Apparatus for and method of cutting stitching threads joining consecutive
bags on a bag making line
Background of invention:
For the packaging of fine powder form products like cement, chemical powder or
granular form products like fertilizer, polymer or animal feedstuff etc., in sacks or
bags of web structure, it is desirable to have provision of valve, suitable for filling
opening. In industry, there are basically two types of valve sacks, block-bottom
type and cushion type.
In the cushion type sacks made from normal web tubular structure, the valve is
formed by inward folding of any one corner of tubular web length and transverse
seaming of straight open edge (Figure 1). These types of cushion sacks are usually
prepared manually or with help of valve bag conversion lines.
On the valve bag conversion machine, after the stitching of top seam with valve
portion, it has been observed that there is an extra-long length chain stitch thread
between two adjacent bags which remains attached to the valve portion (Figures 2
and 3). The very existence of this left-over thread is due to the triangular
configuration of the valve. In the case of sacks without triangular valves, the sacks
are rectangular in configuration and the problem of left-over thread does not arise
(Figure 4). This left-over thread, which is left hanging by the valve portion, causes
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severe problem during the subsequent downstream processing like coating,
printing, packing and final usage on filling station.
Removal of this undesirable portion of thread by cutting it manually is a labour
intensive and tedious process and not suitable for modern automated sack
production lines. Advantageously no extra labour is required by this automated
process, thus the labour cost is also reduced.
Presently, the conventional single cutter devices which suited the pillow bag
manufacture (Figure 5) are typically used for pillow shaped bags with inward
folded valves. It should be easily understood that while it is possible to make a
single cut in this thread using conventional cutters, at least any one of the two
bags between which the thread lay would be left with an undesirably long yarn.
Therefore, the problems caused by undesirably long threads are not overcome.
Hence, there is a need to develop an effective apparatus for cutting and removal of
extra thread length from each bag on the conversion line. Present invention has
the advantage that cutting of extra thread length between two consecutive bags is
now removed by an automated process.
List of Figures:
Figure 1: Pillow-shaped bag with inward folded valve
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Figure 2: Pillow shaped bags with valves with connector threads
Figure 3: Extra length of thread
Figure 4: Bags without inward folded valves with connector threads
Figure 5: Schematic of a conventional single cut apparatus
Figure 6: Schematic of a dual cutter apparatus of the invention
Figure 7: Cutting device in working stage
Figure 8: Cutting device in non-working stage
List of Parts:
1. Pillow shaped bag with an
inward folded valve
2. Triangular shaped valve
3. Connector thread between
two consecutive bags on the
conveyor line
4. Undesirable extra length of
thread
5. Single Cutter Apparatus
6. Cutting device
6A. Dual cutter mechanism
7. Guiding plate
8. Fixed element
9. Movable element
10. Actuating mechanism
11. Mounting plate
12. Waste collection box
13. Sensing mechanism
13A. Sensor
14. Central controller
Objectives of invention
The objectives of the present invention are:
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a) To provide an effective apparatus for cutting of extra length of stitched
yarn which originates from a valve in valve bag
b) To provide a yarn cutting apparatus as described above which is easily
adaptable to conversion line
c) To provide means for disposal or collection of cut end of stitched thread
d) To provide means of cutting stitched yarn in which the cutter blades are
detachably mounted with provision for re-sharpening or replacement
Summary of Invention:
The present invention provides an apparatus for and method of cutting stitching
threads joining consecutive bags on a bag making line. When all stitching of
pillow-shaped storage sacks is completed on an automated bag making line, any
two consecutive bags are still connected with a stitching thread. The present
invention discloses an apparatus that cuts this connecting thread in a manner that
the problems caused by leaving an undesirable length of thread still attached to a
finished bag are eliminated. The apparatus of the invention provides a cutting
device that makes at least two cuts in the connector thread and an automated
method of doing so.
Description of invention:
On the valve bag conversion unit, the tubular fabric is fed-in in the roll form on an
unwinder station. The desired length of fabric is unwound from the roller through
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a tension compensator and fed to the cutting station. Next, a suitable cutting
device like thermo-cutter cuts the desired length of fabric which is then moved
forward on to the bottom seaming station. After the completion of the bottom
seam, the bottom stitched and cut fabric is moved with help of conveying device
onto an inward folding station. On the inward folding station, the open end of the
cut fabric, namely the top end, is then transformed at its one corner into an inward
fold to prepare a valve portion. The tubular fabric structure with an inward fold at
its one corner is made pass through top edge folding unit onto seaming station.
Thus an inward folded valve whereby a cushion shaped bag (1) with an inward
folded valve (2) is formed (see Figure 1).
Now as the bag under operation is gradually moved away from the stitch/seaming
station with help of conveying device, another bag follows the first bag, as
machine is in continuous operation mode. As the stitching/seaming operation is in
continuous mode, there is continuous chain stitch thread or a connector thread (3)
between the stitched bag just moved and next adjacent bag under stitching
operation (see Figure 2).
As seen from Figure 4, in the case of bags without triangular valves, the length of
the connector thread can be kept to a minimum and no excess thread length (4)
(see Figure 3) is caused on account of the valve. In the conventional system (see
Figure 5), a single cutter apparatus (5) is used to cut the stitched thread joining
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two adjacent bags. However, it can be visualised from Figure 3 that at the inward
folded valve portion of bag – due to the triangular configuration of the fold – there
is considerable excess length (4) of thread, sagging from bag body. This extra
thread creates many issues in the subsequent operations like coating, printing,
stacking or usage on the filing station. Hence, this sagging extra thread had to be
cut manually, which cannot assure quality work and is expensively slow.
To overcome the problem of sagging extra thread length, a mechanism to make at
least two cuts (or a dual cutter mechanism) (6) and the method disclosed (see
Figure 6) in this application tackle this issue by eliminating this excessive thread
length in a single operation. With the help of suitable sensor and timer
mechanism, the double cutter system of the present invention is activated such
that it cuts the continuous chain stitch thread between adjacent bags at two pre-set
location.
The inventive cutter system is designed and constructed in a manner that the
portion of the extra stitch thread (4) near the valve area is detected, cut and
disposed of. As seen from Figure 7, the apparatus of the invention comprises a
guiding plate (7), at least two cutting devices (6) or tools, a sensing mechanism
(not shown in figures) (13) to sense arrival of the bags with loose thread joining
them, a mounting plate (11) for mounting the cutting tools, an actuation
mechanism (10) to activate the action of the cutting devices (6), and a cut thread
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disposing system (12). The sensing mechanism (13) comprises preferably a photo
electric sensor (13A) that use light sensitive elements to detect objects and a
facility to send signal to the central controller (14). The sensors have an emitter
(light source) and a receiver (not shown in figure), and sense objects through the
signals sent to and received from the central controller (14) (which has a purpose
build PLC unit) (not shown in figure). The central controller, upon receiving a
signal from the sensor (13A) indicating that the bags are positioned in a
predetermined position, also sends a signal to the actuation device(s) so that the
actuation device(s) in turn activate the cutting devices.
After top side stitching of bag, the bag is then guided with the help of guiding
plate (7) in forward direction, where the sensing mechanism mounted at the
suitable location senses the bag and gives feedback to central controller which
then sends a signal to the actuation device which in turn actuates the cutting
devices (10).
As shown in Figure 8, in one of the embodiments each cutting device has two
elements – a fixed element (8) and a movable element (9). In one embodiment, the
movable element (9) is a blade that is preferably sharp. The thread to be cut (4) is
positioned over the top of the fixed element (8). The movable element (9) moves
in a way such that the thread (4) is cut preferably by a shearing action between the
fixed and movable elements (8, 9). This shearing action takes place at each cutting
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device (6). The cutting device (6) can be adjusted on mounting plate in forward
direction as well as backward direction according to bag length so that the thread
to be cut is positioned over the fixed element. The forward direction is the
direction of forward movement of the bags of the mag making line and the
backward direction is direction reverse to forward direction. After cutting of the
said thread (4) the cut thread is then disposed of in downward direction in to the
waste collection box (12). Thus, we are able to automate the excessive thread
removal operation.
In another embodiment, the cuts in the loose stitching thread (4) are made
simultaneously or one after another.
According to the invention a method of making more than one cuts in the loose
stitching thread between the consecutive bags on a bag making line is disclosed
wherein a step is introduced of making two cuts in the thread that connects any
two consecutive bags.
In one embodiment the movable element is in the form of a rotary blade. In
another embodiment, instead of two elements (fixed and movable) the cutting
devices have a single element such as a sharp linear blade or a rotary blade.
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It is evident that the present invention comprises the following embodiments.
1. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line characterised in that said apparatus has a
dual cutter mechanism to make at least two cuts in the thread connecting
said two consecutive bags.
2. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiment 1
characterised in that said dual cutter mechanism has at least two cutting
devices, a guiding plate, at least one actuation mechanism, a mounting
plate, and a disposing unit, and a sensor, wherein said guiding plate guides
the incoming bags in forward direction, said bags being sensed for their
position by said sensor, said actuation mechanism actuates said cutting
devices once said bags are positioned at a predetermined position, said
mounting plate is provided to facilitate mounting of said two cutting
devices.
3. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 and 2,
characterised in that said cutting devices together make said more than
one cut simultaneously or sequentially.
4. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 3,
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characterised in that said cutting devices are governed using a single
actuation mechanism.
5. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 4,
characterised in that said single actuation mechanism receives a signal
from a central controller to activate said cutting devices.
6. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 5,
characterised in that each of said cutting devices are operated using
separate actuation mechanisms.
7. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 6,
characterised in that said cutting devices comprise replaceable blades.
8. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 7,
characterised in that said cutting devices operate in synchronous mode.
9. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 8,
characterised in that at least one of said cutting devices comprise a fixed
element and a movable element, said movable element being a sharp
blade, wherein once the thread to be cut is positioned over said fixed
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element, said movable element moved such that said thread is cut due to
shearing action between the fixed and movable elements.
10. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 9,
characterised in that said movable element is a rotary blade, which
applies cutting action on said thread through a rotary motion.
11. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 10,
characterised in that said cutting devices are operated mechanically,
electro-pneumatically or electronically.
12. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 11,
characterised in that said cutting devices are adjustably mounted on said
mounting plate.
13. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 12,
characterised in that said apparatus has a disposal unit for disposing of
the cut thread.
14. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiments 1 to 12,
characterised in that said fixed and movable elements are
interchangeable in position.
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15. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiment 8,
characterised in that said cutting devices have only a single element
which is in the form of a sharp linear blade or a rotary blade.
16. A method of cutting stitching thread joining two consecutive bags
processed on a bag making line characterised in that said method
comprises the step of making more than one cut in the thread connecting
two consecutive bags after the seaming operation using more than one
cutting devices.
17. A method of cutting stitching thread joining two consecutive bags
processed on a bag making line as disclosed in embodiment 16
characterised in that said method is carried out on an apparatus disclosed
in any one of the embodiments 1 to 15.
While the above description contains much specificity, these should not be
construed as limitation in the scope of the invention, but rather as an
exemplification of the preferred embodiments thereof. It must be realized that
modifications and variations are possible based on the disclosure given above
without departing from the spirit and scope of the invention. Accordingly, the
scope of the invention should be determined not by the embodiments illustrated,
but by the appended claims and their legal equivalents.

We claim:
1. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line characterised in that said apparatus has a
dual cutter mechanism to make at least two cuts in the undesirable length
of thread connecting said two consecutive bags.
2. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claim 1 characterised in
that said dual cutter mechanism has at least two cutting devices, a guiding
plate, at least one actuation mechanism, a mounting plate, and a disposing
unit, and a sensor, wherein said guiding plate guides the incoming bags in
forward direction, said bags being sensed for their position by said sensor,
said actuation mechanism actuates said cutting devices once said bags are
positioned at a predetermined position, said mounting plate is provided to
facilitate mounting of said two cutting devices.
3. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 and 2,
characterised in that said cutting devices together make said more than
one cut simultaneously or sequentially.
4. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 3, characterised
in that said cutting devices are governed using a single actuation
mechanism.
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5. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claim 1 to 4, characterised
in that said single actuation mechanism receives a signal from a central
controller to activate said cutting devices.
6. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 5, characterised
in that each of said cutting devices are operated using separate actuation
mechanisms.
7. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 6, characterised
in that said cutting devices comprise replaceable blades.
8. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 7, characterised
in that said cutting devices operate in synchronous mode.
9. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 8, characterised
in that at least one of said cutting devices comprise a fixed element and a
movable element, said movable element being a sharp blade, wherein once
the thread to be cut is positioned over said fixed element, said movable
element moved such that said thread is cut due to shearing action between
the fixed and movable elements.
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10. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 9, characterised
in that said movable element is a rotary blade, which applies cutting
action on said thread through a rotary motion.
11. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 10,
characterised in that said cutting devices are operated mechanically,
electro-pneumatically or electronically.
12. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 11,
characterised in that said cutting devices are adjustably mounted on said
mounting plate.
13. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 12,
characterised in that said apparatus has a disposal unit for disposing of
the cut thread.
14. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claims 1 to 13,
characterised in that said fixed and movable elements are
interchangeable in position.
15. An apparatus for cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claim 8, characterised in
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that said cutting devices have only a single element which is in the form
of a sharp linear blade or a rotary blade.
16. A method of cutting stitching thread joining two consecutive bags
processed on a bag making line characterised in that said method
comprises the step of making more than one cut in the thread connecting
two consecutive bags after the seaming operation using more than one
cutting devices.
17. A method of cutting stitching thread joining two consecutive bags
processed on a bag making line as claimed in claim 16 characterised in
that said method is carried out on an apparatus claimed in any one of the
claims 1 to 15.