Textiles: fiber preparation – Working – Carding
Patent
1994-07-22
1996-11-19
Calvert, John J.
Textiles: fiber preparation
Working
Carding
19101, 19105, D01G 1524, D01G 1536
Patent
active
055750389
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of carding a fibrous feedstock to form a carded sliver using a carding engine having a main toothed wire cylinder, a takerin, a doffer, and a series of flats movable along a closed loop having a working path arranged alongside the outer periphery of the cylinder between the takerin and the doffer in order to carry out a carding operation on the feedstock in co-operation with the teeth of the rotating cylinder and to remove trash particles, nep, dust and short fibres from the feedstock to form the carded sliver.
In commercial production of carded webs to form a sliver, it is usual to run the cylinder such that the circumferential speed of the cylinder periphery is about 60,000 inches per minute. Thus, for a 40 inch diameter cylinder, a typical speed of revolution would be about 500 rpm. These figures are given by way of general explanation only, and typical cylinder dimensions and operating speeds vary from one manufacturer to another.
By contrast, a typical linear speed of the revolving flats along the working path is of a very considerably lower order, with a typical speed being about 6 inches per minute i.e. the ratio of flats speed X to cylinder peripheral speed Y is about 1:10,000.
As is well known in the carding art, the fibrous feedstock fed to the cylinder by the takerin is conveyed into the carding zone where the combined action of the high speed cylinder wires or teeth and the much slower speed wires or teeth of the flats exert a carding action on the feedstock to form a carded web, while in addition the flats remove unwanted material from the feedstock in the form of trash particles, nep, dust and short fibres which constitute flat strip waste.
The waste will include small fragments of seeds, husks and also undesired short fibres, so that the resulting web is composed mainly of fibres of usable length. The required amount of short fibres to be removed will depend upon the required quality of sliver to be derived from the web, and the operating parameters will be set-up to suit particular sliver quality requirements.
As mentioned above, the speed of the flats is very small compared to the peripheral speed of the cylinder, and it has always been assumed that this order of flats speed was. necessary in order to carry out a carding operation which is both technically efficient in producing a carded web which can produce a sliver of required quality, and also economic in its usage of the raw material feedstock.
With regard to the matter of economic usage of the raw material, the quality of the sliver depends upon the proportion of short fibres initially present in the feedstock, which still remain in the carded web after carding treatment, and therefore it is desirable to operate the carding engine in such a way as to minimise the residual short fibre content in the web. However, it has always been conventional wisdom that any alteration to the operating parameters to achieve increased removal of short fibres will necessarily involve an unacceptable raw material cost penalty by reason of an inevitable increase in extraction of fibres of usable length (typically about 1 inch).
Therefore, typical running speeds of flats of about 6 inches per minute are considered to be an acceptable compromise between the conflicting requirements of (a) maximising the cleaning efficiency and removal of short fibres and other undesired waste from the feedstock to obtain a required quality of sliver and (b) minimising the loss of acceptable fibres from the feedstock to avoid commercial under utilisation of the raw material resource.
Such typical running speeds have been used for many years, and have been found to provide a satisfactory quality of sliver consistent with economic utilisation of the raw material, and further, and most importantly, have provided reliable operation over extended periods, during which the radial clearances between the flats and the cylinder periphery remain within acceptable limits. The maintenance of these clearances is very impor
REFERENCES:
patent: 3373461 (1968-03-01), Bessette et al.
patent: 4438548 (1984-03-01), Grunder
patent: 4580318 (1986-04-01), Varga
patent: 4922579 (1990-05-01), Varga
patent: 5287600 (1994-02-01), Wespi
Cripps Harry
Varga Andre
Calvert John J.
Carding Specialists (Canada) Limited
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