GB2295807A

GB2295807A - Applying tear strip to pack

Info

Publication number: GB2295807A
Application number: GB9523574A
Authority: GB
Inventors: Pietro Segota
Original assignee: WR Grace and Co Conn; WR Grace and Co
Current assignee: WR Grace and Co Conn; WR Grace and Co
Priority date: 1994-12-07
Filing date: 1995-11-17
Publication date: 1996-06-12
Anticipated expiration: 2015-11-17
Also published as: GB2295807B; GB9523574D0

Abstract

A heat shrunk pack 3 is advanced (along a belt conveyor 5) past an adhesive applicator 9 which applies a strip 21 of hot melt adhesive to the top of the pack. Then the pack 3 with its adhesive strip is advanced (by a belt conveyor 11) past a tear strip application station 13 where a tear strip or label 23 is applied over the adhesive, with a free end 24 of the tear strip or label non-adhered and forming a pull-tag to be grasped and removed for ripping open the pack. The adhesive 21 extends along and close to a seal 34 of the pack, and has bond strengths to both the tear strips 23 and the pack greater than the tear strength of the pack. <IMAGE>

Description

METHOD OF PROVIDING AN EASY OPEN PACK.

AND PACK MADE THEREBY The present invention relates to a method of providing a film package with an easy open feature to facilitate tearing open of the pack by the consumer. The invention is particularly applicable to packages which involve the application of a shrinkable plastic film around a product, with shrinking of the applied film as one of the steps in the manufacture of the package.

In the past there have been various proposals for producing plastic film packs, for example by loading a product into a pre-formed bag or pouch of plastic film, and then subsequently sealing the bag or pouch by welding or clipping, applying a plastic film round a succession of products in a form-fill-seal (either vertical or horizontal) process with subsequent heat sealing of the individual packs, inserting products into a centre-folded film between the superposed sides thereof and sealing, and over-wrapping a product with a shrinkable film and subsequently shrinking it. It is also known to subject the closed pack to shrinking - for example in a hot air shrink tunnel -to tidy the packs.

It is also known to provide packs with an easy-open feature which presents a predetermined area of weakness (e.g. by scoring) or of unsealed contacting films, to enable the consumer to initiate a tear or delamination of the pack by pulling the pack material, possibly with the provision of an easy-open location by application of a stronger film portion as a tear tab or label, to initiate opening. Particularly in the case of the additional tear tab, the conventional method has the important disadvantage that the overall tidiness of the pack after shrinkage (which is after all one of the targets of a shrink tidy operation) is marred by the uneven reaction of the packaging film and the stronger tear tab film to the shrinking heat.

Easy open features have, in the past, been used where there has been no shrink or only a small degree of shrink carried out to form the pack, because the difference in shrink properties of the basic packaging film and the tear strip applied thereto would lead to a loose package if more pronounced shrink is carried out. Furthermore, the tear strip feature is only practical when the basic packaging film is of relatively low tear strength, otherwise the conventional tear strip system would be unable to initiate opening of the pack.

It is an object of the present invention to provide a method of creating an easy open feature on a shrunk pack regardless of the strength of the pack, and regardless of the degree of shrink which is effected to form the pack.

In accordance with one aspect of the present invention there is provided a method of providing a pack, comprising taking an envelope of a heat-shrinkable film enclosing a product, applying shrinking heat to cause the packaging film to apply itself more intimately to the product, and applying thereto a tear strip having a tear strength greater than that of the envelope, the application of the tear strip to the envelope being effected by way of an adhesive having bond strengths to both the tear strip and the envelope which are greater than the tear strength of the envelope, and the adhesive being positioned close to and along a seal of the envelope.

A second aspect of the present invention provides apparatus for forming a pack comprising means for advancing a pack along a path, an adhesive application station along said path for applying a hot melt adhesive to the surface of the packs being passed therealong, and a tear strip application station for applying tear strip material to a quantity of hot melt adhesive on a pack passing the tear strip application station.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which: Figure 1 - is a side elevational view of a machine for applying tear strips to comple: d packs; Figure 2a - is a view showing a pack prior to application of the tear strip thereto and prior to shrink tidying of the enveloping film material; Figure 2b - is a view of the pack of Figure 2a after shrinking; Figure 2c - is a view of the shrunk pack after the application of an adhesive thereto; Figure 2d - is a further view of the pack after application of a tear strip to the adhesive; Figure 3 - is a top plan view of an alternative embodiment of the finished pack; Figure 4 - is a perspective view of a pack during opening by the consumer; and Figure 5 - is a top plan view of a preferred embodiment of the finished pack.

Referring now to the drawings, Figure 1 shows the outlet of a shrink tunnel 1 feeding shrunk packs 3 onto a belt conveyor 5 past a first photosensing unit 7 towards an applicator 9 for a hot melt adhesive.

After the application of the hot melt adhesive the packs 3 pass off the end of the belt conveyor 5 and onto a succeeding belt conveyor 11 which advances the packs from the adhesive application step to an application station 13 for a tear strip or label to be applied to the still soft adhesive.

Figure 2a shows one of the packs 3 as comprising a flat product 15, in this case a stack of slices of meat, within an envelope 17 comprising an upper layer 17a and a lower layer 17b of heat shrinkable film material sealed around the perimeter of the product 15 along a continuous seal region 19. Thus far the pack of Figure 2a is in the condition in which it enters the shrink tunnel 1 whose exit is shown in Figure 1.

In Figure 2b the envelope 17 has been tightly shrunk into contact with the surface of the product (stack of slices) 15 and would be as illustrated exiting the shrink tunnel 1 in Figure 1.

In Figure 2c the pack is illustrated in the form in which it has just passed onto the second belt conveyor 11 from the first belt conveyor 5, after the application of a strip of hot melt adhesive 21 to its upper surface.

Finally, to arrive at the Figure 2d configuration, a tear strip 23 having a tensile strength greater than that of the film which forms the envelope 17 has been applied over the adhesive strip 21. The tear strip 23 may, if required, comprise a printed label of strong film.

When the hot melt adhesive of the strip 21 cools, it must have bond strengths to the tear strip 23 and to the envelope 17 which are at least as great as the tear strength of the film forming the envelope 17. Thus when the tear strip 23 is pulled by its nonadhered end 24 (Figure 2d), upwardly away from the upper surface of the envelope 17 lying on the product 15, the adhesive strip 21 will peel away from the remainder of the envelope 17 and will cause the envelope to open by local rupture.

The strip 21 of the hot melt adhesive may be localised so that it defines a hole in the film layer 17a just large enough for the consumer to insert a finger or a suitable tool through the hole in the envelope 17 in order to initiate further rupture of the shrunk envelope; alternatively the area of the adhesive strip 21 may be more extensive so as to allow a more substantial opening to be formed as the strip 23 is torn away from the envelope 17.

Typically the hot-melt adhesive strip 21 is positioned along and close to a seal of the package; this is particularly suitable when the product is of soft consistency, as the option of providing a small hole to be prised open by the consumer with a finger or a tool can result in damage to the product. In such a case the application of the hotmelt adhesive along a seal to induce opening of the envelope by rupture along the seal itself, would minimise the risk of damage to the product during withdrawal from the open pack.

In a preferred embodiment of the present invention, the envelope comprises a longitudinal seal, and the hot-melt adhesive strip 21 and the tear strip 23 are positioned along said longitudinal seal.

Returning now to Figure 1, there can be seen a supply roll 25 of continuous strip material which is threaded up over guide pulleys 27, 29 and 31, and hence onto applicator pulleys 33 which roll the strip material from the supply roll 25 flat onto the hot melt adhesive strip 21 (Figures 2c and 2d), leaving a non-adhered end 24 projecting beyond the end of the strip 21 of hot melt adhesive.

Typically the continuous strip on supply roll 25 is a carrier sheet with discrete labels 23 of strong film thereon to be applied one at a time to the packs.

The tear strip may in itself be laminated, but it is then important that the strength of bonding of the layers to form that laminate should be at least as great as the bond strength between the laminate and the hot melt adhesive, in order to avoid delamination of the tear strip 23 upon tearing rather than removal of the tear strip 23 and adhesive 21 with the contacted region of the envelope 17 from the remainder of the envelope 17.

Although not essential to the understanding of the present invention, there are also shown in Figure 1 drive motors 37 and 39 under the main table 41 of the apparatus for driving the two belt conveyors 5 and 11; also supports for the various elements of the hot melt adhesive applicator 9 and the tear strip application station 13 are illustrated.

The position of the first photocell 7 adjacent the first conveyor belt 5 is such that it detects the configuration of the series of packs 3 on the belt conveyor 5 when one of the packs is under the adhesive applicator 9 so that the applicator can then be activated to dispense a strip of adhesive through its nozzle.

There is a second photocell 43 at the tear strip application station 13, to actuate indexing of the various guide rollers 27, 29 and 31, and the supply roll 25 of tear strip material, to apply the tear strip 23 to the already formed strip 21 of adhesive on the pack detected by the photocell 43.

The film material for the envelope 17 may be a heat shrinkable display film such as disclosed in GB-A-2115348 and GB-A-2135240. It may, equally, exhibit oxygen barrier properties such as is described in EP-A-0217596.

As indicated at the outset above, the envelope 17 may of course be a bag which has been heat sealed, and typical materials used for such bags are the films disclosed in (EP-A-0627465).

The hot melt applicator 9 may be a manually operated pneumatic model TR 60.3 available from Reka GmbH & Co. KG of Germany or an electrically controlled pneumatic HM 250 applicator available from HOT MACHINES of Turin, Italy.

The tear strip application station 13 may use a commercially available label dispenser to apply the tear strip material to the adhesive 21 on the pack 3, and may for example be a model Collamat 6010/20 available from Guhl & Scheibler AG of AESCH (Switzerland).

The hot melt adhesive used with the method of the present invention must provide high adhesion to both the outer layer of the envelope 17 and the underneath surface of the tear strip material 23.

The tear strip material should also have a relatively low modulus of elasticity so as to be able to adhere to the surface of a shrunk pack even when that surface is somewhat uneven due to the shrinkage. It should have a high tensile strength so that it does not tear during the step of tearing open the pack, and equally it is preferable for there to be little or no elongation under tension, thereby avoiding stretching of the film and ensuring that the effort applied by the consumer is utilised to rupture the envelope rather than to stretch the tear strip.

Typical adhesives which can be used are ethylene vinyl acetate - hot melt adhesives, and one particularly preferred forms are those known under the designations S/84 and S/86, available from Elettrograf s.a.s. of Milan, Italy and VR 5001 available from Barbero Pietro of Grugliasco, Italy. Other food-approved adhesive materials with similar properties or a mixture of different such food-approved materials may be used, if necessary, in order to ensure good adhesion to the outer layer of the envelope 17 if such high adhesion cannot be obtained with an EVA resin.

The pack made by the method of the present invention is particularly suitable for use with edible products, such as cheese or stacked slices of meat.

The tear strip may be applied to the pack 3 by means of a single adhesive strip, or there may be two or more parallel strips of the hot melt adhesive, each holding the same tear strip 23.

A pack of the type having two parallel strips 21a and 21b is shown in plan view in Figure 3, and an alternative type, with one strip 21 as described above, is shown in Figure 4 as the unadhered end 24 of the tear strip 23 is being pulled away to initiate tearing of the envelope.

Where several adhesive strips are used, the rate of delivery of the hot melt from the applicator 9 is kept constant so that a uniform quantity of resin is distributed along each adhesive strip such as 21a and 21b in Fig.3. Where there is only one strip 21 of the adhesive, the rate of delivery of resin from the applicator 9 may be varied so as to apply a non-uniform quantity of resin along the strip as shown in Fig. 4. In this way the label will be adhered to the hot melt resin in such a way that there is a greater amount of hot melt adhesive at the end nearest to the grasping end 24 of the label, where the tear in the envelope 17 is to be initiated, than towards the other end where the tear would be well established, during opening by the consumer.

The hot melt strip 21 can be applied along part, or the whole, of the length of the longitudinal seal 34 of the pack 3, depending on the dimensions of the product and thus of the pack, and on the dimensions of the opening which is to be formed.

The quantity of hot melt adhesive applied to form the strip 21 may be as low as 0.3 grams per package, for a very small pack, but 5 or more grams may be use if the dimensions of the package and the size of the required opening dictate.

The photocells 7 and 43 can be used not only to initiate the application of the hot melt adhesive and of the tear strip, but also to control the positioning of the adhesive and tear strip. Suitable circuitry to allow a change in position for different pack types or sizes may be incorporated in the machine, or alternatively the positioning of the photocell itself can be adjustable to change the location of the adhesive 21 and tear strip 23.

Where, as in the case of a horizontal form-fill-seal pack or a vertical form-fillseal pack, the pack has a continuous seam the easy-open tear strip is applied close to this longitudinal seal so as to locate it at an area of potential weakness of the envelope 17 where opening is going to be most effective.

Equally, where the pack comprises some other inherent line of weakness, the hot melt adhesive strip 21 should be applied along the direction of the line of weakness, and possibly partially overlapping it, in order to facilitate the initial opening.

Where the tear strip 23 is a label for the pack, it is important that that label should adhere firmly to at least part of the hot melt strip 21, if not to the whole strip, and must have at least one free end 24 of a sufficient size to enable it to be gripped between the consumer's fingers in order to apply the tearing force. Suitable materials for the tear strip 23 may be co-polyesters, or oriented polypropylene heat-set (OPP-HS) preferably with a sealant-coated side. Alternatively the tear strip 23 may be on plasticised paper or cardboard, where the coating material has a sufficient bond adhesion to the resin used for the body of the tear strip, and imparts the necessary strength to the substrate.

In a preferred embodiment the tear strip 23 is positioned on the package so that the free end 24 protrudes from the edge of the package surface to ease gripping as indicated in Figure 5. Also preferably the tear strip 23 will bear an indication of the direction in which it should be torn in order to open the package. As shown in Figure 5, this indication can be in the form of an illustration of a partially opened zip fastener.

Where the labels or other tear strips are supplied on a continuous carrier tape as disclosed above, the individual labels may be stuck on a strip of silicone release paper allowing them to be dispensed one at a time for application to the package.

Preferably the labels are stuck on the silicone release paper by means of two lateral strips of pressure sensitive adhesive leaving a central adhesive-free strip for contact with the hot melt adhesive strip 21.

The method in accordance with the invention may, if desired, provide for the application of the hot melt adhesive first onto a part of the label so that that adhesive/label combination can then be applied to the shrunk pack 3 in a single operation.

If desired the shrunk pack to which the method of the present invention is applied may be one which has a vacuum applied to its interior, or may be one having a modified atmosphere (for example of an inert gas or of carbon dioxide), within the envelope 17.

Claims

1. A method of providing a pack, comprising packaging a product in an envelope of a heat shrinkable film, applying shrinking heat to the envelope and applying thereto a tear strip having a tear strength greater than that of the envelope, the application of the tear strip to the envelope being effected by way of an adhesive having bond strengths to both the tear strip and the envelope which are greater than the tear strength of the envelope, and the adhesive being positioned close to and along a seal of the envelope.

2. A method according to claim 1, wherein the adhesive is applied to the pack and then the tear strip is applied to said adhesive to secure the tear strip to the pack.

3. A method according to either of the preceding claims, wherein the adhesive is a hot melt adhesive dispensed hot onto the film to be sealed.

4. A method according to either of claims 1 and 2, wherein the adhesive is a hot melt adhesive applied to the envelope and subsequently heated to melting point to activate it.

5. A method according to either of claims 1 and 2 wherein the adhesive is applied to the tear strip and the tear strip/adhesive combination is then applied to the envelope of the package.

6. A method according to any one of the preceding claims wherein said envelope has a longitudinal seal and the adhesive is applied along said longitudinal seal.

7. A method according to any one of the preceding claims, wherein the tear strip is a printed label.

8. A method of forming a pack, substantially as hereinbefore described as reference to the accompanying drawings.

9. Apparatus for forming a pack comprising means for advancing a pack along a path, an adhesive application station along said path for applying a hot melt adhesive to the surface of the packs being passed therealong, and a tear strip application station for applying tear strip material to a quantity of hot melt adhesive on a pack passing the tear strip application station.

10. Apparatus according to claim 9 and including a shrink tunnel upstream of said adhesive applicator for shrinking the envelope of a pack before presentation at said adhesive applicator.

11. Apparatus for forming packs, substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.

12. A pack formed by the method of any one of claims 1 to 8, or by the apparatus of any one of claims 9 to 11.