Source: http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/patent/1240935/summary.html
Timestamp: 2019-11-12 00:29:11
Document Index: 266414120

Matched Legal Cases: ['art.\n3', 'arts\n12', 'arts 12', 'arts 14', 'arts 16', 'arts 18', 'art 15', 'art 12', 'arts 12']

Patent 1240935 Summary - Canadian Patents Database
Canadian Patents Database / Patent 1240935 Summary
(11) CA 1240935
NATTRASS, FRANK (United Kingdom)
BOWATER PACKAGING LIMITED (Not Available)
8420600 United Kingdom 1984-08-14
A flexible bulk container has a side wall
structure formed from a length of tubular woven fabric
comprising a base fabric and a plurality of parallel
reinforcing bands integrally woven with the base fabric and
extending parallel to the tube axis. A bottom is stitched
to the side wall structure at one end of the fabric length
and a top wall structure may be secured at the other end of
the fabric length. The container has a plurality of lifting
loops at the top end of the fabric length, each lifting loop
being formed by cutting back a portion of the base fabric
alongside each of two adjacent reinforcing bands to leave
parts of the bands projecting from the base fabric, and
securing together the free ends of the projecting parts to
form the loop. One of the projecting parts may be twisted
through 180° before the free ends are joined together.
1. A flexible bulk container comprising a side wall
structure formed from a length of tubular woven fabric, the
fabric comprising a base fabric and a plurality of parallel
reinforcing bands woven integrally with the base fabric and
extending parallel to the axis of the tube, a bottom
stitched to the side wall structure at one end of the
length of fabric, and a plurality of lifting loops at the
other end of the length of fabric, each lifting loop being
formed by cutting back a portion of base fabric alongside
each of two adjacent reinforcing bands to leave parts of
these bands projecting from the base fabric, and securing
together the free ends of the two projecting parts.
2. A flexible bulk container according to claim 1 in
which one of the projecting parts is twisted through 180°
before being secured to the other projecting part.
3. A flexible bulk container according to claim 1 in
which the portions of the base fabric that are cut back
adjacent to each reinforcing band are folded around and
stitched to the respective band.
4. A flexible bulk container according to claim 1 in
which the tubular woven fabric has eight parallel
reinforcing bands, and projecting parts of adjacent pairs
are joined together to form four lifting loops.
5. A flexible bulk container according to claim 1 in
which the fabric is of polypropylene warp and weft base
threads, and each reinforcing band comprises additional
warp threads interwoven with the weft base threads and
having a higher tensile strength than the base warp
II~PROVEMÆNTS ~ELATING TO BULK CONTAI~ER~S
This invention relates to ~lexible bulk containers
such as are used in the storage and transport of materials
5 in granular, powder and other particulate forms.
Such containers are generally in the form of large
bags or sacks which are often required to carry loads of up
to one tonne or more with considerable safety margin above
this working load. The containers are commonly made from
10 woven ~abric, particularly woven polypropylene or other
suitable synthetic material. There have in the past been
many proposals for the manufacture of such containers, and
also many proposals for providing the containers with
lifting loops at the upper part of the container. In the
15 most commonly used construction the lifting loops are loops
of high strength webbing which are stitched to the side
walls of the container, desirably so that there is
reinforcement in the area where stitching occurs. For
example, the side wall fabric may be folded so that each
20 loop is stitched to a plurali~y of thicknesses of material.
In another known arrangement each loop may be stitched to
the side wall in the region where the side wall fabric is
The points of attachment of the lifting loops to the
25 side walls are generally regions of high stress
concentration, and despite reinforcement the areas
surrounding these connections are the commonest failure
areas for these containers. This is particularly the case
where the container is mishandled, for example lifted or
30 pulled with only a single loop of the container engaged by
the lifting or pulling means. A number of attempts have
been made to design constructions which provide a loop
structure such that damage of this nature is positively
avoided, but it is extremely difficult to obtain a
35 satisfactory solution at an economic cost. The object of
the invention is to provide a container with improved
stress distribution into the side wall structure~
According to the invention a flexible bulk container
comprises a side wall structure formed from a length of
5 tubular woven fabric~ the fabric comprising a base fabric
and a plurality of parallel reinforcing bands woven
integrally ~ith the base fabric and extending parallel to
the axis of the tube, a bottom stitched to the side wall
structure at one end of the length of fabric, and a
10 plurality of lifting loops at the other end of the length
of fabric, each lifting loop being formed by cutting back a
portion of base fabric alongside each of two adjacent
reinforcing bands to leave parts of these bands projecting
from the base fabric, and securing together the free ends
15 of the projecting parts.
It will be seen that each loop is formed by a
continuous extension of two adjacent reinforcing bands, and
that those bands are woven integrally with the base fabric.
Thus, there is no stitched connection wha~soever between
20 the individual lifting loops and the side walls of the
container and, apart from avoiding the operation of
stitching the loops to the side walls, this arrangement
avoids the stress concentrations at the stitchiny points
and significantly improves the distribution of stress from
25 the lifting loops o~er the container side wall fabric.
Furthermore, the use of tubular woven fabric, which has
continuous weft threads extending around the full
circumference of the container, leads to an additional
improvement in stress distribution around the container
30 side wall structure.
Preferably one of the projecting parts is twisted
through 180 before being secured to the other projecting
The imparting of 180 twist to one of the projecting
35 parts forming each lifting loop is found, most
3~ii
surprisingly, materially to improve even further the stress
distribution, and the introduction of this twist renders
the loop substantially fully resistant to damage and tear-
out from the container even when the container with its
5 rated load is lifted or pulled with only a single loop
engaged by the lifting or pulling means. A solution to the
pull~out problem is thus provided in an extremely simple
and inexpensive manner, and additionally the container
construction itself is relatively cheap due to the use of
10 tubular woven fabric which avoids the necessity of having
to form side seams between adjacent panels of a side wall
The container may be open or, more preferably, may
be closed by a top stitched to the side wall structure and
15 adjacent to the lifting loops opposite to the bottom of the
container. The top may be formed with any suitable opening
and/or skirt arrangement and the bottom may be formed with
any suitable discharge arrangement. If required the
container may be formed with an inner, impervious, liner
20 within which the load is contained, to give added
protection against the ingress of moisture and also to
prevent fine ~aterial escaping from the container.
The portions of the base fabric that are cut back
adjacent to each reinorcing band are desirably folded
25 around the respective band and stitched to the band in
order to protect the band from chafing and to give added
strength to the lifting loop.
The invention is particularly suitable for a container
having four lifting loops, in which case the tubular woven
30 fabric will have eight parallel reinforcing bands. Four
loop bags are probably the most common in the field of bulk
containers, and an additional advantage provided by the
invention is that such containers can be made with four
stitching operations to sew together the ends of adjacent
35 projecting parts, rather than with eight stitching
operations as are needed conventionally when each lifting
loop is stitched at ea~h end to the side wall structure of
the ~ontainer.
In another embodiment tubular woven fabric having four
5 reinforcing bands can be formed into a container having two
lifting loops.
Formation of a tubular woven fabric having integral
reinforcing bands extending parallel to the axis of the
tube can readily be achieved by conventional weaving
10 techniques. The reinforcing bands may be provided, for
example, by the cramming of warp threads in the region of
the reinforcing band, i.e. by making the warps per
centimetre in the reinforcing band regions greater than the
number of warps per centimetre in the base fabric of the
15 tube. Alternatively, the reinforcing bands may incorporate
warp yarn of a higher tensile strength than the warp yarns
of the base fabric. These higher strength yarns may
replace entirely the warp yarns used for the base fabric,
or they may be used in addition to those warp yarns so that
20 each reinforcing band will incorporate both base fabric
warp yarns and higher strength warp yarns.
In a preferred arrangement the material oE the tube
may be woven fabric having polypropylene warp and weEt
threads interwoven in any appropriate weaving pattern,
25 usually smooth woven, although twill, basket and rib weaves
may also be used. Interwoven with the polypropylene weft
threads in the regions of the reinforcing bands are
additional warp threads having a higher tensile strength
than the base polypropylene warp threads. The reinforcing
30 threads may be made from any suitable natural fibre or from
yarn of synthetic or semi-synthetic polymer, such as
polyester, polyamide, polyolefin or polyacrylic. The
higher strength warp threads may alternatively also be of
polypropylene, which may be of a higher count than the base
35 polypropylene threads or may be a thread similar to the
~4~3S
base thread which has been treated, i.e. by fibrillation,
in order to increase its tensile strength. The suggested
materials given in this paragraph do not constitute an
exhaustive list, and other materials that can be used will
5 be apparent to those skilled in the art.
In order that the invention may be better understood
the manufacture of a specific embodiment of container in
accordance with the invention will now be described in more
detail, by way of example only, with reference to the
10 accompanying drawings in which Figures 1 to 4 show
successive stages in the manufacture of a container.
Referring now to Figure 1 this shows a blank in the
form of a length of tubular woven fabric. The fabric
comprises a base fabric 1 and eight parallel reinforcing
15 bands 2 to 9 woven integrally with the base fabric and
extending parallel to the axis of the tube. In order to
form lifting loops for the container, sections of base
fabric lying between adjacent reinforcing bands at one end
of the length of fabric are cut as shown in Figure 1.
20 Thus, between each pair of adjacent bands a first cut 10 is
made mid-way between the two bands and extending parallel
to the bands, and from the bottom of that cut a transverse
cut 11 is made extending circumferentially of the fabric to
terminate ad~acent to each of the two respective bands.
25 The result of these cuts is to leave a section of each
reinforcing band to which is attached two flaps, one lying
to each side of the band. Thus, band 2 has attached flaps
2a and 2b, band 3 has attached flaps 3a and 3b and so
forth. The two flaps associated with each band are then
30 folded around the band and stitched to it in order to form
a protective covering for the band, whereupon the blank
takes on the form shown in Figure 2. In this form, parts
12 to 19 of the reinforcing bands 2 to 9 project from the
base fabric in a direction parallel to the axis of the
35 tube.
In order to form lifting loops the parts 12 and 13 are
secured together, parts 14 and 15 are secured together as
are parts 16 and 17 and parts 18 and l9. Before such
securing~ however, in a first embodiment of the invention
5 one part of each pair is twisted through 180 as shown, for
example, by the twisting of part 15 in Figure 2. The ends
of the twisted and untwisted parts are then overlapped and
the overlapping region is stitched to form a loop as shown
in Figure 3. When each loop has been completed the 180
lO twist that was present in one part forming the loop is
taken up through the length of the loop so that the twist
therein is gradual along its length.
After formation o~ the loops 20 to 23 a square top 24
is stitched to the side wall structure at the end adjacent
15 the loops, which will of course be the to~ of the
container. The top may be formed with any suitable filling
arangement 25. Similarly, a square bottom 26 is stitched
to the side wall structure at the opposite end of the
length of fabric, and the bottom may be formed with a
20 suitable discharge arrangement 27. If required, the
container may be provided with an impervious inner liner.
~ he simplicity of manufacture of the container will be
appreciated from the ~oregoing description. The strength
of the base fabric and of the reinforcing bands forming the
25 liEting loops are, of course, chosen according to the rated
load of the container in order to give an appropriate
factor of safety, usually required to be at least 5:1.
Stress distribution in the side wall structure is found to
be excellent. Surprisingly, it has been found that a
30 container so manufactured is capable of lifting the rated
load with just one of the four loops engaged by the lifting
means. It is the presence of 180 twist in each lifting
loop that leads to this result, and of course the described
method of manufacturing the container makes it extremely
35 easy for this twist to be inserted.
In a second embodiment of the invention each part 12
to 19 of the reinforcing bands is left untwisted, and
adjacent parts 12, 13, 14, 15, 16, 17 and 18, 19
respectively are stitched together at their ends in the
5 untwisted condition. The resulting container has excellent
stress distribution in the side wall structure, but is
somewhat less resistant to failure if lif~ed on one loop
than is the case in the first embodiment wherein the loops
The examples described have been of containers having
four lifting loops, but the invention may also be applied
to a container having only two loops. In this case the
tubular fabric will be woven to have four reinforcing
bands, upper parts of adjacent pairs of which are then
15 joined to form the lifting loops, with one part of each
pair twisted if required.
In either embodiment the top and bottom of the
container need not be square, but may be circular or of any
other suitable shape. Furthermore, the base may be formed
2~ from a continuation of the tubular woven fabric used for
the side wall structure, suitably cut, folded and stitched
to the required shape. A base formed in this way may
replace, or supplement, a separate fabric base stitched
Sorry, the representative drawing for patent document number 1240935 was not found.
Forecasted Issue Date 1988-08-23
(22) Filed 1985-07-25
(45) Issued 1988-08-23
Expired 2005-08-23
Filing $0.00 1985-07-25
BOWATER PACKAGING LIMITED
Drawings 1993-08-20 2 80
Claims 1993-08-20 1 43
Abstract 1993-08-20 1 24
Cover Page 1993-08-20 1 15
Description 1993-08-20 7 328