· Three kinds of top roller
weighting(loading) are presently in use
- spring loading
- pneumatic loading
- magnetic weighting
· With pneumatic loading system, the total
pressure applied to all top rolers is obtained by simple adjustment of the
pressure in the hose using pressure reducing valve. Moreover the rubbercots
will not get deformed if the machine is stopped for a longer duration,
because the pressure on top rollers can be released to the minimum level.
· · The fibre
strand in the main drafting field consists of only a few remaining fibres.
There is hardly any friction field and fibre guidance provided by the rollers
alone is inadequate. Special fibre guiding devices are therefore needed to
carry out a satisfactory drafting operation. Double apron drafting arrangements
with longer bottom aprons is the most widely used guding system in all the
modern ringframes.
· · In doube
apron drafting system two revolving aprons driven by the middle rollers form a
fibre guiding assembly. In order to be able to guide the fibres, the upper
apron must be pressed with controlled force against the lower apron. For this
purpose, a controlled spacing (exit opening), precisely adapted to the fibre
volume is needed between the two aprons at the delivery. This spacing is set by
"spacer" or "distance clips".
Long bottom aprons have the advantage in comparison wiht short ones, that they can be easily replaced in the event of damage and there is less danger of choking with fluff.
Long bottom aprons have the advantage in comparison wiht short ones, that they can be easily replaced in the event of damage and there is less danger of choking with fluff.