Motion of Heald Shafts

Motion of Heald Shafts, Shuttle and Sley

In a plain power loom the heald shafts, shuttle and sley are operated by mechanisms that are set in motion by a motor through a crankshaft and a bottom shaft. The heald shafts move up and down by the shedding mechanism. The motion is obtained from the bottom shaft or counter shaft that carries the tappets. So the warp sheet is divided into two layers and it forms a shed.

The shuttle is pushed into the warp shed by a picker that gets activated by a picking mechanism. Normally the shuttle is kept in a shuttle box. When the shuttle is pushed, it reaches the opposite box. The arrival of the shuttle in the opposite box is confirmed by shuttle checking devices. The picking mechanism is set in motion by the bottom shaft.

The crankshaft operates the sley through the crank and crank arms. The sley gets a to and -fro motion. As the sley reciprocates, the reed, which is fixed to the sley, also gets a to and fro motion. The reed thus beats up the weft into the fell of the cloth.

Warp and Cloth Control

The shuttle is pushed into the warp shed by a picker that gets activated by a picking after beating up the weft into the fell of the cloth; a take-up motion draws the cloth forward and winds it on to a cloth roller. At the same time the warp is delivered from the weaver’s beam by a let-off motion.

These two motions are operated simultaneously and at a constant rate. I.e. the rate of cloth take-up is so set as to be equal to the rate of warp let-off. The take-up motion is operated through a sley stud and gear mechanism. The let-off motion operates by the pulling action of the cloth.

The two temple pieces located at the selvedges of the cloth control width.

Weaving Mechanism

WEAVING:-

The process of producing a fabric by interlacing warp and weft threads is known as weaving. The machine used for weaving is known as weaving machine or loom. Weaving is a skill that has been practiced for thousands of years. The initial application of weaving dates back to the Egyptian civilization. Over the years, both the process as well as the machine has undergone phenomenal changes. As of today, there is a wide range of looms being used, right from the simplest handloom to the most sophisticated loom.

In this rang, the most widely prevalent loom, especially with reference to India, is the ubiquitous “plain power loom”. In this and in the chapters that follow, the various mechanisms associated with the plain power loom are discussed in elaborate detail.

Mechanisms in a Plain Power Loom

In order to interlace wrap and weft threads to produce a fabric, the following mechanisms are necessary on any type of loom. There are three mechanisms involve they are

1. Primary mechanisms

2. Secondary mechanisms

3. Auxiliary mechanisms

1.    Primary Mechanisms

These are primary or essential mechanisms. Without these mechanisms, it is practically impossible to produce a fabric. It is for this reason that these mechanisms are called ‘primary’ mechanisms. The primary mechanisms are three in number.

a. Shedding mechanism

b. Picking mechanism

c. Beat-up mechanism

a.    Shedding mechanism

The shedding mechanism separates the warp threads into two or more layers according to design or divisions to form a tunnel known as ‘shed’

b. Picking mechanism

The picking mechanism passes weft thread from one selvedge of the fabric to the other through the shed by means of a shuttle, a projectile, a rapier, a needle, an air-jet or a water-jet. The inserted weft thread is known as “pick”.

c. Beat-up mechanism

The beat-up mechanism beats or pushes the newly inserted length of weft thread (pick) into the already woven fabric at a point known as “fell of the cloth”. These three mechanisms namely shedding, picking and then beat-up are done in sequence.

2.     Secondary Mechanisms

These mechanisms are next in significance to the primary mechanisms. If weaving is to be continuous, these mechanisms are essential. So they are called the ‘secondary’ mechanisms. They are:

a)    Take-up motion

b)    Let-off motion.

a)    Take-up motion

The take-up motion withdraws the cloth from the weaving area at a constant rate so as to give the required pick-spacing (in picks/inch or picks/cm) and then winds it on to a cloth roller.

b)   Let-off motion

The let-off motion delivers the warp to the weaving area at the required rate and at constant tension by unwinding it from the weaver’s beam. The secondary motions are carried out simultaneously.

3.     Auxiliary Mechanisms

To get high productivity and good quality of fabric, additional mechanisms, called auxiliary mechanisms, are added to a plain power loom. The auxiliary mechanisms are useful but not absolutely essential. This is why they are called the ‘auxiliary’ mechanisms. These are listed below.

a. Warp protector mechanism

b. Weft stop motion

c. Temples

d. Brake

e. Warp stop motion (Predominantly found in automatic looms)

a. Warp protector mechanism

The warp protector mechanism will stop the loom if the shuttle gets trapped between the top and bottom layers of the shed. It thus prevents excessive damage to the warp threads, reed wires and shuttle.

b. Weft stop motion

The object of the weft stop motion is to stop the loom when a weft thread breaks or gets exhausted. This motion helps to avoid cracks in a fabric.

c. Temples

The function of the temples is to grip the cloth and hold it at the same width as the warp in the reed, before it is taken up.

d. Brake

The brake stops the loom immediately whenever required. The weaver uses it to stop the loom to repair broken ends and picks.

e. Warp stop motion

The object of the warp stop motion is to stop the loom immediately when a warp thread breaks during the weaving process.

Crochet Warp Knitting Machine.

Experiment Name: - Study on the Crochet warp knitting machine.

Introduction:

The warp knitting machine is a knitting m/c where the loops are formed in course wise direction and the fabric produced is in open width form. In Tricot warp knitting m/c compound needles are used. The warp yarns are feed to the needles through guide bars using shogging and swinging motion.

Objectives:

      To get clear concept about the driving mechanism of crotchet knitting machine.

      To know the functions of different parts of the machine.

      To know about the different motions of the machine.

      To know different parts of the machine.

      To improve our technical knowledge.

Specification of the machine:

Ø  Company: DAH HEER Industrial Co. LTD.

Ø  Brand: DAHU.

Ø  Origin: Taiwan.

Ø  Model No: L

Ø  Size: 15 G

Main parts:

1. Motor 
2. Main shaft 
3. Size lever 
4. Shogging motion lever 
5. Weft yarn guide bar 
6. Warp yarn guide bar 
7. Needle bar 
8. Needle 
9. Pressure roller 
10. Take up roller  
11. Ratchet wheel

Machine description:

The machine is driven by an electric motor. Motion is transferred to the machine parts by gear and toothed belt. Here weft yarn guide bar gives to and fro motion and shogging motion. Shogging motion lever give motion to the weft yarn guide bar. Shogging motion is driven from motor by main shaft. Needle bar and warp yarn guide bar also give to and fro and shogging motion by the same mechanism. Take up roller has ratchet wheel, by which take up roller gets motion from the motor by pushing pawl and some mechanism.

Fig: Crochet warp knitting machine.

Features of crochet machine:

1.    On crochet machines, the warp chains are separate from the weft inlay and it is the latter threads that join the chaining Wales to each other.

2.    A single horizontal needle bar whose simple reciprocating action can be used to operate individually- tricked latch, carbine or embroidery needles.

3.    The patent or carbine bearded needle is used for fine structures and has a sideways crimped beard placed in a permanently- pressed position.

4.    No sinker, instead a fixed hold back bar is fitted in front of the knock over verge to prevent the fabric moving out with the needles.

5.    Closed lap pillar stitches and inlay threads controlled and supplied as separate warp and weft respectively.

6.    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 under lap and shog is fixed and is controlled from an electric cam whilst it’s upwards and downwards swing is derived from a rocker shaft. The warp yarn is often placed low at the front of the machine.

7.    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.

8.    There are usually up to two warp guide bars and up to 16 weft inlay bars, which may be electronically controlled.

9.    The weft inlay bars may rather be electronically-driven or mechanically controlled in the traditional manner by chain links or levers. The choice is governed by the requirements either of long complex pattern repeats and quick pattern changes as in sampling, or for simple structures and long production runs.

10. The knitting widths of crochet machine may vary between 16 and 122 inches (400 and 3100 mm).

11. Gauge, often expressed in needles per centimeter, are between 2 and 10 (E5 to E24).

12. Machines run at speeds between 200 and 350 courses per minute.

13. Crochet machines can process a range of filament yarns from 20 dtex to 1000 dtex.

14. The warp yarn is often placed low at the front of the machine.

15. Special attachments are available for producing fancy effects such as cut or uncut fring edges, pile, braiding and snail shell designs.

16. 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.

Conclusion:

Crotchet knitting machine is one of the most important knitting machines to produce knitted fabric. The knitting action of the crochet warp knitting m/c is done by the needles, its sliding latches and the guide bars. By this experiment we learned about the knitting action of a crochet warp knitting machine. This experience will help us to build our future life.

Raschel Warp Knitting Machine

Experiment Name: - Study on Raschel Warp knitting machine.

Introduction:

The warp knitting machine is a knitting m/c where the loops are formed in course wise direction and the fabric produced is in open width form. In Tricot warp knitting m/c compound needles are used. The warp yarns are feed to the needles through guide bars using shogging and swinging motion.

Objectives:

      To identify with Raschel Warp knitting machine.

      To know the machine specification.

      To learn the feature of this machine.

      To know the different parts of this machine.

      To know the machine mechanism.

      To learn the knitting actions of this machine.

Main parts:

      Guide

      Needle bar

      Sinker

      Front of machine

      Trick  plate

      Fabric

Machine description:

Their chain links are usually numbered in even numbers, 0, 2, 4, 6 etc., generally with two links per course. Raschel sinkers perform only the function of holding down the loops whilst the needles rise. They are not joined together by a lead across their ends nearest to the needle bar so they can move away clear of the needles, towards the back of the machine, for the rest of the knitting cycle. The needle trick plate verge acts as a fabric support ledge and knock-over surface.
The fabric is drawn downwards from the needles, almost parallel to the needle bar, at an angle of 120–160 degrees, by a series of take-down rollers. This creates a high take-up tension, particularly suitable for open fabric structures such as laces and nets. 

Fig. A. Knitting elements of a latch needle raschel machine

Fig. B. Cross-section of a latch needle raschel machine.

The warp beams are arranged above the needle bar, centered over the rocker shaft, so that warp sheets pass down to the guide bars on either side of it. The beams are placed above the machine so that it is accessible at the front for fabric inspection and at the back for mechanical attention to the knitting elements. The guide bars are threaded, commencing with the middle bars and working outwards from either side of the rocker-shaft. They are numbered from the front of the machine.

With the raschel arrangement, there is accommodation for at least four 32-inch diameter beams or large numbers of small diameter pattern bars. The accessibility of the raschel machine, it’s simple knitting action, and its strong and efficient take-down tension make it particularly suitable for the production of coarse gauge open-work structures employing pillar stitch, inlay lapping variations and partly threaded guide bars. These are difficult to knit and hold down with the tricot arrangement of sinkers. Additional warp threads may be supplied at the selvedges to ensure that these needles knit fabric overlaps, otherwise a progressive press-off of loops may occur. 

Fig: A Raschel warp knitting machine

Features of raschel machine:

1.    Raschel machines originally had a gauge expressed in needles per 2 inches (5 cm), so that, for example a 36-gauge raschel would have eighteen needles per inch. Now, the standard E gauge (needles per inch) is generally used.

2.    There is a wide gauge range, from E1 to E32.

3.    Their chain links are usually numbered in even numbers, 0, 2, 4, 6….etc.

4.    Generally with two links per coarse.

5.    Raschel sinkers are performing only the function of holding down the loops whilst the needles rise.

6.    Sinkers are not joined together by a lead across their ends nearest to the needle bar so they can move away clear of the needles, towards the back of the machine, for the rest of the knitting cycle.

7.    The needle trick plate verge acts as a fabric support ledge and knock over surface.

8.    The fabric is drawn downwards from the needles, almost parallel to the needle bar, at an angle of 120-160 degrees, by a series of take down rollers. This creates s high take-up tension, particularly suitable for open fabric structure such as laces and nets.

9.    The warp beam is arranged above the needle bar, centered over the rocker shaft, so that warp sheet pass down to the guide bar on either side of it.

10. The beam is placed above the machines so that it is accessible at the front for fabric inspection and at the back for mechanical attention to the knitting elements.

11. The guide bars are threaded, commencing with the middle bars and working out wards from either side of the rocker shaft. They are numbered from the front of the machine.

12. With the raschel arrangement, there is accommodation for at least four 32-inch diameter beams or large numbers of small diameter pattern bars.

13. The accessibility of this machine, it’s simple knitting action, and its strong and efficient take-down tension make it particularly suitable for the production of coarse gauge open work structures employing pillar stitch , inlay lapping Variations and partly threaded guide bars, these are difficult to knit and hold down with the tricot arrangement of sinkers.

14. Additional warp threads may be supplied at the selvedges to ensure that these needles knit fabric overlaps, otherwise a progressive press off of loops may occur.

Conclusion:

From this experiment we know about the raschel warp knitting machine and its features. Raschel knitting machine is one of the most important knitting machines to produce knitted fabric. So we should learn about this mechanism very carefully, this experience will help us in our future practical life.

Tricot Warp Knitting Machine.

Experiment Name: - Study on the Tricot warp knitting machine. 

Introduction:

The warp knitting machine is a knitting m/c where the loops are formed in course wise direction and the fabric produced is in open width form. In Tricot warp knitting m/c compound needles are used. The warp yarns are feed to the needles through guide bars using shogging and swinging motion.

Objectives:

      To identify with tricot Warp knitting machine.

      To know the machine specification.

      To learn the feature of this machine.

      To know the different parts of this machine.

      To know the machine mechanism.

      To learn the knitting actions of this machine.

M/C specification:

Brand: LIBA

Origin: W. Germany

Manufacturing Company: MASCHINEN FABRIK, NAILA.

Manufacturing Year: 1991

Width: 84 inch/ 213 cm

Type: COP 2K

Gauge: 28

Features of tricot machine:

1)    Tricot machines have a gauge expressed in needle per inch.

2)    Chain link numbering 0, 1, 2, 3, 4 …………etc.

3)    Generally with three links per course.

4)    Their sinker are joined to each other at the front and back, never move clear of the needles as they combine the functions of holding down, knocking over, and supporting the fabric loops.

5)    The fabric is drawn-away towards the batching roller almost at right angles to the needle bar.

6)    The warp beams are accommodated in an inclined arc toward the back of the machine, with the top beam supplying the front guide bar and the bottom beam supplying the back guide bar.

7)    The warp sheets pass over the top of the guide rocker shaft to their tension rails situated at the front of the machine.

8)    The machines have a simple construction and a short yarn path from the beams.

9)    Mechanical attention to the knitting elements is carried out at the front of the machine as the warp beams prevent access to the back.

10) The entire warp sheets are drawn over the rocker shaft to the front of the machine it is easier to thread up the guide bars connecting with the back bar; otherwise the front warp will obscure this operation.

11) The guide bars are therefore numbered from the back towards the front of the machine because of this threading sequence.

12) The conventional tricot beam arrangement generally restricts the maximum number of beam and guide bars to four, but this is not of major importance as the majority of tricot machines employ only two guide bars.

13) The small angle of fabric take away and the type of knitting action produce a gentle and low tension on the structure being knitted.

14) This is ideal for high speed production.

15) It is a simple, fine gauge (28-44), close knitted, p[lain and patterned structures, particularity for lingerie and apparel, specially using two guide bar structures with both bar over lapping and under lapping.

16) In the past, the two guide bar tricot or lock knit machine proved most particular in E28 and E32 gauge, with knitting widths of 84 and 168 inches (213 and 426 cm) using 40 denier nylon.

17) It is possible to knit from 10 denier nylon up to 1/20’s cotton count. Machine gauges can range from E10 for coarse staple fiber yarn to E20-E24 for textured yarn fabrics and E36-E44 gauge for fine fabrics, in knitting widths up to 260 inches (660 cm).

18) The needles, like the sinkers and guides, may be cast in leads or they may be individually cranked to fit into the needle bar.

Fig: Tricot warp knitting machine.

Knitting Action:

1. The rest position: The needles have risen to 2/3 of their full height from knock-over and have their hooks towards the back of the m/c. The latch bar is in downward position and the guides are at the front of the m/c with the sinkers forward, holding the old overlaps in their throats so that they are maintained in the correct height on the needle stems.

2. Needle rise and guide bar swing: With the sinkers forward holding down the fabric, the hooks and tongues rise, with the hook rising faster, until the head of the latter is level with the guide holes and is open. The guides then swing through to the back of the m/c.

3. The overlap and return swing: The guide’s shog for the overlap and swing to the front of the m/c immediately. The hooks and the tongues start to descend with the tongues descending more slowly, thus closing the hook.

4. Hook closing: The hooks and the tongues start to descend with the tongues descending more slowly, thus closing the hook

5. Landing: The sinkers start to withdraw as the needles descend so that the old loop is landed onto the closed hook. Thus the landing is occurred.

6. Knock-over and under lap: The sinkers start to withdraw as the needles descend so that the old loop is landed onto the closed hook and then knocked over as it descends below the sinker belly. At this point the under lap occurs before the needles begin their upward rise and sinker move forward to hold down the fabric.

7. Go to rest position: The sinkers now move forward to hold down the fabric loops and push them away from the ascending needles, which are rising to the rest position.

Conclusion:

The knitting action of the Tricot warp knitting m/c is done by the needles, its sliding latches and the guide bars. The main work of feeding the thread around the needle is done by guides with their shogging and swinging motions. By this experiment we learned about the knitting action of a tricot warp knitting machine. This experience will help us in our future career.