Jacquard Complete Installation Part 1

Описание: Here is a look to Electronic Jacquard Complete Installation Part 1

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Jacquard shedding system was developed by Joseph Marie Jacquard (1752–1834) who was a French weaver and merchant . In case of cam and dobby shedding systems, large number of yarns passing through a heald is controlled as a group. Thus it precludes the possibility of controlling individual ends independently. Therefore, complicated woven designs cannot be made using cam or dobby shedding systems. With jacquard shedding system, individual ends can be controlled independently and thus large woven figures can be produced in fabrics.

Mechanical jacquard systems can be classified under three categories:

Single lift and single cylinder (SLSC)
Double lift and single cylinder (DLSC)
Double lift and double cylinder (DLDC)

Jacquard Harness

It is the system by which the ends are controlled during jacquard shedding with the help of nylon cords, heddles (heald eyes) and dead weights (lingoes). In the preceding part of discussion, it has been considered that the capacity of jacquard is 300 ends. Now, if the fabric has 3000 ends then ten repeats of the design can be produced on the fabric. For example, if a floral pattern is woven on the fabric and it requires 300 ends, then 10 such floral patterns can be produced on the entire width of the fabric. It is assumed that the hooks of the jacquard are arranged in six rows and each row is having 50 hooks. Then each hook will effectively control 10 (3000/300) ends. The interlacement pattern of end 1, 301, 601, 901, 1201, 1501…….2701 will be identical and thus they can be controlled by hook no. 1 through 10 nylon cords. Similarly, hook no. 300 will control 10 ends namely end number 300, 600, 900, 1200, 1500, 1800, ….., 3000. This has been depicted in Figure 6.44. The individual harness cords pass through the perforations of a wooden or polymer board named comber board. The dead weights or lingoes pull the end downwards when it is not lifted.

In recent times electronic jacquards have become very popular. It controls the ends by synchronized operations of following machine components.

Electromagnet
Retaining hook or ratchet
Hooks
Knives
Double roller
The knives are used to lift or lower the hooks. If the electromagnet is activated by the signal pattern, then it can briefly retain the upper end of the retaining hook once the latter is pressed on the electromagnet due to the upward movement of the hook. If this happens then the hook is not retained by the retaining hook when the former starts to descend with the knife. On the other hand, if the electromagnet is not activated, then the hook is retained or caught by the retaining hook.


Harness Mounting
The jacquard harness is the system of cords, healds and lingoes that transmit the movement of the hooks to the individual warp threads. A simple form of harness is represented in the fig. below:

A simple form of harness is represented in the figure.

There are two main types of harness ties.
1. Norwich system.
2. London system.

Norwich system

When jacquard mechanism is mounted with the parallel of the loom is called Norwich Jacquard. In this jacquard the long rows of needles are parallel to the comber board & at the right angle to the warp. The cords will be at the front or at the back or at both front & back of the loom.

London system
When the jacquard mechanism is mounted at one end of the loom and at 90˚ angle of the loom is known as London Jacquard. In this system the jacquard is turned through a right angle the cords stay at the side of the loom.

The both tie systems are divided into the following four types.
1. Single tie-up.
2. Repeating tie-up.
3. Pointed tie-up.
4. Mixed tie-up.

Single tie-up: (For asymmetric design)
In this system only one harness cord is attached to one neck cord. There are must be as many hooks as there are threads in the width of the fabric. If the design is required to be woven 400 ends there are 400 hooks in the jacquard.
No. of neck cord = No. of harness cord = No. of warp in a repeat

Scope
This tie is used to produce a fabric containing only one repeat across the width of the fabric.

Repeating tie-up
This is the most common design tie used for both Norwich and London harness ties. In this tie there must be as many harness cards tied to each neck cord as there are 4 repeats in the full width of the fabric. If there are 4 repeats of the pattern then there will be 4 harness cords tied with each neck cord.
No. of neck cord = No. of jacquard



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