The Knitting Action of the Single Needle Bar Raschel Machine

The Needle-bed of a Knitting Machine

The needle-bed of a knitting machine is made up by the needles. As we said before, the needles can be all fixed on the same needle bar (picture 14) or can be driven individually in a grooved plate, according to the type of knitting machine. All knitting machines can be equipped with one or two needle-beds, according to the model.

Picture 14 - A needle bar with spring beard needle

                                     

                                   Picture 15 - The needle-bed of a flat knitting machine

The needle-bed of a knitting machine can be flat (picture 15) or circular (picture 16). It is made up of a steel body provided with grooves where the needles with hook and butt turned upward slide. The milled grooves guide the needles during the knitting process.

  Picture 16- The needle-bed of a circular knitting machine

The needle-bed is characterised by two elements:
- the operating width
- the gauge

The operating width is the maximum working area and varies according to the type of machine (picture 17): for example in a flat-bed machine the operating width is the distance between the first and the last needle while in circular knitting machines the operating width is the needle-bed diameter.

The gauge is the population of needles on a certain length of bed. The English Gauge is the number of needles included in an English inch, that is to say how many are included in 2.54 needle-bed centimetres. From a conceptual point of view, the English inch is measured from the centerline of a needle but usually it is the distance corresponding to 1 inch, measured from one side of the needle to the same side of another needle within 1 inch. For example: if we start from the right side of the first needle we will have to reach the right side of the last needle. The gauge refers always and only to one of the two needle-beds. The English gauge is indicated with a capital E and is used for all the weft knitting machines and warp knitting frames.

There are also other types of gauges used for other machines and specifically:

1. The English Raschel Gauge for Raschel looms is indicated with the capital letters “ER” and refers to the number of needles included in 2 inches, that is to say in 5.08 centimetres;
2. The GG Gauge is indicated with the capital letters GG and refers to the number of needles included in 1.5 inches, that is to say in 3.81 centimetres. This gauge is usedfor flat-bed full-fashioned machines and for English circular machines.
3. French Gauge is indicated with the Gros symbol and refers to the number of needles included in 1.5 French inches, that is to say in 4.16 centimetres. It is used for loopwheel circular machines.

  Flat needle-bed width                        Circular needle-bed diameter

Basic Knitting Elements of a Circular Knitting Machine

NEEDLES

The needles are the most important stitch forming elements. They are displaced vertically up and down and are mounted into the tricks or cuts of the knitting cylinder.
There are three types of needles namely:
1. Latch needle
2. Spring bearded needle 

3. Compound needle.

We can divide a needle into three main parts:
A. the hook, which takes and retains the thread tube looped;
B. the hook opening and closing device, that allows the hook to alternatively take a new thread and release the previous one;
C. a system allowing the needle to move and form the loop.

 

1=Butt,2=Butt height,3=Back shank,4=Stem,5=Crimp,6=Groove,7=Cheek,8=Hook,9=Hook width,10=Latch,11=Rivet 

                                                                     Fig: Needle

Sinker

The sinker is the second primary knitting element. It is a thin metal plate with an individual or a collective action operating approximately at right angles from the hook side of the needle bed, between adjacent needles.

1=Butt,2=Butt breadth,3=Height of shank,4=Buldge,5=Neb,6=Length of neb,7=Throat angle,8=Sinker platform height,9=Breadth of lower shank,10=Clearance,11=Throat

       Fig: sinker.

CAMS

The knitting cams are hardened steels and they are the assembly of different cam plates so that a track for butt can be arranged. Each needle movement is obtained by means of cams acting on the needle butts.

The upward movement of the needle is obtained by the rising cams or clearing cams. The rising cam places the needle at a certain level as it approaches the yarn area. Cams controlling the downward movement of the needles are called stitch cams.

Fig: Cams

Knitting cycle of a single jersey latch needle machine

The knitting action of a latch needle and holding-down sinker during the production of a course of plain fabric.

Fig. Knitting cycle of a single jersey latch needle machine

(a) Tucking in the hook or rest position. The sinker is forward, holding down the old loop whilst the needle rises from the rest position.

(b) Clearing. The needle has been raised to its highest position clearing the old loop from its latch.

(c) Yarn feeding. The sinker is partially withdrawn allowing the feeder to present its yarn to the descending needle hook and also freeing the old loop so that it can slide up the needle stem and under the open latch spoon.

(d) Knock-over. The sinker is fully withdrawn whilst the needle descends to knock over its old loop on the sinker belly.

(e) Holding-down. The sinker moves forward to hold down the new loop in its throat whilst the needle rises under the influence of the upthrow cam to therest position where the head of the open hook just protrudes above the sinker belly.