U.S. patent application number 12/577809 was filed with the patent office on 2011-04-14 for container sealing machine for food packaging.
Invention is credited to David Lin, Irene H. Lin.
Application Number | 20110083810 12/577809 |
Document ID | / |
Family ID | 43853887 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110083810 |
Kind Code |
A1 |
Lin; David ; et al. |
April 14, 2011 |
Container Sealing Machine for Food Packaging
Abstract
A sealing machine for a fresh-keeping and cooking container is
provided. The sealing machine includes a lidding-film processing
unit, a bonding unit, and a heat-sealing unit. The lidding-film
processing unit includes die cutters and hot needles for forming
line-segment-shaped, spaced slits and dot-shaped
atmosphere-modifying breathing holes on a surface of a lidding film
passing through the lidding-film processing unit. The processed
lidding film then enters the bonding unit and is bonded with an
airtight sealing strip whose bottom is provided with adhesive.
Afterward, the lidding film bonded with the sealing strip enters
the heat-sealing unit so as to cover an opening of a container and
be heat-sealed to a heat-sealable rim of the opening. Thus, the
lidding film is processed and sealed to the container in a
continuous manner to simplify sealing of the container and removal
of scraps cut from the used lidding film.
Inventors: |
Lin; David; (Shanhua,
TW) ; Lin; Irene H.; (Shanhua, TW) |
Family ID: |
43853887 |
Appl. No.: |
12/577809 |
Filed: |
October 13, 2009 |
Current U.S.
Class: |
156/497 |
Current CPC
Class: |
B65B 61/184 20130101;
B65B 61/02 20130101; B65B 25/04 20130101; B65B 31/028 20130101 |
Class at
Publication: |
156/497 |
International
Class: |
B65B 51/10 20060101
B65B051/10 |
Claims
1. A sealing machine for a fresh-keeping and cooking container, the
sealing machine comprising a lidding-film processing unit, a
bonding unit for bonding an airtight sealing strip to a lidding
film, and a heat-sealing unit for covering an opening of the
container with the lidding film; wherein, in the lidding-film
processing unit, the lidding film is unwound and extended downward
to a table from a roll of the lidding film, and a perforating
assembly at the table is actuated to form line-segment-shaped,
spaced slits or dot-shaped atmosphere-modifying breathing holes at
predetermined positions on a surface of the lidding film passing
through the lidding-film processing unit; wherein, as the processed
lidding film enters the bonding unit, the airtight sealing strip is
unwound and extended downward from a roll of the airtight sealing
strip above a table of the bonding unit and is laid over the
lidding film passing through the bonding unit such that the
line-segment-shaped, spaced slits formed on the lidding film are
covered, the airtight sealing strip, whose bottom is provided with
adhesive, being bonded to the lidding film via a hot-press sealing
assembly at the table of the bonding unit; wherein, as the lidding
film bonded with the airtight sealing strip enters the heat-sealing
unit configured for sealing the opening of the container, the
container, which contains frozen or refrigerated food and is placed
in a supporting frame of a table of the heat-sealing unit, is
covered by the lidding film passing through the heat-sealing unit,
and the lidding film covering the container is sealed to a
heat-sealable rim of the opening of the container via a
heat-sealing assembly at the table of the heat-sealing unit while
scraps cut from the used lidding film are wound around a rewinding
spool at an opposite end of the heat-sealing unit; and wherein the
lidding film covering the opening of the container is processed and
sealed to the container in a continuous manner to effectively
simplify sealing of the container and removal of the scraps cut
from the used lidding film.
2. The sealing machine of claim 1, wherein the perforating assembly
of the lidding-film processing unit comprises hot needles.
3. The sealing machine of claim 1, wherein the perforating assembly
of the lidding-film processing unit comprises die cutters
configured for forming the line-segment-shaped, spaced slits.
4. The sealing machine of claim 1, wherein the perforating assembly
of the lidding-film processing unit comprises hot needles and die
cutters configured for forming the line-segment-shaped, spaced
slits.
5. The sealing machine of claim 1, wherein a protection shield is
provided outside and around the perforating assembly of the
lidding-film processing unit.
6. The sealing machine of claim 1, wherein a protection shield is
provided outside and around the hot-press sealing assembly of the
bonding unit of the sealing machine.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to a sealing machine for
sealing a food container and enabling the sealed container to
preserve the freshness of food contained therein in a modified
atmosphere and to automatically regulate the build up steam
pressure generated during microwave heating. More particularly, the
present invention relates to a sealing machine which provides a
continuous process of processing a lidding film, filling frozen or
refrigerated food into a container, and then sealing opening of the
container with the processed lidding film.
[0003] 2. Description of Related Art
[0004] A conventional sealing machine for sealing frozen or
refrigerated food is typically configured to work in the following
manner. A roll of pre-fabricated lidding film is provided from a
roll stock film unwinding set of the sealing machine. Meanwhile, a
container filled with food to be frozen or refrigerated is in place
at a sealing position of the sealing machine. When the sealing
machine is started, the lidding film is unwound and extended
downward from the roll of lidding film at the end of the sealing
machine so as to pass over the container. The lidding film covering
the container is hot-pressed and thus sealed to an opening of the
container by a sealing mechanism. After the sealing process, scraps
die cut from the edge of lidding film are wound up to a rewinding
spool located at an opposite end of the sealing machine. Thus, the
opening of the container containing the to-be-frozen or
to-be-refrigerated food is sealed.
[0005] In the early days, a commonly used technique to preserve the
freshness and quality of fruits and vegetables is to lower the
temperature of the Storage environment. In a low-temperature
environment, living fruits and vegetables have a reduced metabolic
rate, and in consequence the oxidation and consumption of organic
sugar, starch, and fat in the fruits and vegetables slow down,
which delays the ripening and yellowing of the fruits and
vegetables. In addition, it was found decades ago that the
metabolic rate of fresh fruits and vegetables can also be
decreased, and their shelf life increased, by adjusting oxygen and
carbon dioxide concentrations in the packaging area surrounding the
fruits and vegetables. In fact, the modified-atmosphere packaging
(MAP) technique is an application based on and integrated with the
refrigeration technique so as to enhance the effect of freshness
prolongation on fruits and vegetables by both refrigeration and
atmosphere modification. During the past few decades, studies on
freshness preservation, storage, and transportation in a modified
atmosphere packaging have thrived. Since different fruits and
vegetables have different structure characteristic, the outer
surface area of a leafy vegetable that is in contact with air and
available for breathing differs from that of a fresh vegetables
with a stem or root tuber. A leafy vegetable also has a different
metabolic respiration rate from a stem or root tuber. Likewise,
total oxygen demand and carbon dioxide emission vary from one
species to another. Generally speaking, leafy vegetables have
relatively large surface areas, require a relatively larger amount
of air for metabolic respiration, and consequently ripen and yellow
relatively faster. In order to slow down metabolic respiration, the
modified-atmosphere packaging technique requires that storage
temperature and oxygen concentration be low, and carbon dioxide
concentration be high. By contrast, a fresh vegetable with stem or
root tubers, which breathe only through their outer skin, have
lower oxygen demand, are less sensitive to the change of oxygen
concentration in the environment, and therefore have higher
tolerance to variations in temperature and oxygen and carbon
dioxide concentrations during storage and transportation. The
atmospheric environment contains approximately 20.9% of oxygen and
0.03% of carbon dioxide. If fresh fruits and vegetables are stored
in an environment whose temperature is adjusted to a refrigeration
temperature of 0.degree. C. to 5.degree. C., whose oxygen
concentration is lowered to 2% to 15%, and whose carbon dioxide
concentration is raised to 5% to 30%, the shelf life of the fruits
and vegetables can be extended significantly from three days to
more than ten days, which is helpful to long-term storage and
long-distance transportation and distribution of fruits and
vegetables in continental countries. For produce grower in areas of
capricious weather conditions and having high requirements for
freshness and quality, the development of packaging materials for
use in modified-atmosphere packaging application is important.
Hence, many countries have put great efforts into the research and
development of special packaging materials for fruits and
vegetables. Presently, freshness preservation techniques for fruits
and vegetables can be divided into two major categories, namely
controlled-atmosphere packaging (CAP) and modified-atmosphere
packaging (MAP). In controlled-atmosphere packaging, the various
gas concentrations in a packaged atmosphere are under an active
controllable method. More specifically, oxygen and carbon dioxide
concentrations in the packaged atmosphere are regulated and kept
constant by means of detection equipment and external supply of
oxygen and carbon dioxide. Therefore, fruits and vegetables stored
in such a packaged atmosphere have their respiration and metabolic
rates lowered in exchange for extended shelf life and high quality.
However, the control system, including hardware and software, for
controlled-atmosphere packaging is costly. On the other hand,
modified-atmosphere packaging is carried out by packaging fresh
fruits and vegetables with a special air-permeable packaging
material such that, due to metabolism and respiration of the fruits
and vegetables under a specific storage temperature, coupled with
the special gas permeability of the packaging material, oxygen and
carbon dioxide concentrations in the packaged atmosphere gradually
reach a dynamic equilibrium state and thus meet the required
fresh-keeping conditions. The cost of modified-atmosphere packaging
is lower than that of controlled-atmosphere packaging.
[0006] While the shelf life of fresh fruits and vegetables can be
extended by applying the hardware, software, and packaging
materials of the aforesaid two packaging techniques, neither of
these packaging techniques provides the dual function of the
packaging material disclosed in the present invention, namely
atmosphere modification for freshness preservation and automatic
regulating the build up hot steam pressure when the packaged fruits
and vegetables are directly heated by microwave. Generally, a
packaging material for preserving the freshness of fruits and
vegetables in a modified atmosphere has an oxygen permeability
ranging approximately from 20 to 200000 cc/(daym.sup.2atm25.degree.
C.). However, the overall air-regulating capacity of such a
packaging material for modified-atmosphere freshness preservation
is not enough to regulate the huge instantaneous amount of build up
hot steam generated when the packaged fruits and vegetables are
heated by microwave especially at the onset of boiling temperature;
the packaging material will burst and break when subjected to such
vast vapor. Polyethylene or polypropylene bags with a thinner gauge
made by their blown films are common packaging materials for fruits
and vegetables and have fresh-keeping and air-permeable properties.
These bags, though capable of modified-atmosphere freshness
preservation, are not suitable for use as closed packages microwave
heating because the bags cannot regulate and withstand the vast
amount of build up hot steam pressure generated instantly upon
microwave heating.
[0007] Fresh fruits and vegetables sealed in a closed container for
storage and transportation are basically living plants. When oxygen
in the container is continuous depletion, and carbon dioxide
concentration becomes too high, the fruits and vegetables sealed in
the container begin to rot, yellow, and produce unpleasant odor. In
order to prevent fruits and vegetables from rotting due to lack of
oxygen, the container is usually perforated by die cutting so as to
enable rapid exchange of oxygen between the interior of the
container and ambient atmosphere, thus allowing the living fruits
and vegetables to survive. When massive gas exchange takes place,
however, oxygen and carbon dioxide concentrations inside and
outside the container become virtually equal, namely 20.9% of
oxygen and 0.03% of carbon dioxide. Now that the fruits and
vegetables are stored substantially in an atmospheric environment
and are allowed to restore their normal respiration and metabolic
rates, the container has lost the ability to significantly extend
the shelf life of its content.
[0008] Nowadays, modified-atmosphere freshness preservation of
fruits and vegetables is mostly implemented via an air-permeable
mixed polymer material. The material is formed into an
air-permeable film by co-extrusion, film blowing, or a T-die
stretching technique. In addition to complexity of the
manufacturing process, the resultant film is also disadvantaged by
the fact that its oxygen permeability and carbon dioxide
permeability are not applicable to the modified-atmosphere
preservation of all fruits and vegetables. More importantly, the
resultant air-permeable film cannot be used to regulate the large
amount of high-temperature, high-pressure vapor generated in a
closed microwave-heated environment. There are many breathable
packaging materials on the market that have special
air-permeability for the preservation of fruits and vegetables but
are not suitable for use in a closed microwave-heated environment.
A few examples of these commercially available air permeable
packaging materials and their manufacturing technologies are
described as follows.
[0009] 1. A plastic material is blended and thoroughly mixed with
an inorganic powder. The blended mixture goes through a blowing or
T-die extrusion process and is stretched by a mono or two
directional stretching tenter so as to form an air-permeable film.
For instance, an inorganic powder of calcium carbonate
(CaCO.sub.3), titanium dioxide (TiO.sub.2), or aluminum oxide
(Al.sub.2O.sub.3) is evenly mixed with an organic polymer material
such as polyethylene, prior to being extruded into a film. Similar
techniques are disclosed in U.S. Pat. Nos. 3,679,540; 4,187,390;
4,350,655; 4,466,931; 4,777,073; and 5,340,646. While the resultant
film has special air-permeability and meets the requirements for
modified-atmosphere packaging, it generally does not qualify for
use in a closed package that is to be directly heated by microwave,
for the following reasons: 1) The film has not enough mechanical
strength. 2) The film has a low melting point. The material
commonly used for making the film is polyethylene or polypropylene,
both of which have low melting points. When mixed with a higher
percentage of inorganic powder, the elongation ratio of this higher
weight percentage of blended inorganic powder is limited. In
practice, with a higher solid content, the stretched film tends to
break during the stretching process, and the inorganic powder may
fall off easily. 3) The formula of the film often includes
additives such as a lubricant. The added lubricant or the aforesaid
inorganic powder may migrate to or contact with food during
microwave cooking and cause an undesirable effect on the human
body. Furthermore, the lubricant additive, such as wax, may produce
unpleasant odor during microwave heating. In short, the low
mechanical strength and low melting point prevent the film from
being used in a closed package that is directly heated by
microwave. Besides, due to not enough steam pressure regulating
ability, the film tends to extend excessively or even rupture when
subjected to continuous heating and huge instantaneous build up
steam pressure.
[0010] 2. A plastic resin material is blended with an additive
having a low molecular weight, such as mineral oil. After the film
is formed, the mineral oil is extracted by a special solvent. More
specifically, the plastic material is evenly mixed with the mineral
oil. Then, the mixture is converted into a film via a T-die or
through a film casting process. Furthermore, the mineral oil is
extracted and thus removed by the solvent, so as to produce an
air-permeable film. The principle of the foregoing manufacturing
process is to make a film having a porous structure out of a
mixture of incompatible materials and then remove a certain
ingredient by solvent extraction. Similar techniques are disclosed
in U.S. Pat. Nos. 3,378,507; 3,310,505; 3,607,793; 3,812,224;
4,247,498; 4,466,931; and 5,928,582. While a film thus formed has
special air-permeability and meets the requirements for
modified-atmosphere packaging, it is generally incapable of
regulating the large amount of high temperature, hot steam pressure
generated in a closed microwave-heated package and may rupture as a
result. Moreover, considerations must be made for the risk of
having residual mineral oil in contact with food, as well as for
the excessive extension and burst of the film under continuous high
temperature.
[0011] 3. Another air-permeable material, as taught by U.S. Pat.
No. 5,865,926, is made of an air-permeable non-woven fabric or
fibrous web. However, an air-permeable film produced by such a
method has a macroporous structure and is unsatisfactory in terms
of food packaging, taste, flavor preservation, and efficient use of
energy.
[0012] The packaging materials described above are capable of
modified-atmosphere freshness preservation but incapable of
automatically regulating the build up hot steam pressure generated
during microwave heating. To prevent the packaging materials from
bursting fracture due to the instantaneous huge build up hot steam
and pressure during microwave heating or other cooking means, it is
common practice to form pressure-releasing macro holes in the
packaging materials or trays by laser microperforation or machine
die cutting. Air-permeable packaging materials with macro holes,
whose diameters are often greater than 1 mm, can not be used in a
closed microwave-heated environment but, owing to their high
air-permeability, turn out to be high-permeable packaging
materials, which may lead to dehydration of the packaged food. In
practice, these macro-hole packaging materials fail to prolong the
shelf life of fresh fruits and vegetables. In addition, a packaging
material for fruits and vegetables that is perforated by die
cutting tends to have a air-permeability so high that not only are
the various gas concentrations around the packaged fruits and
vegetables substantially the same as those in the ambient
atmosphere, but also small insects and fungi are allowed easy
access through the holes. Furthermore, in case of overtime
microwave cooking, the macro holes may cause the food to lose
excessive moisture during the heating process and end up dry and
hard.
[0013] Although the foregoing air-permeable packaging materials and
their manufacturing methods are well known in the art, those
packaging materials do not serve the dual function of
modified-atmosphere freshness preservation and proper pressure
regulation in a closed microwave-heated environment. More
importantly, those packaging materials have a relative high
production costs.
BRIEF SUMMARY OF THE INVENTION
[0014] The inventor of the present invention has endeavored to
improve microwavable food-packaging materials and their production
processes. The present invention relates to the integration of a
sealing machine and a container for storing frozen or refrigerated
fresh or cooked food, thereby enabling the container to preserve
the freshness of its content and be directly heated by microwave.
The subject matter of the present invention has never been
disclosed in the above-cited prior art.
[0015] The present invention provides a novel design of a sealing
machine configured for sealing a container which contains food to
be frozen or refrigerated. According to the present invention, a
lidding film for covering an opening of a container is processed
and then sealed to the container in a continuous fashion so as to
simplify sealing of the container and removal of scraps cut from
the used lidding film. Heat-sealing the lidding film to a loaded
food container may have the following functional appeals: 1) Frozen
or refrigerated food can be completely sealed to prevent ice burn
which may otherwise result from prolonged frozen storage. Besides,
the food can be directly heated by microwave oven in the frozen
state and serve when cooked. 2) Fresh fruits and vegetables can be
refrigerated and kept fresh in a modified atmosphere packaging for
storage and transportation. The fruits and vegetables can also be
directly heated by microwave oven and serve when cooked. 3) Fresh
fruits and vegetables, such as fresh-cut produce which has been
washed, packaged, and vacuum pre-cooled, can stay fresh under
refrigeration and be eaten directly. There is no need to open the
lidding or to cut a hole to the lidding prior to microwave heating
to prevent the bursting fracture.
[0016] The present invention provides a sealing machine for
rendering a food container capable of modified-atmosphere freshness
preservation as well as automatic build up vast hot steam pressure
regulation during microwave heating. The sealing machine includes
hot needles configured for quantitatively controlling the diameter
and number of melted holes formed in a lidding film sealed to the
container. Consequently, the air-permeable composite lidding film
has a specific gas permeation capacity and is applicable to fresh
fruits and vegetables of different kinds and different weights for
extending their shelf life of freshness.
[0017] On the other hand, the lidding film is formed with
line-segment-shaped, spaced slits and provided with an airtight
sealing strip such that the container is completely air tight
during storage and transportation but can rapidly regulate the
large amount of high-temperature, high-pressure hot steam generated
instantly during microwave cooking, thereby preventing the
container from bursting. The amount of vapor that the
line-segment-shaped, spaced slits are capable of regulating is far
greater than the small gas permeation amount required for
preserving the freshness of fruits and vegetables in a modified
atmosphere. If the content of the container is frozen cooked food,
the hot needles of the sealing machine can be restrained from
operation; alternatively, the melted holes formed by the hot
needles are located in an area covered with the airtight sealing
strip. Thus, a totally air tight food package is formed, with the
airtight sealing strip covering the line-segment-shaped, spaced
slits, so as to prevent ice burn which may otherwise occur after a
long-term frozen storage period. This air tight structure is also
suitable for low vacuum packaging or inert gas purging packaging.
When food packaged in a container of this structure is heated by
microwave, the huge amount of hot steam generated instantaneously
is regulated by the plurality of line-segment-shaped, spaced slits,
thereby protecting the container from bursting. Meanwhile, water
and other liquids in the food are largely preserved during
microwave heating and prevented from splashing in the microwave
oven, thus reducing the time and water resource required for
cleaning the microwave oven.
[0018] More importantly, this packaging material provides a
reversible and automatic air permeation and pressure regulation
function. Before microwave heating, the packaging material has a
closed structure. During heating, the packaging material
automatically regulates steam pressure so as for food in the
container to undergo a continuously pressurized heating process
while the container and the packaging material are protected from
bursting. When cooled after microwave heating is stopped, the
packaging material substantially resumes its closed structure. This
pressure- and temperature-dependent reversible structure is
reusable and reheatable, which is a far cry from the conventional
food-packaging materials which must be pulled or cut open to the
packaging material before microwave heating.
[0019] The inventor of the present invention has also granted
several patents for the core techniques of microwavable
food-packaging film materials. The disclosed packaging film can be
further integrated and benefit the present invention. These patents
include Japanese Patent No. 3747004; U.S. Pat. Nos. 7,077,923 and
7,208,215; Korean Patent No. 0536896; Canadian Patent No. 2381146;
and Australian Patent No. 780966. The present invention further
integrates the mechanical hardware of a sealing machine with a
lidding film so as for food packager to provide a more flexible
packaging option which selectively combines microwaveable and the
ability to preserve freshness according to product needs.
[0020] As mentioned above, the present invention provides a sealing
machine for rendering a food container capable of
modified-atmosphere freshness preservation as well as automatic
pressure regulation to the build up vast hot steam during microwave
heating. A container that can be as it is heat-sealed by the
sealing machine is made of a material selected from plastic, wood,
paper, synthetic paper, and ceramic, or a combination thereof. Each
of the lidding film and the sealing strip includes at least one
layer of stretched film and is made of a material selected from the
group consisting of polyolefin, polyester, polypropylene (PP),
polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC),
polycarbonate (PC), polyamide, nylon, polyethylene terephthalate
(PET), polyvinyl alcohol (PVA), ethylene-vinyl acetate (EVA),
ethylene vinyl alcohol (EVOH), polyvinyl dichloride (PVDC),
ethylene-styrene copolymer (ES), wax paper, synthetic paper,
glassine paper, polymer-coated paper, paper, and a combination
thereof.
[0021] The primary objective of the present invention is to provide
a sealing machine for sealing an opening of a container containing
frozen or refrigerated food. The sealing machine includes a
lidding-film processing unit, a bonding unit for bonding an
airtight sealing strip to a lidding film, and a heat-sealing unit
for covering the opening of the container with the lidding film. In
the lidding-film processing unit, the lidding film is unwound and
extended downward from a roll stock of the lidding film so as to
pass over a table. Die cutters and hot needles provided at the
table move back and forth vertically to form line-segment-shaped,
spaced slits and dot-shaped atmosphere-modifying breathing holes at
predetermined positions on a surface of the lidding film. The
processed lidding film proceeds to the bonding unit, in which a
roll of airtight sealing strip located above a table is unwound,
extended downward, and laid over the lidding film passing through
the bonding unit. Thus, the line-segment-shaped, spaced slits
formed on the lidding film are covered by the airtight sealing
strip. Then, the airtight sealing strip, whose bottom is provided
with adhesive, is bonded to the lidding film by means of a
hot-press sealing assembly installed at the table of the bonding
unit. Afterward, the lidding film boned with the airtight sealing
strip enters the sealing unit configured for sealing an opening of
a container. In the sealing unit, a container containing frozen or
refrigerated food is in place in a supporting frame of a table. The
lidding film passes over the supporting frame and thus covers the
container. A heat-sealing assembly provided at the table of the
heat-sealing unit seals the lidding film covering the container to
a heat-sealable flange along the rim of the opening of the
container. Scraps of the used lidding film are cut adjacent to the
rim of the opening of the container and wound up around a rewinding
spool. Thus, the lidding film which is now covering the container
has been processed and sealed to the container in a continuous
manner to effectively simplify sealing of the container and removal
of the scraps cut from the used lidding film.
[0022] According to the present invention, the dot-shaped
atmosphere-modifying breathing holes formed by being melted through
by the hot needles may vary in size, depending on the diameter and
vertical insertion depth of the slender and pointed hot alloy
needles which are resistant to high temperature and each have a
round sectional shape. When cooled, the melted breathing holes have
fixed shapes and will not close. Thus, the breathing holes form an
open structure having a slight but quantifiable air-permeation
capacity. To achieve a desired air-permeation capacity, the number
and size of the breathing holes are determined by the kinds and
total weight of fresh fruits and vegetables to be packaged in the
container, as well as by the temperature and duration of storage
and transportation. The diameter and air-permeation capacity of the
breathing holes are quantitatively tested by a digital optical
microscope and an air permeation testing machine, respectively. The
diameter of the melted dot-shaped breathing holes ranges from 0.1
mm to 1.5 mm.
[0023] If the hot needles in the sealing machine of the present
invention are not actuated, the resultant sealed food container is
completely closed. The original oxygen-containing air in the
container can be replaced by a gas mixture including a preset
percentage of inert gas such as nitrogen and carbon dioxide.
Alternatively, the completely air tight food container is processed
by vacuum packaging or other food packaging techniques.
Nevertheless, during microwave cooking, build up high-temperature,
high-pressure hot steam generated from within the packaged food can
be regulated via the line-segment-shaped, spaced slits on the
lidding film so as to prevent the container and the lidding film
from bursting.
[0024] For operational safety, the sealing machine of the present
invention is additionally provided with a protection shield outside
and around the die cutters and hot needles of the lidding-film
processing unit, thereby preventing an operator from being injured
during operation. Another safety feature of the sealing machine of
the present invention is a protection shield outside and around the
hot-press sealing assembly of the bonding unit such that the
operator's hands are protected from being squeezed.
[0025] Presented below is an example of applying the present
invention to fresh-cut produce or, more specifically, to Babylon
which was freshly picked, washed, cut, centrifugally dried, and
vacuum pre-cooled. The 342 gm Babylon was placed in microwavable
polypropylene (PP) trays each having dimensions of 140 mm.times.200
mm.times.50 mm (W.times.L.times.H). A laminated PET/PP lidding
film, 220 mm in width, was unwound from a spool and processed by
the die cutters and the hot needles so as to have a row of equally
spaced slits shaped as 7-mm line segments and a row of dot-shaped
atmosphere-modifying breathing holes, wherein the two rows are
parallel to each other and offset by 3 cm. The lidding film has
eight 7-mm line-segment-shaped, spaced slits and ten dot-shaped
atmosphere-modifying breathing holes in an area above each
fresh-cut produce loaded tray, wherein each melted breathing hole
has a diameter of 0.15 mm. The row of line-segment-shaped, equally
spaced slits was then covered by and bonded within a 20-mm wide,
airtight sealing strip. Finally, the lidding film bonded with the
airtight sealing strip was sealed, by the heat-sealing unit, to a
rim of the opening of each fresh-cut produce loaded tray. As a
result, only the ten 0.15-mm dot-shaped atmosphere-modifying
breathing holes were exposed on the lidding film of each tray to
provide modified-atmosphere freshness packaging condition. After
being refrigerated at a constant temperature of 5.degree. C. for
two weeks, the Babylon did not yellow, was free of mold, and did
not produce unpleasant odor. When subsequently cooked in a
1100-watt microwave oven full power for five minutes, the large
amount of build up hot pressurized steam generated intray during
the heating process was automatically regulated via the eight 7-mm
line-segment-shaped, spaced slits under the 20-mm wide, airtight
sealing strip such that neither the lidding film nor the tray
burst.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0026] The invention as well as a preferred mode of use, further
objectives, and advantages thereof will be best understood by
referring to the following detailed description of an illustrative
embodiment in conjunction with the accompanying drawings,
wherein:
[0027] FIG. 1 is a schematic drawing showing the operating
procedure of a sealing machine according to the present
invention;
[0028] FIG. 2 is a top view of a lidding film bonded with an
airtight sealing strip according to the present invention;
[0029] FIG. 3 is a perspective view of the lidding film and a
container yet to be sealed by the lidding film;
[0030] FIG. 4 is perspective view of the container sealed by the
lidding film; and
[0031] FIG. 5 is a perspective view showing the airtight sealing
strip being peeled off from the lidding film.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The present invention provides a sealing machine for sealing
a food container and thus rendering the food container capable of
keeping fruits and vegetables fresh in a modified atmosphere and
automatically adjusting pressure generated during microwave
heating. Referring to FIG. 1 and FIG. 5, a sealing machine 4
according to the present invention is configured to seal a
heat-sealable rim of an opening of a container 7 containing frozen
or refrigerated food. The sealing machine 4 includes a lidding-film
processing unit 1, a bonding unit 2 for bonding an airtight sealing
strip 6 to a lidding film 5, and a heat-sealing unit 3 for covering
the opening of the container 7 with the lidding film 5.
[0033] In the lidding-film processing unit 1 shown in FIG. 1, the
lidding film 5 is reeled out and extended downward to a table 12
from a roll of the lidding film 5 that is wound around a spool 11.
A perforating assembly 13 at the table 12 moves back and forth
vertically to effectuate cutting. The perforating assembly 13
includes die cutters 131 and hot needles 132 and is operable in
different ways according to the food to be packaged. For instance,
if the packaged food only requires modified-atmosphere freshness
packaging, the hot needles 132 of the perforating assembly 13 are
actuated to melt through the lidding film and thus form dot-shaped
atmosphere-modifying breathing holes 53 at predetermined positions
on a surface of the lidding film 5 while the lidding film 5 passes
through the lidding-film processing unit 1. If the packaged food
only requires microwave cooking, the die cutters 131 of the
perforating assembly 13 are actuated to form line-segment-shaped
spaced slits 52 at predetermined positions on the surface of the
lidding film 5 while the lidding film 5 passes through the
lidding-film processing unit 1. If the packaged food needs
modified-atmosphere freshness preservation as well as microwave
cooking, both the die cutters 131 and the hot needles 132 of the
perforating assembly 13 are actuated to form the desired
line-segment-shaped, spaced slits 52 and dot-shaped
atmosphere-modifying breathing holes 53 at predetermined positions
on the surface of the lidding film 5, as shown in FIG. 2, while the
lidding film 5 passes through the lidding-film processing unit 1.
An additional protection shield 15 is provided outside and covered
the perforating assembly 13 of the lidding-film processing unit 1
to prevent an operator's hands from being operational injury by
accident.
[0034] As shown in FIG. 1, the processed lidding film 5 moves on to
the bonding unit 2, in which a roll stock of an airtight sealing
strip 6 is reeled out downward from a spool 21 above a table 22 and
is laid over the lidding film 5 that passes through the bonding
unit 2. Thus, referring to FIG. 2, the airtight sealing strip 6
covers the line-segment-shaped, spaced slits 52 formed on the
lidding film 5. The airtight sealing strip 6, which has a bottom
side provided with adhesive layer material, is bonded to the
lidding film 5 by a hot-press sealing assembly 23 installed at the
table 22. A protection shield 24 is additionally provided outside
and around the hot-press sealing assembly 23 of the bonding unit 2
to protect the operator's limbs from being squeezed and
injured.
[0035] Afterward, referring back to FIG. 1, the lidding film 5
bonded with the airtight sealing strip 6 advances to the
heat-sealing unit 3, which is configured to seal the rim of the
opening of the container 7 after the container 7 is filled with
food. The container 7 containing frozen or refrigerated food is in
place in a supporting frame 32 of a table 31 so as to be covered by
the passing lidding film 5, as shown in FIG. 3. The lidding film 5
covering the container 7 is then sealed to a heat-sealable rim 72
of an opening 71 of the container 7, as shown in FIG. 4, by means
of a heat-sealing assembly 33 installed at the table 31. Scraps 54
outside the new heat-sealed rim 72 of the container 7 are cut from
the lidding film 5 and reeled in by a rewinding spool 34 located at
an opposite end of the heat-sealing unit 3, as shown in FIG. 1.
[0036] Thus, the lidding film 5 shown in FIG. 5 as covering the
opening 71 of the container 7 has been die cut, punctured, sealed
airtight, heat-sealed to the rim 72 of the container 7, and rid of
the scraps 54 in a continuous manner. In consequence, the sealing
of the container 7 and removal of the scraps 54 are effectively
simplified.
[0037] While the present invention is described herein by reference
to a preferred embodiment, it is understood that the embodiment is
not intended to limit the scope of the present invention. A person
skilled in the art can make various changes or modifications to the
disclosed embodiment without departing from the concept and scope
of the present invention. Therefore, the scope of the present
invention is defined only by the appended claims.
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