Auto leveler (autoleveller) in carding | How it works?

Careful control of sliver uniformity is necessary in the spinning process, to minimise the production of streaky fabrics. waste of raw material and  waste of production time.

So, continuous checking of sliver weight together with automatic correction of sliver weight variation at card is necessary.

The irregularity of card feed material is the important reason for sliver count variation ranging from very short(upto 25 cm) to very long term (more than 250 m ) variations.

Based on high spinning draft, even short term sliver irregularity leads to quite distinct count variation in yarn.

1. Graf 'Optima" card auto leveller:

Sliver passes between front draft controlling roller first, then passes between tongue and groove roller. Sliver variation cause the tongue (upper) roll to rise or fall. These very small movements of the tongue roll or the variations in mass per unit length of card sliver are amplified 20 fold and transmitted to an infinitely variable speed gear box. The out put shaft of the same drive the front draft controlling roller, calender roller, and coiler roller at variable speed so as to adjust the draft in accordance with the sliver thickness measurement.

2. RIETER C4 RR LEVELLER:

This system reduce long-term and short term variation., The weight of sliver leaving the card is sensed with a pair of stepped roll i. e., the number of fibres in the cross section is measured.

Deviations from the nominal count are processed by electronics into correction commands, which are executed at the card in take via the feed roll. 

3. INGOLSTADT ELECTRONIC LEVELLER

Of the two sensing roller, one is movable under spring pressure. The distance between centre of two rollers varies with the fluctuating sliver thickness. The amount of this lift is measured and converted into a voltage proportional to the sliver thickness.

Prom this measured value a set point speed is derived for the variable speed motor which drive the draft roll. If the actual speed differs from the set point, the variable speed motor is de-accelerated or accelerated untill the two speeds coinside i. e The output shaft of variable speed motor drive the draft roll at variable speed so as to adjust the draft in accordance with the sliver thickness measurement.

Stop motions in the carding

Stop motions are used in the following places of HP cards.

object:

1.To stop the doffer when sliver is missing or sliver is too thin or too thick or when the lap-up (choking) on coiler calender Roller.

If a sliver is missing or sliver is too thick/thin, the spacing between coiler calender roller changes. As the calender roll move, the aluminium disc is lifted and comes in contact with adjustable pins, it operate the corresponding electro pneumatic valve on or off the doffer driving mechanism.

2. Sliver break stop motion:

The sliver delivered from the calender roller passes beneath a guide located at the end of a lever. This lever drops when the sliver or the web breaks and, stop the card by the operation of the mechanism.

3. Coiler hood stop motion:

A limit switch is provided to prevent the starting of doffer when the coiler hood is opened.

4.Optical feeler in the coiler unit:

A photo cell monitors the sliver between the calender rollers and the coiler. The optical feeler is so arranged that the running sliver interrupts the beam of light and if the sliver breaks. light reaches the photo cell so the doffer drive is cut out and the fault signalling lamp lights up.

5. Peed Roller Stop Motion.

At both ends of the feed roller, microswitch is provided. During the entry of abonormal thickness of lap or metal pieces under the feed roll, the knob raises. When the knob raises by 1 mm the limit switch will act in such a way that the machine stop, and the white lamp burns, giving a signal to the operators.