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VASANT R KOTHARI has done Master’s in Textiles Technology from DKTE’s Textile and Engineering Institute,

Ichalkaranji (Shivaji University, Kolhapur), Maharashtra. He has also done Diploma in Export Management (Apparel

Export) from the Indian Institute of Export Management, and Garment Export and Merchandising Management

from NIFT, Bangalore. Presently, he’s working as an Assistant Professor in Department of Fashion Technology,

NIFT, Bangalore. (This is his ninth input from the series of articles in Knitting Views).

Purl fabric

The Purl fabrics are also known as link-

link fabrics. Purl was originally spelt ‘pearl’

and was so named because of its similar

appearance to pearl droplets. In purl, the

loops of one course are intermeshed in

one direction and the loops of the next

course intermeshed in opposite direction,

i.e. the alternate courses having face and

back loops. It means each wale contains

both knit stitches and purl stitches. This

differs from the rib fabric, in which the

wales contain either knit or purl stitches.

A simple purl fabric looks somewhat like

the back of a jersey knit on both sides of

the fabric. The simplest purl fabric is

Fig 9.1: The technical face of purl fabric

Fig 9.2: 1 x 1 purl fabric

Fig 9.3: Face and back side ofplain jersey fabric

known as 1 x 1 purl, in which one course

has all knit stitches and the next course

has all purl stitches. The cycle repeats on

the third course. A 2 x 2 purl knit fabric is

made with two courses of knit stitches

followed by two courses of purl stitches.

Fig 9.5: Knitting notation of purl fabric

Fig 9.4: Face side of the fabric

Crosssection

Back side of thefabric

KNITTING VIEWS/MAY-JUNE 2011/23

Fig 9.9: Interlock fabric structureFig 9.6: Circular and flatbed purl

knitting machine Fig 9.8: Purl needle transfer action

Production of purl fabric

Purl-knit fabrics are made on knitting

machines called purl-knit machines or links-

and-links machines. The purl knitting

machines are basically of flat and circular

types as shown in fig 9.6. The flat is having

two horizontal beds for needle movement

and central gap for fabric formation. The

circular type has two cylinders, one above

the other and thus referred as super

imposed cylinder machine. As stitches are

sometimes drawn to the front and

sometimes to the back, two sets of needles

are required to produce these fabrics. In purl

machines, however, rather than two distinct,

separate sets of needles, one set of double-

headed latch needles is used as shown in

fig 9.7. The two needle beds are in alignment

with each other. The double headed needles

move from one needle bed to the other, from

side to side of the knitted fabric as it is

produced, alternately making stitches on one

fabric side and then the other.

The purl-knit machines used to produce

purl knit fabrics are the most versatile

industrial knitting machines. These

machines can produce plain and rib as well

as purl fabrics. By selective programming

of needle motion, fabrics of all three types,

sometimes with unique design effects are

possible. Purl-knit machines are widely

used in the sweater industry.

Although extremely versatile, the purl knit

machines have the lowest rate of

production of all knitting machines.

The knitting action

Fig 9.8 shows the knitting action of a

flatbed purl machine which has tricks in

each of the needle beds. They are in line

with one another to enable the transfer of

purl needle from the control of a slider in

one bed into the control of a slider in the

opposite bed.

Position 1 shows engagement of the head

of the receiving slider with the needle hook

that was originally knitting from the

opposing bed. In position 2, the needle

has been moved to the centre, with both

sliders engaging the needle hook. The

sliders then start to move back, but the

slider in the back bed is pressed down by

a cam, so that front bed slider is freed from

the needle hook and the needle is

transferred to the back bed.

In position 3, the slider in the back bed has

control of the needle and it can be seen that

the yarn is fed to the opposite end of the

needle, when compared to that of position

1. Then the slider in the back bed has moved

the needle to knock over position to

complete the formation of the purl stitch.

It should be noted that a purl stitch is made

when a loop is formed by one hook and

then at the next course by the other hook

of the same needle, so that one course is

formed on the front bed and the next

course is formed on the back bed to create

a 1 x 1 purl structure.

Fabric characteristics

To identify a purl-knit fabric, fabric need

to stretch in its length direction. The

appearance of alternating rows of knit

stitches and purl stitches in the course

direction is evidence of a purl knit.

Generally purl-knit fabrics tend to lie flat

and do not curl as do jersey knits. Purl

fabric has same appearance in face and

back. It can unroved from either end.

Lengthwise extension is more as compare

to width wise and hence purl fabric

contract towards the centre in a course

wise direction. Thickness of fabric is two

to three times more as compare to single

jersey fabric.

The fabric is commonly used for children’s

wear and sweaters.

Interlock fabric

Interlock-knit fabrics are a variation of rib

knits made on the interlock machine.

Interlock is an interlocking of two 1 x 1 rib

structures in such a way that the face wale

of fabric “1” is directly in front of the

‘reverse wale’ of the rib fabric “2”.

Interlock has the technical face of plain

fabric on both sides, but its smooth

surface cannot be stretched out to reveal

the reverse meshed loop wales because

the wales on each side are exactly opposite

to each other and are locked together as

shown in Fig. 9.9. Each interlock pattern

row (often termed an ‘interlock course’)

requires two feeder courses, each with a

separate yarn that knits on separate

alternate needles, producing two half-

Fig 9.7: Double headed latch needle

Therefore, the cost per pound of fabric

produced is highest for purl knit fabrics.

Knitting machines for jersey knits have

the highest productivity but the lowest

versatility. Productivity for rib-knit

machines falls between those for jersey

and purl machines.

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Production of interlock fabric

Interlock is produced mainly on special

cylinder and dial circular machines and on

some double-system V-bed flat machines.

In interlock machine

• Interlock gating, the needles in two bedsbeing exactly opposite each other sothat only one of the two can knit at anyfeeder

• Both, the cylinder and dial beds shouldhave two types of needles viz., long andshort needles

• Alternate placement of long and shortneedles in both the beds is required

• The long needle of one bed should facethe short needle of the other bed andvice versa

• Two separate cam systems in each bed,each controlling half the needles in analternate sequence, one cam systemcontrolling knitting at one feeder, andthe other at the next feeder

• Needles set out alternately, onecontrolled from one cam system, the nextfrom the other; diagonal and notopposite needles in each bed knittogether

• Minimum of two yarns are required toknit one interlock course and hence aminimum of two feeders supply

• The knitting style is in such a mannerthat only long needles of dial andcylinder will knit with the first feederand only short needles of dial andcylinder will knit with second feeder

Fabric characteristics

To determine whether a fabric is an

interlock or a rib, spread the fabric width

wise, and view the fabric wales carefully

at the top edge of the cloth. If the knit

stitches are one behind the other, the

fabric is interlock. If the wales of knit

stitch alternate, the fabric is rib.

Interlock fabric is a reversible balanced,

smooth, stable structure that lies flat

without curl. Like 1 x 1 rib, it will not unrove

from the end knitted first, but it is thicker,

heavier and narrower than rib of

equivalent gauge, and requires a finer,

better, more expensive yarn.

It unroves from the course knitted the last.

The fabric becomes costlier due to

thickness and less production. Interlock

is used for outwear fabrics, often using

wool, acrylic and polyester yarns, while

cotton and polyester/cotton blends are

used for the production of underwear

fabrics. Interlock fabrics are also popular

for blouses, dresses, and dressy T-shirts.

Their dimensional stability and the fact

that they do not tend to easily stretch out

of shape contribute to these popular uses.

Interlock fabrics offer a smooth surface

for printing by both screen and heat-

transfer methods

In the next article, we would be discussingabout straight bar knitting machine.

(The Author can be contacted atwww.vasantkothari.com)

Fig 9.17: Interlock cam system

gauge 1 x 1 rib courses whose sinker loops

cross over each other. Thus, odd feeders

will produce alternate wales of loops on

each side and even feeders will produce

the other wales.

Fig 9.16: Graphic representation of two setsof needle on interlock knitting machine

Fig 9.15: Knitting notation of interlock fabric

Fig 9.10: Interlock fabric structure

Fig 9.11: Interlock fabric structure

Fig 9.12: Front view of interlock fabric

Fig 9.13: Back view of interlock fabric

Fig 9.14: Cross sectionview of interlock fabric