DEVICE AND METHOD FOR TESTING HEAT SEALS

Abstract: A universal heat seal tester (10) and method is provided for simulating heat-sealing processes. The tester (10) includes a pair of sample holders (11, 12) each of which hold a sample (20). A heater (30) is removably placeable between the samples (20), and the invention can simulate a hot-air side-seaming section of a cup machine. The method and apparatus test heat seals between the samples (20) while simulating real manufacturing processes, specifically heat sealing process, and can simulate other types of heat-sealing processes, such as ones relating to liquid packaging machines, which include electric, gas-fired, hot-air, induction, and radiant heating. The method and apparatus can be run automatically to eliminate operator variability.

Description: DEVICE AND METHOD FOR TESTING HEAT SEALS BACKGROUND OF THF TNVENTION 1 • Field of the Invention The present invention relates to a universal heat seal tester. More particularly, the present invention relates to a method and apparatus for simulating heat-sealing processes. The invention can simulate a hot-air side-seaming section of a cup machine. 2. Description of the Prior Art During the production of cupstock, various problems relating to the heat-sealability of cupstock occurred which indicated that a better, more realistic method of determining the heat-sealability of materials for use as such cupstock was needed. Various methods and apparatus have been developed to test and inspect heat seals. For example, U.S. patent No. 3,743,562 (Phipps) discloses an apparatus for testing heat seals between sheet materials, and employs a pair of rotating heated elements. The speed and temperature to which the rotating elements are heated can be varied. The apparatus requires the rotating element to directly contact the heated sheet material. Another method is shown in U.S. patent No. 3,533,548 (Taterka) which pertains to a method of visually ascertaining whether a section of plastic sheet is securely sealed to an adjacent surface. The method performs its non-destructive seal inspection by using transparent media sealed to a substrate and inspection of the seal through the transparent media. U.S. patent No. 3,444,732 (Robbins) relates to a method and apparatus for determining optimum bonding parameters for thermoplastic material. Different heating temperatures are simultaneously applied through heated metal elements, which directly contact the substrate being tested. All of the foregoing methods and devices suffer from a common drawback, specifically, they operate in an environment or way which fails to resemble actual process conditions. Unless the testing can be performed in such a way that the actual process conditions are simulated, any results will be of limited or no value. As a direct result of the positioning of the heating and tested elements in direct contact with the sheets being tested, the aforementioned devices cannot achieve accurate simulation of the processes they are trying to test. SUMMARY OF THE INVENTION These and other deficiencies of the prior art are addressed by the present invention which is directed to a method and apparatus for testing heat-seals while simulating real manufacturing processes, specifically heat-sealing processes. In particular it is an object of the present invention to provide a method and device which simulate a real heat-sealing manufacturing process. Another object of the present invention is to simulate a hot-air side-seaming section of a cup machine. Yet another object of the present invention is to simulate other types of heat-sealing processes, such as ones relating to liquid packaging machines, which include electric, gas-fired, hot-air, induction, and radiant heating. A further object of the invention was to reduce operator involvement, by implementing an automated test sequence. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and attributes of the present invention will be described with respect to the following drawings in which: FIG. 1 is a flow chart of a method according to the present invention; and FIGS. 2a-2d are schematic views of the steps of the method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1 and 2a-2d, the method and device 10 of the present invention employs two sample holders , a left and right sample holder 11 and 12, respectively, to clamp two samples 20 along two edges. The samples 20 can be laminates such as opaque substrates, and can be paper, plastic, or foil laminates or a combination of those elements such as- pa¬ per/plastic laminate or paper/foil/plastic laminate. Several pins (not shown) may be positioned on the sample holders 11 and 5 12 so that they come close to the back sides of the two samples 20, and thus provide some support in the event that one or both of the samples 20 moves during the process. The samples 20 are positioned so that the surfaces to be sealed are in face-to-face relation with one another, and so 0 that a gap exists between the two samples 20. At least one movable heater 30 moves between the samples 20 to heat sections of the samples for preprogrammed lengths of time, as shown in Fig. 2a. In the illustrated embodiment two heaters 30 are shown. A staggered time difference for heating the two samples 20 may 5 be incorporated. The heaters 30 are then withdrawn, and after a prepro¬ grammed delay the right sample holder 11 moves closer to the left sample holder 12, as shown in Fig. 2b. The left and right sample holders 11 and 12 are then clamped together after a second preprogrammed delay, as shown in Fig. 2c. The pressure at which the left and right sample holders 11 and 12 are clamped is adjustable. Similarly, the length of time the two samples 20 are clamped together is adjustable. Once that preprogrammed length of time has expired, the two sample holders 11 and 12 are separated as can be seen in Fig. 2d, and the two samples 20 are pulled apart after a programmable delay. The quality of the seal is then evaluated. All of the time periods and delays, temperatures, air¬ flow rates and pressures can be varied to particular machine operating parameters. The actual times, temperature, pressures, and delays can be monitored in real time by an operator, by , utilizing an operator interface and other indicting devices. The time periods, temperatures, pressures, air flow, , sample size and/or configuration can be changed as desired. The heater 30 does not come into contact with the samples 20. The type and size of the heater 30 can be varied. For example, the heater 30 may be an electric heater, a gas-fired heater, an inductive heater or a radiant heater. Once the two samples 20 are undamped, they can be peeled apart after a delay, as set forth previously, or immediately. The present invention may incorporate a configuration where only one of the sample holders 11 and 12, or both of the sample holders 11 and 12 are movable towards one another. Furthermore, the invention is not intended to be limited to a single heater 30, but rather, any number of heaters may be employed. As a result of the method and apparatus of the present invention, realistic simulation of heater temperatures, heating times, air flows, clamping temperatures and pressures, and other time periods, important to the heating process, can be pro¬ grammed. An automated testing protocol may be used to eliminate operator dependence. The automated testing can continuously monitor the times, air flow, temperatures, and pressures. The sample holders can be moved by air cylinders, or by other comparable mechanical devices. Having described several embodiments of the device and method for testing heat seals in accordance with the present invention, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the description set forth above. It is therefor to be understood that all such variations, modifications and changes are believed to fall within the scope of the invention as defined in the appended claims.

Claims: WHAT IS C-LAIMED IS: 1. A heat seal testing device comprising: two sample holders, which each hold one of two samples so that said two samples have a gap disposed between said samples, means for moving said sample holders towards and away from each other, a heater for heating said samples, and clamping means for clamping said sample holders together. 2. A heat seal testing device as recited in claim 1 , wherein said heater is an air heater. 3. A heat seal testing device as recited in claim 1, further comprising a plurality of heaters. 4. A heat seal testing device, as recited in claim 1, wherein said two sample holders are moved toward one another after said samples are heated by said heater. 5. A heat seal testing device, as recited in claim 4, wherein said clamping means clamps said two sample holders together after said sample holders are moved together. 6. A heat seal testing device, as recited in claim 1, wherein said heater is movable into and out of said gap between said samples. 7. A heat seal testing device, as recited in claim 1, wherein a temperature to which said samples are heated is adjustable. .8. A heat seal testing device as recited in claim 5, wherein a pressure to which said two sample holders are clamped is adjustable. 9. A heat seal testing device as recited in claim 1, wherein a time period for which said samples are heated is adjustable. 10. A heat seal testing device as recited in claim 1, wherein a time period for which said samples are clamped is adjustable. 11. A heat seal testing device, as recited in claim 4, wherein one of said two sample holders has a fixed position and another of said two sample holders moves toward said one of said two sample holders after said samples are heated by said heater. 12. A heat seal testing device, as recited in claim 1 , wherein one of said two samples is paper and another one of said two samples is a paper/plastic laminate. 13. A heat seal testing device, as recited in claim 1, wherein said two samples are paper/plastic laminates. 14. A heat seal testing device, as recited in claim 1, wherein said two samples are paper/foil/plastic laminates. 15. A heat seal testing device, as recited in claim 1 , wherein one of said two samples is one of paper and pa¬ per/plastic laminate and another one of said two samples is paper/foil/plastic laminate. 16. A method of heat seal testing comprising: supporting two samples on sample holders, with a gap disposed between said samples, heating said samples, moving said sample holders towards and away from each other, and clamping said sample holders together. 17. A method of heat seal testing as recited in claim 16, wherein said heating step is performed by a plurality of heaters. 18. A method of heat seal testing, as recited in claim 16, wherein said moving step is performed after said heating step. 19. A method of heat seal testing, as recited in claim 16, wherein said clamping step is performed subsequent to said moving and heating steps. 20. A method of heat seal testing, as recited in claim 16, further comprising the step of moving said heater into and out of said gap between said samples. 21. A method of heat seal testing, as recited in claim 16, further comprising the step of adjusting a temperature to which said heaters are heated. 22. A method of heat seal testing as recited in claim 16, further comprising the step of adjusting a pressure to which said two sample holders are clamped. 23. A method of heat seal testing as recited in claim 16, further comprising the step of adjusting a time period for which said samples are heated. 24. A method of heat seal testing as recited in claim 16, further comprising the step of adjusting a time period for which said samples are clamped. 25. A method of heat seal testing as recited in claim 24, further comprising the step of adjusting a time period delay after said two samples are un amped. 26. A method of heat seal testing as recited in claim 25, further comprising the step of separating said sealed samples automatically.

Inventors: GIBBONS CHARLES E, LOMAX DOYLE, RAINES RUSSELL S, WATSON CARTER M, WHILLOCK ALLAN A, GIBBONS, CHARLES, E., LOMAX, DOYLE, RAINES, RUSSELL, S., WATSON, CARTER, M., WHILLOCK, ALLAN, A.
Applicants: INT PAPER CO, INTERNATIONAL PAPER COMPANY
Application year: 1996
Main classification: G01N3
IPC codes: B29C65, G01N19