AU582845B2

AU582845B2 - Cup rim and method

Info

Publication number: AU582845B2
Application number: AU56241/86A
Authority: AU
Inventors: Kenneth W. Baker
Original assignee: Fort Howard Cup Corp
Current assignee: Solo Cup Operating Corp
Priority date: 1985-04-16
Filing date: 1986-03-18
Publication date: 1989-04-13
Anticipated expiration: 2006-03-18
Also published as: GB2187083B; DE3690205T1; GB8629782D0; CA1275269C; GB2187083A; JPS63500164A; EP0217864A1; WO1986006045A1; AU5624186A

Description

- 1 -

CUP RIM AND METHOD

BACKGROUND OF THE INVENTION

This invention relates to an improved cup. Specifically, the invention concerns an improved rim structure for a cup made from a material having at least one foamed layer and at least one non-foamed layer.

It is understood by those familiar with the art that single use drinking cups for holding both hot and cold beverages can be fabri¬ cated from extruded expanded polystyrene sheet (commonly referred to as "foam"). When the foam material is suitably oriented in the machine direction during extrusion, cups may be fabricated from rec¬ tangular blanks which are formed into cylindrical sleeves by slightly overlapping the ends of the rectangular blank, heating the adjacent surfaces, and applying suitable pressure to produce an impervious sealed seam. The resulting cylindrical sleeve is shrunk to a frusto-eonical shape. In forming a two-piece cup, a polystyrene foam disc may be used to close the bottom circular opening of the frusto-eonical cup. Such a known cup and method of making the cup is disclosed, for example, in U.S. Patent No. 3,854,583. A known method and apparatus for forming such cups is disclosed in U.S. Patent No. 3,969,173.

A more recent development in cup technology permits the use of structures consisting of layers of different materials, for example, a foamed layer coincident with a non-foamed layer wherein the different layers have different properties. For example, one layer may be a polystyrene foam while the other layer is a non-foamed polystyrene layer forming a plastic skin. Cups made from a combined foamed and non-foamed plastic material generally have the foam layer - 2 -

on the inside of the cup and the solid plastic layer on the outside, which permits a glossy smooth outside surface more amenable to printing. When a multi-layered material having layers of different materials is used, however, fabrication of the cup, particularly the rim, becomes more difficult than with a conventional single material, such as foam.

When a multi-layered, multi-material sheet is fabricated into a cup, forming a smooth rolled rim around the mouth of the cup becomes difficult due to the difference in properties, such as stiffness, between the different materials. What generally results is a rim having an undesirable series of flat sections within the rim roll rather than a smooth curved contour. The resulting irregularly shaped rim makes it difficult to fit a standard lid on the cup without the lid leaking around the rim. The irregularly shaped rim also provides a less pleasing appearance.

Accordingly, it is an object of the present invention to provide a cup made from a multi-layered, multi-material sheet in which the ri m roll may be fabricated with a smooth curved contour. Additionally, it is a further object of the present invention to provide an improved method of making a smooth curved contour rim roll on a cup made from such a material. SUMMARY OF THE INVENTION

In accordance with the present invention, an improved cup-like container is disclosed. The container has a side wall, an open mouth defined by the upper portion of the side wall and closing means for closing the bottom of the side wall in a liquid tight manner, thus defining a conventional drinking cup container. The closing means may be any means commonly used and well-known in the prior art to make either one-piece cups or two-piece cups. Most drinking cups include a rim or thin tight bead around the mouth of the cup. The present invention provides a plurality of score lines formed in the side wall, parallel to the circumferential direction of the side wall, adjacent the - 3 -

open mouth defined by the upper portion of the side wall. The score lines are preferably formed by creasing the side wall material so that the score lines will weaken the side wall. The scored upper portion of the side wall is reversely folded into a thin tight bead which surrounds the open mouth of the cup-like container to form a smooth, curved rim.

Preferably, the cup is made from a coextruded material having a foamed plastic resin layer and a non-foamed plastic resin layer. The non-foamed layer may be either on the inside or on the outside of the cup according to specific end use requirements. The score lines are preferably formed in the direction of bending, that is, in the outside layer when a reversely folded rim is formed. A reversely folded rim is one which is curled towards the outside of the cup. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an elevational view partly in section of a cup-like container in accordance with the present invention.

Figure 2 is a detail of the side wall of the cup shown in Figure 1.

Figure 3 is a schematic view illustrating the formation of score lines in a web of material to be formed into a cup.

Figure 4 is a detailed view of the tool used to form the score lines.

Figure 5 is a detailed view of the score lines formed in a web of material.

Figure 6 is a fragmentary enlarged sectional view of a cup side wall and rim according to the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The preferred embodiment of a nestable insulated cup 10 is shown in Figure 1 constructed in two parts, including a sidewall 20 and a sealed bottom disc 11. Alternatively, cup 10 may be made as a one-piece cup in accordance with well-known manufacturing proce¬ dures. Cup 10 is manufactured using known techniques as disclosed in the U.S. patents cited above. In general, the rectangular side wall blanks are severed from a web of sheet material having a biaxial ori¬ entation, that is, an orientation in both the longitudinal and transverse directions. However, the orientations in each direction need not be to the same degree. A cylindrical sleeve is formed from the blank with the machine direction of the web extending circumferentially around the cylindrical sleeve. A liquid tight lapped seam is formed between the ends of the sleeve such as by heat sealing. The sleeve is then placed over a forming mandrel having an outer surface corresponding to the desired configuration of the inner surface of the side wall of the cup to be formed. The sleeve, while it is so positioned over the mandrel, is heated to cause it to heat shrink into conforming face-to- face contact with the forming surface of the mandrel. The shrunken sleeve is stripped from the mandrel. A separate bottom closure may be affixed to the side wall while the sleeve is still in position on the mandrel or after it is removed by any of several known cup manufacturing techniques. Alternatively, a one-piece cup may be formed.

Cup 10 contains a rolled, reversely curled rim shown generally at 12, and also shown in section at 13. Stacking shoulder indents 14, also shown in cross-section at 15, may be provided at the bottom of sidewall 20, as shown in Figure 1. Such indents are provided to improve nesting of one cup within another.

As shown in Figure 2, the cup body or sidewall 20 is preferably made from a rectangular blank of oriented polystyrene material extruded with a non-foamed skin layer 21 of solid polystyrene and a layer 22 of polystyrene foam coextruded with layer 21. Although polystyrene is a preferred material, other thermoplastic polymeric materials also may be used. Additionally, the invention is equally applicable to materials having more than two layers, such as a mate¬ rial having a layer of foamed material sandwiched between two layers of a non-foamed material. - 5 -

In accordance with the present invention, and using known fabri¬ cation techniques, a sheet consisting of a foamed plastic resin, such as polystyrene, is extruded from an annular die, in combination with a non-foamed plastic resin to form a coextruded material. Alternatively, the layers may be laminated rather than coextruded or formed using other fabrication techniques. Also, a multi-layer, i.e., a material having more than two layers may be used. Preferably, foamed layer 22 makes up approximatley 96% of the total caliper of the coextruded sheet and non-foamed or solid layer 21 approximates 4% of the total caliper. A separate extruder may be used to supply solid layer 21 by means of cross over pipes so as to surround the foamed extruded material just prior to exiting the annular die. Generally, the extruded layers are given a biaxial orientation in both the machine, i.e., lengthwise, direction as well as the transverse direction of the sheet of material, that when heated, a formed cylindrical sleeve will properly shrink into conformance with a mandrel. The orientation in the machine direction may readily be imparted to the web of material by engaging the material while it is at a suitable orientation tempera¬ ture between opposed counter rotating rolls which are driven at periph¬ eral speeds substantially in excess of the linear speed of the thermoplastic material leaving the extruder. Additional longitudinal ori¬ entation and transverse orientation is provided as the sheet leaves the extruder die, all as is well understood in the art.

As shown in Figure 3, a web 30 of coextruded material is scored in the area subsequently to be curled into rim 12 of cup 10 with a series of parallel lines 33. A driven wheel 31 having parallel bosses or projections 32 may be used to form score lines 33. Prefer¬ ably, projections 32 are positioned approximately 1/32" apart on centers contoured such that a .005" flat occurs as the edge of an included angle of 60 ° with a projected depth of 1/32". The preferred configu¬ ration of projections 32 is shown more particularly in Figure 4. The depth of score lines 33 may be further controlled by adjusting the - 6 -

driven wheel 31 towards or away from the web so that the scoring penetration of score lines 33 is enough to crease the solid layer 21 without cutting through layer 21, as shown in Figure 5. The score lines are formed in the direction of bending. When a reversely folded rim is used, as shown, the score lines are in whichever layer is on the outside of the cup sidewall.

Figure 6 illustrates rim roll 12 in detail showing score lines 33 formed in the upper portion of sidewall 20. As shown, the upper por¬ tion of sidewall 20 is reversely folded into a thin tight bead which surrounds the mouth of cup 10. In accordance with kno wn manufacturing processes, a rimming or curling tool presses the upper scored portion of sidewall 20 first downwardly and outwardly, and then is contoured to force the material back toward the cup sidewall, and then upwardly to finally provide a smooth rim curl contour. Scoring lines 33 cause a weakening of the more resistant solid sheet layer 21 during the curling operation allowing the softer outer foam layer to curl around in a generally circular fashion without buckling of the solid layer. Score lines 33 predetermine the position where creasing of the solid layer occurs during the ri m curling operation to prevent inconsistent, randomly deformed rim curl shapes. Score- lines 33 weaken solid layer 21 so that rim 12 will have a smooth more pleasing appearance. Also, the smooth uniform contour of rim 12 ensures superior dimensional reliability of the rim diameter and the rim vertical thickness, which are important for lid design and manufacture to a leak-tight fit. A conventional lid would not effectively seal a cup having a randomly deformed rim.

When solid layer 21 is on the outside of the finished cup as shown in Figures 1, 2 and 6, the outside surface of the finished fabri¬ cated cup permits a more pleasing glossy surface highly receptive to good quality printing using known flexographic or gravure printing techniques for decoration. Alternatively, solid layer 21 may be within the finished cup upon fabrication for certain end product applications. - 7 -

Although a preferred form of the invention has been described, the invention is not to be limited thereto. Various modifications may be made to the invention, which is limited only by the following claims.

Claims

- 8 -CLAIMS

1. A cup-like container having a sidewall, an open mouth defined by the upper portion of said sidewall, and closing means for closing the bottom of said sidewall in a liquid tight manner, the improvement wherein a plurality of score lines are formed in said sidewall adjacent said open mouth so that said score lines will weaken said sidewall; said score lines being formed parallel to the circumferential direction of said sidewall, and wherein said scored upper portion of said sidewall is rolled into a thin tight bead which surrounds the open mouth of the cup-like container.

2. A cup-like container as recited in claim 1 wherein said sidewall is made from a material having at least -one foamed plastic resin layer and at least one non-foamed plastic resin layer.

3. A cup-like container as recited in claim 2 wherein both said foamed plastic resin and said non-foam ed plastic resin are polystyrene.

4. A cup-like container as recited in claim 2 wherein said foamed plastic layer comprises more than 90% of the total thickness of said sidewalL

5. A cup-like container as recited in claim 2 wherein said non-foamed layer is on the outside surface of said sidewall and the foamed layer is on the inside surface of said sidewalL

6. A cup-like container as recited in claim 2 wherein said non-foamed layer is on the inside surface of said sidewall and the foamed layer is on the outside surface of said sidewall.

7. A cup-like container as recited in claim 2 wherein said score lines comprise a crease which does not penetrate through said non-foamed layer.

8. A cup-like container comprising: a sidewall made from a single sheet of a heat-shrinkable thermoplastic material having at least one foamed layer and at least one non- foamed layer, the ends of said sidewall being joined to one another to form a liquid tight seam extending from the top to the bottom of said container; a mouth at the top of said container defined by the upper portion of said sidewall; a plurality of score lines formed in one of said layers adjacent said mouth at said upper portion of said sidewall; and a thin tight bead formed by rolling said upper portion of said sidewall in the direction of said layer having said score lines.

9. A cup-like container as recited in claim 8 wherein said thermoplastic material is polystyrene.

10. A cup-like container as recited in claim 8 wherein said foamed plastic layer comprises more than 90% of the total thickness of said sidewalL

11. A cup-like container as recited in claim 8 wherein said non-foamed layer is on the outside surface of said sidewall and the foamed layer is on the inside surface of said sidewall.

12. A cup-like container as recited in claim 8 wherein said non-foamed layer is on the inside surface of said sidewall and the foamed layer is on the outside surface of said sidewalL

13. A cup-like container as recited in claim 8 wherein said score lines comprise a crease which does not penetrate through said non-foamed layer.

14. A method of making a smoothly curved rim for a cup-like container comprising the steps of: forming a plurality of score lines parallel to the circumferential direction of a web of material to be formed into a cup-like container; formi ng said web of material into a sealed cup-like container having a sidewall, an open mouth at the upper portion of said sidewall and a closed bottom portion at the bottom of said sidewall, said score lines being adjacent said open mouth; rolling said upper portion of said sidewall along said score lines into a thin, tight bead to form a smoothly curved rim which surrounds said open mouth.

15. A method as recited in claim 14 wherein said material is a material having at least one foamed layer and at least one non- foamed layer.

16. A method as recited in claim 15 wherein said step of forming said score lines comprises creasing one of said layers without penetrating through said layer.