_Making Warps for Elastic Fabrics—Quills for Use in Shuttles—Effect
of Finishing Processes Must Be Calculated from Beginning of Web
Construction—Details of Processes and Machines for Different Styles of
Goods—Care to Avoid Acid in Goods—Rubber’s Reaction on Copper_
The making of cotton warps for elastic fabrics, particularly for double
cloth webs, involves considerable thought and care in view of the
number of sections necessary for a properly constructed fabric, and the
different weaves employed. Owing to the contraction of the rubber, it is
essential at all times that the proper balance be maintained between the
face and the back of the goods.
This necessitates a uniform weight of stock where the weaves on the face
and the back are identical, no matter how the size of the yarns used may
vary, and a variable weight of stock where the weaves are different. All
this is determined by experimental work when establishing the grade.
These conditions necessitate separate warps for the face and back. Then
again the different weaves employed involve a variable length in the
take-up and this alone would make it impracticable to combine the various
weaves.
It is invariably the plan to use fine stock for the face and a coarser
material for the back. Of course it would not be practical to put these
together on the same beam. The crowded condition of material used
necessitates the further splitting of the face and back sections. The
binder, which takes up so much faster than any of the other yarns, also
requires a special warp.
SELVAGE UNDER SPECIAL CONTROL
The general appearance of the finished product being so dependent upon
the character of the selvage, it is advisable to have these threads under
special control, so that they may be treated in the best possible manner
to produce a satisfactory shed, and allow the filling to get a good
clearance. So as to secure a smooth well-rounded edge it is therefore
necessary to have this on a special beam.
It will be seen, therefore, that in an ordinary piece of double cloth
elastic web there will be required at least five warps: back, face,
binder, edge and gut. Figures and fancy effects will often necessitate
auxiliary warps. With very fine webs, having six threads to a cord, it
is often found necessary further to split up the face to obtain proper
working conditions. Figs. 1 and 1A show a six-cord web, together with
warp calculations for the goods.
The employment of so many warps to each strip of web, which are
automatically delivered by the friction let-off levers described in
a previous article, prohibits the use of warps where the threads are
equally distributed across the beam, as is the practice in wide fabrics,
the method usually being to tape them on the beams.
WARPING MACHINE
The required spools for the number of threads in the warp are put in a
creel, each thread passing under an electrically connected wire, which
is held out of contact by the running thread while the warp is making.
If the thread should break, the wire would drop and make an electrical
connection which would automatically stop the machine. Fig. 2 shows
a view of a warping machine such as is used for this work. They are
generally constructed so as to allow for two or four beams, all of which
may be run together or started, stopped or run individually, as required.
[Illustration: Fig. 1.—Six-Cord Web]
[Illustration: Fig. 1A.—Harness and Chain Draft for Fig. 1]
Each beam is friction driven so that a uniform speed is obtained in the
delivery of the yarn from the spools. Beams are also so arranged that
they will stop automatically on reaching a given size. Each warp thread
is passed through a pair of reeds, fitted with dead stops in the center
of alternating dent spaces, so that leases may be put in the warps at
fixed intervals to assist in keeping them straight in the looms.
In taping the warps on the beams, it is customary in some mills to run
the threads over a small steel flanged pulley about one and one-half
inches wide, which will keep each thread in its proper position and make
the tape absolutely straight and flat as it leads to the beam. A perfect
fabric is largely dependent upon how well the warps have been made, but
it must not be forgotten that a good warp may be spoiled by a poor beam.
Beam flanges should not lie flat against the warp creel standards, but
should be kept clear by the formation of the head near the barrel, which
should have enough prominence at this point to keep the flanges clear,
and thus reduce the friction to a minimum. The edges of the flanges
should be perfectly smooth so as to allow for uniform delivery by the
contact lever. Much of the beam abuse which occurs in many mills might be
avoided by provision being made for beam racks at convenient points.
[Illustration: Fig. 2.—Warping Machine]
QUILLS FOR SHUTTLES
The making of proper quills for use in the shuttle is of no small
importance, for on this the evenness and uniformity of the selvage very
much depends. When flanged wood quills are used, the guides should be
carefully adjusted so that the filling is uniformly spread over the
entire length of the quill, allowing for perfect freedom at each end
without dragging. Quills should not be overloaded. In drum pressure
quilling, the automatic stop should be so arranged that the quill will be
filled even with the outer edge of the flanges and no more.
Should there be any tendency to hardness in the material used for
filling, it may be found advisable to run the thread over a plush pad on
which has been applied a light application of cocoanut oil, but great
care should be exercised not to overdo this as there is nothing so
hurtful to rubber goods as oil.
The quills should only be of sufficient length to allow for uniform
delivery from the shuttle without dragging at the ends. To assist in this
elongated shuttle eyes are preferable to round ones, so as to shorten the
angle at which the filling leaves the quill when running from the extreme
end. Thumb bits should be so adjusted that the delivery is uniform from
start to finish. The quill flanges should not lie flat against the
sides of the quill opening, but should be pointed at the ends so as to
reduce the friction. Quill wires should be of hard tempered steel and be
perfectly straight at all times. When it becomes necessary to run narrow
goods in wide spaces, recoil springs should be provided to gather up the
loose filling.
CARE REQUIRED IN FINISHING
The finishing of elastic fabrics is a process which demands great care,
and has to be taken into calculation from the beginning of the web
construction. Calculations must always be made as to what effect heat,
moisture and sizing will have upon the covered up elastic threads,
confined as they are in a multiple of small cavities and under high
tension. As soon as the softening influence of heat and steam operate
upon the covering of cotton yarn which confines these threads, the rubber
strands begin to assert themselves and contraction at once takes place.
To what extent this can go must be predetermined in fixing values, and a
certain degree of uniformity of contraction arranged for.
Webs which are perfectly flat and straight when taken from the looms are
liable to be transformed into unshapely products and completely ruined
by unsuitable finishing. For instance, take a web with a twill center
and a plain border which is apparently flat and satisfactory at the
loom. The effect of heat and steam upon such a web will be to contract
the soft woven center more than the harder woven plain border, which
will cause the web to be long-sided and curl. Such a condition must be
anticipated in the construction of the web and provision made to offset
its occurrence. Sometimes it must be met by a change in the size of
some of the yarns used, or number of threads employed at given points,
or perhaps added gut threads must be introduced to stop contraction in
certain places. It must always be remembered that we are dealing with
a very much alive element when we are finishing rubber goods, and that
unexpected results may at any time arise.
FINISHING MACHINES
Finishing machines vary both in design and capacity, but the general
principle is the same in all. A series of drying cans are arranged
for the application of the sizing mixture. Some machines are laid out
horizontally and some are upright. In the longitudinal layout the
machines are more easily accessible in their different parts and under
better control, while the upright machines are more compact and occupy
less floor space. Fig. 3 shows a horizontal machine of the latest
type. It has a drying capacity of eleven cylinders, 24 inches wide, 36
inches in diameter, allowing for a web contact of about 100 feet. These
cylinders are arranged in two decks so as to economize in floor space.
The goods first pass through a pair of independently driven circular
brushes, fixed at the feed end of the machine, to clear them from lint
and dirt before being steamed and dried. They next pass between two pairs
of nip rolls between which are fixed the steaming and sizing attachments.
The goods pass through dry high pressure steam which is confined in
a steam chest. They pass into and out of this chest through slots
underneath the cover. A trough carries the condensed steam away from the
goods and prevents dripping, otherwise they would be spotted.
[Illustration: Fig. 3.—Narrow Fabric Finishing Machine]
The steam pressure must be carefully controlled so as to get uniform
shrinkage of the goods. The steaming process softens the cotton, and the
rubber threads, which are under considerable tension, gradually creep up
and contract the goods. The steaming also makes the web more absorbent
and thus prepares it for the size bath, through which it is passed under
submerged brass rollers. The size is kept at a uniform heat by steam
heated copper coils. The web then passes through the second pair of nip
rolls, which are worked under pressure so as to squeeze out the size
before the web reaches the drying cans.
ALLOWANCE FOR CONTRACTION
The first of the dry cans is usually covered with cloth, so as to absorb
any size which may remain on the surface of the goods and allow it to
penetrate by further softening. As the goods continue to pass over the
hot cans a gradual process of contraction takes place. This contraction
is provided for by a corresponding regulation of the speed of the cans.
Intermediate expansion pulleys are provided for this purpose, so that
the speed adjustments can readily be made to meet the requirements of
different kinds of web.
The two pairs of front rubber nip rolls are likewise independently
driven, so as to provide for the shrinkage which takes place at the steam
box and size bath. At the delivery end of the machine the goods pass
through a set of nip rolls which are belt-driven from cone pulleys, so as
to be able to deliver the goods at the speed they leave the last drying
cans. From these last nip rolls, which are fixed quite high, they drop
into receiving cans or boxes.
Ten to twenty-five strips running side by side are finished at one time.
Adjustable guides are provided at different places on the machines to
keep the goods running in proper position. The speed of the machine is
usually governed by a Reeves transmission, and the delivery of the goods
ranges from 10 to 15 yards per minute, according to the requirements of
finishing. Three inches per yard is generally allowed for shrinkage,
but this again is determined by the goods. Neglect at any point in this
process may so interfere with the calculated shrinkage that values and
costs are materially changed.
New patterns and grades should be tested for shrinkage as soon as the
goods come from the loom, as short lengths made in sample looms are not
at all times reliable. Frequent tests are also advisable to see that
original conditions are maintained, as changes made by heat, steam and
speed are always liable to occur.
The immersing process is used mostly for single cloth garter webs. Double
cloth webs having a warp pile on the face are sized on the back only.
Exceptions are made on double cloth white webs used for the corset trade,
which are bathed with a very light size and often tinted in this bathing
process to the desired tone of white to match the cloths they are to be
associated with. Where the goods are sized on the back only the effect of
this has to be considered when they are constructed, and provision made
to maintain a proper balance under such conditions.
In frilled webs the elastic portion only is sized, so as not to interfere
in any way with the soft flutings of the frill. This is done by guiding
each strip over narrow pulleys which are run through the size bath. The
size accumulated on these pulleys is absorbed by the web passing over
them.
ACID IN GOODS
The requirements of the trade are so varied, and the types of web so
numerous, that no formula for size is suitable for general use. Care must
be taken, however, to avoid any sizes containing acids. Results from the
use of such preparations may seem excellent at the machine but later on,
when the goods are made up and come in contact with metal parts, the
metal is quickly tarnished, and the result may be heavy claims for damage.
It may be well to note here that the sulphur used in the process of
vulcanizing the rubber has the effect of blackening the copper cans
and the rolls over which the goods must pass. This can be effectively
prevented by having the cans nickel plated, thus doing away with much
risk of dirty goods, and of constant scourings and washing of the
different parts.
[Illustration: Fig. 4.—Narrow Fabric Singer]
Provision should be made for sufficient depth in the sizing pans so that
they will hold a liberal supply of size. Replenishment should be made at
regular intervals and the heat maintained at a uniform temperature to get
satisfactory results. It is advisable to make provisions to travel the
web over the top of the machine for a distance after immersion in the
size bath, and before it strikes the hot cans, so as to allow for proper
absorption of the size.
All these details are best worked out by experience. Webs are generally
fed into the machine from racks after being properly wound up, and
great care must be taken to avoid any variable tension on the webs when
entering the machine.
On lisle webs, a process of gassing or singeing takes place prior to
finishing for the purpose of removing any fuzz or fibre from the goods.
Fig. 4 shows a gassing machine used for this purpose. It is run at a high
rate of speed and several strips are gassed at once. When the machine is
running the flames are close to the web, but upon the stopping of the
machine the flames are carried away out of contact. In gassing white and
colors, great care must be exercised to have the gas mixture correct and
free from any carbonizing effect on the goods.