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(11) | EP 0 019 455 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Carding engine and method of carding textile fibres |
| (57) A carding engine in which the arc of the carding cylinder that lies between flats
(5), and the doffer (6) has part of the inner surface which constitutes a restricting
section extending across the full width of the carding cylinder (4). The section (12)
is set at spacing of less than 0.25mm from the periphery formed by the tips of the
sawtooth wire of the cylinder surface and changes the airflowsto reduce sucking back
offlat strips. Presence of the restricting section (12) unexpectedly allows increased
cylinder speeds resulting in higher production rates. |
[0002] In the conventional cotton carding engine with revolving flats, the flat assembly consists of a series of flat bars surrounding the top arc of the carding cylinder and connected at each end to a pair of endless chains. The flats are driven by way of the chains to move in a closed path which runs adjacent to the cylinder surface normally from the back towards the front of the cylinder and then above the cylinder to return to the back thereof. The flat bars each carry a strip of card clothing material, which is usually discrete fillet wire having points which face the points of carding elements on the carding cylinder. Cotton fibres carried on the surface of the cylinder are opposed by the wire points on the flat bars and after being arrested are combed back on to the cylinder from whence they were originally lifted away. In this way tufts and agglomerations of cotton fibre are dismembered. Very short fibres, neps and trash remain embedded between the wires of the flat bars and cannot be combed back on to the cylinder. This residue together with any intermingled long fibres is referred to as "flat strips" and is cleaned from the flat bars after these have been lifted away from the surface of the cylinder and are on their return part of the path. This cleaning action, usually by way of an oscillating comb, ensures that the flat bars are clean as they again move into a position adjacent to the back end of the-cylinder.
[0003] One of the main requirements of a carding engine is that it should eliminate as much as possible of the short fibres, neps and trash from the cotton. When processing cotton for spinning into finer yarns, the quality and strength of these yarns depends on freedom from this material.
[0004] The object of the invention is to improve the standard of cleaning and carding in a carding engine and is based on the observation that at the moment when any given flat bar commences moving away from the cylinder surface at the front of the card the uppermost and dirtiest layer of flat strip material tends to be sucked onto the surface of the cylinder and thus re-contaminates the cotton fibres carried by the cylinder. A similar effect is observed when stationary flat plates are used in place of movable flat bars. Thus, a substantial proportion of the short fibres, neps and trash that have been removed become transferred back to the cylinder surface and are then transferred to the doffer. These impurities ultimately reduce the quality of yarn spun from the web.
[0005] It has been known that a percentage-plate may be used in the gap between the flat bars and the cylinder surface in the region where the flat bars commence moving away from that surface in order to effect some control of the amount of flat strips. The percentage plate is a smooth plate having a tapered leading edge which is set in the space and by adjusting the setting of that tapered edge relative to the cylinder surface the amount of flat strips may be controlled to some degree. The usual use of a percentage plate has been to increase the amount of waste sucked back onto the cylinder surface. This is often done in the interests of economy to reduce the loss of fibres present in the flat strips where a lower quality of yarn was acceptable. Percentage plates have, however, been unable to prevent the return of a proportion of the flat strip material to the cylinder surface.
[0006] It is also known that the part of the carding cylinder between the region of the flat bars and the doffer may be covered. Many different types of cover have been proposed, and one common arrangement is to use a succession of three plates, a stripping plate adjacent to the flats, a stripping door following the stripping plate and a bottom front plate following the stripping door and terminating adjacent to the doffer. There have been many other proposals for covers in this region, and it has also been proposed that part of the internal surface of the cover be provided with card clothing. There has been no evidence that any of these previously used covers has had any significant effect in reducing the sucking back of the flat strip material onto the cylinder surface.
[0007] According to the present invention a carding engine comprises a takerin, a carding cylinder clothed with metallic sawtooth wire, flat bars or plates surrounding an arc of the cylinder, a doffer spaced from the flats, and a cover over the arc of the cylinder lying between the flats and the doffer, in which at least part of the inner surface of the cover comprises a restricting section extending across the full width of the carding cylinder and set at a spacing of less than 0.25 mm from the periphery formed by the tips of the sawtooth wire on the cylinder surface.
[0008] It has been found that, by providing this limited clearance between the restricting section of the cover and the periphery of a cylinder clothed with metallic sawtooth wire, the air flows surrounding the cylinder in the region where the cylinder surface moves from the flats region are changed in such a manner that the suction tending to transfer part of the flat strip material back onto the cylinder surface is reduced or even eliminated. This has a dramatic effect on the cleanliness of the web taken by the doffer from the cylinder.
[0009] Preferably there is an abrupt reduction in clearance from the region preceding the restricting section to the section itself. This enchances the effect on the air flows.
[0010] In one preferred form of the invention the restricting section is provided, on at least part of its surface which faces towards the cylinder, with non-loading carding elements which extend axially for the full width of the cylinder. The term "non-loading carding element" is recognised in the art as meaning a carding element which will momentarily arrest a fibre as it passes the element, but will not permanently retain the fibre. Various types of non-loading carding elements are known, for example conventional card clothing having very short wires with small metallic points; sawtooth wire wherein the teeth are short, have small points and are set at a'suitable angle; and so-called granular card clothing which is a roughened surface wherein the individual peaks on the surface act as carding elements in arresting fibres. The selection of non-loading carding elements ensures that there is very little, if any, build up of material on the restricting section so that little if any cleaning is required. When the restricting section is provided with non-loading carding elements then the required clearance of less than 0.25 mm is set between the tips of the carding elements on the section and the periphery formed by the tips of the sawtooth wire on the cylinder surface. It is preferred to use metallic sawtooth wire on the restricting section, and the number of wire end points per sq. cm. should be such that the barrier provided to the air currents is sufficient to give the overall effect to the air flows that will prevent or reduce the sucking back of the flat strips.
[0011] Although an improvement in cleanliness and carding of the web is observed with spacing of up to 0.25 mm between the restricting section and the periphery formed by the tips of the carding elements on the cylinder surface, it is preferred that this spacing be no more than 0.18 mm.
[0012] The restricting section may preferably be located approximately halfway along the arc of the cylinder which extends from the flats region to the location of the doffer. However, it is envisaged that the restricting section may in some cases be positioned closer to the flats, or even closer to the doffer. In a further alternative the whole or part of the inner surface of the cover forms the restricting section. The restricting section may be conveniently made up of a plurality of members, for example four, arranged to be adjacent circumferentially of the cylinder. The members may be flat bars provided on their inner surfaces with low height and non-loading metallic sawtooth wire confronting the cylinder surface. With each flat bar approximately 3.175 cm in width this gives an arc length of.12.7 cm of the cylinder surface that is covered by the restricting section. However, more or less than four flat bars or other members could be used so that the arc length may be either more or less than that figure.
[0013] Desirably there are spaces in the cover in the region of the restricting section so that air may be expelled from between the cylinder and the restricting section. This can lead to better quality than is obtained with the cover completely sealed.
[0014] The invention is applicable both to single cylinder carding engines and to duo-cards, that is carding engines wherein the web if subjected to a first carding action between a first or breaker cylinder and its associated flats, is taken from the breaker cylinder by a doffer and transferred by a centre section to a second or finisher cylinder also having an associated set of flats.- Either or both of the breaker and finisher cylinders may have the arc between their respective flats and doffers covered by a cover assembly that comprises a restricting section in accordance with the invention.
[0015] One totally unexpected advantage of the invention is that it can lead to a very significant increase in the production rate of a carding engine. Preferably, therefore, the feature of the restricting section is used in combination with-a carding engine having means for rotating the carding cylinder at a speed substantially higher than those conventionally used. Thus, for example, in the context of a single cylinder carding engine, the cylinder may be accelerated to a surface speed of not less than 1395 meters/minute, e.g. a 127 cm diameter cylinder may be accelerated to a speed of not less than 350 rpm, 102 cm diameter cylinders may be accelerated to a speed of not less than 550 rpm, preferably approximately 800 rpm and even to speeds as high as 1,000 rpm. By running at such increased speeds increases of production rates of 30% and more can be attained with a single cylinder carding engine. Attempts have been made to increase production rates by accelerating the cylinder without the restricting section being present, but these did not result in the production of a satisfactory web at the higher rates. There thus appears to be an unexpected synergistic effect between the presence of the restricting section and the increase in cylinder speed, which gives very remarkable results.
[0016] Even more surprising results are obtained if the cylinder having the restricting section is fed with a web of fibres that have already been opened. Preferably the opened web of fibres is a pre-carded web, and more preferably the web is taken from an immediately preceding carding cylinder which may or may not have an associated restricting section.
[0017] One particular embodiment of the invention is in the form of a duo-card comprising a takerin, a breaker carding cylinder clothed with metallic sawtooth wire, flat bars or plates surrounding an arc of the breaker cylinder, a doffer spaced from those flats, a web transfer section at the centre of the card, a finisher cylinder clothed with metallic sawtooth wire, flat bars or plates surrounding an arc of the finisher cylinder, a doffer spaced from those flats, and a cover over the arc of the finisher cylinder lying between those flats and doffer in which at least part of the inner surface of the cover comprises a restricting section extending across the full width of the finisher cylinder and set at a spacing of less than 0.25 mm from the envelope of the tips of the sawtooth wire on the finisher cylinder surface.
[0018] In the aforesaid context the invention effects the additional cleaning already referred to. Of perhaps even greater importance however,.is the fact that use of a restricting section in finishing a pre-carded web allows even greater increases in production rates than those previously envisaged, and increases of 50% to 60% using a duo-card have been recorded.
[0019] As already stated, it is preferred that the web fed to the cylinder (in a single-cylinder card) or to the finisher cylinder (in a duo-card) has been pre-carded and the pre-carding is desirably effected by a cylinder rotating at conventional speeds, the cylinder with which the restricting section cooperates being rotated at speeds of from 25% to 100%, preferably from 40% to 60%, greater than the speeds of the pre-carding cylinder. As a particular example, in a duo-card having a 102-cm diameter breaker cylinder rotating at 500 rpm (1602- meters/minute) and a 102 cm diameter finisher cylinder rotating at 800 rpm (2564 meters/minute - a speed increase of 60%) increases in production of from 50% to 60% can be attained.
[0020] Attempts have been made to increase production rates by accelerating the finisher cylinder of a duo-card without any restricting section fitted to that finisher cylinder, but these did not result in the production of a satisfactory web at the higher rate. There thus appears to be even more of an unexpected synergistic effect between the presence of the restricting section on the finisher cylinder on a duo-card, and the increase in speed of that finisher cylinder, which gives extremely remarkable results.
[0021] Good results may also be obtained where a pre-opened web is fed to a cylinder with a restricting section other than in a duo-card context. For example, fibres may receive an initial carding operation on a single-cylinder carding engine, the carded web then being formed into a roll rather than being condensed into a sliver. The roll may be stored and the pre-carded web then fed from the roll to a further single-cylinder carding engine rotating at the increased speed and fitted with the restricting section.
[0022] A particular embodiment of the invention will now be described in more detail, by way of example only with reference to the accompanying drawings in which:-
Figure 1 is a schematic side elevation of a single-cylinder carding engine embodying the invention;
Figure 2 is a schematic side elevation of a duo-card carding engine embodying the invention;
Figure 3 is an enlarged schematic view of part of Figure 1 or Figure 2;
Figure 4 is a more detailed view of part of the carding engine of Figure 1 or Figure 2; and
Figure 5 is a view similar to Figure 3 of an alternative arrangement.
[0023] Figure 1 shows in outline a single cylinder carding engine. This has a conventional feed arrangement 1 from which a lap of fibres is taken to a lap-feed 2 and then by a takerin 3 to the carding cylinder 4, which is clothed with metallic sawtooth wire. The upper arc of the carding cylinder is surrounded by a series of flat bars 5 secured to chains in the conventional manner and movable in a closed path adjacent to the cylinder surface and along a return section as indicated by the arrows. On the return section of the path there is provided an oscillating comb (not shown) for cleaning short fibres, neps and waste material in the form of flat strips from the flat bars. Below the flat bars 5 there is a doffer 6, also clothed with metallic sawtooth wire, which takes the carded web from the cylinder, the web being removed from the doffer by a stripper roll 7 and thence being passed through a pair of crush rolls 8 to a condenser and calender rolls 9. The arc of the cylinder between the flat bars 5 and the doffer 6 is covered by a cover assembly 10 usually mounted on the bends of the carding engine.
[0024] Figure 1 shows in outline a duo-card carding engine. This has a conventional feed arrangement (not shown) from which a lap of fibres is taken to a lap-feed 101 and then by a takerin 102 to a breaker carding cylinder 103 clothed with metallic sawtooth wire. The upper arc of the breaker carding cylinder is surrounded by a series of flat bars 104 secured to chains in the conventional manner and movable, in a closed path adjacent to the cylinder surface and along a return section as indicated by the arrows. On the return section of the path there is provided an oscillating comb (not shown) for cleaning short fibres, neps and waste material in the form of flat strips from the flat bars. Below the flat bars 104 there is a doffer 105 also clothed with metallic sawtooth wire which takes the carded web from the cylinder, the web being removed from the doffer by a stripper roll 106, and thence being passed through a pair of crush rolls 107 to a redirecting roller 108 and takerin 109 from whence the web passes to a finisher carding cylinder 4. The finisher carding cylinder is clothed with metallic sawtooth wire and surrounded by a series of flat bars 5 similar in arrangement and operation to the flat bars 105. Below the flat bars 5 there is a doffer 6 also clothed with metallic sawtooth wire which takes the carded web from the finisher cylinder, the web being removed from the doffer 6 by a stripper roll 7 and thence being passed through a pair of crush rolls 8 to a condenser and calender rolls 9. The arc of the finisher cylinder 4 between the flat bars 5 and the doffer 6 is covered by a cover assembly 10 mounted in conventional manner on the bends of the carding engine.
[0025] In both the Figure 1 and Figure 2 embodiments the cover assembly (Figure 3) comprises a top plate 11, an intermediate section 12 and a bottom plate 13. The top plate 11 has a smooth inner surface spaced from the finisher cylinder surface and is conventionally mounted on the bends of the carding engine in such a way that the clearance a between the leading edge of the top plate and the envelope of the tips of the carding elements on the cylinder 4 may be adjusted. The intermediate section 12 comprises a series of four flat bars 14 having non-loading metallic sawtooth wire carding elements on their inner surfaces, the elements being 0.71 mm high and there being 86.8 points per sq. cm. The mounting of these bars is shown in more detail in Figure 4. The bottom plate 13 is secured to the bends of the carding engine so that there is a substantially constant clearance b between the smooth surface of that plate and the envelope of the tips of the carding elements on the cylinder over the whole surface of the plate.
It has already been stated that the clearance a is adjustable, and conventionally this clearance is set at between 0.5 and 1.5 mm. The clearance c at the trailing edge of the top plate 11 is conventionally fixed at about 0.75 mm. In accordance with the invention, the clearance d between the tips of the non-loading carding elements on the flat bars 14 and the periphery formed by the tips of the sawtooth wire on the cylinder is set at no more than 0.25 mm and desirably at less than 0.18 mm. There is thus an abrupt change from the setting c beneath the top cover plate to the limited setting presented between the intermediate restricting section 12 and the cylinder. The setting b between the bottom plate and the cylinder is conventionally fixed at about 0.75 mm. It is found that the abrupt change in spacing from the relatively wide spacing at c to the restricting spacing d creates air flow conditions which substantially prevent the sucking back onto the cylinder surface of the upper layer of waste material from the flat strips carried by the flat bars 5.
[0026] It has already been.explained that quite apart from increased cleanliness in the web taken from the cylinder wires by the doffer due to this effect, the presence of the restricted clearance-d together with an increase in cylinder speed makes possible an unexpected increase in production rates. As particular examples, a single 102 cm diameter cylinder carding engine according to the invention may have its carding cylinder rotated at a speed of not less than 550 rpm, preferably about 800 rpm and possibly as high as 1,000 rpm. It is found that using this arrangement it is possible to work a thicker or heavier web to obtain good sliver quality at production rates of 54.4 kilos per hour and more, for a cotton blend that without use of the restricting section would give unacceptable quality at production rates of 40.8 kilos per hour. This represents a substantial increase, of over 30% in utilisable production rates. In a duo-card carding engine with 102 cm diameter cylinders, the breaker cylinder may be rotated at a speed of 500 rpm and the finisher cylinder at the same speed, but desirably at a speed of not less than 550 rpm, preferably about 800 rpm and possibly as high as 1,000 rpm. With the finisher cylinder running at 800 rpm good sliver quality is obtained at production rates of 72.6 kilos per hour and more, representing a 50% increase over the production rate of 49.9 kilos per hour, the highest rate at which acceptable quality is presently being obtained.'
[0027] Figure 4 shows one way in which the intermediate part of the cover may be mounted on the bends 15 of the carding engine, and is applicable both to the single cylinder embodiment of Figure 1 and to the duo-card of Figure 2. Four flat bars 14 extend the full width of the cylinder and are each secured at opposite ends to respective carriers 16 by way of bolts 17. Each flat is provided on its inner surface with a non-loading metallic fillet wire card clothing 18 confronting the wires on the cylinder surface (not shown). The required setting.of the flat bars relative to the carriers 16 may be controlled by shims located as indicated at 19. The carrier arrangement at each side of the carding engine is identical, and each carrier is pivotally mounted at 20 to an arm 21 which in turn is pivotally mounted at 22 to the bend 15. The arm 20 is provided with an eccentric adjusting mechanism 23 cooperating with the bend 15 so that the spacing of the pivot point 20 from the cylinder surface may be adjusted. Each carrier is secured in the required position by a locking device comprising a lever 24 also pivoted about the pivot 22 and terminating in an enlarged head 25. A pressure element 26 is slidable on the lever 24 and is biased towards the pivot point by spring elements 27 disposed between the head 25 and the element 26. The pressure element 26 bears on a cut-away section 28 of the carrier 16. The pressure element may be engaged with the carrier by moving the element 26 towards the head 25 against the action of the spring 27 and when in position allowing the spring to move the element to hold the carrier 16. The spacing of the carrier 16 and the flats from the cylinder at this end of the carrier is controlled by a bolt 29 engaging the end of the flat, the bolt being adjustable in a tapped bore 30 in the bend 15 and being fixed in the set position by a lock nut 31. Thus, -by adjustment of the bolt 29 and of the eccentric 23 the assembly of flat bars may be set at the required uniform spacing from the cylinder surface.
[0028] It will be understood that only one particular method of mounting flat bars forming the intermediate section has been described, and that alternative arrangements may be used. The invention has been described in an embodiment where four flat bars are provided, but it will be understood that more or less than this number may be provided if required. The flat bars are shown provided with non-loading metallic sawtooth wire card clothing, but other types of non-loading clothing may be used. In some cases the intermediate section may be constituted by a plurality of members other than flat bars, and such member or members may or may not have card clothing thereon...The flat bars are shown in Figure 4 as being spaced closely adjacent one to another with sealing elements 32 between adjacent bars and top plate 11 in order to prevent air leakage in their region.
[0029] In some cases, however it is advantageous for such sealing elements to be omitted, and possibly for the bars or other members to be set further apart one from another and for the first bar to be spaced from the top plate 11. Thus, spaces are deliberately left for the expulsion of air from between the cylinder and the members, it being surprisingly found that the quality of yarn spun from fibres processed on a card where air is expelled is somewhat higher than when the fibres are processed on a card where there is sealing between the members forming the restricting section. There may be a tendency for these spaces to become closed by waste from the card, and it can therefore be advantageous to apply suction in the region of the spaces to ensure that they are kept clear.
[0030] Figure.5 shows schematically an alternative arrangement wherein a restricting section 40 is secured to the inner surface of a top plate 41 forming part of a cover which also includes an intermediate plate 42 and a bottom plate 43. The restricting section may have a smooth inner surface or may be provided with non-loading carding elements, and the clearance e between this and the periphery formed by the tips of the sawtooth wire on the cylinder 4 is no more than 0.25 mm, and desirably less than 0.18mm. The barrier section extends the full width of the carding cylinder, but its arcuate extent over the carding cylinder may differ from that shown. Means may be provided for adjusting the top plate on the bends to set the required clearance e at an optimum figure.
1. A carding engine comprising a takerin, a carding cylinder clothed with metallic
sawtooth wire, flat bars or plates surrounding an arc of the cylinder, a doffer spaced
from the flats, and a cover over the arc of the cylinder lying between the flats and
the doffer, in which at least part of the inner surface of the cover comprises a restricting
section extending across the full width of the carding cylinder and set at a spacing
of less than 0.25 mm from the periphery formed by the tips of the sawtooth wire on
the cylinder surface.
2. A carding engine according to claim 1 in which there is an abrupt reduction in
clearance above the periphery of the tips of the sawtooth wire on the cylinder from
the region preceding the restricting section to the restricting section itself.
3. A carding engine according to claim 1 or claim 2 in which at least part of that
surface of the restricting section which faces towards the cylinder is provided with
non-loading carding elements extending axially for the full width of the cylinder,
the elements and their arrangement being such as to create an air flow barrier.
4. A carding engine according to any one of the preceding claims in which the spacing
between the inner surface of the restricting section and the periphery of the tips
of the sawtooth wire on the cylinder surface is no more than 0.18 mm.
5. A carding engine according to any one of the preceding claims in which the restricting
section is located approximately halfway along the arc of the cylinder which extends
from the flats region to the location of the doffer.
6. A carding engine according to any one of the preceding claims in which the restricting
section is made up of a plurality of members extending axially across the cylinder
surface, and arranged to be adjacent circumferentially of the cylinder.
7. A carding engine according to claim 6 in which each member is a flat bar provided
on its inner surface with low height non-loading metallic sawtooth wire card clothing
confronting the cylinder surface.
8. A carding engine according to any one of the preceding claims in which there are
spaces in the cover in the region of the restricting section so that air may be expelled
from between the cylinder and the restricting section.
9. A carding engine according to any one of the preceding claims in which the engine
is a single cylinder carding engine and means are provided for rotating the cylinder
at a surface speed of not less than 1395 meters/minute.
10. A carding engine according to any one of the preceding claims in which the engine
is a duo-card comprising a takerin, a breaker carding cylinder clothed with metallic
sawtooth wire, flat bars or plates surrounding an arc of the breaker cylinder, a doffer
spaced from those flats, a web transfer section at the centre of the card, a finisher
cylinder clothed with metallic sawtooth wire, flat bars or plates surrounding an arc
of the finisher cylinder, and a doffer spaced from those flats, and in which the cover
and restricting section cooperate with that arc of the finisher cylinder which lies
between the associated flats and doffer.
11. A carding engine according to claim 10 and including means for rotating the finisher
cylinder at speeds of from 25% to 100% higher than those of the breaker cylinder.
12. A carding engine according to claim 10 and including means for rotating the finisher
cylinder at speeds of from 40% to 60% higher than those of the breaker cylinder.
13. A carding engine according to claim 10 and including means for rotating the breaker
cylinder at a surface speed of approximately 1602 meters/minute and the finisher cylinder
at a surface speed of approximately 2564 meters/minute.
14. A method of carding textile fibres comprising feeding the fibres by way of a takerin
to a carding cylinder clothed with metallic sawtooth wire cooperating with flat bars
or plates surrounding an arc of the cylinder, and stripping the carded web from the
cylinder, in which, while moving over the arc of the cylinder lying between the flats
and the doffer, the web is passed beneath a cover having an inner surface comprising
a restricting section extending across the full width of the carding cylinder and
set at a spacing of less than 0.25 mm from the periphery formed by the tips of the
sawtooth wire on the cylinder surface.
15. A method according to claim 14 in which the cylinder is run at a surface speed
of at least 1680 meters/minute.
16. A method according to claim 14 or claim 15 in which the fibres are fed.to.the
takerin in the form of a pre-opened web.
17. A method according to claim.14 in which the pre-opened web is formed on the breaker
cylinder of a duo-card and transferred to the takerin by a centre section of the duo-card,
the cylinder being the finisher cylinder of the duo-card.
18. A method according to claim 17 in which the finisher cylinder is rotated at speeds
of from 25% to 100% higher than those of the breaker cylinders.
19. A method according to claim 17 in which the finisher cylinder is rotated at speeds
of from 40% to 60% higher than those of the breaker cylinders.