GB2187129A - Method and apparatus for forming curled rims on cups - Google Patents

Abstract

A throw-away drinking cup vacuum-formed from sheet material, e.g. polystyrene, is first formed with a more or less curved flange around the mouth which has one or more radially-spaced, circumferentially- extending notches (17) in its inner or outer surface so that when the flange is curled into a rim of approximately circular cross-section, material can flow more easily than if the rings had not been formed and a good curled rim can be formed with little tendency to uncurl. A mould (13) used for forming the cup has, or is in combination with, an annular ring for defining the mouth of the cup which has one or more protrusions (16) which will produce notches or indentations when the cup is formed. <IMAGE>

Description

SPECIFICATION Cup rims This invention relates to methods offorming curled rims on cups, to the cups so formed and to the moulds of making such cups.

The invention has particular, but not exclusive, application to throw-away drinking cups formed by a vacuum forming process from heated sheet poly styrene material which is drawn into the female mould.

It is the practice with such cups and other cups to form the cup in a first stage in which the bottom and side are formed together with a more or less curved flange around the mouth followed by a second step in which theflange is fed to a curling machinewhich curlstheflangeintoasmooth neatcurled rim around the finished cup.

In practicethecurled rim is often notassatisfactory as is desired and it is an object of the present invention to provide a means for improving the form of the curled rim.

According to one aspect of the present invention in a method of forming a curled rim on a cup orthe like the rim is moulded with one or more rings or notches in its inner and/oroutersurface, and isthen curled while hot while the space defined by the rings or notches is filled by flowing material, or is expanded as the material stretches.

Because of the nature of the cup forming process the material from which the rim is formed tends to be thickerthan the material from which the bottom and side of the cup are formed and tends to be much nearerthe thickness of the original sheet material.

This means that when the rim is curled considerable heat has to be applied to get the material to flow sufficiently to form a proper curl. If following the curling the material is not sufficiently cooled the rim can tend to uncurl due to the "memory" ofthe material.

In any case the heating necessary to effect the curl tendsto make the process uneconomical.

By providing the rings or notches in the surfaces of the rim prior to curling in accordance with the invention, during curling less material has to be displaced because the rings or notches can be filled by displaced material or can allow the material to stretch. That in turn means that the rim material does not have to be heated so much during forming so that it is likely that the curl will remain without tending to uncurl and that less heat will be needed in the process.

Preferablythe material is heated just sufficiently to effect a satisfactory curl and after curling the material is cold enough to substantially prevent uncurling.

In one embodimentthere are at least two circumferential rings or notches radially spaced from one another in the undersurface of the uncurled rim.

In another embodiment there is at least one circumferential ring or notch in a mould ring for defining the outer/upper surface of the rim, so that the material can readily stretch during curling.

According to another aspect of the invention a cup orthe like has a curled rim with discontinuities in the inside or the curl where during curling material has flowed to fill preformed notches.

The underside of the curled rim is preferably generally in a horizontal plane.

There may be notches extending generallyvertically in the material forforming the rim.

According to a third aspect of the invention a mould forforming a cup orthe like has, or is in combination with, an annular ring for defining the mouth of the cup which is generally of part-circular or curved cross-section, and which has one or more circumferential protruding rings which will produce corresponding notches or indentations when the cup is formed on the mould.

The invention may be carried into practice in various way and one embodiment will now be described by way of example with reference to the accompanying drawings in which: Figure 1 isa diagrammaticsection showing howa drinking cup can be vacuum moulded from sheet polystyrene; Figure2 is a detail of Figure 1 to an increased scale showing how the conventional mould of Figure 1 can be modified in accordance with the invention; Figure 3 is a view of part of a cup as moulded using the mould of Figure 2; Figure 4 shows how a curl can be formed at the mouth ofthecupshown in Figure 3; Figure 5 is a diagram showing how the curl tended to beon priorartcups;; Figures 6 and 7 are respectively sections of details ofa mouldforforming an external notch in the rim material and on the cup rim after curling; Figures 8and 9 are similarviews of an alternative; and Figures 10and 11 areiiaresimilarviewsofanarrange- mentforforming vertical notches in the rim.

In vacuum forming drinking cups and the like sheet polystyrene is clamped by a clamping ring 12 around the top of a mould 13. The sheet polystyrene is heated and pressure differential is applied so that it is drawn into the mould 13 as indicated generally at 14 which shows an intermediate stage in the formation of the cup. On making contact with the walls of the mould the sheet polystyrene is chilled and the cup is formed in accordance with the contour of the mould 13.

Itwill be noted from Figure 1 that around whatwill be the mouth of the cup the sheet polystyrene is not stretched to anything like the same extent as the material forming the side walls and the bottom ofthe cup and also that the shape of the material around the mouth is defined by the shape of the mouth of the mould.

Figure 2 shows a detail ofthe mouth ofthe mould where there is an annular ring 15 of approximately semi-circular cross-section. In accordance with the invention the ring 15 is formed with one or more cir cumferentiallyextending ring projections 16, so that after the cup has been formed the mouth will have corresponding indentations 17 in the underside.

Afterthe stage of Figure 3 has been reachedthe cup is cut from the surrounding sheet material from which it is formed and is fed to a rim curling machine which may be of a number of different kinds in which the partly formed rim is passed through grooves in rollers cylinders or wheels orthrough a generally tapered mould so that it becomes more curled as shown in Figure 4 or Figure 5. It is necessary to heat the rim to form thefinal curl and in general the thicker the material to be curled the hotter it will have to be.

After leaving the curling machine unless the curl has been fully cooled it will tend to resile partly back to the form of Figure 3 and the final rim tended to be as indicated in Figure Sin prior proposals.

However, in accordance with the invention the formed but uncurled rim has the internal notches 17 so that during curling material does not have to be displaced to the same extent as would be the case if the notches were not there because the notches provide space forthe material to flow into. In consequ ence it is possible to effectcurling without heating the uncurled rim to the same extent as had previously been thought necessary.

In accordance with the invention the rim may be in aform after curling as shown in Figure4wherethe notches have been filled and the underside of the curl is generally in a horizontal plane with little tendencyto resile.

This produces a much more satisfactory curl in the sense that it tends to be more uniform, more pleasing to the eye and more effective with vending mach ineswhich pull onecupfrom another stacked into it by engagement around the curled rim.

In the example described there were two rings 16 forming corresponding notches 17 inthecup but there may be one, two,three, four or more rings and the actual positions of them will depend on the particular design of the cup and the thickness of the material, and will probably only be determined bytrial and error.

In the arrangements of Figures 6 and 7 the mould ring 15 is smooth surfaced but it cooperates with an upper ring 21 formed with a protruding circumferential ring 22 forforming a corresponding notch in the upper surface of the moulded cup. When the rim material is curled to the form shown in Figure 7 the circumferential notch simplifiesthe stretching of the material as shown at 23. Thattends to preventthe rim uncurling afterforming.

The arrangement of Figure 8 is similar, but in that casethe upper moulding ring 21 isformedwithtwo spaced circumferential rings 24 forforming two notches in the rim to assist reaching the curled stage shown in Figure 9. Again, the notches 25 assistthe curling and "loss of memory" of the sheet material.

Figure 10 shows another arrangement in which the upper mould ring 21 is formed with a circumferential ring ofvertically extending radially inward projections 26 forforming in the curled rim corresponding vertical notches or grooves 27 which allow for radial expansion and stretch.

Only some examples have been shown. In accordance with particular requirements there may be a combination of any of the notch arrangements described so that there could be notches both in the outer and the underfaces of the rim material before curling and possibilyvertically extending notches as well.

Claims (14)

1. A method of forming a curled rim on a cup or the like, in which the rim is moulded with one or more rings or notches in its inner surface, each ring or notch defining a space, and the rim is then curled while hot and capable of flowing, and the space defined by the rings or notches is filled by flowing material.

2. A method of forming a curled rim on a cup or the like, in which the rim is moulded with one or more rings or notches in its outer surface, and the rim is then curled while hot and the material stretches at the rings or notches.

3. A method as claimed in Claim 1 or Claim 2 in which the rings or notches extend circumferentially.

4. A method as claimed in Claim 3 in which there are at least two rings or notches which are spaced apart over the radial length of the rim material.

5. A method as claimed in any preceding claim in which the material is heated just sufficiently to support a satisfactory curl.

6. A method as claimed in any preceding claim in which after curling, the material is cold enough to prevent substantial uncurling.

7. A method offorming a curled rim on a cup or the like performed substantially as herein specifically described with reference to Figures 1 to 4, or 6 and 7, or 8 and 9, or 9 and 10 of the accompanying drawings.

8. A cup orthe like formed from sheet material and having a curled rim with regions where material has flowed to fill preformed notches, or stretched at preformed notches extending circumferentially in the rim.

9. A cup as claimed in Claim Bin which the underside of the curled rim is in a generally horizontal plane.

10. A cup as claimed in Claim 8 or Claim 9, in which there are circumferentially-spaced, verticallyextending notches in the rim.

11. Adrinkingcupformedofsheetmaterialsub- stantially as herein specifically described with refer enceto any of Figures 4,7,9 and 11, ofthe ac- companying drawings.

12. A mouldforforming a cup orthe like which has, or is in combination with, an annular ring for defining the mouth of the cup which is generally of part-circular or curved cross-section, and which has one or more circumferential ring protrusions which will produce corresponding notches or indentations when the cup isformed on the mould.

13. A mould as claimed in Claim 12 in which the, or each, protrusion is in a curved part of the ring which will define the part of the material forforming the underside of the curl.

14. A mould as claimed in Claim 12 in which the, or each, protrusion is in a curved part of the ring which will define the part of the material forforming the upper side of the curl.