GB1574145A

GB1574145A - Composite lid

Info

Publication number: GB1574145A
Application number: GB15883/76A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1976-04-20
Filing date: 1976-04-20
Publication date: 1980-09-03
Also published as: BE853772A; SE433070B; NO771353L; NO146275C; NL187619C; IE44915B1; DE2717298B2; IE44915L; NL7704299A; AU506977B2; DE2717298C3; AU2438377A; DK170477A; SE7704473L; NO146275B; CH614677A5; FR2348863B1; DE2717298A1; DK147935C; DK147935B

Abstract

A connection lid with a moulded-on edge for packaging containers, in which lid distortion and the occurrence of tension in the lid, caused by shrinkage of the moulded-on or cast-on edge (2), are prevented by preformed lines of weakness (13), the lid curving out along these lines when tension occurs. The lid is manufactured by cutting out the lid plate (1), applying the predetermined lines of weakness (13) in the plate, and casting on a terminating edge (2) along the periphery of the lid plate. <IMAGE>

Description

(54) cOMPOSITE LID (71) We, IMPERIAL CHEMICAL INDUS TRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Com- pany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to composite lids of the kind comprising a sheet of a first material and a rim moulded from a second material around the perimeter of the sheet.

Composite lids of this kind are suitable for closing cartons used for packaging various materials or articles offered for sale, e.g.

foodstuffs such as ice cream, or articles such as nails. A composite construction enables a rim shape to be accurately moulded from a flexible thermoplastics material such as poly ethylene, so as to provide a good fit around the mouth of the carton in known manner, while also providing a readily printable surface over the area of the lid enabling ready application of a decoration to provide customer appeal. The first material forming the sheet is generally cardboard, but various laminates may equally be used for this purpose. The second material forming the rim, and indeed forming the carton itself, is usually polyethylene, but various other injection-mouldable thermoplastics may be appli- cable also.

The composite lids are manufactured by shaping the sheets to the desired outlines, and stacking them in a magazine. The sheets are normally flat even though there may be tabs around the perimeter which are bent perpendicular at some stage during the moulding operation, and the decorations are usually applied before stacking. The sheets are then fed to an injection moulding machine where the rim is injection moulded around the perimeter of the sheet. However, to minimise the quantities of materials required and to obtain a good sealing closure of the carton, the lids are made flexibly thin, and problems have arisen due to warping of the composite lids, in which the moulded rims become curved out of their intended plane.

According to one aspect of the invention there is provided a composite lid of the kind comprising a sheet of a first material and a rim moulded from a second material around the perimeter of the sheet, wherein the sheet has at least one line of weakness extending between each two adjacent corners of the lid and following a path which on leaving one corner diverges from the portion of the moulded rim joining the two corners and converges with the rim as it approaches the other corner, to allow the sheet to bend along the lines of weakness and thereby relieve stresses in the lid caused by shrinkage of the moulded rim. Relieving these stresses in this way, may reduce or even eliminate the warping referred to above.

Various configurations of lines of weakness may be used. For example, the path of the line may comprise a plurality of straight lengths with a sharp bend between adjacent lengths, or a smooth curve from one corner to the other, or a combination of straight lengths and curved lengths. The lines extending between each pair of corners may intersect, but in general it is preferred to leave an inner area remote from all the corners, free from any of the lines of weakness. This latter provides a relatively flat area with gentle downward curvature into the corners, and moreover by suitably restricting the lines of weakness to the areas around the perimeter, an advantageous shape may be provided wherein all areas of the sheet after bending along the lines of weakness to reduce the stresses, lie within the volume enclosed by the moulded rim.This enables the lids to be handled on conventional machines, e.g. when destacking the lids and placing them on filled cartons, whereas these machines may not always accept lids wherein the sheet portion is dished upwards beyond the top of the rim, i.e. when it extends outside the volume enclosed by the Tim.

According to a further aspect of the inven tion there is provided a method of manufacturing a composite lid comprising shaping a sheet of a first material to a desired outline and moulding a rim of a second material around the perimeter of the sheet, the improvement consisting in providing the sheet with at least one line of weakness extending between each two adjacent corners of the lid and following a path which on leaving one corner diverges from the portion of the moulded rim joining the two corners and converges with the rim as it approaches the other corner.

The lines of weakness may be formed by various known methods, such as by scoring or cutting the sheet part-way through its thickness for example. Alternatively a compressible sheet may be compressed along the path where the lines are required. Where the magazine and associated mould feeding mechanism allows, the sheet may be embossed to provide the lines of weakness.

Where the sheet is itself preformed by a moulding operation, the lines of weakness may be provided as regions of thinner material. A preferred method is one in which the sheet is provided with its lines of weakness before the rim is moulded around its perimeter, and it is generally convenient to provide the lines of weakness when preparing the sheet to the desired outline shape.

The lids may be used for closing moulded containers, having a base and sides in conventional manner. However, they may similarly be used at both ends of a tube of suitable section, thereby providing both base and lid.

The invention is illustrated by four specific embodiments described herein by way of example, with reference to the drawings accompanying the Provisional Specification in which Figures 1 and 2 are plan views of two square lids of similar configuration; Figures 3 and 4 are diagrammatical sections along the lines III III and IV IV respectively of Figures 1 and 2; Figure 5 is a plan view of a further square lid: Figure 6 is a diagrammatical section along the line VI VI of Figure 5; Figure 7 is a plan view of a triangular lid; and Figure 8 is a diagrammatical section along the line VIII VIII of Figure 7.

The composite lid shown in Figures 1 and 3 comprises a substantially square sheet 1 of a first material, e.g. cardboard, having a rim 2 moulded from a second material, e.g. polyethylene, around its periphery. The rim has a channel section, the sides of which extend from the base 3 by different amounts.

The outer side 4 extends the furthest, and has an integral latching ridge 5. The inner, shorter side 6 has a perpendicular flange 7 extending in the direction away from the outer side. The four corners 8, 9, 10, 11 are rounded. The sheet has correspondingly rounded corners, and upturned tabs 12 along each edge. Extending between adjacent corners, i.e. between 8 and 9, 9 and 10, 10 and 11, and 11 and 8, are lines of weakness 13, each comprising two straight portions meeting to produce a sharp bend 14. As each line leaves its corner, it diverges from the portion of the moulded rim 2 joining the two corners, and converges with the rim as it approaches the other corner. The sheet is bent along the lines 13 to give a dished profile as shown in Figure 3.

A composite lid as shown in Figures 1 and 3, is made by stacking sheets precut to the desired outline of a square with rounded corners and edge tabs 12, and provided with a design printed on one side.

Whilst cutting the outline, the printed side is cut part-way through to provide the lines 13 of weakness. The stacked sheets while still flat, are fed to the mould, and the rims injection moulded around the sheet with the edge tabs bent up as shown in the drawings.

On removal from the mould, the sheet automatically bends along the lines of weakness to relieve the stresses applied to the sheet by contraction of the rim as it cools.

The lid shown in Figures 2 and 4 is substantially the same as that shown in Figures 1 and 3 (and like numerals have been used for like parts), except that the lines 21 of weakness form smooth curves rather than dog legs. In both lids there is an inner area 22 remote from all the corners, which is free from any of the lines of weakness, and this produces a relatively flat area with gentle downward curvature into the corners. Moreover, as will be apparent from Figures 3 and 4, this leads to all the areas of the sheets lying within the volume enclosed by the moulded rim, the upper and lower edges of the rim showing on either side of the sheet in these sections.

Figures 5 and 6 show a lid which is similar to the previous two, except that all the lines of weakness 51 meet at the centre.

The effect of this is to dish the sheet to a greater displacement at the centre. This is more likely to stand proud of the moulded rim, and may then give handling problems with some conventional machines.

In Figures 7 and 8 is shown a triangular lid to illustrate how the invention may be applied to shapes other than the more usual square and other rectangular shapes. Like reference numerals have been used where appropriate.

WHAT WE CLAIM IS:- 1. A composite lid of the kind comprising a sheet of a first material and a rim

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tion there is provided a method of manufacturing a composite lid comprising shaping a sheet of a first material to a desired outline and moulding a rim of a second material around the perimeter of the sheet, the improvement consisting in providing the sheet with at least one line of weakness extending between each two adjacent corners of the lid and following a path which on leaving one corner diverges from the portion of the moulded rim joining the two corners and converges with the rim as it approaches the other corner. The lines of weakness may be formed by various known methods, such as by scoring or cutting the sheet part-way through its thickness for example. Alternatively a compressible sheet may be compressed along the path where the lines are required. Where the magazine and associated mould feeding mechanism allows, the sheet may be embossed to provide the lines of weakness. Where the sheet is itself preformed by a moulding operation, the lines of weakness may be provided as regions of thinner material. A preferred method is one in which the sheet is provided with its lines of weakness before the rim is moulded around its perimeter, and it is generally convenient to provide the lines of weakness when preparing the sheet to the desired outline shape. The lids may be used for closing moulded containers, having a base and sides in conventional manner. However, they may similarly be used at both ends of a tube of suitable section, thereby providing both base and lid. The invention is illustrated by four specific embodiments described herein by way of example, with reference to the drawings accompanying the Provisional Specification in which Figures 1 and 2 are plan views of two square lids of similar configuration; Figures 3 and 4 are diagrammatical sections along the lines III III and IV IV respectively of Figures 1 and 2; Figure 5 is a plan view of a further square lid: Figure 6 is a diagrammatical section along the line VI VI of Figure 5; Figure 7 is a plan view of a triangular lid; and Figure 8 is a diagrammatical section along the line VIII VIII of Figure 7. The composite lid shown in Figures 1 and 3 comprises a substantially square sheet 1 of a first material, e.g. cardboard, having a rim 2 moulded from a second material, e.g. polyethylene, around its periphery. The rim has a channel section, the sides of which extend from the base 3 by different amounts. The outer side 4 extends the furthest, and has an integral latching ridge 5. The inner, shorter side 6 has a perpendicular flange 7 extending in the direction away from the outer side. The four corners 8, 9, 10, 11 are rounded. The sheet has correspondingly rounded corners, and upturned tabs 12 along each edge. Extending between adjacent corners, i.e. between 8 and 9, 9 and 10, 10 and 11, and 11 and 8, are lines of weakness 13, each comprising two straight portions meeting to produce a sharp bend 14. As each line leaves its corner, it diverges from the portion of the moulded rim 2 joining the two corners, and converges with the rim as it approaches the other corner. The sheet is bent along the lines 13 to give a dished profile as shown in Figure 3. A composite lid as shown in Figures 1 and 3, is made by stacking sheets precut to the desired outline of a square with rounded corners and edge tabs 12, and provided with a design printed on one side. Whilst cutting the outline, the printed side is cut part-way through to provide the lines 13 of weakness. The stacked sheets while still flat, are fed to the mould, and the rims injection moulded around the sheet with the edge tabs bent up as shown in the drawings. On removal from the mould, the sheet automatically bends along the lines of weakness to relieve the stresses applied to the sheet by contraction of the rim as it cools. The lid shown in Figures 2 and 4 is substantially the same as that shown in Figures 1 and 3 (and like numerals have been used for like parts), except that the lines 21 of weakness form smooth curves rather than dog legs. In both lids there is an inner area 22 remote from all the corners, which is free from any of the lines of weakness, and this produces a relatively flat area with gentle downward curvature into the corners. Moreover, as will be apparent from Figures 3 and 4, this leads to all the areas of the sheets lying within the volume enclosed by the moulded rim, the upper and lower edges of the rim showing on either side of the sheet in these sections. Figures 5 and 6 show a lid which is similar to the previous two, except that all the lines of weakness 51 meet at the centre. The effect of this is to dish the sheet to a greater displacement at the centre. This is more likely to stand proud of the moulded rim, and may then give handling problems with some conventional machines. In Figures 7 and 8 is shown a triangular lid to illustrate how the invention may be applied to shapes other than the more usual square and other rectangular shapes. Like reference numerals have been used where appropriate. WHAT WE CLAIM IS:-

1. A composite lid of the kind comprising a sheet of a first material and a rim

moulded from a second material around the perimeter of the sheet, wherein the sheet has at least one line of weakness extending between each two adjacent corners of the lid and following a path which on leaving one corner diverges from the portion of the moulded rim joining the two corners and converges with the rim as it approaches the other corner.

2. A composite lid as claimed in claim 1 wherein an inner area of the sheet remote from all the corners, is free from any lines of weakness.

3. A composite lid as claimed in claim 1 or claim 2 wherein all areas of the sheet after bending along the lines of weakness to reduce the stresses, lie within the volume enclosed by the moulded rim.

4. A composite lid as claimed in any one of the preceding claims wherein the first material is cardboard.

5. A composite lid as claimed in any one of the preceding claims wherein the second material is polyethylene.

6. A composite lid substantially as hereinbefore described and as illustrated in any one of the drawings accompanying the Provisional Specification.

7. A method of manufacturing a composite lid comprising shaping a sheet of a first material to a desired outline and moulding a rim of a second material around the perimeter of the sheet, the improvement consisting in providing the sheet with at least one line of weakness extending between each two adjacent corners of the lid and following a path which on leaving one corner diverges from the portion of the moulded rim joining the two corners and converges with the rim as it approaches the other corner.

8. A method according to claim 7 wherein the sheet is provided with its lines of weakness before the rim is moulded around its perimeter.

9. A method acording to claim 7 or claim 8 wherein the lines of weakness are formed by cutting the sheet part-way through.

10. A method of manufacturing a composite lid substantially as hereinbefore described with reference to any one of the drawings accompanying the Provisional Specification.