THE MODERN SPINNING MULE.
=The Self-Actor Mule.=--In the preceding chapter there has been detailed
the particulars of the invention of the "Mule" by Samuel Crompton. Since
that event the mule has been the object of over a century of constant
and uninterrupted improvement and development, especially in the details
of greater or less importance.
The Self-Actor Mule of to-day represents and embodies the inventions of
hundreds of the most intelligent men ever connected with any industry in
the world's history. It is universally acknowledged to be one of the
most wonderful and useful machines ever used. The actual operations of
making a thread are however practically as left by Samuel Crompton over
a hundred years ago. It is only in details of mechanism involved in
making the various operations more perfectly automatic, and of greater
size and productiveness, that the long line of inventors since
Crompton's first mule was made, has been engaged.
To-day, such is the great size and wonderfully perfect automatic action
of these machines, that they are found 120 feet long, while in width,
over all, they may be 9 or 10 feet. Such a mule of this length would
contain over 1300 spindles, each spinning and winding 64 inches of
thread in about 15 seconds, and one man with two youths would be
sufficient to give all the attention such a machine required.
Independently of a vast number of inventors of smaller importance, there
are several names which stand out in greater prominence in the history
of the developments of the mule. Among these names must certainly be
placed, ahead of any others that might be named, that of Richard Roberts
of Manchester, who succeeded in 1830, after about five years'
application, in making the mule self-acting.
A good number of ingenious individuals had contributed more or less to
this result between the dates of Crompton's and Roberts' inventions, and
doubtless the results of the labours of these would be of great service
to Roberts in his great task.
Indeed, several inventors had previously brought out what might be
termed self-action mules, but it remained for Roberts to endow it with
that constant and automatic motion which obtains to-day in practically
the same form as left by him.
The special portion of mechanism with which his name is more especially
identified, is what is denominated the "Quadrant." This is practically
the fourth part of a large wheel, which is so arranged and connected
that it performs almost exactly the same functions on a mule that
Holdsworth's differential motion performs on the bobbin and fly frames.
To look at it, one would imagine it to be--what it really is--one of the
simplest pieces of mechanism possible, yet the actions performed by it
are complex and beautiful in the extreme. Later on, these actions of
the Quadrant will be carefully examined.
Image: FIG. 26.--Mule head showing quadrant.
The self-actor mule is an intermittent spinning machine, _i.e._, it is
not continuous in action, as are most machines used in the making of
thread or yarn from the fibrous product of the Cotton plant. Take for
instance the Carding Engine, and the bobbin and fly frames, as
previously described. So long as these machines are working, practically
all of the acting parts of the mechanism have a continuous forward
motion.
This is by no means the case with the machine now under consideration,
as many of the more important and principal parts move alternately in
opposite directions, while other of the less important may revolve at
one time, and be stationary at another.
What are called the medium counts of yarn contain say from 30 to 50
hanks in one pound avoirdupois; a cotton hank being equal to 840 yards,
so that one pound of 40's yarn will contain no less than 40 x 840 yards
or 33,600.
For such yarns as these, a modern self-actor mule would probably go
through its cycle of movements four times per minute. For coarser or
thicker yarns this speed might be increased, while for finer and better
qualities of yarn the speed would be diminished.
Now as each succeeding "stretch" marks a complete cycle of movements and
is a repetition of others, it will probably suffice if a brief
non-technical description of one of these "stretches" or "draws," as
they are termed in mill parlance, be given.
As in the bobbin and fly frames, the bobbins containing the rovings of
cotton to be operated upon, are placed behind the mules on skewers
fitted in a suitable framework of wood and iron called "creels," so as
to allow the cotton to be easily pulled off and unwound without
breaking. These rovings are guided to and drawn through three pairs of
drawing rollers (see Fig. 27), which shows this very fully.
The chief difference between these rollers and those of the previously
described machines being in the lessened diameters of the mule rollers,
and consequently attenuating the cotton to a much greater extent. It
is a truism well understood by those in the trade, that the finer the
rovings are the better the raw cotton must be, and the more drawing-out
they will stand in any one machine. One inch of roving put up behind the
rollers of a mule spinning medium numbers would probably be drawn out
into 9 inches.
Image: FIG. 27.--Mules showing "stretch" of cotton yarn.
Nothing more need be said here about the action of the drawing rollers.
As the attenuated rovings leave the roller at the front, each one is
conducted down to a spindle revolving at a high rate of speed; so
quickly indeed, that there is no other body used in spinning which
approaches it for speed.
It is quite a usual practice to have them making about 8000 revolutions
per minute, and sometimes a speed of 10,000 is attained by them.
Assuming that a "Cop" of yarn (see Fig. 27), showing the cops on the
spindles, has been partly made upon each spindle, the roving or thread
from the rollers would extend down to the cop and be coiled round the
spindle upwards up to the apex. The spindle would probably twist the
thread for 40's counts twenty-three or twenty-four times for each inch
that issued from the rollers, there being a well-recognised scale of
"twists per inch" for various sorts and degrees of fineness of yarn.
Unlike the bobbin and fly frames, the roving or yarn is not wound on its
cop or spindle as it is delivered, but a certain definite and regulated
length of cotton is given out to each spindle, and fully twisted and
attenuated before it is wound into a suitable shape for transit and for
subsequent treatment.
To keep each thread in tension, therefore, as it is delivered from the
rollers, the carriage containing the twisting spindles is made to recede
quickly away from the rollers, a common distance for such movement being
64 inches. All the time the spindles are quickly revolving and putting
twist into the rovings, thus imparting strength to them to a far greater
degree than at any previous stage. Often the carriage is made to recede
from the rollers a little quicker than the latter, the difference in the
surface speeds between the two being technically known as "_gain_." The
object of this carriage "gain" is to improve the "evenness" of the yarn
by drawing out any thick soft places there may be in the length of
thread between each spindle and the roller, a distance of 64 inches. It
is a property of the twist that it will run much more readily into the
thinner portions of thread than the thicker, thus leaving the latter
capable of stretching out without breaking.
Arrived at the limit of 64 inches stretch (see Fig. 27), certain rods,
levers, wheels and springs are so actuated that the parts which draw out
the carriage and cause the rollers to revolve are disconnected, so that
both are brought to a standstill for the moment.
In many cases the spindles at this stage are kept on revolving in order
to put in any twist that may be lacking in any portion of the stretch.
Twisting being finished, the important operation of "backing off"
commences.
It maybe at once explained that "backing off" means the reversing of the
spindles; the uncoiling of a portion of the yarn from the spindles; and
generally putting all the requisite apparatus into position ready for
winding or coiling the attenuated and twisted rovings upon the spindles.
Here come now into action those most beautiful and ingenious
applications of mechanical principles, the working out of which entailed
so many years of arduous effort, and which rendered the mule practically
self-acting and automatic.
By a most wonderful, intricate and clever combination of levers, wheels,
pulleys and springs, aided by what is called a "friction clutch," the
instant the spindles have ceased twisting the yarn, they are reversed in
direction of revolution.
This reversal only occupies two or three seconds, and as the motion
imparted to the spindles is very slow at this stage, the practical
effect is, that a small portion of yarn is "_uncoiled_" from each
spindle, sufficient to allow of two "guide wires" to assume proper and
necessary positions for winding the attenuated threads upon the
spindles.
These two wires are termed "faller wires," and while one is controlled
by the cop-shaping mechanism and termed the "winding faller wire" the
other simply keeps the threads in the requisite state of tension during
"winding on" and is termed the "counter" or "tension faller wire." Both
these wires can be seen in Fig. 28. During backing off, the "winding
faller wire" has a descending motion, while the "counter faller" has an
ascending motion, these being necessary for them to attain their proper
positions for "winding on."
Image: FIG. 28.--Mule showing action of faller wires.
The movement of these faller wires into proper position, and the
uncoiling of a small portion of yarn from each spindle, are both brought
about by the "backing off" motion, which formed an important part of
Roberts' Mule. It may be remarked, however, that certain of the
predecessors of Roberts had made great efforts in this direction, thus
making the way much easier for his applications, which were entirely
successful. When "backing off" is completed, all the necessary parts are
in position for winding the 64 inches of thread just given out upon each
spindle.
This practically involves three primary and most important operations.
(1) The drawing-in of the carriage back to its original position. (2)
The revolution of the spindles at a speed suitable for winding the
threads upon the spindles as the carriage moves inwards. (3) The guiding
of the threads upon the spindles in such a manner that a cop of yarn
will eventually be formed upon each spindle, of such dimensions and
shape as to be quite suitable for any subsequent processes or handling.
Taking these three important divisions in the order given, it may be
said that the drawing-in of the carriage is effected through the medium
of the "scroll" bands, which are attached to the carriage at one end,
and to certain spiral scrolls or fusees at the other end. The scrolls
being revolved, wind the cords or bands round them, so pulling in the
carriage. There are usually two back scroll bands and one front band,
the latter being a sort of check band upon the action of the other two.
What is termed the "rim band" revolves the spindles during the outward
traverse of the carriage.
The drawing-in of the carriage in a sense causes the other two
operations to be performed. With respect to the second of these, viz.,
revolving the spindles and thus winding the threads upon them, it may be
said this action causes what is termed the "Winding Chain" to pull off a
small drum of six inches diameter, thus rotating the latter and thereby
the spindles. Here, however, comes in now the action of the very
beautiful and effective piece of mechanism, "Roberts' quadrant" (see
Fig. 26). The winding chain just mentioned is attached to one extremity
to the arm of the quadrant, and the peculiar manner in which the
quadrant moves in relation to the winding drum gives the variable motion
to the spindles that is required.
When commencing a new set of cops it may take about eighty revolutions
of the spindles to wind on the 64 inches of thread to each spindle,
representing one stretch. The bare spindle may be about a quarter of an
inch in diameter, but it may finally attain a diameter of an inch and a
quarter (_i.e._, the cop upon the spindle). This cop will only require
about twenty revolutions to wind on the 64 inches, which are only
one-fourth of the revolutions necessary for the empty spindles. It is
the action of the quadrant which gives this variation in speed to the
spindles during winding-on.
But as has been pointed out previously, the quadrant imparts a
"differential winding" motion to the spindles in two distinct and
different ways, and the second motion is even more important than the
first.
It is necessary for practical purposes that the cop of yarn should be
built up of a conical shape in the upper part, as shown in the
illustration. Now it must be obvious to the least technical of the
readers of this story, that to wind a given portion of yarn upon the
thin apex of a cone, will require a greater number of revolutions than
would be necessary to wind the same length of yarn upon the base of the
same cop. All the way between the apex and the base of the cone are also
other varying diameters, and during each return movement of the mule
carriage the thread is wound upon all the varying diameters of the cone
in succession.
This implies the necessity for the revolutions of the spindles to a
varying quantity all the time of the return or inward movement of the
spindle carriage.
The quadrant gives this varying speed in a manner which is all but
mathematically correct, any slight deviation from any such mathematical
correctness being easily compensated for in other ways.
For the specific manner in which this quadrant works, the reader is
referred to any of the recent text-books on cotton spinning.
The third primary and important operation, which takes place during each
return movement of the carriage, is the guiding of the thread upon the
spindles in a correct manner. This operation is closely associated,
however, with the action of the quadrant.
That portion of a "self-actor mule" which guides the faller wires is
termed the "shaper" or "copping motion." It consists of an inclined iron
rail upon the upper smooth surface of which slides the "copping bowl,"
this being a portion of the mechanism which connects the rail with the
faller wires. The rail rests upon suitable inclines termed "copping
plates," whose duty it is to regulate the movement of the rail so as to
allow for the ever-increasing dimensions of the cop during the building
process. When the carriage again reaches its initial position, suitable
mechanism causes all the parts to return in the position required for
spinning.
Such is the complete cycle of movements of the "mule," each succeeding
cycle being simply a repetition of the preceding. It will probably take
such a mule as the one described about six hours to make a "set of
cops," _i.e._, one on each spindle, each cop being 1-1/4 inches in
diameter and 7-1/2 inches long. Every fifteen seconds, while the mule is
making a cycle of its movements, may be divided up approximately as
follows: nine seconds for the drawing-out and twisting; two seconds for
backing-off; four seconds for winding-on and resuming initial position.
A multitude of minor motions and details might be easily expanded into
several chapters; in fact, more can be said about the mule than about
any other spinning machine, but such detailed description would be out
of place in this story.
All the motions just named are centred in what is termed the "Head
Stock," this being placed midway in the length of the mule.
This head stock receives all the power to drive the various motions,
from the shafting and gearing, and distributes it in a suitable manner
to various parts of the machine.
It will have been observed by this time, that, as in the case of the
bobbin and fly frames, the intricate and wonderful mechanism of the
self-actor mule is not devoted to the formation of threads, but to the
effective and economical placing of the threads of yarn, in the form of
cops, after it has been spun.
Image: FIG. 29.--Mule head showing "copping rail."
The spinning processes take place during the outward traverse of the
mule carriage, the mechanism involved in this motion being comparatively
simple. The really complicated and difficult motions being
"backing-off," revolving the spindles "during winding-on," and the
guiding of the spun threads upon the spindles during the winding-on
process. It was the addition of these three motions by the later
inventors which gave the mule the title of "Self-Acting."