Needles generally used in weft knitting are latch needles. It is the most widely used type of needle today. This needle, which can operate at high speeds and is less likely to cause problems, is more advantageous than the others. Needles can be in different shapes depending on the machine type and thickness. All lingual needles consist of beak (hook), tongue, neck, body and foot (heel). It is used in weft knitting machines with flexible needles, hooked needles at both ends, compound needles and compound needles.
Ever since mechanical knitting looms were invented, knitting needles have become the heart of the process. There are three types of needles that have emerged over the centuries.
The flexible tip needle is the oldest type of needle. Thanks to its simple structure and cheapness, it has managed to remain in use for four centuries. Although new machines using this type of needle are rarely produced today, many of them are still used in many businesses around the world. In order to open and close the hook during production, the flexible-tipped needle needs an auxiliary element, a press. This auxiliary element adversely affects the production rate and limits the use of this type of needle in modern knitting machines.
The most successful needle to date is the latch needle, invented 150 years ago by Townsend and Moulden. The tongue of the needle is fixed and rotates around a pin to open and close the hook. The invention of this needle was inspired by the breaking of a pocket knife, according to a legend.
The latest development is the sliding needle. Although this needle has revolutionized the warp knitting industry, it has not yet found a commercial place in the weft knitting industry. To open and close the hook of the needle, a closing member slides through a hole in the main part of the needle.
As mentioned above, the flexible-tipped needle was the first needle produced. The machine is the cheapest and easiest type as it is produced from a single piece of metal with approximately 60 needles per inch in the jaws and making sure there is enough space between the needles. When the needles move back and forth in their beds, the movement must be a collective movement because of individual pressure and needle movement problems. Sequential movement in weft knitting is therefore performed by other loop control elements that move the loops along the needle body. Flexible-tipped needles are not competitive in the production of flat fabric types, and their use is currently limited to the production of special structures.
There are 5 basic parts of a flexible needle:
1. The body is the part of the needle around which the loop takes shape.
2. The needle head is the body part where it takes the shape of a hook to pass the new loop through the old loop.
3. The tip is the continuation of the downward rotating fold of the hook used to separate this loop from the new loop as the old loop slides towards the needle tip.
4. The slot or recess is the part where the tip enters the body when pressed, and with this movement the new loop is closed.
5. The needle foot can take a curve in a separate position inside the machine.
Knitting action on flexible needle
1-The last loop formed is in the body of the needle in the starting position.
2. When the needle moves up, the loop in the stem slides down more. Meanwhile, new thread can be fed into the needle.
3. The sinker presses the newly fed thread closer to the needle body and brings it into a position that allows it to enter the hook with the downward movement of the needle.
4. An auxiliary element known as the press (press) traps the newly fed yarn in the hook, allowing the old loop to pass over the fed thread to form a loop.
5. The new loop is formed and returned to the starting position.
Pierre Jeandeau patented the first latch needle in 1806, but patents for practical use were obtained by Matthew Townsend in 1849, thus challenging the 260-year reign of the flexible needle. The production of this needle is a more expensive process than the flexible needle, but it has the advantage of movement and loop control, thus making needle selection possible by providing individual movement and control of the needles. For this reason, this needle is the most widely used in weft knitting and is sometimes described as an automatic needle. Recently produced latch needles enable the production of very high quality fabrics.
When the needle moves up, the old loop is released from the hook of the needle because the loop slides down through the hook and contacts the tongue, the tongue opens and slides the loop over the tongue onto the body. When the thread is fed with the downward movement of the needle, the hook closes automatically because the old loop on the stem slides upwards in contact with the stem and closes the tongue by pushing it upwards, so that the newly fed thread is trapped inside the hook. Latch needles therefore automatically knit as the needles move back and forth. Except for Raschel warp knitting machines, these needles can be moved independently in their own slots. They can be used at any desired angle, but they are generally used at angles that will prevent the tongue from breaking and facilitate the opening of the tongue.
Latch needles that move separately can form their own loop structures for each needle, unlike needles used in warp knitting machines and flexible-tipped needles that move as a unit and need a guide or needle head to form loops in their body.
With the change in height during the back and forth movement of the needles, hanger, skipping or loop is formed and the depth determines the loop length. Specially designed latch needles can easily transfer loops in rib arrangement with selective elevation. Harosha needles with two needle 22 legs slide through the old loop in order to knit from the opposite bed, thus forming loops in the opposite direction.
Basic parts of latch needle
The latch needle has 9 basic parts:
1-The hook pulls the new loop and keeps it.
2. The slot meets the sharp part of the tongue (not shown).
3. The jaws are riveted to the backing where the sharp part of the tongue is (not shown).
4. Rivets can be straight or screwed. The slice is distributed in the slots by compression to retain the sharp part.
5. The sharp part of the tongue determines the location of the tongue on the needle.
6. The spoon-shaped part of the tongue is an extension of the sharp part and provides a connection between the hook and the extension of the hook towards the body when the tongue is closed.
7.The body carries the loop in the sliding or rest position.
8. The needle foot allows the needle to move back and forth when the needle comes into contact with the cams. Two-pointed reverse needle types have a hook at each end. When knitting a hook, the inactive hook moves back and forth and is controlled as a needle foot by a cam element called the slider.
9. The tail is an extension at the bottom of the needle foot. It gives the needle additional support and protects the needle along its path.
Knitting movement on latch needle
1. The top of the needle hook is flush with the top of the loop start point, the loop formed by the previously fed thread is trapped inside the hook. Thus, the rise of the loops during the rise of the needle is prevented by the stabilizer needle heads moving back and forth between the needles.
2. As the needle foot passes through the inclined part of the replacement cam, the old loop pressed by the needle head slides inside the hook, meets the tongue, turns it and opens the tongue (opening the tongue).
3. When the needle reaches the lowest point of the cam, the old loop slides off the hook and lowers the tongue into its slot in the stem (replacement height).
4. The needle begins to descend and the tongue is below the starting point as it moves under the old loop. At the same time, new thread is fed into the descending needle hook through the hole in the feeder guide. In this position, there is no risk of the thread being fed under the tongue.
5. The old loop comes into contact with the lower part of the tongue, causing it to close over the hook (thread feed and tongue closure).
6. As the needle head descends further below the starting point, the old loop slips out of the needle and the new loop passes through it. When needle lowering is complete, the loop length, which is approximately twice the amount of needle head lowering, is determined. The distance is defined by the depth setting of the needle cam, which is an adjustable value (stitch length formation)
The sliding needle with a sliding tongue was first patented in 1856 by Jeacock of Leicester. After going through a very painful period in the early 1960s, it has dominated the warp knitting industry today. However, it has not gone beyond being a prototype in weft knitting, where variety and needle selection are at least as important as knitting speed.
The slide needle consists of two different parts that are controlled separately: the hook and the closing element (tongue, piston, etc.). These two units rise and fall as one piece, but move faster to open the hook at the top of the ascent and to close at the beginning of the descent.
Two types of sliding needles are used in warp knitting machines. Tubular needle, in which the tongue moves through the hook tube, was introduced in 1938 and was successfully used in the 1940s and 1950s in James Morton's high-speed FNF tricot warp knitting machine as a competitor to flexible-point needle-operated machines. The second type is the open stem pusher bolt type, in which the flat hook member of the closure cable slides along a groove in the surface of the flat hook member outside rather than inside a tube, and is commonly used today. The pusher type is easier and cheaper to manufacture, the two parts of this needle can be placed separately and their size is smaller allowing knits with tighter loops.
The cost of the sliding needle is higher than the other needles. During the knitting process, each piece should be controlled separately by a cam system. Yarn feeding can also be extremely critical. For example, in a latch needle, the thread fed on the latch will not enter the hook, whereas in the sliding needle, the latch will slip, so even if a feed is made on the tongue, it will fall into the hook under all circumstances.
The slide needle has a simple, short and smooth movement without inertia problems of the tongue or jaw and does not rely on a knitted loop to open and close. Its thin construction and short hook make it particularly suitable for flat and fine warp knits knitted at high speeds. Chain loops can be made continuously without raising loops by needles, and its durable structure can resist bending by elastic threads or thick parts in spun threads. In addition, cotton deposits can be removed from the hook during movement by the closing element.
Knitting action on the slide needle
1- In the starting position, the loop is locked between the needle and the slider and the needle starts to move.
2. When the needle is in the upper position and the slider is in the lower position, the thread is laid by the guide. The loop belonging to the previous row is on the needle body.
3. The slide rises as the needle goes down.
4. While the downward movement of the needle continues, the hook is completely closed and the newly laid yarn is kept on the hook.
5. When the needle is pulled down further, stabbing occurs and a new row of stitches is formed.