RING FRAME - 3
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
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.
- Specific shape of the cop is achieved by placing the layers of yarn in a conical arrangement. In the winding of a layer, the ring rail is moved slowly but with increasing speed in the upward direction and quickly but with decreasing speed downwards. This gives a ratio between the length of yarn in the main (up) and cross(down) windings about 2:1.
- The total length of a complete layer (main and cross
windings together) should not be greater
than 5m (preferably 4 m) to facilitate unwinding. The traverse stroke of the ring rail is ideal when it is about 15 to 18% greater than the ring diameter.
- End break suction system has a variety of functions.
- It removes fibres delivered by the drafting
arrangement after an end break and thus prevents
end breaks on neighbouring spindles.
- It enables better environmental control, since a
large part of the return air-flow of the
system is led past the drafting system, especially the region of the spinning triangle.
- In modern installations, approx. 40 to 50 % of
the return air-flow passes back into the duct system
airconditioning plant via the suction tubes of pneumafil suction system.
- A relatively high vacuum must be generated to
ensure suction of waste fibres
- for cotton - around 800 pascals
- for synthetic - around 1200 pascals
- A significant pressure difference arises between the fan and the last spindle. This pressure difference will be greater , the longer the machine and greater the volume of air to be transported. The air flow rate is normally between 5 and 10 cubic meter/ hour.
- Remember that the power needed to generate an air-flow of 10 cubic meter/ hour , is about 4.5 times the power needed for an air-flow of 6 cubic meter/ hour, because of the significantly higher vacuum level developed at the fan.
- It removes fibres delivered by the drafting arrangement after an end break and thus prevents mulitple
- From Roving bobbin to cop, the fibre strand passes
through drafting arrangement, thread guide, balloon
control rings and traveller. These parts are arranged at
various angles and distances relative to each other.
The distances and angles together are referred to as the spinning geometry,has a significant influence on the spinning opeartion and the resulting yarn. They are
- yarn tension
- number of end breaks
- yarn irregularity
- binding-in of the fibres
- yarn hairiness
- generation of fly etc.
- Spinning Triangle:
Twist in a yarn is generated at the traveller and travel against the direction of yarn movement to the front roller. Twist must run back as close as possible to the nip of the rollers, but it never penetrates completely to the nip because, after leaving the rollers, the fibres first have to be diverted inwards and wrapped around each other. There is always a triangular bundle of fibres without twist at the exit of the rollers, this is called as SPINNING TRIANGLE. Most of the end breaks originate at this point. The length of the spinning triangle depends upon the spinning geometry and upon the twist level in the yarn.
- The top roller is always shifted 3 to 6 mm forward compared to bottom roller. This is called top roller
overhang.This gives smoother running and smaller spinning triangle. The overhang must not be made too large, as the distance from the opening of the aprons to the roller nip line becomes too long resulting in poorer fibre control and increased yarn irregularity.
- Continuous variation of the operating conditions arises during winding of a cop.The result is that the tensile force exerted on yarn must be much higher during winding on the bare tube than during winding on the full cop, because of the difference in the angle of attack of the yarn on the traveller. When the ring rail is at the upper end of its stroke, in spinning onto the tube, the yarn tension is substantially higher than when the ring rail is at its lowermost position. This can be observed easily in the balloon on any ring spinning machine.
- The tube and ring diameters must have a minimum ratio, between approx. 1:2 and 1:2.2, in order to ensure that the yarn tension oscillations do not become too great.
- Yarn tension in the balloon is the tension which
finally penetrates almost to the spinning triangle and
which is responsible for the greater part of the thread
breaks. It is reduced to a very small degree by
the deviation of the yarn at the thread guide. An
equilibrium of forces must be obtained between the yarn
tension and balloon tension.
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