GB1604214A - Flexible bulk containers - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO FLEXIBLE BULK CONTAINERS (71) We, TAY TEXTILES LIMITED, a British Company of Park Mill, Dundee, Scotland, do 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 per formed, to be particularly described in and by the following statement: This invention relates to flexible bulk containers.

Such containers may be used in the storage and transport of materials in granular, powder and other particulate form, such as chemicals, foodstuffs, cement and so forth. The containers are generally in the form af large bags or sacks.

They are often required to carry loads of up to one tonne or more, and there should desirably be a considerable safety margin above this working load. The containers are frequently made from woven fabric, for example woven polypropylene or another suitable synthetic material.

To avoid the use of pallets, slings or the like when lifting a flexible bulk container, it may be provided with lifting means such as loops of high strength webbing stitched to the side of the container. The points of attachment of the lifting loops can be regions of high stress concentration, and failure of or damage to the stitching for the loops, or the bag material itself, may occur. This may be a particular problem if a container is subjected to rough treatment such as intermittent lifting movements which can result in high transient stresses.

Various methods of attaching lifting loops to a container have been propcsed to achieve a high safety factor and to provide an attachment strong enough to resist damage, but these methods can be somewhat complicated, involving for example multiple folds of the bag material, and may still leave the bag material highly stressed. Certain methods of attachment may rcsult in a considerable reduction in the perimeter of the container, thus reducing its capacity.

According to the invention there is provided a flexible bulk container consisting of three woven fabric portions, one of which is Ushaped so as to form first and second side walls and the base of the container, and the remaining two of which are connected across the ends of the U-shaped portion so as to form third and fourth side walls, each of said portions having at least one region extending the length thereof, in which the strength of the warp per unit width is greater than that over at least the major part of the remainder of the portion, lifting means being attached to such regions.

Preferably each portion has a pair of such regions, which may extend along the selvedges as disclosed and claimed in our co-pending Application No. 39234/80 (Serial No 1,604,213 Serial No. 1,604,211) divided from Application 2250/77.

The higher warp strength density in the various regions may be provided by using a higher density of warp threads, by using higher tenacity warp threads, or by a combination of the two.

Warp threads of lower tenacity could be formed as flat polypropylene tape, and those of higher tenacity as twisted polypropylene tape, R.E.F. (roll embossed film) yarns or high tenacity multi-filament yarns. In a preferred construction, whilst the lower tenacity threads are flat tape, the higher tenacity threads are e.g. R.E.F. polypropylene yarns or circular cross-section filaments. Various reinforcing possibilities are disclosed and claimed in the Complete Specification filed in pursuance of our co-pending Application No. 25798/78 (Serial No. 1,604,212). The two types of thread may be of different materials, for example the lower tenacity threads being of polypropylene and the higher tenacity thread of polyester or nylon.

The container may be provided with a top closure member with a filling spout, or a closure skirt which can be drawn together to close the top of the container. A discharge spout may be provided in the bottom of the container.

Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a first embodiment of a container in accordance with the invention; Figure 2 is a detailed view of a corner of the container of Fig. 1; Figure 3 is a sectional plan view of the corner of Fig. 2; Figure 4 is a view similar to Fig. 3, showing another means of reinforcement; and Figure 5 is a view similar to Fig. 3, showing an alternative form of seam construction.

Referring now to the drawings, in Fig. 1 there is shown a flexible bulk container for carrying up to 1 tonne of material, possibly with a safety factor of at least five times this weight. The container includes a bag portion 1, to which are attached four lifting loops 2.

The bag is of woven fabric, for example woven polypropylene although polyethylene ter phthalate, rayon, nylon and so forth could be used. A preferred fabric is 15 X 12 per square inch woven polypropylene tape of 2,000 denier.

The fabric may be sealed by a coating of polypropylene, or by laminated polyethylene.

The loops 2 are preferably webbing e.g.

woven polyethylene terephthalate (e.g. "Terylene", Registered Trade Mark), approximately two inches wide.

The bag 1 comprises three pieces of fabric, namely a substantially "U"-shaped portion 3, forming two sides and the base of the bag, and two rectangular pieces 4 and 5 forming the other two sides of the bag. The fabric pieces are arranged with their warp threads running vertically up the sides of the bag. The pieces are joined by stitching along seams, e.g. a blanket stitch using polypropylene yarn. The selvedges of the fabric pieces 3, 4 and 5 run vertically along the seams, apart from at the base of the bag. Stitching 6 is provided around the top of the bag, to prevent fraying of the fabric. The seam construction and method of attachment of the loops to the bag is shown more clearly in Figs. 2 and 3. The two pieces of fabric 3 and 4 are stitched together along seam 7, by polypropylene yam 8.Between the two pieces of fabric 3 and 4 is an optional reinforcing strip 9 of webbing similar to that from which the loops 2 are formed, and of approximately the same width. The strip 9 is stitched in position, the seam stitching passing through it.

The loop 2 has two legs 10 and 11. The fabric adjacent the seam 7 is pinched together, to form a flange, and the legs 10 and 11 are stitched to the flange, straddling it. Each stitch passes through the legs 10 and 11 of the loop, the two thicknesses of bag fabric, and the reinforcing strip 9. The reinforcing strip 9 extends further along the seam than the legs of the loop 2, to provide additional reinforcement along the seam.

A moisture-proofing strip of deformable moisture - impervious material capable of sealing gaps occurring where the stitches pass through the bag material and the strip, for example of polyethylene, could be positioned in the same way as the reinforcing strip 9.

Moisture-proofing strips could be used in addition to the reinforcing strip 9, for example one being positioned each side of the strip 9.

Figure 4 shows optional reinforcement of the base of the flange, in an arrangement similar to that of Fig. 3. Thus a strip 12 of webbing similar to that of loops 2, but somewhat wider, bridges the base of the flange and is stitched to wall portions of the bag. The strip 12 can run as far down the bag as required. As shown, there is no reinforcing strip 9, but such could be included if required for additional strength.

Figure 5 shows an alternative embodiment employing a different seam construction. In this embodiment two pieces of fabric 3' and 4' are laid together, and then folded back on each other to produce a turnover 13. Stitching 9' is inserted along the fold line, to produce a seam 7'. Legs 10 and 11 are then stitched to the flange incorporating the turnover, the stitches passing through the legs and the four thicknesses of bag fabric. The turnover 13 is somewhat wider than the legs 10 and 11, being for example 2* inches wide.

Although not shown, adjacent the selvedge of the fabric pieces the weft threads are turned back, for example a distance of i inch. This can provide a degree of reinforcement adjacent the seam. Additionally, strengthening is obtained in all embodiments by means of regions of a higher strength density of warp threads extending along each piece of fabric. For example, in a region generally marked 14, adjacent the selvedge of fabric piece 3, there is a higher density of warp threads, and/or warp threads of higher tenacity. Thus, over the majority of the bag, the warp threads could be polypropylene tape having a tenacity of perhaps 4 to 6 g/denier. In regions such as 14, adjacent selvedges, the warp threads could be polypropylene R.E.F. yarns having a tenacity of 5-7 g/denier or multi-filament polypropylene yarns. The width of the region 14 is such as to accommodate the legs of the loop, and the reinforcement suip 9.

A feature of the above described embodiments is that lifting forces are transmitted by regions of reinforcement of the bag fabric, between the top and the bottom of the bag.

The arrangement is such that stresses in un reinforced regions of the bag fabric may be reduced.

Attention is drawn to our co-pending Appli cation Nob 2250/77 (Serial No. 1,604,211) from which this Application was divided, No.

39234/80 (Serial No. 1,604,213) also divided from that Application and No. 25798/78 (Serial No. 1,604,212).

WHAT WE CLAIM IS:- 1. A flexible bulk container consisting of three woven fabric portions, one of which is U-shaped so as to form first and second side walls and the base of the container, and the remaining two of which are connected across the ends of the U-shaped portion so, as to form third and fourth side walls, each of said por tions having at least one region extending the length thereof in which the strength of the warp per unit width is greater than that over .at least the major part of the remainder of the portion, lifting means being attached to such regions.

2. A container as claimed in claim 1, wherein the threads in the regions of greater warp strength are of a higher tenacity than elsewhere.

3. A container as claimed in claim 2 wherein the threads in the regions of greater warp strength are multi-filament polypropylene yarns.

4. A container as claimed in claim 2 or 3 wherein the warp threads outside the said regions of greater warp strength are in the form of polypropylene tape.

5. A container as claimed in any preceding claim wherein there is a higher density of warp threads in the regions of greater warp strength than elsewhere.

6. A container as claimed in any preceding claim wherein the width of each region of higher warp strength is at least equal to the width of lifting means which are connected thereto.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   reinforced regions of the bag fabric may be reduced.

   Attention is drawn to our co-pending Appli cation Nob 2250/77 (Serial No. 1,604,211) from which this Application was divided, No.

   39234/80 (Serial No. 1,604,213) also divided from that Application and No. 25798/78 (Serial No. 1,604,212).

   WHAT WE CLAIM IS:- 1. A flexible bulk container consisting of three woven fabric portions, one of which is U-shaped so as to form first and second side walls and the base of the container, and the remaining two of which are connected across the ends of the U-shaped portion so, as to form third and fourth side walls, each of said por tions having at least one region extending the length thereof in which the strength of the warp per unit width is greater than that over .at least the major part of the remainder of the portion, lifting means being attached to such regions.
2. 2. A container as claimed in claim 1, wherein the threads in the regions of greater warp strength are of a higher tenacity than elsewhere.
3. 3. A container as claimed in claim 2 wherein the threads in the regions of greater warp strength are multi-filament polypropylene yarns.
4. 4. A container as claimed in claim 2 or 3 wherein the warp threads outside the said regions of greater warp strength are in the form of polypropylene tape.
5. 5. A container as claimed in any preceding claim wherein there is a higher density of warp threads in the regions of greater warp strength than elsewhere.
6. 6. A container as claimed in any preceding claim wherein the width of each region of higher warp strength is at least equal to the width of lifting means which are connected thereto.