Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-03-15
2001-03-06
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S228000
Reexamination Certificate
active
06197136
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of setting heat-sealing conditions of a thermoplastic sheet.
Heat-sealing is now widely utilized for sealing the opening of containers, making bags, and so on. The degree of heat seal ranges from separable bonding to complete sealing so as not to pass vapors and microorganisms. There are various factors which influence heat-sealing, such as material to be heat-sealed, designed heat seal strength, the type and seal of a heat sealer, line speed, and ambient temperature. However, when these factors are fixed, i.e. when heat-sealing is is conducted as to a predetermined sheet in a predetermined factory, the heat-sealing conditions depend on heat-sealing temperature and pressing period.
Heretofore, the heat-sealing temperature and pressing period were set empirically by repeating trial and error using a real machine. That is, by using a lot of real material with labor, a heat-sealing test was repeated with the varying of the heat-sealing temperature and pressing period in a wide range, and the heat sealed samples thus obtained were evaluated by JIS method(s), specially tensile strength (JIS Z 0238) and visual inspection. Through the test period, industrial production must be stopped, and nevertheless, the heat sealing conditions thus designed were not so accurate. As a result, the heat-sealing conditions were set slightly higher which tend to induce thermal damages at the heat sealed part.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method of setting heat-sealing conditions easily and accurately by a compact tester using only a small amount of real material and without stopping of industrial production.
In order to achieve the above object, the inventor investigated earnestly, and devised a compact heat-sealing tester having a pair of heating blocks which controls its surface temperature with high accuracy and nips to heat-seal an object and a temperature microsensor which is inserted between heat-sealing surfaces of the object. He further investigated, and found that, by attaching a surface cover material to the heating face which is the same as the surface cover material of a real heat sealer, substantially the same heat-sealing conditions as the real heat sealer can be allowed to occur, and by tracing the temperature at just the part to be heat-sealed, the heat-sealing conditions of the real heat sealer can be seen. The inventor further found that, the above technique can be generalized and applicable to other type heat sealers, e.g. one heater type, simulation of double step heat sealing, etc.
The present invention has been achieved based on the above findings, and provides:
A method of setting heat-sealing conditions which comprises.
(1) using a pressing and heating apparatus having two faces which face each other, at least one face thereof being movable toward the other face to nip an object to be heat-sealed, at least one face being provided with a heating means, and at least a temperature of one face being measured,
(2) providing a surface cover material to a heating face which is the same material as a surface cover material of a real heat sealer to be used,
(3) inserting a minute temperature sensor between heat-sealing surfaces of the object to be heat-sealed,
(4) locating the object between the two faces,
(5) heating the face provided with a heating means at a temperature exceeding the fusing point of the surface to be heat-sealed of the object,
(6) moving the movable face toward the other face to nip the object,
(7) measuring a time course of temperature at a part to be heat-sealed of the object, and,
(8) setting a pressing period of the real heat sealer as the time course of temperature being the same as the time course of the above step (7) at the temperature of the step (5).
In heat-sealing, an important factor is the initiation of fusion at the par-t to be heat-sealed, i.e. the surfaces to be heat-sealed. Using the above device, the inventor devised a simple and accurate method for determining the initiation of fusion at the part to be heat-sealed, which comprises differentiating the time course obtained in the step (7) twice, and the fusing point is at the position where the difference value changes from minus to plus.
REFERENCES:
patent: 4346196 (1982-08-01), Hoh et al.
patent: 5616199 (1997-04-01), Jurrius et al.
Crispino Richard
Flynn ,Thiel, Boutell & Tanis, P.C.
Koch, III George R.
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