EP0576499B1

EP0576499B1 - Method of manufacturing flexible containers

Info

Publication number: EP0576499B1
Application number: EP92906677A
Authority: EP
Inventors: Jeffrey Robin Caldwell-Nichols
Original assignee: AgriTay (Holdings) Ltd; AGRITAY HOLDINGS Ltd
Current assignee: AgriTay (Holdings) Ltd
Priority date: 1991-03-21
Filing date: 1992-03-19
Publication date: 1996-06-05
Anticipated expiration: 2012-03-19
Also published as: WO1992016438A1; EP0576499A1

Abstract

A flexible intermediate bulk container is produced by cutting down from a top edge (11) and across the width of a tubular base panel (10) so that at least 25 % of base panel material terminates at cut edges (22) of two apertures (12) and only the remainder continues into opposing portions (30) which are joined at their top edges (11) to provide a lifting handle (31). A top closure panel (40) is secured across the top of the load carrying portion of the container, between the cut edges (22), and below the handle (31). The resultant container has a well defined aperture for lifting purposes and, when filled and stored out in the open, good stability in high winds. Material terminating at the cut edges (22) may be cut away completely, as shown, or may remain as flaps which are incorporated into the handle (31).

Description

TECHNICAL FIELD

This invention relates to a method of manufacturing large capacity flexible containers which are suitable for storage and transport of various goods, particularly dry goods of powdered or granular type.
Such containers are often referred to as flexible intermediate bulk containers and they typically have a capacity in the range from 0.25 - 2.0m³ and are rated as safe for loads of half a tonne up to three tonnes. They are made of flexible material which must be of adequate strength for lifting of the filled containers by engaging one or more handles or loops at the top. The usual material is woven synthetic plastics, for example woven tapes of polypropylene.

BACKGROUND ART

One conventional method is to manufacture containers of this type with a single integral lifting loop or handle at the top for engagement by a fork lift mechanism or hook. For example, EP-A-0118112 discloses a container of this type produced from a body of tubular woven material or from a body of flat woven material which is seamed at the sides. Slits are provided by cuts down from the top edge of the material or by unseamed edge regions above a load carrying section of the container. Top edge regions at respective sides of the cuts or slits are joined and the material above the load carrying section is gathered together, often within a sleeve, to provide an integral lifting loop or handle which includes substantially all the longitudinal fibres or tapes of the woven material. Manufacture of this style of container is simple and inexpensive and consequently it is widely used.
However, the above-described known style of container has certain disadvantages.
One such disadvantage is that the integrally formed lifting loop offers a restricted aperture therebelow as target area for engagement of lifting means, e.g. fork lift tines, because substantially all the longitudinal fibres or tapes of the body material extend into the lifting loop. In practice, fork lift operators have difficulty in accurately aiming for such restricted apertures. This is troublesome in itself and also frequently results in damage to the material of the loop. This can have serious safety implications since if damage to the loop significantly impairs the strength thereof subsequent lifting could be hazardous. Moreover, where such containers have been stacked, the lifting loops of lower containers are generally so collapsed that it is necessary for operatives manually to raise them to expose the aperture for lifting purposes. If this is not done, probing with the lifting means is likely to result in damage to the lifting loop and/or to an inner liner, if present.
A further problem arises when filled containers of this style are required to be stored out in the open for lengthy periods, exposed to all types of weather. Field studies and experiments in a wind tunnel have revealed that a lifting loop which includes substantially all the longitudinal fibres or tapes of the base material flaps so violently in high winds as to lead to disintegration, e.g. by fraying of edges. Even modest exposure to wind speeds which are commonly encountered in practical situations can impair lifting loop strength to such a degree as to make lifting unsafe. Furthermore, material of a liner to such a container, in which the contents are enclosed, is liable to damage by friction either as a result of the violent motion of the lifting loop, particularly if it is frayed or otherwise damaged, or as a result of its own motion where it is exposed and capable of billowing. If the liner is punctured or split it no longer provides an effective barrier to moisture and the contents are likely to be ruined. Thus, considerable economic losses can result from the susceptibility of these containers to wind damage.
EP-A-0382951 also discloses a container with an integral lifting loop consisting of all the material to each side of and above the load carrying section sewn together along their top edges and then gathered together, a sleeve housing the gathered material.
As with the container of EP-A-0118112, such an arrangement produces an aperture of restricted dimensions for insertion of lifting means, and results in a lifting loop prone to damage on exposure to high winds.
GB 2042469 discloses a container in which upward extensions of only part of the walling are used to provide a lifting loop or handle. An upstanding spout is formed between these extensions by making V-shaped cut outs and seaming the edges thereof. This is not a viable method of producing a container. Such V-shaped seaming tends to suffer from high levels of stress at the base of the V causing localised fabric failure at relatively low loads. Furthermore, the spout has been shown in wind tunnel tests to flap violently, resulting in damage to the spout material and any liner within the container in the manner previously discussed.
GB 1581438 discloses a cuboid container in which only half the walling material can extend into the lifting area. This container is produced from at least two lengths of woven material by stitched seams at each join between side and end walls and also along bottom wall edges. This style of container is not economical to manufacture and is not widely used. It has two main limitations, namely inefficient use of fabric strength and the fact that the container inevitably takes up an oval cross section in use as a consequence of two of the four sides being unrestrained, particularly during lifting. Distortion to oval cross section leads to storage problems and stacking can be unsafe.

OBJECT OF THE INVENTION

An object of the present invention is to provide a method of manufacturing a flexible container with at least one integral lifting loop or handle as simply and as economically as possible, and whereby the container so produced requires a minimum of intervention by operatives upon filling and lifting, and is more resistant than any hitherto known container designs to handle and/or liner damage upon lifting or upon exposure to high winds.

DISCLOSURE OF THE INVENTION

With this object in view, the present invention proposes a method of manufacturing a flexible container of the type having side walling of tubular form and at least one lifting loop which is an integral extension of the side walling, characterised by the steps of cutting down from a top edge and across the width of the side walling so as to create at least two apertures and leave at least two portions, joining together said portions at their top edges to provide the lifting loop or loops, and securing closure material to cut edges of the apertures so as to extend below the lifting loop or loops and close off the top of the container.
By having only a proportion of the base material extending to form the lifting loop or loops and by inserting a panel or panels of material to provide a definite top closure to the container, below the loop or loops, a much wider aperture for engagement of lifting means is obtained. At the same time, as the loop or loops are reduced in size they provide a smaller target for impact of wind so flapping thereof and susceptibility to damage in high winds is reduced. The insertion of the top closure material minimises any possibility of wind damage to a liner, as the latter is not free to billow and is not exposed to contact with the flapping handles.
As is conventional, the side walling or base material of the container of the invention will generally consist of woven material having longitudinal and transversely extending interwoven strands. The term "strands" as used here should be understood to include strips or fibres or any other filamentary elements. To achieve the desired enhancement of lifting aperture size and wind stability, while retaining adequate handle strength, the lifting loop or loops should ideally include between 50% and 75% of the said longitudinal strands of the woven material. Conversely, between 25% and 50% of the longitudinal strands of the woven base material should terminate at the cut edges of the apertures.
The body material for production of containers in accordance with the method of the invention consists of tubular walling. This may be formed by flat pieces joined by seams. Preferably, however, the body material is woven in one piece as a tube so as to avoid additional steps of seaming in the production process, which must be kept as cost effective as possible.
In preferred methods of the invention the closure material secured to cut edges of the aperture extends up the aperture edges of the portions providing the lifting loop or loops. Thus, in these cases, a portion of the closure material also forms at least a lower part of the loop or loops. This is advantageous in closing off the inwardly facing sides of the loop or loops, thereby reducing their "sail" effect in windy conditions. It also reduces or eliminates exposure of cut edges, which are vulnerable to disintegration in windy conditions. Moreover, it provides a more effective barrier to ingress of water to the top of the container.
Since securement of closure material to the handle forming portions adds to the complexity of manufacture of the container, it may be omitted to minimise production costs.
Tension across the top closure may be provided by making the width of the closure material less than the width or diameter of the container, for example by at least 20%. An opening may be provided in the closure material to allow for filling of the container. In this respect, the container will in most cases have a liner for receipt of contents and the liner neck may protrude through the opening for filling thereof and be tucked back below the closure material afterwards. A spout may be provided around the opening to facilitate filling.
Alternatively, more than one piece of closure material may be used and an opening therebetween, e.g. between overlapping edges, may allow for filling and/or liner neck protrusion.
In other methods there may be no opening in the closure material itself, and filling and/or liner neck protrusion may simply be by way of unjoined regions of seams, whereby the closure material is secured to the edges of the container base material.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be explained further by reference to a number of exemplary embodiments as illustrated in the accompanying schematic drawings.
In the drawings:

Fig. 1 shows an upper region of a body panel and a closure panel of a first container manufactured according to the method of the invention;
Fig. 2 is a perspective view of an upper region of the same embodiment when fully formed and filled;
Figs. 3 and 4 are corresponding views of a second container manufactured according to the method of the invention;
Figs. 5 and 6 are corresponding views of a third container manufactured according to the method of the invention, and
Figs. 7 and 8 are corresponding views of a fourth container manufactured according to the method of the invention;

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the preferred method of manufacturing flexible intermediate bulk containers in accordance with the present invention, a body panel 10 of tubular woven polypropylene strips is firstly cut to a selected pattern, as shown in Figs. 1, 3, 4 and 7. The tubular blank is laid flat and cuts are made down from a top edge 11 and across the width thereof to produce centrally disposed apertures or cut-outs 12 in register in the confronting layers thereof. This leaves opposing loop or handle forming portions 30 at respective sides of the cut-outs 12. Top edges 11 of these portions 30 are subsequently joined together, typically by stitching for greatest security, to provide a loop or handle 31, for lifting the container, as shown in Figs. 2, 4, 6 and 8. The material of the handle is preferably gathered together and bound by a sleeve 32, as shown, to provide a well defined handle with a clear aperture therebelow for lifting the eventual filled container.
The cut outs 12 have confronting basal cut edges 22, extending across the width of the container between the handle forming portions 30, and confronting side cut edges 24, 26, which extend between the top edge 11 and the basal cut edges 22, up the sides of the handle forming portions 30. One or more closure panels 40, 50, 61, 62, 70 is secured between these confronting cut edges 22, 24, 26, across the top of the container, as will be explained shortly with reference to the respective embodiments. Securement of the panel or panels 40, 50, 61, 62, 70 to the cut edges 22, 24, 26 is generally effected by stitching and it may be accomplished either prior to or after connection of the tops of the portions 30 to form the lifting loop 31.
Between 50% and 75% of the material of the body panel 10, more specifically of the longitudinal strips of woven material thereof, extend into the handle 31. Conversely, between 25% and 50% of the longitudinal strips of the tubular base material terminate at the basal cut edges 22 of the cut outs 12.
The base of the body panel 10 is closed off in accordance with any conventional pattern. For example, it may be cut appropriately to provide for cross shaped seaming or for overlapping flaps seamed across the bottom, or a separate bottom panel may be inserted. The closure of the base is not relevant to the present invention and is not illustrated.
A liner, designated generally by reference numeral 80, and typically of flexible, substantially impermeable plastics sheet material is inserted into the container, for subsequent filling. Such containers are commonly used for powdered or granular fertilsers, or other chemicals, and it is important that these are kept dry within the liner.
Referring to Figs. 1 and 2, in this embodiment an oblong closure panel 40 is provided and is secured along its longer edges to edges of the cut outs 12. In this respect, the panel 40 extends part way up both the side cut edges 24, 26, thus part way up into the handle 31, as is apparent in Fig. 2. Lines of stitching are indicated by crosses, and opposing edges XY, X'Y' of the panel 40 are shown stitched between corresponding positions XY, X'Y' around the edges 22, 24, 26 of the body panel 10.
A slit or slot 41 is provided transversely and substantially centrally of the panel 40 for use in filling the container and the liner neck 80 is shown protruding therethrough in Fig. 2.
Figs. 3 and 4 show an alternative construction in which the panel 50 has no opening therethrough and is of sufficient length to be secured almost to the top of the side cut edges 24, 26, at least as far as where these extend into the handle sleeve 32. To enable filling of the container, one edge of the closure panel 50 is left partially unconnected at 51 so that the liner neck 80 can protrude therethrough.
Figs. 5 and 6 show another alternative construction in which two panels 60, 61 are provided for closure of the top of the container. One of these 60 is secured as shown, XY, and X'Y', along cut edges 22 and 24, while the other 61 is secured as shown, MN and M'N', along cut edges 22 and 26, with a central region of overlap at 62. As in Fig. 4, the panels are shown extending up substantially the full length of the handle forming portions 30. The neck of the liner 80 can be pulled out centrally between the overlapping edges of the two pieces 60, 61 of closure material.
Figs. 7 and 8 show yet another possible construction in which the initial cut outs 12 are of inverted T-shape. Between 25% and 50% of the longitudinal strips of the woven base material still terminate at the cross-cut 72, so that only 50% to 75% extend directly into the handle forming portions 30. However, instead of being completely removed, the remainder of the material of the initial blank provides flaps 73, 74 which are folded towards each other and joined at seams AA', BB' which extend up the inner sides of the handle forming regions 30, as shown in Fig. 8. A smaller panel 70 of material then suffices for closing off the container above the cross cut 72. This is provided with a slit or slot 71 for filling purposes, comparable to that in Figs. 1 and 2.
In all these embodiments the closure panel or panels 40, 50, 60, 61, 70 may conveniently be made of the same material as the body panel 10. However, they may have additional impregnation or coating applied thereto or an additional layer to improve water resistance. Alternatively, a film of water-resistant material may be used for the closure panel. In either of the latter cases, ingress of water to the contents of the container is effectively prevented. During storage of filled containers out of doors water tends to accumulate in pools upon the top closure. Effective water resistance of the closure material and securement of the edges of that material to the body panel is particularly advantageous in preventing access of that water to the container contents either during the course of storage or upon emptying of the container.
Whilst stitching is the preferred method of securement, of the top closure panel or panels to the body material, adhesion or welding or use of fasteners would also be possible.
Whilst the closure panels which extend up into the handle have all been shown as oblong they could advantageously be of a tapered shape, narrowing as they extend further up the handle, so as to match the shape of the latter, and perhaps gather the handle material together more securely, thereby further reducing susceptibility to wind damage.
The maximum secured width of all the closure panels 40, 50, 60, 61, 70 in a direction through the handle 31, i.e. the width X, X' or Y, Y', is advantageously chosen to be less than the width of the base of the container (or of the remainder of the container, when filled) in order that the material connected thereto at the upper margin of the body panel 10 is to some extent drawn over the top of the contents of the container, when filled, so that the top region of the resulting package is reasonably firmly held together. This can be important for stability in windy conditions and also generally for storage and stacking of filled containers. In this respect, a panel which is at least 20% narrower than the remainder of the container may be desirable.
Provision for projection of a liner neck and/or for filling fo the container is not necessary, either by a slit or slot through closure panel, or by leaving an unseamed region, in cases where filling is accomplished through the base of the container.
Although the initial body panel 10 is shown in Figs. 1, 3 and 5 with the handle forming portions 30 at either side of a central cut out 12, it is equally possible, of course, to produce the container from an initial cut panel where the handle forming portions 30 are central and the cut-outs 12 are at respective sides thereof. This is simply a transposition of regions through 90° and is a matter of choice in manufacturing procedure.
Additional areas cut away from the top of the body panel or additional cuts down from the top edge could allow for formation of more than one lifting loop, if desired.

Claims

A method of manufacturing a flexible container of the type having side walling (10) of tubular form and at least one lifting loop (31) which is an integral extension of the side walling,
characterised by the steps of cutting down from a top edge and across the width of the side walling so as to create at least two apertures (12) and leave at least two portions (30), joining together said portions (30) at their top edges (11) to provide the lifting loop or loops (31), and securing closure material (40, 50, 60, 61, 70) to cut edges (22, 24, 26, 72) of the apertures (12) so as to extend below the lifting loop or loops (31) and close off the top of the container.
A method as claimed in claim 1 wherein substantial portions are cut away from top regions of the tubular side walling (Figs. 1 to 6).
A method as claimed in claim 1 or 2 wherein the tubular side walling (10) consists of woven material having longitudinal and transversely extending interwoven strands and, upon production of the apertures (12), between 25% and 50% of the longitudinal strands terminate at cut edges (22, 72) of the apertures.
A method as claimed in claim 1 or 2 wherein the tubular side walling (10) consists of woven material having longitudinal and transversely extending interwoven strands and, upon production of the apertures (12), only between 50% and 75% of the longitudinal strands continue into the portions of material for provision of the lifting loop(s) (31).
A method as claimed in any preceding claim wherein the side walling (10) consists of material which is woven in tubular form.
A method as claimed in any preceding claim wherein the closure material (40, 50, 60, 61) secured to cut edges (22, 24, 26) of the apertures (12) extends up the aperture edges (24, 26) of the portions (30) providing the lifting loop(s) (31). (Figs. 1 to 6).
A method as claimed in any preceding claim wherein an opening (41, 71) is provided in the closure material (40, 70) or between respective pieces (60, 61) of closure material to enable filling access to and/or protrusion therethrough of a neck of a liner (80) to the container.
A method as claimed in any preceding claim wherein the maximum width (X, X'; Y, Y') of the closure material (40, 50, 60, 61, 70) secured between cut edges (22) of the apertures (12) in a direction through the loop or loops (31) is less than the width of the remainder of the container, when filled.
A method as claimed in claim 8 wherein the maximum width of the closure material (40, 50, 60, 61, 70), when secured, is at least 20% less than the width of the remainder of the container, when filled.
A method as claimed in any preceding claim wherein the material of the or each lifting loop (31) is gathered together and a sleeve (32) is provided therearound.