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Manufacture Of Cotton Yarn






=Picker Room.= The first step in the conversion of the bale of cotton
into yarn consists in giving the cotton fibers a thorough cleaning.
This is accomplished by feeding the cotton to a series of picker
machines called in order, bale breaker, cotton opener and automatic
feeder, breaker picker, intermediate picker, and finisher picker.
These machines pull to shreds the matted locks and wads of cotton (as
we find them in the bale), beat out the dirt, stones, and seeds, and
finally leave the cotton in the form of batting upon the cylinders;
this batting passes from one machine to another until it issues from
the finisher picker as a downy roll or lap.

(Sometimes the bale breaker is not used in the mill.)

=Carding Machine.= When the lap of cotton leaves the picker it goes to
the carding machine, where it is combed into parallel fibers by means
of a revolving cylinder covered with wire teeth called card clothing.
As the cotton is fed to the card in the form of a sheet or lap from
the picker, it is supposed to have been freed from a considerable
quantity of sand, seed, etc., but there still remain nep, fine leaf,
and short fibers, which are removed during carding.

On leaving the card cylinder the lap has become a gossamer-like web
thirty-nine inches broad. This web next passes through small "eyes,"
which condense it into a narrow band about an inch in width, known as
card sliver.

When a lap is delivered from the finisher picker, it should weigh a
given number of ounces per yard. The method of ascertaining the weight
is to make each lap a standard number of yards in length and weigh
each lap. The machine can be regulated so as to give the desired
weight per yard.

=Combing.= When an extremely fine and strong yarn is required, in
addition to carding, the fibers are also subjected to the process of
"combing." This may be said to be merely a continuation of the carding
process to a more perfect degree. The chief object is to extract all
fibers below a certain required length, and cast them aside as
"waste." This is done in order to secure the very best fibers
calculated to give the strongest and best results in the spun yarn.

The process of combing follows carding. The card delivers the cotton
in the form of a sliver or strand, while the combing machine requires
the fibers to be delivered to it in the form of sheets, nine to twelve
inches wide. This is done by taking a number of card slivers and
forming a lap of them by passing the sliver through a sliver lap
machine. The laps are passed through the comber. This machine consists
essentially of a series of rollers, nippers, and rows of metal teeth.
By the action of these, the short fibers are separated and combed out,
and the long ones arranged in parallel order in the form of a thin,
silky strand, in which condition it is sent to the drawing frames to
be drawn out. Of course it must be understood that a combing machine
is used by only a small percentage of cotton spinners. For ordinary
purposes a sufficiently good quality can be made without a comber. As
there is from 15 to 35 per cent waste to this operation it may be
readily seen that it is costly, and limited entirely to the production
of the very best and finest yarns, such as those intended for sewing
or machine thread, fine hosiery, lace curtains, underwear, imitation
silks, and fine grades of white goods. There are combing machines that
comb short staple cotton.

=Drawing.= The cans containing the slivers are taken from the card or
combing machine (as the case may be) to the drawing frame. The object
of this machine is mainly to equalize the slivers, combining a number
of them together so as to distribute the fibers uniformly. The
condition of the fibers on leaving the card or comb is such that a
slight pull will lay them perfectly straight or parallel, and this
pull is given by the drawing frame rollers. Of course the fibers
coming from the comb are parallel, but it is necessary to alternate
them by the drawing. The drawing frame is a machine consisting of a
number of sets of rollers, the front roller having a greater speed
than the rear ones.

The slivers, which are as nearly as possible the same weight per
yard, are combined together in the drawing and emerge from the pair of
front rollers as one sliver weighing the same number of grains per
yard as a single sliver fed up at the back. This process is repeated
two or three times, according to requirements, the material then being
referred to as having passed through so many "heads" of drawing. It is
not unusual to pass Indian and American cotton through three
deliveries.

The object of all the processes thus far described has been that of
cleaning (in the picker), arranging the fibers in a parallel position
to each other, making uniform, and drawing out the stock. In every
case the stock delivered from a machine is lighter than when fed into
it, and contains just twist enough to hold it together and prevent its
being stretched or strained when unwound from the bobbin, and fed into
the next machine. The minimum amount of twist in roving is desirable
for the reason that it permits the stock to be drawn out more easily
and uniformly, the little twist that is put in the roving by the
slubber being practically eliminated when it is passed through the
rolls of the intermediate. The same applies in the case of the roving
passing from the roving to the spinning frame.

=Fly Frames.= The process in the manufacture of yarn after the cotton
has passed through the drawing frame consists of further attenuation
of the sliver, but as the cotton sliver has been drawn out as much as
is possible without breakage, a small amount of "twist" is introduced
to allow of the continued drawing out of the sliver.

From the drawing frame, the drawing passes through two, three, or four
fly frames, according to the number of yarn to be made. All these
machines are identical in principle and construction, and differ only
in the size of some of the working parts. They are the slubber,
intermediate, roving,--and fine or jack frame-fine, and the function
of each is to draw and twist.

=Intermediate Frame.= The function of the intermediate frame is to
receive the slightly twisted rove from the slubber and add thereto a
little more twist and draft. The rove is taken from two bobbins to
one spindle in the machine, an arrangement which tends to insure
strength and uniformity. The principle of the machine is in other
respects the same as that of the slubbing frame.

=Roving Frame.= The function of the roving frame is to receive the
twisted rove from the intermediate and add more twist and draft,
thereby further attenuating the rove. As in the intermediate frame the
rove is generally taken from two bobbins for one spindle.

=Fine or Jack Frame.= This machine is used when fine yarns have to be
made. It is built on the same principle as the preceding frames, the
only difference being that a finer rove is made from which finer
numbers of yarn can be spun. As in the slubber, intermediate, and
roving frames, the rove is taken from two bobbins for one spindle.

=Spinning.= In the manufacture of single ply yarn the final process is
that of spinning, which consists in drawing out the cotton roving to
the required size, and giving it the proper amount of twist necessary
to make the yarn of the required strength. While the spinning frame is
built on entirely different principles from the roving, intermediate,
or slubber frame, the object of each machine is the same as that of
the spinning frame. The principal point of difference is the amount of
twist imparted to the cotton roving.

The objects of the spinning process are:

1. Completion of the drawing out of the cotton roving to the required
size.

2. Insertion of the proper amount of twist to give the thread
produced strength.

Excessive speed causes defects in the yarn and undue wear and tear on
the machine.

There are two methods of spinning: ring spinning and mule spinning.
The mule spinning is the older form. There are but few mule frames in
operation in this country.

=Mule Spinning.= The function of mule spinning is to spin on the bare
spindle, or upon the short paper tubes, when such are required to form
a base for the cop bottom. The mule will spin any counts of yarn
required, and is especially adapted for yarn in which elasticity and
"cover" are essentials. Hosiery yarns are produced on the ordinary
cotton mule and are very soft spun.

The bobbins of roving are placed in a creel at the back of the
machine, the stands of roving being passed through the rolls and drawn
out in the same manner as at the roving frame. The spindles are
mounted on a carriage which moves backward and forward in its relation
to the rolls, the distance roved being about five feet. When the
spindles are moving away from the frame the stock is being delivered
by the rolls, the speed at which the spindles move away from the rolls
being just enough to keep the ends at a slight tension. The twist is
put in the yarn at the same time.

When the spindles reach their greatest distance from the rolls, the
latter are automatically stopped and the direction of the motion of
the spindle carriage reversed. The yarn is wound on the spindle while
the carriage is being moved back toward the rolls, the motion of the
rolls being stopped in the meanwhile, the spindles revolving only fast
enough to wind up the thread that has been spun during the outward
move of the carriage.

The mule is a much more complicated machine than the ring frame, its
floor space is much greater, and more skilled help is required for its
operation. Under ordinary conditions it is not practical to spin finer
yarn than No. 60s on a ring, while as high as No. 500s is said to have
been spun on a mule. The same number of yarn can be spun on a mule
with less twist than on the ring. This is important in hosiery yarn.

Ring spinning is used for coarse numbers, and has greater production
and requires less labor than mule spinning. Ring-spinning yarn is used
for warp purposes.

=Ring Spinning.= The function of ring spinning is to draw out the rove
and spin it into yarn on a continuous system. The yarn made is spun
upon bobbins.

The ring spinning differs from mule spinning in having the carriage
replaced by a ring, from which the machine takes its name. The ring is
from one and one-half to three inches in diameter, grooved inside and
out, and is connected with a flat steel wire shaped like the letter D,
called the "traveller." Its office is to constitute a drag upon the
yarn, by means of which the latter is wound upon a bobbin. Its size
and weight depend on the counts of yarns to be spun; coarse yarns
demand the largest ring and heaviest traveller.





Next: Thread And Cotton Finishing

Previous: Cotton



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