CIRCULAR KNITTING
Knitting machines are divided into two classes according as they produce
fabric in flat portions or in circular shape. In the methods of stitch
formation already described the courses of loops are constructed in a
flat piece, whilst the circular machine makes its fabric in circular
form. This system of fabric production has many advantages over the
plain width fabric and is indispensable for various branches of the
hosiery trade. In seamless articles such as hose and half-hose it is an
advantage to have them worked circular as this fits the shape of the
body part where they have to be worn. Also large quantities of fabric
are expeditiously worked on the circular frame with big diameter head,
these lengths being often suitable for making into articles such as
nightdresses where the circle of fabric may be used for the body part.
The great bulk of fabrics made on large diameter circulars are intended
for the cut-up trade, and they are so made because of the great
advantages possessed by such frames in point of speed. In flat rotary
frames where the work is made by an alternating motion of the
thread-carrier from side to side a principle of motion is utilized which
has a certain jerkiness as characteristic. With the circular principle
of motion there is an entire absence of jars and jerks in working, the
movement being steady and accurate, whilst the addition of eight or more
feeds to a machine makes an enormous production possible. One of the
most easily understood forms of this type of motion is incorporated in
the well-known Griswold type of circular knitting machine used still in
considerable numbers in one or other of its modifications for the
footwear trade. An illustration of this class of knitting machine is
shown in section in Fig. 50, which is so arranged as to give a side view
of the cylinder which makes the plain work and the dial as used for rib
work. The machine is constructed in a circle which for men's half-hose
is about 4¼ in. in diameter for a normal size, and the upright cylinder
marked C is fitted with grooves cut according to the set of the article
as it is fine or coarse. An average set of machine is 84 needles in the
4¼ in. diameter, but there are as few as 64 in the cylinder for the
coarse varieties, and up to 144 for fine gauges of footwear. A section
of the dial or ribber, as it is often called, is shown crosswise at D
with the cams at CB1. The cylinder needles are indicated by CN whilst
the dial or ribber needles are marked DN. The thread-carrier is shown on
the right by TC, whilst the thread is recognized by the letter T.
_Movement of the Parts._—The upright cylinder receives its rotatory
movement by means of a handle at the side which operates the bevel
gearing to drive the thread-carrier and the set of cams. The action of
the cams is to give the needles their up-and-down motion in loop
formation, they move round to work on the needle butts in succession,
pushing them up so that the hooks receive the thread from the carrier,
and drawing them down again so as to discharge and knock over the loops.
The thread-carrier and the cams are made to revolve together by the
turning of the machine handle, or in the case of power machines this
motion proceeds from the drive of the frame. The machine may be worked
without the dial, using the cylinder needles only for knitting, in which
case plain stitch fabric is produced as would be required for a plain
hose article. When ribbed work is needed the dial or ribber needles are
set in connection with the upright cylinder needles and are made to
rotate with the cylinder so that the dial needles share the thread with
the cylinder needles. The process of feeding the thread to both sets of
needles is clearly illustrated at the right-hand corner of Fig. 50,
where the thread T is seen to be proceeding through the eye of the
thread-carrier TC, when part of the thread is taken by the cross needle
issuing from the dial and part taken by the upright needles working in
the cylinder. The dial needles discharge their stitches towards the
right, whilst the cylinder needles throw their stitches over to the
left, and this alternation in direction of the stitch discharge is
responsible for the ribbed effect in the fabric. The ribber needles
radiate from the centre of the dial outwards, whilst the cylinder
needles all stand parallel to each other in an upright circle. The
fabric F proceeds down the centre of the machine, as shown, and is
maintained at the correct tension by suspension of weights in the hand
machine, whilst for the power frame we have an automatic motion for
winding up the fabric as it is produced.
[Illustration:
FIGS. 50, 51 and 52
]
_Stitch Formation._—The principle of stitch formation may be understood
from an examination of Fig. 51, which gives a view of the type of cams
found inside the cam box of the hand machine. Except where it is
required to knit the needle rests on what may be termed the normal
ledge, and it is only moved from this position when the cams reach it to
make it knit. The normal ledge is indicated by L and L1, and whilst the
needle is resting on this part of the platform no motion can result. To
form the stitch the first stage is to have the needle knocked above the
general level of the needle hooks to catch its share of the thread as it
is being fed into the needles, and this push-up is given by the small
triangular-shaped cam marked PC which raises the needles just
sufficiently above the normal height to receive their share of the
thread from the carrier. This done, the needle is at once operated upon
by the knitting cam KC, which is of the shape shown so as to draw down
the needle for the discharge of the loop. The butts of the needles N are
depressed by the knitting cam KC, and when they have reached their
lowest extremity N they have discharged their loops completely. The part
M of the cam causes the needles to rise once more into their normal
inoperative position, where they remain until the cams swing round to
them again to resume the knitting operation. On the right of Fig. 51
will be noted a push-up cam in a dotted position PC1, and it should be
explained that this is for the case of reciprocal knitting such as is
required in making the heel or the toe of an article of hose. In this we
operate only one-half of the needles in the cylinder, and in so doing
cause the cams to move from side to side in an oscillatory fashion. When
the cams are rotating in one direction push-up cam PC1 operates the
needles, and when the direction of knitting is reversed PC gives the
needles their upward thrust to receive the yarn. From Fig. 51 it will be
clear that the depth of stitch drawn by the needle depends on the
adjustment of the knitting cam KC, and the lower this is set the longer
will be the loop drawn through. If the loop is required shorter so as to
accommodate a larger number of courses per inch, the knitting cam is
raised in its adjustment so that a shorter stitch is the result. The
dial needles have a corresponding arrangement by which the needles are
drawn farther in to make a longer loop and for a shorter loop are not
pulled inwards to the same degree.
_Making of a Ribbed Sock._—Fig. 52 gives a view of an ordinary type of
sock where the various sections are marked as they are produced on the
machine. A start is made with the rib top marked R which in this case is
1 and 1 rib, that is, one upright needle in the cylinder for every
needle in the dial or ribber, and when all these are in operation at the
same time 1 and 1 rib work is formed on the power stocking-knitter.
Before beginning the rib top proper it is usual to make what is termed a
welt which consists in working a number of courses in the upright
needles only and letting the ribbed stitches draw round so as to give a
finished appearance to the edge. On reaching the end of the rib top it
is necessary to change the needle arrangement for making 3 and 1 rib,
and in the case of the power-rib stocking-knitter every second needle in
the upper ribber cylinder which is in the same plane as the lower one is
made to slide into the lower cylinder, that is, we have three needles in
the lower cylinder for every needle in the upper one. The 3 and 1 rib
continues for the leg portion, as shown by Fig. 52, when arrangements
require to be made for the heel-which has to be in the plain stitch and
continued for the sole of the foot and round the toe. To effect the
plain stitch for the heel, the front half of the dial needles are made
to slide into the lower cylinder and fashioning for the heel is soon
commenced. This is brought about by reducing the needles in work at each
side one at a time until only about twelve needles are left in
operation, when the process is reversed and the needles again brought
into knitting position at each successive course until the full
complement is available. This action gives a nicely-rounded pocket for
the accommodation of the heel, and at the same time it is usual to
introduce some form of reinforcing thread known as splicing, which has
the effect of considerably increasing the period of wear of such
articles. The plain stitch introduced for the heel is continued for the
sole, where the top of the foot A is worked in rib stitch and the under
portion B plain, as indicated in the diagram. When the foot has been
worked in this manner to its full length, the reciprocating motion is
repeated for the making of the toe exactly as for the heel, and several
extra courses are inserted so that one article may be kept separate from
another, and the next sock is worked exactly as the last. On the modern
automatic rib sock machine about seven dozen pairs of men's socks can be
produced by a single machine in a working day of eight hours, and as one
girl can mind a set of half a dozen machines, it will be seen that the
cost of production is infinitesimal when compared with hand-driven
machines or with the hand stocking-knitter. One heavier item in the
upkeep is the outlay required for a skilled mechanic, who is most
essential if the machines are to be maintained in thorough working
order, and this expense is proportionately the greater if the
manufacturer has only a few machines in this department. It is essential
to instal a series of machines of adequate scope of gauge and fineness
to warrant the employment of a skilled mechanic who can repair and keep
them in constant working order.
_Full-fashioned Hosiery._—In addition to the large and important branch
of the footwear trade which is devoted to the making of plain and ribbed
articles devoid of seams and which comprise a large and important
section of the knitting industry, we have other systems such as the
full-fashioned hosiery trade which produce varied types of footwear. For
full hose the length is greater, and as it has to cover the leg of the
wearer right over the knee, it requires to be shaped to the fit of the
individual. In the cheaper classes of hosiery an effort is made to
introduce a diminution in the width of the leg towards the ankle by
means of boarding, that is, the stockings are made uniform in width till
nearly the ankle except for any small contraction which it is possible
to effect by tightening the tensions. The woollen articles are stretched
on boards carved to the shape of the leg and when dried in a heated
chamber the natural plasticity of the wool enables the articles to take
up the shape they have been stretched into, the wide portion of the leg
stretches, whilst at the narrow portion the width contracts. Obviously
this device cannot long stand the exigencies of wear, and after a short
period of service the lower leg portion begins to widen and the result
is most untidy. When one comes to consider the great trouble involved in
making an article true to shape, it will be realized that such
stratagems of quick manufacture mean a considerable saving of time.
As the name implies, full-fashioned hosiery is worked on the knitting
frame in flat pieces which are afterwards seamed or joined together to
form the article as required. For a full-fashioned hose in plain stitch,
a rotary frame of the Cotton's Patent type is employed, and they are
made with two articles in one normal division of the frame, that is, in
a 12-at-once machine, for garment size we should be able to make
twenty-four articles of hose at one and the same time. The leg is made
uniform in width right down to the calf when narrowings are performed
according to the rate of diminution required, but it is when the heel is
reached that greatest labour is expended. It is necessary to work the
heel in two sections at each side, and the foot sole is worked on to
these pieces for the lower portion, the upper part of the foot being a
continuation of the leg and the whole is secured by a seam along each
side of the foot. By this system of manufacture it becomes possible to
make a much more roomy and capacious heel than is general on the
automatic seamless machine, for it can be made square-shaped and of any
convenient size by enlarging or contracting the heel portions.
This method of manufacture is termed the English heel, but there is
another system known as the French heel which is also largely adopted
for certain classes of goods. The real test of these articles is to note
the seam, which in the English foot always occurs along each side of the
foot and down the back of the heel. In the case of the French foot the
seam occurs along the centre of the sole of the foot which is obviously
an awkward arrangement from point of view of comfort. The French style
of foot is often employed for articles which have clocking or
embroidered patterns on them, whilst there is also a saving of time in
the process of making. The upper and lower portions of the foot are made
in one width and afterwards folded over with only one seam along the
middle of the sole of the foot, whilst in the case of the English foot
the seam is double and occurs along each side of the foot. It is
interesting to be able to distinguish between these various methods of
making hosiery; for the article in which no effort is made to fashion
the leg on the frame the marking indicative of narrowings for the leg
will be entirely absent, and in their place will be the temporary local
thickening of the fabric due to the increase in the number of stitches
at that point. In the case of the full-fashioned article, the shape will
be gradual and symmetrical, for the French foot only one seam will be
found along the centre of the foot, whilst in the English variety a seam
will occur at each side.