AU728260B2 - A bag including a closure device made of complementary strips and a closure device therefor - Google Patents

Abstract

The invention concerns a plastic bag provided with a detachable closing device (1) capable of being closed tight, consisting of two sections (2), each section (2) being made up of a seat (3) provided, on one face, with a closing element (4), co-operating with that of the other section (2) and, on the opposite face, with at least a raised band (5) for fixing the seat (3) on one surface of the bag (10), by melting and pressing the fixing band (5) on said surface (10), characterised in that the fixing band (5) has a transverse cross-section the length of which increases from the free end towards the seat (3).

Description

A BAG INCLUDING A CLOSURE DEVICE MADE OF COMPLEMENTARY STRIPS, AND A CLOSURE DEVICE THEREFOR The present invention lies in the field of bags that include closure devices of plastics material. More particularly, the invention relates to closure devices fixed to a bag wall by heat sealing.

Numerous bags have already been proposed that include a closure device made up of two strips. In such a device, each strip comprises a base that is to be fixed on the wall of the bag and at least one closure element projecting from said base. Each strip is fixed on the wall of the bag in such a manner that each closure element of a strip faces a closure element of the other strip that is complementary thereto.

In order to facilitate heat sealing the base onto the wall, devices are known in which the base is provided with ribs.

Thus, patent FR 2 613 326 describes separable closure strips provided with a plurality of meltable ribs of rectangular cross-section and of sufficient mass to provide a molten bonding layer between the strip and the wall of the bag. Nevertheless, with ribs of that type, heat sealing is sometimes difficult, thereby reducing fixing effectiveness and causing the strip to be deformed, which impedes proper co-operation between the closure elements.

The object of the invention is to provide an improvement to ribs for heat sealing closure strips onto bag walls.

The invention is a plastics material bag provided with a separable and reclosable closure device made up of two strips, each strip being constituted by a base provided on one face with a closure element suitable for co-operating with the closure element of the other strip, and on its opposite face with at least one fixing rib for fixing the base onto a wall of a bag by melting and compressing the fixing rib against said wall, the bag 2 wherein the cross-section of the fixing rib is of width that increases going away from its free end towards the base.

After being melted and compressed, the tip of the rib is flattened. The width of the zone of contact between the rib and the wall of the bag thus varies as a function of the quality of heat sealing.

This rib shape presents the advantage of being tolerant to variations in the pressure applied for sealing the strip to the film of the bag. If the sealing pressure is small, then the force on the tip is nevertheless sufficient to give rise to a good bond.

However, the greater the pressure, the greater the area r. over which bonding takes place, thereby giving rise to a backing pressure that increases accordingly. This makes it possible to avoid passing right through the thickness of the film that constitutes the wall of the bag.

In an advantageous embodiment of the invention, a e. pigment is included in the bulk of the plastics material, at least in the ribs.

Thus, if the wall of the bag is translucent or transparent, a stripe appears that is colored to a S: greater or lesser extent where the strips are fixed on.

The width and the intensity of the color constituting said stripe are then functions of the area of the region of the rib that has melted together with the support.

Thus, the quality of the fixing can be monitored optically after heat sealing.

S" In addition, asymmetrical coloring of the ribs on 4 either side of the closure elements makes it possible for the person handling the components to identify the direction in which the strip ought to be placed relative to the opening of the bag. The closure element must have great resistance against the internal pressure of the bag contents. However, the same element must also be easy for a user to open, and must therefore present smaller R 1,esistance to external pressure. To satisfy these requirements, the closure elements are asymmetrical and the asymmetry must be capable of being identified during the step of heat sealing the strip onto the wall of the bag.

Bags of the invention are described below with the help of a non-limiting example and with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a closure device of the invention, with its closure elements spaced apart, prior to their ribs being heat sealed onto the walls of a bag.

Figure 2 is a perspective view of a closure device of the invention with its closure elements mutually engaged, after their ribs have been heat sealed onto the walls of a bag.

""Figures 3a, 3b, 3c are a series of cross-sections through a triangular rib to show the advantage of bulk pigmentation.

Figure 4 is a diagrammatic view of a bag closure device of the invention, in a die between two guides of a certain type.

Figure 5 is a diagrammatic view of a bag closure S device of the invention between two guides of another type.

The following detailed description describes a particular but non-limiting embodiment of bags and of a closure device of the invention.

Figure 1 shows a closure device 1 made of plastics material and constituted by two strips 2. Each strip 2 3. is constituted by a base 3. Each base 3 is a flat member 0 of rectangular section.

Each base has an internal main face and an-external main face. The internal faces of the two strips face each other when the closure device 1 is operationally in position on the wall of a bag The internal face is provided with at least one closure element 4. The external face is provided with at least one fixing rib 5 for fixing the strip 2 onto a wall of the bag Each closure element 4 extends parallel to the edge of the base 3.

The closure elements 4 of the strips 2 are suitable for co-operating with each other to hold the two strips 2 together. These closure elements can be engaged one in the other and they can be separated from each other in reversible manner.

In Figures 1 and 2, one of the closure elements 4 is represented by an arrow which symbolizes a male element.

The other closure element 4 is represented by an open cylinder, which symbolizes a female element. These elements may be of any known shape that is suitable for performing the closure function by the male element engaging in the female element. The closure is preferably hermetically sealed.

Each fixing rib 5 is parallel to the edge of the base 3.

Each fixing rib 5 has a cross-section of width that increases going from a free edge towards the base 3. The section is preferably triangular. The triangle defined in this way is an isosceles triangle or an equilateral triangle. If it is an isosceles triangle, neither of the two same-length sides coincides with the base 3.

Each rib 5 can be disposed on the base 3 in various ways.

For example and preferably, if there are two ribs per strip 2, each of them is situated close to a respective one of the longitudinal edges 8 of the base 3, on the face of the base 3 opposite from its face carrying the closure element 4.

However, this embodiment is not limiting and it is also possible to envisage only one rib 5 per strip 2, or indeed three, or four, or even more ribs 5 per strip 2.

Under such circumstances, two of the ribs will be situated, for example, close to respective longitudinal edges 8 of the base 3.

The quantity of material in the ribs 5 that is subjected to compression during heat sealing can be variable. The more effective the operations of melting and compressing the ribs 5, the wider the area of the line of heat sealing 6 (Figure Thus, the triangular shape of the ribs 5 makes it possible to inspect the quality of the resulting heat sealing directly by eye.

In an advantageous but non-limiting variant of the invention, the plastics material of the closure device 1, and in particular the material of the ribs 5, can be tinted in its bulk by means of pigments. This improvement makes it possible to observe the width 1 of the heat sealing surface 6 by transparency through the wall of the bag The pigmentation can be obtained using any type of pigment. The concentration of the pigment can be less than 1% by weight.

Furthermore, the quantity of pigment accumulated at the surface of the line of heat sealing 6 increases with increasing depth h over which the tip 7 of the rib 5 is compressed (Figure Thus, the quality of the heat sealing can be inspected optically, not only by the width 1 of the line of heat sealing 6, but also by the intensity of the color of the heat sealing 6.

To make it easier to identify the asymmetry of strips 2 in terms of their resistance to internal pressure and to a bag-opening force, the ribs 5 can be tinted in different manner on either side of the closure elements 4.

By way of non-limiting illustration, each strip 2 may have the following dimensions: width of the base 3, between its two longitudinal edges 8, about 8 mm; thickness E level with the closure elements 4 of the two strips 2 when assembled together with said closure elements 4 being engaged one in the other, about 2 mm; width of the base of each rib 5, where it meets the base 3, about 1 mm to 2 mm; and distance between the longitudinal edge 8 of the base 3 and the edge of the rib 5 closest to said longitudinal edge 8, about 0 to 1 mm.

The strip 2 can be made with various types of polymer. In particular, these polymers may be a polyolefin or a mixture of polyolefins.

The base 3 and the closure elements can be made of any polymer having mechanical characteristics enabling it to close effectively. By way of example, it can be a polyolefin of low, medium, or high density.

The ribs 5 can be made of any polymer having good heat sealing characteristics and can be coextruded with the material of the base 3. By way of example, the polymer can be a polyolefin such as linear polyolefins, EVA, metallocene, etc.

In particular, and preferably, the material constituting the ribs 5 can be different from the material constituting the closure elements 4 and the base 3. Most preferably, the material constituting the ribs has a melting point that is lower than that of the material constituting the closure elements 4 and the base 3.

To facilitate insertion and passage of the strips 2 through various extruder dies 20 or other subassemblies of machines for forming or assembling bags, it is preferable for the ribs 5 to be of a shape and position on the base 3 that enable the pair of strips 2 of the closure device 1 to deform so as to occupy a smaller amount of space between the guides 21 of such dies (Figure More precisely, the sum of the width L of the external faces 7 of the ribs 5 is less than or approximately equal to the thickness E of the set of two strips 2 in register with the closure element 4 when said 7 elements 4 are engaged one within the other. In this manner, it is possible for the strips 2 to occupy a deformed state in which the surface formed by the external face 9 of the base 3 between the ribs 5 and the internal faces 7' of the ribs 5 is roughly plane.

In other types of die 30 or in other subassemblies of machines for forming or assembling bags, the ribs make it possible to position the strips 2 accurately in said dies 30 between guide elements 31 which are in the form of spring blades or wheels (Figure For this purpose, the width of the base 3 between the bases of the inside faces 7' of the ribs 5 is approximately complementary to the width of the guide elements 31.

Claims (21)

1. A plastics material bag provided with a separable and reclosable closure device made up of two strips, each strip being constituted by a base provided on one face with a closure element suitable for co-operating with the closure element of the other strip, and on its opposite face with at least one fixing rib for fixing the base onto a wall of a bag by melting and compressing the fixing rib against said wall, wherein the cross-section of the fixing rib is of width that increases going away from its free end towards the base.

2. A bag according to claim 1, wherein the fixing rib has a cross-section that is generally triangular in shape.

3. A bag according to claim 2, wherein the triangle defined by the cross- 0. section of the fixing rib is an isosceles triangle, with neither of its two same-length 0 sides coinciding with the base.

4. A bag according to claim 2, wherein the triangle defined by the cross- section of the fixing rib is an equilateral triangle.

5. A bag according to any one of the preceding claims, wherein each strip has two ribs, each situated in the vicinity of one of the longitudinal edges of the base, and on the face of the base that is opposite from its face carrying the closure element.

6. A bag according to any one of claims 1 to 4, wherein each strip has four fixing ribs situated on the face of the base opposite from its face carrying the closure element, two of the ribs being situated close to a respective longitudinal edge of the base.

7. A bag according to any one of the preceding claims, wherein each fixing rib tinted in its bulk. 9

8. A bag according to any one of the preceding claims, wherein the ribs are tinted in different manner on either side of the closure elements.

9. A bag according to any one of the preceding claims, wherein the ribs are of shapes and positions on the base enabling the assembly including the two strips of the closure device to deform so as to occupy little space and facilitate insertion of said strips into the dies of extruders, and to facilitate passage therethrough.

A bag according to any one of the preceding claims, wherein the sum of the widths of the external faces of the ribs is less than or approximately equal to the thickness of the two assembled-together strips in register with the closure elements when said elements are engaged one in the other.

11. A bag according to any one of the preceding claims, wherein the ribs 15 enable the strips to be held between guide elements. 0o S .i e'

12. A closure device for use with a bag according to any one of the preceding claims, the closure device including two strips, each strip including a base provided on one face with a closure element suitable for co-operating with the closure element of the other strip, and on its opposite face with at least one fixing rib for fixing the base onto the wall of a bag by melting and compressing the fixing S rib against said wall, wherein the cross-section of the fixing rib is of width that increases going away from its free end towards the base. S:

13. A closure device according to claim 12, wherein the fixing rib has a cross- section that is generally triangular in shape.

14. A closure device according to claim 12 or 13, wherein each strip has two ribs, each situated in the vicinity of one of the longitudinal edges of the base, and on the face of the base that is opposite from its face carrying the closure element.

C:\WINWORD\TONIA'B F'SPECISP82187.DOC A closure device according to any one of claims 12 to 14, wherein each fixing rib is tinted in its bulk.

16. A closure device according to any one of claims 12 to 15, wherein the ribs are tinted in different manner on either side of the closure elements.

17. A closure device according to any one of claims 12 to 16, wherein the ribs are of shapes and positions on the base enabling the assembly including the two strips of the closure device to deform so as to occupy little space and facilitate insertion of said strips into the dies of extruders, and to facilitate passage therethrough. 0@ OS 0O S 0* 5 0 0

18. A closure device according to any one of claims 12 to 17, wherein the sum of the widths of the external faces of the ribs is less than or approximately equal to the thickness of the two assembled-together strips in register with the closure elements when said elements are engaged one in the other.

19. A closure device according to any one of claims 12 to 18, wherein the ribs enable the strips to be held between guide elements.

A plastics material bag substantially as herein before described with reference to the illustrations.

21. A closure device substantially as herein before described with reference to the illustrations. OSOS eo see 25 00 of: DATED: 12 February 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: FLEXICO-FRANCE