US3718274A

US3718274A - High strength open bottom packaging trays

Info

Publication number: US3718274A
Authority: US
Inventors: R Reifers; K Bixler
Original assignee: Diamond International Corp
Current assignee: PACKAGINING Corp OF AMERICA A DE CORP; Packaging Corp of America
Priority date: 1972-04-24
Filing date: 1972-04-24
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27
Also published as: NO136617C; GB1344949A; CA973842A; FR2182783A2; DE2247912A1; AU467753B2; LU66206A1; AU4639872A; JPS4921273A; IT1045210B; BR7206741D0; SE375960B; ZA726095B; CH565686A5; DE2247912B2; NO136617B; IL40355A

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.

Description

United States Patent 1191 Reifers et al. 1 Feb. 27, 1973 [5 HIGH STRENGTH OPEN BOTTOM 2,310,465 2/1943 Samford ..229/29 F PACKAGING TRAYS 31521? 71323 ti r '1 Baa/56 171]; arte ieta. lnvemorsl Richard Relic", N canan, 3,056,232 10/1962 Chaplin ..229/2.5 ux Kenneth Bnxler, g- 3,217,962 11/1965 Weiss "229/25 ton, N.Y. 3,346,400 10/1967 Roesner ...229/2.5 X 3,357,625 12 1967 M 1 ..229 2.5 [73] Assignee: Diamond International Corporation, 3,480,178 1969 a issa X New York, NY. 3,185,371 5/1965 Reifers ..229/2.5 [22] Filed, April 24 1972 3,682,365 8/1972 Reifers ..229/2.5

[21] Appl. No.: 246,600 Primary ExaminerDavis T. Moorhead At 1( 1W. F1 k Related U.S. Application Data tome), at 0c 5 [63] Continuation-impart of Ser. No. 111,578, Feb. 1, ABSTRACT 1971' abandoned A tray of molded pulp or the like is provided for the packaging of meat, poultry or fish in conjunction with [52] U.S. C1. ..229/2.5, 217/26, 206/9495/i3734, an overwrapped transparent film The tray bottom is formed of a plurality of inverted V or U-shaped ribs 2; :5; 2 g? joining or intersecting in two directions and defining 1 1 1e 0 Zea/ 7 open windows therebetween, the height of each inverted V-shaped rib being on the order of several 56 R f d times the thickness of the remainder of the tray, and 1 e erences e the total volume of the inverted V-shaped ribs being UNITED STATES PATENTS approximately equal to the volume 01' a bottom of an "961 E Dglzlg imperforate bottom tray of the same size. D191,545 10 mery .7

442,500 12/1890 Weaver ..229/42 20 Claims, 15 Drawing Figures PATENTEB FEB 2 T1975 SHEET 1 or 3 PATENTEDFEBZYIHB SHEET 2 OF 3 HIGH STRENGTH OPEN BOTTOM PACKAGING TRAYS This is a continuation-in-part of copending parent application Ser. No. 111,578 filed Feb. 1, 1971, now abandoned.

FIELD OF INVENTION 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 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 nonelastic 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 tothe 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 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 X l3/l6 inch at the bottom of the inverted V-shaped ribs.

The transition betweensuch 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 to 35.

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.

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-scalable 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 US Pat. No. 3,185,371. As is conventional, such adjacent end and side wall merges at a rounded comer 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 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, theheight 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 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 2030", and these notches reduce the beam pick-up strength. In many instances, the construction of FIGS. 7-l0 is entirely suitable and the presence of the small notches 140 do not present any serious defect.

Another difference between the tray 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 comer 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 2040 at the intersection of the ribs to about 10 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 points provides for stiffer beam structure, as well as denesting, and the 2040 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 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 or less, and the maximum included angle adjacent each intersection on the order of about 30.

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 l0 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 k 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 impervioussubstance, 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 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 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 Vs.

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 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 5 material. On the other hand, the trays of the present in- 15 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.

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 35 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 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 5 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.

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 gutterlike 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 included V-angle.

11). 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 10-30.

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 ulp and wherein said end and side walls are of bowe 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.

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. I

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; 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.

Claims

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*.

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* 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*-30*.

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*.

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.