Patent Application
20070095719
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.
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.
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.
a is a partial elevation view of the embodiment in
b is a partial plan view of the embodiment in
a and 5b are elevation views of notched steel rule knives used in the embodiment illustrated in
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
A multiple portion packaging tray 10 made in accordance with an embodiment of this invention is illustrated in
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
The method of making the multiple portion packaging tray 10 is illustrated in
The trim station 32, illustrated in an exploded schematic in
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.
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.
