CA2127650A1 - Lid to hermetically seal a container and a method for making same - Google Patents

Abstract

The disclosure herein describes a container lid which displays, on one face thereof, an annular pattern of separate bosses of thermoplastic adhesive, the bosses being so disposed relative to one another as to leave a gap therebetween whereby, when the lid is in a stacked dispensing relationship with similarly constructed lids, air presence is permitted between the edge of the lid to the center thereof thereby preventing surface adherence between successive lids as the lids are removed from the stack. On the other hand, the disposition and the volume of each boss are such that the thermoplastic adhesive covers the full pattern area as the lid is heat sealed to the rim of a container.

Description

2127~;50 TITLE OF THE lNV~ ION
Lid to hermetically seal a container and a method for making same.

FIELD OF THE lNV~:N~ION
The present invention relates to a lid formed of a thin sheet of plastics material for hermetically and peelably sealing plastic containers.

BACRGROUND OF THE lNV~L.lION
Containers for food stuff, such as dairy products, or for medicament, such as drug doses, are generally covered by planar closures which are formed of metallic foils, such as aluminum foil, molded plastics and the like. The peripheral edge of these closures, or lids, are coated with an adhesive bonding material or a heat sealable coating so that they may be affixed to the planar lip or rim of containers.

These lids are stacked in a dispensing magazine and are removed one by one by a lid destacking and feeding device which places them on containers where they are heat sealed to the rim thereof.

The dispensing of lids made of metallic foils is usually carried out without such problems as lids adhering to one another due to presence of embossing configurations usually found on such foils. On the other hand, with lids made of a thin sheet of plastics material, it has been observed that there exists a suction effect on the lid being removed adhering to its superposed lid in the magazine due to surface adherence;
S this is due to the absence of air entering behind the lid as it is removed from the magazine.

OBJECTS AND STATEMENT OF THE INVENTION
The present invention is concerned with overcoming the above problem of lids formed of thin sheet of plastics material by so configurating the lid that, during its removal from the stacking magazine, air entry is made possible between the lid being removed and its superposed lid to thereby prevent surface adherence between the two.

This is achieved by forming, on the underside of the lid, an annular pattern of separate bosses of thermoplastic adhesive, the bosses being so disposed relative to one another as to leave a gap therebetween whereby, when the lid is in a stacked dispensing relationship with similarly constructed lids, air circulation is permitted between the edge of the lid to the center thereof thereby preventing surface adherence between successive lids as the lids are removed from the stack. On the other hand, the disposition and the volume of each boss are such that the thermoplastic adhesive covers the full pattern area as the lid is heat sealed to the rim of a container.

It is also an object of the present invention to provide a method of making such lid.

The present invention therefore relates to a lid formed of a thin sheet or laminated sheets of plastics material, the lid having an underside coated, at its peripheral edge, with a pattern of thermoplastic adhesive to define a heat sealable marginal region allowing the lid to be hermetically sealed to a peripheral flange portion of a container. The pattern of adhesive consists of fine particles forming bosses so disposed relative to one another as to leave a gap therebetween whereby, when the lid is in a stacked dispensing relationship with similarly constructed lids, air circulation between the edge of a lid to be dispensed to a central region thereof is permitted thereby preventing surface adherence to a superposed lid as the lid is removed from the stack of lids.

The present invention is also concerned with a method of making a lid having a pattern of bosses along a marginal peripheral portion, comprising the steps of:
passing a strip of a thin sheet or laminated sheets of plastics material between a pair of rollers, including an upper pressure roller and a lower metal 21~765~

roller; the latter having a portion thereof extending in a bath of hot melt adhesive and having a cylindrical surface displaying an engraved area and a non engraved area;
scraping the hot melt from the surface of the lower roller prior to the film being passed between the rollers so that hot melt is removed from the non engraved area whereby, as the sheet is passed between the rollers, the hot melt in the engraved area is passed onto the sheet to form bosses;
chilling the bosses; and cutting the sheet to form lids having an embossed area along the marginal peripheral portion.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter.
It should be understood, however, that this detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a bottom plan view of a lid made in accordance with the present invention;

Figure 2 is a fragmentary elevation view of a container to which the lid of the present invention has been sealed;
Figure 3 is an elevational, partly cross-sectioned, schematic view showing a lid destackingdevice;
Figure 4 is an enlarged cross-sectional of parts of three superposed lids in a magazine;
Figure 5 is a schematic representation of the method of making the lid of the present invention;
Figure 6 is an elevational view showing a pressure roller and a pattern carrying roller; and Figure 7 is an enlarged cross-sectional view taken along lines 7-7 of figure 6.

DESCRIPTION OF PREFERRED EMBODIMENT
Referring to figure 1, there is shown a lid, generally denoted 10, made in accordance with the present nvention .

Referring also to figure 2, the lid has a top side 12 and an underside 14 which is adapted to be hermetically and peelably sealed to the peripheral flange or rim 16 of a plastic container 18.

The lid has been die cut to a shape corresponding to that of the flange 16 of the container and may include a finger gripping portion 20 also sealed 212765~

to a corresponding extension 22 of the flange of the container.

The present invention is concerned with providing a pattern of thermoplastic adhesive to the peripheral edge of the underside 14 of the lid. As can be seen in figure 1, the pattern of adhesive consists of an arrangement of fine particles 26 forming bosses which are separate from one another thus leaving a gap therebetween to thereby provide direct or indirect air circulation from the peripheral edge 28 of the lid to the unembossed region 30 in the central region of the underside of the lid.

Referring to figure 3, there is shown a lid magazine 32 in which are stacked a plurality of superposed lids, and a lid destacking device, generally denoted 34, which includes an arm 36 equipped with a lid contacting and retrieving element 38; this arm removes the lids from the bottom of the magazine 32 and moves (as indicated by arrow 40) to the position shown in dotted lines where the lid is ready to be deposited over the mouth of a container.

The representation of figure 4 shows in an exaggerated ways the superposition of the lids to indicate that an air gap exists between adjacent bosses so that, as a lid is retrieved by the device 34, the usual surface adherence between two contacting lids of thermoplastic material, such as polyethylene, is prevented so that only one lid is retrieved at a time.

Figure 5 is a schematic representation of the method of making the bosses on the underside of a lid.
From a reel 42, a strip 44 of a thin sheet of plastics material is passed by a first series of rollers 46, 48, 50 and 52 and then between a pair of vertically disposed rollers, including an upper pressure roller 54 and an engraving lower roller 56. The latter roller has a major portion thereof submerged in a bath 58 of hot melt material, such as a copolymer of ethylene and vinyl acetate (EVA), contained in a reservoir 60. The hot melt material collected by roller 56 is in part removed by a scraper 62 as further explained hereinbelow.

Referring to figure 6, the cylindrical surface of roller 56 is configured with an engraved areas 56a and a plurality of non engraved areas 56b. The area of these areas 56b is circular correspond to that of the non embossed area 30 on the underside of the lid (see figure 1) .

As can be seen in figure 7, the engraved area 56a consists of a series of a plurality of recesses 64, which may have various shapes, the configuration and 2127 ~5~

disposition of these recesses will be found on the underside of the lid.

In bath 58, the cylindrical surface of rotating roller 56 is covered with the hot melt adhesive.
However, scraper 62 removes the adhesive from the non engraved surfaces 56b, thus leaving adhesive only in the recesses 64. As the sheet 44 passes between rollers 54 and 56, the pressure on roller 54 causes the transfer of the adhesive from the recesses 64 onto the film, the lower face of which now has a configuration resembling that of the outer surface of roller 56. As illustrated in figure 5, the modified film 44' is then past onto a series of rollers (not shown) allowing the chilling of the bosses, then printing, if needed, on the top side of the film and to a die cutting operation which cuts the film into a series of lids having, for example, a configuration such as that shown in figure 1. These various steps are not illustrated as they are well known in the art.

Although the invention has been described above in relation to a specific form, it will be evident to a person skilled in the art that it may be modified and refined in various ways. For example, the pattern of bosses may have various configurations; the only requirement is that the bosses must not be continuous so as to block air circulation from the edge of the lid to _ 9 2 12765 0 the central region thereof. It is therefore wished to have it understood that the present invention should not be limited in interpretation, except by the terms of the following claims.

Claims (6)

1. A lid formed of a thin sheet of plastics material, said lid having a top side and an underside, said underside being coated, at its peripheral edge, with a pattern of thermoplastic adhesive to define a heat sealable marginal region allowing the lid to be hermetically sealed to a peripheral flange portion of a container, said pattern of adhesive consisting of an arrangement of fine particles forming bosses so disposed relative to one another as to leave a gap therebetween whereby, when said lid is in a stacked dispensing relationship with similarly constructed lids, air circulation between the edge of a lid to be dispensed to a central region thereof is permitted thereby preventing surface adherence to a superposed lid as said lid is removed from the stack of lids.

2. A lid as defined in claim 1, wherein said bosses are formed of a copolymer of ethylene and vinyl acetate.

3. A lid as defined in claim 2, wherein said plastics material is polyethylene.

4. A method of making a lid having a pattern of bosses along a marginal peripheral portion, comprising the steps of:
passing a strip of thin sheet of plastics material between a pair of rollers including an upper pressure roller and a lower roller; said lower roller having a portion thereof extending in a bath of hot adhesive melt; said lower roller having a cylindrical surface displaying an engraved area and a non engraved area;
scraping said hot melt from the surface of said lower roller prior to said film being passed between said rollers so that hot melt is removed from said non engraved area whereby, as said sheet is passed between said rollers, the hot melt in the engraved area is passed onto said sheet to form bosses;
chilling said bosses; and cutting said sheet to form lids having an embossed area along said marginal peripheral portion.

5. A method as defined in claim 4, comprising the step of printing the top side of said sheet prior to the cutting step.

6. A method as defined in claim 4, wherein said adhesive melt is a copolymer of ethylene and vinyl acetate.