US20100107568A1

US20100107568A1 - Method and apparatus for heat-sealing container

Info

Publication number: US20100107568A1
Application number: US12/450,792
Authority: US
Inventors: Shoichi Inaba; Hironori Kobayashi; Yoshinori Asada
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Group Holdings Ltd
Priority date: 2007-04-11
Filing date: 2007-04-18
Publication date: 2010-05-06
Also published as: KR20090128538A; CN101678902A; JPWO2008129679A1; JP5200266B2; WO2008129679A1

Abstract

A heat welding member 23 of a seal head 21 formed in the shape of a flange portion 11 a of a container 10 is heated by high frequency induction heating and a cap 12 is welded by pressing the heated seal head 21. By using the seal head 21 comprising the heat welding member 23 having a shape necessary for sealing the cap 12, influences by temperature drop and inflation of gas in a head space can be prevented and sealing at a high speed and in a stable manner can be achieved.

Description

TECHNICAL FIELD

This invention relates to a method and an apparatus for heat-sealing a container and, more particularly, to a method and an apparatus capable of carrying out heat-heating at a high speed and in a stable manner in a case where a cap in the form of a film should be heat-sealed to a container main body made of paper or synthetic resin and formed in the shape of a cup.

BACKGROUND ART

A container in which a cap in the form of a film is heat-sealed on a container main body made of paper or synthetic resin and formed in the shape of a cup is used broadly as a container for food etc., as, for example, a container for jelly, baby food, viscous food such as soup or miso or cooked food.
For sealing a container main body and a cap in such a container, heat-sealing which carries out sealing by heating using a seal head is generally used.
As such heat-sealing method, Japanese Patent Application Laid-open Publication No. 2004-250027 discloses a method in which a cap is conveyed and placed on a container by cap pressing and conveying means disposed above container conveying means and, while the state in which the cap is in close contact with the container is maintained, induction heating is carried out by a high frequency seal head which is disposed above the cap without contacting the cap. According to this method, sealing can be achieved at a high speed without vertically moving the seal head or container.
Japanese Patent Application Laid-open Publication No. 11-20801 discloses high speed adhesion between a cap and a container by using of both heating with a heater cartridge and high frequency induction heating or supersonic vibration heating.
Japanese Patent Application Laid-open Publication No. 58-19536 discloses that, as shown in its FIG. 4, a pressing and heating belt 4 in which a metal member 2 is sandwiched between a heat resisting member 3 is provided above a container conveying belt conveyer 1 in a manner to move synchronously in parallel with the conveyer 1 and that a high frequency induction heating coil 5 is disposed in the belt 4 to high frequency induction heating the pressing and heating belt 4 so that a cap 7 placed on a container 6 may be sealed.

SUMMARY OF THE INVENTION

In carrying out sealing at a high speed by using one of the above described heat-sealing methods, if capacity of a heat receiving and imparting portion of a seal head, i.e., heat capacity, is small, temperature of the seal head tends to drop during sealing when the seal head is pressed against the cap and heating of the cap is made in a peripheral portion of the cap and, therefore, a seal head having a more or less lump shape and having a large heat capacity must be used.
If, however, one attempts to carry out sealing at a high speed by using a large seal head, not only the peripheral portion of the cap but also the central portion of the cap tend to be heated and therefore temperature of the central portion tends to rise and, as a result, gas in a head space of the container is inflated in a stage before the welded portion is completely solidified and wrinkles are produced in the cap thereby causing difficulty in sealing.
Moreover, if one attempts to carry out sealing at a high speed i.e., in a short period of time, by elevating temperature of the seal head, the cap tends to adhere to the seal head thereby causing difficulty in sealing and, in this case, limitation is posed on the type of material which can be used as the cap.
Further, in the case of Japanese Patent Application Laid-open Publication No. 2004-250027 in which the cap is heated by high frequency induction heating, the cap must be heated directly and, therefore, sealing by heating can be made only in the case that the cap is made of metal.
Furthermore, in all of the above described methods, the entire surface of the cap is heated and, as a result, gas in the head space of the container is inflated thereby causing difficulty in sealing.
The present invention has been made in view of these problems of the prior art methods. It is an object of the invention to provide a method and an apparatus for heat-sealing a container capable of carrying out sealing at a high speed and in a stable manner regardless of material of a cap.
For achieving the above described object of the present invention, in the first aspect of the invention, there is provided a method for heat-sealing a container by sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container comprising a step of high frequency induction heating a seal head formed in the shape of the flange portion of the container and pressing the cap with the heated seal head to weld the cap to the container.
According to this method for heat-sealing a container, since the seal head formed in the shape of the flange portion of the container is high frequency induction heated and the heated seal head is pressed on the cap to weld the cap, by using a seal head having a shape necessary for sealing the cap, influence by dropping in the temperature and inflation of gas in the head space can be prevented and sealing at a high speed in a stable manner can be achieved.
In the second aspect of the invention, there is provided a method for heat-sealing a container as defined in the first aspect further comprising a step of cooling the seal head while the heated seal head is pressing the cap.
According to this method for heat-sealing a container, the seal head is cooled while the heated seal head is pressing the cap. Since pressing is finished after the seal head is cooled, even if sealing temperature is raised, adhering of the cap to the seal head can be prevented and sealing at a high speed and in a stable manner can be achieved even in a higher degree.
In the third aspect of the invention, there is provided a method for heat-sealing a container as defined in the second aspect wherein cooling of the seal head is made by supplying a cooling medium into the seal head.
According to this method for heat-sealing a container, since cooling of the seal head is made by supplying a cooling medium into the seal head, cooling of the seal head can be made easily.
In the fourth aspect of the invention, there is provided a method for heat-sealing a container by sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container with a seal head comprising a heating ring formed along the shape of the flange portion and a high frequency induction heating coil provided on the inside of the heating ring via magnetic shielding plates, said method comprising a step of high frequency induction heating the heating ring with the high frequency induction heating coil and pressing the cap with the heating ring to weld the cap to the container.
According to this method for heat-sealing a container, the seal head with which the cap is heat welded on the flange portion provided in the opening portion of the container comprises the heating ring formed along the shape of the flange portion and the high frequency induction heating coil provided on the inside of the heating ring via magnetic shielding plates and the heating ring is high frequency induction heated with this high frequency induction heating coil and pressed on the cap to weld the cap. Therefore, by using a seal head having a heating ring having a shape necessary for sealing the cap and concentrically heating the heating ring shielded by the magnetic shielding plates, influence by dropping in the temperature and inflation of gas in the head space can be prevented and sealing at a high speed in a stable manner can be achieved.
In the fifth aspect of the invention, there is provided a method for heat-treating a container as defined in the fourth aspect wherein supply of electricity to the high frequency induction heating coil is stopped after the heating ring has been heated to a predetermined temperature and then pressing with the heating ring is continued for a predetermined period of time.
According to this method for heat-sealing a container, since supply of electricity to the high frequency induction heating coil is stopped after the heating ring has been heated to a predetermined temperature and then pressing with the heating ring is continued for a predetermined period of time, heating with the heating ring which has been heated to a predetermined temperature is continued for a predetermined period of time necessary for heat welding and, therefore, sealing can be made in a sealing state which becomes stable and proper in a short period of time.
In the sixth aspect of the invention, there is provided a method for heat-treating a container as defined in the fourth or fifth aspect wherein the heating ring is cooled while pressing with the heating ring is continued.
According to this method for heat-sealing of a container, since the heating ring is cooled while pressing with the heating ring is continued, even if the temperature is raised, pressing is finished after the heating ring is cooled and, therefore, adhering of the cap to the heating ring can be prevented and sealing at a high speed and in a stable manner can be achieved even in a higher degree.
In the seventh aspect of the invention, there is provided a method for heat-sealing a container as defined in the sixth aspect wherein the heating ring has a hollow portion and cooling of the heating ring is made by supplying a cooling medium into the hollow portion.
According to this method for heat-sealing a container, since the heating ring has a hollow portion and cooling of the heating ring is made by supplying a cooling medium into the hollow portion, cooling of the heating ring at a high temperature can be made easily in a short period of time.
In the eighth aspect of the invention, there is provided a method for heat-sealing a container as defined in the seventh aspect wherein cooling of the heating ring with the cooling medium and supplying of the cooling medium are made by providing a plurality of cooling medium supplying and exhausting openings in the hollow portion of the heating ring and supplying and exhausting the cooling medium from a different one of the supplying and exhausting openings in a predetermined order or at random.
According to this method for heat-sealing a container, cooling of the heating ring with the cooling medium and supplying of the cooling medium are made by providing a plurality of cooling medium supplying and exhausting openings in the hollow portion of the heating ring and supplying and exhausting the cooling medium from a different one of the supplying and exhausting openings in a predetermined order or at random. By supplying and exhausting the cooling medium from a different one of the supplying and exhausting openings in a predetermined order or at random, the heating ring can be cooled to a uniform temperature whereby heating temperature for next heating can be made uniform and heat-sealing can be made in a stable manner.
In the ninth aspect of the invention, there is provided an apparatus for heat-sealing a container comprising a seal head for sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container, said seal head comprising a seal head main body, a heat welding member provided in the seal head main body and formed in the shape of the flange portion, and a high frequency induction heating coil provided in the seal head main body for high frequency induction heating the heat welding member.
According to this apparatus for heat-sealing a container, since the apparatus comprises the heat welding member provided in the seal head main body and formed in the shape of the flange portion, and the high frequency induction heating coil provided in the seal head main body for high frequency induction heating the heat welding member, by heating the heat welding member in the form of the flange portion with the high frequency induction heating coil, the heat welding member can be heated to a necessary temperature for sealing in a short period of time and, therefore, influence of dropping in the temperature and inflation of gas in the head space can be prevented and high-speed and stable sealing can be achieved with a seal head having a shape necessary for sealing of the cap.
In the tenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the ninth aspect wherein the heat welding member comprises a cooling medium flow-path which enables the heat welding member to cool while pressing of the heat welding member on the cap is maintained.
According to this apparatus for heat-sealing a container, since the heat welding member comprises a cooling medium flow-path which enables the heat welding member to cool while pressing of the heat welding member on the cap is maintained, cooling of the seal head can be made easily and, therefore, even if the temperature is raised, by finishing pressing after the seal head is cooled, adhering of the cap to the seal head can be prevented and sealing at a high speed and in a stable manner can be achieved even in a higher degree.
In the eleventh aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the ninth or tenth aspect wherein the heat welding member comprises a non-welding member on a surface of the heat welding member which presses the cap.
According to this apparatus for heat-sealing a container, since the heat welding member comprises a non-welding member on a surface of the heat welding member which presses the cap, even if the sealing temperature is raised, adhering of the cap to the seal head can be prevented by covering of the seal head and sealing at a high speed and in a stable manner can be achieved even in a higher degree.
In the twelfth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the tenth or eleventh aspect wherein the heat welding member comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap.
According to this apparatus for heat-sealing a container, since the heat welding member comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap, heating for sealing a next cap can be made in an even shorter period of time whereby sealing can be made at a high speed and in a stable manner.
In the thirteenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in any of the ninth-twelfth aspects wherein the seal head main body comprises temperature holding means for holding heating temperature of the heat welding member.
According to this apparatus for heat-sealing a container, since the seal head main body comprises temperature holding means for holding heating temperature of the heat welding member, a temperature which becomes a basis of temperature range of heating and cooling can be maintained and, therefore, when heating and cooling are repeated, sealing can be made at a high speed and in a stable manner in an even shorter period of time.
In the fourteenth aspect of the invention, there is provided an apparatus for heat-sealing a container comprising a seal head and sealing the container by heating the seal head and pressing a cap placed on a flange portion of an opening portion of the container with the heated seal head to heat-weld the cap to the container, said seal head comprising a heating ring shaped along the shape of the flange portion, and a high frequency induction heating coil wound in a plurality of windings provided on the inside of the heating ring and held between magnetic shielding plates.
According to this apparatus for heat-sealing a container, since apparatus for heat-sealing the container comprising the seal head and sealing the container by heating the seal head and pressing the cap placed on the flange portion of the opening portion of the container with the heated seal head to heat-weld the cap to the container, said seal head comprising the heating ring shaped along the shape of the flange portion, and the high frequency induction heating coil wound in a plurality of windings provided on the inside of the heating ring and held between magnetic shielding plates, by heating the heating ring shaped along the shape of the flange portion with the high frequency induction heating coil held between the magnetic shielding plates, the heating ring can be heated concentrically to a temperature necessary for sealing the cap in a short period of time and, therefore, influence of dropping in the temperature and inflation of gas in the head space can be prevented and high-speed and stable sealing can be achieved with a seal head having a shape necessary for sealing of the cap.
In the fifteenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the fourteenth aspect wherein the heating ring of the seal head comprises a hollow portion which is a cooling medium flow-path capable of cooling the heating ring while the heating ring is pressed on the cap and a plurality of cooling medium supplying and exhausting openings provided in the cooling medium flow-path which can change a supplying and exhausting position of the cooling medium.
According to this apparatus for heat-sealing a container, the heating ring of the seal head comprises the hollow portion which is the cooling medium flow-path capable of cooling the heating ring while the heating ring is pressed on the cap and a plurality of cooling medium supplying and exhausting openings provided in the cooling medium flow-path which can change a supplying and exhausting position of the cooling medium. By making the heating ring hollow and using the inside of the hollow portion as the cooling medium flow-path, and carrying out cooling while changing the supplying and exhausting position of the cooling medium among the plurality of cooling medium supplying and exhausting openings, adhering of the cap to the heating ring can be prevented and high-speed and stable sealing can be made even in a higher degree and, further, uniform cooling and uniform next heating can also be realized.
In the sixteenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the fourteenth or fifteenth aspect claim wherein the heating ring comprises a non-welding member on a surface of the heating ring which presses the cap.
According to this apparatus for heat-sealing a container, since the heating ring comprises a non-welding member on a surface of the heating ring which presses the cap, even if the sealing temperature is raised, adhering of the cap to the heating ring can be prevented by covering of the heating ring and sealing at a high speed and in a stable manner can be achieved even in a higher degree.
In the seventeenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in the fifteenth or sixteenth aspect wherein the heating ring comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap.
According to this apparatus for heat-sealing a container, since the heating ring comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap, heating for sealing a next cap can be made in an even shorter period of time and sealing can be made at a high speed and in a stable manner.
In the eighteenth aspect of the invention, there is provided an apparatus for heat-sealing a container as defined in any of the fourteenth-seventeenth aspects wherein the seal head comprises temperature holding means for holding heating temperature of the heating ring.
According to this apparatus for heat-sealing a container, since the seal head comprises temperature holding means for holding heating temperature of the heating ring, a temperature which becomes a basis of temperature range of heating and cooling can be maintained and, therefore, when heating and cooling are repeated, sealing can be made at a high speed and in a stable manner in an even shorter period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view showing a container used in an embodiment of the container heat-sealing method and apparatus of the present invention.

FIG. 2 a vertical section showing an embodiment of the container heat-sealing method and apparatus of the present invention.

FIG. 3 is a schematic plan view showing an embodiment in which the container heat-sealing method and apparatus of the invention are applied to a rotary type heat-sealing apparatus carrying out high speed continuous heat-sealing.

FIG. 4 is a schematic view of another embodiment of the container heat-sealing method and apparatus of the present invention.

FIG. 5 is a schematic vertical section of the embodiment shown in FIG. 4.

FIG. 6A is an explanatory view of heating and cooling processes of an embodiment of the container heat-sealing method and apparatus and FIG. 6B is an explanatory view of change in temperature of this embodiment.

FIG. 7A is a schematic view of the prior art heat-sealing apparatus and FIG. 7B is a cross sectional view of this apparatus.

FIG. 8 is a sectional view showing another example of the heating ring of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Description will now be made in detail about embodiments of the present invention with reference to the accompanying drawings.
FIGS. 1 and 2 show an embodiment of the container heat-sealing method and apparatus. FIG. 1 is an exploded view of the container and FIG. 2 is a vertical sectional view of the embodiment of the heat-sealing apparatus.
In this container heat-sealing apparatus (hereinafter referred simply to as “heat-sealing apparatus”) 20, as shown in FIG. 1, a container 10 is composed of a container main body 11 and a cap 12 which covers the container main body 11. This container main body 11 is formed in the shape of a cup and has, in the periphery of an upper end opening portion, a flange portion 11 a which extends horizontally outwardly. The cap 12 has, in its outer peripheral portion, a heat seal portion 12 a which extends horizontally corresponding to the flange portion 11 a. This annular heat seal portion 12 a is formed integrally on the inner side thereof with a recessed cap portion 12 b which projects downwardly to be positioned in the container. As the cap 12, a normal flat plate type cap including the heat seal portion 12 a and is not formed in the shape of a recessed cap portion may also be used.
The heat-sealing apparatus 20 which heat-seals the container main body 11 and the cap 12 together has, as shown in FIG. 2, a seal head 21.
A seal head main body 22 of the seal head 21 is provided with a heat welding member 23 having the same shape as and corresponding to the shape of the heat seal portion 12 a of the cap 12, for example, a hollow ring shape, in such a manner that the lower surface of the heat welding member 23 is exposed. The hollow portion 23 a of the heat welding member 23 constitutes a flow-path of a cooling medium, e.g., cooling water and a cooling medium pipe 24 is connected to the flow-path to supply and exhaust the cooling medium.
This heat welding member 23 is made of a material, e.g., metal, which can be heated by high frequency induction heating.
A high frequency heating coil 25 is disposed above the heat welding member 23 of the seal head main body 22 of the seal head 21. The coil 25 has windings of, e.g., three windings in a horizontal plane parallel to the upper surface of the heat welding member 23 and is connected to a high frequency power source through an electric current supply member (feeder) 26 connected to one end portion of the coil 25. This high frequency heating coil 25 is also made hollow and a cooling medium such as cooling water can be supplied to and exhausted from this hollow portion via a cooling medium pipe 27.
A ferromagnetic substance member 28 is provided in the seal head main body 22 in a manner to surround the heat welding member 23 and the high frequency heating coil 25. The seal head 21 thus composed can be moved vertically and moved for pressing by means of an unillustrated elevating and pressing device.
In this heat-sealing apparatus 20, a container support 29 is provided below the seal head 21 to support the lower surface of the flange portion 11 a of the container main body 11.
The cap 12 is placed on the container main body 11 which is supported by the container support 29 and is filled with contents and, after the heat seal portion 12 a of the cap 12 is superposed on the flange portion 11 a of the container main body 11, the cap 12 is pressed between the container support 29 and the seal head 21.
Description will now be made about the operation of the heat-sealing apparatus 20 having the above described structure as well as the method for heat-sealing a container.
This type of heat-sealing apparatus 20 is normally provided on a filling line of the container 10 and is used for high speed continuous production according to which contents are filled in the container main body 11 and then the cap 12 is placed on the container main body 11 and sealed by heat-sealing. Description will however be made with respect to an example in which a single container is heat-sealed.
After contents are filled in the container main body 11 of which the flange portion 11 a is supported by the container support 29, the cap 12 is placed on the container main body 11 and the heat seal portion 12 a of the cap 12 is superposed on the flange portion 11 a of the container main body 11 with the recessed cap portion 12 b projecting into the head space of the container main body 11 thereby reducing the capacity of the head space. In a case where a normal flat type cap having no recessed cap portion is used as the cap, the cap 12 is placed on the container main body 11 in such a manner that the heat seal portion 12 a is superposed on the flange portion 11 a.
In the seal head 21, in parallel to mounting of the cap 12, high frequency current is supplied from the high frequency current source to the high frequency heating coil 25 through the electric current supply member 26 to heat the surface of the heat welding member 23. This heating by the high frequency heating coil 25 is high frequency induction heating according to which high frequency flux generated by high frequency current penetrates the heat welding member 23 which is the object of heating and thereby induces an eddy current having a very high density which heats the surface of the heat welding member 23.
The temperature of heating of this seal head 21 will suffice if the container main body 11 and the cap 12 which constitute the container 10 to be welded by heat-sealing are welded and sealed together. Temperature control is made by determining the temperature of heating at a proper value depending upon the materials of the container main body 11 and the cap 12. By way of example, in a case where the cap is made of polyethylene terephthalate resin or a case where the cap is made of stacked layers and polypropylene resin is used as an inner sealant material, temperature required for heat-sealing usually is within a range from 180° C. to 220° C.
The seal head 21 which has been heated to a temperature required for heat-sealing is moved by the unillustrated elevating and pressing device to press the heat seal portion 12 a of the cap 12 to the flange portion 11 a of the container main body 11 which is supported by the container support 29 with the cap 12 placed thereon.
Since the heated heat welding member 23 of the seal had 21 has the same shape as the shape of the flange portion 11 a and the heat seal portion 12 a, a portion which is necessary for heat-sealing only is heated and pressed and heat-sealing is made at a predetermined temperature.
In the heating by this seal head 21, the central portion (the recessed portion 12 b) of the cap 12 is not directly heated by virtue of the shape of the heat welding member 23 and the shape of the cap 12 having the recessed portion 12 b but the flange portion 11 a and the heat seal portion 12 a only are directly heated and, therefore, even heat-sealing is made at a high temperature, inflation of gas in the head space of the container main body 11 can be held to the minimum and expansion of the cap 12 can also be prevented so that failure in sealing due to these causes can be prevented. Even if the cap 12 is formed in a flat plate shape, direct heating of its central portion can be prevented.
Then, cooling water as the cooling medium is supplied to the hollow portion 23 a of the heat welding member 23 of the seal head 21 through the cooling medium pipe 24 for cooling the heat welding member 23 compulsorily while the heat welding member 23 is kept pressed to the heat seal portion 12 a of the cap 12. The seal head 21 then is elevated by the elevating and pressing device and heat-sealing of one container 10 is thus completed.
Since pressing is finished after the heat welding member 23 is cooled in the above described manner, even if the heat-sealing is made at a high temperature, adhering of the cap 12 (i.e., a covering material of the cap such as a heat-sealing film) to the surface of the heat welding member 23 can be prevented and, therefore, high speed and stable heat-sealing can be achieved. Accordingly, materials which have been said to have difficulty in heat welding such as polyester resins e.g., polyethylene terephthalate and polyethylene naphthalate and polyamide resins e.g., nylon can be used for heat-sealing whereby the scope of materials to which heat-sealing is applicable can be broadened.
By forming a cover layer 30 made of a material which can prevent heat welding of the heat seal portion 12 a of the cap 12, e.g., fluorine containing resin or polyimide on the surface of the heat welding member 23 which contacts the heat seal portion 12 a of the cap 12, adhering of the cap 12 can be completely prevented.
For preparing for heat-sealing of a next container, cooling medium exhausting means 31 may be provided for exhausting the cooling medium which was supplied to the hollow portion 23 a of the heat welding member 23 so that next heating may be made easily and in a short period of time. As this cooling medium exhausting means 31, for example, a changeover valve 32 may be provided in the cooling medium pipe 24 to enable supply of a fluid 33, e.g., compressed air, which has a smaller heat capacity than the cooling medium so that the cooling medium may be replaced by air simultaneously with exhaustion and recovery of the cooling medium from the hollow portion 23 a of the heat welding member 23.
By replacing the cooling medium in the hollow portion 23 a of the heat welding member 23 by air having a smaller heat capacity than the cooling medium such as cooling water, heating time can be shortened and heat-sealing thereby can be made at a higher speed.
For shortening heating time until next heat-sealing after cooling of the seal head 21, an electric heater 34 which constitutes the temperature holding means may be provided adjacent to the heat welding member 23 of the seal head 22 and temperature may be controlled so that, after temperature is lowered to a value at which adhering of the cap 12 can be prevented, the temperature will not be lowered further so that a temperature which becomes a basis of temperature range of heating and cooling, i.e., the lowest temperature in the temperature range, can be maintained.
By this arrangement, even when high frequency induction heating of the heat welding member 23 of the seal head 21 is made with the high frequency heating coil 25, temperature is maintained at the lowest temperature required for heat-sealing by the electric heater 34 or the like constituting the temperature holding means and, therefore, heating may be made on the basis of this lowest temperature in the temperature range, i.e., heating starting temperature whereby the heat welding member 23 can be heated to the heat-sealing temperature in a shorter period of time.
In a case where high-speed continuous heat-sealing is made by using such heat-sealing apparatus 20, a rotary type heat-sealing apparatus 40 (hereinafter referred simply to as “heat-sealing apparatus 40) as shown in the schematic plan view of FIG. 3, for example, is used.
In this heat-sealing apparatus 40, a container main body supply unit A of a rotary type container main body conveying apparatus 41 which conveys the container main body 11 filled with contents conveys the container main body 11 to a cap supply position B while replacing the head space of the container main body 11 with inert gas or other gas. At this cap supply position B, the cap 12 which is conveyed from a cap stack position C by a cap conveying apparatus 42 is placed on the container main body 11 and the container main body 11 then is conveyed to a heating position D of the container main body conveying apparatus 41 by moving in a rotating locus.
At this heating position D, the seal head 21 which is induction heated by the high frequency induction coil 25 is lowered to press and heat the heat seal portion 12 a of the cap 12 and conveys the container main body 11 to a cooling position E in a rotating locus while maintaining this pressing state.
At the cooling position E, cooling water is supplied as the cooling medium from the cooling medium pipe 24 to the hollow portion 23 a of the heat welding member 23 to start cooling. Then, at a container discharge position F, the seal head 21 is elevated and the sealed container 10 is discharged.
Thus, heat-sealing of one container is completed in the rotary conveying of the container from the cap supply position B to the container discharge position F. Then, in the course of return movement from the container discharge position F to the heating position D, discharge of the cooling medium and high frequency induction heating necessary for next heat-sealing are made at a position such as position G.
According to the heat-sealing apparatus 40 combined with the rotary type conveying apparatus, heat-sealing can be finished by cooling while the seal head is maintained in a pressing state and, therefore, heat-sealing can be made continuously at a high speed. For example, according to this heat-sealing apparatus 40, high speed sealing of 600 containers per minute can be realized in contrast to the prior art apparatus in which heat-sealing speed is 20 to 30 containers per minute.
FIG. 4 is a schematic view of another embodiment of the invention and FIG. 5 is a schematic vertical section of the embodiment of FIG. 4.
A heat-sealing apparatus 20 for carrying out heat-sealing comprises, as shown in FIGS. 4 and 5, a seal head 122 which is mounted on the lower surface of an upper portion of an apparatus frame 121.
This seal head 122 comprises a seal head main body 123 which is composed of a cylindrical central member 123 a and an outer annular member 123 b. The central member 123 a and the annular member 123 b are attached concentrically to the apparatus frame 121 and an annular opening 123 c between the central member 123 a and the annular member 123 b constitutes an annular opening corresponding to the shape of the heat seal portion 12 a of the cap 12 which has the same shape as the flange portion 11 a of the container 10.
In the annular opening 12 c of the seal head 123, there is provided a heating ring 124 shaped along the heat seal portion 12 a which is the same as shape of the flange portion 11 a of the container main body 11.
The heating ring 124 is shaped in the form of a ring having a generally U-shaped section which opens upwardly and having outwardly extending flange portions 124 a at both inner and outer circumferences in the upper portion. The flange portions 124 a are in abutting engagement with stepped portions formed in the lower portions of the seal head main body 123. A bottom portion 124 b of the heating ring 124 is exposed in the lower surface thereof to the space below and held between a support plate 123 d in the shape of a disk and a support plate 123 e in the shape of a ring. By this arrangement, an annular space is formed with the apparatus frame 121, the seal head main body 123 and the heating ring 124.
The bottom portion 124 b of the heating ring 124 is made hollow to form a hollow portion 124 c which constitutes a flow-path of a cooling medium such as cooling water. A plurality of cooling medium supplying and exhausting openings 124 d are formed to communicate with the flow-path. In the illustrated example, two opening 124 d are formed at diagonal positions and these openings 124 d are respectively connected to cooling medium pipes 125 so hat the cooling medium can be supplied and exhausted from either of these pipes 125.
The heating ring 124 is made of a material, e.g., metal, which can be heated by high frequency induction heating.
In the annular space between the seal head main body 123 and the heating ring 124 of the seal head 122, a high frequency induction heating coil 126 is disposed in such a manner that it is held on both sides thereof between magnetic shielding plates 127. This high frequency induction heating coil 126 is wound, for example, in plural windings in both horizontal and vertical directions and is connected to a high frequency oscillator 128 via an electricity supply member (feeder) 128 a provided at the end of the coil 126. This high frequency induction heating coil 126 is made hollow to form a hollow portion and the cooling medium such as cooling water can be supplied to and exhausted from this hollow portion through an unillustrated cooling medium pipe.
Opposing the seal head 122, a container support 129 is provided in the lower portion of the apparatus frame 121 to support the lower surface of the flange portion 11 a of the container main body 11 of the container 10.
In this heat-sealing apparatus 20, an elevating and pressing device 130 is provided so that, after the cap 12 is placed on the container main body 11 which is supported by the container support 129 and filled with contents in such a manner that the heat seal portion 12 a of the cap 12 is superposed on the flange portion 11 a of the container main body 11, these portions can be pressed between the container support 129 and the seal head 122.
To this elevating and pressing device 130 is attached the container support through an air cylinder 131. By elevating the container support 129 and further stretching the rod, the heat seal portion 12 a of the cap 12 superposed on the flange portion 11 a of the container main body 11 is pressed between the container support 129 and the seal head 122.
Pressing of the heat-sealing portion 12 a of the cap 12 superposed on the flange portion 11 a of the container 11 may be made not only by vertically moving the container support 129 but also by vertically moving the seal head 122.
Description will now be made about the operation of the heat-sealing apparatus 20 constructed in the above described manner as well as the method for heat-sealing the container.
This type of heat-sealing apparatus 20 is normally provided on a filling line of the container 10 and is used for high speed continuous production according to which contents are filled in the container main body 11 and then the cap 12 is placed on the container main body 11 and sealed by heat-sealing. Description will however be made with respect to an example in which a single container is heat-sealed.
After contents are filled in the container main body 11 of which the flange portion 11 a is supported by the container support 129, the cap 12 is placed on the container main body 11 and the heat seal portion 12 a of the cap 12 is superposed on the flange portion 11 a of the container main body 11 with the recessed cap portion 12 b projecting into the head space of the container main body 11 thereby reducing the capacity of the head space. In a case where a normal flat type cap having no recessed cap portion is used as the cap, the cap 12 is placed on the container main body 11 in such a manner that the heat seal portion 12 a is superposed on the flange portion 11 a as shown in FIGS. 4 and 5.
In the seal head 122, in parallel to mounting of the cap 12, high frequency current is supplied from the high frequency oscillator 128 to the high frequency induction heating coil 126 through the electric current supply member 128 a to heat the surface of the bottom portion 124 b of the heating ring 124. This heating by the high frequency induction heating coil 126 is high frequency induction heating according to which high frequency flux generated by high frequency current penetrates the heating ring 124 which is the object of heating and thereby induces an eddy current having a very high density which heats the surface of the bottom portion 124 b of the heating ring 124.
The temperature of heating of this heating ring 124 of the seal head 122 will suffice if the container main body 11 and the cap 12 which constitute the container 10 to be welded by heat-sealing are welded and sealed together. Temperature control is made by determining the temperature of heating at a proper value depending upon the materials of the container main body 11 and the cap 12. By way of example, in a case where the cap is made of polyethylene terephthalate resin or a case where the cap is made of stacked layers and polypropylene resin is used as an inner sealant material, temperature required for heat-sealing usually is within a range from 180° C. to 220° C.
Then, by operating the air cylinder 131 of the elevating and pressing device 130, the container main body 11 which is supported by the container support and is covered with the cap 12 with the heat seal portion 12 a of the cap 12 being superposed on the flange portion 11 a of the container main body 11 is elevated and pressed to the seal head 122 in which the heating ring 124 has been heated to a temperature necessary for heat-sealing.
Since the heating ring 124 of the seal head 122 is formed along (i.e., in the same shape as) the shape of the flange portion 11 a and the heat seal portion 12 a, heat-sealing is performed at a predetermined temperature with the portion necessary for heat-sealing only being heated and pressed.
The heating and cooling processes by the heat-sealing apparatus 20 and temperature change in these processes are shown in FIGS. 6A and 6B. As shown in these figures, the heating ring 124 is heated to a predetermined temperature, e.g., 180° C. and then heating by the high frequency oscillator 128 is stopped and pressing by the elevating and pressing device 120 only is maintained.
In the heating by this seal head 122, the central portion (the recessed portion 12 b) of the cap 12 is not directly heated by virtue of the shape of the heating ring 124 and the shape of the cap 12 having the recessed portion 12 b but the flange portion 11 a and the heat seal portion 12 a only are directly heated and, therefore, even if heat-sealing is made at a high temperature, inflation of gas in the head space of the container main body 11 can be held to the minimum and expansion of the cap 12 can also be prevented so that failure in sealing due to these causes can be prevented. Even if the cap 12 is formed in a flat plate shape as shown in FIGS. 4 and 5, direct heating of its central portion can be prevented.
Since the heating ring 124 is formed in the annular shape having the U-shaped section, the heating ring 124 is thin and has a small heat capacity and therefore can be heated to a high temperature in a short-period of time with the high frequency induction coil 126 having plural windings in the horizontal and vertical directions. Moreover, drop in the temperature after stopping supply of electric current is relatively small and a predetermined temperature can be maintained whereby sealing can be achieved by maintaining pressing with the heating ring 124 for a period of time necessary for heat-sealing.
After heat welding by the heating ring 124 of the seal head 122 is made by maintaining pressing of the heating ring 124, cooling water as the cooling medium is supplied through the cooling medium pipe 125 to the cooling medium flow-path formed by the hollow portion 124 c of the heating ring 124 with one of the cooling medium supplying and exhausting openings 124 d being used as a supplying opening and another of the openings 124 d being used as an exhausting opening to compulsorily cool the heating ring 124. After the heating ring 124 is cooled to a predetermined temperature, the container support 129 is lowered by the elevating and pressing device 130 to complete heat-sealing of one container 10. Cooling of the heating ring 124 to a predetermined temperature is continued even after lowering of the container 10 and discharge of water (see FIG. 6A) to be described later is performed.
By this arrangement, since pressing is finished while the heating ring 124 of the seal head 122 is cooled, even if heating time is shortened by elevating the heating temperature, adhering of the cap 12 (i.e., the covering material of the cap such as a heat-sealing film) to the surface of the heating ring 124 of the seal head 122 can be prevented whereby high-speed and stable heat-sealing can be achieved. Besides, since the heating ring 124 is formed annularly and thin, it has a small heat capacity and therefore can be cooled in a short period of time.
FIG. 8 shows a modified example of the heating ring.
In the heating ring 224 of FIG. 8, the same component elements as those of the heating ring shown in FIG. 5 are designated by the same reference characters and description thereof will be omitted.
This heating ring 224 is divided in two portions of the upper portion and the lower portion. The upper portion 224 a is formed integrally with a central portion 123 a and is made of a synthetic resin, e.g., polyether ether ketone resin and the lower portion 224 b is made of metal. A cooling medium is supplied to an opening portion 226 between the upper portion 224 a and the lower portion 224 b. A gap between the upper portion 224 a and the lower portion 224 b is sealed with an O-ring 227. Reference character 228 designates a blank plug and reference character 229 designates a heating ring holder.
According to such heat-sealing apparatus 20, materials which have been said to have difficulty in heat welding such as polyester resins e.g., polyethylene terephthalate and polyethylene naphthalate and polyamide resins e.g., nylon which have a relatively high melting point can be used as the cap for heat-sealing whereby the scope of materials to which heat-sealing is applicable can be broadened. Additionally, thickness of the cap can be increased to such a degree that the invention is applicable to a cap formed by injection molding. Even in a case where the material of the cap is changed in the above described manner, by maintaining pressing of the heating ring 124 for a period of time after heating the heating ring 124 to a predetermined temperature until start of the cooling process with supply of electric current being stopped, temperature and time necessary for heat welding the material can be secured.
By forming, as shown in the enlarged view of FIG. 5, a cover layer 124 e which is made of a material such as fluoride resin or polyimide which can prevent heat welding of the heat seal portion 12 a of the cap 12 at least on the surface of heating ring 124 which contacts the heat seal portion 12 a of the cap 12, adhering of the cap 12 can be completely prevented.
For preparing for next heat-sealing of a container, the cooling medium which has been supplied to the hollow portion 124 c of the heating ring 124 may be discharged by providing an unillustrated cooling medium exhausting means whereby discharge of water can be made in a simple manner so that heating of the cooling water in the hollow portion 124 c in next heat-sealing will be obviated and heating of the heating ring 124 can be made easily and in a short period of time.
As this cooling medium exhausting means, for example, a changeover valve may be provided in the cooling medium pipe 125 to enable supply of a fluid such as compressed air which has a smaller heat capacity than the cooling medium so that air can replace the cooling medium while the cooling medium is discharged and recovered from the hollow portion 124 c of the heating ring 124.
According to this arrangement, by replacing the cooling medium in the hollow portion 123 a of the heat welding member 123 with air which has a smaller heat capacity than the cooling water used as the cooling medium, heating time can be shortened and high speed heat-sealing thereby can be realized.
For further shortening heating time until next heat-sealing after cooling of the seal head 122, an electric heater which constitutes the temperature holding means may be provided adjacent to the heat welding member 124 of the seal head 122 and temperature may be controlled so that, after temperature is lowered to a value at which adhering of the cap 12 can be prevented, the temperature will not be lowered further so that a temperature which becomes a basis of temperature range of heating and cooling, i.e., the lowest temperature in the temperature range, can be maintained.
By this arrangement, even when high frequency induction heating of the heat welding member 124 of the seal head 122 is made with the high frequency induction heating coil 126, temperature is maintained at the lowest temperature required for heat-sealing by the electric heater or the like constituting the temperature holding means and, therefore, heating may be made on the basis of this lowest temperature in the temperature range, i.e., heating starting time whereby the heat welding member 124 can be heated to the heat-sealing temperature in a shorter period of time.
Further, by supplying and exhausting the cooling medium through different ones of cooling medium supplying and exhausting openings 124 d when the heating ring 124 is cooled after finishing heat-sealing of a next container, drop of temperature in the portion of the heating ring 124 where the cooling medium enters and elevation of temperature in the portion of the heating ring 124 where the cooling medium exits can be prevented whereby uniform cooling can be ensured notwithstanding repeated heating and cooling. By this arrangement, temperature of the heating ring 124 by subsequent heating can be made uniform whereby heat-sealing can be made with a stable quality.
In the above described embodiment, two cooling medium supplying and exhausting openings 124 d are diagonally provided and cooling is made by changing the cooling medium supplying opening and the cooling medium exhausting opening alternately each time the container 10 is changed. Alternatively, more than two cooling medium supplying and exhausting openings may be provided and cooling may be made by changing the cooling medium supplying opening and the cooling medium exhausting opening in a predetermined order, or detecting temperature in some portions of the heating ring 124 and supplying and exhausting the cooling medium at a suitable position randomly so that distribution in the temperature will not be produced. Further alternatively, the cooling medium may be supplied simultaneously from plural positions and exhausted from plural positions or a single position or the cooling medium may be supplied from a single position and exhausted from plural positions.
In the above described embodiments, description has been made with respect to a case where the cap having a recessed cap portion or a flat cap portion is placed on the container main body having the shape of a cup. The shapes of the cap and the container main body are not limited to these shapes but other shapes such as a tray may be used as the shapes of the cap and the container main body.
In the above described embodiments, either the seal head or the container support is moved vertically to heat-seal a container during the heat-sealing process of the container. In these embodiments, the other of the seal head and the container support which has been described as moveing vertically in these embodiments may be moved vertically for heat-sealing.
Supply of the cooling medium may be omitted depending upon the material of the cap or the conditions of heating. In this case, time for the entire heat-sealing process may be shortened or heating time may be lengthened.
Since heat-sealing at a high speed can be made, drinks which have in the past been filled in a metal can or a PET bottle may be filled in the container used in the present invention and the container may be sealed at a high speed. Prepared food containing a solid food or viscous food may also be filled in the container used in the present invention and the container may be sealed at a high speed.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a method and an apparatus for heat-sealing a container. Particularly, in the case of heat-sealing a cap in the form of a film on a container main body in the form of a cup made of paper or a synthetic resin, heat-sealing can be made at a high speed in a stable manner.

Claims

1. A method for heat-sealing a container by sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container comprising a step of high frequency induction heating a seal head formed in the shape of the flange portion of the container and pressing the cap with the heated seal head to weld the cap to the container.

2. A method for heat-sealing a container as defined in claim 1 further comprising a step of cooling the seal head while the heated seal head is pressing the cap.

3. A method for heat-sealing a container as defined in claim 2 wherein cooling of the seal head is made by supplying a cooling medium into the seal head.

4. A method for heat-sealing a container by sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container with a seal head comprising a heating ring formed along the shape of the flange portion and a high frequency induction heating coil provided on the inside of the heating ring via magnetic shielding plates, said method comprising a step of high frequency induction heating the heating ring with the high frequency induction heating coil and pressing the cap with the heating ring to weld the cap to the container.

5. A method for heat-treating a container as defined in claim 4 wherein supply of electricity to the high frequency induction heating coil is stopped after the heating ring has been heated to a predetermined temperature and then pressing with the heating ring is continued for a predetermined period of time.

6. A method for heat-treating a container as defined in claim 4 wherein the heating ring is cooled while pressing with the heating ring is continued.

7. A method for heat-sealing a container as defined in claim 6 wherein the heating ring has a hollow portion and cooling of the heating ring is made by supplying a cooling medium into the hollow portion.

8. A method for heat-sealing a container as defined in claim 7 wherein cooling of the heating ring with the cooling medium and supplying of the cooling medium are made by providing a plurality of cooling medium supplying and exhausting openings in the hollow portion of the heating ring and supplying and exhausting the cooling medium from a different one of the supplying and exhausting openings in a predetermined order or at random.

9. An apparatus for heat-sealing a container comprising a seal head for sealing the container by heat welding a cap on a flange portion provided in an opening portion of the container, said seal head comprising a seal head main body, a heat welding member provided in the seal head main body and formed in the shape of the flange portion, and a high frequency induction heating coil provided in the seal head main body for high frequency induction heating the heat welding member.

10. An apparatus for heat-sealing a container as defined in claim 9 wherein the heat welding member comprises a cooling medium flow-path which enables the heat welding member to cool while pressing of the heat welding member on the cap is maintained.

11. An apparatus for heat-sealing a container as defined in claim 9 wherein the heat welding member comprises a non-welding member on a surface of the heat welding member which presses the cap.

12. An apparatus for heat-sealing a container as defined in claim 10 wherein the heat welding member comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap.

13. An apparatus for heat-sealing a container as defined in claim 9 wherein the seal head main body comprises temperature holding means for holding heating temperature of the heat welding member.

14. An apparatus for heat-sealing a container comprising a seal head and sealing the container by heating the seal head and pressing a cap placed on a flange portion of an opening portion of the container with the heated seal head to heat-weld the cap to the container, said seal head comprising a heating ring shaped along the shape of the flange portion, and a high frequency induction heating coil wound in a plurality of windings provided on the inside of the heating ring and held between magnetic shielding plates.

15. An apparatus for heat-sealing a container as defined in claim 14 wherein the heating ring of the seal head comprises a hollow portion which is a cooling medium flow-path capable of cooling the heating ring while the heating ring is pressed on the cap and a plurality of cooling medium supplying and exhausting openings provided in the cooling medium flow-path which can change a supplying and exhausting position of the cooling medium.

16. An apparatus for heat-sealing a container as defined in claim 14 wherein the heating ring comprises a non-welding member on a surface of the heating ring which presses the cap.

17. An apparatus for heat-sealing a container as defined in claim 15 wherein the heating ring comprises cooling medium exhausting means for exhausting the cooling medium in the cooling medium flow-path after cooling of the cap.

18. An apparatus for heat-sealing a container as defined in claim 14 wherein the seal head comprises temperature holding means for holding heating temperature of the heating ring.

19. A method for heat-treating a container as defined in claim 5 wherein the heating ring is cooled while pressing with the heating ring is continued.

20. An apparatus for heat-sealing a container as defined in claim 10 wherein the heat welding member comprises a non-welding member on a surface of the heat welding member which presses the cap.

21. An apparatus for heat-sealing a container as defined in claim 15 wherein the heating ring comprises a non-welding member on a surface of the heating ring which presses the cap.