NZ272818A - Forming plastics bags with peelable seal line adjacent reclosable elements in bag mouth - Google Patents

Description

Patents Form # 5 27 2 8 1 8 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION TITLE: A Method of forming a Bag APPLICATION#: 272818 FILING DATE: 18 November 1995 We,: Minigrip Flexible Packaging Limited Address: 27 Ross Reid Place, East Tamaki, Auckland, New Zealand Nationality: New Zealand 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: .JWP REG 15.11 ?408'J6H£ft~ 39-'";par L~ FEE CODE - 1050 272818 This invention relates to a method of forming a bag and in particular has been devised for forming bags to carry consumer items, for example, food items but other uses of the bag are envisaged.

Bags which hold, for example, cheese and also other items are usually gas flushed with, for example, carbon dioxide and nitrogen to enhance the storage qualities of the cheese. For this to be effective the bag when sealed must provide a hermetic seal. This requires seals to be formed and it is desirable that such seal be sufficiently robust to cope with forces on the seal during normal storage, transportation and sale but be 10 sufficiently rupturable to enable relatively easy access to the product by the consumer after purchase.

A type of seal known as a peelable seal has been developed which enables parts of the package to be readily separated by manual pressure across the seal. The peelable seal 15 gives hermetic barrier properties but enables relatively easy ^ntry.

Such peelable seals may be associated also with connectors which are elongated recloseable connectors comprising two elongated elements, one being a bulbous rib and the other being a narrow mouthed channel so that the connectors can be snapped 20 into and cm' of engagement to close and open the bag.

Such bags are often formed and filled by thermoforming processes, in particular top and bottom web vacuum systems. Such constructions are however disadvantageous in that sealing of the bag, in particular across the recloseable 8802QCSL.4 98/CW/jq laments at the ends thereof intellectual property office of n.z. 2 e apr 1998 RECFIV/FD 27 2 818 where the recloseable elements meet the edges of the bag, the required hermetic seal is often not achieved principally because of the number of layers that must be sealed. This is particularly so where the peelable seal is inward of the recloseable elements. The peelable seal can be put outside the recloseable elements which reduces the risk 5 of leakages but to date such constructions can only be applied in apparatus comprising top and bottom web vacuum systems. This is disadvantageous.

It is therefore an object of the present invention to provide a method of forming a bag and/or a bag which will obviate or minimise the foregoing disadvantages in a simple IO yet effective manner or which will at least provide the public with a useful choice Accordingly in one aspect the invention consists in a method of forming a bag comprising the steps of forming plastics material to provide a bag having front and back faces and a mouth, providing adjacent said mouth part of an elongated 15 recloseable element on each face to enable said mouth to be opened and closed and providing, independent of said recloseable elements, at least one seal line across said bag, said seal being sufficiently strong to resist opening of said seal during normal usage of the bag but being tearable by manual pressure across the seal, each bag being formed either as one of a string of linked bags for later filling or on vertical fill 20 apparatus at the time of filling.

Preferably said bag is formed of material to allow the peelable seal to be provided by the application of heat thereto. intellectual property office of n.z. 2 9 apr 1998 8 802QCSL.4 98/CW/'jq received 272818 Preferably a peelable seal is provided adjacent each edge but the peelable seal near the mouth is formed to a lower tear strength.

Preferably the peelable seal at the mouth is positioned outside the recloseable elements, or inside the recloseable elements, or a peelable seal is provided in both positions.

Alternatively the peelable seal is provided by tapes of suitable material applied to or 10 adhered to the desired position of the bag face.

In a further aspect the invention consists in a bag when formed by the method of any of the preceding paragraphs.

In a still farther aspect the invention consists in a bag containing produce when the bag has been formed by a method according to any one of the preceding paragraphs.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest 20 themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting. 8802QCSL.498/CW/jq intellectual property office of n.z. 2 9 apr 1998 received -5- ^ 2818 One preferred form of the invention will now be described with reference to the accompanying drawings in which, Figure 1 is a diagrammatic simplified perspective view of a string of preformed 5 bags forming part of one embodiment of the invention, Figure 2 is a diagrammatic view of an enlargement of part of figure 1, Figure 3 is a diagrammatic view of an alternative method for forming the 10 invention, Figure 4 is a diagrammatic cross sectional view of one form of bag, an alternative form of bag according to the invention, Figure 5 is a view as in figure 4 of a still further alternative bag.

Referring to the drawings, a method of forming a bag is provided as follows.

The product of the invention comprises a bag of plastics material which comprises 20 front and rear faces and is which sealed around three edges to provide a mouth. Into the mouth is positioned recloseable elements which comprise an elongated buibous rib on one inner face of the bag and a narrow mouthed receiving channel on the other face of the bag. The reclose elements may be provided as tapes or strips and methods of positioning these elements into bags of plastics material are 8802QCSL.498/CW/jq in the industry. intellectual property office of n.z. 13 apr 1998 received :7 2 81 8 The reclose elements could also be formed integrally into the bag material or provided just as the element itself. Either inwardly of the recloseable elements or outwardly of the recloseable elements or both is provided a peelable seal of a type formed by heat sealing and which is commonly known by the term peel seal. This is a seal that is 5 peelable by the application of manual pressure across the seal but the seal is sufficiently robust to provide a hermetic seal and to resist the normal stresses on the seal during normal transportation, storage, and sale of the items.

In one form of the invention a series of bags 1 comprising individual bags 2 linked 10 together, for example, at the mouth end is provided. Recloseable elements 3 as described above are provided adjacent the mouth. It will be apparent that the bags can be inverted so that the bags are provided upside down and filled through the bottom end for later closure and the changes necessary to the following description would be clear to persons skilled in the art. The bags may be formed of material which allow 15 the peelable seal to be formed, for example, co-extrusions of polybutylene and ionomer. After filling at position 4 the bags are heat sealed at 5 or 6 or both to provide the peelable seals above described. The peelable seal is indicated in the drawings by a row of small "x's". Where the bag is formed of the polybutylene and ionomer material the side edges and foot can also be formed by peelable seals, for 20 example, at 7 and 8 and in such a construction it is desirable that the seals at 7, 8 and 9 are formed somewhat stronger. This can be achieved by sealing at a higher temperature, for example, 170°C compared to sealing at about 135°C at 5 or 6. 8802QCSL.498/CW/jq iniellectual property office of n.z. 2 9 apr 1998 received 2818 Sealing at 135°C will give a strength test of about 10 Newtons per 25mm compared to the strength at 170°C of about 40 Newtons per 25mm.

The arrangement shown in figures 1 and 2 is performed on apparatus that enables the 5 string of bags shown in figure 1 which have been preformed to be filled and sealed. The same effect can be achieved by the use of vertical fill lines where incoming plastics material 10 is folded downwardly and around the filling pipe 11. The peelable seals can be formed at 12 and 13 and appropriate cross seals formed to complete the bag. Again the material can be the polybutylene and surlyn co-extrusion 10 or alternatively strips or tapes of that material can be adhered, for example, to a polyethylene or other material bag to enable the peelable seal to be formed. Where strips or tapes are used standard technology is used to form any required seals at the sides and foot of the bag.

Thus a bag is formed which has a front and back face sealed on the side edges and sealed or folded at the bottom. Across the mouth of the bag is provided recloseable elements and on one or both side of the recloseable elements is provided a peelable seal.

An alternative embodiment is shown in figure 4 where the bag 2 has a peelable seal 15 therein and within that is provided a folded closure part which carries the recloseable elements indicated at 16. The bag and closure part 17 are sealed together at 18. The construction of figure 5 is similar with the peelable seal at 15 and a closure part 17 8802QCSL.498/CW/jq 7281 carrying recloseable element 16 save that the seals formed at 18 are provided with the closure part 17 adhered to the outside of the bag part 2. This enables the peelable seal 15 and the sealing of the bag 2 to the closure part 17 to be performed by a single sealing operation.

Thus it can be seen that a method of forming a bag and or a bag are provided which has the advantage that the filling and sealing can be performed on apparatus to fill and seal linked bags or in vertical fill apparatus. The use of such techniques leads to a reduction in the rate of bags formed with inadequate hermetic seals particularly in the region of the recloseable elements. intellectual property office of n.z. 2 9 apr 1398 received 8802QCSL.498/CW/jq c - 81

Claims (9)

WHAT WE CLAIM IS:

1. A method of forming a bag comprising the steps of forming plastics material to provide a bag having front and back faces and a mouth, providing adjacent said 5 mouth part of an elongated recloseable element on each face to enable said mouth to be opened and closed and providing, independent of said recloseable elements, at least one seal line across said bag, said seal being sufficiently strong to resist opening of said seal during normal usage of the bag but being tearable by manual pressure across the seal, each bag being formed either as one of a string of linked 10 bags for later filling or on vertical fill apparatus at the time of filling.

2. A method as claimed in claim 1 wherein said bag is formed of material to allow the peelable seal to be provided by the application of heat thereto.

3. A method as claimed in either claim 1 or claim 2 wherein a peelable seal is provided adjacent each edge but the peelable seal near the mouth is formed to a 15 lower tear strength.

4. A method as claimed in any one of the preceding claims where the peelable seal at the mouth is positioned outside the recloseable elements, or inside the recloseable elements, or a peelable seal is provided in both positions.

5. A method as claimed in any one of claims 1 to 3 wherein the peelable seal is 20 provided by tapes of suitable material applied to or adhered to the desired position of the bag face. 8802QCSL.49 8/CW/jq intelleciual property office of n.z. 2 9 apr 1998 ! receivfn [

6. A method of forming a bag substantially as herein described with reference to the accompanying drawings.

7. A bag when formed by the method of any one of the preceding claims.

8. A bag substantially as herein described with reference to the accompanying drawings.

9. A bag containing produce when the bag has been formed by a method accordingly to any one of claims 1 to 6. !0. A bag containing produce substantially as herein described with reference to the accompanying drawings. JAMES W PIPER & CO Attorneys for the Applicant Minigrip Flexible Packaging Limited INTELLECTUAL PROPERTY OFFICE OF N.Z. 2 9 apr 1998 received 8802QCSL.498/CW/jq