High-temperature, heat-sealed products and methods and means for their manufacture

A heat sealing apparatus for sealing high-temperature thermoplastic material having:

• (a) a first hollow flat band compression member, having a first sealing surface;
• (b) a second flat band compression member, having a second sealing surface opposing the first compression member;
• (c) means for rapid impulse heating at least said first sealing surface to provide flash heating, said rapid impulse heating means having an electrically conductive sealing element having a first end and a second end;
• and
• (d) means for rapidly cooling at least said one sealing surface, said rapidly cooling means being in fluid communication with a vortex tube capable of providing a coolant fluid at least within said first hollow flat band compression member for immediately cooling said one sealing surface to room temperature or below by contacting the sealing element with chilled coolant fluid from the vortex tube, whereby a high temperature thermo-plastic workpiece to be sealed may be inserted between the first and second compression members, together with flash heating and cooling of the sealing element, thereby to achieve a heat seal in the workpiece.

A method of forming a heat seal in high-temperature thermoplastic film, comprising the steps of:

• (a) providing apparatus having
• (i) a first compression member, having a first sealing surface;
• (ii) a second compression member, having a second sealing surface, that opposes the first compression member and that has an electrically conductive sealing element having a first end and a second end and being in fluid communication with a vortex tube capable of cooling a coolant fluid disposed therethrough and further being attached to an electrical power source and backed by a layer of high-temperature, resiliant material capable of supporting the sealing element;
• and
• (iii) two floating sheets or tapes of high-temperature release material each having a thickness between 0.001" and 0.0301" disposed therebetween but not in constant contact therewith wherein the sealing element is rapable of being flash-heated to a maximum temperature of about 1100.degree. C. (c. 2000.degree. F.) by application of electric current from the power source and immediately cooled to room temperature or below by contacting the sealing element with chilled coolant fluid from the vortex tube via the first end of the sealing element;
• (b) inserting between the two floating sheets of high-temperature release material a high-temperature thermoplastic workpiece to be sealed having at least two boundary edges;
• (c) providing a compressive force sufficient to bias the first and second compression members against the workpiece;
• (d) simultaneously applying sufficient electric current from the power source to the heating element to flash-heat the element to a desired sealing temperature, thereby heat sealing a desired portion of the workpiece;
• (e) subsequently contacting the sealing element with chilled coolant fluid introduced to the sealing element lumen from the vortex tube via the first end of the sealing element, in order to return the heat sealed portion of the workpiece to at least about room temperature;
• and.
• (f) removing the compressive force from the first and second compression members such that the heat-sealed workpiece is released from the apparatus.