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RINGS And TRAVELLERS - 2

ring spinning


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  • SHAPE OF THE TRAVELLER:

  • The traveller must be shaped to match exactly with the ring in the contact zone, so that a single contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn,
    a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning of synthetic fibre yarns.

    WIRE PROFILE OF THE TRAVELLER: 

  • Wire profile influences both the behaviour of the traveller and certain yarn characteristics, they are
    • contact surface of the ring
    • smooth running
    • thermal transfer
    • yarn clearance opening
    • roughening effect
    • hairiness

    MATERIAL OF THE TRAVELLER

  • The traveller should
    • generate as little heat as possible
    • quickly distribute the generated heat from the area where it develops over the whole volume of the traveller
    • transfer this heat rapidly to the ring and the air
    • be elastic, so that the traveller will not break as it is pushed on to the ring
    • exhibit high wear resistance
    • be less hard than the ring, because the traveller must wear out in use in preference to the ring

     

  • In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. "Braecker" has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.

     

  • Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon
    • yarn count
    • yarn strength
    • spindle speed
    • material being spun

    If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveller weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.

     

  • When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.

 

  • For the rings two dimensions are of primariy importance. 1.internal diameter 2. flange width. -

     

  • Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.

     

  • Low crown profle has the following advantage. Low crown ring has a flattened surface top and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely used ring form now.

     

  • The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.

     

  • A good ring in operation should have the following features:
    • best quality raw material
    • good, but not too high, surface smoothness
    • an even surface
    • exact roundness
    • good, even surface hardness, higher than that of the traveller
    • should have been run in as per ring manufacturers requirement
    • long operating life
    • correct relationship between ring and bobbin tube diameters
    • perfectly horizontal position
    • it should be exactly centered relative to the spindle

     

  • In reality, the traveller moves on a lubricating film which builds up itself and which consists primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets.
    The platelets are continually being replaced during working. The traveller smoothes these out to form a continuous running surface.The position, form and structure of lubricating film depends on

     

    • yarn fineness
    • yarn structure
    • fibre raw material
    • traveller mass
    • traveller speed
    • heigh of traveller bow
    Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec.

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