EP0400826B1

EP0400826B1 - Flexible container

Info

Publication number: EP0400826B1
Application number: EP90305016A
Authority: EP
Inventors: Gordon Chilmaid
Original assignee: MEDWAY PACKAGING Ltd
Current assignee: MEDWAY PACKAGING Ltd
Priority date: 1989-05-30
Filing date: 1990-05-10
Publication date: 1993-02-03
Anticipated expiration: 2010-05-10
Also published as: DE69000855D1; EP0400826A1; ATE85287T1

Abstract

A flexible container (10), including a closed end (16), the closed end being formed by folding an open end portion (19), and joining means joining said folded end portion (19) to the body of the flexible container (10), said joining means being arranged so as to join said folded end portion to said body more strongly over outer sections (26, 27) adjacent each side edge (23, 24) of said flexible container than over an inner section (28) spaced from said side edges.

Description

The present invention relates to a flexible container such as a sack and in particular, a paper sack.
It is a common requirement of flexible containers such as sacks that they should be securely closed so that during transportation and storage the sack remains firmly closed and the contents are retained inside the sack. However, when it is desired to empty the sack of its contents, the sack should be easily openable without any tools.
A variety of means for dealing with this problem have been devised and a colon method is by means of sewing up a closed end of the sack utilising a tape and a particular form of stitching. In normal use the stitching and tape are strong and will maintain the sack closed, but when it is desired to open the sack, the stitching may be grasped at a particular point and readily parted from the sack whereby the end of the sack is opened.
Although this arrangement is useful in many circumstances, where the sack is utilised to hold food raw material or products, in particular, there is the possibility that the loose ends of the tape and of the thread used to sew up the sack will become dislodged and enter the food process with undesirable results. There is therefore a demand for a flexible container in the form of a sack which can readily be opened without loose parts of the closure breaking away and joining with the contents of the sack.
Much work has been carried out in this direction and various proposals have been made for meeting the problem.
One of these is shown in European Patent Publication 283279 which shows a sack with a releasable end closure in which a long extended end of the sack is folded over in a particular way to provide a "peak" which is taped down with an adhesive tape (the so-called "cap strip"). To maintain the strength of this sack it is necessary to provide a long fold and the sack can be readily opened by grasping the peak below the cap strip and pulling on that peak portion to disengage the adhesive cap strip. Such an arrangement works quite well but in practice, has disadvantages. One disadvantage is that a considerable extra length of material is required to form the closure which in the very competitive industry of paper sacks can be of considerable economic importance.
Another arrangement is disclosed in UK Patent Application 2208222. In this, an open end of the sack is folded over and is held closed by means of a tape which adhesively connects the body of the bag and the folded over portion, the tape having a free edge which may be grasped so as to pull the tape off the body of the bag to release the folded up end. The adhesive connecting the tape to the bag must be sufficiently strong to maintain its integrity and yet at the same time must be disconnectable readily when the bag is to be opened.
US Specification 2 363 957 discloses an envelope or container in which one end is closed by a folded over flap 30. The flap 30 is adhered to the remainder of the envelope by adhesive under lobes 32 spaced towards each side of the envelope, leaving an unadhered portion between, and the actual opened end is sealed by means of releasable adhesive 37. The releasable adhesive 37, forming the main closure of the open end of the envelope extends substantially to either side of the envelope. The unadhered portion between the lobes 32 could allow dirt to collect beneath the flap which in the case of use of a container with food stuff such as flour is unacceptable.
Reference is also made to US Patent No 4 512 479 which discloses a container having an easy opening closure which includes an adhesive layer seal having a bonding strength adjacent one end of the flap to facilitate opening of the container.
According to the invention there is provided a flexible container, including a closed end, the closed end being formed by folding an open end portion, and an adhesive joining said folded end portion to the body of the flexible container, characterised in that adhesive is applied to one of said end portion or body as a contiguous strip transversely of the body from one side to the other, the other of said end portion or body having a coating or layer thereon over the surface of an inner section of the body located centrally of said container between outer sections which extend towards said inner section from the adjacent sides of the container, said coating or layer consisting of a material having a low tack relationship with said adhesive whereby the one and the same contiguous adhesive strip adheres more strongly to the surface of the body over the outer sections where the coating or layer is not present, than over the inner section where the coating or layer is present.
Thus a relatively simple fold of an open end can be provided to close the open end, and the folded over portion is more strongly joined to the body adjacent the sides of the flexible container where there is most stress and the likelihood of failure of the joint, than at a central portion of the container (the "inner section"). This means that the closure over the inner section can be more readily opened.
To prevent ingress of dirt or insects into the sack and to provide a complete seal, the inner and outer sections should be contiguous and extend to the outer sides of the sack.
Preferably said inner section includes a loose edge so that fingers can be inserted under the loose edge to break the joining means at said inner section to thereby open said closed end of the flexible container.
Preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

FIGURE 1 is a view of tubes of paper material from which sacks according to the invention may be manufactured,
FIGURE 2 is a back view of a tube of Figure 1 before folding,
FIGURE 3 is a back view of a sack incorporating a first embodiment of the invention,
FIGURE 4 is a back view of the sack corresponding to the lower part of Figure 3 after it has been opened,
FIGURE 5 is a diagrammatic back view of a sack incorporating a second embodiment of the invention, and
FIGURE 6 is a view of a sack during manufacture comprising a third embodiment of the invention.

Figure 3 shows the back view of a sack 10. The paper sack is for the storage and transportation of flour, but may be used for other purposes. As is well known, the paper material of the sack 10 may be multi-ply.
Referring to Figure 1 it will be seen that the paper sacks 10 are manufactured from a strip or strips of material (s) which is (are) folded over so that opposite longitudinal edges 12, 13 overlap, the opposite longitudinal edges 12, 13 being adhesively joined to one another to provide a joint 14. The tubular member thereby produced is divided transversely by suitable cutting means to provide a succession of open ended tubes 10A, 10B from each of which a paper sack may be made.
Conventionally, the sack manufacturer closes a first end 16 of the open ended tubes 10A, 10B (as shown in Figure 2) to form sacks having a second, open, end 17 (as shown in Figure 3) and the user, having filled the sacks, closes the second, open, ends 17 of the sacks.
As is illustrated in Figure 2, the first end 16 of a paper sack 10 is closed by folding an end portion 19 over a fold line 21, the fold line 21 being parallel to the cut open end 16 of the sack 10 and spaced therefrom. The folded over end portion 19 is then connected to the body 22 of the sack 10. In a preferred embodiment to be described, the end portion 19 when folded over is adhesively attached to the body 22. Thus, to do this, adhesive is applied to either the end portion 19 (at 25A) or the body 22 (at 25B) just above the fold line 21 across the complete width from side 23 to side 24 of the sack 10.
Such an arrangement is, of course, entirely conventional. However, in the present instance, it is arranged that the end portion 19 is divided into three sections, outer sections 26, 27 each extending from respective sides 23, 24 inwardly towards the middle of the sack, and an inner section 28 which extends between the two outer sections 26, 27. An important aspect is that the outer sections of the end portion 19 are more strongly adhered to the body 22 than the inner section 28 of the end portion 19.
It is preferably also arranged that, at least over the inner section 28, the adhesive is not applied to the remote end of the end portion 19 (ie adjacent the cut edge 20) so that when the end portion 19 is folded over the fold line 21 and adhesively connected to the body 22, there is a small flap 31 left which may be grasped.
Thus, in use, once the sack has been manufactured as described, it may be filled by the user with the relevant material and the second open end 17 closed as in the conventional manner. The closure of the second open end 17 may be arranged in any manner, since it will remain closed thereafter and it is not necessary for it to be opened at that end.
In use, to remove the material from within the closed sack 10, the flap 31 of the end portion 19 (which as indicated above, may preferably not include adhesive so as to be grasped by the fingers of the hand), may be gripped along the inner section 28 and pulled so as to break open joint lines 36, 37 between the inner section 28 of the end portion 19 and the body 22. The greater adhesion between the outer sections 26,27 and the body 22 will mean that they remain adhesively closed and so the end portion 19 will tear at the joint line 36 between the outer section 26 and inner section 28, and the joint line 37 between the inner section 28 and outer section 27. Figure 4 shows the end 16 of the sack after it has been opened in this manner. Material from inside the sack may be poured out via the, now, open section 28.
Furthermore, because there are no loose parts arising as a result of this opening process, there is no likelihood of loose parts such as loose ends of thread becoming disconnected and joining the flow of material out of the sack 10.
Of course, it will be understood that the use of the stronger adhesion over the outer sections 26, 27 is necessary because most of the forces tending to undo the end portion 19 will arise adjacent the sides 23, 24. So long as the end portion 19 adjacent the sides 23, 24 is maintained firmly closed by the use of the stronger adhesion over the outer sections 26, 27, less strong adhesion can be used in the central portion over the inner section 28.
The different strengths of adhesion of the inner section and outer sections is achieved (as shown in Figure 6) by printing an area 35 of lacquer or like material onto the surface of the area of the inner section 28 of the body 22, so that a single adhesive can be applied to the end portion 19, the adhesive more strongly adhering to the body 22 over the outer sections 26, 27 where the lacquer is not present, than over the inner section 24 where the lacquer is present.
When folded over about the line 21, in the area of the strip 34, the two plies 32A, 32B, overlie one another so that in this central area, there is added strength to the part of the sack which will be gripped and pulled to open the sack.
In an alternative arrangement of the embodiment of Figure 5, in place of the crossed lines of adhesive as shown in Figure 5, similar lines of printed lacquer are provided, adhesive being applied across the lacquer or across the surface which will be folded into contact with the lacquered surface and by controlling the relative area of the lines of lacquer (which does not adhere well to the adhesive), the effective strength of the adhesive can be controlled. In place of the lines shown in Figure 5, one can provide areas of lacquer in the form of an array of shapes such as circular dots, triangles or diamonds, and the relative sizes of these dots, triangles or diamonds of lacquer to non-lacquered surface may be increased or decreased across the area where the adhesive is to be applied so as to vary the effective strength of the adhesive.
In place of printed lacquer one might use other printed materials such as ultra violet cured ink to which a hot melted adhesive will not readily adhere and thus by varying the relative proportion of the printed to non printed parts (i.e. by varying the size of the dots or triangles or diamonds), one can change the effective strength of the adhesive.
Such an arrangement of use of other printed materials such as ultra violet cured ink with hot melted adhesive enables one to manufacture the sack in a slightly different way. The arrangements thus far described show the first closed end of the sack closed in accordance with the invention. This process is normally carried out by the sack manufacturer; the sack is then shipped to the user and the user closes the opposite end of the sack in a conventional manner by for example adhesive or sewing. With the use of hot melted adhesive and other printed material such as ultra violet cured ink, it is possible to provide the closure of the invention on the end of the sack which is closed by the user since the second end can be printed with other printed materials such as ultra violet cured ink, and provided with the hot melted adhesive and the user can simply close that second end by folding over the second end and melting the adhesive in the normal manner.

Claims

A flexible container (10), including a closed end (16), the closed end (16) being formed by folding an open end portion (19), and an adhesive (25A, 25B) joining said folded end portion (19) to the body (22) of the flexible container (10), characterised in that adhesive is applied to one of said end portion (19) or body (22) as a contiguous strip transversely of the body from one side to the other, the other of said end portion or body having a coating or layer thereon over the surface of an inner section of the body located centrally of said container between outer sections (26, 27) which extend towards said inner section from the adjacent sides of the container, said coating or layer consisting of a material having a low tack relationship with said adhesive whereby the one and the same contiguous adhesive strip adheres more strongly to the surface of the body over the outer sections (26, 27) where the coating or layer is not present, than over the inner section (28) where the coating or layer is present.
A flexible container as claimed in claim 1, characterised in that the coating is a lacquer or ultra violet cured ink.
A flexible container as claimed in claim 1 or 2, characterised in that said inner section (28) includes a loose edge (31) so that fingers can be inserted under the loose edge (31) to break the joining means (25, 25A, 25B) at said inner section (28) to thereby open said closed end (16) of the flexible container (10).