LATCH NEEDLE KNITTING
The latch needle is one of the indispensable instruments of the knitting
industry, as was abundantly proved during the war period when shortage
of needles threw large numbers of useful knitting machines into disuse,
whilst inferior needles accounted for a great drop in efficiency. There
is a great variety in form of the latch needle, but they are similar in
essential features. A sketch of a normal type is given in Fig. 8 where
the various parts are lettered thus: H = hook at the left extremity of
the needle, L = latch, S = stem or shank of the needle, B = needle butt
or heel, as it is often termed. The latch moves on a pivot from the
dotted position when it shuts the hook to the normal position when the
hook is open. The stem or shank varies in proportion of length according
to the class of machine in which it is employed, whilst there is also a
large diversity of forms of the needle heel or butt usually in the
direction of strengthening by adding extra metal to withstand friction
for large scale knitting.
[Illustration:
FIGS. 8, 9 and 10
]
_Loop Formation with Latch Needles._—The matter of loop formation is of
the greatest interest and importance in any study of knitting and is
shown in detail by means of a series of sketches, 1 to 5 in Fig. 9,
illustrating the operation at the various stages. This will be useful in
studying any knitting frame, for an apparently complex piece of
machinery may be quickly reduced to intelligible dimensions if the
observer has a grasp of the process of loop formation. All machines
using the latch needle, and they are many and varied, form their stitch
on exactly the same principle, and when this is understood considerable
progress has been made towards a thorough comprehension of the whole.
Sections 1 to 5 of Fig. 9 represent the successive stages in stitch
making, the needles being shown at the angle usually found in the flat
knitting machine of the Lamb type. In Diagram 1 of the series the needle
is shown in its normal non-operative position with the latch closed and
the loop M inside it. In all knitting a division must be maintained
between the old loop and the new yarn. In Diagram 2 the needle rises,
and in so doing the old stitch M opens the latch L and passes on to the
stem and the new yarn marked Y is in the act of being seized by the hook
of the needle. In Diagram 3 the needle is noted to have sunk lower in
position so that the old loop M closes the latch with the yarn Y inside,
and the old loop covers the latch as shown. This stage is termed the
"landing of the stitch" and in Diagram 4 the needle is noted to have
dropped still farther, so that the old loop is pushed over the needle
extremity and the new yarn drawn through the old loop M to form a
complete stitch. Precautions have to be taken in the machine mechanism
to have the old loop properly discharged over the needle end and the new
yarn completely drawn through. When this is complete the needle again
rises in its position as in Diagram 5, and in so doing the yarn inside
the hook moves downwards and opens the latch preparatory to a new course
of stitches.
Diagram 10 illustrates another important form of the latch needle known
as the double-headed needle as it has a hook at each extremity. This
instrument forms the basis of utility of a series of different machines
such as the rib hose frame and the pearl knitter. In these cases the
needle moves from one knitting stage into another discharging its loop
from the upper or lower hook according to the pattern of the rib or
pearl fabric.
_The Flat Knitter._—One of the best known machines using the latch
needle for its loop formation is the flat knitter which has an extensive
use in the knitting industry. The scope of work produced on the flat
knitter is truly wonderful and its great versatility of application
accounts for its immense popularity. In addition to plain fabric it can
make a large variety of fancy and reinforced stitches, which provide
great extension to the textural scope of the knitted fabric, allowing it
to be employed for a wider diversity of uses. Various colours can be
introduced in stripe formation, and with attachments of Jacquard
character or by the use of the double-headed needle the range of
patterns is further diversified. In regard to making full-fashioned
goods almost every form of garment can be made on it-pants, shirts, hose
and half-hose, coats, vestings, caps and gloves, are only a few of the
garments procurable. These can be fashioned by the worker to the
required form and an interpretation can be given to symmetry and style
of the human form. It has found an extensive application as a hand
machine to the making of seamless gloves being used by the most
progressive firms in the trade, and with the application of power it can
be adapted with considerable success to the making of goods in the bulk.
Hand machines are moderately priced so that to start a knitting factory
with such a plant is not a really formidable proposition, quite a
respectable equipment being procurable for a few hundred pounds; many a
prosperous firm owes its initial successes to the adoption of the flat
knitter and from this they have been able to launch larger schemes of
development in the knitting business. With new starters in this trade
to-day the flat knitting machine nearly always figures prominently when
there is lack of capital, and on this basis quite a sound foundation may
be laid.
A diagrammatic side view of the Lamb flat knitting machine is shown in
Fig. 11 where the foundation of the machine consists of two needle beds
or stages marked NB which are cut with tricks or grooves into which the
needles are placed as shown, each side being a duplicate of the other.
The needle is marked N and on it will be recognized such essentials as
the latch L, the hook H, the butt or heel B working inside the cam-box
CB. The thread T passes from its bobbin through the eye of the
thread-carrier TC and the needle is pushed into its position in the
cam-box by the spring marked S shown at the extremity of the needle
beds. The fabric is marked F and is noted to pass down through the
centre of the machine whilst at its extremity is attached a set of
weights which act as a means of drawing the fabric from the needle ends
as they are formed and if the needles are not being sufficiently well
cleared the amount of weight is increased. The weights have to be raised
from time to time to a higher position in contact with the fabric as it
is being worked.
[Illustration:
FIGS. 11, 12, 13, 14, 15 and 16
]
_Interior of Cam-box._—In this machine the principal functional part is
the cam-box CB, and from this the knitting action is imparted to the
needles. On this account a full view is given in Fig. 12 of the set of
cams used in the knitting machine made by Messrs. W. and J. Foster of
Preston. This set of cams is placed on each bed right and left and the
constituent parts are indicated as follows. Parts A and B are termed the
knitting cams, whilst the parts C, D and E combine to form what is known
as the knock-up cam. The part E is a fixture, whilst the needle path is
indicated curved, and through this the needle butts N are seen to be
passing. From the previously-given description of the making of loops on
the latch needle it should not be difficult to note that the cams
working on the needle butts in the needle path combine to raise the
needles to secure the yarn from the thread-carrier and, having received
the yarn, the needles are pulled down again to complete the loop by
drawing the new yarn through the old loop. The cams have a side-to-side
motion and pass over the needle bed from right to left and again from
left to right. In so doing they operate as follows: when the cam-box is
passing from right to left the needle heels are made to ascend the left
side of C and D and are drawn down again by the inside of cam B; when
the action is reversed and the cam-box is drawn from left to right, the
needle heels pass up the right side of cam D and are drawn down again by
passing along the inside of cam A, this alternate action being repeated
during the process of making plain work on the flat knitting machine.
_The Rib Stitch._—One of the outstanding advantages of the flat knitter
is the facility with which all kinds of rib stitches can be made, and
this is due to the arrangement of the needle beds, where the needles of
one side make their stitches in a direction contrary to those in the
opposite side. In making rib work both sets of needles in back and front
beds are in action at the same time; when the thread is supplied to the
needles those on the back rise equally with those on the front and
receive their share of yarn to form their own loops. Now it is clear
that the knitting action on the right-hand needle is opposite in effect
to that of a left-hand needle, this being expressed by the form of the
knock-over of the stitch; the right-hand needles discharge their
stitches to the left, whilst the left-hand needles discharge their
stitches towards the right. It is this combination of stitches
discharged in opposite directions which gives rise to the rib stitch
which is such a valued adjunct to all forms of knitted texture. This
difference in the direction of loop discharge causes one set of needles
to form back-fabric stitches whilst the opposite needles knit right-side
fabric stitches. The normal flat knitter has its two needle beds cut
one-and-one, as shown in Fig. 13, each bed has accommodation for the
same number of needles, these being set so as to pass up the centre
between the opposite series. This is termed a one-and-one arrangement
and the resulting fabric is known as the 1-and-1 rib stitch, one row of
loops in a vertical direction appears as wrong-side fabric stitches,
whilst the alternate rows work out as right-side fabric loops. This
explains the great increase of elasticity found in rib texture as
compared with plain because back-fabric stitches are always seeking the
back. In their normal position they virtually pass to the back, only
being visible on the face when stretch is applied in the width. The yarn
in crossing from face to back and _vice versâ_ undergoes a greatly
increased amount of intersection which contracts the whole fabric in the
width. This property is of the greatest practical value in garment
manufacture, because the extremities are usually finished with a few
inches of rib which enables the article to secure a firmer hold on the
limb or part of the body and thus serves to keep it in position. The rib
stitch is also an indispensable foundation of a number of textures which
weigh much heavier than the plain, as it enables a greater weight of
yarn to be inserted and the fabric is thereby increased greatly in bulk.
_Tension and Weight._—The texture of a fabric on any given knitting
machine can be varied according to a number of factors and of these
quite an important one is the length of loop drawn by the needle. An
examination of Fig. 11 will show that the needle beds on the flat
knitting machine are stationary and that the needles during stitch
formation draw the yarn over the top ends of the beds and obviously the
length of the loop will depend on the distance which the needle is drawn
below the edge of the needle bed, this distance being determined by the
adjustment of the knitting cams A and B shown in Fig. 12.
Cam B is shown in a dotted position raised so as to draw a shorter loop
and the length of the loop can be varied according to the height of
either knitting cams A or B within certain limits. If the loop is drawn
too long, that is, if the knitting cam is set too deep, the yarn may not
stand the strain and breakage will result; on the other hand, if the
loop is too short the fabric will appear stodgy in character.
_Patterns Produced._—This type of knitting machine has an extensive
range of patterns and textures which can be obtained and amongst the
first variations possible are those which result from an alteration of
the needle arrangement. The normal setting is to have one needle in the
front stage for one in the back stage, and these being arranged
alternately give the ordinary 1-and-1 rib stitch. This is shown in Fig.
13, where the upper row of small circles represents the needles in the
back bed or stage whilst the lower row gives those in the front stage.
The next, Fig. 14, shows the needles in exactly the same sett except
that the needles have been arranged to give the 2-and-2 rib pattern,
this being shown in diagrammatic enlargement in Fig. 16 at the side. The
third sett of needles given in Fig. 15 represents the arrangement for a
3-and-1 rib pattern where every third needle only is allowed to remain
in the front stage whilst the back stage retains its full complement.
From these examples it will be clear that by altering needles in this
way to any scheme a large variety of rib effects may be produced, nor
need the arrangement be uniform throughout the width, for the borders
may be in one pattern and the ground or interior in another. Novel
effects in imitation of lace work may also be produced by leaving a
needle out of one or other of the beds which makes an opening in the
fabric which can be manipulated to give an effect of a lace-like
character.
[Illustration:
FIGS. 17, 18, 19 and 20
]
_Manipulation of Knitting Cams._—Figs. 17 to 20 have been prepared to
illustrate the manner in which the cams are altered to give certain
well-known stitches in the flat knitting machine, and the construction
is the same as Diagram 12, with corresponding letters for the various
parts. On the left of the plate are arranged the cams as in the front
bed whilst the right-hand arrangement gives the set of the cams in the
back. In Fig. 17 the two beds are shown arranged for plain rib work
where both back and front needles are in action at the same time. Fig.
18 shows the cam setting in front and back beds for making the
well-known half-cardigan or royal rib which has played such an important
part as the stitch for cardigan jackets supplied to the troops during
the war period. It will be seen that on the front bed cam A is raised
into what is termed a tucking position, that is, the needles are pushed
up by D to receive the thread but are not drawn down far enough to have
their loops discharged over the needle ends. At the same time the cams
in the back bed are set for plain work and the needles there knit as
usual at every course. The real stitch, however, does not appear until
the direction of knitting is reversed, because the needles on the front
bed are again pushed up to receive a second thread and on this occasion
are drawn down the full distance by B to knock off the stitches. This
means that on the front bed stitches are formed in double threads after
every two courses whilst the back discharges its loops at every course,
which enables a much greater weight of yarn to be inserted into the
texture, making it more rigid and stable. The cams in Fig. 19 are
arranged in front and back beds to produce the polka or full cardigan
stitch, where double courses are worked on both front and back. This may
be clear if we consider the cam arrangements as illustrated moving first
to the right when the stitches on the front bed are "tucked" whilst
those on the back bed knit to the position of cam A. In reversing the
knitting to proceed to left, two yarns are drawn through in the front
needles whilst no discharge takes place on the back. In this way the
knitting occurs on the cardigan rib plan on both front and back needle
beds and the resulting fabric is much heavier in weight than
half-cardigan and when taken from the machine shows a strong tendency to
expand in width owing to the yarn seeking to take up a more expanded
position. The full cardigan stitch tends to be loose in character, the
weight of material is greatly increased over plain 1-and-1 rib, but
there is a lack of structural firmness and cohesion. In Fig. 20 the part
C of the cam comes into the picture as being necessary to give circular
work on the flat knitting machine. This can be drawn up out of action in
both front and back beds by a small finger lever, and an examination of
this arrangement will show that in going to the right the needles of the
front bed will knit as usual, but in reversing, as shown on the right of
Fig. 20, the needles pass completely under part D owing to the absence
of part C and knitting is not performed; the cam portion D is raised by
a spring to allow the needles to pass over the dotted position. It will
thus be seen that to make circular work we arrange the cams on the front
bed so that they will knit in going to right but miss in going to left,
whilst in the opposite bed the reverse holds good. Thus a course of
loops is made on the front with the back not knitting, alternated by a
course made on the back with the front not knitting. The fabric's being
worked from one yarn causes the loops to be joined at the edges and so a
continuous length of circular webbing is produced.