GB2134871A - Covering of open-topped containers - Google Patents

Abstract

A method of covering an open- topped container having a peripheral dependant flange spaced from the container side wall with film comprises: covering the top of the container with a piece of film, the film overlapping the container at its rim; applying vacuum to the underside of the overlapping portion of the film to bring the film into engagement with at least the uppermost part of the rim of the container or to enhance such engagement; applying further vacuum to said overlapping portion to bring the overlapping portion into engagement with the dependent flange of the rim of the container or to enhance such engagement; and then removing surplus film below the free edge of said dependent flange. Apparatus for use in carrying out this method comprises means 7 for holding in position a container to be covered with film; means 10 for positioning a piece of film over the top of the container with the film overlapping the container at its rim; means 17 for applying a vacuum to the underside of the overlapping portion of the film to bring the film into engagement with at least the uppermost part of the rim of the container or to enhance such engagement; further means 15, 16 for applying vacuum to the overlapping portion of the film to bring the overlapping portion into engagement with the dependent flange of the rim of the container or to enhance such engagement; and means 31 for removing surplus film below the free edge of the flange. <IMAGE>

Description

SPECIFICATION Covering of open-topped containers The present invention relates to the covering of open-topped containers with films, particularly but not exclusively stretch film and shrink film.

Shrink film or shrink-wrap film is well known. A characteristic property of such film is that when suitably dispensed, e.g. from a roll, it tends to shrink or contract in area. Also the film tends to cling or adhere to articles to which it is applied.

The film, which is usually transparent, is hereinafter referred to as "shrink film".

It is known to cover open-topped containers with shrink film of other film for the purpose of packaging goods in their containers, e.g. to retain the goods in the containers and keep the goods clean and to provide a convenient package for retail customers to handle. Hitherto the practice has been to cover the top of the container with a piece of film considerably larger in area than the top of the container so that excess film overhangs the sides of the container and to fold the excess film around the sides of the container and underneath the bottom of the container.Not only does this result in excessively large amounts of film being wasted since the film at the sides of the container and underneath the container does not contribute to covering the open top of the container but the film at the sides of the container and underneath the container becomes wrinkled and multilayered and hence unsightly in appearance. It is necessary to provide the large excess of the film, to be folded around the sides of the container and underneath the container, so that the film is reliably held on the container and the packaged goods are accordingly held securely in the container.

An object of the present invention is to overcome the aforementioned disadvantages at least in respect of open-topped containers of the type specified below.

By "an open-topped container of the type specified" I mean an open-topped container having a rim of inverted-channel shape section.

Such a rim has a depending edge portion with a free edge spaced from the side wall or walls of the container to define a downwardly opening channel.

In accordance with a first aspect of the present invention, there is provided a method of covering an open-topped container of the type specified with film, the method comprising: covering the top of the container with a piece of film, the film overlapping the container at its rim; applying vacuum to the underside of the overlapping portion of the film to bring the film into engagement with at least the uppermost part of the rim of the container; applying further vacuum to said overlapping portion to bring the overlapping portion into engagement with the depending edge portion of the rim of the container; and then removing surplus film below the free edge of said depending edge portion.

It is to be understood that by "vacuum" I mean in a general sense simply reduced atmosphere pressure.

Preferably the further vacuum is applied from within the channel defined by the rim to bring the film into good engagement with the depending edge portion of the rim.

Preferably the removal of the surplus film below the free edge of the depending edge portion of the rim of the container leaves a band or strip of film below the free edge (and still being part of the film covering the top of the container) which band curls underneath the free edge so as to become disposed on the side of the depending edge portion facing the side wall or walls of the container. This provides a neat tidy-looking finish to the resulting package and assists in preventing unintentional removal of the film from the container.

The removal of the surplus film may be conveniently effected by using a heated wire to cut the surplus film from the remainder of the film, which is e.g. being fed from a roll.

When using presently available films in the method of the invention, it is preferable to warm the fim prior and/or during its application to the container to ensure that it securely clings to the container. To this end, preferably warm air is blown over the film at and adjacent the rim of the container whilst the film is being applied thereto to facilitate adherence of the film to the rim of the container.

According to a second aspect of the invention, there is provided apparatus for covering opentopped containers of the type specified with film, the apparatus comprising: means for holding in position a container to be covered with film; means for positioning a piece of film over the top of the container with the film overlapping the container at its rim; means for applying a vacuum to the underside of the overlapping portion of the film to bring the film into engagement withat least the uppermost part of the rim of the container; further means for applying vacuum to the overlapping portion of the film to bring the overlapping portion into engagement with the depending edge portion of the rim of the container; and means for removing surplus film below the free edge of the rim.

Preferably the first-mentioned means (the means for holding in position the container to be covered with film) comprises: a holder having a recess in which the container can be seated when the film covering is to be applied thereto.

Preferably the second-mentioned means comprises ducts opening on a platform arranged to surround and be disposed below the rim of the container to be covered with film, the ducts being for withdrawing air frorn beneath the overlapping portion of the film to bring the overlapping portion down towards the platform.

Preferably said further means for applying vacuum to the overlapping portion of the film comprise ducts arranged to open within the channel defined by the rim of the container to withdraw air from the channel.

Preferably, as mentioned above, the firstmentioned means comprise a holder having a recess in which the container can be seated.

Preferably a duct through which air can be withdrawn from the recess opens into the bottom of the recess and the recess is surrounded at its top by an upstanding lip through which the ducts referred to in the preceding paragraph extend. In use of the apparatus, when the container to be covered is seated in the recess, the lip protrudes into the downwardly opening channel at the rim of the container. When air is withdrawn from the recess through the duct opening into the bottom of the container, air is caused to be withdrawn from the part of the downwardly opening channel to the outside of the lip through the ducts in the lip.

Preferably the means for removing the surplus film comprises a wire surrounding the means for holding in position the container and means for heating the wire so that it can cut through the film and separate the surplus film from the remainder of the film. Preferably the wire is disposed to be spaced below the free edge of the rim of the container when held in position by the firstmentioned means.

In accordance with one feature of the present invention, in carrying out the method referred to above the container and the recess in the holder may be so relatively dimensioned that the lower portion of the containter is a loose fit in the holder i.e. there is a space between at least the lower portions of the side walls of the container and the inner surface of the recess. (The term "side walls" is intended to embrace a single side wall when the container is e.g. circular).

Since the container side walls normally incline outwardly and upwardly the space may be provided by the inner side surface of the recess in the holder being substantially vertical.

The holder may comprise metal sheeting providing the inner side surface of the holder.

As described above a duct through which air can be withdrawn from the recess may open into the bottom of the recess, the recess being surrounded at its top by an upstanding lip. This lip may be provided by the metal sheeting.

The provision of the space between the side walls of the container and the inner side surface of the recess in the holder may facilitate the withdrawal of air from the channel defined by the rim of the container through the duct opening into the bottom of the recess.

Moreover, when the space is to be provided between the side walls of the container and the inner side surface of the recess, the shape or dimensions of at least the lower portion of the container may be unimportant provided that the container can fit in the recess and said further means (for bringing the overlapping portion of the film into engagement with the depending edge portion of the rim of the container by applying vacuum to the overlapping portion) can function satisfactorily.

It will now be understood that the apparatus can thus be used to cover a variety of different shapes and dimensions of containers with film.

The ducts in the upstanding lip of the holder may comprise ducts spaced below the upper free edge of the lip, and/or may comprise ducts provided by the lip at its upper free edge being serrated or otherwise provided with spaced notches i.e. ducts which open at both ends on opposite sides of the lip and also open upwardly along their length.

The notches serve the same function as the ducts spaced below the upper free edge of the lip but enable the overlapping portion of the film to be more securely and firmly drawn against the depending edge portion of the rim of the container and may also serve to draw the film left beneath the depending edge portion of the rim towards the interior of the channel so that after surplus film has been removed, as described above, the film left below the depending edge portion is better able to curl up in the channel and against the depending web of the rim of the container.

The invention is further described below by way of example with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic sectional view of a container which can be covered with film by means of the invention; Figure 2 is a diagrammatic side view, partly in section of an apparatus according to the invention; Figure 3 is a vertical section through part of the apparatus at one stage in the operation of the apparatus; Figures 4 and 5 are similar to Figure 3 but at later stages in the operation of the apparatus; Figure 6 shows the container covered with film by use of the apparatus of Figures 2 to 5.

Figure 7 is a vertical section through part of another apparatus according to the invention at one stage in the operation of the apparatus; and Figure 8 is a view in the direction of arrow A in Figure 7 showing the lip of the holder.

In the drawings, like reference numerals indicate like parts.

Referring to Figure 1, a semi-rigid plastics container 1 is generally rectangular in plan and has a horizontal base 2 and four upstanding side walls 3 (only three of which are visible in the figure). The container is open-topped and at its rim has a horizontal outwardly extending web 4 and a depending web 5, both the webs 4 and 5 extending around the entire periphery of the container. As can be seen from the figure, the free edge 5' of the web 5 is spaced outwardly from the side walls 3 of the container so that a downwardly opening channel 6 is defined by the side walls 3 and the webs 4 and 5.

Normally the side walls 3 and the bottom of the container are ribbed to strengthen the container and to enhance the appearance of the container.

Referring to Figure 2, the apparatus shown therein comprises a holder 7 for containers to be covered with film dispensed from a roll 8, a film support tray 9 as shown, or a warming block, and a carrier frame 10.

The frame 10 is mounted on arms (not shown) so as to be movable along path P, whilst remaining horizontal, between the position shown in full lines, immediately above the support tray 9, and the position shown in broken lines, immediately above the holder 7.

A heating wire 20 is disposed between the block 9 and the holder 7 for cutting film dispensed from the roll 8 as described below.

Referring to Figure 3, the holder 7 is formed as a resin block having an upwardly opening cavity or recess 11 shaped to receive the body of a container such as shown in Figure 1. The holder 7 has at the top of the recess 11 an upwardly protruding lip 12 extending around the entire perimeter of the recess. A shoulder 1 3 is formed below the lip 12 and a horizontal platform 14 below the shoulder. An electrical heating wire 31 extends around the holder 7 just below the shoulder 5.

The lip 12 on its side 12' facing away from the recess 11 is undercut. Ducts 1 5 extend through the lip 12 from one side of the lip to the other.

A duct 1 6 opens centrally into the recess 11 at its bottom and is connected via a control valve to a source of vacuum.

Also ducts 17 open onto the platform 14 at intervals around the recess 11, the ducts 17 being connected to the source of vacuum through a control valve.

The frame 10 is rectangular in plan and is provided with ducts 1 8 also connected to the source of vacuum through a control valve, the ducts opening into the underside of the frame through inserts 1 8a of a gripping material.

Further ducts 19 are provided around the frame 10, these ducts being connected to a source of warm air through a control valve.

In use of the apparatus successive containers are covered with film in the following manner.

Throughout operation of the apparatus warm air is supplied through the ducts 1 9 to the frame 10.

Each container 1 to be covered and normally being filled with produce, e.g. fruit, vegetables or mushrooms, is placed in turn in the recess 1 of the holder 7. The container fits in the recess as shown in Figure 3 with the lip 12 of the holder projecting into the downwardly directed channel 6 of the rim of the container and with slight clearances, due to the presence of the ribs on the container and/or the relative dimensions of the container and the recess, between the container and the holder at the sides and bottom of the container.

Initially a length of film 21 unrolled from the roll 8 is laid across the tray 9, the frame 10 is positioned immediately above the tray 9 and vacuum is applied through the ducts 1 8 so that the unrolled film is held fast against the inserts 1 8a of the frame and is also prevented from contracting. Warm air is directed onto the film through the ducts 1 9. When the length of the film has been sufficiently warmed by the warm air, the frame 10 is moved (through the position shown in Figure 3) to the position shown in broken lines in Figure 2 and shown in full lines in Figure 4.

The length 21 of warmed film is thus carried by the frame 10 to lie over the top of the container.

Simultaneously by the movement of the frame 10 a further length of film is drawn from the roll 8 and laid across the tray 9 and as the frame 10 compietes its movement to the position shown in Figure 4 the film 21 being laid over the container is cut from the remainder of the film by the wire 20, which is heated. Throughout the movement of the frame 10 warm air is directed onto the film 21 through the ducts 1 9 so that the film stays warm and, when applied to the rim of the container, clings to it well.

Next the application of vacuum through the ducts 1 8 of the frame 10 is stopped and vacuum is applied through the ducts 17 to the marginal areas of the piece of film covering the container to draw the marginal areas 21' of the film down onto the platform 14 as shown in Figure 5, the frame remaining over the holder 7 to keep the film in tension against atmospheric pressure opposing the vacuum applied through the ducts 17 and to be applied through the ducts 1 5. At the same time, the rate of flow of heated air through the ducts 1 9 is increased to give increased heating of the film in the area of the webs 4 and 5 of the container thereby to assist the film in stretching and forming more easily around the webs 4 and 5.

Vacuum is then applied through the duct 16.

This vacuum is transmitted via the ducts 1 5 to the portion of the film overlapping the rim of the container to cause the film 21 to be drawn against the depending web 5 of the rim of the container, and at the same time the depending web is deformed inwardly by the vacuum towards the undercut side 12' of the lip 12 of the holder 7.

Next the wire 31 is heated and the film, which is held against the wire by the vacuum applied through the ducts 15, 1 6 and 1 7 and because of the inward deformation of the web 5, is cut through by the wire. The frame 10 is then returned to its initial position immediately above the support tray 9 and vacuum is again applied through the ducts 1 8 for the purpose described earlier.

The cut film left covering the container has d narrow marginal portion 21' below the depending web 5 of the rim of the container and this marginal portion, either spontaneously and/or assisted by the air being drawn through the ducts 15, curls up behind the web 5 and against the side of the web 5 facing the side walls 3 of the container. Figure 6 shows in section the container covered with the film.

The container thus covered with film is removed from the holder 7 either manually or by mechanical means (not shown) and the next container to be covered is inserted into the holder to be covered with film in the manner described.

The curling of the film under the rim of each container ensures a neat finish to the covering of the film and assists in preventing the film becoming inadvertently detached from the container. Furthermore the amount of film used to cover each container is relatively low since nQ film is wasted being folded underneath the container.

It is to be understood that the warming of the film prior to and during its application to the containers is desirable to ensure that it adheres well to the rims of the containers.

The apparatus may include means for controlling and timing the movement of the frame 10 and the application of vacuum through the ducts 16, 17 and 1 8, the supply of warm air through the ducts 1 9 and the heating of the wires 20 and 31 and the operation of mechanical means for removing the containers from the holder 7 so that the operation of the apparatus can be at least partially automated.

Each of the wires 20 and 31 is conveniently an electrical resistance wire which is heated as desired by passing an electric current through it.

The film used to cover the container may be stretch film, which is normally produced in plasticized polyvinylchloride (PVC), shrink film or other plastics film of e.g. polypropylene, polyester or polyethylene or a laminate material.

It will be appreciated that the containers to be covered by the film may be filled with products not only level or below the rim of the container but also well above the level of the rim.

The holder 7 may be cast from aluminium if a suitable material (e.g. polytetrafluoroethylene) is used to insulate the heated wire 31 from it.

The apparatus may be adapted so that a plurality of containers may be simultaneously covered with film.

The apparatus shown in Figures 7 and 8 is similar in construction and operation to the apparatus of Figures 2 to 3 except as described below.

Referring to Figure 7 the holder 1 4 is formed of a resin body 1 4a having a sheet metal liner 1 4b providing the lip 12 of the holder. It will be seen that the liner 1 4b is substantially vertical and that a space 30 is defined between the sloping side walls 3 of the container 1 and the liner 14b.

The lip 12 is provided not with ducts 1 5 in the form of bores as described above but with notches 15'. These are provided at intervals along the lip and extend from the one side of the lip to the other and open upwardly along their length.

It will be appreciated that the container 1 may be of any shape and dimensions provided that it fits into the recess 11 of the holder with the lip 12 projecting into the downwardly directed channel 6 of the rim of the container.

Moreover, the holder 14 shown in Figures 7 and 8 is considerably easier to manufacture than the holder shown in Figures 2 to 5 since complicated and accurate shaping of the resin to form the lip is avoided.

The notches 15' function similarly to the ducts 1 5 referred to above. However, after the film 21 has been drawn against the depending web 5 of the rim of the container, because the notches 15' are higher than the ducts 1 5, the portion of the film immediately below the depending web 5 may be drawn up by the vacuum applied through the duct 1 6 and notches 15' towards or into the interior of the channel 6 of the rim of the container.

After film 21 has been cut below the web 5 by the wire 31 to leave the marginal portion 21', the portion 21', either spontaneously and/or assisted by the air being drawn through the notches 15' curls up behind the web 5 and against the side of the web 5 facing the side walls 3 of the container.

This curling up may be facilitated by the film below the depending web having already, as described in the preceding paragraph, been drawn up towards or into the interior of the channel 6.

Claims (20)

1. A method of covering an open-topped container of the type specified herein with film, the method comprising: covering the top of the container with a piece of film, the film overlapping the container at its rim; applying vacuum to the underside of the overlapping portion of the film to bring the film into engagement with at least the uppermost part of the rim of the container or to enhance such engagement; applying further vacuum to said overlapping portion to bring the overlapping portion into engagement with the depending edge portion of the rim of the container or to enhance such engagement; and then removing surplus film below the free edge of said depending edge portion.

2. A method according to claim 1, wherein the further vacuum is applied from within the channel defined by the rim to bring the film into good engagement with the depending edge portion of the rim.

3. A method according to claim 1 or 2, wherein the removal of the surplus film below the free edge of the depending edge portion of the rim of the container leaves a band or strip of film below the free edge, which band curls underneath the free edge so as to become disposed on the side of the depending edge portion facing the side wall or walls of the container.

4. A method according to any preceding claim, wherein the removal of the surplus film is effected by using a heated wire to cut the surplus film from the remainder of the film.

5. A method according to any preceding claim, wherein the film is warmed prior to and/or during its application to the container.

6. A method according to claim 5, wherein warm air is blown over the film at and adjacent the rim of the container whilst the film is being applied thereto.

7. A method of covering an open-topped container of the type specified herein with film, substantially as described herein with reference to the accompanying drawings.

8. Apparatus for covering open-topped containers of the type specified herein with film, the apparatus comprising; means for holding in position a container to be covered with film; means for positioning a piece of film over the top of the container with the film overlapping the container at its rim; means for applying a vacuum to the underside of the overlapping portion of the film to bring the film into engagement with at least the uppermost part of the rim of the container or to enhance such engagement; further means for applying vacuum to the overlapping portion of the film to bring the overlapping portion into engagement with the depending edge portion of the rim of the container or to enhance such engagement; and means for removing surplus film below the free edge of the rim.

9. Apparatus according to claim 8, wherein the first-mentioned means comprises: a holder having a recess in which the container can be seated when the film covering is to be applied thereto.

10. Apparatus according to either of claims 8 and 9, wherein said further means for applying vacuum to the overlapping portion of the film comprise ducts arranged to open within the channel defined by the rim of the container to withdraw air from the channel.

1 Apparatus according to claims 9 and 10, wherein a duct through which air can be withdrawn from the recess opens into the bottom of the recess and the recess is surrounded at its top by an upstanding lip through which the ducts referred to in claim 10 extend.

12. Apparatus according to claim 11, wherein the ducts in the lip are provided by the upper free edge of the lip being serrated or otherwise provided with spaced notches.

1 3. Apparatus according to any of claims 8 to 12, wherein the means for removing the surplus film comprises a wire surrounding the means for holding in position the container and means for heating the wire so that it can cut through the film and separate the surplus film from the remainder of the film.

14. Apparatus according to claim 13, wherein the wire is disposed to be spaced below the free edge of the rim of the container when held in position by the first-mentioned means.

1 5. Apparatus according to claim 9 or any of claims 10 to 14 is appendant thereto, wherein the inner side surface of the recess in the holder is substantially vertical.

1 6. Apparatus according to claim 9 or any of claims 9 to 1 5 as appendant thereto, wherein the holder comprises metal sheeting providing the inner side surface of the holder.

1 7. Apparatus according to claim 16 as appendant to claim 11, wherein the lip is provided by the metal sheeting.

1 8. Apparatus according to any of claims 8 to 17, wherein the second-mentioned means comprise ducts opening onto a platform arranged to surround and be disposed below the rim of the container to be covered with film, the ducts being for withdrawing air from beneath the overlapping portion of the film to bring the overlapping portion down towards the platform.

19. A method according to any of claims 1 to 7, when carried out using apparatus according to claim 9 or any of claims 10 to 18 & as appendant thereto, wherein the lower portion of the container is a loose fit in the holder.

20. Apparatus for covering open-topped containers of the type specified herein with film, substantially as described herein with reference to the accompanying drawings.