Hall Dielectric Machinery, Inc.

William A Hall

Arnold Tobler

An improved apparatus and method for joining two or more thin sheets of thermoplastic materials along a welded seam includes a welding assembly and a means for feeding the thermoplastic sheets to the working area of the welding assembly. The welding assembly includes a heated platen welding press coupled with a welding tool, an energy generator electrically connected to the welding tool and control means electrically connected to the welding press, the welding tool and the energy generator. The welding press includes a pair of opposed platens, means for heating each of the platens and pressing means for displacing at least one of the opposed platens in the thickness direction of the thermoplastic sheets. Pressure is applied to the thermoplastic sheets by using the pressing means to displace at least one of the heated platens in the thickness direction of the thermoplastic sheets. Heat produced by the heating means is then transferred to the thermoplastic sheets by the heated platens to raise the temperature of the thermoplastic sheets in the area of the welded seam to a first predetermined temperature which is below the softening temperature of the thermoplastic materials. High frequency energy produced by the energy generator is then conducted to the thermoplastic sheets by the welding tool to raise the temperature of the thermoplastic sheets in the area of the welded seam to a second predetermined temperature which is above the softening temperature but below the melt point of the thermoplastic materials. Conduction of the high frequency energy is then discontinued so that the thermoplastic sheets fuse together along the welded seam under applied pressure. Application of the pressure is then discontinued so that the welded thermoplastic sheets may be removed from the welding assembly.

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Tega Cay, SC, United States of America

William A Hall