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Traveller machine

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  1. 1. The traveller imparts twist to the yarn, and enables winding of the yarn on to the cop.
  2. 2. TRAVELLER LAG • The length wound on to the cop per unit time corresponds to the difference between speed of spindle and traveller. And this should be equal to that of front roller delivery speed. • The speed difference due to lagging of the traveller relative to the spindle, since the traveller does not have a drive of its own but is dragged along behind the spindle is known as ‘Traveller Lag’.
  3. 3. • High contact pressure (up to 35 N/mm2) is generated between the ring and traveller during winding, mainly due to centrifugal force. • The pressure induces strong frictional forces which in turn lead to generation of significant amount of heat. • This is the kernel of the ring/traveller problem. The low mass of the traveller does not permit dissipation of heat in the short time available. As a result the traveller speed is limited.
  4. 4. • Travellers are required to wind up yarns of very different types: coarse/fine ; smooth/hairy ; compact ; voluminous ; strong/weak ; natural fibre /synthetic fibre. • These widely varying yarn types cannot all be spun using just one traveller – variety of travellers are needed. Difference are found in: form, mass , raw material , finishing treatment of the material , wire profile , size of the yarn clearance opening for the thread. Spinners must make wise decision according to conditions.
  5. 5. FORM OF TRAVELLER • The traveller must be shaped to correspond exactly with the rings in the contact zone, so that a single contact surface, with the greatest possible surface area, is created between these two elements. 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. These are used in short staple spinning mills.
  6. 6. Wire profile also influences both the behaviour of the traveller and certain yarn characteristics, namely; • Contact surface of the ring • Smooth running • Thermal transfer • Yarn clearance opening • Roughening effect • Hairiness
  7. 7. • The material of the traveller should: • Generate as little heat as possible • Quickly distribute the generated heat from the area where it develops (the contact surface) 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; but • Be somewhat less hard than the ring, because the traveller must wear away in use in preference to the ring.
  8. 8. • In view of these requirements, travellers used in the short staple spinning mill are almost exclusively made of steel. However, pure steel does not optimally fulfill the first three requirements. Accordingly, traveller manufacturers have made efforts over several decades to improve running properties by surface treatment. Suitable processes for this purpose are: • Electroplating, in which the traveller receives a coating of one or most metallic layers, e.g. nickel and silver; or • Chemical treatment of the surface to reduce friction and pitting.
  9. 9. TRAVELLER MASS • Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. • If traveller mass is too small, the balloon will be too big and the cop too soft; material take-up in the cop will be low. An unduly high traveller mass leads to high yarn tension and many end breaks. Accordingly, the mass of the traveller must be matched exactly to both the yarn (fineness, strength) and the spindle speed. • 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 the traveller and better transfer of heat out of the traveller.