FIELD OF THE INVENTION
Device of the invention relates to weaving machines, containing warp and weft
yarns/tapes for fabric weaving on circular weaving machines, more precisely,
sensing end of warp yarn/tape during fabric production.
5
BACKGROUND INFORMATION
The circular weaving loom or machine (CWM) is designed to weave endless
tubular or flat fabric using PP, HDPE, LLDPE yarn/tape or other blends of
polyolefin (Figure1).
10
The warp yarns/tapes are fed to the weaving machine from more than one creel
via rollers. This ensures uniform warp tension, excellent fabric quality, and
trouble-free handling (Figures 2 & 3).
15 In conventional looms, six or more shuttles running on a reed ring are provided
for carrying the weft bobbins. During the fabric production, warp bobbins can be
changed easily and quickly without shutting down the CWM. This is done by
tying into a knot the two ends – one end being that of the exhausted bobbin and
the other being that of the fresh yarn. Therefore, when yarn/tape on a bobbin is
20 coming to end, the bobbin needs replacement with a new bobbin. If this is not
done within stipulated time, the warp yarn/tape on the bobbin becomes loose as
tension drops due to continuity break. As this is done under observation of the
operator, this whole operation is dependent on operator skill and prone to operator
3
error. Furthermore, the loose yarn/tape may possibly entangle with other nearby
yarns/tapes coming from adjacent bobbins thereby damaging section of the
running fabric. Thus, one of the drawbacks of the existing systems is its
requirement to regularly monitor bobbin exhaustion by operator. Similarly,
another drawback of the existing systems is that when the 5 ends of the warp are
noticed, the machine needs to be stopped immediately such that the ends of the
warp tapes are not allowed to reach reed ring section of the weaving machine.
One of the popular methods to sense yarn ends incorporates the use of a drop wire
10 (Figures 4A and 4B). Drop wire systems consist of a gravity-controlled ‘drop
wire’ made of metals such as stainless steel through which the tape used for fabric
making passes. When warp yarn/tape ends, yarn/tape loses it tension which causes
it to slag causing drop wire to fall down. In this case, operator observes slag in
yarn/tape and stops the machine to change the empty or semi filled tube with new
15 bobbin.
There are certain limitations of this system which are of practical significance.
First, in running machine operator would require to keep monitoring for any warp
end, which is very difficult when number of machines operated by operator is
20 more than one or operator loses his attention in between. Second, when number of
warp bobbins getting empty is higher, in that case observing all of them is
difficult, meanwhile running machine produces waste fabric which cannot be used
further.
4
Nowadays, there is growing trend of filler addition to polyolefin tapes. The filler
content tends to generate powdery dust particulates during fabric weaving
operation. These dust particles settle on any available surface in the vicinity of the
loom. The settled dust has the potential to disrupt the electronic/5 electrical sensor
functioning, hampering the loom operations. There are yarn end detection systems
that are automated and use electric circuits. However, it has been found that these
systems are susceptible to frequent malfunctioning, especially in the dusty
environs.
10
There is therefore a need to provide an improved drop wire and a system to detect
yarn end and provide a notification of it to the operator, which will work
unhampered even in dusty environment.
15 OBJECTS OF THE INVENTION
Accordingly, one of the objects of the present invention is to provide an
automated system for sensing warp end.
Another object of the invention is to provide an automated system for detecting
20 warp end which will work robustly in dusty environment.
A further object of the invention is to provide an improved drop wire for the
purpose of detection of warp end.
5
Another object of the present invention is to provide a system that reduces the
wastage of weaved fabric and machine downtime.
SUMMARY 5 OF THE INVENTION
The invention discloses an improved drop wire and a device to detect the end of a
running yarn on a CWM used to make endless tubular fabric. The device of the
invention also discloses an electric circuit which is kept open during normal
10 working of the loom – that is when all yarns are running unbroken. The device is
so designed that upon detection of a yarn end (due to yarn breakage or due to the
yarn package running out of yarn) by a yarn detection means that is also a part of
the device, the electric circuit is completed and a notification is sent to the loom
operator. The invention is particularly suitable in dusty environment in which
15 CWMs typically operate.
The invention utilizes an improved drop wire (6) which maintains its normal
operating position by hanging by the running yarn that passes through a loop
provided at one end of the drop wire. The drop wire is provided with an
20 electrically conducting first element having a spatially curved external surface.
Breakage of the running yarn causes loss of tension in the yarn, causing the drop
wire to lose its elevation rapidly. The device of the invention also incorporates a
set of electrically conducting second elements having a curved internal surface.
Upon the loss of elevation, the first and second elements come in electrical
6
contact with each other, thereby completing an electric circuit and consequently
causing a signal to be sent to the operator of the loom indicating yarn breakage.
Drop wires (6) are provided on every individual warp yarn/tape which is fed to
the central reed ring section.
5
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows a schematic of loom used to manufacture woven fabric
Figure 2 shows a schematic of warp yarn/tape travel path in a loom
10 Figure 3 shows woven fabric and a tube form of it
Figure 4A and 4B show the open circuit and closed circuit positions, respectively,
of the typical drop-wire type device of the prior art
Figures 5A and 5B show the configuration of second elements
Figure 6A shows the drop wire with first element
15 Figures 6B, 6C, and 6D show second elements along with configuration of inner
surfaces
Figure 7 shows details of the inner surfaces of a second element
List of parts:
Creel Bracket (1)
Inlet Motor (2)
Outer Surface (6C)
Second elements (7)
Roller (3) Physical gap (7A)
Woven fabric (4) Inner Curved shaped surface (7B)
Bobbin (5) Single surface (7C)
7
Drop wire (6)
Loop (6A)
First element (6B)
Electronic Circuit (8)
Sub-surface (7D)
Point (7E)
Edge (7F)
Yarn (9)
DETAILED DESCRIPTION OF THE INVENTION
Woven fabric for use in making bags for storing materials such as grains, cement,
etc. is made from yarn/tape of PP, HDPE, LLDPE or other blends of polyolefin.
As shown in Figure 1, a circular weaving machine/loom 5 (CWMs) that makes
tubular fabric for making such bags deploys a number of bobbins. Figure 2 shows
the typical yarn travel path in a CWM. As discussed earlier, for a number of
reasons, yarn gets broken during the loom operation. The device disclosed in the
invention allows detection of ends of a broken yarn/tape so that the CWM may be
10 stopped in order and a signal is sent to the operator on duty to avoid entanglement
of the broken yarn/tape with other yarns/tapes operational on the CWM.
As disclosed in the summary section, the key purpose of the device of the
invention is to detect the breakage or end of a running yarn and inform the loom
15 operator of its occurrence. This is achieved by providing the following three key
elements in the device: a means to detect the yarn breakage, an electric circuit,
and a notification means.
8
It also should be noted that the CWMs operate in an environment where a
substantial amount of particulate matter (dust) is generated as a result of loom
operation. These particles settle on any available surface in the vicinity of the
loom. The settled dust which is electrically non-conductive has the potential to
hamper the loom operations. In the case of systems to detect 5 yarn ends, where
electric circuits are employed, the smooth working of such circuits may be
hampered by such dust. One of the key aspects of the device of the invention is
that it works effectively regardless of the dusty environments within which they
are deployed.
10
The present invention discloses a device for sensing end of warp yarn or tapes on
an automated fabric weaving loom and notifying the instance of yarn breakage to
the operator. It comprises a yarn end detection means to detect the breakage of or
a slack in running yarn, an electric circuit, and a notification means to notify
15 breakage of or slack in yarn.
In one aspect of the invention, the yarn end detection means comprises an
improved weighted drop wire (6) (Figures 4A and 6A) with an eye (6A) at its one
end through which the running warp yarn/tape (9) passes, and which is held in
20 substantially upheld position by the tension in the running yarn (9). An
electrically conducting first element (6B) is attached fixedly to the drop at a
predetermined distance 'h' (Figure 4A) from the eye (6A).
9
During the operation of the loom, if a yarn (9) breaks, the specific drop wire (6)
that was supported by the yarn (9), before its breaking, drops (Figure 4B) from its
previously upheld position. It should be noted that during the normal operations
of a loom, the drop wire (6) moves vertically, in small amounts, from its normal
operating position. This is due to irregularity in the package's 5 winding quality,
leading to variation in the yarn tension. However, such vertical positional
variation is normal and not unexpected. Whenever there's such accepted type of
positional variation, the drop wire (6) regains its normal working position in a
matter of fraction of seconds.
10
In the instance of an actual breakage (or indeed when a package comes to an end,
thereby running out of yarn), the drop of the drop wire (6) from its normal
operating position is substantial and irrecoverable. The drop wire (6) drops
vertically by a substantial distance from its normal operating position on
15 substantial loss of tension in the running yarn (6) – sensing of the irrecoverable
drop of the drop wire (6) represents yarn end detection. A pair of electrically
conducting second elements (7) (see Figures 5A/5B) is provided as a part of the
electric circuit that is referred to earlier. Upon the detection of a yarn breakage, as
the specific drop wire (6) drops (Figure 4B), it brings the first element (6B) in
20 electrical contact with corresponding second elements (7), thereby closing the
electric switch/loop and consequently completing the electric circuit (Figure 5B).
10
As also shown in Figures 5A and 5B, in another aspect of the invention, the
components of the electric circuit are the first elements (6B), second elements (7),
an electronic circuit (8) that electrically connects two second elements (7) of any
pair of the second elements (7) at one end of the second elements (7), and a
source of electric power. It further comprises an electric switch 5 or a loop that is
yarn-dust-proof. During the normal working operation of the loom, the electric
switch/loop remains 'open'. The device is so designed that upon detection of a
yarn breakage or a yarn end, the electric switch/loop closes effectively thereby
completing the electric circuit – regardless of the presence of dusty environment.
10 Upon closure of the electric circuit, an alarm is raised and a signal is sent to the
operator indicating the yarn breakage.
As discussed earlier, the drop wire (6) supports a first element that has an
electrically conducting outer surface (6C). The outer surface (6C) of the first
15 element (6B) is spatially curved (Figure 6A), preferably substantially in the form
of a cone of any type. The outer surface (6C) may have serrations that run
substantially longitudinally. The yarn-dust-proof electric switch/loop comprises a
pair of electrically conducting second elements (7). As shown in Figures 6B and
6C, the second elements (7) are provided with inner curved shaped surfaces (also
20 termed as inner surfaces or inner shaped surfaces) (7B) with a shape that
corresponds to the outer surface (6C) of the first elements (6B).
11
The term 'corresponds' mentioned above refers to the correspondence between the
outer surface (6C) of the first element (6B) and the shaped inner surface (7B) of
the second element (7), and is to be understood in the context of electrical
connection. The outer surface (6C) of the first element (6B) and the
corresponding inner surface (7B or 7C) on the second element 5 do not have to be
'exactly matching' – that is they do not need to be in full contact with each other.
By correspondence it is meant that there simply needs to be sufficient contact so
that the electric switch/loop is closed effectively.
10 It is known that the dust tends to settle on surfaces that are, among other
characteristics, devoid of geometric features such as points and sharp edges. In the
view of this, in one aspect of the invention, the inner surfaces (7B) of the second
elements (7) are provided with points and/or sharp edges. Some of these are
illustrated in Figure 7.
15
As shown in Figures 5A and 5B, in one embodiment of the invention, the second
elements (7) are in the form of a strip or a plate on which are provided the inner
curved shaped surfaces (7B). When positioned across from each other, these
plates, with the inner curved shaped surfaces (7B) facing the inner curved shaped
20 surfaces (7B) of the other second element (7) from the pair of second elements,
they form receptors into which the first elements (6B) fall when the drop wire (6)
loses its elevation substantially. As can be seen from Figure 5, there is a physical
gap (7A) between the two shaped edges that face each other. It is this gap (7A)
12
that keeps the electric switch/loop in an open state during the normal working
condition of the loom. At the same time, the gap (7A) is so designed that the drop
wire (6) passes through it in its normal working position without closing the
electric loop.
5
The curve of the outer surface (6C) of the first element (6B) may of any shape,
however it should be such that when the drop wire (6) drops from its normal
working position, the first element (6B)—owing to the curvature of its outer
surface (6C)—goes into the gap (7A) between the inner shaped curved surfaces
10 (7B) of the two parts of the second elements (7) easily. The curvature of the outer
surface (6C) should be of such shape that upon resumption of the tension in the
yarn, when the drop wire (6) is pulled up back to its own normal working position
due to the tension in the yarn, this upward movement of the drop wire (6) is
carried out unhindered.
15
The inner curved shaped surfaces (7B) of the second elements (7) may be made of
a single surface (7C) (Figure 6D) or multiple sub-surfaces (7D) (Figures 6B/6C).
In the case there are multiple sub-surfaces (7D), the junctions between any two
sub-surfaces (7D) are preferably in the form of a point (7E) or an edge (7F) (see
20 Figure 7) that is preferably sharp.
Formation of points or sharp edges (7E and/or 7F) is important in order to not
allow dust to settle on at least some part of the curved shaped inner surfaces (7B).
13
This is of crucial importance as it allows an effective electric contact to be
established with ease between at least some parts of the curved outer surface (6C)
of the first element (6B) and the inner curved shaped surface (7B) of the second
elements (7) at any time when the drop wire (6) has fallen from its normal
5 operating position.
The vertical distance 'h' (Figure 4A) at which the first element (6B) is located
from the running yarn (9) that supports a particular drop wire (6) depends on the
overall configuration of the system of yarns. The distance should be such that
10 upon yarn breakage detection, the circuit is closed within a reasonably short time
period. The distance should also be such that there is no false alarm raised in
situations where there is temporary loss of tension. However, there may be
exceptional circumstances, where the loss of tension is due to abnormal or
unexpected slack in an unbroken running yarn, where the drop wire (6) may drop
15 sufficiently so that the circuit closes.
One feature of the present invention is its ability to distinguish between temporary
slack in the warp and permanent breakage in the yarn/tape (9). In the experience
of the inventor, in the situations where such exceptional situations occur, the yarn
20 (9) resumes its normal operation once the slack is eliminated by the ongoing
movement of the yarn (9). This may take a duration as small as 0.1 seconds and
up to 2 seconds. Under such circumstances, it would be undesirable if the CWM
14
shuts down simply because there was a circuit closure (which is typically
indicative of yarn end detection).
In order to overcome such exceptional but potentially real problems, the device is
provided with time monitoring facility. Time from any given closure 5 of circuit is
monitored and noted. In the case where there's no opening up of the circuit
following from a circuit closure event within a predetermined period, it is
indicative of a situation involving a yarn end or other undesirable event that
suggests that it would be potentially harmful to allow the CWM to continue
10 operation without intervention. In such situation the CWM is made to shut down
and a notification signal is sent. The signal may be sent to a monitor. In the case
where there's opening of the circuit within the predetermined period, no
notification would be sent, however, the CWM will be permitted to continue
operation.
15
In this manner, the inbuilt intelligent module eliminates possibility of any faulty
alarm generation for temporary loosening in yarn/tape (9), and more importantly
the consequent shutting down of the CWM. Temporary slack of warp yarn/tape
(9) is very common in weaving machines which on account of false alarms
20 consumes significant amount of resources in terms of time and manpower
utilization as machine get down for this time period, which is always desirable to
avoid under any circumstances.
15
It is evident from the foregoing discussion that the present invention has a number
of embodiments.
1. A device for sensing end of warp yarn or tape on an fabric weaving loom,
said device comprises a yarn-end detection means to detect 5 the breakage of
or end in said running yarn, an electric circuit of which said yarn detection
means form a part, and a notification means to notify breakage of or end of
yarn, characterised in that
10 said yarn-end detection means comprising a first elemental having an
electrically conducting outer surface said first element being fitted on a
drop wire that has an opening for passage of said warp yarn, said drop wire
being held in its normal operating position due to tension in said running
yarn warp, and a pair of second elements each said second element having
15 an electrically conducting inner surface, there being present a physical gap
between said second elements,
wherein, subsequent to the falling of said drop wire from its normal
operating position due to substantial loss of tension in said warp, said
20 electrical circuit/switch gets completed by said electrically conducting
surfaces of first and second element coming in contact with each other,
thereby triggering the notification means for a notification signal
generation of yarn/tape break or end.
16
2. A device as disclosed in embodiment 1, characterized in that said
electrically conducting outer surface is spatially curved, and said internal
surface carrying a dust-repelling geometrical shape.
3. A device as disclosed in embodiments 1 or 2, characterised in that said
notification signal is an audio or a visual or audio-visual signal, 5 or a signal
indicating apparatus failure sent to a monitor.
4. A device as disclosed in embodiments 1 to 3, characterised in that said
first element has a substantially conical outer surface.
5. A device as disclosed in any of embodiments 1 to 4, characterised in that
10 said inner curved surface being provided with a shape corresponding to
that of said outer surface of said first elements.
6. A device as disclosed in any of embodiments 1 to 5, characterised in that
one detection means is provided for each of the running yarn that is being
weaved on the weaving machine.
15 7. A device as disclosed in any of embodiment 1 to 6, characterised in that
said apparatus is capable of detection of at least one broken yarn.
8. A as disclosed in any of embodiments 1 to 7, characterised in that said
notification indicating yarn breakage identifies specific yarn which has
broken.
20 9. A device disclosed in any of embodiments 1 to 8, characterised in that said
notification is sent only in the event that said electric circuit remains
closed for more than a predetermined time period.
17
10. A device disclosed in any of embodiments 1 to 9, characterised in that
said predetermined period is in the range between 0.1 to 2 seconds.
11. A device disclosed in any of embodiments 1 to 10, characterised in that
said the two second elements from any given pair of second elements are
electrically connected at one end of respective second 5 elements and at
their other ends they are connected to a source of electric current.
12. A device disclosed in any of embodiments 1 to 11, characterised in that
said inner curved surface has a number of sub-surfaces, and wherein the
interfaces between said sub-surfaces being edges or points.
10 13. A device disclosed in any of embodiments 1 to 12, characterised in that
said edges being sharp.
14. A method for sensing end of warp yarn (9) or tape on a circular weaving
loom, characterized in that said method comprises the steps of
- providing a device as disclosed in any one of embodiments 1 to 13,
15 - detecting a yarn end,
- upon substantial loss of elevation of any drop wire (6), completing
electrical circuit/switch,
- sending a notification signal indicating detection of a yarn end or a
yarn break,
20 - stopping the working of said circular weaving loom.
While the above description contains much specificity, these should not be
construed as limitation in the scope of the invention, but rather as an
18
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 5 legal equivalents.

We claim:
1. A device for sensing end of warp yarn (9) or tape on a fabric weaving
loom, said device comprises a yarn-end detection means to detect the
breakage of or end in said running yarn, an electric circuit of which said
yarn detection means form a part, and a notification 5 means to notify
breakage of or end of yarn, characterised in that
said yarn-end detection means comprising a first element (6B) having an
electrically conducting outer surface (6C) said first element (6B) being
10 fitted on a drop wire (6) that is provided corresponding to each individual
yarn, said drop wire (6) has an opening (6A) for passage of said warp yarn
(9), said drop wire (6) being held in its normal operating position due to
tension in said running yarn warp, and a pair of second elements (7)
provided corresponding to a group of said drop wires (6), each said second
15 element (7) having an electrically conducting inner curved shaped surface
(7B) corresponding to each said drop wire (6), there being present a
physical gap (7A) between said second elements (7),
wherein, subsequent to the falling of said drop wire (6) from its normal
20 operating position due to substantial loss of tension in said warp yarn (9),
said electrical circuit/switch gets completed by said electrically conducting
surfaces (6C and 7B) of first and second elements (6B and 7) coming in
20
contact with each other, thereby triggering the notification means for a
notification signal generation of yarn/tape break or end.
2. A device as claimed in claim 1, characterized in that said electrically
conducting outer surface (6C) is spatially curved, and said inner curved
shaped surface (7B) having a dust-repelling 5 geometrical shape.
3. A device as claimed in claims 1 or 2, characterised in that said notification
signal is an audio or a visual or audio-visual signal, or a signal indicating
apparatus failure sent to a monitor.
4. A device as claimed in any of claims 1 to 3, characterised in that said outer
10 surface (6C) is substantially conical.
5. A device as claimed in any of claims 1 to 4, characterised in that said inner
curved shaped surface (7B) is provided with a shape corresponding to that
of said outer surfaces (6C).
6. A device as claimed in any of claims 1 to 5, characterised in that one yarn15
end detection means is provided for each of the running yarn (9) that is
being weaved on the weaving machine.
7. A device as claimed in any of claims 1 to 6, characterised in that said
device is capable of detection of at least one broken yarn.
8. A device as claimed in any of claims 1 to 7, characterised in that said
20 notification indicating yarn breakage identifies specific yarn (9) which has
broken.
21
9. A device as claimed in any of claims 1 to 8, characterised in that said
notification is sent only in the event that said electric circuit remains
closed for more than a predetermined time period.
10. A device as claimed in any of claims 1 to 9, characterised in that said
predetermined period is in the range between 5 0.1 to 2 second.
11. A device as claimed in any of claims 1 to 10, characterised in that said the
two second elements (7) from any given pair of second elements are
electrically connected at one end of respective second elements and at
their other ends they are connected to a source of electric current.
10 12. A device as claimed in any of claims 1 to 11, characterised in that said
inner curved shaped surface (7B) has a number of sub-surfaces (7D), and
wherein the interfaces between individual said sub-surfaces (7D) are edges
or points.
13. A device as claimed in any of claims 1 to 12, characterised in that said
15 edges being sharp.
14. A method for sensing end of warp yarn (9) or tape on a circular weaving
loom, characterized in that said method comprises the steps of
- providing a device as claimed in any one of claims 1 to 13,
- detecting a yarn end,
20 - upon substantial loss of elevation of any drop wire (6), completing
electrical circuit/switch,
- sending a notification signal indicating detection of a yarn end or a
yarn break,
22
- stopping the working of said circular weaving loom.