MANIPULATION OF COTTON IN OPENING, SCUTCHING, CARDING, DRAWING, AND
FLY-FRAME MACHINES.
Before attempting to give the readers of this story an insight into the
various operations through which cotton is made to pass, it may be
advisable to briefly enumerate them first.
On the field there are the operations of collecting and ginning, that
is, separating the raw cotton from the seeds. To the stranger it is very
astonishing that as many as 66 to 75 pounds of seed are got from every
100 pounds of seed cotton gathered. Then in or near the cotton field
the process of baling is carried out. Thus there are collecting, ginning
and baling, as preliminary processes.
When the cotton arrives in bales at the mill (see Fig. 10), in which it
is to be cleaned, opened and spun, it is first weighed and a record
kept.
In the mill the first real operation is the taking of quantities of
cotton from different bales of cotton from various countries, or
different grades from the same country, and "mixing" so as to secure a
greater uniformity in the quality of the yarn produced. In this process
it is now the common practice to use a machine termed the "Bale
Breaker," or "Cotton Puller."
The second important process carried out in the mill is "opening." By
this the matted masses of cotton fibres are to a great extent opened
out, and a large percentage of the heavy impurities, such as sand,
shell, and leaf, fall out by their own weight. It is now also usual at
this stage to form the cotton into a large roll or sheet called the
"lap."
Immediately following the "opening" comes "scutching," which is merely a
continuation of the work performed by the "opener," but done in such a
way that greater attention is bestowed upon the production of an even
sheet or "lap" of cotton.
The cotton at this stage is practically in the same condition as it was
when first gathered from the tree in the plantation.
=Carding= comes next in order, and it should be observed that this is one
of the most beautiful and instructive operations carried on in the
mill.
The process of opening out the cotton is continued in this operation to
such an extent that the fibres are practically _individually separated_,
and while in this condition very fine impurities are removed, and many
of the short and unripe fibres which are always more or less present are
removed. Before leaving the machine the fibres are gathered together
again in a most wonderful manner and converted into a "sliver," which
for all the world looks like a rope of cotton, a little less than an
inch in diameter.
In most mills "drawing" succeeds "carding," this operation having for
its object (1) the doubling together of four to eight slivers from the
card and attenuating them to the dimension of one so as to secure
greater uniformity in diameter. (2) The reduction of the crossed and
entangled fibres from the card into parallel or side by side order.
After "drawing," the cotton is brought to and sent through a series of
machines termed "Bobbin and Fly Frames." There are usually three of
these machines for the cotton to pass through, to which are given the
names of "Slubbing," "Intermediate," and "Roving" Frames.
Their duties are to carry on the operation of making the sliver of
cotton finer or thinner until it is ready for the final process of
spinning, and incidentally to add to the uniformity and cleanliness of
the thread of cotton.
The final process of spinning is chiefly performed on one of two
machines, the "Mule" and the "Ring Frame," either of which makes a
thread largely used without further treatment in a spinning mill.
Sometimes, however, the thread is further treated by such operations as
doubling, reeling, gassing, etc. It should be added that in the
production of the finest and best yarns an important process is gone
through, named "combing."
This may be defined as a continuation of the carding process already
named before to a much more perfect degree. The chief object is to
extract all fibres below a certain required length, and reject them as
waste. There is as much of this latter made at this stage of manufacture
as that made by all the other machines put together, that is, about 17
per cent. Of course it will be readily seen that this is a costly
operation and is limited entirely to the production of the very best and
finest yarns.
This process necessitates the employment of a machine called a "Sliver
Lap" and sometimes a "Ribbon Lap Machine" in order to put the slivers
from the carding engine into a small lap suitable for the "creel" of the
"Combing Machine."
=Cotton Mixing and the Bale Breaker.=--As before stated, the first
operation in the mill is the opening out of bales of raw material and
making a "mixing." Of course the weight of the bale is ascertained
before it is opened.
All varieties of cotton vary in their commercial properties, this
variation being due to a number of causes. From a commercial value point
of view, there is an enormous difference between the very best and the
very worst cottons; so much so, indeed, that they are never blended
together. Between these two extremes there is a well-graded number of
varieties and classifications of cotton, and some approximate so closely
to others in quality, that they are often blended together in the
"mixing."
Further than this, the same class of cotton often varies in spinning
qualities from a number of circumstances that need not here be named.
This is, however, an additional reason why cotton from various bales
should be blended together in order to secure uniformity.
A cotton "mixing" may be described as a kind of "stack," resembling
somewhat the haystack of the farm yards.
The method usually pursued in making this mixing is somewhat as
follows:--A portion of cotton from a certain bale is taken off and
spread over a given area of floor space. Then a similar portion from
another bale is placed over the first layer already lying on the floor.
The same operation is followed with a third and fourth layer from
different bales, and so on with as many bales as the management consider
there are variations in quality, the larger the mixing the better for
securing uniformity of yarn.
When it is desired to use the cotton, it should be pulled down
vertically from the face of the "mixing," so as to secure a fair portion
from each bale composing the mixture. Before spreading the cotton out it
is usually pulled into pieces of moderate size by the hands of the
operative.
During recent years it has become the very general practice to use a
small machine called the "Bale Breaker" or "Cotton Puller," and to have
also working in conjunction with this machine long travelling "lattices"
called "mixing lattices." These perform the operation of "pulling" and
"mixing" the cotton much more quickly and effectively than by hand
labour.
The "Cotton Puller" or "Bale Breaker" (see Fig. 12) simply consists, in
its most useful form, of four pairs of coarsely fluted or spiked
rollers of about 6 inches diameter with a feed apron or lattice such as
is shown in the illustration.
Image: FIG. 12.--Bale breaker or puller.
The method adopted with the "Bale Breaker" and "mixing lattices" in use
is as follows:--
The various bales of cotton intended for "mixing" are placed very near
to the feed apron of the Bale Breaker, and a layer from each bale in
succession is placed on the apron. The latter feeds the cotton at a slow
rate to the revolving rollers of the machine, and as each pair of top
and bottom rollers that the cotton meets is revolving more rapidly than
the preceding pair, the result is a pulling asunder of the cotton by the
rollers, into much smaller pieces, quite suitable for the next machine.
The Bale Breaker delivers the cotton upon long travelling aprons of
lattice work, which carry the cotton away and deposit it upon any
desired portion of the floor to form the "mixing."
=Opening.=--The name of the next process, viz., "opening," has been given
it because its primary function is "to open" out the cotton to such an
extent that the greater bulk of the seed, leaf, sand, and dust is
readily extracted. The details of this machine and indeed practically of
all machines used in cotton spinning, vary so much with different
makers, that it would be utterly out of place to deal with them here, so
that it may be said at once, that all such points are entirely omitted
from this treatment of the subject.
The essential and principal portions of the machines are practically
identical for all makers, and it is with these only that it is proposed
to deal, taking in all cases the best present-day practice.
The opener, then, is a very powerful machine, being in fact the most
powerful used in cotton spinning, and the most important feature of the
machine is the employment of a strong beater, to which is fitted a large
number of iron or steel knives or spikes. These beat down the cotton and
open it at a terrific rate, the beater having a surface speed of perhaps
4000 feet a minute. Various fans, rollers, and other parts are employed
to feed the cotton to the beater, and to take it away again after
treatment. It will perhaps best serve the purpose of our readers if the
passage of the cotton be described through an opener of the most modern
and approved construction, dealing with the subject in non-technical
terms.
With this object in view, take for example what is termed "The Double
Cotton Opener" with "Hopper Feed Attachment." This machine is shown in
Fig. 13.
Image: FIG. 13.--"Double opener" with "hopper feed."
The Hopper Feed is about the most recent improvement of any magnitude
generally adopted in cotton spinning mills. It is an attachment to the
initial or feed end of an opener with the object of feeding the cotton
more cheaply and effectively than it can be done by hand.
It may be said to consist of a large iron feed box, into which the
cotton is passed in considerable quantities at one time. At the bottom
of the feed box, or hopper, is a travelling apron which carries the
cotton forward, so as to be brought within the action of steel pins in
an inclined travelling apron or lattice. This latter carries the cotton
upwards, and special mechanism is provided in the shape of what is
termed an "Evener roller," to prevent too much cotton going forward at
once.
The cotton that passes over the top of the inclined lattice or apron is
stripped off by what is denominated the stripping roller, and is then
deposited on the feed apron of the opener, where formerly it was placed
by hand.
It may be said that one man can feed two machines with Hopper Feeds as
against one without them, and in the best makes the work is done more
effectively.
The feed lattice of the opener carries the cotton along to the feed
rollers, which project it forward into the path of the large beater. It
is here that the opening and cleaning actions are chiefly performed.
The strong knives or spikes of the beater break the cotton into very
small portions indeed, and dash it against "cleaning bars" or "grate
bars" specially arranged and constructed. Through the interstices of
these bars much of the now loosened seed and dirt present in the cotton
passes into a suitable receptacle, which is afterward cleaned out at
regular intervals.
The opened and cleaned cotton is taken away from the action of the
beater by an air current produced by a powerful fan. This latter creates
a partial vacuum in the beater chamber by blowing the air out of certain
air exit trunks specially provided. To supply this partial vacuum
afresh, air can only be obtained from the beater chamber, and the air
current thus induced, takes the cotton along with it, and deposits it in
the form of a sheet upon what are termed "cages" or "sieve cylinders."
These are hollow cylinders of iron or zinc perforated with a very large
number of small holes through which the air rushes, leaving the cotton,
as it were, plastered on the outer surfaces of the cages.
It is usual to have a pair of these cages, working one over the other
like the pair of rollers in a wringing machine.
The cotton now passes between two pairs of small guide rollers, and is
fed by the second pair to a second beater, but of very different
construction from the first one.
This consists of two or three iron or steel blades extending the full
width of the machine and carried by specially constructed arms from a
strong central shaft.
The edges of these beater blades are made somewhat sharp, and they
strike down the cotton from the feed roller at the rate of 2000 or more
blows per minute.
This of course carries the opening work of the cotton of the first
beater to a still further degree, and as in this case the cotton is also
struck down upon "beater bars" or cleaning bars, a further quantity of
loosened impurities passes through the bars. As before, another powerful
fan creates an air current by which the cotton is carried away from the
beater and placed upon a pair of "Cages." From this point the cotton is
conducted in the form of a sheet between four heavy calender or
compression rollers, the rollers being superimposed over each other, and
the cotton receiving three compressions in its passage.
This makes a much more solid and tractable sheet of cotton, and it is
now simply wound upon an iron roller in the form of a roll of cotton
termed a "lap," being now ready for the subsequent process, as shown in
the illustration (Fig. 14).
Image: FIG. 14.--Scutching machine with "lap" at the back.
=Scutching.=--This term obviously means beating, and the process itself is
simply a repetition of the opening and cleaning properties of the
opener, these objects being attained to a greater degree of perfection.
For the best classes of cotton it is often deemed sufficient to pass it
through the opener alone, and then to immediately transfer the lap to
the process of carding. For some cottons it is the practice to pass the
cotton through two scutchers in addition to the opener, while in other
cases it is the practice to use one scutcher only in addition to the
opener.
In the scutcher it is the most common practice to take four laps from
the opener and to place them in a specially constructed creel and
resting on a travelling "lattice" or apron. By this they are slowly
unwound and the four sheets are laid one upon another and passed in one
combined sheet, through feed rollers, to a two or three bladed beater,
exactly like the second one described when treating upon the double
opener. Also, exactly in the same manner, a lap is formed ready for the
immediately succeeding process of carding. In the scutcher the doubling
of four laps together tends to produce a sheet of cotton more uniform in
thickness and weight than that from the opener. This object of equality
of lap is also invariably aided by what are termed Automatic Feed
Regulators, which regulate the weight of cotton given to the beater to
something like a continuous uniformity. The action is clearly seen in
the illustration.
=Carding.=--By many persons this is deemed to be the most important
operation in cotton spinning. Its several duties may be stated as
follows:--
1. The removal of a large proportion of any impurities, such as
broken leaf, seed and shell, that may have escaped the previous
processes. It may usually be deemed to be the final process of
cleansing.
2. To open out and disentangle the clusters of fibres into even
greater individualisation than existed when first picked, and to
leave them in such condition that the subsequent operations can
easily draw them out, and reduce them to parallel order.
3. The extraction of a good proportion of the short, broken and
unripe fibres, present more or less in all cottons grown, and
practically worthless from a manufacturing point of view.
4. The reduction of the heavy sheet or lap of cotton from the
scutcher, into a comparatively light and thin sliver. Ordinarily,
one yard of the lap put up behind the card weighs more than 100
times as heavy as the sliver delivered at the front of the card.
There are several varieties of Carding Engine, but in each case nearly
all the essential features are practically the same in one card as in
another. At the present time, the type of Carding Engine which has
practically superseded all others is denominated the "Revolving Flat
Card." This Card originated with Mr. Evan Leigh, of Manchester, and
after being in close competition with several other types has almost
driven them out of the market. Of course it has been considerably
improved by later inventors, and various machine makers have their own
technical peculiarities.
In the illustration seen in Fig. 15 there is conveyed an excellent idea
of the appearance of the heavy lap of cotton as it is placed behind the
Carding Engine, and of the manner in which the same cotton appears as a
"sliver" or soft strand of cotton as it issues from the front of the
same machine, and enters the cylindrical can into which it is passed,
and coiled into compact layers, suitable for withdrawal at the
immediately succeeding process.
Image: FIG. 15.--Two views of the carding engine: upper view, cotton
entering; lower view, cotton leaving.
In the main, the parts which operate upon the cotton fibres in their
passage through this machine consist of a number of cylinders or rollers
of various diameters, but practically equal in width. Some of these
rollers are merely to guide and conduct the cotton forward, but the more
important are literally bristling all over with a vast number of closely
set and finely drawn steel wire teeth, whose duty it is to open, and
comb out, and clean the fibers as they pass along.
To begin with, the "lap" or roll of cotton is placed behind the machine
so as to rest on a roller of 6 inches in diameter, which slowly unwinds
the lap at the rate of about 9 inches per minute, by frictional contact
therewith.
Here, it may be said that the width of this and other chief rollers and
cylindrical parts of the card may be about 38 inches or 40 inches wide,
there being a tendency to make present-day Carding Engines rather
narrower than formerly, in order to give greater strength to certain
parts. From the lap roller the sheet of cotton is conducted for about 8
inches over a smooth feed plate, and then it goes underneath a fluted
roller of 2-1/4 inches diameter, termed the feed roller, having
practically the same surface speed as the lap roller, or possibly a
small fraction more to keep the cotton lap tight.
At this stage the actual work of the Carding Engine may be said to
commence. While the feed roller and the feed plate hold the end of the
sheet of cotton and project it forward at the slow rate of 8 or 9 inches
per minute, this projecting end of the lap becomes subject to the action
of a powerful roller or beater termed the taker-in or licker-in.
The most recent and improved construction of this roller is termed the
Metallic Taker-in, and it is covered all over with strong steel teeth
shaped something like those of a saw. It is about 9 inches in diameter,
and its strong teeth strike the cotton down from the feed roller with a
surface speed of nearly 1000 feet per minute.
It is at this stage that the bulk of the heavier impurities still found
in the cotton are removed, as these fall through certain grids below the
taker-in immediately they are loosened from the retaining fibres by the
powerful teeth of the taker-in.
The great bulk of the cotton fibres, however, are retained by the teeth
of the taker-in and carried round the under side to a point where they
are exposed to the action of the central and most important part of
every Carding Engine, viz., the main "cylinder." The licker-in contains
about twenty-eight teeth per square inch, but the "cylinder" is the
first of the parts that the cotton arrives at, previously referred to as
being covered with a vast number of closely set steel wire teeth.
Just to convey an idea of this point to the uninitiated reader, it may
be said that it is quite common to have on the "cylinder" as many as 600
steel wire teeth in one square inch. For a cylinder 40 inches wide and
50 inches diameter, this works out to the vast number of over 3,800,000
steel wire teeth on one cylinder, each tooth being about 1/4 inch long,
and secured in a cloth or rubber foundation before the latter is wound
round the cylinder.
The steel teeth of the cylinder strip the fibres from the taker-in and
carry them in an upward direction, the surface speed of the cylinder
being over 2000 feet per minute.
Placed over the cylinder, and extending for nearly one-half of its
circumference, are what are technically known as the "flats."
These are narrow iron bars, each about 1-3/8 inches wide; each being
covered with steel wire teeth in the same manner as the cylinder; and
each extending right across the width of the cylinder, and resting on a
suitable bearing termed the "bend."
They are formed into an endless chain containing about 108 "flats," but
only about 44 of which are in actual work at one time; this endless
chain of flats being given a slow movement of about 3 inches per minute.
Here it may be said that the various working parts are set as close as
possible to each other without being in actual contact, the usual
distance being about 1/143rd of an inch determined by a specially
constructed gauge, in the hands of a skilled workman.
The steel teeth of the flats, being set very close to those of the
cylinder, catch hold of and retain a portion of the short warty fibres
and fine impurities that may be on the points of the cylinder teeth, the
amount of this reaching about 3 per cent. of the cotton passed through
the machine. In addition to this the teeth of the flats work against
those of the cylinder so as to exercise a combing action on the cotton
fibres.
Having passed the "flats," the cotton is deposited by the cylinder on
what is termed the doffer. This is a cylindrical body, exactly similar
to the main "cylinder" excepting that it is only about half the
diameter, say 24 inches. Its steel wire teeth are set in the opposite
way to those of the cylinder, and its surface speed is only about 75
feet per minute. These two circumstances acting together enable it to
take the cotton fibres from the main cylinder.
The operations of carding may now be said to be practically performed,
as the remaining operations have for their object the stripping,
collecting, and guiding of the cotton into a form suitable for the next
succeeding processes. The fleece of cotton is stripped from the doffer
by the "Doffer Comb," which is a thin bar of steel, having a serrated
under edge, and making about 1600 beats or strokes per minute. From this
point cotton is collected into the form of a loose rope or "sliver," and
passed first through a trumpet-shaped mouth, and then through a pair of
calender rollers about six inches wide and four inches in diameter.
Image: FIG. 16.--Lap, web, and sliver of cotton.
Finally, the sliver of cotton is carried upward, as shown in the
illustration (Fig. 15), and passed through special apparatus and
deposited into the can, also shown. This latter is about 10 inches in
diameter and 36 inches in length, and the whole arrangement for
depositing the cotton suitably into the can is denominated the "Coiler."
In the next illustration (Fig. 16) are shown three forms in which the
cotton is found before and after working by the Carding Engine. That to
the left is the lap as it enters, the middle figure is part of the web
as it comes from the doffer, and that to the right is part of a coil of
cotton from the can.
Such is a brief description of the most important of the preparatory
processes of cotton spinning. There are innumerable details involving
technical knowledge which fall outside the province of this story.
=Drawing Frames.=--It is a very common thing for a new beginner in the
study of cotton spinning to ask--what is the use of the drawing frame?
As a matter of fact, the unpractised eye cannot see any difference
between the sliver or soft rope of cotton as it reaches, the drawing
frame and as it leaves the frame.
The experienced eye of the practical man can, however, detect a
wonderful difference.
It has been shown that the immediately preceding operation of
carding--amongst other things--reduces the heavy lap into a
comparatively thin light sliver; thus advancing with one great stride a
long way toward the production of the long fine thread of yarn ready for
the market.
No such difference can be perceived in the sliver at the drawing frame.
This machine is practically devoted to improving the thread finally
made in two distinct and important ways.
1. The fibres of cotton in the sliver, as they leave the Carding Engine,
are in a very crossed and entangled condition, not at all suited to the
production of a strong yarn by the usual processes of cotton spinning.
The first duty of the drawing frame may be said, therefore, to be the
laying of the fibres in parallel order to one another, by the action of
the drawing rollers.
2. The sliver of cotton, as it leaves the card, is by no means
sufficiently uniform in weight per yard for the production of a uniform
and strong finished thread. It will easily be conceived by the readers
of this story of the cotton plant that the strength of any thread is
only that of its weakest portions.
Take a rope intended to hold a heavy weight suspended at its lower end,
and assume it to be made of the best material and stoutest substance,
but to contain one very weak place in it; this rope would practically be
useless, because the strength of the rope would only be that of the
weakest part.
The drawing machine in cotton spinning aims at removing the weak places
in cotton thread, thus making the real strength of the thread vastly
greater than it would otherwise be.
The method by which these important objects are attained may be briefly
explained as follows:--
From four to eight, but most usually six, cans of sliver from the
previous machine are placed behind the frame, and the ends of the
slivers conducted over special mechanism within the range of action of
four pairs of drawing rollers. This passage of the cotton is shown very
clearly in Fig. 17.
The top rollers are made of cast iron, covered with soft and highly
finished leather made from sheepskins, the object of this being to cause
the rollers to have a firm grip of the cotton fibres, without at the
same time injuring them. The bottom rollers are of iron or steel, made
with longitudinal flutes or grooves, in order to bite the cotton fibres
firmly on the leathers of the top rollers. In order to assist the
rollers in maintaining a firm grip of the fibres the top rollers are
held down by somewhat heavy weights.
The action of the drawing rollers will be adequately discussed later in
this story, when dealing with the inventions of Lewis Paul and Sir
Richard Arkwright, and need not be enlarged upon at this stage.
It will be sufficient, therefore, to say that, assuming that six slivers
are put up together at the back of the frame, the "draft" or amount of
drawing-out between the first and second pairs of rollers the cotton
comes to, may be about 1.3, between the second and third pairs 1.8, and
between the third and fourth pairs 2.6. These three multiplied together
give a total draft of slightly over 6.
In other words, assuming that 1 inch of cotton be passed through the
first pair of rollers, the second pair will immediately draw it out into
1.3 inches; the third pair will draw out the same portion of cotton into
1.3 x 1.8 inches = 2.34 inches, and the fourth or last pair of rollers
will draw out the same portion of cotton into 2.34 x 2.6 inches = 6.084.
Image: FIG. 17.--Drawing frame showing eight slivers entering and one
leaving the machine.
The six slivers put up at the back are therefore drawn out or
attenuated to the dimensions of one by the rollers, and then at the
delivery side of the machine the six slivers are united into one sliver,
and arranged in beautiful order inside a can exactly as described for
the Carding Engine.
Now it is in the doubling together and again drawing-out of the slivers
of cotton that the two objects of making the fibres parallel and the
slivers uniform are effected.
In the first place, even the uninitiated readers of this story may
conceive that the combining of six slivers will naturally cause any
extra thick or thin places in any of the individual slivers to become
much reduced in extent by falling along with correct diameters of the
other five slivers; and experience proves that such is the actual fact.
In this way the slivers, or soft untwisted ropes of cotton, are made
uniform.
It is perhaps not so easy to see how it is that drawing rollers make the
fibres of cotton parallel. As a matter of fact, it may be said that as
each pair of rollers projects the fibres forward, the next pair of
rollers takes hold of the fibres and draws their front extremities
forward more rapidly than the other pair will let the back extremities
of the same fibres pass forward. It is this action often repeated that
draws the fibres straight, or in other words, reduces them to a
condition in which they are parallel to each other.
It is the usual practice to pass each portion of cotton through three
separate frames in this manner, in immediate and rapid succession. The
"slivers" or ropes of cotton made at the front of the first drawing
frame, would be placed in their cans behind a second drawing frame and
the exact process just described would be repeated. The same identical
process would usually be performed yet a third time in order to secure
the required objects with what is considered a sufficient degree of
perfection.
After this the cotton is usually deemed to be quite ready for the
immediately succeeding process of "slubbing."
=Bobbin and Fly Frames.=--The series of machines now to be dealt with, are
distinguished more for their complicated mechanism in putting twist into
the attenuated cotton and in winding it upon bobbins in suitable form
for the immediately succeeding process, than for the action of the parts
upon the cotton so as to render it better fitted for the production of
strong, fine yarn.
The manner in which these machines perform a part in the actual
production of a thread or yarn is practically a repetition of the work
of the drawing frame, with the great difference that the strand or thin
rope of cotton leaves each machine of the series in a thinner and longer
condition than when it arrived.
This attenuation of the cotton roving is indeed the chief desideratum
that bobbin and fly frames aim at, although they assist in making the
strand of cotton more uniform by carrying still further to a limited
extent the doubling principle so extensively utilised at the drawing
frames.
The basis of the operations are again the drawing rollers, brought to
such a state of perfection by Richard Arkwright, and here it may be
useful to remind the readers of this story how superior in this respect
of general adaption Arkwright's method of spinning was to that of
Hargreaves'. It will be remembered that the latter named inventor
utilised a travelling carriage, for drawing the cotton finer, while the
former performed the same work by drawing rollers.
Although the travelling carriage principle was at one time somewhat
largely utilised in preparing the rovings for the final process of
spinning, it has long since entirely given way before the superior
merits and adaptability of the drawing roller principle; and it is now
this latter method which is universally employed.
It usually takes three bobbin and fly frames to make up what may be
called a "set," each portion of the cotton roving passing through the
three machines in succession. For low classes of yarn only two of these
machines may be used, while for the finest yarns there are sometimes
four used to make up the "set."
Of course, all the readers of this story must understand that in an
ordinary-sized cotton spinning mill there will be many sets of these
machines, just as there will be a large number of "carding engines" and
"drawing frames," and mules. Bale brakers, openers and scutchers are so
very productive that only a limited number is required as compared with
the other machines already named.
Those of our readers who have studied the details of Arkwright's
spinning frame, described in another chapter in this book, and have
understood those details, will have a clear comprehension of the action
of the parts and leading mechanical principles concerned in the
operations of a modern bobbin and fly frame. Certainly there are some of
the most difficult problems of cotton spinning involved in the mechanism
of these machines, but these points are so highly technical that it is
not intended to introduce them here.
The "set" of machines just named are usually known by the names
"Slubber," "Intermediate or Second Slubber," and "Roving" Frames.
Nearly all the operations and mechanisms involved in one are almost
identical in the others, so that a description of one only in the set is
necessary, merely explaining that the parts of each machine the cotton
comes to in the latter two of the set are smaller and more finely set
than the corresponding parts of the immediately preceding machine.
Taking the Intermediate frame as a basis, the operation may be described
as follows:--The bobbins formed at the slubbing frame are put in the
creel of the Intermediate, as shown in the photograph (Fig. 18), each
bobbin resting on a wooden skewer or peg which will easily rotate.
In order to increase the uniformity of the roving or strand of cotton,
the ends from two of the slubbing rovings are conducted together through
the rollers of the machine.
There are three pairs of these rollers, acting on the cotton in every
way just as described for the drawing frame.
Although two rovings are put together behind the rollers, yet the
"draft" or drawing-out power of the rollers is such, that the roving
that issues from the front of the rollers is about three times as thin
as each individual roving put up behind the rollers. This drawing-out
action of the rollers need not be further dilated upon at this stage.
The points which demand some little attention at our hands, are the
methods and mechanism involved in twisting the attenuated roving, and
winding it upon bobbins or spools in suitable form for the next process.
Image: FIG. 18.--Intermediate frame (bobbin and fly frame).
As regards twisting of the roving it must be distinctly understood that
when the attenuated strand of cotton issues from the rollers of the
first bobbin and fly frame, it has become so thin and weak that it can
no longer withstand the requisite handling without being seriously
damaged. Hence the introduction of "Twist," which is by far the most
important strength-producing factor or principle entering into the
composition of cotton roving and yarn.
Without twist there would be no cotton factories, no cotton goods; none
of the splendid and gigantic buildings of one description or another
which are found so plentifully intermingled with the dwellings and
factories of large cotton manufacturing towns!
In a sense it is to this all-powerful factor of "twist" that all these
buildings owe their existence, since it would be practically impossible
to make a thread from cotton fibres without the assistance of "twist" to
make the fibres adhere to each other. Hence there could be none of that
wealth which has caused the erection of these buildings.
This is true in a double sense, since we have both the natural twist of
the cotton fibres and the artificial twist introduced at the latter
processes of cotton spinning, in order to make individual fibres and
aggregations of fibres adhere to each other. What is termed the natural
twist of the fibres may average in good cottons upwards of 180 twists
per inch, while the twists per inch put into the finished threads of
yarn from those fibres may vary, say, between 20 and 30 twists per
inch.
In all the fly frames, therefore, this artificial twist is invariably
and necessarily put into the roving. As the cotton leaves the front or
delivery rollers, each strand descends to a bobbin of from 8 to 12
inches long, upon which it is wound by special mechanism. As in
Arkwright's frame, this bobbin is placed loosely upon a vertical
"spindle," and upon the latter is fitted a "flyer," whose duty it is to
guide the cotton upon the bobbin.
The primary duty of the spindle is to insert the "twist" which has been
shown to be so necessary to give sufficient strength to the roving.
Let any reader of this story hold a piece of soft stuff in one hand
while with the other hand he rotates or twists the roving and he will
have an idea of the method and effect of twisting (see Fig. 19).
Without going into minute details we may say that the practical effect
is that, while the roving is held firmly by the rollers, it is twisted
by means of its connection at the other end to the rotating bobbin,
spindle and flyer. The twist runs right from the spindle along the 6 to
12 inches of cotton that may extend from the spindle top to the "nip" of
the rollers, thus imparting the requisite strength to the roving as it
issues from the rollers. The mechanism for revolving the spindles is by
no means difficult to understand, simply consisting of a number of
shafts and wheels revolved at a constant, definite and regulated speed
per minute.
Not only is it necessary to provide special apparatus for twisting the
cotton at the bobbin and fly frames, but also very complicated and
highly ingenious mechanism for winding the attenuated cotton in suitable
form upon the bobbins. Indeed it is with this very mechanism that some
of the most difficult problems of cotton spinning machinery are
associated.
Although the cotton at this stage is strengthened by twist, yet it is
extremely inadvisable and practically inadmissible to insert more than
from 1 to about 4 twists per inch at any of these machines, so that at
the best the rovings are still very weak.
If too much twist were inserted at any stage, the drawing rollers of the
immediately succeeding machine could not carry on the attenuating
process satisfactorily.
This winding problem was so difficult that it absolutely baffled the
ingenuity of Arkwright and his contemporaries and immediate successors,
and it was not until about 1825 that the difficulties were solved by the
invention of the differential winding motion by Mr. Holdsworth, a
well-known Manchester spinner, whose successors are still eminent master
cotton spinners.
This winding motion is still more extensively used than any other,
although it may be said that quite recently several new motions have
been more or less adopted, whose design is to displace Holdsworth's
motion by performing the same work in a rather more satisfactory manner.
In these pages no attempt whatever will be made to give a technical
explanation of the mechanism of the winding motion. It may be said that
it was a special application of the Sun and Planet motion originally
utilised by Watt in his Steam Engine, for obtaining a rotary motion of
his fly-wheel.
Sufficient be it to say that this "Differential Motion," acting in
conjunction with what are termed "Cone drums," imparts a varying motion
to the bobbins upon which the cotton is wound, in such a manner that the
rate of winding is kept practically constant throughout the formation of
the bobbins of roving, although the diameters of the latter are
constantly increasing.
The spindles and bobbins always rotate in the same direction, but while
the revolutions per minute of the spindles are constant, so as to keep
the twist uniform, those of the bobbins are always varying, in order to
compensate for their increasing diameters or thicknesses of the bobbins.
The delivery of cotton from the rollers is also constant and the
mechanism required to operate them is exceedingly simple.
A vast number of details could easily be added respecting the operations
performed by the bobbin and fly frames, but further treatment is deemed
unnecessary in this story.