The high pressure area in the card-at the junction between cylinder and flats at taken-in end-causes ejection of dust over top of the back plate and between the flats.
Another high pressure area- at the junction between the main cylinder and doffer -leads to ejection of dusty air over the doffer
Doffer comb produces air turbulences, which causes dust to rise and at the calender roller the air that is mixed with the cotton in the web is squeezed out, together with dust and fly.
Air escaping into the atmosphere from the high pressure zone carries dust with it and is responsible for most of the dust in the card room.
Modern HP cards are equipped with the dust and fly collector such as shirley pressure point system for extracting the dust, fly and fibres which are collected in a special chamber without rendering unhygienic the atmosphere in the card room.
This has low running cost and useful
1) to prevent the ejection of dust by suitably covering the regions of the machine where the dust is liberated.
2. To move the dust from several forces to a central region from which it can be conveniently removed.
An Exhaust fan, through suitable hoods fitted to critical regions of the card draw off air with fly and dust and after separating these from air, pure air is returned to the department.
The dust passing through the slits between the flats is retained (and then exhausted) by a flexible metal sheet across the full width of flats and placed inside the flat chain to cover about 2/3 of the flats
The region where flats take position on the bend is also boxed in and exhausted.
A deflector shield is fitted over the doffer comb and extends forward to the calender roller and the region under the calender roll is boxed in to collect the fly that falls from the under side of web.
A screen of perforated metal is fixed in front of the flat cleaning brush to catch any fly released there, and a similar screen is fitted on the coiler where the sliver turns through a right angle to proceed to the can.
The complete shirley pressure point system reduces the dust load in the card room atmosphere by about 90%.
Following are the improved waste removal system of latest high production carding,
Internal suction system:
The integral fan for internal suction creates a vacuum with in the outer shell. Thus no dust from the card escapes into. the workroom. the suction is very effective in the removal or fly waste, dust and micro dust which are released during carding. Dust and wastes are removed at all points of occurence, feed, flat entry, flar strips, web delivery and waste chamber under the card. The internal suction operates continuously there by maintaining constant autodymanic conditions in the card.
The exhaust air is conveyed to air conditioning system. The amount of exhaust air is 2300 m3/h per card. Under card waste removal system.: . The under card waste are transferred by programmed periodic blasts of compressed air into the vicinity of a suction hood and collected in the rear most filter of the two filters built into the outer shell. The over card wastes including flat strips are collected in the foremost filter. The intermittently acting central suction system programmed to empty first the foremost filter and then the rear most filter.
The card can be connected to a continuously acting suction system in which case there is no need for fan and filters. manual cleaning of filter is necessary in the absence of central suction system.
