Apparatus for severing and heat sealing sheets of thermoplastic material

A method of heat sealing and simultaneously severing overlapping portions of thermoplastic sheets to each other, comprising the steps of fixedly supporting one side of one of the overlapping portions on a flat supporting surface;

• biasing one side of the other of the overlapping portions so that the overlapping portions are pressed each other, including contacting said one side of the other portion with a pair of elastic spreading implements;
• simultaneously stretching the overlapping portions in a predetermined direction by the spreading implements;
• and contacting the one side of the other portion with a heated tool which severs the overlapping portions transversely of said directly and simultaneously heat seals the overlapping portions to each other whereby the thus obtained severed parts of the overlapping portions are automatically separated from each other as a result of said streching step.

Apparatus for sumultaneous severing and heat sealing of thermoplastic sheets, comprising a sheet supporting anvil having a flat sheet supporting surface;

• a hold-down device arranged to urge the sheets against the supporting surface of the anvil in the course of a combined severing and heat sealing operation, said device having a core and a heat-resitant outer layer surrounding at least a portion of the core and having an edge arranged to contact the sheets in the course of said operation;
• a combined severing and heat sealing tool movable into engagement with sheets which are supported by said surface of the anvil and are held by said heat-resistant layer, said tool comprising a blade having a predetermined thickness and said core including at least one plate-like member whose thickness matches or approximates said predetermined thickness, said outer layer having an end face adjacent said edge and sloping away from said surface of the anvil and toward said blade;
• and means for heating said tool.