Latch needle | Characteristics & Uses of Latch needle

Latch needle were used on raschel and crochet machines. The latch needle is composed of a curved hook, a latch, or tumbler, that swings on a rivet just below the hook, and the stem, or butt. It is sometimes called the self-acting needle because no presser is needed; the hook is closed by the pressure of a completed loop on the latch as it rises on the shaft. Needles differ greatly in thickness, in gauge, and in length. Pierre Jeandeau patented the first latch needle (also known as the tumbler needle) in 1806 but there is no evidence of its practical use.There is also no evidence that the pivoting of a broken pocket knife blade led to the development of the latch spoon.

Latch Needle Characteristics:

1. Most widely used in weft knitting.
2. More expensive needle than the bearded needle.
3. Self acting or loop controlled.
4. Work at any angle.
5. Needle Depth determines the loop length.
6. Variation of the height of reciprocating produces knit, tuck or miss stitch.

Uses of Latch Needle: Latch needle are widely used in –

1.  Double Cylinder Machine,
2.  Flat Bar Machine,
3.  Single Jersey Circular Knitting Machine,
4.  Double Jersey Circular Knitting Machine.

The elements which characterise this type of needle are the following:

• the stem: the stem is the main part of the needle and its thickness is proportional to the machine gauge; the stem is arranged between the rods and the pockets of the needle bed, which acts as a guide; the stem can be bent to allow the needle to keep the position set by the selection mechanism.
• the butt: the butt is the stem section in contact with the cams or the selection mechanism; cams and selection mechanism generate the upward and downward strokes of the needle: the height of the butt can vary according to the different operating possibilities. A latch needle can have one or more butts, arranged at different levels.
• the hook: the hook is the upper end segment of the stem. It picks up the yarn fed by the thread guide to form the stitch. Height, diameter, length, thickness, shape and position are the main parameters of a hook.
• the latch holder: the latch holder is the part of needle carrying the latch pin. The latch can be assembled in three different ways:
  1. it can be screwed (this manufacturing technology is rather complex);
  2. it can be “R” standard pressed (when it has a straight hole);
  3. it can be “A” angle pressed (when it has a slant hole).
• The latch: it is shrunk on the pin and it can freely rotate in both directions; its length determines the stroke the needle must cover to form the stitch. At the latch end there is a recess (the “spoon”), which allows the thickness resulting from the mating of the latch and the hook to be reduced. The yarn must fit under the open latch but the surface on which the loop must slide must not be too thick; for this reason, a special pocket, or “throat”, is machined on the needle stem.

- See more at: http://www.textileschool.com/articles/341/knitting-needles#sthash.EOJglenX.dpuf

The elements which characterise this type of needle are the following:

• the stem: the stem is the main part of the needle and its thickness is proportional to the machine gauge; the stem is arranged between the rods and the pockets of the needle bed, which acts as a guide; the stem can be bent to allow the needle to keep the position set by the selection mechanism.
• the butt: the butt is the stem section in contact with the cams or the selection mechanism; cams and selection mechanism generate the upward and downward strokes of the needle: the height of the butt can vary according to the different operating possibilities. A latch needle can have one or more butts, arranged at different levels.
• the hook: the hook is the upper end segment of the stem. It picks up the yarn fed by the thread guide to form the stitch. Height, diameter, length, thickness, shape and position are the main parameters of a hook.
• the latch holder: the latch holder is the part of needle carrying the latch pin. The latch can be assembled in three different ways:
  1. it can be screwed (this manufacturing technology is rather complex);
  2. it can be “R” standard pressed (when it has a straight hole);
  3. it can be “A” angle pressed (when it has a slant hole).
• The latch: it is shrunk on the pin and it can freely rotate in both directions; its length determines the stroke the needle must cover to form the stitch. At the latch end there is a recess (the “spoon”), which allows the thickness resulting from the mating of the latch and the hook to be reduced. The yarn must fit under the open latch but the surface on which the loop must slide must not be too thick; for this reason, a special pocket, or “throat”, is machined on the needle stem.

- See more at: http://www.textileschool.com/articles/341/knitting-needles#sthash.EOJglenX.dpuf

The elements which characterise this type of needle are the following:

The stem: The stem is the main part of the needle and its thickness is proportional to the machine gauge; the stem is arranged between the rods and the pockets of the needle bed, which acts as a guide; the stem can be bent to allow the needle to keep the position set by the selection mechanism. The butt: the butt is the stem section in contact with the cams or the selection mechanism; cams and selection mechanism generate the upward and downward strokes of the needle: the height of the butt can vary according to the different operating possibilities. A latch needle can have one or more butts, arranged at different levels. The hook: the hook is the upper end segment of the stem. It picks up the yarn fed by the thread guide to form the stitch. Height, diameter, length, thickness, shape and position are the main parameters of a hook. The latch holder: The latch holder is the part of needle carrying the latch pin. The latch can be assembled in three different ways:

• It can be screwed (this manufacturing technology is rather complex);
• It can be “R” standard pressed (when it has a straight hole);
• It can be “A” angle pressed (when it has a slant hole)

The latch: It is shrunk on the pin and it can freely rotate in both directions; its length determines the stroke the needle must cover to form the stitch. At the latch end there is a recess (the “spoon”), which allows the thickness resulting from the mating of the latch and the hook to be reduced. The yarn must fit under the open latch but the surface on which the loop must slide must not be too thick; for this reason, a special pocket, or “throat”, is machined on the needle stem.  

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Needle | History | Function | Construction of Sewing needle

History: Needles are made in straight or curved forms. Today the steel needle is commonly used. Needles used for hand sewing since about 18,000 BC and made from bone, wood and horn. In 1800 AD, Balthasar Krems of Germany was the first to use a needle with the eye near the point and the he had developed it. Iron needles were introduced during the 15th century for hand sewing. The large scale production of sewing machines started about 1840 Curved needle is only used in blind stitch machine

Fig: Industrial sewing needle

Functions

1. To form a passage in the material through which the needle thread can be wholly passed.
2. To form a loop which can be picked up by the loooper of hook mechanism.

Needle construction:  The main construction features of a needle are-

1. Butt: The truncated conical shape at the top of the needle which a facility it’s insertion into the needle bars or clamp.
2. Shank: Usually larger in diameter than the rest of the needle, the shank can be cylindrical in shape of flat on side depending on the method used to secure the needle in or on the needle bar.
3. Shoulder: The section joining of the shank to the blade
4. Blade: The longest section of the needle, this runs from the shoulder to the eye.
5. Grooves: On one side of the needle there is a long groove which protects the needle threads as it enters and is withdrawn from the fabric. There is a short groove on the opposite side which extends a short distance above and below the eye. Its purpose is to aid the passage if thread into the material and loop formation.
6. Eye: An ellipheal hole between the two grooves. The shape and finish of the inside top of the eye are important factors in the prevention of thread damage during sewing.
7. Point: This is shaped to provide the best penetration of the material being sewn.
8. Tip: The tip when combined with the point, determine the case and extent of penetration into the fabric.

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