It includes the following topics:
Necessity of stripping
Conventional plain brush roll stripping method
Development in stripping process.
Necessity for stripping:
During the carding process, fibres and impurities become embedded in the wires of the cylinder & doffer which may reduce their effectiveness of carding and increases the nep count in card sliver & finally affect the quality of the yarn. So stripping the dust, fibres & impurities from the card clothing is essential to regain their efficiency.
Conventional plain brush Roll stripping
Stripping Roller: This is a wooden roller mounted on steel shaft covered with flexible wire fillet. The roller is about 6 inch in dia and slightly longer than the width of the cylinder.
stop the card.
Remove the flat strips and open the front middle plate.
Disengage the doffer gear.
Put the stripping Roller on the stripping stand of
Cylinder so that it runs with the points down where it comes in contact with cylinder wire,
Connect the crossed band drive from loose pulley of cylinder to the stripping roller,
Slip the main belt half way onto the tight pulley to turn the cylinder slowly,
The fibres & dirt impurities embedded in wires of cylinder & doffer are stripped i. e. The stripping action is done by passing the points of stripping roll over the back of the wire i. e. point to back action and with higher surface speed for stripping roller.
After the stripping is completed, remove the stripping roller & move the main belt to the tight pulley. Then put the stripping roll on the doffer stand for stripping the doffer (same procedure )
Let the sliver run onto the floor for 2 to 3minutes ( As the cylinder & doffer collects fibres very rapidly, the first yards of sliver will be abnormally light.
Limitation: It has serious disadvantages or throwing a considerable amount of dust& fly from card clothing into the card room atmosphere, there by creating undesirable and unhealthy working condition & spoils the machinery and product.
Developments of stripping
Following are some of, the developments of stripping method.
1. Dustless stripper
2. Vacuum stripper
Dustless stripper: This stripper consists of a plain stripping roll partially enclosed in a sheet metal hood from which a large flexible tube leads to a special stripping truck A small suction fan fitted on the truck exhausts into a fabric bag.
It requires 110 volts, 60 cycles, single phase current for a 1/6 HP, 3500 RPM Motor which is connected to the suction fan. Dustless stripper is used exactly like plain stripper, except that the fan is connected to the suction fan.
Dustless srtripper is used exactly 1 ike plain stripper, except that the fan is kept running during the stripping of cylinder & doffer.
As a result, the dust which would normally he thrown into the air drawn away by the suction and collects in the dust bag.
2. Vacuum stripper:
The stripper mainly consists of traverse tube, cast iron carriage and stripping nozzles.
Traverse Tube: A traverse tube extending the full width of the card is attached just above the doffer hood. The under side of the tube has a wide-slot. A long screw rod having a 1/2 inch pitch is fitted inside the tube. Cast Iron Carriage: A short cast iron carriage is mounted to slide along the traverse tube. A pawl which projects through the slot in the tube engages with the traverse screw. The two stripping nozzles are attached to the cast-iron carriage by means of bracket.
Stripping nozzles:
The cylinder nozzle is a cylindrical tube about 18" long which tapers to small rectangular opening at the end. It reaches over the top of the doffer to a slot in the stripping door. The doffer nozzles tapers to a long - narrow mounted opening located just in front of the doffer cover. Both nozzles lead to one opening where the end of a flexible suction hose is connected.
Drive to the nozzles:
The traverse screw is operated by two gears carried in a small case on the end of the traverse tube. A hole is cut in the doffer gear guard so that one of these motion gears can be made to engage with the large doffer gear by turning the cam.
Operational procedure's:
In stripping the card with this stripper, it is not necessary to stop either the cylinder or the doffer. The stripping nozzles are pushed to the far side of the card manually. The flexible tube is connected to the vaccum outlet. The cam is turned to engage the motion gears. Then, with the suction drawing the cotton from the surfaces of the cylinder and doffer, the nozzles move slowly across the card. The gear ratio is such that the nozzles advance 1 ess than their own width for each turn of the cylinder and doffer and so they strip overlapping spiral paths which completely cover both surfaces. The stripping takes 1 to 2 minutes depending upon the speed of doffer. The cylinder and doffer are kept rotating during the whole operation resulting in some gain in the production than the other strippers.
