1) The document discusses stop devices used in looms to automatically stop operation if a warp or weft thread breaks, which could cause flaws. It describes common issues with early stop devices and objectives to improve them. 2) It provides details on different types of stop motions used for warp and weft threads, including piezoelectric and optical sensor mechanisms. Piezoelectric devices detect broken weft threads using crystals that produce electric charges. Optical sensors like photocells detect thread presence without touching the weft. 3) The document concludes that understanding stop devices is important for knowing how looms detect and respond to broken threads to prevent defects and wasted material.

1. GREEN UNIVERSITY OF BANGLADESH
Department Of Textile
ASSIGNMENT
Remarks:
Course Code : TE 302
Course Title : Fabric Manufacturing II
Submitted To:
Name : Ms. Suraiya Ireen
Designation : Lecturer
Department : Textile
Contact : suraiya@tex.green.edu.bd
Submitted By:
Name : Md Rakibul Hassan
ID : 183014057
Section : E1
Department : Textile
Date Of Performance : 07-08-2020
Date Of Submission : 17-08-2020
Assignment Topic : Stop Device

2. Assignment On Stop Device
Loom Stop Motions:
This invention relates to improvements in loom stop motions of the character used for
controlling the opera tion of looms for weaving cloth. In the weaving process, the
warp of the material is fed horizontally toward the front of the loom, being threaded
through harness frames that are suspended vertically, being supported and operated
by fine wires, or other flexible devices.
frames are used in side-by-side relation, and are raised and lowered alternately as the
shuttle passes through the warp to provide the desired pattern of weave of the material.
If one of the supporting wires for the harness frames should break, the frame connected
therewith would remain stationary, and this would result in a flaw in the material. It
has been proposed heretofore to stop the machine in the event of breakage of one of
the wires, but such stop devices as have been proposed, generally, have been complex
of structure, difficult to apply to the loom, and often fail to indicate which of the several
frames may be rendered inoperative. Since a loom usually contains a number of harness
frames, and the stoppage of the loom operation results in a loss to the owner through
inactivity of the loom, it is important for the weaver to be able to detect quickly and
readily the point where the breakage has occurred. One object of this invention is to
overcome the objections noted above and encountered heretofore in loom stop motions
to provide for the stoppage of the loom auto matically in the event of breakage of any
of the harness frame connections to prevent an imperfection in the cloth resulting
therefrom, which would be a loss to the mill.
Where the loom is provided with a knock-off box to control the shipper shaft, which in
turn controls the Y clutch and brake, the knock-off box may be used to con trol the
operation of the loom according to this invention, and used in connection with the
shipper shaft for that purpose. This embodiment of the invention is illustrated in the
accompanying drawings in which:

3. Fig. 1 is a diagrammatic view showing the side of the loom with the heddle frames and
their operating mechanism; and
Fig. 2 is a cross-section through the loom showing diagrammatically the travel of the
warp. The invention is shown as applied to a loom of conventional form, which is
illustrated only diagrammatically in the drawings and many parts thereof are omitted
for clearness of illustration since the construction of the loom forms no parts of this
invention. Only sufficient loom structure is shown to illustrate the application of the
invention thereto. The loom is shown as provided with a frame generally designated
by the numeral 1, for supporting the operat ing mechanism involved in weaving the
cloth. As showin Fig. 1, the warp threads are supplied from a warp beam 2 being
directed over a guide roll 3 through heddles in frames 4, over a lay 5 and cloth guide
6, to a cloth roll
Warp Stop Motion:
A mechanism used to stop a loom automatically if a warp thread breaks. If a thread
breaks, the vane drops and, by falling between the teeth of the racks, stops the motion
of the movable rack which causes the loom to shut down.
Warp Stop Motion Device:
Fig: Infrared Yarn Warp Stop Motion Device
Weft Stop Motion:
This motion enables to stop the loom immediately after a weft break or weft running
out. In case the loom is allowed to run even after the weft breaks there will be no woven
cloth except long threads of warp.

4. Types of weft stop motion:
In modern looms various types of weft stop motions are used:
1. Piezoelectric electronic weft stop
2. The optical sensors
Piezoelectric electronic weft stop:
In the case of rapier and projectile weaving machines, the mostly used device is
provided with piezoelectric crystals. These crystals have a double quality: if an electric
charge passes through them, they vibrate, or vice versa if they are made vibrate, they
produce a light electric charge.
This second property is used for the weft insertion control. This device, if it detects a
correctly inserted weft, produces a light electric charge. As this signal is too weak, it is
first amplified and then controlled against a sample signal: if the signal corresponds,
nothing happens.
Otherwise, the absence of the charge is interpreted as a broken weft and the weaving
machine stops. At this point the automatic pick finding device enters into action and
brings the machine back to the shed where the fault occurred. In this connection you
must consider that, although the stop signal is given quite quickly, a certain technical
time for stopping the loom is required. During this time, although the weft presenting
device is standing, the loom moves forward with some strokes which are compensated
recovering tension and space through the reverse running of the evener rollers.
Fig: Piezoelectric Electronic Weft Stop for Rapier Loom
The optical sensors:
In the case of fluid jet machines, it is preferable not to hinder the weft fly, therefore
optical sensors are used which do not touch the weft. As already mentioned, in the case
of the air-jet machines (at the moment only for them) there is a device which permits
to restore automatically the broken weft and to start the loom. This mechanism permits
to go on weaving if the problem takes place inside the shed. However, if defects take
place in the pre-winding drum or between this and the cone, it is appropriate to have
on board the machine the device which permits to select automatically the cone being
processed. This system enables to bypass the pre-winding drum which has problems
and to select a reserve drum which is standing until that moment. The machine does
not need long stops and the operator can intervene easily to remedy the problem.

5. Fig: Air Jet Weaving Machine
Should the same fault take place again on the new pre-winding drum, this will be
excluded in favor of the first drum.
The optical sensors are primarily infrared photocells suited to detect the presence of
the thread or the quantity of thread accumulated in a prefixed zone.An example of these
devices is the sensor for weft control on air-jet weaving machines, which is briefly
described in the following.
This device, which is designed to control the correct weft insertion into the shed of an
air jet loom, has the task of stopping the machine in case of incorrect insertion.
The sensor is placed on the shaped reed at the desired height in the zone of weft arrival;
it reads the presence of the thread when its front free end arrives in the sensor’s
measuring range and crosses it. The two photo-elements are opposing as schematically
indicated in Fig. 109 and constitute an optical barrier which is disturbed by the weft
thread when it is crossed by this thread.
Opto-electronic weft-stop motion:
In the case of air jet machines for staple yarn weaving, an opto-electronic weft stops
motion in twin arrangement can be delivered. While the first of the two weft stop
motions serves as support for the machine control, the second one records the weft
threads broken in the shed or expelled.

6. Fig: Opto-electronic weft stops motion
When the first one gets the weft, which means the weft thread has travelled the
predetermined distance, the loom remains running. And in case of the second one gets
the weft, which means the weft thread has broken and travelled excess than the
predetermined distance, it knocks-off the loom instantly.
Conclusion:
From this discussion we got to know about stop device and its working factor in warp
and weft motion in weaving loom.
Submitted by
Md Rakibul Hassan
Article collected from
https://textilelearner.blogspot.com/2011/06/modern-weft-stop-
motion-device-of-loom_7523.html
http://fabricclub.blogspot.com/2010/10/weft-stop-motion-
conventional-loom.html
https://patents.google.com/patent/US3911969A/en
https://scholar.google.com/