WO1986000275A1

WO1986000275A1 - Packaging tray and packaging method

Info

Publication number: WO1986000275A1
Application number: PCT/AU1985/000131
Authority: WO
Inventors: James Valentine Henry David Garwood; Anthony James Murray Garwood
Original assignee: Garwood James Valentine Henry
Priority date: 1984-06-20
Filing date: 1985-06-20
Publication date: 1986-01-16
Also published as: DK76786D0; DK76786A; EP0222750A4; EP0222750A1

Abstract

A generally rigid tray (1) for use in packaging goods, said tray (1) comprising at least a formed plastics material upper tray (3) nested within a formed plastics material lower tray (5), either the upper tray (1) or the lower tray (5) or both being corrugated and the upper and lower trays being bonded to each other where the crests of the corrugations touch the other tray.

Description

- / -

PACKAGING TRAY AND PACKAGING MEIHDD

Field of the Invention

This invention relates to an improved packaging tray and packaging method and relates particularly, but not exclusively, to such for use in packaging meat. The invention has particular application to the packaging of food stuffs which can deteriorate in normal atmosphere, such as vegetables and/or meat but it is not limited solely thereto. Description of Prior Art Hitherto, in the art of packaging meat it has been known to package the meat in a package which comprises a rigid tray member and wherein the tray member is closed by an upper lid and wherein the upper lid is thermo sealed to the tray. The packaging is filled with a gas which will inhibit deterioration of the meat. The tray and the lid are of a plastics material which will inhibit the escape of gas. Typically, the gas for vegetables comprises 5% oxygen, 3% carbon dioxide and 92% nitrogen. For fresh meat, it comprises 80% oxygen and 20% carbon^' dioxide. Other gases may be used if desired. The exact type of gases are known generally in this art. For packaging fresh meat, the volume of gas should approximately equal the volume of the meat in order to provide for long shelf life.

In the prior art constructions, the tray is usually of about 0.02 inches in thickness and is therefore quite expensive. Typically, the tray is formed from a single web of two or more layers of plastics material. One of the layers is a gas barrier layer, whilst the other is a layer which permits thermo sealing to the lid. Typically, the tray -can be formed from a web of co-extruded material. The lid of the tray is usually of a co-extruded or laminated web but of thinner construction than that of the tray. The lid has one layer of a gas impervious plastics -material and the other layer is of a thermo sealable material such that it can be heat sealed to the tray. The tray may be composed of polystyrene and polyethylene; P.V.C., P.V.D.C., and polyethylene or other combinations of like plastics of these types. The lid may be of layers of nylon and polyethylene or nylon, P.V.D.C. and polyethylene or of polyester, P.V.D.C. and polyethylene. The use of at least two materials is necessary because the gas barrier layer is not a thermo sealing type plastic material.

Various combinations of the above materials are possible, but the end requirement for the tray is to be rigid and to have a gas barrier characteristic. A requirement for the package is that it has a gas barrier characteristic. Preferably the tray and the lid are thermo sealable together. The materials from which the tray is made are very expensive particularly having regard to the 0.02 inch thickness requirement to give the necessary^' rigidity.

Statement of the Invention It is therefore an object of the present invention to provide an improved packaging tray, an improved method of producing trays, an improved package and an improved method for packaging products, such as meat, in such packages, and an apparatus for producing such a package. In accordance with a first aspect of the present invention there is provided:-

A generally rigid tray for use in packaging goods, said tray comprising at least a formed plastics material upper tray nested within a formed plastics ^• material lower tray, either the upper tray or the lower tray or both being corrugated and the upper and lower tray being bonded to each other where the crests of the corrugations touch the other tray.

In accordance with a further aspect of the present invention there is provided a method for producing a generally rigid packaging tray comprising:

(a) forming an upper plastics material tray in a web of plastics material

(b) forming a lower plastics material tray in a web of plastics material _ _

(c) providing corrugations in either or both trays at step (a) or (b)

(d) relatively moving the upper and lower trays so that the upper tray is nested within the lower tray

(e) bonding the upper and lower trays together where the crests of corrugations touch the other tray.

In accordance with a further aspect of the present invention there is provided improved packaging, particularly, but not exclusively for fresh meat, comprising^'a generally rigid tray into which meat can be placed, said generally rigid tray being of laminated construction and being closed by a lid and wherein the package has a gas retained therein which will inhibit deterioration of the meat, said packaging being characterised by said tray comprising at least a formed plastics material upper tray nested with a formed plastics material lower tray, either the upper tray or the lower tray or both being corrugated and the upper and lower tray being bonded to each other where the crests of the corrugations touch the other tray said lid being, in the case of packaged meats or like foodstuffs, of plastics material which will be a barrier to gas therein, and in the case of fresh vegetables and the like foodstuffs, of plastics material which will be pervious to at least -oxygen.

For fresh meats it is preferable to have the innermost surface of the tray on which it rests corrugated so the meat is supported by the crests of the corrugations and does not contact all of the surface of the tray, thereby allowing the gas to contact nearly all of the surfaces of the meat. A process for producing trays of the packaging as recited above is also provided. Throughout this specification the term "tray" should be construed to cover any receptacle into which goods can be placed. The receptacle may be flat such as like a meat tray or it may be deep like a glass or a can.

Brief Description of Drawings In order that the present invention can be more clearly ascertained preferred constructions will now be described with reference to the accompanying drawings wherein:-

Figure 1 is an exploded top perspective view of a preferred tray;

Figure 2 is an exploded top perspective view of a preferred package;

Figure 3 is a side cross-sectional view of the package;

Figure 4 is a transverse cross-sectional view of the package taken along line 4-4 of Figure 3; Figure 5 is a detailed close-up view of a bottom corner of the package as shown in Figure 3, but showing a further embodiment;

Figure 6 is a side schematic view of apparatus used for producing the required packages; Figure 7 is a close-up side view of a thermo forming station and of a tray resting and bonding station;

Figure 8 is a detailed close-up view of a gas flushing and lid sealing station; and Figure 9 is a cross-sectional view taken along line 9-9 of Figure 7;

Figures 10 through 15 show some possible variations of methods and packaging included within the broad aspects of the invention. Description of Preferred Embodiments Referring firstly to Figure 1 there is shown an improved tray 1 for use in packaging goods. In the embodiment of Figure 1 the tray 1 is formed from two webs of plastics material by producing an upper tray 3 and a lower tray 5. The upper tray 3 and the lower tray 5 may both be corrugated if desired or alternatively only one of the upper or lower trays 3 and 5 may be corrugated. The tray 1 is therefore produced by nesting an upper tray 3 within a lower tray 5. The trays 3 and 5 are bonded together by any convenient means such as by thermo sealing, friction welding, high frequency welding, sonic welding and even by gluing or by dissolving the plastics material with a solvent and then urging the dissolved surfaces to be bonded together. Desirably the bonding is where the crests of the corrugations on one tray touch the other tray. Typically if both the upper tray 3 and the lower tray 5 are corrugated the corrugations are arranged such that the crest of one will engage with the troughs of the other so there will be point contact at the point of bonding. This will provide for maximum strength of the tray 1. The tray 1 is made from an inexpensive plastics material such as polyethylene or polypropylene P.V.C. or polystyrene. The plastics material is preferably in the order of 0.002 inches in thickness although it is possible to use thicker materials but naturally this will have a consequent effect on the final cost of the tray 1. Each of the trays 3 and 5 is preferably made by thermo forming the tray shapes into individual webs of plastics material. This can be suitably done by heating webs of plastics material and inserting the webs of plastics material between suitably shaped male and female die members. Alternatively, the trays can be produced in any other convenient manner such as by injection moulding techniques. Conveniently, the upper tray 3 is bonded to the lower tray 5 by melting the plastics material and thermo sealing the trays together. Preferably the necessary melting can be effected by melting the plastics material with impulse heat sealing means at the region of the crests of the corrugations by introducing the nested trays 3 and 5 into a female die cavity which has impulse sealing means appropriately positioned on the surface thereof. A male die member can be inserted into the tray 3 so as to urge the tray 3 towards the crests of corrugations in tray 5 so that bonding can be effected.

If desired a third or further tray(s) can be nested together so as to produce a rigid tray 1. Each of the trays can then be suitably bonded where the corrugations touch the adjacent tray.

If the tray is to have a gas barrier, then one or more of the trays 3 and 5 must be made from a material which has this characteristic. If the bonding is to be by thermo sealing, then the trays 3 and 5 will have to be of a co-extruded or multi-layered construction where one of the layers is a thermo sealing layer and another is a gas barrier layer. Such material can be used for sonic welding and R.F. or high frequency welding also. If high frequency welding is envisaged then the trays 3 and 5 can be of only P.V.C. as this material is bondable by this process and it has a gas barrier characteristic.

In the embodiment shown in.. Figure 1 where each of the trays 3 and 5 have a thickness of 0.002 inches, it has been found that the tray has a comparable strength to the same size tray of a single web of plastics material of 0.02 inches thick.

Referring now to Figure 2 there is shown an exploded top perspective view of a preferred package 1A for holding fresh food such as vegetables. The package lA is made from four webs of plastics material. Suitable materials for each web are co-extruded layers, or alternatively two or more laminated layers, of nylon and polyethylene or polystyrene, P.V.D.C. and polyethylene, or polypropylene and polyethylene. The essential requirements of the individual webs are that they are heat sealable to one another and that at least one of the webs is a gas barrier such that any gas which is to be retained within the packaging cannot escape. In this connection at least the lid web of the packaging must possess this features but any one or more of the succeeding webs from which the tray is made must also have these' features. The webs may be of a single layer of P.V.C. if they are high frequency welded together. The package comprises a tray 2 which is composed of an upper tray 3, a corrugated intermediate tray 5 and a lower tray 7. A lid 6 is also provided. Each of the trays 3, 5 and 7 are of generally the same rectangular configuration and are shaped to allow for nesting relationship of one within the other. Food such as vegetables is placed in the tray 2 in the upper tray 3 thereof. During assembly the lid 1, and tray 2 are brought together in aligned relationship as shown in Figure 2, and gas is introduced,between the lid 6 and the upper tray 3. At the same time the lid 6 and the tray 2 are thermo sealed together. Thus, there is produced a package which contains food such as vegetables and a deterioration inhibiting gas. Desirably, the lid 6 and the tray 2 are made of transparent materials such that the contents, can be viewed from all sides. It can be observed from Figure 2, that the base of all of the trays 3, 5 and 7 are gable-like in appearance. This is provided to allow any juices which should seep from the food, to drain to the lowermost corners. This is particularly desirable in the art of packaging fresh meats, and particularly so when the tray 2 is transparent, because then, such juices do not extend over substantially all of the surface of the bottom of the tray 2 and detract from the appearance of the packaged fresh meat. It can also be seen that each of the trays 3, 5 and 7 have peripheral lips 3', 5¹ and 7' . The peripheral lips are provided principally to allow an effective thermo sealing surface for the lid with the tray 2. This will be explained further in due course. In the preferred embodiment, each of the webs of material from which the lid 6 , the upper tray 3, the corrugated tray 5 and the lower tray 7 are made, is of about 0.002 inches thick and therefore the total package represents a considerable saving in materials over that in the prior art, where considerably more plastics material is used.

Referring now to Figure 3 there is shown a transverse cross-sectional view of an assembled tray 2 . Here, it can be seen there is the upper tray 3 nestled within the corrugated tray 5, and that the corrugated tray 5 is nestled within the lower tray 7. The gable-like bottom of the tray 2 can be clearly seen. It is noted that at each side of the gable-like bottom there is provided a generally horizontally extending platform 9. The platforms 9 serve as drainage points into which any liquids which escape from the food can gravitate. The lower tray 7 is bonded to the corrugated tray 5 and the corrugated tray 5 is bonded to •the upper tray 3. The bonding is at the respective surfaces of the corrugations which contact each other. The actual bonding of the lower tray 7 to the corrugated tray 5 and of the upper tray 3 to the corrugated tray 5 is effected by electrical heat sealing elements on appropriate die members which move the upper tray 3 into the corrugated tray 5 and in appropriate die members which move the lower tray 7 towards the corrugated tray 5. This will be explained in further detail in due course. If desired the bonding may be effected by gluing or by use of R.F. or sonic welding ^• or by use of a heat banks or by dissolving the plastics material with a solvent and then urging the dissolved materials together and thus allowing bonding.

By inspecting Figure 4 it can be seen that the upper tray 3 is bonded to the corrugated tray 5 at locations 11 i.e. on the crests of the corrugations. It can also be seen that the lower tray 7 is bonded to the corrugated tray 5 at the locations 13 i.e. at the troughs of the corrugations. Thus, the pattern of heat sealing elements which is provided in the die members is arranged to align with the crests 11 and troughs 13. Typically, the heat bonding is effected by electric impulse heating of appropriate electrical heating elements on the surfaces of the die members although others form of bonding as recited above are possible.

In Figure 5, there is shown a close-up transverse cross-sectional view of one lower corner of the tray 2 of a further embodiment. In this embodiment, the upper tray 3 has a series of openings 15 through the platform 9. Also, the corrugated tray 5 has a series of openings 17 therein which are aligned with the openings 15 in the upper tray 3. Thus, any liquids which gravitate to the platforms 9 can pass through the openings 15 and 17 and be caught in the lower tray 7. In this connection, the lower tray 7. is shaped with a longitudinally extending ridge 19. The corrugated tray 5 is also shaped with a generally stepped corrugation part 21. The stepped corrugation part 21 and the ridge 19 extend continuously along the lowermost edge of each side of the tray 2 along the platforms 9. A liquid or gas absorbing material 23 is placed in the lower corner of the lower tray 7 against the ridge 19 and locates in the stepped corrugation part 21 of the corrugated tray 5. If desired of material 23 can be placed between the upper tray 3 and the intermediate tray 5. Thus, the liquid or gas absorbing material 23 is retained in the lowermost corner of the tray 2. Accordingly, any liquids or gas which pass through the openings 15 and 17 are absorbed within the liquid or gas absorbing material 23 and are not free to flow across the bottom surfaces of the tray 2 or to contaminate the food. The liquid or gas absorbing material 23 can be of type of material suitable for absorbing liquids or gas which emanate from foods. Typical examples being an absorbent paper pad for absorbing liquids. If desired the pad may be chemically treated to absorb liquids or to absorb gases such as CO- or ethylene. A typical chemical for absorbing ethylene gases is potasium permangenate.

The provisions of the openings 15 and 17 also assists in the nesting relationship of the corrugated tray 5 within the lower tray 7 and of the upper tray 3 in the corrugated tray 5. In this instance, when the trays are relatively moved towards each other, air can escape through the openings 15 and 17 to allow satisfactory nesting without trapping air therebetween and inhibiting close mating engagement of the surfaces of the upper tray 3 with the corrugated tray 5 and of the corrugated tray 5 with the lower tray 7. Thus effective bonding at the crests 11 and the troughs 13 is possible.

Referring now to Figure 6, there is shown a side elevation schematic view of a _#typical apparatus used for producing packaged meat. In Figure 6 the various sections of the machine have been separated as follows :-

Section A Individual tray forming station.

Section B Tray assembly and bonding station.

Section C Food loading station.

Section D Gas flushing and lid sealing station. Section E Severing and discharging station. It can be seen that there are three webs of plastics material 30, 31 and 32 which are in strip form and unwound from rolls 33, 34 and 35 respectively. The webs of material 30, 31 and 32 are heated by heaters 65 (see Figure 7), and pass underneath appropriate dies 37, 37'; 38, 38^» and 39, 39' which produce respectively, the upper tray 3, the corrugated tray 5 and the lower tray 7. The so-formed trays 3, 5 and 7 are still attached to the webs 30, 31 and 32 and pass into the tray assembly and bonding station B. Here, the upper tray 3 is severed from web 30 and the lower tray 7 is severed from web 32 by knives 70. The trays 3 and 7 are then advanced towards the corrugated tray 5 where they nestle together. Appropriate dies 50 and 51 are provided to receive the upper tray 3 and the lower tray 7 and to move them to the nested position. The dies 50 and 51 are provided with impulse heat sealing elements means in the form of electrically heated elements in the surfaces of the dies 50 and 51 which effect bonding together of the upper tray 3 to the corrugated tray 5 and the corrugated tray 5 to the lower tray 7. The completed trays 2 then pass into a food loading station C where food 53 is placed into the trays 2. It is noted that the trays 2 are still integral with the web 31. The trays 2 and the food 53 pass into a gas flushing and lid sealing station D. The gas flushing and lid sealing station D can be of any desired type but one particularly preferred construction will be described in due course. A further web of material 57 is wound off a roll 59 and passes through the gas flushing and lid sealing station D. The web 57 is used to provide lids 6 (not shown in Figure 6) to the trays 2. The package, when suitably filled with gas and heat sealed, discharges from the gas flushing and lid sealing station D into the severing and discharge station E. Here, the packages ar severed from the web 31 and are suitably taken away an^*d stored.

Referring now to Figure 7 there is shown, in detail, the individual tray forming station A and the tray assembly and bonding station B for each of the various webs 30, 31 and 32. Here, it can be seen that web 30 is provided by unrolling the roll of plastics material from roll 33. Web 31 is provided by unrolling plastics material from roll 34 and web 32 is provided by unrolling plastics material from roll 35. Web 30 passes under respective rollers 60, 61 and 62 so as to align th respective webs 30, 31 and 32 generally horizontally. All the webs are vertically in line. The webs 30, 31 an 32 pass under heaters 65 which raise the temperature of the webs 30, 31 and 32 sufficiently to permit thermo forming of the various trays.

It can be seen that web 30 advances into a thermo forming area where an upper platen 37 depresses the web 30 into a lower generally cup-shaped die 37'. Similarly web 31 is advanced into a thermo forming station where an upper platen 38 is advanced to form a tray 5 by deforming the web 31 into a lower cup-shaped die 38' . Similarly, web 32 is advanced into a thermo forming station where an upper platen 39 is advanced to form a tray 7 in web 32 as it is depressed into a cup-shaped die 39'.

At this stage, the trays 3, 5 and 7 are integral with the respective webs 30, 31 and 32. It can also be seen that the platen 38 and the cup-shaped die member 38* are suitably corrugated in shape so as to produce corrugations in the tray 5.

If desired, the trays 3 and 7 can be corrugate and tray 5 can be plane. When the trays 3, 5 and 7 are advanced into the tray assembly and bonding station B, it can be seen thSt the upper tray 3 is severed by a knife 70 preferably at the same time as a platen 50 engages within the tray 3 and advances it to the position as shown in dotted lines adjacent web 31. Approximately simultaneously, the tray 7 is separated from the lower web 32 by knife 70, preferably when the lower die 51 is advanced upwardly to the position shown adjacent web 31. Here, the upper tray 3 is nested within the corrugated tray 5 and the corrugated tray 5 is nested within the lower tray 7. Each ^'of the dies 50 and 51 are provided with a pattern of elements on the surface thereof which corresponds generally to the positions of the crests 11 and troughs 13 of the corrugations. Thus, when the tray 3 is nested within the corrugated tray 5 and the corrugated tray 5 is nested within the lower tray 7, an electrical current can be supplied to the electric heating elements causing them to heat and thus cause bonding of the upper tray 3 to the corrugated tray 5 and of the corrugated tray 5 to the lower tray 7. The electrically heated bonding is known as impulse sealing in the packaging arts. This bonding preferably does not occur around the peripheral lips 3' , 5' or 7' but only along the side walls and bottom surfaces of the tray 2. Thus, an integrally connected tray 2 is formed from three distinct webs of plastics material. The tray 2 is still .integral with the web 31. The trays 2 then advance through the food loading station C into the gas flushing and lid sealing station D. Referring now to Figure 8 there is shown a side view of the gas flushing and lid sealing station D. Here a particularly preferred embodiment of gas flushing and sealing of the lid 6 is shown. In this construction, a web of plastics material 57 for the lids 6 is unwound from a roll 59 and the web 57 passes through a rectangular shaped opening 183 in a gas flushing member 185. The gas flushing member 185 extends parallel with the web 31 from which the trays 2 are provided. The gas flushing member 185 also extends between an upper chamber part 187 and a lower chamber part 189 of the gas flushing and lid sealing station D. The upper chamber part 187 carries a platen 151 therein. The upper chamber 187 is fixed in position but the platen 151 is movable downwardly therein. The lower chamber 189 is movable upwardly towards the web 57, as will be described later. The platen 151 carries a blade 191 at the side edge thereof which is closest to a guide roller 181 which guides the web 57 off the roll 59. The blade 191 is spring biased so as to extend downwardly below the lowermost edge face of the chamber 187. This is clearly shown in this figure. The blade 191 extends at least across the width of the trays 2. Air evacuation openings 193 are provided in the upper and lower chambers 187 and 189 respectively. A gas flushing inlet 195 is provided in the gas flushing member 185. Gases of the same nature as that described previously are introduced to the gas flushing member 185 and exit through outlets 200.

In operation, the trays 2 are formed in station B and are loaded with food in station C and then enter station D. Here, the lower chamber 189 is closed about the tray 2 and simultaneously air is exhausted from the chambers 187 and 189 through openings 193. During this process, the trays 2 are moved upwardly against the lower surfaces of the upper chamber 187. After a time sufficient to allow substantially all the air to escape within the chambers 187 and 189 and from within the tray 2, then the gas is introduced and allowed to pass from outlets 200 between the web 57 and the web 31 in which the trays 2 are still integrally connected. Thus, the gas fills the tray 2. It can be observed that the gas flushing member 185 has the peripheral wall portions of the opening 183 directly under the faces of the upper chamber 187 and the aligned faces of the lower chamber 189. Thus, when the lower chamber 189 is raised it presses the web 57 against the lower faces of the upper chamber 187, the peripheral wall portions of the gas flushing member against the web 1, the web 31 against the underneath peripheral wall portions of the gas flushing member 185, thereby sealing the web 1 relative to the web 57 at the left-hand side of Figure 8. At the right-hand side, the web 57 is pressed against the web 31 to provide a seal at that side. Accordingly, when air is evacuated from the chambers 187 and 189 it is also evacuated from the tray 2. Because the gas outlets 200 are then between web 57 and web 31 gas can be introduced to replace the air which is evacuated.

When the gas has been introduced, the heated platen 151 can be lowered thereby hermatically sealing, the lid 6 to the tray 2.

It can be observed, that because the blade 191 extends downwardly below the lowermost edge of the platen 151, it will contact the web 57 prior to the lowermost surfaces of the platen 151 touching the web 57. This will, in turn, cause the web 57 to be pressed downwardly against the lower web 31 so as to hold it in that position and not tend to cause it to lift and adhered to the platen 151 when the platen 151.is nearly at the fully depressed position. Thus, the web 57 will not be displaced from the desired sealing position.

Accordingly, the peripheral edges of the tray 2 are sealed to the upper web 57 with a lid 6. For this reason it is not necessary to seal the trays 2 around the peripheral lips 3', 5' or 7' at station B because they are sealed at this time. A gas flushing and sealing machine of this general type is covered in PCT Patent Application PCT/AU84/00131 - Publication No. WO 85/00339 - In the name of Atmosphere Packaging Pty. Ltd. Figure 9 is a sectional view, along line 9-9 of

Figure 8, and shows the general shape of the gas flushing member 185 and the opening 183 therein.

If desired, the choice of plastics materials for the various webs which constitute the upper tray 3, the intermediate tray 5 and the lower tray 7 may be such that a suitable chemical in liquid or gas or other form can be held between the various trays. Thus, it may be possible by appropriate choice of plastics materials to allow toxic gases which generate within the tray 2 to be transmitted through the plastics materials and be absorbed within the liquid or gas by passing through the plastics material and into those chemicals. Thus, the longevity of the contents can be enhanced by this process. Chemicals for this purpose are generally known in the food packaging arts.

Referring now to Figures 10 through 15, there is shown some possible variations of methods and packaging included with the broad aspects of the invention. Referring firstly to Figure 10 there is shown the tray material formed from an upper tray part 3, a corrugated intermediate tray part 5 and a lower tray part 7. These parts correspond with the tray parts shown in the previous embodiments. In Figure 10 there is shown one particular method used when forming the tray 2. In this embodiment the corrugated tray 5 is placed or nested in a lower tray 7 and an upper tray 3 is placed on top of the corrugated tray 5. Air is then evacuated from between the corrugations as shown by nozzles 102. This air evacuation draws the upper tray 3 towards the corrugated tray 5 and the lower tray 7 towards the corrugated tray 5. The contacting surfaces of all trays can then be suitably bonded.

Figure 11 shows a further embodiment where the corrugated tray 5 is bonded to the lower tray 7 prior to the bonding of the upper tray 3 thereto. In this embodiment an upper platen 101 with downwardly extending fingers 103 is pressed into the corrugations in the corrugated tray 5 and the corrugated tray 5 is then moved downwardly to engage with the lower tray 7. A lower platen 105 is then moved upwardly and pressure applied between the upper platen 101 and the lower platen 105. The bonding can be by any one of the methods noted above. If RF or high frequency bonding is to be effected then the fingers 103 will be arranged so that they can perform this function.

In Figure 12 there is shown a second step in the manufacture of the tray as shown in Figure 11. Here it can be seen that the corrugated tray 5 has been bonded to the lower tray 7 at points 108. The upper tray 3 is then moved downwardly towards the corrugated tray 5 and air is sucked from the space between the upper tray 3 and the corrugated tray 5. The air is sucked from that space by a suitable air evacuation nozzle 107. Because the air is sucked from that space, the upper tray 3 moves under the influence of air pressure to seat on the crests of the corrugated tray 5. The upper tray 3 can be bonded to the corrugated tray 5 by any of the bonding methods noted above. During the bonding process, air and/or any desired gas can be introduced into the space under the corrugations between the corrugated tray 5and the lower tray 7. The air and/or the gas can be introduced via a nozzle 109. Typically the air and/or gas which is introduced through the nozzle 109 has slight pressure above that of any forces applying the upper tray 3 onto the crests of the corrugations in the corrugated tray 5. In this manner the corrugated tray 5 is supported during the bonding of the upper tray 3 thereto.

Figure 13 shows an embodiment where a multiplicity of corrugated webs are bonded one on top of each other to provide a substantially strong corrugated structure for a tray. The teachings as shown in Figures 13 and 12 can be applied to produce a multiplicity of corrugated layers one after another. Referring now to Figure 14 there is shown how the upper tray 3 is nested within the corrugated tray 5 and how the corrugated tray 5 is nested within the lower tray 7. The nested relationship of all of these trays 3, 5 and 7 produce the tray 2. In the embodiment of Figure 14 it can be seen that the upper peripheral surface and/or lip 111 of each of the tray 3, 5 and 7 is generally planer. Air evacuation nozzles 113 can be placed between the trays as shown to suck the air therefrom as in the case of the embodiment of Figure 10 and/or to suck air therefrom and to introduce gas thereto as in the case of the embodiment shown in Figure 12. The nozzles 113 are generally as shown in Figure 15 and comprise a generally flat shaped nozzle with a central forward opening 115. The nozzles 113 are placed immediately adjacent the side edges of each of the trays 3, 5 and 7 and not within the peripheral lip portions thereof. By placing the nozzles 113* at the side edges as distinct from within the lip portions, there is no tendency for the nozzles 113 to upset the nesting relationship of the trays 3, 5and 7 and hence there will be a substantially good seal made between the upper tray 3, the corrugated tray 5 and the lower tray 7.

Claims

1. A generally rigid tray for use in packaging goods, said tray comprising at least a formed plastics material upper tray nested within a formed plastics material lower tray, either the upper tray or the lower tray or both being corrugated and the upper and lower tray being bonded to each other where the crests of the corrugations touch the other tray.

2. A tray as claimed in Claim 1, wherein there is a third tray in which said lower tray is nested and wherein said third tray is corrugated and wherein said third tray, is bonded to said lower tray where the crests of the corrugations touch.

3. A tray as claimed in Claim 1, wherein there is a third tray in which said lower tray is nested and wherein said lower tray is corrugated and said third tray is not corrugated and wherein said third tray is bonded to said lower tray where the crests of the corrugations touch.

4. A tray as claimed in Claim 2 or Claim 3, wherein there are apertures in at least said upper tray and wherein said lower tray or said third tray has liquid or gas absorbing material therein whereby to absorb liquids or gases which may escape or generate from goods packaged in said tray.

5. A tray as claimed in any one of the proceeding claims wherein the bottom of said upper tray is gable-like in shape so that any liquids which escape from goods packaged within said tray will gravitate to the lowest level of said gable-like shape.

6. A tray as claimed in Claim 5 and dependent on Claims 3 or 4, wherein said apertures are at the lowest level of said gable-like shape.

7. A method for producing a generally rigid packaging tray comprising: (a) forming an upper plastics material tray in a web of plastics material

(b) forming a lower plastics material tray in a web of plastics material

(c) providing corrugations in either or both trays at step (a) or (b)

8. A method as claimed in Claim 7, comprising forming a third plastics material tray with corrugations and nesting said lower plastics material tray in said third plastics material tray and bonding the lower and the third trays where the crests of corrugations touch.

9. A method as claimed in Claim 7, comprising forming a third plastics material tray with corrugations and wherein said lower plastics material tray is not corrugated and bonding the lower and third trays where the crest of the corrugations touch.

10. A method of any one of Claims 7 to 9, wherein the plastics material trays are produced by thermo forming in separate webs of plastics material.

11. A method of Claim 10 when dependent on Claim 8 or Claim 9, wherein the respective .trays are formed in separate webs of plastics material and wherein two of the trays are separated from their respective webs whilst the other tray is retained in said web and wherein there is relative movement of all three trays so that all three trays are nested together with said other tray.

12. A method as claimed in Claim 11, wherein the three trays are welded together where the crest of the corrugations touch.

13. A method as claimed in Claim 12, wherein the three trays welded together are then loaded with goods and moved to a lid sealing station where a lid is bonded thereto and wherein after bonding of said lid thereto, the so produced package is severed from said web.

14. A method as claimed in Claim 13, wherein said lid sealing station also comprises a gas flushing station where the so produced package is gas flushed prior to bonding of said lid so that it will contain said gas when the lid is bonded thereto.

15. A package produced by the method of any one of Claims 13 and 14.

16. A package, particularly, but not exclusively for fresh meat, comprising a generally rigid tray into which meat can be placed, said generally rigid tray being of laminated construction and being closed by a lid and wherein the package has a gas retained therein which will inhibit deterioration of the meat, said package being characterised by said tray comprising at least a formed plastics material upper tray nested with a formed plastics material lower tray, either the upper tray or the lower tray or both being corrugated and the upper and lower trays being bonded to each other where the crests of the corrugations touch the other tray said lid being, in the case of packaged meats or like foodstuffs, of plastics material which will be a barrier to gas therein, and in the case of fresh vegetables and the like foodstuffs, preferably of plastics material which will be pervious to at least oxygen.

17. A package as claimed in Claim 16, wherein there is a third tray from which said generally rigid tray is made said lower tray nesting in said third tray, said third tray being corrugated and bonded to said lower tray where the crests of said corrugations touch the said lower tray.

18. A package as claimed in Claim 16, wherein there is a third tray from which said generally rigid tray is made said lower tray nesting in said third tray, said third tray being corrugated and said lower tray not being corrugated, said third tray being bonded to said lower tray where the crests of the corrugations touch said lower tray.

19. A package as claimed in any one of Claims 16 to

18, wherein at least said upper tray has apertures therein and wherein said lower or said third tray has a liquid or gas absorbing material therein whereby to absorb liquids which may escape from goods packaged therein or to absorb gases which may escape or generate from the goods packaged therein.

20. A package as claimed in any one of Claims 16 to

19, wherein the bottom of said upper tray is gable-like in shape so that any liquids which escape from goods packaged therein will gravitate to the lowest level of said gable-like shape.

21. A package as claimed in Claim 20 when dependent on Claims 18 or 19, wherein said apertures are at the lowest level of said gable-like shape.

22. A method as claimed in any one of claims 7 to 14 wherein air is sucked from the space between said upper plastics material tray and said lower plastics material tray in order to cause the crests of the corrugations to be urged together between the trays during said bonding.

23. A method as claimed in Claim 23 wherein a gas is introduced under pressure between said upper plastics material tray and said lower plastics material tray during bonding of said third tray.