U.S. patent number 3,718,274 [Application Number 05/246,600] was granted by the patent office on 1973-02-27 for high strength open bottom packaging trays.
This patent grant is currently assigned to Diamond International Corporation. Invention is credited to Kenneth D. Bixler, Richard F. Reifers.
United States Patent |
3,718,274 |
Reifers , et al. |
February 27, 1973 |
HIGH STRENGTH OPEN BOTTOM PACKAGING TRAYS
Abstract
A tray of molded pulp or the like is provided for the packaging
of meat, poultry or fish in conjunction with an overwrapped
transparent film. The tray bottom is formed of a plurality of
inverted V or U-shaped ribs joining or intersecting in two
directions and defining open windows therebetween, the height of
each inverted V-shaped rib being on the order of several times the
thickness of the remainder of the tray, and the total volume of the
inverted V-shaped ribs being approximately equal to the volume of a
bottom of an imperforate bottom tray of the same size.
Inventors: |
Reifers; Richard F. (New
Canaan, CT), Bixler; Kenneth D. (Hunington, NY) |
Assignee: |
Diamond International
Corporation (New York, NY)
|
Family
ID: |
22931347 |
Appl.
No.: |
05/246,600 |
Filed: |
April 24, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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111578 |
Feb 1, 1971 |
|
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Current U.S.
Class: |
229/407;
217/26 |
Current CPC
Class: |
B65D
81/261 (20130101); Y02A 40/90 (20180101); Y02W
90/10 (20150501); Y02W 90/13 (20150501); Y02A
40/961 (20180101) |
Current International
Class: |
B65D
81/26 (20060101); B65d 001/00 (); B65d
065/00 () |
Field of
Search: |
;229/2.5,29M ;217/21F,26
;206/45.33 ;D9/219 ;99/174 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moorhead; Davis T.
Parent Case Text
This is a continuation-in-part of copending parent application Ser.
No. 111,578 filed Feb. 1, 1971, now abandoned.
Claims
WHAT IS CLAIMED IS:
1. In a generally rectangular molded tray for the packaging of
fresh meat, fish or poultry in conjunction with a transparent
overwrap film heat-sealed thereabout, said tray comprising a pair
of upwardly and outwardly inclined side walls, each said side wall
forming a long side of said tray; a pair of upwardly and outwardly
inclined end walls, each said end wall being adjacent to ends of
said side walls, and thereby forming the rectangular configuration
of said tray; a generally rounded corner between each said side
wall and each said end wall; and a peripheral lip extending
outwardly from said side and end walls and defining the periphery
of said tray, the improvement comprising:
means for providing improved oxygen breathing through the bottom of
the tray and for providing visibility through the bottom of the
tray and for supporting the meat, fish or poultry at the bottom of
said tray while maintaining a high humidity thereabout
substantially without the formation of liquid pools, and also for
protecting meat freshness and improving meat quality maintenance,
said breathing and support means comprising a plurality of strong,
substantially solid primary ribs having an inverted V-shaped
cross-section with rounded apices, some of said primary ribs
extending in one direction, and other of said primary ribs
extending in a different direction, said primary ribs meeting and
defining therebetween a plurality of open windows, said ribs having
a section modulus in combination with said end and side walls such
that the total strength is substantially equal to the beam strength
of a tray of the same material of equal weight with a flat,
imperforate bottom;
and means to increase rigidity and strength comprising a
peripherally extending annular transition zone between said end and
side walls and said primary ribs.
2. A tray in accordance with claim 1 molded of wood pulp.
3. A tray in accordance with claim 2 wherein said end and side
walls are of bowed construction.
4. A tray in accordance with claim 2 wherein said primary ribs have
a height above five times the thickness of said side and end
walls.
5. A tray in accordance with claim 2 wherein said primary ribs have
an included V-angle of about 10.degree..
6. A tray in accordance with claim 1 wherein said primary ribs
extend generally parallel to said side and end walls and meet at
right angles to form generally rectangular open windows.
7. A tray in accordance with claim 6, wherein said annular
transition zone comprises a gutter-like bottom wall and secondary
ribs extending thereacross.
8. A tray in accordance with claim 7 wherein said secondary ribs
are of reduced height above said gutter-like bottom wall and are
filled in on the bottom adjacent said end and side walls.
9. A tray in accordance with claim 7 wherein said secondary ribs
are of height substantially equal to said primary ribs, and are of
about 10.degree. included V-angle.
10. A tray in accordance with claim 7 wherein said secondary ribs
are staggered in relation to said primary ribs.
11. A tray in accordance with claim 7 wherein said primary ribs
have a varying included V-angle of about 10.degree.-30.degree..
12. A tray in accordance with claim 1 wherein said peripheral lip
comprises a relatively large and thick portion dome-shaped in
cross-section, and a horizontal portion extending outwardly from
said dome-shaped portion at a location substantially below the top
of the dome-shaped portion.
13. A tray in accordance with claim 12 molded of a wood pulp having
large free liquid accepting capacity, and provided with a liquid
impervious coating on the bottom surface thereof.
14. In a generally rectangular molded tray for the packaging of
meat, fish or poultry in conjunction with a transparent overwrap
film heat-sealed thereabout, said tray comprising a pair of
upwardly and outwardly inclined side walls, each said side wall
forming a long side of said tray; a pair of upwardly and outwardly
inclined end walls, each said end wall being adjacent to ends of
said side walls, and thereby forming the rectangular configuration
of said tray; a generally rounded corner between each said side
wall and each said end wall; and a peripheral lip extending
outwardly from said side and end walls and defining the periphery
of said tray, the improvement comprising:
means for suspending the meat, fish or poultry at a substantial
height above the exterior bottom of the tray so that the meat, fish
or poultry will not contact the overwrap film along the bottom of
the tray, and for providing improved oxygen breathing through the
tray bottom and for providing visibility through the tray bottom,
said breathing and suspending means comprising a plurality of
strong, substantially solid primary ribs of inverted V-shaped
cross-section with rounded apices and height substantially greater
than the thickness of said side and end walls, some of said primary
ribs extending in one direction and other of said primary ribs
extending in a different direction, said primary ribs joining and
defining therebetween a plurality of open windows;
and transition means to increase strength and rigidity including an
annular rib and a peripheral channel between said end and side
walls and said primary ribs.
15. A tray in accordance with claim 14 molded of wood pulp and
wherein said end and side walls are of bowed construction, said
primary ribs extending generally parallel to said side and end
walls and joining to form generally rectangular open windows.
16. A tray in accordance with claim 14 further comprising secondary
ribs extending across said gutter-like bottom wall to said end and
side walls, said secondary ribs having a height substantially equal
to said primary ribs and being staggered in relation to said
primary ribs, said primary and secondary ribs having an included
V-angle of about 10.degree..
17. A tray in accordance with claim 15, further comprising
secondary ribs in line with said primary ribs extending across said
gutter to intersect said end and side walls at a level
substantially above said rib height.
18. In a generally rectangular molded tray for the packaging of
meat, fish or poultry in conjunction with a transparent overwrap
film heat-sealed thereabout, said tray comprising a pair of
upwardly and outwardly inclined side walls, each said side wall
forming a long side of said tray; a pair of upwardly and outwardly
inclined and walls, each said end wall being adjacent to ends of
said side walls, and thereby forming the rectangular configuration
of said tray; a generally rounded corner between each said side
wall and each said end wall; and a peripheral lip extending
outwardly from said side and end walls and defining the periphery
of said tray, the improvement comprising:
means for control of meat bleeding and providing relatively
unobstructed vision to the meat packaged therein through open
windows of the tray bottom resulting in the protection and
maintenance of a tightly sealed film overwrap, said means
comprising a plurality of strong, high, substantially solid primary
ribs of inverted V-shaped cross-section with rounded apices and
molded of wood-pulp, some of said primary ribs extending in one
direction and other of said primary ribs extending in a different
direction, said primary ribs intersecting and defining therebetween
a plurality of open windows;
a peripheral gutter-like bottom wall between said end and side
walls and said primary ribs; and
wherein said peripheral lip comprises a relatively large and thick
portion dome-shaped in cross-section, and a horizontal portion
extending outwardly from said dome-shaped portion at a location
substantially below the top of the dome-shaped portion.
19. A tray in accordance with claim 17 molded of a wood pulp having
large free liquid accepting capacity, and provided with a liquid
impervious coating on the bottom surface thereof.
20. A tray in accordance with claim 1, further comprising means to
denest and determine a denesting interval consisting essentially of
material from which said tray is formed providing an additional
thickness on the interior underside of said inverted V-shaped ribs.
Description
FIELD OF INVENTION
The present invention relates to an open bottom food container and,
more particularly, to a food container for use for the packaging of
fresh meat, poultry and fish in conjunction with a transparent
overwrap film, and where the bottom wall is replaced with a
plurality of open windows defined by structural beams; and the
resultant high strength package so produced.
BACKGROUND
Molded wood or paper pulp food trays have served the food packaging
industry well for many years for the packaging of meat, fish and
poultry. Such trays have the advantage, besides low price and low
cost to the consumer, of being clean, sturdy and safe; of being
biodegradable so as to minimize the solids pollution problem; of
being capable of assimilating the free liquid juices which exude
from meat, fish and poultry; and of being air and vapor permeable
so as to maintain color and freshness of meat and permit passage of
liquid vapors. Nevertheless, in spite of the many advantages of
such molded wood pulp trays, certain locals have effectively
outlawed their usage by the requirement that a very high percentage
of the food packaged therein be visible to the consumer and since
wood pulp is normally opaque, such trays have not met this legal
requirement.
Consequently, in such locals the only packaging trays utilizable in
view of such laws are clear plastic trays. These clear plastic
trays have many defects, some shared with foam plastic trays,
including reduced strength, increased usage cost because of
downgrading of meat, fabrication of non-biodegradable material;
such trays have sharp edges which tend to cut the packaging film
and/or hands, as well as the meat packaged therein. These trays
collect liquid exudants in puddles from the meta, fish and poultry
packaged therein, thereby not only causing discoloration of the
packaged product, but also serving as a bacterial breeding ground
and further serving to opacify the package itself and provide
distortion in the remaining transparent areas thereby contributing
to the very problem which such trays were designed to overcome;
blood that goes under the tray acts to release the sealed film
causing soiled hands, soiled check out counters, leaking packages,
etc. In addition, the conventional plastic trays, being formed of
non-breathable material, inhibit oxygen migration to the meat at
the bottom of the tray; this causes further discoloration of the
meat and it is well known that meat in plastic trays deteriorates
on the bottom first.
Another defect of the clear plastic trays involves their
transmission of light along the plane of the tray walls, i.e. a
light pipe or fiber optic effect; this causes further discoloration
of the bottom of the meat. Light has a negative effect on meat
quality causing discoloration more quickly than meat which is
maintained more in the dark but under otherwise similar conditions.
Because of the light pipe effect meat packaged in clear plastic has
its bottom exposed to light constantly even when the tray rests on
an opaque object such as the bottom of the meat cooler or an
underlying package or between two packages.
SUMMARY
It is, accordingly, an object of the present invention to overcome
the defects of the prior art.
It is another object of the present invention to provide a molded,
nestable tray, preferably of molded wood pulp or the like, for the
packaging of meat, fish and poultry which, in spite of being made
of generally opaque or translucent material, provides a superior
quality of visibility of the packaged product.
It is another object of the present invention to provide for the
clean, safe and effective packaging of meats, fish and poultry.
It is another object of the present invention to provide a meat
tray which, although being primarily open on the bottom, is
sufficiently strong so as to facilitate the handling of meat which
tends to be floppy.
It is another object of the present invention to provide a meat
packaging tray which is not only effective but which is
inexpensive.
It is another object of the present invention to provide a meat
packaging tray which provides up to about 90% visibility of the
meat packaged, by providing minimized effective support contact of
the meat packaged in the bottom of the tray.
It is another object of the present invention to provide a meat
packaging tray having improved fresh meat quality maintenance and
superior visibility which are properties enhanced by the absence of
visibility distorting and breathability inhibiting accumulations of
free liquids, the tray tending to inhibit the exuding of juices by
the heat but accepting any liquid which is exuded, in a controlled
manner.
It is a major object of the present invention to provide a high
visibility meat tray having an open multiple window bottom which
has increased, rather than decreased, strength even when
overwrapped with stretchable, transparent plastic film which acts
to compress and sometimes collapse a conventional tray; and which
also has high beam strength.
It is another object of the present invention to provide a meat
packaging tray which provides visibility by providing a minimum
surface contact of the meat.
It is another object of the present invention to provide for
improved meat storage by providing a packaging tray in which the
bottom side of the meat is subjected to increased oxygen
transmission and in which the bottom of the meat is not subject to
rapid deterioration as in imperforate plastic trays.
It is another object of the present invention to provide a
packaging tray in which the bottom side of the meat is subjected to
improved oxygen availability to best maintain freshness and
color.
It is another object of the present invention to maintain the
packaged meat in a moist but not wet condition.
It is another object of the present invention to eliminate meat
contact with a non-breathing tray structure and provide an oxygen
permeable, see-thru structure that keeps meat from touching the
film windows on the bottom of the tray.
It is another object of the present invention to obviate the
necessity of utilizing clear plastic food trays which often provide
poor, distorted visibility, clear polystyrene plastic not being
oxygen permeable and thus tending to discolor the meat, and which
also transmit light to the bottom of the tray because of fiber
optic effect thereby adding to the discoloration problem, the clear
plastic also collecting exuded liquid in pools thereby adding to
visibility distortion and forming bacterial breeding grounds, and
causing nutrient loss.
These and other objects and the nature and advantages of the
instant invention will be more apparent from the following
description:
Meat packaging trays have evolved substantially over the years. The
earlier trays had essentially straight side walls and a flat
peripheral lip, and these served the trade successfully for many
years. However, as the nature of transparent plastic wrap film
changed and non-elastic and non-shrink cellophane was replaced with
more elastic thermoplastic or stretch overwrap films, the tray in
accordance with Reifers U.S. Pat. No. 3,185,371 was developed
improving the tray performance. In more recent years there has been
a strong consumer desire for greater visibility of fresh meat
packaged in trays.
One of the earlier attempts to provide visibility through the
bottom wall of the tray involved simply providing one or more
relatively large openings in the bottom of the tray. However, this
was found to weaken the tray and was not a successful approach to
the problem. The next attempt was to utilize a raised lip about the
periphery of the opening(s) in the bottom wall of the tray, the
function of the upwardly extending lip being to hold the meat
upwardly, to trap juices, and to stiffen and reinforce the
structure. However, this approach was not successful as the meat
tended to sag through the large opening(s) and the structure was
still too weak.
A recent approach, corresponding to the invention of the Bixler
application Ser. No. 53,545 uses a plurality of meeting or
intersecting, inverted V or U cross-section shaped ribs extending
across the bottom of the tray and merging with the side walls of
such tray. This construction provides maximum visibility with
minimum meat contact, and the inverted V-shaped ribs provides for a
reinforced structure. This construction of the Bixler application
is, in many respects, a successful approach to the problem, and the
present invention constitutes an improvement on this basic
construction.
In particular, the embodiment illustrated in the Bixler application
Ser. No. 53,545 still suffers, under certain conditions, from some
weakness, these weaknesses being manifested when a tray containing
meat, fish or poultry is tightly overwrapped with transparent
stretch film which strongly squeezes the tray side walls inwardly
distorting them and causing failure where ribs only are the single
support to side walls. Thus, in certain environments it is found
that the embodiment illustrated in Bixler Ser. No. 53,545 needs to
be strengthened, particularly where the V-ribs are joined to the
side walls of the tray. Thus, the smaller trays in accordance with
Bixler application Ser. No. 53,545 may fail at this location
because of the compressive force of the film alone while the larger
size trays fail more easily here because of the compressive force
of the film and because of greatly reduced beam strength in
relation to the increased strength that is actually needed in the
longer side walls.
The present invention provides such an improved structure by the
utilization of an improved force transfer distribution zone or
transition zone between the side walls of the tray and the ribs of
inverted V-cross-section such that the major rib beams are moved
inwardly away from the side walls themselves, preferably by the
provision of a peripheral gutter-like bottom wall or channel. To
provide increased side wall cave-in resistance it is preferred that
there be ribs in the gutter portion along its full bottom edge
merging into the end and side walls and joined to both an annular
boundary rib that encloses the grid and the side and end walls.
In addition, stronger ribs may be utilized. Greater rib strength is
preferably provided -- when the tray is molded of wood pulp -- by
the use of a narrow U- or V-angle. Increased strength may also be
optionally obtained by the use of higher ribs; it is found in
accordance with the present invention that it is desirable that the
inverted V-shaped ribs be of substantial height to provide a thick
platform or pallet upon which the meat is supported, wherein the
total volume of the primary ribs forming the platform and defining
the open windows is approximately 90 percent of the volume and
weight of the same area of a bottom of a conventional tray, such as
that shown in Reifers U.S. Pat. No. 3,185,371.
The height of the primary ribs may vary considerably depending on
the size of the window openings therebetween, so that the smaller
the opening and the greater the number of ribs, the smaller the
ribs need be, both for sufficient strength factor and for packaged
product maintenance. In this latter regard the packaged meat should
be kept off the overwrap film on the bottom of the tray. When
molded of wood pulp there may be a slight variation in rib height
of a given rib design based on furnish variation and weight
variation. In general, many small ribs tend to reduce visibility so
that the preferred minimum rib height should be on the order of
about one-fourth inch with openings therebetween of about 13/16
.times. 13/16 inch at the bottom of the inverted V-shaped ribs.
The transition between such ribs and the side and end walls of the
tray should be such that minimal or no "fault lines" or notches are
provided in the side or end wall and the transition zone, and this
is preferably accomplished -- when the tray is molded of wood pulp
-- by providing relatively thin ribs at the end and side walls
thereby promoting "filling in" of the V-structure. As an
alternative to reducing the width of the ribs at the side and end
walls, such ribs may be reduced in height. If desired, the ribs may
be terminated at the annular boundary rib prior to reaching the end
and side walls.
Preliminary lab tests show that fresh meat packaged on the tray of
the present invention, when formed of molded wood pulp, stays fresh
much longer than meat packaged in the so-called clear polystyrene
trays. Over the normal holding time range that meat is maintained
in the store including the time in the showcase, fresh meat
packaged in trays in accordance with the present invention has
better bloom retention, flavor retention, and better blood control
resulting in substantial savings because of less rewraps, less
downgrading, and less actual loss of meat. Some appearance
improvement was noted in the meat so packaged when compared to meat
packaged in molded wood pulp trays with solid bottoms; a
substantially greater improvement was noted in the appearance of
meat packaged in accordance with the present invention compared
with meat packaged in foam plastic trays; and a still greater
improvement was noted in appearance of meat packaged in accordance
with the present invention compared with meat packaged in clear
plastic trays. As pointed out above, the tray of the present
invention provides improved oxygen transmission, moisture vapor and
blood control under the meat, no fiber optic problem like clear
polystyrene trays all resulting in improved meat appearance with
unequaled protection to meat freshness.
The characteristics of the package provided in accordance with the
present invention, some of which are indicated above, are
accomplished by the use of relatively high support beams, namely,
the inverted V cross-section ribs, which are themselves strong,
which are coupled via a force transfer distribution zone to the
side and end walls in a way that maintains high side wall beam
strength, for highest total package strength. As pointed out above,
this rib connection with the force transfer zone, which takes the
force transfer from the side walls, is preferably achieved by
making sure that the force transfer ribs at the point of connection
to the end and side walls are relatively solid, i.e. filled in at
the bottoms so that there will be a relatively uninterrupted lower
side or end wall edge, with minimum notch formation. Rib forms have
been shown previously in trays of uniform material thickness, such
as plastic, that have the liability of an interrupted lower edge.
Rib filling, when the tray is manufactured of wood pulp, will
determine the precise configuration; the filling, in turn, is
determined by the rib V-angle, the type of material from which the
tray is formed, and the weight, height and rib thickness. These
factors are selected to optimize window visibility, strength and
nesting of the tray. In general, the included V-angle will lie in
the range of about 5.degree. to 35.degree..
The fundamental aspects of the tray in accordance with the present
invention may be said to be: spaced beam members, the spacing being
open between such beam members to allow for viewing the tray
contents between each beam of relatively solid material. The
section modulus of the beams is such that in combination with the
end and side walls, the total strength equals or exceeds the beam
strength of a tray of the same material of equal or slightly more
weight with a flat, solid bottom.
For a better understanding of the invention possible embodiments
thereof will now be described with reference to the attached
drawings, it being understood that these embodiments are to be
intended as merely exemplary and in no way limitative.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view of an embodiment of a tray in accordance with
the present invention;
FIG. 2 is a front elevation of the tray of FIG. 1;
FIG. 3 is a section taken along line 3 -- 3 of FIG. 1;
FIGS. 4, 5 and 6 are sections taken along lines 4 -- 4, 5 -- 5 and
6 -- 6, respectively, of FIG. 3;
FIG. 7 is a plan view of a second embodiment of a tray in
accordance with the present invention;
FIG. 8 is a side elevation of the tray of FIG. 7;
FIG. 9 is an end elevation of the tray in accordance with FIG.
7;
FIG. 10 is a section taken along line 10 -- 10 of FIG. 7;
FIG. 11 is a plan view of a third embodiment of a tray in
accordance with the present invention;
FIGS. 12-14 are sections taken along lines 12 -- 12, 13 -- 13 and
14 -- 14 of FIG. 11; and
FIG. 15 is a partially broken away section view showing a completed
package.
DETAILED DESCRIPTION OF EMBODIMENTS
Noting FIG. 1, it will be seen that a tray 10 is provided for the
packaging of meat, fish or poultry in association with an overwrap
film of transparent material such as plastic film or heat-sealable
cellophane. As is conventional, the food tray 10 has two upwardly
and outwardly inclined opposite end walls 18, both the end walls
and side walls preferably being bowed as described in the Reifers
U.S. Pat. No. 3,185,371. As is conventional, such adjacent end and
side wall merges at a rounded corner 20, and the side and end walls
terminate at their upper end in a downwardly and outwardly
extending peripheral lip 22; however, the preferred peripheral lip
is unlike anything previously used, and this is described in
greater detail below.
Instead of having a flat bottom wall as is conventional, the tray
10 is provided with a plurality of ribs 24 extending between the
bottom of the end walls 18, and, preferably at right angles
thereto, a plurality of ribs 26 extending between the side walls
16. As best seen in FIG. 3, these ribs form in cross section an
inverted V-shape with their apices forming the internal bottom of
the tray upon which the meat rests; it is clear from inspection
that the V-apex of each rib is well rounded unlike sharp ribs that
might cut or otherwise damage the meat. The V-angle in this
embodiment is approximately 30.degree. included angle. It will also
be clear from FIG. 3 that the bottom of each inverted V-rib
terminates in a plane passing through the bottom of the side and
end walls 16 and 18.
An important feature of the present invention involves the height
of the inverted V-shaped ribs 24 and 26. It will be noted best from
FIG. 3 that in this embodiment the height of such ribs is about
three-eights - seven-sixteenth inches, over five times the
thickness of the pulp material, i.e. about one-sixteenth inch,
forming the side and end walls of the tray. From this it will be
understood that the ribs 24 and 26 are of substantial height to
provide a thick platform or pallet upon which the meat is
supported. The cross-sectional area, in a vertical plane passing
through the ribs 24 or 26 forming the platform is approximately
equal to the cross-sectional area taken along a vertical plane of a
conventional tray of equal size with a flat solid bottom of
thickness equal to its side walls. By providing such a
construction, a sufficient section modulus is provided so that the
tray 10 will have proper strength to resist normal handling, to
prevent inward collapse during overwrapping, and to provide
sufficient beam strength.
In accordance with the present embodiment the transition zone is
provided in the form of an annular rib 28' and a peripheral
gutter-like bottom wall 28 which is not provided with windows and
which merges with the bottom portions of the end and side walls 16
and 18 along a rounded corner 30. It is preferred to provide such a
peripheral gutter-like bottom wall 28 since it provides, along with
the annular rib 28', a stronger structure and by having such a wall
it is easier to prevent the formation of "fault lines", "notches"
or "breaks" in the side or end walls, such "fault lines", "notches"
and "breaks" providing for reduced beam strength.
It is also preferred, in accordance with the present invention, to
provide secondary ribs 24' and 26' merging into the side and end
walls, although this is not essential as described below; this may
be accomplished as illustrated by merely extending the ribs 26
through the gutter beyond the annular boundary rib entirely to the
side walls 16 and the ribs 24 through the gutter entirely to the
end walls 18. However, when the ribs 24 and 26 are extended to the
end and side walls as secondary ribs 24' and 26', as is shown in
this embodiment, their height is reduced as they approach such end
and side walls (FIGS. 3-6). This expedient has the effect of
improving beam strength. Thus, it will be seen, noting FIG. 5, that
as the rib 26' approaches the side wall 16 its height, above the
solid bottom 28, is reduced in comparison with the annular rib 28'
forming a background in FIG. 5. As is seen in FIG. 4, the height of
the rib 26' has been reduced even more, closer to the side wall 16,
and at this location the rib height is reduced to such an extent
that the bottom 26" of the rib is filled in completely.
The reduction in rib height, as shown in FIGS. 4 and 5, to promote
filling of the rib bottom at 26" preserves the lower tray edge
without "notching" as is seen from the smooth configuration at the
bottom of the tray side wall 16 as shown in FIG. 2, compared with
the FIGS. 8 and 11 embodiments where the rib height is not
substantially reduced as it approaches the side wall. The
embodiment of FIGS. 1-6, with the greater reduction in rib height
as it approaches the side and end walls, results in an increased
beam pick-up strength, although there is a slight disadvantage
produced by providing a slight reduction in side wall deflection
resistance.
An alternative embodiment (not shown) terminates the ribs 24 and 26
at the boundary rib in which case there is no extension of the ribs
through the gutter or channel 28 to the side and/or end walls. This
embodiment has a decreased side wall deflection resistance,
although it is entirely satisfactory for many purposes,
particularly if the tray is wrapped with cellophane rather than
stretch or shrink film.
Another embodiment 100 is shown in FIGS. 7-10. As with the
embodiments of FIGS. 1-6, the tray 100 has side walls 116, end
walls 118, a peripheral lip 122, crossing inverted V-ribs 124 and
126 which form open windows therebetween, and a peripheral
gutter-like bottom wall 128 between the end and side walls and the
open window bottom portion.
The embodiment 100 of FIGS. 7-10 differs from the embodiment 10 of
FIGS. 1-6 in primarily two respects. First, contrary to the
embodiment described above, the secondary ribs 126' and 124' as
they approach the side and end walls 116 and 118 above the
peripheral solid bottom 128, do not reduce greatly in height. This
construction provides for additional side wall deflection
resistance, although it does have a tendency to produce the notches
140 as shown in FIGS. 8 and 9 when molded of wood pulp with an
included V-angle of about 20.degree.-30.degree., and these notches
reduce the beam pick-up strength. In many instances, the
construction of FIGS. 7-10 is entirely suitable and the presence of
the small notches 140 do not present any serious defect.
Another difference between the tray 100 and the tray 10 is the
provision of a different corner structure. Thus, in the tray 100 it
will be seen that the annular boundary rib 128' in the vicinity of
each of the four corner windows 150 makes a relatively sharp right
angle at each deep corner 120 of the tray 100. At contrast thereto,
in the tray 10 of FIGS. 1-6, it will be seen that the annular
boundary rib 28' forms a smooth curve at the corners of such
tray.
In yet another embodiment (not shown) a 20 percent increase in
windows area is obtained by varying the included V-angle from about
20.degree.-40.degree. at the intersection of the ribs to about
10.degree. or even less at a point midway between each
intersection. This V-angle variation provides bowed windows with
undulating ribs. Not only does this embodiment provide for
increased window area, but better light entry results insuring
improved viewing of the product packaged. When molded of wood pulp,
the rib back "filling" at the 10.degree. points provides for
stiffer beam structure, as well as denesting, and the
20.degree.-40.degree. flare aids screen formation used to cover
forming dies used if the article is made of a molded pulp of
synthetic or natural biodegradable materials.
The preferred embodiment in accordance with the present invention
is shown in FIGS. 11-14. This tray 200, as with the other
embodiments, has bowed side walls 216, bowed end walls 218, a
peripheral lip 222, crossing inverted V-ribs 224 and 226 of about
10.degree. included V-angle about five-sixteenths inch high
defining open windows, and a peripheral gutter section 228 between
the end and side walls and the open bottom portion. These ribs are
almost solid as seen in FIG. 14 and are very strong; they have a
volume of about 90 percent that of a bottom of a standard solid
bottom tray of equal size. Such ribs are preferably of the
undulating type with a minimum included angle -- between each
intersection -- about 10.degree. or less, and the maximum included
angle -- adjacent each intersection -- on the order of about
30.degree..
Tray 200 provides increased beam strength along with increased side
wall deflection resistance by the use of staggered merging ribs
224' and 226' which are also of about one-fourth to three-eighths
inch height and of about 10.degree. included U or V-angle. Thus,
instead of extending the primary ribs to the side and end walls as
in the embodiments of FIGS. 1 and 8, the primary inverted V-ribs
224 and 226 are terminated at the boundary rib 228' and staggered
secondary or force-transfer ribs 224' and 226' extend across the
gutter 228 to the side and end walls; the staggering permits the
use of an additional rib 224' and 226' so that in the illustrated
version there are five primary ribs 224 -- besides the two defining
the gutter 228 -- and six secondary ribs 224', and this improves
both beam strength and side wall deflection resistance, the
staggered secondary ribs acting as a shock absorber for inward side
wall force during wrapping.
In addition, such secondary ribs 224' and 226' are full height as
seen in FIGS. 12-14, increasing side wall deflection resistance.
Another feature of the secondary ribs 224' and 226', contributing
to beam strength by the elimination of "notches", "fault lines" or
"breaks" in the side and end walls, is their provision in
substantially solid form, being substantially filled in at the
bottom when molded of wood pulp, noting FIG. 14, thus reducing
notch formation at the side and end walls, and contributing to less
warpage during free drying. In another embodiment such ribs 224'
and 226' may be made thinner than rigs 224 and 226 with less
rounded tops because they extend only across the peripheral gutter
and do not provide substantial meat support.
While the tray of the present invention is preferably formed of
conventional molded wood or paper pulp stock which may be formed or
preformed from a water slurry, it will be understood that other
materials may be used; the ribs may be made of harder paper stock,
or such ribs may be specially pressed or otherwise treated. In a
preferred embodiment, the wood pulp stock comprises about 3 percent
ureaformaldehyde wet strength resin or about 1 1/2 percent
melamine-formaldehyde wet strength resin (both FDA approved) and,
furthermore, has a large capacity to accept free liquids which have
exuded from the "problem cuts" or "heavy bleeders", as they are
known in the art; in this embodiment the bottom of the tray ribs
may be specially treated with an inert, impervious water-resistant
substance, e.g. wax or plastic such as polyethylene, while the
upper portions of the ribs will accept this free liquid and expand
to provide a softened cushion for the meat. If desired, the rib
tops may also be coated with the impervious substance, leaving the
side rib surfaces and it center free to accept excess free
liquids.
Referring to FIG. 15, there is seen a cut of meat packaged using
the tray of the present invention in conjunction with an overwrap
transparent film 60. In the illustrated embodiment, the lip 222 is
provided with a special shape, particularly useful when used in
combination with the special wood pulp stock having large free
liquid accepting capacity. The peripheral lip 222 has an outwardly
extending horizontal terminal portion 230 and, as seen in the
drawing, the film 60 contacts the lip 222 along two distinct and
separated portions, i.e. the end of the terminal portion 230 and
the top of the lip at point 232, to provide a double gasket or
sealing function. With the "problem cuts" of beef (about 10 percent
of the meat packaged), which bleed profusely, the special accepting
furnish in conjunction with the double sealing provided by the
peripheral lip 222, prevents the travel of free liquid by capillary
action between the film 60 and the lip from the inside to the
outside of the tray were it would cause the plastic heat seal of
the plastic film to open effecting leakage and unwrapping of the
package, beside providing an unsightly appearance.
The lip 222 of FIG. 15 has mechanical advantages even without the
use of the special accepting furnish, the latter normally having
particular desirability in conjunction with "problem cuts". The lip
222 is provided with greater material mass which provides
additional beam strength to resist inward force provided by the
tension exerted by the stretched film 60. In addition, the
horizontal portion 230, being at a height considerably lower than
the top 232 of the lip 222, absorbs inwardly directed forces in a
manner that stresses the side wall less because the resultant lever
arm is lower, e.g. 30-35 percent lower. Additionally vector
analysis shows that the net effect in inward deflection resulting
from inward force is reduced and there is 12% less bending
moment.
If desired, the tray of the present invention may be formed of
other, equivalent materials, the structural advantages of the tray
deriving from its geometry. For example, the tray may be formed of
plastic foam, such as structural cellular polystyrene foam
comprising on the order of 70 percent void space, or porous
polyolefin material, or a biodegradable plastic such as
biodegradable foam polystyrene. If formed of materials having
different strength characteristics, various changes in the
configuration may be necessary and, depending on the material,
certain advantages may be absent. When made of conventional foam
polystyrene, sufficient strength may be provided by completely
filling in the channel 228 to provide a continuous annular rib
corresponding to the section shown in FIG. 13.
It will be understood that visibility through the bottom of the
tray to the bottom surface of the meat is very great, on the order
of at least 70 percent, and that there is a minimum surface contact
of the meat on the soft rounded apices of the inverted V's.
The tray of the present invention has many advantages, a number of
which have been delineated above. In brief, however, it may be
noted:
a. Visibility -- Both sides of the meat, fish or poultry may be
viewed, providing up to 90 percent view of contents with at least
70 percent of the bottom of the contents being visible. This
actually results in improved visibility when compared to clear
plastic trays some of which introduce an added layer of thick
plastic sheet in each window area and do not control juices which
distort, mislead, and impair vision where they exist.
b. Strength -- Added beam of structural members across bottom adds
stiffening. Tray easily resists all types of normal handling: (1)
The tray has sufficient strength to resist handling during
wrapping; compression of film on the inward side wall is the main
force which tends to cause side wall deformation or collapse, but
the present tray resists such deformation or collapse. (2) The tray
resists damage from handling in the store and by consumer at home;
insufficient beam strength of package for weight of contents may
tend to deform or break some packages when lifted, but the tray of
the present invention tends to resist such deformation or
breakage.
c. Breathability -- For meat freshness and bloom protection, the
open meat suspending structure promotes oxygen transfer as does the
absence of free liquid pools which in other packages clog the pores
of the overwrap film. This maintains better meat color and provides
for maintenance of meat bloom and quality over the extended period
for store sale to home storage. In addition, no anaerobic bacteria,
such as slime bacteria or botulism, are possible with the high
oxygen transmission provided.
d. Juice Control -- The ribbed tray suspends the entire bottom of
the meat in a moisture saturated atmosphere, desirable for meat
quality preservation. Only a small amount of liquid and a portion
of this water evaporates to provide this moisture laden atmosphere;
the remaining portion of exuded liquid is controlled by the pulp.
This controlled acceptance of free liquids enhances appearance,
maintains near perfect visibility and prolongs the freshness and
bloom of the meat. The actual contact of the meat with the tray is
less than any tray structure even known in commercial use. This
minimal contact of the meat with the tray together with the
maintenance of the moisture saturated atmosphere inhibits the
exuding of liquids and insures that the meat retains its moist
surface and juicy character but without forming puddles or pools of
liquid.
e. Nestability -- Trays nest closely for economical storage and
shipping. The bottom itself determines the stacking interval and
gives good denesting as well as prevention of jammed trays. The
trays are easy to denest too because they may be ram stacked and
have an internal compressive spring back that aids denesting. The
inverted V-shaped ribs are preferably indented in the bottom to
match or complement the upper part of the rib shape thereby
reducing the stacking interval with consequent reduced storage and
shipping costs without a sacrifice in strength.
f. Refrigeration -- Beam bottom construction holds meats suspended,
providing improved circulation of moisture saturated air for
oxygenation, and rapid cooling of the meat.
The multiple window frame construction of the trays of the present
invention accepts into the frame itself any excessive
non-evaporated seepage of liquid from the meat. This prevents the
free flowing of bloody liquid from draining into the window opening
that is composed of film alone. This is in contradistinction to the
window area or rib patterns on the non-breathable clear polystyrene
trays, which are covered by the extra bottom layers or layers of
breathable transparent film that is rendered useless in the
breathing function, and again reduces the effective visibility of
the polystyrene tray.
Just one drop of blood in the polystyrene tray creates an immediate
problem in the specific window area because of distortion of
remaining visibility, and additionally exposes the meat surface to
a pool of bloody liquid that provides a broth for bacterial action,
often causing slime buildup and causing shorter shelf life in the
store and in the home refrigerator. By way of contrast, the trays
of the present invention with the multiple open window features
maintain the advantages of control of exuding liquid, primarily by
maintaining a saturated atmosphere about the meat but also by
controlled acceptance while at the same time taking advantage of
this control to maintain excellent visibility in the windows that
are breathable, maintain great effectiveness of the transparent
film over the entire surface of the package, protecting it to the
maximum freshness and minimum bacterial action.
The trays of the present invention also have no problem of cutting
film like the clear plastic trays because the film is protected by
the soft edges of the pulp tray. The meat contained in the clear
polystyrene tray is exposed to bacteria and other contamination
when the film has been cut by the sharp edges of the polystyrene
tray. After extended storage the meat in the clear polystyrene
trays nearly always discolors on the bottom first because of the
destructive effects of the non-breathing, light transmitting, clear
styrene material. On the other hand, the trays of the present
invention work to protect the meat freshness so perfectly that the
bottom of the meat most always retains its meat freshness longer
than the top of the meat under conditions of extended storage.
It is to be understood that the invention is not limited to the
embodiments disclosed which are offered illustratively and that
modifications may be made without departing from the invention; for
example, variations in the precise configuration, spacing, height
and arrangement of the ribs and the windows may be made, e.g. the
ribs may intersect or meet at such angles to provide brick-work,
diamond shaped, etc. window patterns.
* * * * *