AU2759902A - Plastic container and method of manufacture - Google Patents

Description

AUSTRALIA

Patents Act 1990 Duncan Hopkins 09.0 0.

0 00 0 0 0 %0:0 00 :0.00 0 0. 0.:

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Plastic container and method of manufacture The following statement is a full description of this invention including the best method of performing it known to us:- Field of the Invention The present invention relates to plastic containers, such as those used to contain foodstuffs and small goods, and in particular provides a plastic container construction and method of construction.

Description of the Prior Art Generally, lightweight plastic containers are shaped by a process called thermoforming, in which a portion of a planar plastic sheet is heated and deformed to define a desired container shape. The portion of the sheet defining the desired container shape is then cut from the sheet for stacking and packaging.

One type of machine used in thermoforming processes is the radiant heat style of thermoforming machine. Radiant heat thermoforming machines typically feed a plastic sheet from a roll through a plurality of stations, by 15 way of moving chains having spikes which hold opposing edges of the plastic sheet. The first station is typically a radiant heat station, which heats the plastic sheet sufficiently for deformation to take place. The heated portion of sheet is then fed to a subsequent station, where a mould is brought to bear upon the heated sheet, and a sealing member is brought against an opposing side of the sheet to provide a seal around the mould. The heated sheet is then deformed to the shape of the mould, either by a vacuum applied through small holes in the mould surface, or by air pressure applied via the sealing S"member. The mould and sealing member are then withdrawn from the sheet to allow the sheet to be carried to a subsequent station where each moulded container is removed from the sheet by a cut line around the container. The cut line is made in portions of the sheet which remain within the plane of the sheet, and the plane defined by the cut line is known as the cutting plane.

Subsequent or additional stations may be provided, for example for stacking the moulded containers or performing other tasks.

A second type of machine used in thermoforming processes is the contact heat style of thermoforming machine. Contact heat thermoforming machines use rollers to feed a plastic sheet into position over a flat heating surface, and a mould member is brought down onto the sheet, acting with the heating surface to provide a seal around the mould. Air pressure is provided through small holes in the mould member to hold the plastic sheet against the heating surface until the plastic sheet has been sufficiently heated to allow deformation. Subsequently, the air in the mould is evacuated and the plastic sheet is deformed to the shape of the mould by air pressure introduced through small holes in the heating surface. Finally, the mould member is brought further down against the flat heating surface, in order to cut each moulded container from the plastic sheet. Accordingly, the cutting plane is defined by the heating surface in contact heat machines. The mould is then withdrawn and the moulded containers and sheet skeleton are removed from the station by further feeding of the plastic sheet.

Contact heat machines are significantly cheaper to purchase than radiant heat machines, which leads to lower unit cost. Further, contact heat machines, typically having only one station, occupy significantly less floor space, further reducing the cost of using such machines. However, the flat S"heating surface of contact heat machines limits the range of mould shapes which may be implemented, and in particular imposes the limitation that the plastic sheet can only be deformed to one side of the cutting plane.

S. By providing separate stations for heating and deformation, radiant heat machines allow the mould to define a container shape which extends S: both above and below the plane of the plastic sheet. However, radiant heat machines are typically significantly more expensive than contact heat machines, usually by a factor of around five or more. Further, radiant heat machines, having multiple stations, have a large footprint and occupy a large amount of space, increasing the cost of their use. Radiant heat machines often only become cost effective for very large volume applications.

Additionally, the use of spiked chains to hold opposing edges of the plastic sheet makes those edge portions of the sheet unavailable for use, leading to higher waste, and therefore higher unit cost.

Figure la is an elevation view of a first type of container 10 which can be formed by a radiant heat thermoforming machine. The container 10 is of unitary construction and includes a body portion 11 and a lid portion 12 which are joined by a hinge portion 13. The container is formed in the open position shown, from a plastic sheet positioned in the plane defined by the rim 16 of the body portion and the outer rim 17 of the lid portion.

The body portion 11 and lid portion 12 are formed with respective sealing portions 14, 15, such that when the container 10 is closed, the sealing portions 14, 15 cooperate to releasably hold the container 10 in a closed position and cooperate to provide a seal around the lateral periphery of the container.

The hinge portion 13 is of sufficient strength to hold the body portion 11 and lid portion 12 together, while being flexible so as to bend and/or fold as the container 10 is opened or closed. Hinge portion 13 includes a flexible raised central portion 18, to assist in providing flexibility so as to allow the container 10 to be moved from a formed position or open position, shown in Figure la, to a closed position. Figure lb illustrates the container 10 nearing a closed position.

Figure Ic is a partial cross-sectional view of the hinge portion region of the container 10 while in a closed position. As can be seen, hinge portion 13 has deformed to allow lid portion 12 to be brought into a nested position with .body portion 11. That is, the lid portion 12 is partially situated within a cavity defined by the body portion 11. In particular, as can be seen in Fig Ic, 15 hinge portion 13 deforms to such an extent that rim 16 of the body portion 11 :and outer rim 17 of the lid portion 12 are brought together while the container 10 is in the closed position.

Containers of this type provide a relatively good seal of the container, however it can be seen that the container shape extends both above and below the cutting plane, necessitating the use of a radiant heat thermoforming o" omachine.

Figure 2 illustrates a container 20 which extends only within and to .i one side of the cutting plane, and which may therefore be formed on a contact heat thermoforming machine. As shown in elevation view in Fig 2a, container 20 is of unitary construction and includes a body 21, a lid 22, and a hinge 23. One or more locking lugs 24 formed in the lid 22 are adapted to engage respective locking recesses 25 formed in the body 21. Hinge 23 is a simple fold line, defined by consecutive linearly aligned slits which are cut across the container so as to leave small flexible portions along the fold line.

Figure 2b is an illustrative elevation view of the container 20 in a closed position. Due to inherent stiffness and resilience in hinge 23, the lid 22 and body 21 deform slightly in the vicinity of the hinge 23, causing an air gap to remain between the lid and body even when the lugs 24 and recesses are engaged. This gap can allow contents of the container to escape even when the container is closed. Further, it can be seen that the lugs 24 and recesses 25 necessitate the use of significant additional material beyond that required for the body and lid, which leads to increased material cost per unit.

However, containers of the type shown in Fig 2 do allow use of a contact heat thermoforming machine, and the lugs and recesses 24, 25 are able to hold the container closed in a reasonably satisfactory manner.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Summary of the Invention According to a first aspect, the present invention provides a 15 thermoformed plastic container of unitary construction comprising a body portion, a lid portion and a hinge portion, wherein the hinge portion extends between a rim of the body portion and a rim of the lid portion, :..wherein, in a formed position, the body portion, hinge portion and lid portion extend only within and to one side of a nominal cutting plane, and the hinge portion separates the rim of the body portion and the rim of the lid portion by a length of the hinge portion, and wherein the hinge portion is formed such that, proximal to the hinge portion, the rim of the body portion and the rim of the lid portion are spaced by substantially the length of the hinge portion when the container is in a closed position, and such that the body portion and the lid portion adopt a nested position proximal to the hinge portion when the container is in a closed position.

By providing a hinge portion which holds the rim of the body portion and the rim of the lid portion at a distance when the container is closed, the present invention allows a container construction which extends to only one side of the cutting plane, while also allowing the body portion and lid portion to adopt a nested position proximal to the hinge portion when the container is in a closed position.

According to a second aspect, the present invention provides a thermoformed plastic container of unitary construction comprising a body portion, a lid portion and a hinge portion extending between a rim of the body portion and a rim of the lid portion, wherein, in a formed position, the body portion, hinge portion and lid portion extend only within and to one side of a nominal cutting plane, and wherein the body portion and lid portion comprise sealing means adapted to cooperate to releasably hold the container in a closed position, and wherein the hinge portion and sealing means are formed such that, when the container is in the closed position, the sealing means seals the container proximal to the hinge portion.

Embodiments of the second aspect of the present invention are advantageous in the provision of a container which may be formed by use of a contact heat thermoforming machine, and which has a hinge portion .formed to allow sealing of the container proximal to the hinge portion.

According to a third aspect, the present invention provides a method of 15 using a contact heat thermoforming machine to form a plastic container of unitary construction, comprising the step of: forming a container comprising a body portion, a lid portion, and a hinge portion extending between a rim of the body portion and a rim of the S.lid portion such that, proximal to the hinge portion, the rim of the body portion and the rim of the lid portion are spaced by substantially a length of the hinge portion when the container is in a closed position, and such that the body portion and lid portion adopt a nested position proximal to the hinged portion when the container is in a closed position.

o The method of the third aspect of the present invention is advantageous in providing a method of using a contact heat machine in the manufacture of a container which allows nested positioning of the body portion and lid portion proximal to the hinge. Previously, nested positioning proximal to a hinge has only been possible by forming containers which extend both above and below a cutting plane, which necessitated the use of radiant heat thermoforming machines.

In preferred embodiments of the invention, the hinge portion may comprise a generally planar portion between the lid portion and the body portion, wherein a first fold line is defined proximal to the body portion and substantially parallel to a local portion of the rim of the body portion, and wherein a second fold line is defined proximal to the lid portion and substantially parallel to a local portion of the rim of the lid portion. The length of the hinge portion in such embodiments will typically be substantially equal to the shortest distance between the first and second fold lines. The first and second fold lines are each preferably defined by linearly aligned slits cut across the hinge portion, so as to leave relatively small flexible portions along that fold line which allow folding while retaining the lid portion and body portion.

Preferably, sealing means of the lid portion and the body portion cooperate to provide a seal around substantially an entire lateral periphery of the container.

It will be appreciated that the ability for the body portion and lid portion to adopt a nested position proximal to the hinge portion when the container is in a closed position is advantageous, in that sealing ribs of the body portion and lid portion may interact both to hold the container in a closed position, and to provide a seal around part or substantially all of the 15 periphery of the container. Further, it will be appreciated that the body portion and the lid portion may adopt the nested position by virtue of the body portion being situated at least partially within a cavity defined by the lid portion, or alternatively, by virtue of the lid portion being situated at least partially within a cavity defined by the body portion.

In preferred embodiments, substantially the entire rim of the body portion is situated within a cavity defined by the lid portion when the container is in a closed position. In particular, the portion of the rim of the body portion which is proximal to the hinge portion is preferably situated within the cavity defined by the lid portion.

In particularly preferred embodiments of the present invention, the container is sealed by interaction of the rim of the body portion with sealing means of the lid portion. In such embodiments, the sealing means of the lid portion preferably comprises an inwardly extending rib around the periphery of the lid, adapted to allow the rim of the body portion to be placed behind the rib and to hold the rim in that position.

In alternate embodiments of the invention, the body portion may have a first sealing portion and the lid portion may have a second sealing portion, and wherein the first and second sealing portions are adapted to releasably hold the container in a closed position. The sealing portions may extend substantially entirely around a periphery of the container, or may be positioned at one or more distinct positions around the lateral periphery of the container.

In some embodiments of the invention, the hinge portion may meet the rim of the lid portion and the rim of the body portion.

It is to be appreciated that a container in accordance with the first or second aspect of the invention may be formed by use of a contact heat thermoforming machine, allowing containers of this type to be produced on a significantly less costly machine, allowing shorter production runs and/or lower unit cost. However, containers in accordance with the first and second aspects of the invention may also be formed by use of a radiant heat thermoforming machine.

Brief Description of the Drawings An embodiment of the invention will now be described with reference 15 to the accompanying drawings in which: Figures la, lb and ic illustrate a prior art container extending both above and below a cutting plane; Figures 2a and 2b illustrate a prior art container extending only within and to one side of a cutting plane; and Figures 3a, 3b and 3c illustrate a plastic container in accordance with the present invention.

Detailed Description of the Preferred Embodiments Figure 3a is an elevation view of a thermoformed plastic container in accordance with the present invention. The container 30 is of unitary construction and comprises a body portion 31, a lid portion 32 and a hinge portion 33 extending between a rim 34 of the body portion 31 and a rim 35 of the lid portion 32. In the formed position, as shown in Fig 3a, the body portion 31, hinge portion 33 and lid portion 32 extend only within and to one side of a nominal cutting plane, indicated by 36.

The hinge portion 33 is a planar portion between the lid portion 32 and the body portion 31, wherein a first fold line 37 is defined proximal to the body portion 31 and is substantially parallel to a local portion of the rim 37 of the body portion 31. A second fold line 38 of the hinge portion 33 is defined proximal to the lid portion 32 and is substantially parallel to a local portion of the rim 35 of the lid portion 32. The length of the hinge portion 33 is equal to the shortest distance between the first fold line 37 and second fold line 38.

The first and second fold lines 37, 38 are each defined by linearly aligned slits cut across the hinge portion 33 so as to leave relatively small flexible portions along that fold line. The hinge portion 33 separates the rim 34 of the body portion 31 and the rim 35 of the lid portion 32 by the length of the hinge portion 33.

The hinge portion 33 allows the container 30 to be moved between open and closed positions, as shown occurring in Fig 3b. It can be seen that folding occurs along fold lines 37, 38, while little or no flexing or bending occurs in the remainder of the hinge portion 33.

The hinge portion 33 is formed such that, proximal to the hinge portion 33, the rim 34 of the body portion 31 and the rim 35 of the lid portion 32 are spaced by substantially the length of the hinge portion 33 when the container 30 is in a closed position, as shown in Fig 3c.

15 From Figure 3c, it can be seen that the container 30 allows the body portion 31 and lid portion 32 to adopt a nested position proximal to the hinge portion 33 when the container is in a closed position. Further, it can be seen that the hinge portion 33 holds the rim 34 of the body portion 31 at a distance S. from the rim 35 of the lid portion 32 when the container is closed. It is also to be noted that the container 30 shown in Figures 3a to 3c allows sealing to occur around substantially an entire lateral periphery of the container, and in particular allows sealing to occur proximal to the hinge 33.

From Figure 3a it can be seen that the present embodiment of the invention has a construction which extends to only one side of the cutting plane 36, allowing formation of the container 30 by a contact heat thermoforming machine.

In accordance with the method of the third aspect of the present invention, a contact heat thermoforming machine may be used to form a plastic container of the type shown in Figure 3 by performing the step of forming the container 30 comprising body portion 31, lid portion 32, and hinge portion 33 such that, proximal to the hinge portion, a rim of the body portion and a rim of the lid portion are spaced by substantially a length of the hinge portion when the container is in a closed position.

In more detail, it is anticipated that the method of forming such a container will include the steps of: feeding a plastic sheet into position over a flat heating surface of the contact heat thermoforming machine; lowering a mould member onto the sheet such that the mould member acts with the heating surface to provide a seal around the mould; providing air pressure through small holes in the mould member to hold the plastic sheet against the heating surface until the plastic sheet has been sufficiently heated to allow deformation; deforming the plastic sheet to the shape of the mould by evacuating air in the mould and introducing air pressure through small holes in the heating surface; cutting the container thereby formed from the plastic sheet; withdrawing the mould member from the plastic sheet while providing some air pressure through the mould to discharge the sheet from the mould member; and removing the moulded container and sheet skeleton from the station by further feeding of the plastic sheet.

:As noted previously herein, contact heat machines are significantly cheaper to purchase than radiant heat machines, which leads to lower unit cost. Further, contact heat machines, typically having only one station, 15 occupy significantly less floor space, further reducing the cost of using such S. machines. Although the flat heating surface of contact heat machines limits the range of mould shapes which may be implemented, and in particular imposes the limitation that the plastic sheet can only be deformed to one side *of the cutting plane, the present invention provides a container and method of forming such a container which allows use of a contact heat machine while *.:providing a container capable of nested positioning of the lid and body.

In the embodiment of the invention shown in Figures 3a to 3c, the body portion 31 and the lid portion 32 adopt the nested position by virtue of the body portion 31 being situated at least partially within a cavity defined by the lid portion 32. Further, substantially the entire rim 34 of the body portion 31 is situated within the cavity defined by the lid portion 32 when the container 30 is in the closed position. Additionally, the container is sealed by interaction of the rim 34 of the body portion 31 with sealing means 39 of the lid portion 32, sealing means 39 comprising an inwardly extending rib around a portion of the periphery of the lid portion 32, adapted to allow the rim 34 of the body portion 31 to be placed behind the rib and to hold the rim 34 in that position.

It will be appreciated that the sealing portion 39 may extend substantially entirely around a lateral periphery of the lid portion 32, or may be positioned at one or more distinct positions around the periphery of the lid portion 32. Additionally, where the lid portion is rectangular, the sealing portion 39 may extend along one or more sides of the lid portion 32.

Alternately, containers in accordance with the present invention may have no sealing means at all. For example, a container having the shape of a rectangular prism, for example as used for storing stationery such as Christmas cards, may be formed without any integral sealing means. Such containers may have a hinge having a hinge length equal to a height of the container, such that the lid portion adopts a nested position over the full height of the container. Such containers may be sealed by use of separate sealing means, such as an adhesive tab or the like.

It is to be appreciated that a container in accordance with the present invention may be formed by use of a contact heat thermoforming machine, allowing containers of this type to be produced on a significantly less costly machine, allowing shorter production runs and/or lower unit cost. However, containers in accordance with the first and second aspects of the invention 15 may alternately be formed by use of a radiant heat thermoforming machine.

The term "plastic" as used herein relates to any suitable material which can be worked by heating and deformation to manufacture a container in accordance with the present invention. For example, the container could be made of materials such as polypropylene, styrenes, PET or PVC.

Further, it is to be understood that terms such as 'seal', 'sealed' or the V, *like are not to be interpreted as defining a hermetic seal or pressure seal for the container. Those in the art will understand that materials suitable for thermoforming may be of limited strength and any seal provided may therefore be of a limited nature. Further, the nature of intended contents of a container may allow a seal which is only partial, in that the seal may have many gaps or air passages of significant size from outside the container to within the container, yet still provide a seal within the context of the intended use of the container. Such limited and partial seals are intended to be within the scope of the present invention.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the 12 specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

0 C.

C

o

Claims (39)

1. A thermoformed plastic container of unitary construction comprising a body portion, a lid portion and a hinge portion, wherein the hinge portion extends between a rim of the body portion and a rim of the lid portion, wherein, in a formed position, the body portion, hinge portion and lid portion extend only within and to one side of a nominal cutting plane, and the hinge portion separates the rim of the body portion and the rim of the lid portion by a length of the hinge portion, and wherein the hinge portion is formed such that, proximal to the hinge portion, the rim of the body portion and the rim of the lid portion are spaced by substantially the length of the hinge portion when the container is in a closed position, and such that the body portion and lid portion adopt a nested position proximal to the hinge portion when the container is in a closed position. 15

2. A thermoformed plastic container as claimed in claim 1, wherein the body portion and lid portion comprise sealing means adapted to cooperate to releasably hold the container in a closed position, and wherein the hinge .i portion and sealing means are formed such that, when the container is in the S" closed position, the sealing means seals the container proximal to the hinge portion.

3. A thermoformed plastic container as claimed in claim 1 or claim2, wherein the hinge portion comprises a substantially planar portion between the lid portion andthe body portion, wherein a first fold line is defined proximal to the body portion and substantially parallel to a local portion of the rim of the body portion, and wherein a second fold line is defined proximal to the lid portion and substantially parallel to a local portion of the rim of the lid portion.

4. A thermoformed plastic container as claimed in claim 3, wherein the first and second fold lines are each defined by linearly aligned slits cut across the hinge portion, so as to leave relatively small flexible portions along that fold line which allow folding while retaining the lid portion and body portion.

A thermoformed plastic container as claimed in any one of claims 1 to 4 wherein sealing means of the lid portion and sealing means of the body portion cooperate to provide a seal around substantially an entire lateral periphery of the container.

6. A thermoformed plastic container as claimed in any one of claims 1 to wherein the body portion and the lid portion adopt a nested position by virtue of the body portion being situated at least partially within a cavity defined by the lid portion.

7. A thermoformed plastic container as claimed in any one of claims 1 to wherein the body portion and the lid portion adopt a nested position by virtue of the lid portion being situated at least partially within a cavity defined by the body portion.

8. A thermoformed plastic container as claimed in any one of claims 1 to 6 wherein substantially the entire rim of the body portion is situated within a cavity defined by the lid portion when the container is in a closed position.

S9. A thermoformed plastic container as claimed in any one of claims 1 to 6 or claim 8, wherein the container is sealed by interaction of the rim of the body portion with sealing means of the lid portion.

10. A thermoformed plastic container as claimed in claim 9 wherein the sealing means of the lid portion comprises an inwardly extending rib around the periphery of the lid, adapted to allow the rim of the body portion to be placed behind the rib and to hold the rim in that position.

11. A thermoformed plastic container as claimed in any one of claims 1 to 7 wherein the body portion has a first sealing portion and the lid portion has a second sealing portion, and wherein the first and second sealing portions are adapted to releasably hold the container in a closed position.

A thermoformed plastic container as claimed in claim 11 wherein the first and second sealing portions extend substantially entirely around a periphery of the container.

13. A thermoformed plastic container as claimed in claim 11 wherein the first and second sealing portions are positioned at one or more distinct positions around the lateral periphery of the container.

14. A method of using a contact heat thermoforming machine to form a plastic container of unitary construction, comprising the step of: forming a container comprising a body portion, a lid portion, and a hinge portion extending between a rim of the body portion and a rim of the lid portion such that, proximal to the hinge portion, the rim of the body portion and the rim of the lid portion are spaced by substantially a length of the hinge portion when the container is in a closed position, and such that the body portion and lid portion adopt a nested position proximal to the hinge portion when the container is in a closed position.

The method of claim 14, wherein the step of forming further comprises forming sealing means adapted to cooperate to hold the lid portion and the body portion in a closed position.

16. The method of claim 15, wherein the step of forming the sealing means further comprises forming the sealing means such that, when the container is in a closed position, the sealing means seals the container proximal to the hinge portion.

17. The method of claim 15 or claim 16 wherein the step of forming the sealing means further comprises forming the sealing means such that, when the container is in a closed position, the sealing means seals the container around substantially an entire lateral periphery of the container.

The method of any one of claims 14 to 17, wherein the step of forming the hinge portion comprises forming a substantially planar portion between S"the lid portion and the body portion, defining a first fold line proximal to the body portion and substantially parallel to a local portion of the rim of the body portion, and defining a second fold line proximal to the lid portion and substantially parallel to a local portion of the rim of the lid portion. 20

19. The method of claim 18 wherein the step of defining each of the first and second fold lines comprises cutting linearly aligned slits across the hinge S. portion so as to leave relatively small flexible portions along that fold line :which allow folding while retaining the lid portion and body portion.

The method of any one of claims 14 to 19 wherein the step of forming the container further comprises forming the container such that the container adopts a nested position by virtue of the body portion being situated at least partially within a cavity defined by the lid portion.

21. The method of any one of claims 14 to 19 wherein the step of forming the container further comprises forming the container such that the container adopts a nested position by virtue of the lid portion being situated within a cavity defined by the body portion.

22. The method of any one of claims 14 to 20 wherein substantially the entire rim of the body portion is situated within a cavity defined by the lid portion when the container is in a closed position.

23. The method of any one of claims 14 to 20 or claim 22, wherein the container is sealed by interaction of the rim of the body portion with sealing means of the lid portion.

24. The method of claim 23 wherein the sealing means of the lid portion comprises an inwardly extending rib around the periphery of the lid, adapted to allow the rim of the body portion to be placed behind the rib and to hold the rim in that position.

The method of any one of claims 14 to 22 wherein the body portion has a first sealing portion and th elid portion has a second sealing portion, and wherein the first and second sealing portions are adapted to releasably hold the container in a closed position.

26. The method of claim 25 wherein the first and second sealing portions extend substantially entirely around a periphery of the container.

27. The method of claim 25 wherein the first and second sealing means are positioned at one or more distinct positions around the lateral periphery of S"the container.

28. A thermoformed plastic container of unitary construction comprising a body portion, a lid portion and a hinge portion extending between a rim of the body portion and a rim of the lid portion, 20 wherein, in a formed position, the body portion, hinge portion and lid portion extend only within and to one side of a nominal cutting plane, and wherein the body portion and lid portion comprise sealing means adapted to cooperate to releasably hold the container in a closed position, and wherein the hinge portion and sealing means are formed such that, when the container is in the closed position, the sealing means seals the container proximal to the hinge portion.

29. A thermoformed plastic container as claimed in claim 28, wherein the hinge portion comprises a substantially planar portion between the lid portion and the body portion, wherein a first fold line is defined proximal to the body portion and substantially parallel to a local portion of the rim of the body portion, and wherein a second fold line is defined proximal to the lid portion and substantially parallel to a local portion of the rim of the lid portion.

A thermoformed plastic container as claimed in claim 29, wherein the first and second fold lines are each defined by linearly aligned slits cut across the hinge portion, so as to leave relatively small flexible portions along that fold line which allow folding while retaining the lid portion and body portion.

31. A thermoformed plastic container as claimed in any one of claims 28 to wherein sealing means of the lid portion and sealing means of the body portion cooperate to provide a seal around substantially an entire lateral periphery of the container.

32. A thermoformed plastic container as claimed in any one of claims 28 to 31 wherein the body portion and the lid portion adopt a nested position when the container is in a closed position, by virtue of the body portion being situated at least partially within a cavity defined by the lid portion.

33. A thermoformed plastic container as claimed in any one of claims 28 to 32 wherein the body portion and the lid portion adopt a nested position when the container is in a closed position, by virtue of the lid portion being situated at least partially within a cavity defined by the body portion.

34. A thermoformed plastic container as claimed in any one of claims 28 to S"32 wherein substantially the entire rim of the body portion is situated within a cavity defined by the lid portion when the container is in a closed position.

A thermoformed plastic container as claimed in any one of claims 28 to 32 or claim 34, wherein the container is sealed by interaction of the rim of the body portion with sealing means of the lid portion.

36. A thermoformed plastic container as claimed in claim 35 wherein the .sealing means of the lid portion comprises an inwardly extending rib around the periphery of the lid, adapted to allow the rim of the body portion to be placed behind the rib and to hold the rim in that position.

37. A thermoformed plastic container as claimed in any one of claims 28 to wherein the body portion has a first sealing portion and the lid portion has a second sealing portion, and wherein the first and second sealing portions are adapted to releasably hold the container in a closed position.

38. A thermoformed plastic container as claimed in claim 37 wherein the first and second sealing portions extend substantially entirely around a lateral periphery of the container.

39. A thermoformed plastic container as claimed in claim 37 wherein the first and second sealing portions are positioned at one or more distinct positions around the lateral periphery of the container. Dated this 2 2 nd day of March 2002 Duncan Hopkins Patent Attorneys for the Applicant: F B RICE CO