Multiple portion packaging tray and method of making same

Abstract

A multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array, each comprising a receptacle and an integral peripheral flange extending from the receptacle, the flanges integrally connecting adjacent containers to one another along perforation lines comprising a series of alternating openings and land areas wherein the land areas are sized so that the containers are separated by tearing apart the flanges without propagating cracks across the flanges. The method of making a multiple portion packaging tray in a former comprising a form station and a separate trim station comprising the steps of thermoforming the multiple portion packaging tray and cutting the perimeter and perforation lines of the multiple portion packaging tray to create a series of alternating openings and land areas.

Description

FIELD OF INVENTION

This invention relates to plastic containers for use in packaging. In particular, this invention relates to packaging comprising an array of separably connected plastic containers that are easily separated and methods of making such containers.

BACKGROUND OF INVENTION

Use of single serve plastic containers is well known in the food product industry. These single serve containers are sometimes manufactured and sold in a multiple portion packaging tray comprising an array of separable containers. The containers are generally connected to one another along their flanges and may be broken apart by breaking the connection at the flanges. These containers work well when made of a relatively brittle plastic. Use of less brittle or more pliable polymers makes the containers more difficult to break apart. For some foods, brittle plastics, such as polystyrene, cannot provide the necessary protection and a high moisture barrier polymer is needed, such as polypropylene or polyethylene. Polypropylene and polyethylene are also generally lower cost materials than polystyrene. Traditionally, single serve packages made from polyolefins include secondary packaging, such as a cardboard sleeve, to form a multiple portion package. Connecting individual containers to form a multiple portion packaging without the use of secondary packaging, however, would deliver a substantial cost benefit. Accordingly, there is a need for an array of separably connected plastic containers made from less brittle and more pliable polymers.

Containers in the form of an array of separably connected plastic containers are typically formed from thermoforming processes well known to those of skill in the art. Examples of such thermoforming methods include solid phase pressure forming, melt phase forming, plug assist, vacuum forming, and drape forming. After thermoforming, the containers are transferred to a separate trim station, outside of the thermoforming station, to trim the containers.

SUMMARY OF INVENTION

This invention addresses the above-described need by providing a multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array. Each pliable polymer container comprises a receptacle and an integral peripheral flange extending from the receptacle, the flanges integrally connecting adjacent containers.

More particularly, this invention comprises perforation lines in the flanges as a means to easily separate the containers. The perforation lines comprise a series of alternating openings and land areas wherein the land areas are sized so that the containers are easily separated by tearing apart the flanges without propagating cracks across the flanges or compromising the containers' integrity and at the same time are robust enough to survive normal handling in a distribution process with out separating incidentally.

In addition, this invention encompasses a method for making a multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array. This method is performed in a former comprising a form station and a separate trim station and comprises the steps of thermoforming a pliable polymer sheet in the form station to create the multiple portion packaging tray and cutting the flanges in the trim station to form perforation lines having a series of alternating openings and land areas.

Other objects, features, and advantages of this invention will be apparent from the following detailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an array of separably connected plastic containers in accordance with an embodiment of this invention.

FIG. 2a is a partial elevation view of the embodiment in FIG. 1 illustrating a perforation line.

FIG. 2b is a partial plan view of the embodiment in FIG. 1 illustrating a perforation line along its longitudinal length.

FIG. 3 is a schematic representation of a system of making an array of separably connected plastic containers in accordance with an embodiment of this invention.

FIG. 4 is an exploded schematic representation of a trim station used in the embodiment illustrated in FIG. 3.

FIGS. 5a and 5b are elevation views of notched steel rule knives used in the embodiment illustrated in FIG. 3.

DETAILED DESCRIPTION

As summarized above, this invention encompasses a multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array. Such containers are frequently used to package individual servings of food products, although other uses are well known in the art. The containers are easily separable from the multiple portion packaging tray through the exertion of tensile force by hand. Embodiments of this invention are described in detail below and illustrated in FIGS. 1-5.

A multiple portion packaging tray 10 made in accordance with an embodiment of this invention is illustrated in FIG. 1. The multiple portion packaging tray 10 comprises a plurality of pliable polymer containers 12 configured in an array. The individual containers 12 comprise receptacles such as cups 14 surrounded by peripheral flanges 16. The flanges 16 integrally connect adjacent containers 12 to one another. The flanges 16 comprise perforation lines 18 wherein the perforation lines provide a means to easily separate the individual containers 12 from the multiple portion packaging tray 10. The perforation lines 18 may be formed within channels 19 formed in the flanges 16, as shown in FIGS. 1, 2a and 2b, or directly in non-channeled flanges. The channels 19 can be formed by any suitable means including but not limited to coining, and the like. The perforation lines 18 comprise a series of alternating openings 20 and land areas 22. The land areas 22 are sized so that the individual containers 12 are easily separated by tearing apart the flanges 16 at the tear lines 18 using tensile forces without propagating cracks across the flanges 16. Desirably, the land areas 22 can be easily pulled apart by hand yet are strong enough to survive normal handling and shipping. The perforation lines 18 extend along the flanges 16 in a longitudinal direction D as illustrated in FIG. 2b. The length L of the land areas 22 in the longitudinal direction D of the perforation lines 18 preferably ranges from about 15 mils to about 32 mils, more preferably from about 18 mils to about 22 mils. The length L of the land areas 22 in the longitudinal direction D of the perforation lines 18 is most preferably about 20 mils.

The multiple portion packaging tray 10 preferably comprises a pliable polymer material which is desirable in some packaging applications. For example, polyolefins are suitable pliable polymer materials for forming the packaging tray 10. Preferred polyolefins include polypropylene, high density polyethylene, and low density polyethylene. The most preferable polyolefin is polypropylene. The pliable polymers also may be coextruded with other materials. For example, polypropylene may be coextruded with ethylene vinyl alcohol by using ethylene vinyl acetate based tie layers for adhesion to the polypropylene. Other pliable polymer materials are also suitable.

The thickness T of the pliable polymer can vary and is preferably at least 3 mils and desirably ranges from 3 mils to about 40 mils, and more desirable ranges from about 5 mils to about 30 mils. As illustrated in another embodiment in FIG. 2a, the flanges 16 may be coined to form channels 19 so that the material thickness t at the perforation lines 18 is less than or equal to that of the remaining portion of the flanges.

The method of making the multiple portion packaging tray 10 is illustrated in FIG. 3. The multiple portion packaging tray 10 can be made using any suitable polymer sheet or film forming process, but is desirably made using a thermoforming process 24. Suitable thermoforming methods include solid phase pressure forming, melt phase forming, plug assist, vacuum forming, and drape forming. The thermoforming process 24 occurs in a former 28 comprising a form station 30 and a separate trim station 32. A pliable polymer sheet 26 is indexed through the form station 30 to create the formed multiple portion packaging tray 10 using thermoforming methods known to those skilled in the art. Desirably, the mold temperature of the former 28 is controlled using cold water flow through internal channels in the mold to quench the formed multiple portion packaging tray 10 so that there is crystallization of the polymer. The cooling process is well known to those of skill in the art.

The trim station 32, illustrated in an exploded schematic in FIG. 4, comprises steel rule knives 40 to cut the perimeter of the formed multiple portion packaging tray 10. The trim station 32 further comprises notched steel rule knives 42a and 42b, best shown in FIGS. 5a and 5b to create a series of alternating openings 20 and land areas 22 in the longitudinal direction of the respective tear lines 18. As illustrated in FIG. 5, the notched knives 42a and 42b comprise standard straight blade steel rule knife material with notches 44a and 44b sized to create land areas of a predetermined size so that the individual containers 12 are easily separated by tearing apart the flanges 16 at the perforation lines 18 without propagating cracks across the flanges 16. The perimeter knives 40 can also have small notches to create tabs attaching the multiple portion packaging tray 10 to the polymer sheet 26. The steel knives 40 and 42a and 42b touch a striker plate 46 to trim the perimeter of the multiple portion packaging tray 10 and to create the openings 20 and land areas 22 of the perforation lines 18. In another embodiment, the trim station 32 further comprises a punch and die system, well known to those of skill in the art, at the points where the individual containers 12 meet on the multiple portion packaging trays 10. The cutting by the steel knives 40 and 42a and 42b and punch and die system may be done simultaneously or in separate steps.

The multiple portion packaging trays 10 may be indexed to a stacking station 36 where the perimeter tabs are broken by pushing the array of containers 10 through the sheet 26 to a stacking chamber where they are counted and pushed to a packaging station 38.

The present invention is further illustrated by the following example, which is not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof which, after reading the description therein, may suggestion themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims.

EXAMPLE

A 30 mil 100% polypropylene sheet is used to make a multiple portion packaging tray. The polypropylene sheet is heated to 160° C. as it indexes through an oven into the form station at 4 second cycles. In the form station, the hot sheet may be formed using a variety of methods. The formed multiple portion packaging tray leaves the forming station, still attached to the sheet. The formed multiple portion packaging tray enters the trim station approximately 8 seconds after leaving the forming station. At the trim station, a lower platen moves up to the sheet level to capture the individual containers in a die plate. An upper platen containing steel rule knives, notched steel rule knives, and punches moves downward until it just touches the die plate and trims the perimeter of the multiple portion packaging tray as well as forms the tear lines in the flanges with alternating opening and land areas. The notches of the notched steel rule knives are desirably 20 mils in length. The upper and lower platens return to their initial positions and the multiple portion packaging tray proceeds to the stacking station. In the stacking station, a ram below sheet level pushes the multiple portion packaging tray up through the sheet, separating the multiple portion packaging tray from the sheet, and feeds the multiple portion packaging tray into a stacking chamber. The multiple portion packaging trays are collected in the stacking chamber and pushed onto a conveyor for packing.

It should be understood that the foregoing relates to particular embodiments of the present invention, and that numerous changes may be made therein without departing from the scope of the invention as defined from the following claims.

Claims

1. A multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array and each comprising a receptacle and an integral peripheral flange extending from the receptacle, the flanges integrally connecting adjacent ones of the containers to one another along perforation lines in the flanges having a series of alternating openings and land areas, wherein the land areas are sized so that the containers are separable by tearing apart the flanges without propagating cracks across the flanges.

2. The multiple portion packaging tray as in claim 1 wherein the pliable polymer containers comprise a polyolefin.

3. The multiple portion packaging tray as in claim 2 wherein the polyolefin is polypropylene.

4. The multiple portion packaging tray as in claim 2 wherein the polyolefin is high density polyethylene or low density polyethylene.

5. The multiple portion packaging tray as in claim 2 wherein the pliable polymer containers comprise a coextruded sheet comprising the polyolefin.

6. The multiple portion packaging tray as in claim 1 wherein each perforation line has a longitudinal direction and the length of each land area in the longitudinal direction of the respective perforation line ranges from about 15 mils to about 32 mils.

7. The multiple portion packaging tray as in claim 1 wherein each perforation line has a longitudinal direction and the length of each land area in the longitudinal direction of the respective perforation line ranges from about 18 mils to about 22 mils.

8. The multiple portion packaging tray as in claim 1 wherein each perforation line has a longitudinal direction and the length of each land area in the longitudinal direction of the respective perforation lines is about 20 mils.

9. The multiple portion packaging tray as in claim 1 wherein the land areas have a thickness from about 3 mils to about 40 mils.

10. The multiple portion packaging tray as in claim 1 wherein the land areas have a thickness from about 5 mils to about 30 mils.

11. The multiple portion packaging tray as in claim 1 wherein the flanges have channels and the perforation lines are formed in the channels so that the thickness of the land areas is less than the thickness of the flanges outside of the channels.

12. The multiple portion packaging tray as in claim 1 wherein the containers are made by thermoforming a pliable polymer sheet.

13. The method of making a multiple portion packaging tray in a former comprising a form station and separate trim station comprising the steps of:

thermoforming a pliable polymer sheet in a form station to create the multiple portion packaging tray comprising a plurality of pliable polymer containers configured in an array and each comprising a receptacle and an integral peripheral flange extending from the receptacle, the flanges integrally connecting adjacent ones of the containers to one another; and

cutting the flanges in the trim station to form perforation lines having a series of alternating openings and land areas.

14. The method as in claim 13 wherein the step of cutting comprises cutting the flanges with steel rule knives to trim the containers and cutting the flanges along the perforation lines with notched steel rule knives to form the open areas.

15. The method as in claim 14 wherein the notches of the notched steel rule knives have a length that ranges from about 15 mils to about 32 mils.

16. The method as in claim 14 wherein the notches of the notched steel rule knives have a length that ranges from about 18 mils to about 22 mils.

17. The method as in claim 14 wherein the notches of the notched steel rule knives have a length of about 20 mils.

18. The method as in claim 13 wherein the pliable polymer containers comprise a polyolefin.

19. The method as in claim 19 wherein the polyolefin is polypropylene.

20. The method as in claim 19 wherein the polyolefin is high density polyethylene or low density polyethylene.

21. The method as in claim 19 wherein the pliable polymer containers comprise a coextruded sheet comprising the polyolefin.