Introduction:
On crochet warp knitting machines, the warp chains are separate from the weft inlay and it is the latter threads that join the chaining wales to each other. Crochet machines, with their simple construction, ease of pattern and width changing, and use of individual yarn packages or beams provide the opportunity for short runs on coarse- or fine-gauge fancy and open-work structures and edgings, as well as the specialist production of wide fancy fabrics or narrow elastic laces. Very approximately, the knitting widths of crochet machine may vary between 16 and 122 inches (400 and 3100mm). Gauges, often expressed in needles per centimeter, are between 2 and 10 (E 5 to E 24). Machines run at speeds between 200 and 350 courses per minute (or much more on simple structures). Crochet warp knitting machine can process a range of filament yarns from 20dtex to 1000 dtex. Crochet machine is used to produce a huge range of warp knitted fabrics (warp knits) for clothing, household textiles and technical textiles.
Needles Used in Crochet Machine:
Different types of needles are used in crochet machine such as:
1. The patent or carbine bearded needle: It (A needle similar in shape to a bearded needle but with the beard shielded by a shoulder on the stem. The needle may only be lapped in one direction for the yarn to pass under the beard. A presser is not necessary as the needle is self-acting, the shoulder passing the loop on to the beard. It is mainly used in crochet-type machines) is used for fine structures and has a sideways crimped beard placed in a permanently-pressed position. Although warp threads can only be fed into the beard from the left, the old overlaps are automatically cleared and landed by the movement of the needle. It is still the most frequently used needle, achieving speeds up to 2500 rpm. Reduced machine speed and high needle wear make its use uneconomical for knitting single end cotton yarns.
2. Embroidery or Lace needles: They are carbine needles with pointed heads that can penetrate pre-woven structures to produce embroidery effects. The needles can be arranged for coarser gauges or for fancy set-outs, when the floating inlay threads may be cut to produce separated fringed edgings.
3. The compound needle: It patented by Muller produces less stress on the yarn during loop formation so a wider range of yarns can be used, and compound needles last up to six times longer than bearded needles.
4. Latch needles: It operates at uneconomic speeds and have a short life due to latch breakage.
Knitting Elements of a Crochet Machine
A single horizontal needle bar whose simple reciprocating action can be used to operate individually-tricked latch, carbine or embroidery needles. The patent or carbine bearded needle is used for fine structures and has a sideways crimped beard placed in a permanently-pressed position.
No sinkers; instead a fixed hold-back bar is fitted in front of the knock-over verge to prevent the fabric moving out with the needles.
Closed lap pillar stitches and inlay threads controlled and supplied as separate warp and weft respectively. Each needle is lapped from below by its own warp guide, which is clipped to a bar whose automatic one-needle overlap and return and underlap shog is fixed and is controlled from an eccentric cam whilst its upwards and downwards swing is derived from a rocker-shaft. The warp yarn is often placed low at the front of the machine.
The weft yarn, often placed above and towards the back of the machine, supplying the carrier tubes, which are clipped to the spring-loaded inlay bars. These bars are fitted above the needle bar and are shogged at the rate of one link per course, from pattern chains around a drum at one end of the machine. There are usually up to two warp guide bars and up to 16 weft inlay bars, which may be electronically controlled.
Special attachments are available for producing fancy effects such as cut or uncut fringe edges, pile, braiding (equivalent to fall-plate) and snail shell designs.
Crochet machines, with their simple construction, ease of pattern and width changing, and use of individual yarn packages or beams provide the opportunity for short runs on coarse- or fine-gauge fancy and open-work structures and edgings, as well as the specialist production of wide fancy fabrics or narrow elastic laces.
Knitting Action of the Crochet Machine
The knitting action or stitch formation to produce one course of loops on a crochet machine equipped with latch needles consists of the following stages:
- The weft inlay
- Clearing the warp overlap
- The warp overlap wrap
- Warp knock over and underlap
The essence of these stages consists in the following operations:
1. The inlay: Whilst the needle is withdrawn into its trick during knock-over of the previous warp overlap, the weft inlay tube is lowered. As it traverses in an underlap shog, the weft is laid below the level of the needle and on top of the warp thread that extends from its head to the warp guide.
2. Clearing the warp overlap: The weft tube rises slightly on completion of its traverse movement to allow the needle to move out of its trick to clear its old warp overlap.
3. The warp overlap wrap: The warp guide rises between the needles and automatically overlaps from the left, lowering itself again on the right side of its needle.
4. Warp knock-over and underlap: The needle now retires into its trick to knock over the old overlap, whilst the warp guide is cammed under its needle to the start position for its next overlap, thus completing the closed lap pillar.
NB: The closed lap is used for the carbine needle but the alternating overlap of the open lap pillar stitch used with the conventional latch and bearded needles gives a more balanced loop structure. Tricot lapping with two guide bars produces a secure fabric which does not unrove.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
