the overlapping strap portions and a pressure-applying means including a pressure block with a tiltable universal joint coupling for pressing the overlapping strap portions against the heating element with a first relatively light pressure to melt the facing surfaces thereof. The heating element is withdrawn while the pressure-applying means presses the strap thereagainst with the first pressure, and then the melted strap portions are pressed together with a strong second pressure to complete the seal. A cam with a yieldable section controls the first pressure and a compression spring controls the second pressure. While retracted, the heating element is raised to a higher temperature for burn-off of strap residues. Switch means disposed in the strap path provide a positive stop to prevent strap overfeed while a yieldable track section permits escape of excess strap from the path to prevent jamming. Air filter means remove waste products of the heat-sealing operation.