Abstract: Apparatus and method for heat sealing a selected segment of a web of at least two layers of biaxially oriented plastic film. The web layers are pressed together and a selected segment of the pressed web is heated above the bonding temperature of the plastic while adjacent web segments are maintained below that temperature. The surfaces pressing thus the heated web segment has a relatively lower surface friction than the surfaces pressing the adjacent web segment, whereby the layers of the heated segment of the web are physically unrestrained against shrinking during heating and are allowed to shrink back to their pre-oriented molecular configuration while the adjacent segment is restrained against movement. A hermetic bead seal is thus formed between the web layers. A product heat sealed according to the novel method is also disclosed.

Abstract: Apparatus and method for heat sealing a selected segment of a web of at least two layers of biaxially oriented plastic film. The web layers are pressed together and a selected segment of the pressed web is heated above the bonding temperature of the plastic while adjacent web segments are maintained below that temperature. The surfaces pressing thus the heated web segment has a relatively lower surface friction than the surfaces pressing the adjacent web segment, whereby the layers of the heated segment of the web are physically unrestrained against shrinking during heating and are allowed to shrink back to their pre-oriented molecular configuration while the adjacent segment is restrained against movement. A hermetic bead seal is thus formed between the web layers. A product heat sealed according to the novel method is also disclosed.

Abstract: Apparatus for bonding heat bondable materials through the application of pressure and heat employs a diaphragm pressed by fluid pressure against the materials. The diaphragm comprises a web having a flexible heating element which is bonded to its non-material pressing side and has a configuration corresponding to the desired seam configuration. The web carries heat dissipating means to conduct heat away from the diaphragm and the materials in the seam configuration and heat directing means to conduct heat from the element to the seam area. Preferably the heating element, heat directing means and heat conducting means are formed from metallic foil bonded to both sides of the web and having portions etched away to provide electrically insulating channels separating one from another.

Abstract: Apparatus for bonding heat bondable materials through the application of pressure and heat employs a diaphragm pressed by fluid pressure against the materials. The diaphragm comprises a web having a flexible heating element bonded to its non-material pressing side and has a configuration corresponding to the desired seam configuration. An improved heating element configuration is disclosed to reduce the forces tending to separate the element from the web as a result of their different coefficients of expansion and provision is made fo facilitate electrical connection to the heating element while reducing unwanted effects on the heat pattern.

Abstract: A device for heat bonding thermoplastic materials. At least one pressure chamber having a diaphragm is spaced from a supporting surface with the diaphragm and supporting surface in opposing relation to each other. Materials to be bonded are positioned between the pressure chamber diaphragm and supporting surface and the pressure in the chamber is raised above ambient pressure causing a deflection of the diaphragm. The amount of diaphragm deflection increases with the distance from the pressure chamber side wall. Either the supporting surface or the pressure chamber, or both, is moved toward the other causing a contact between the deflected diaphragm, supporting surface and the materials to be bonded. As the relative movement continues, the contact area with the materials to be bonded increases thereby progressively expelling air trapped between the materials.