Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF FORMING A CONTAINER HAVING AN INTERNAL
RESERVOIR
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a Continuation-in-Part of U.S. Nonprovisional
Application Serial No. 11/559,653 filed November 14, 2006 and International
Application No. PCT/US06/044289 filed November 14, 2006, which claim the
benefit
of U.S. Provisional Application Serial No. 60/737,023 filed November 14, 2005,
each
of which are herein incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a container for packaging. Particularly,
the present invention is directed to a method of forming a container for
packaging
products or other items susceptible to exuding liquids, wherein the container
has an
internal reservoir for the collection of liquids exuded therefrom.
Description of Related Art
Conventional containers for packaging and display of meat, produce
and other products for consumers are made of plastic foam or paperboard, and
generally are simple concave trays having a separate transparent film cover or
overwrap.
Consumers prefer to purchase items such as meat, poultry, seafood and
products that release liquid, in dry packages. However, the amount of liquid
residing
in a food container typically increases over time, as the product ages and
exudes
liquid. Accordingly, retailers frequently rewrap the package, reduce the sale
price of
the product, or remove the product from the shelf because of consumer
perception that
the product might be spoiled. Moreover, such liquid can leak from a package if
the
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package is not well sealed.
A common practice to reduce the problems caused by exuded liquids
inside such containers includes the use of an absorbent pad, which is placed
in or
glued to the bottom of the container, typically between the container and the
contents
of the package. Typically, this practice requires a separate supply line in
the
manufacturing process for delivering the absorbent pad to the container, an
additional
step in the manufacturing process for application of the adhesive, and a dwell
period
to allow the adhesive to firmly bond the absorbent pad to the container.
Further, the
particular composition of absorbent pad and adhesive must comply with Federal
Drug
Administration guidelines and regulations regarding materials in direct
contact with
edible products.
Such conventional methods of forming containers having absorbent
pads generally have been considered satisfactory for their intended purpose.
For
example, U.S. Patent Nos. 3,834,606 and 6,695,138, which are hereby
incorporated
by reference in their entirety, disclose various absorbent pad configurations
and
methods of manufacture. However, these configurations are subject to a variety
of
disadvantages including a complex, cost prohibitive process in which the
resulting
products may have limited absorbency. In particular, these pads can tear or
stick to
the container contents and freeze to the contents when frozen, all of which
pose
inconvenience to the consumer, and added cost. Further, absorbent pads may dry
the
product with which they are in contact by wicking more liquid from the product
than
would otherwise occur naturally. Also, liquid held by an absorbent pad can be
squeezed out if the pad is pressed, which may occur as a result of handling or
due to
the force exerted by the film overwrap. Such pads also tend to leak fluid when
products are merchandised on their side. Moreover, the manufacturing process
is
labor intensive and requires a separate processing line to make and insert the
pads into
the containers, fabricating an assortment of pad sizes for use in varying tray
sizes, and
additional quality inspection is required to ensure proper placement of the
pads.
A self-absorbing tray using an open cell foam structure is another
conventional solution to absorb excess fluids. The material becomes absorbent
when
holes are pierced through the surface of the tray. While effective in reducing
labor
required to insert pads, an open cell tray structure is weaker overall,
thereby
increasing the chance for folded, cracked or broken trays during wrapping and
transport of the product. Depending on the tray design, open cell trays can
wick
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moisture through the tray and transfer liquid to the consumer's hands. Some
open cell
foam trays change color when saturated with fluid and are therefore unsightly
to
consumers. Furthermore, open cell trays offer a limited amount of absorbency.
Trays
loaded with large amounts of meat can easily overwhelm the absorbent capacity
of the
tray, resulting in unabsorbed liquid pooling at the bottom of the package.
Conventional double-walled trays, which contain an absorbent pad
between an outer and inner tray are expensive and also have a limited
absorbency.
Moisture is introduced to the absorbent core through holes in the inner tray.
Like that
of the open cell tray, the liquid within the pad may have a propensity to be
wicked up
to and leaked from top edges of these types of trays. Further, the process
used to
manufacture these trays results in a rough edge that tends to pierce film
wraps, which
also results in leakage of liquid from the container.
Packaging containing an absorbent pad, either glued inside or
sandwiched between inner and outer trays, creates a packaging container
comprised of
many different materials. The added labor and expense required to remove the
absorbent materials from the package prohibit recycling of such packaging.
As evident from the related art, conventional methods often require
excessive manufacturing cost and complexity while providing a container which
suffers from inadequate absorbency of exuded liquids.
There thus remains a need for an efficient and economic method of
manufacturing a container capable of contaiiunent of exuded liquids from and
pooling
of exuded liquids within container for packaging liquid-exuding products, such
as
meats, produce and other products.
SUMMARY OF THE INVENTION
The purpose and advantages of the present invention will be set forth
in and apparent from the description that follows, as well as will be learned
by
practice of the invention. Additional advantages of the invention will be
realized and
attained by the methods and systems particularly pointed out in the written
description
and claims hereof, as well as from the appended drawings.
An object of the invention is to provide a packaging tray for products
that tend to release liquids that avoid the drawbacks of existing trays set
forth above.
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To achieve these and other advantages and in accordance with the purpose of
the
invention, as embodied and broadly described, the invention includes a method
of
manufacturing a packaging container including first and second trays.
In one aspect of the invention, the method includes providing a first
web of material and a second web of material, and heating each of the first
and second
webs to facilitate the forming of the webs into a particular container shape,
as desired.
In one embodiment, the first web is formed into a first tray having a shape
which
includes a first bottom wall, and a surrounding first sidewall extending
generally
upwardly from the first bottom wall to define a space therein. Similarly, the
second
web is formed into a second tray having a shape which preferably includes a
second
bottom wall and a surrounding second sidewall extending generally upwardly
from
the second bottom wall to define a space therein. The second tray is sized
such that it
can be positioned within the space defined by the first tray such that the
second
bottom of the second tray is spaced from the first bottom of the first tray to
define a
reservoir therebetween. Further, the first and second trays are joined to one
another
about at least a portion of the perimeter, the joined first and second tray
defining a
product receiving unit for receiving a food product.
In accordance with another aspect of the invention, the method of
forming the container includes a dwell period to cool the first and second
trays to a
desired temperature, wherein at least one drain aperture is formed in the
second tray,
the at least one drain aperture in fluid communication with the reservoir. The
central
drain region is proximate to the center, or a centerline of first bottom the
second tray,
depending on the specific embodiment. Also, the second bottom of the second
tray
can be formed with a downward slope towards the drain aperture(s) to
facilitate the
draining of exuded liquid into the reservoir.
In accordanee with still another aspect of the invention, the first and
second webs are unwound from separate rolls of stock material, which can be of
either homogenous or dissimilar material compositions, and formed into the
desired
tray shape via vacuum or pressure thermoformer. The thermoformer can be
configured to form the first and second tray simultaneously, as well as form a
plurality of first and second trays simultaneously, if so desired. In one
arrangement,
the thermoformer includes an upper tool which is configured to impart the
desired
geometry of the second tray into the second web, and a lower tool which is
configured
to impart the desired geometry of the first tray into the first web.
Additionally, the
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steps of forming the first and second trays, joining the first and second
trays, and
forming the at least one drain aperture in the second tray can be performed in
a single
thermoformer.
The joining of the first and second trays can be achieved by a
conductive coil or heating element, disposed within either the upper or lower
tool of
the thermoformer, which forms a heat seal that extends around at least a
portion of the
perimeter of the first and second trays. In some embodiments, the heating
element is
employed at sufficient temperature and duration that a portion of sidewalls of
the first
and second tray are joined together. Additionally, the first bottom of the
first tray
may be formed to include at least one raised surface feature, to which the
second
bottom of the second tray can be joined. The joined first and second trays,
which in
an assembled arrangement define the product receiving unit, are separated or
trimmed
from the first and second webs, respectively.
In another aspect of the invention, the temporal order of the heating,
forming, joining, forming of the drain aperture, and trimming can be performed
in any
sequence, as desired.
In accordance with another aspect of the invention, a container is
formed by providing pre-formed first and second trays, wherein the first tray
has a
bottom wall and a surrounding sidewall extending generally upwardly from the
bottom wall to define a space therein. The second tray is configured to be
received
within the space of the first tray, such that the second tray is spaced from
the bottom
of the first tray to define a reservoir therebetween. The first and second
trays are
joined to each other along at least a portion of the perimeter of the second
tray. The
drain aperture(s) is formed by perforating at least one section of the second
tray to
define at least one drain aperture in fluid communication with the reservoir,
with at
least a portion of the perforated section being joined to the first tray. In
one
embodiment, the perforation of the drain aperture(s) is performed via a punch
device.
The punch device can include a conduit for introducing air through the drain
aperture(s) to displace the second tray relative to the bottom of the first
tray.
Preferably, the perforated section(s) is welded to the bottom of the first
tray.
It is to be understood that both the foregoing general description and
the following detailed description are exemplary and are intended to provide
further
explanation of the invention claimed.
The accompanying drawing, which is incorporated in and constitutes
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part of this specification, is included to illustrate and provide a further
understanding
of the metliod and system of the invention. Together with the description, the
drawing
serves to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1-A is a cross-sectional view of a first embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 1-B is a bottom-perspective view of a first embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 1-C is a cross-sectional view of a first embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 1-D is a cross-sectional view of a first embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 1-E is a top-perspective view of a first embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 2-A is a top view of a second embodiment of a container having
an internal reservoir, in accordance with the invention.
Figure 2-B is a cross-sectional view of a second embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 2-C is a cross-sectional view of a second embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 2-D is a perspective view of a second embodiment of a
container having an internal reservoir, in accordance with the invention.
Figure 3 is a schematic representation of the method of manufacturing
a container having an internal reservoir in accordance with the invention.
Figure 4 is a cross-sectional side view illustrating the forming of the
drain aperture(s).
Figure 5A-D is an enlarged view of various drain aperture
configurations for the container of Figures 1 A-E.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
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Reference will now be made in detail to the present preferred
embodiments of the invention, an example of which is illustrated in the
accompanying
drawing. The method and corresponding steps of the invention will be described
in
conjunction with the detailed description of the system.
The apparatus and related methods presented herein can be used for
packaging of any product, particularly a liquid-exuding product. The present
invention is particularly suited for the packaging of meat, produce, and other
perishable products. In accordance with the invention, a container is formed
comprising first and second trays. The various geometries and structural
features of
the first and second tray are disclosed in detail in copending United States
Nonprovisional Patent Application Serial Number 11/559,653 filed November 14,
2006, and United States Provisional Application Number 60/737,023 filed
November
14, 2005, which are herein incorporated by reference in its entirety.
Figures IA-IE illustrate an example of the product produced by the
inventive method described in detail below. Figures 1 A-1 E, illustrate a
container 100
which generally includes a first tray 220 and a second tray 110. The first or
"bottom"
tray 220 is preferably larger than the second tray 110, having a sidewall 221
and a
bottom wall 225 defining a recessed space. The space is preferably large
enough to
accommodate at least a portion of the second tray 110, if not essentially the
entire
second tray 110.
The second or "top" tray 110 includes a bottom wall 115 which rests
on or nests within the first tray 220 as shown in Figure 1 A. As embodied
herein, a
sidewall 111 preferably extends from the bottom wall 115. An outer edge 112 of
the
second tray 110 rests on and, preferably, is attached to an outer edge 212 of
the first
tray 220. Sidewall 111 of the second tray 110 connects the edge region 112 to
the
bottom wall 113 of the second tray 110. In a preferred embodiment, a flange is
provided at the edge of at least one of the edge regions 112, 212. Attachment
of the
two trays is preferably effected by any suitable method, and preferably, a
watertight
connection is formed, such as by heat welding or adhesive, cohesive,
ultrasonic
welding or chemical bonding techniques as discussed below.
For purpose of explanation and illustration, and not limitation, an
exemplary embodiment of the method in accordance with the invention is shown
in
Fig. 3 and is designated generally by reference character 500.
As shown in Fig. 3, the system 50 generally includes providing a first
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web of material (20) and a second web of material (10) from separate stock, or
alternatively providing a single supply of stock material which is then
converted into
first and second webs. Typically, the first and second webs are delivered from
separate stock rolls by simultaneously unwinding the rolls at equal rate of
speed. The
first and second webs each or both can be of homogenous or dissimilar material
compositions, and include indicia such as differing colors for various
aesthetic
configurations or marketing purposes, among other things. As embodied herein,
the
first and second webs are heated, such as in an oven (30) or equivalent device
which
preferably provides heat from both above and below at least one of the webs,
to
facilitate the shaping of the webs into the desired container geometry as well
as
assisting the joining of the webs, as will be discussed in detail below.
The first and second webs are delivered to a tray forming station (40),
which in a particular embodiment is a vacuum or positive pressure
thermoformer,
though various molds and other devices suitable for imparting the desired tray
geometries to the webs are contemplated to be within the scope of this
invention. As
embodied herein, the first and second webs preferably are formed into first
and
second trays, respectively. The former can be configured to form the first
(220) and
second (110) tray simultaneously, and can further be configured to form a
plurality of
first and second trays concurrently, if so desired. In one arrangement, the
thermoformer includes an upper tool (42) configured to impart the desired
geometry
of the upper surface of the second tray (110) into the second web (10), and a
lower
tool (44) which is configured to impart the desired geometry of the lower
surface of
the first tray (220) into the first web (20). Alternatively, the inverse
arrangement can
be performed in which the upper tool imparts the geometry of the first tray
into the
first web while the lower tool imparts the geometry of the second tray into
the second
web.
In accordance with one embodied herein, the first and second webs are
vertically aligned and indexed into the thermoformer (40) such that the first
and
second webs are disposed between the upper (42) tool and lower tool (44). A
vacuum
force is applied through channels in the upper and lower tool to bring the
webs (10,
20) into contact with the upper and lower tools, respectively. Preferably, the
upper
and lower tools also bring portions of the first and second webs, which can be
formed
into flanges or ledges of one or both trays, into contact with each other. The
vacuum
force applied via the upper and lower tool bring each web into conformance
with the
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respective tool geometry. Additionally, a positive pressure can be introduced
into the
space between the first and second webs, to further urge the webs against the
respective tools and enhance formation of the first and second trays,
respectively.
The upper and lower tools can be moved toward each other and converge to apply
a
compressive force which facilitates the formation of the flanges, as well as
creation of
the seal between the two trays as discussed in further detail below.
In one embodiment, as illustrated in Figs. lA-lE, the first web is
formed into a first tray having a shape which includes a first bottom wall,
and a
surrounding first sidewall extending generally upwardly from the first bottom
wall to
define a space therein. Similarly, the second web is formed into a second tray
having
a shape which includes a second bottom wall. Preferably, the second tray also
includes a surrounding second sidewall extending generally upwardly from the
second
bottom wall to define a space therein. The second tray is sized and shaped
such that
at least a portion of the second tray can be positioned within the space
defined by the
first tray such that the second bottom of the second tray is spaced from the
first
bottom of the first tray to define a reservoir (300) therebetween. Preferably,
the
reservoir (300) is sized to contain approximately 100 grams of exuded liquid.
It is further contemplated that one or more raised surface features (118,
218) such as ribs or protrusions can be formed on the bottoms of one or both
trays.
For example, the first tray can be provided with raised surface features to
contact with
the second bottom of the second tray. Such raised surface features are
advantageous
for enhancing the structural integrity of the overall container, and if joined
to the
second bottom of the second tray as illustrated, can ensure the size of the
reservoir,
i.e. the space (300) between the first bottom of the first tray and the second
bottom of
the second tray, generally remains constant. The raised surface features can
be
formed in a variety of desired quantity or pattern. Preferably, the surface
features are
configured to aide the flow of exuded liquid to the aperture, and into the
reservoir.
The surface features, furthermore, support the product to be packaged above
the upper
surface of the bottom wall of the second tray to minimize contact with the
exuded
liquid and prevent the contents from occluding the drain aperture.
Further, the first and second trays are joined to one another about at
least a portion of the perimeter, the joined first and second tray defining a
product
receiving container for receiving a food product. Numerous suitable techniques
may
be employed for joining the trays depending upon the material selected for
each tray,
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such as adhesive, cohesive, lip rolling, mechanical crimping, ultrasonic
welding,
vibration welding, chemical bonding, mechanical snap fitting and induction
welding,
or combinations thereof can also be used to join the first and second trays.
Other
known types of bonding techniques can be used, as can mechanical interlocking
or
interference fit techniques for joining the two trays.
Generally, for use with certain thermoplastic materials, heat sealing is
preferred for the resulting strength, cost, and performance. Heat sealing also
allows
for scrap portions of the webs remaining after the trimming operation to be
reclaimed
to provide material and cost savings.
In a preferred embodiment, a thermally conductive ring is provided in
at least one of, and preferably both of, the upper and lower tools of the
thermoformer.
Each ring generates sufficient heat to form a heat seal about the perimeter of
the first
and second trays disposed within the flange portion of the trays. More
preferably, the
position of the rings in the upper and lower tools can be adjustable in a
vertical
direction to allow for the modification to the clamp force provided by the
upper and
lower tools. This is advantageous in that the variable positioning of the
rings provides
a selective and sufficient force to attain a leak free seal between the first
and second
trays if desired. In order to reduce process cycle duration, the heating
elements
preferably are continuously activated, however the intermittent operation of
the rings
is also possible, if desired. Preferably, the heating element may be activated
to a
predetermined temperature, for example for use with webs having a thickness in
the
range of approximately 40 - 90 mm, to a temperature of approximately 220 F or
higher, and for a sufficient duration, for example approximately 3.75 seconds,
to form
a heat seal which can extend beyond the flange portion of the trays and
downwardly a
desired distance of approximately 1 inch along adjacent sidewalls of the trays
as
shown in Fig. 1-D. More preferably, the heating element on the lower tool
extends
toward the upper tool, whereas the corresponding surface of the upper tool is
flush,
such that upper surface of the second tray is not embossed or otherwise
altered. The
presence of such an elongated seal can reinforce the sidewalls and enhance the
crush
strength of the assembled container, while further preventing the tendency for
bowing
as a result of the application of a shrink wrap around the container.
According to another aspect of the invention illustrated in Figs. 4, the
upper tool (42) of the thermoformer is equipped with a device for forming at
least one
drain aperture (117) in the second tray. If desired, or necessary, depending
on the
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contents of the container, a plurality of apertures can be provided in a
central region
of the second bottom as shown in Figures 5A-D. Additionally or alternatively,
apertures can be provided along the edge of the second bottom of the second
tray
(110). Typically, the first and second webs are formed into the first and
second trays
while the webs are at an elevated temperature as discussed above. A cooling,
or dwell
period allows for the temperature of the formed trays to decrease to a desired
temperature, which is above ambient temperature. The drain aperture(s)
preferably
are formed at this above-ambient temperature.
In one embodiment, the upper tool includes a punch mechanism (46)
which perforates the second bottom of the second tray (110) to cut out at
least one
section, or slug (48), which defines the drain aperture(s). The cut-out (48)
section is
preferably is urged toward and adheres to the first bottom of the first tray
(220) by the
latent heat remaining after the heating of the trays discussed above. This
process is
advantageous in that it avoids the need to discard or otherwise secure a cut-
out that is
entirely severed from the second tray. Preferably, the punch mechanism
includes a
pneumatic port for introducing positive pressure between the first and second
webs
during the forming process to further urge the webs against the lower and
upper tools,
respectively.
As Figure 3 illustrates the simultaneous forming of a plurality of
containers, with each container including a first and second tray, the upper
tool of the
thermoformer can be equipped with a plurality of punch mechanisms, i.e. one
punch
mechanism for forming at least one drain aperture in the upper tray for each
corresponding container. In this embodiment, the punch mechanisms can be
operated
independently of each other, or alternatively the plurality of punch
mechanisms can
be driven simultaneously by a common operator. The operator for driving the
punch
mechanism(s) is preferably an air cylinder, however a servo motor or other
electro-
mechanical device can actuate the punch mechanism(s).
In the alternative, or in addition to forming the drain aperture(s) via the
punch mechanism forming a slug as described above, the drain aperture(s) (117)
can
be formed by melting or other high temperature process for forming a hole in
the
second tray. For example, this can be accomplished by heating a probe in the
upper
tool of the thermoformer, either continuously or intermittently, to a
temperature of
approximately 650 F and advancing the probe into the second tray. This high
temperature technique has the advantage of not forming any scrap or slug
portions,
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and therefore eliminates the need for any associated scrap removal steps
and/or
equipment. Additionally and/or alternatively, a finishing punch can be used to
form
the final desired shape and dimensions for the aperture(s) after the first and
second
trays have been formed, joined and cooled.
Generally, and as illustrated in Figs. 5A-5D, the size of the apertures
will depend upon the intended tray size and food product. It is preferable,
however, to
use an appropriate size that is sufficiently large to allow drainage of liquid
into the
reservoir and venting of gases out of the reservoir without the need for a
separate vent
hole, but sufficiently small to prevent spillage of the liquid from the
reservoir. The
preferred aperture size therefore will depend upon the number of apertures
provided,
whether venting is required or provided by an alternative vent opening, the
characteristics of the fluid (e.g., viscosity, surface tension), and the
expected flow
rate, among other factors. For example, a single round hole with a diameter of
about
0.375 inches is suitable for both drainage of liquid and venting of air for a
conventional meat product container.
By providing a plurality of apertures, a smaller aperture size can be
used to accommodate the same flow rate as a single aperture of larger size.
The total
amount of aperture area can be calculated by summing the entire area of each
individual aperture. In this manner, providing a plurality of smaller
apertures over a
large area can reduce the risk of spillage as well as reduce any compromise to
the
integrity of the bottom wall of the second or "upper" tray.
By contrast, however, it is beneficial to ensure adequate aperture area
to accommodate the required functionality. While, for the foregoing reasons, a
smaller aperture can be desirable, there are additional considerations to be
made when
reducing the size of the aperture. Firstly, for very small apertures, the
surface tension
of the liquid can provide a substantial obstacle to proper drainage. For these
and even
larger holes, if the aperture is not large enough to allow air from the
reservoir to
escape while liquid enters, then drainage will also be impeded.
Additionally or alternatively, the aperture(s) can be formed such that at
least a portion of the material which is punched to form the aperture(s)
remains
attached to the second tray. For example and in accordance with one
embodiment, the
entire boundary of the cut-out (48) is not separated from the second tray.
Instead, the
punch is configured to sever a cut-out along an edge defining the aperture(s)
that
extends a distance less than the entire perimeter of the aperture(s).
Accordingly, a
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portion of the cut-out remains connected to the remainder of the second tray.
The cut-
out can be depressed downwards and adhered to the first tray to allow liquid
to flow
into the internal reservoir.
To aid in the bonding of the cut-out to the second tray, as well as the
spacing of the first bottom of the first tray from the second bottom of the
second tray,
the punch device can be configured with an internal conduit for channeling air
into the
reservoir. A blast of heated air can be delivered via the conduit through the
aperture(s) to facilitate the separation of the bottoms of the first and
second trays and
further assist the shaping of the trays in the thermoformer, as discussed
above.
The upper (42) and lower (44) tools of the thermoformer (40) diverge
to release the assembled container and allow for the first and second webs to
be
indexed to the trimming station (50). In one embodiment, the trim station (50)
is a
separate station. Alternatively, and in accordance with another preferred
embodiment, a trim-in-place device can be employed in which the trimming
operation
is performed in the same station as used for forming of the trays, joining of
the trays,
and formation of the drain aperture(s). For example, a trim press can operate
along the
flange portion to sever each assembled container from the webs and thereby
define a
product container unit. The trim press can operate to sever one assembled
container
at a time, or alternatively a plurality of assembled containers
simultaneously, if so
desired. A plurality of severed containers can be stacked to reduce storage
space and
advanced to further product handling and shipping processes. Suitable
equipment for
such forming, joining and trimming processes are available from Irwin Research
and
Development, Inc. and can be modified accordingly as desired.
The particular order of operations described above is for purposes of
explanation and illustration only, and not limitation. Indeed, the steps of
heating the
webs, forming the webs into trays, joining the first and second trays, forming
a drain
aperture, and trimming the assembled container from the web supply can be
performed in a variety of desired temporal sequences. Further, while the
preferred
embodiment performs the steps of forming first and second webs into first and
second
trays, joining of the trays, and forming the drain aperture in a single
thermoformer, it
is contemplated that one or more of these operations can be performed
separately and
independently of each other -- although it is preferred that certain steps be
performed
simultaneously.
As detailed above, one preferred sequence for manufacturing the
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container includes: i) heating of the first and second webs; ii) forming first
and second
trays from the first and second webs, respectively; iii) joining the first and
second
trays; iv) punching a drain aperture(s); and v) trimming the assembled
container from
the web. Preferably, forming, joining and punching are performed
simultaneously.
Alternatively, the method for manufacturing the container can be performed in
the
following sequence: i) heating the first and second webs; ii) forming first
and second
trays from the first and second webs, respectively; iii) joining the first and
second
trays; iv) trimming the assembled container from the web; and v) punching a
drain
aperture(s). Preferably, at least forming and joining are performed
simultaneously,
and trimming and punching are fornied simultaneously. Alternatively, the
punching
of the drain aperture(s) can be performed in a station or apparatus which is
separate
and independent from the thermoformer, and/or trim press station.
Particularly, at
least forming of the first and second trays and joining of the first and
second trays can
be performed as a single integral step.
A representative example of a method of forming a tray is set forth
below for purpose of illustration and not limitation. A first web of polymeric
material
and approxiii7ately 40 mm thickness is provided and heated to approximately
220
degrees Fahrenheit. A second web of polymeric material and approximately 90 mm
thickness is provided and heated to 220 degrees Fahrenheit. The first and
second
webs are directed into a modified Irwin Magnum model thermoforming system with
an upper tool and a lower tool. A negative approximate-vacuum pressure is
applied to
draw each web against the corresponding tool for a dwell time of approximately
1
second, and a positive pressure of approximately 5 lbs. can be applied between
the
first and second webs to further enhance the thermoforming process. The upper
and
lower tools converge to apply a compressive force along heating elements
heated to a
temperature of about 220 degrees Fahrenheit for a period of approximately 3.75
seconds. The joined webs are then cooled to a desired temperature and trimmed
of
excess material form the perimeter.
In another embodiment of the invention, illustrated in Figs. 2A-2D, the
method of forming the container (200) includes forming a tray having (220) a
bottom
wall (225) and a surrounding sidewall (221) extending generally upwardly from
the
bottom wall to define a space therein. Rather than form the second tray in
conjunction with the first tray, a separate insert member (150) can be formed
and/or
provided from an independent manufacturing line. For example, the insert
member
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(150) can be a thermoformed sheet having an alternative contoured
configuration, or
can be a film or panel having a substantially flat or planar shape.
Preferably, at least
one drain aperture (117) is formed in the insert member as previously
described. The
insert member is inserted into the space of the first tray, so as to be spaced
from the
bottom of the first tray to define a reservoir (300) with the drain
aperture(s) (117) in
fluid communication with the reservoir. At least a portion of the perimeter of
the
insert member is joined to the first tray by adhesive, cohesive, heat welding,
ultrasonic welding or chemical bonding techniques or other suitable
techniques. The
first tray and insert member can be formed from similar or dissimilar material
compositions, and further have differing aesthetic designs, e.g. color.
A raised surface feature can be formed on the bottom of the first tray,
and/or on the second tray or insert member, in any of the shapes or
configurations as
described above. Additionally, a ledge (222) which protrudes inwardly towards
the
space of the first tray can be formed in the surrounding sidewall of the first
tray. The
second tray or insert member can be disposed within the space of the first
tray on top
of the raised surface feature(s) and/or protruding shelf (222).
Preferably, the second tray or insert member is provided with a
downward slope towards the drain aperture(s) to facilitate the draining of
exuded
liquid into the underlying reservoir. This sloped geometry can be provided by
employing a relatively rigid member of shape memory material in which the
desired
geometry is inlparted directly into the second tray or insert member during
the
manufacture of the insert member. Alternatively, a flexible insert member can
be
utilized in which the weight of the food product deflects the second tray or
insert
member downward to provide the desired slope. Further, raised surface features
can
be provided on the bottom of the first tray such that the height of the
surface features
decreases towards the center of the first tray. The second tray or insert
member can
be adhered to these raised surface features of the underlying tray so as to
create the
desired slope.
The containers described herein can be manufactured from any suitable
material, for example, expanded polystyrene foam, metal foil, such as aluminum
foil,
oriented polystyrene (OPS), polypropylene, mineral filled polypropylene,
amorphous
polyethylene terephthalate (APET), thermoplastics. It is to be understood that
the
foregoing list is not exhaustive, and that the containers can be made from
other
materials. The use of foams in forming of the trays and/or insert member
requires less
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material and thus provides a cost benefit over sheet materials.
The containers described herein can be of any shape desired, such as,
for example, circular, rectangular, oblong, oval, or square. The containers
can be
used for packaging uncooked foods, but can also be used for cooking and/or
holding
of cooked food, such as a cooked chicken. Advantageously, the subject
containers are
capable of retaining the liquid exuded during and after cooking of a roast
chicken, for
example. If used for cooking, the materials used for the container must be
capable of
satisfactorily withstanding oven temperatures.
It will be apparent to those skilled in the art that various modifications
and variations can be made in the method and system of the present invention
without
departing from the spirit or scope of the invention. Thus, it is intended that
the
present invention include modifications and variations that are within the
scope of the
appended claims and their equivalents.
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