_Head Motion Looms and Dobbies for Making Fancy Effects—Tying Up
Harness—Construction of Loom Webs, Lisle Webs, French Web or Railroad
Weave and Cable Webs—Making Good Selvages and Preventing Long-Sided
Effect_
So far we have mentioned only plain looms, or those limited to the
capacity of eight or twelve pick cams. Before we consider any of the
varied constructions relating to elastic webs it will be well to speak
of fancy looms. There are different types, adapted to a wide range of
fancy effects, but the fancy loom most generally used is what is known as
the chain head, an example of which is shown at Fig. 1. Such looms are
usually of 18 and 24 harness capacity, and are operated by a figure chain
of the length required to produce the desired figure. Chains are made up
of a series of bars, one bar operating with each pick of the loom and
having on it space for a roller or sinker for each harness to be operated.
Wherever a roller is placed on the bar, the corresponding harness will be
raised, and wherever a sinker is used, the corresponding harness will be
dropped. A series of rollers following each other will hold the harness
up, and likewise a series of sinkers following each other will keep the
harness down, thus maintaining at all times an open shed.
THE SHEDDING OPERATION
The shedding operation is very simple. In the fancy head there are two
cylinders, each of which has gear teeth running the entire length. These
cylinders operate continuously in opposite directions. The teeth of the
cylinders do not go around the entire circumference as will be noticed on
the upper cylinder shown in Fig. 1, but there is a blank space provided
so as to allow for the engaging of the gear wheels brought into position
at the right time as the cylinders revolve.
Between the two cylinders are vibrator gears, one for each harness, and
to these gears are attached arms which are connected with the different
harnesses. These vibrator gears can be thrown into position by the chain
rollers or sinkers, so as to come in contact with the teeth of either the
upper or lower cylinder, and are so timed that they take their position
at the moment when the blank part of the cylinder presents itself. A
vibrator gear engaging the upper cylinder is turned so as to lift the
harness connected with it, while a vibrator gear engaging the lower
cylinder drops that particular harness. The harnesses stay in their
relative positions until the chain calls for another change.
Both cylinders and engaging gears are made of hard chilled steel, so that
wear and tear by hammering at the time of engagement are reduced to a
minimum. To further soften the engagement, the speed of the cylinder is
controlled by elliptical driving gears, which reduce the speed of travel
just at the moment when the engagement takes place.
The timing of the various movements of the head is so well controlled
that there is little risk of any part failing to maintain proper
relationship with the other parts. But in the event of any accident or
breakage occurring which interferes with the free motion of the head,
such strain is taken care of by a soft pointed set screw on the head
driving shaft, which shears off and so prevents further serious damage.
The capacity of the head is such that by careful arrangement of figures
and repeats it is quite possible to make several simple designs to run
side by side in the same harnesses and this is often done. Of this we may
write more later.
[Illustration: Fig. 1.—Fancy Loom for Weaving Narrow Fabrics]
[Illustration: Fig. 2.—Double Index Dobby]
[Illustration: Fig. 3.—Overshot Dobby]
THE OVERHEAD DOBBY
A popular machine for light fancy warp figures is the overhead dobby
shown at Fig. 2, which may be used as auxiliary either to the plain
cam loom or the fancy head loom. It is placed on a well braced, rigid
frame and built as high as convenient so as to reduce the angle of the
harness strings. It is driven directly from a two to one shaft, which
may be either underneath the loom or at the end, and is connected with a
threaded adjustable rod, which is attached to a slotted lever and can be
adjusted to govern the depth of the dobby shed.
It is customary to put two of these dobby machines over each loom, but
having only one main drive the two machines are coupled together and
work in unison. Such an arrangement has the double advantage of a less
acute angle at the harness tie-up, and also affords facilities for a
distinctly different pattern on either half of the loom. It minimizes
the risk of the harness threads cutting into the compart boards, and
prolongs relatively the life of the dobby harness. Furthermore it allows
for a straight tie-up on either machine so that there is no limitation
to the length or character of the design, as is often the case where two
patterns are run together on the same machine, or where point tie-ups are
used, as would very likely be necessary if only one machine was installed
to cover different designs on both halves of the loom. As we have
previously stated it is not advisable to limit capacity for the saving of
a few dollars in the initial cost.
OVERSHOT DOBBY
Another type of loom employed in the making of fancy goods is what
is known as the overshot loom. It is used for the introduction of a
silk weft figure effect, and is probably the most pronounced form of
elaboration introduced. It differs from the old rise and fall method in
the economy of operation. The overshot continues to weave the body of the
goods right along while the auxiliary shuttle is putting the silk figure
in at the same time. Not only is it economical in the respect of greater
yardage, but the method employed in binding the figure limits the use of
silk to the actual figure displayed, and does not carry the silk, which
is the most expensive material in the fabric, to the extreme selvage at
every pick, as is the case where the rise and fall method is employed.
In the overshot system a specially designed dobby, shown at Fig. 3, is
used for operating the lightly weighted threads of the binder warps. Two
pairs of knives are employed, one of each pair operating far enough to
raise the threads used in the binder warp to the level of the top main
shed, while the other one of each pair carries the threads which are used
for figure purposes to a higher level, so that the overshot shuttle may
pass under them. This occurs every alternate pick of the loom, the body
shuttle making two picks while the upper or overshot shuttle makes only
one.
In levelling the harness, setting or timing of the loom, and making the
shed for overshot work, the plans followed are identically the same as
in ordinary single shuttle work, as the upper shuttle and upper shed are
distinctly auxiliary and subordinate to the main shed. The binder warp,
being necessarily but lightly weighted in its relationship to the upper
and lower cloths it is binding together, allows for the figure threads
to be strained out of their normal position, so that the upper shuttle
may pass under them. In order to conform to this strained position of the
binder figure threads, the upper shuttle must be acutely pitched downward
at the nose so as to get a good clearance, and thus avoid any binding
in its passages through the shed. This peculiar downward pitch of the
shuttle is very important and cannot be over emphasized. It is shown in
Fig. 4.
The overshot dobby is so constructed that a different set of draw knives
operate on each alternate pick of the loom, one on the binder lift and
the other on the rubber lift. This not only allows for a silk figure made
with the shuttle but affords facilities for the introduction of a warp
figure also, a combination which can often be made very effective, as
shown in Fig. 5.
[Illustration: Fig. 4.—Showing Auxiliary Shed and Pitched Shuttle as Used
in Overshot Work]
IMPORTANCE OF DOBBY HARNESS
Too much importance cannot be attached to the rigging of the dobby
harness. A 30/9 ply linen cord is desirable and a lingo of about 16 to
the pound. After deciding on the character of the tie-up required, and
when the harness has been threaded in the compart boards, the lingoes
should be looped on the strings, and then left to stand and settle for
a couple of days before leveling. It is better still to run the dobby
machine for a few hours, lifting all the harness and then dropping them,
so as to settle the strings and take out any kinks or loose places which
are bound to exist in a highly cabled linen cord of this character.
The labor required in the tying up and leveling of a string harness
suggests the advisability of great care in determining the tie-up to be
used, so that changes of pattern can be made easily without involving
changes in the tie-up. In order to prolong the life of the harness, in
the adjustment of which so much time and care must necessarily be spent,
it is advisable to apply a dressing of boiled linseed oil, which should
be thoroughly worked into the strings by running the harness for several
hours, using one and one change cards. This should be followed by a
dusting of talc or soapstone, which will add much to the smoothness of
the finish.
To reduce the friction of the strings which operate in the several
outside compart boards, where the strain and wear are particularly acute,
and also to prevent the strings from cutting into the boards themselves,
it is good practice to fix strips of ground glass between the different
rows of strings, just above the compart boards. These strips of glass may
be threaded through drilled holes in the compart board frame.
CONSTRUCTION OF SIMPLE WEBS
Before enlarging further on details of fancy looms, it will be well to
retrace our steps and consider the construction of some of the simpler
forms of web, such as are made on what we have described as plain looms.
The webs best known, perhaps, are those such as are used for men’s
ordinary garter wear, and for cutting up to retail in the regular dry
goods and notions trade. They vary from one-quarter to 2 inches in
width. There are several distinct classes of these goods, the best known
of which are the loom webs, the lisles and the cables, all of which are
of single cloth construction, in which the filling is the main feature.
There are generally two cotton warps used in such goods, one of which
is commonly called the binder and weaves two up and two down, while the
other is called the gut or filler, and works with the rubber warp, one up
and one down. The selvages of these webs are made with the filling, which
passes around a wire at each pick, the wire remaining stationary while
the web is taken away from it in the process of weaving. An illustration
of a loom web of this character is shown at Fig. 6. The draft and cam
arrangement are shown at Fig. 6A.
[Illustration: Fig. 5.—Combination Warp and Shuttle Figure Produced on
Overshot Dobby.]
[Illustration: Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10]
It is customary in some factories to use only one harness to carry both
rubber and gut, inasmuch as the weaving of the two are the same and they
both go in the same cavity or pocket of the web. Where such a method is
employed there is always a tendency for the gut threads to get out of
their proper places, and to fall together in pairs at irregular points,
which will produce an objectionable “rowey” appearance in the goods. This
will be noticed more particularly in white and light colored webs.
[Illustration: Fig. 6A.—Harness Draft and Weave for Three-Quarter Inch
Loom Web]
[Illustration: Fig. 7A.—Harness Draft and Weave for One-Half Inch Lisle
Web]
[Illustration: Fig. 8A.—Harness Draft and Weave for Three-Quarter Inch
French Web]
[Illustration: Fig. 9A.—Harness Draft and Weave for Three-Quarter Inch
Cable Web]
In the harness draft shown, it will be seen that one harness is employed
for the rubber and one for the gut. It is thus possible to shed the gut
harness so as to open more than the rubber, having it travel both higher
and lower than the rubber harness at each alternate pick of the loom. By
this movement the gut threads will be kept in the desired position, and
at the same relative side of the rubber threads in each of the several
pockets designed to carry them both. If, from any unusual cause, any of
the gut threads get away from their proper places it is easy by this
arrangement of separation to lift the gut harness at any time, insert
a thread of cotton between the gut and rubber threads, and put them in
their proper places when commencing to weave again.
The weave employed in the making of webs of this kind, although of a very
simple character, involves a condition which does not favor a straight
well woven fabric unless great care is taken to offset troublesome
tendencies. The nature of the weave is such that at one pick the binder
harness changes, while on the next pick it remains open and does not
change, the rubber and gut harness changing only. The result of this
movement is such that one shed clears for the reception of the filling
much better than the other, so that at one side of the web the filling
will hug the edge wire, shown at W in Fig. 6A, while at the other side of
the web the failure to get a good clearance prevents the filling getting
so snugly around the wire. Therefore, as the web draws away from the edge
wire in the process of weaving, the tendency is for one selvage rubber
cavity to be small, while the other is large, which means that at the
open side there is a freedom for contraction of the edge rubber which is
not present at the other side, and a long-sided uneven web is the result.
MAKING A GOOD SELVAGE
To counteract this it is essential that great care should be taken to
get a good clearance of the shed. The shed should be timed as early as
possible, so as to give every particle of fibre on the warp a good chance
to separate and clear itself. When space permits, the front reed should
be set slightly over on one side of the reed space, so as to create a
little longer pull on the filling as it draws from the shuttle on the
open side, and correspondingly eases up the draw of the filling on the
other side. The warp stock used, however, may be of such a character that
the loose fibre on it makes even these precautions ineffective altogether
to counteract the trouble, and it may then become advisable to put in
a fine edge wire on the open side of the web to offset the creeping
tendency of the selvage rubber thread when contraction takes place after
the web comes through the press rolls.
The feature which is aimed at, and which is most desirable in the
appearance of such goods, is a clean cut prominent rib at the rubber
line, and the avoidance of a flat paper-like look and feel of the web
generally. The prominence of the rib varies, of course, according to the
size of the rubber thread used, and the binder warp employed in dividing
the same, but even the very best of conditions may be spoiled if proper
care is not taken to get all the prominence of rib possible. Use as fine
a binder warp as is practicable, compensating for any loss of weight or
excess of contraction by using a heavier gut, which again of itself helps
to fill in the rubber cavity and thereby lends additional prominence to
the rib. All the weight possible should be carried on the binder warp
up to a point of safety, and care should be taken to get a very easy,
uniform delivery of the warp from the beam so as to avoid any erratic
jerky movement of the warp lever.
The warp beams which are used on this delicate type of work should
be well balanced and true to center, and the flanges free from any
irregularity which would in any way interfere with the easy and uniform
operation of the warp lever.
The gut, which weaves in with the rubber thread, is used for the two-fold
purpose of giving additional body to the fabric and of regulating in a
measure the length of stretch in the goods. The more gut there is used,
the less becomes the power of contraction of the rubber warp, and the
shorter the stretch produced.
Aside from the fineness and body of the goods, the element of stretch
largely governs the market value of the fabric, so that good judgment and
great care must be exercised in the assembling of the different sizes of
yarns used. Weft, binder and gut all play their part in the governing
of the stretch, as also does the number of picks put in the goods. Any
excess of weight on the binder warp also materially reduces the stretch.
In fact, any one of these features, wrongly adjusted, may result in the
difference between the profit and loss.
In making the selvage of these goods a hard steel wire is used, around
which the filling passes at each pick. This wire, shown at W in Fig.
6A, is highly tempered piano wire, of the very best quality obtainable.
Sharpened to a needle point at one end, with a loop turned at the other
end, it is fastened at the back of the loom by a cord which has an
adjustable slip knot, so as to be able easily and quickly to regulate
the length of wire running in the web. It is then passed through a
harness heddle eye on the rubber or gut shaft, and through a reed space
next outside the selvage rubber thread. The constant wear of this wire
on the reed dent makes it necessary to have this dent of hardened steel
so as to withstand the constant wear of the wire, which is always being
crowded against the dent by the nipping action of the filling as it draws
against the wire in the process of weaving, and the repeated beat at the
same place in the dent at the weaving line. In any event, after a short
time the dents in the reed will be cut so that it becomes necessary to
frequently replace them with new ones, and for this reason it should be
so arranged that they can be easily and quickly removed from and replaced
in the reeds.
THE LISLE WEB
The lisle web, being perfectly plain, is similar in general character to
the loom web, except that it is made with high grade combed and gassed
yarns for the filling in place of cheaper stock used on the loom webs,
and is woven with four threads for the binder warp between each strand
of rubber, instead of two as in the loom web. The harness draft of the
one-half inch lisle web shown at Fig. 7, together with the weave, is
shown at Fig. 7A. The construction is as follows: Binder, 36 ends 80/2;
gut, 8 ends 40/2; rubber, 10 ends 32s; reed, 21 dent; picks, 78 per inch;
stretch, 75 per cent.
It will be seen that all the binder threads operate two up and two down,
but change at each pick in rotation, making the repeat every four picks
of the loom. In a weave of this character the changes of the harness are
distributed uniformly at each pick, thus making it much easier to get
uniform conditions on each selvage. It differs from the loom web in this
respect, where the alternating light and heavy pick has to be contended
with.
Like the loom webs, prominence of the rib over the rubber thread is the
main feature aimed at in the general appearance of the fabrics, and
therefore everything possible should be done which will emphasize this.
The binder warp must be of fine yarns, and the warp must be weighted so
as to cut the warp line down sharp and clear up to a point of safety,
being careful at the same time not to go to excess so as to narrow
in the goods or cause undue chafing of the rubber warp. The yarn most
generally used for filling is 26-2 comber and gassed high grade stock,
of about 15 turns per inch. It should be a well-rounded lofty yarn so
as to obtain all the covering property possible. It should be spun with
the utmost uniformity, as the slightest irregularity in the yarn will be
noticeable in the goods.
The dyeing and bleaching of the yarn used for filling is also of the
greatest importance. It is not an unusual occurrence to find otherwise
perfect goods made unmarketable as first class by the use of a filling
yarn which has not been properly processed. This faulty condition of
the yarn may be caused in a variety of ways; such as an irregular boil,
poor circulation of liquor in the kier, irregular drying, etc. Even when
the color appears to be perfect, poor processing will often prevent the
smooth running of the yarn from the shuttle, causing it to drag and
thus create irregular and crooked selvages which result in the repeated
breaking of the selvage rubber threads and ruin the goods.
The many difficulties of this character which were encountered when skein
yarn was more generally used for filling led to the introduction and
almost general use of warp yarns for filling purposes, inasmuch as the
method of processing the warp yarns gives results which are not nearly
so variable. Furthermore the long unbroken runs of thread obtainable by
quilling avoid the many knots which are present when using skein yarn.
Knots are unsightly and objectionable when appearing on the face of the
goods.
Chafed and broken edge rubber threads, however, are not always the result
of the conditions named, by any means, but may be caused by a variety of
other things. Not infrequently the edge wire may be weaving too long in
the web so as not to draw out freely. Sometimes it may be a bent wire
that causes the trouble, or it may be the rubber rolling around the wire.
Many times defects are caused by the edge wire having cut into the dent,
so that it has a file-like effect as the rubber thread passes by in
weaving. All these things require looking into, and when trouble comes
the cause should be found and not guessed at.
FRENCH WEB OR RAILROAD WEAVE
Another plain web which has attained considerable popularity, and which
is a kind of intermediate grade between the loom web and the lisle, is
what is known as the French web or railroad weave, shown at Fig. 8. In
almost all respects the general treatment of this web is the same as
already described, and it differs only in the draft, which is shown at
Fig. 8A. It allows for the use of a somewhat finer yarn than is generally
employed in the loom web, and the draft changes at every two cords, which
gives it a peculiar “rowey” appearance from which it derives the name of
railroad weave.
There is one feature associated with all these plain webs which it might
be well to speak of. The high tension at which it is necessary to work
the rubber warp, together with the light weight required on the cotton
warp and the crowding together of the picking, creates a tendency for
the goods to rebound at the front reed, accompanied by a backward and
forward sliding movement when passing over the rod at the breast beam.
This movement is liable to polish the goods, which is an objectionable
feature. To counteract this it is advisable to let the web pass over
a small, felt-covered wood tube, which revolves and responds to the
movement of the bounding web. In this way there is no friction to glaze
or polish the web and interfere with the bloom of the yarn. The same
polish will occur as the goods pass through the press rolls, unless they
are felt covered.
CABLE WEB
The most popular web now made up into men’s garters is what is known
as the cable web, shown at Fig. 9. With the pronounced prominence of
the two-dent rib, which gives it a character peculiarly different
from the plain web, it is well adapted to this class of goods. Simple
in appearance, it nevertheless requires special care to manufacture,
particularly when we remember that it is not unusual to be required to
make a finished stretch of not less than 100 per cent. The harness draft
and weave are shown at Fig. 9A. The construction is as follows: Binder,
34 ends 80/2; Gut, 24 ends 20/2; Rubber, 18 ends 28s; Reed, 20 dent;
Picks, 80 per inch; Stretch, 100 per cent.
The filling, floating across the wide spaces under which lie the rubber
threads in pairs, is very easily thrown out of place, the result of which
may be an unsightly seersucker appearance, as shown in Fig. 10, which the
process of finishing aggravates rather than corrects.
Trouble may manifest itself by the filling over the ribs opening up and
allowing the gut threads to prick through. To prevent this objectionable
feature it is necessary to use a good quality of moderately soft yarn
for the gut, not necessarily of high grade stock, but a yarn which is
uniformly spun and not at all hard or wiry. As these goods are being
woven and on full stretch, the gut threads, of course, are perfectly
straight and accurate in line, but when contraction takes place, to
probably one-half the former length, these heavy threads, which form
probably about 25 per cent. of the weight of the entire web, should bend
or fold uniformly and dispose of themselves in such a manner as not to
appear in any way on the face of the web, snugly housed away in the
several pockets or cavities. If the yarn composing these gut threads is
spotty or irregularly spun, this uniformity of fold inside the pockets
will be broken up and the appearance of the face of the goods is likely
to be marred by unsightly specks of cotton pricking through, which can be
both seen and felt.