The Jute Industry: From Seed to Finished Cloth by T. Woodhouse and P. Kilgour
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T. Woodhouse and P. Kilgour >> The Jute Industry: From Seed to Finished Cloth
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The root ends of stricks are sometimes treated by a special machine
termed a root-comber with the object of loosening the comparatively
hard end of the strick. A snipping machine or a teazer may also be
used for somewhat similar purposes, and for opening out ropes and
similar close textures.
The cuttings may be partially loosened by means of blows from a
heavy iron bar; boiling water is then poured on the fibre, and then
the material is built up with room left for expansion, and allowed
to remain in this condition for a few days. A certain quantity of
this material may then be used along with other marks of jute to
form a batch suitable for the intended yarn.
A very common practice is to cut the hard root ends off by means of
a large stationary knife. At other times, the thin ends of the
stricks are also cut off by the same instrument. These two parts are
severed when it is desired to utilize only the best part of the
strick. The root ends are usually darker in colour than the remainder,
and hence the above process is one of selection with the object of
securing a yarn which will be uniform in colour and in strength.
CHAPTER VII. CARDING
_Breaker and Finisher Cards_. After the fibre from the softening
machine has been conditioned for the desired time, it is ready for
one of the most important processes in the cycle of jute manufacture;
this process is termed carding, and is conducted in two distinct
types of machines--
1. The breaker card.
2. The finisher card.
The functions of the two machines are almost identical; indeed, one
might say that the work of carding should be looked upon as one
continuous operation.
The main difference between the two types of machines is in the
method of feeding, and the degree of fineness or setting of the
small tools or pins which perform the work. In both cases the action
on the stricks of jute is equivalent to a combined combing and
splitting movement, and the pins in the various rollers move
relatively to each other so that while the pins of a slowly-moving
roller allow the strick or stricks (because there are several side
by side) to pass slowly and gradually from end to end, the pins of
another but quickly-moving roller perform the splitting and the
combing of the fibre. The pins of the slowly-moving roller hold, so
to speak, the strick, while the pins of the quickly-moving roller
comb out the fibres and split adhering parts asunder so as to make a
comparatively fine division.
The conditioned stricks from the softening machine are first
arranged in some suitable receptacle and within easy reach of the
operative at the back or feed side of the breaker card. A receptacle,
very similar to that used at the breaker card, appears near the far
end of the softening machine in Fig. 13.
A modern breaker card is illustrated in Fig. 14. The feed or back of
the card is on the extreme right, the delivery or front of the card
on the extreme left, while the gear side of the card is facing the
observer. The protecting cages were removed so that the wheels would
be seen as clearly as possible.
Some of the stricks of fibre are seen distinctly on the feed side of
the figure; they are accommodated, as mentioned, in a channel-shaped
stand on the far side of the inclined feed sheet, or feed cloth,
which leads up to and conveys the stricks into the grip of the
feeding apparatus. This particular type is termed a "shell" feed
because the upper contour of the guiding feed bracket is shaped
somewhat like a shell. There is a gradually decreasing and
suitably-sized gap between the upper part of the shell and the pins
of the feed roller.
The root ends of the pins in this roller lead, and the stricks of
fibre are gripped between the pins and the shell, and simultaneously
carried into the machine where they come into contact with the
points of the pins in the rapidly-revolving large roller, termed a
cylinder. The above-mentioned combing and splitting action takes
place at this point as well as for a distance of, say, 24 inches to
30 inches below. The fibres which are separated at this stage are
carried a little further round until they come into contact with the
points of the pins in the above-mentioned slowly-moving roller,
termed a "worker," and while the fibres are moving slowly forward
under the restraining influence of the worker, they are further
combed and split. A portion of the fibres is carried round by the
pins of the worker from which such fibres are removed by the
quicker moving pins of the second roller of the pair, termed a
"stripper," and in turn these fibres are removed from the pins of
the stripper by the much quicker moving pins of the cylinder.
[Illustration: FIG. 14 MODERN BREAKER CARD]
The above operations conducted by the first pair of rollers (worker
and stripper) in conjunction with the cylinder, are repeated by a
second and similar pair of rollers (worker and stripper), and ultimately
the thin sheet of combed and split fibres comes into contact with the
pins of the doffer from which it is removed by the drawing and pressing
rollers. The sheet of fibres finally emerges from these rollers into
the broad and upper part of the conductor. This conductor, made mostly
of tin and V-shaped, is shown clearly on the left of the machine in
Fig. 14. Immediately the thin film or sheet of fibres enters the
conductor, it is caused as a body gradually to contract in width and,
of course, to increase in thickness, and is simultaneously guided and
delivered to the delivery rollers, and from these to the sliver can,
distinctly seen immediately below the delivery rollers. The sliver is
seen emerging from the above rollers and entering the sliver can.
The fibres in this machine are thus combed, split and drawn forward
relatively to each other, in addition to being arranged more or less
parallel to each other. The technical term "draft" is used to
indicate the operation of causing the fibres to slip on each other,
and in future we shall speak about this attenuation or drawing out
of the fibres by this special term "draft."
It will be evident that, since the sliver is delivered into the can
at the rate of about 50 yards per minute, this constant flow will
soon provide a sufficient length of sliver to fill a sliver can,
although the latter may hold approximately 20 lbs. The machine must,
of course, deliver its quota to enable succeeding machines to be
kept in practically constant work. As a matter of fact, the machines
are arranged in what are termed "systems," so that this desirable
condition of a constant and sufficient feed to all may be
satisfactorily fulfilled.
The driving or pulley side of the breaker card is very similar to
that shown in Fig. 15 which, however, actually represents the pulley
side of one type of finisher card as made by Messrs. Douglas Fraser &
Sons, Ltd., Arbroath. All finisher cards are fed by slivers which
have been made as explained in connection with the breaker card, but
there are two distinct methods of feeding the slivers, or rather of
arranging the slivers at the feed side. In both cases, however, the
full width of the card is fed by slivers laid side by side, with,
however, a thin guide plate between each pair, and one at each
extreme end.
One very common method of feeding is to place 10 or 12 full sliver
cans--which have been prepared at the breaker card--on the floor and
to the right of the machine illustrated in Fig. 15. The sliver from
each can is then placed into the corresponding sliver guide, and
thus the full width of the machine is occupied. The slivers are
guided by the sliver guides on to an endless cloth or "feed sheet"
which, in turn, conveys them continuously between the feed rollers.
The feed apparatus in such machines is invariably of the roller type,
and sometimes it involves what is known as a "porcupine" roller. It
will be understood that the feeding of level slivers is a different
problem from that which necessitates the feeding of comparatively
uneven stricks.
[Illustration: By permission of Messrs. Douglas Fraser & Sons, Ltd.
FIG. 15 FINISHER CARD WITH DRAWING-HEAD]
The slivers travel horizontally with the feed-sheet and enter the
machine at a height of about 4 feet from the floor. They thus form,
as it were, a sheet of fibrous material at the entrance, and this
sheet of fibres comes in contact with the pins of the various pairs
of rollers, the cylinder, and the doffer, in much the same way as
already described in connection with the breaker card. There are,
however, more pairs of rollers in the finisher card than there are
in the breaker card, for while the latter is provided with two pairs
of rollers, the former may be arranged with 3, 4, 5 or even 6 pairs
of rollers (6 workers and 6 strippers). The number of pairs of
rollers depends upon the degree of work required, and upon the
opinions of the various managers.
There are two distinct types of finisher cards, viz--
1. Half-circular finisher cards.
2. Full-circular finisher cards.
The machine illustrated in Fig. 15 is of the latter type, and such
machines are so-called because the various pairs of rollers are so
disposed around the cylinder that they occupy almost a complete
circle, and the fibre under treatment must move from pair to pair to
undergo the combing and splitting action before coming into contact
with the doffer. There are five pairs of rollers in the machine in
Fig. 15, and all the rollers are securely boxed in, and the wheels
fenced. The arrangement of the wheels on the gear side is very
similar to that shown in connection with the breaker card in Fig. 14,
and therefore requires no further mention. Outside the boxing comes
the covers, shown clearly at the back of the machine in Fig. 15, and
adapted to be easily and quickly opened when it is desired to
examine the rollers and other parts.
The slivers, after having passed amongst the pins of the various
rollers, and been subjected to the required degree of draft, are
ultimately doffed as a thin film of fibres from the pins of the
cylinder and pass between the drawing rollers to the conductor. The
conductor of a finisher card is made in two widths, so that half the
width of the film enters one section and the other half enters the
other section. These two parallel sheets, split from one common sheet,
traverse the two conductors and are ultimately delivered as two
slivers about 6 inches above the point or plane in which the 10 or 12
slivers entered, and on to what is termed a "sliver plate." The two
slivers are then guided by horns projecting from the upper surface
of the sliver plate, made to travel at right angles to the direction
of delivery from the mouths of the conductors, and then united to
pass as a single sliver between a pair of delivery rollers on the
left of the feed and delivery side and finally into a sliver can.
In special types of finishing cards, an extra piece of
mechanism--termed a draw-head--is employed. The machine illustrated
in Fig. 15 is provided with this extra mechanism which is supported
by the small supplementary frame on the extreme right. This special
mechanism is termed a "Patent Push Bar Drawing Head," and the
function which it performs will be described shortly; in the
meantime it is sufficient to say that it is used only when the
slivers from the finisher card require extra or special treatment. A
very desirable condition in connection with the combination of a
finisher card and a draw-head is that the two distinct parts should
work in unison. In the machine under consideration, the feed and
delivery rollers of the card stop simultaneously with the stoppage
of the draw-head mechanism.
One of the chief aims in spinning is that of producing a uniform
thread; uniform not only in section, but in all other respects. A
so-called level thread refers, in general, to a uniform diameter,
but there are other equally, if not more, important phases connected
with the full sense of the word uniform.
It has already been stated that in the batching department various
qualities of jute are mixed as judiciously as possible in order to
obtain a satisfactory mixture. Fibres of different grades and marks
vary in strength, colour, cleanness, diameter, length and suppleness;
it is of the utmost importance that these fibres of diverse
qualities should be distributed as early as possible in the process
so as to facilitate the subsequent operations.
[Illustration: _By permission of Messrs. James F. Low & Co., Ltd. _
FIG. 16 WASTE TEAZER]
However skilfully the work of mixing the stricks is performed in the
batching department, the degree of uniformity leaves something to be
desired; further improvement is still desirable and indeed necessary.
It need hardly be said, however, that the extent of the improvement,
and the general final result, are influenced greatly by the care
which is exercised in the preliminary processes.
The very fact of uniting 10 or 12 slivers at the feed of the
finisher card mixes 10 or 12 distinct lengths into another new length,
and, in addition, separates in some measure the fibres of each
individual sliver. It must not be taken for granted that the new
length of sliver is identical with each of the individual lengths
and ten or twelve times as bulky. A process of drafting takes place
in the finisher card, so that the fibres which compose the combined
10 or 12 slivers shall be drawn out to a draft of 8 to 16 or even
more; this means that for every yard of the group of slivers which
passes into the machine there is drawn out a length of 8 to 16 yards
or whatever the draft happens to be. The resulting sliver will
therefore be approximately two-thirds the bulk of each of the
original individual slivers. The actual ratio between them will
obviously depend upon the actual draft which is imparted to the
material by the relative velocities of the feed and delivery rollers.
It is only natural to expect that a certain amount of the fibrous
material will escape from the rollers; this forms what is known as
card waste. And in all subsequent machines there is produced, in
spite of all care, a percentage of the amount fed into the machine
which is not delivered as perfect material. All this waste from
various sources, e.g. thread waste, rove waste, card waste, ropes,
dust-shaker waste, etc., is ultimately utilized to produce sliver
for heavy sacking weft.
The dust-shaker, as its name implies, separates the dust from the
valuable fibrous material, and finally all the waste products are
passed through a waste teazer such as that made by Messrs. J. F. Low &
Co., Ltd., Monifieth, and illustrated in Fig. 16. The resulting mass
is then re-carded, perhaps along with other more valuable material,
and made into a sliver which is used, as stated above, in the
production of a cheap and comparatively thick weft such as that used
for sacking.
CHAPTER VIII. DRAWING AND DRAWING FRAMES
The operations of combing and splitting as performed in both the
breaker and finisher card are obviously due to the circular movement
of the pins since all these (with the single exception of those in
the draw-head mechanism of certain finisher cards) are carried on the
peripheries of rotating rollers. In the draw-head mechanism, the
pins move, while in contact with the fibres, in a rectilinear or
straight path. In the machines which fall to be discussed in this
chapter, viz., the "drawing frames," the action of the pins on the
slivers from the finisher card is also in a straight path; as a
matter of fact, the draw-head of a finisher card is really a small
drawing frame, as its name implies. Moreover, each row or rather
double row, of pins is carried separately by what is termed a
"faller." The faller as a whole consists of three parts:
1. A long iron or steel rod with provision for being
moved in a closed circuit.
2. Pour or six brass plates, termed "gills" or
"stocks," fixed to the rod.
3. A series of short pins (one row sometimes about
1/8 in. shorter than the second row), termed gill or
hackle pins, and set perpendicularly in the above
gills.
The numbers of fallers used is determined partly by the particular
method of operating the fallers, but mostly by the length of the
fibre. The gill pins in the fallers are used to restrain the
movements of the fibres between two important pairs of rollers.
There are actually about four sets of rollers from front to back of
a drawing frame; one set of three rollers constitute the "retaining"
rollers; then comes the drawing roller and its large pressing roller;
immediately after this pair is the "slicking" rollers, and the last
pair is the delivery rollers. The delivery rollers of one type of
drawing frame, called the "push-bar" drawing frame, and made by
Messsrs. Douglas Fraser & Sons, Ltd., Arbroath, are seen distinctly
in Fig. 17, and the can or cans into which the slivers are
ultimately delivered are placed immediately below one or more
sections of these rollers and in the foreground of the illustration.
The large pressing rollers, which are in contact with the drawing
roller, occupy the highest position in the machine and near the
centre of same. Between these rollers and the retaining rollers are
situated the above-mentioned fallers with their complements of gill
pins, forming, so to speak, a field of pins.
Each sliver, and there maybe from four to eight or more in a set, is
led from its sliver can at the far side of the machine to the sliver
guide and between the retaining rollers. Immediately the slivers
leave the retaining rollers they are penetrated by the gill pins of
a faller which is rising from the lower part of its circuit to the
upper and active position. Each short length of slivers is
penetrated by the pins of a rising faller, these coming up
successively as the preceding one moves along at approximately the
same surface speed as that of the retaining rollers. The sheet of
pins and their fallers are thus continuously moving towards the
drawing rollers and supporting the slivers at the same time. As each
faller in succession approaches close to the drawing rollers, it is
made to descend so that the pins may leave the fibres, and from this
point the faller moves backwards towards the retaining roller until
it reaches the other end ready to rise again in contact with the
fibres and to repeat the cycle as just described. It will thus be
seen that the upper set of fallers occupy the full stretch between
the retaining rollers and the drawing rollers, but there is always
one faller leaving the upper set at the front and another joining
the set at the back.
[Illustration: Fig. 17 Push-bar drawing frame]
The actual distance between the retaining rollers and the drawing
rollers is determined by the length of the fibre, and must in all
cases be a little greater than the longest fibre. This condition is
necessary because the surface speed of the drawing roller is much
greater than that of the retaining rollers; indeed, the difference
between the surface speeds of the two pairs of rollers is the actual
draft.
Between the retaining and drawing rollers the slivers are embedded
in the gill pins of the fallers, and these move forward, as mentioned,
to support the stretch of slivers and to carry the latter to the nip
of the drawing rollers. Immediately the forward ends of the fibres
are nipped between the quickly-moving drawing rollers, the fibres
affected slide on those which have not yet reached the drawing
rollers, and, incidentally, help to parallelize the fibres. It will
be clear that if any fibre happened to be in the grip of the two
pairs of rollers having different surface speeds, such fibre would be
snapped. It is to avoid this rupture of fibres that the distance
between the two sets of rollers is greater than the longest fibres
under treatment. The technical word for this distance is "reach."
On emerging from the drawing rollers, the combed slivers pass
between slicking rollers, and then approach the sliver plate which
bridges the gap between the slicking rollers and the delivery rollers,
and by means of which plate two or more individual slivers are
diverted at right angles, first to join each other, and then again
diverted at right angles to join another sliver which passes
straight from the drawing rollers and over the sliver plate to the
guide of the delivery rollers. It will thus be seen that a number of
slivers, each having been drawn out according to the degree of draft,
are ultimately joined to pass through a common sliver guide or
conductor to the nip of the delivery rollers, and thence into a
sliver can.
The push-bar drawing illustrated in Fig. 17, or some other of the
same type, is often used as the first drawing frame in a set. With
the exception of the driving pulleys, all the gear wheels are at the
far end of the frame, and totally enclosed in dust-proof casing. The
set-on handles, for moving the belt from the loose pulley to the
fast pulley, or _vice versa_, are conveniently situated, as shown,
and in a place which is calculated to offer the least obstruction to
the operative. The machines are made with what are known as
"two heads" or "three heads." It will be seen from the large
pressing rollers that there are two pairs; hence the machine is a
"two-head" drawing frame.
The slivers from the first drawing frame are now subjected to a
further process of doubling and drafting in a very similar machine
termed the second drawing frame. The pins in the gills for this
frame are rather finer and more closely set than those in the first
drawing frame, but otherwise the active parts of the machines, and
the operations conducted therein, are practically identical, and
therefore need no further description. It should be mentioned,
however, that there are different types of drawing frames, and their
designation is invariably due to the particular manner in which the
fallers are operated while traversing the closed circuit. The names
of other drawing frames appear below.
Spiral or screw gill;
Open link chain;
Rotary;
Ring Carrier
Circular.
For the preparation of slivers for some classes of yarn it is
considered desirable to extend the drawing and doubling operation in
a third drawing frame; as a rule, however, two frames are considered
sufficient for most classes of ordinary yarn.
CHAPTER IX. THE ROVING FRAME
The process of doubling ends with the last drawing frame, but there
still remains a process by means of which the drafting of the
slivers and the parallelization of the fibres are continued. And, in
addition to these important functions, two other equally important
operations are conducted simultaneously, viz., that of imparting to
the drawn out sliver a slight twist to form what is known as a
"rove" or roving, and that of winding the rove on to a large rove
bobbin ready for the actual spinning frame.
The machine in which this multiple process is performed is termed a
"roving frame." Such machines are made in various sizes, and with
different types of faller mechanism, but each machine is provided
for the manipulation of two rows of bobbins, and, of course, with
two rows of spindles and flyers. These two rows of spindles, flyers,
and rove bobbin supports are shown clearly in Fig. 18, which
represents a spiral roving frame made by Messrs. Douglas Fraser &
Sons, Ltd., Arbroath.
Each circular bobbin support is provided with pins rising from the
upper face of the disc, and these pins serve to enter holes in the
flange of the bobbin and thus to drive the bobbin. The discs or
bobbin supports are situated in holes in the "lifter rail" or
"builder rail" or simply the "builder"; the vertical spindles pass
through the centre of the discs, each spindle being provided with a
"flyer," and finally a number of plates rest upon the tops of the
spindles.
[Illustration: FIG. 18 ROVING FRAME _By Permission of Messrs.
Douglas Fraser & Sons, Ltd_.]
A roving machine at work is shown in Fig. 19, and it will be seen
that the twisted sliver or rove on emerging from the drawing rollers
passes obliquely to the top of the spindle, through a guide eye,
then between the channel-shaped bend at the upper part of the flyer,
round the flyer arm, through an eye at the extreme end of either of
the flyer arms, and finally on to the bobbin. Each bobbin has its
own sliver can (occasionally two), and the sliver passes from this
can between the sides of the sliver guide, between the retaining
rollers, then amongst the gill pins of the fallers and between the
drawing (also the delivery) rollers. Here the sliver terminates
because the rotary action of the flyer imparts a little twist and
causes the material to assume a somewhat circular sectional form.
From this point, the path followed to the bobbin is that described
above.
As in all the preceding machines, the delivery speed of the sliver
is constant and is represented by the surface speed of the periphery
of the delivery rollers, this speed approximates to about 20 yards
per minute. The spindles and their flyers are also driven at a
constant speed, because in all cases we have--
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