EP0524221B1

EP0524221B1 - Making rounded clusters of fibers

Info

Publication number: EP0524221B1
Application number: EP91907407A
Authority: EP
Inventors: Adrian Charles Snyder; George Larry Vaughn
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1990-04-12
Filing date: 1991-04-09
Publication date: 1994-12-14
Anticipated expiration: 2011-04-09
Also published as: CN1058818A; ES2067226T3; DE69105966T2; PT97344A; CA2079225A1; CN1027386C; DE69105966T3; ES2067226T5; IE911213A1; WO1991016484A1; EP0524221A1; JPH05505958A; AU7680291A; DE69105966D1; EP0524221B2

Abstract

Ball-shaped and other rounded fiber clusters that have a density that may be controlled, as desired, with good uniformity of size and density, may be obtained from staple fiber that has been crimped mechanically, as well as from spirally-crimped polyester staple fiber, by an improved process and apparatus at a high through put.

Description

FIELD OF INVENTION

This invention relates to improvements in making rounded clusters from staple fiber, and more particularly to a process and apparatus for making such clusters, and the resulting rounded (e.g. ball-like) clusters, especially from resilient crimped fiber of denier 4 to 15 (about 4 to 17 dtex) such as is useful for filling purposes.

BACKGROUND

Staple fiber has long been used as filling material, for support and/or insulating purposes. Polyester fiberfill has been a particularly desirable fiber for such purposes, because of its bulk, resilience, resistance to attack by mildew and other desirable features. Conventionally, fiberfill used to be processed in the form of batts, after the fibers were parallelized on a card (or garnett), because this was an economically attractive and useful way of handling fiberfill.
Recently, however, Marcus has disclosed in U.S. Patent Nos. 4,618,531 and 4,783,364 how spirally-crimped fiberfill can be formed into fiberballs that make a particularly desirable filling material, being lofty, soft and refluffable in a way that is similar to down filling. Marcus has also disclosed in U.S. Patent No. 4,794,038 how fiberballs can be made similarly from blends of fiberfill with binder fiber, which can then be activated to make useful bonded support structures, e.g. for cushioning and mattresses. Marcus has disclosed a useful batch process and apparatus that takes advantage of the spirally-crimped nature of his feed material for making such fiberballs, which are being produced commercially and have proved useful and interesting ball-like fiber structures, because of their lofty nature, because they are easily transported by air-conveying during processing, and because of the interesting and advantageous properties of the products, which may be processed into several interesting variants. We generally refer to these structures herein as fiber clusters.
An object of the present invention is to provide a process and apparatus that can be operated to provide such ball-like clusters of fibers continuously at high throughputs. Another object is to provide a process and apparatus that does not necessarily require a special feed fiber, but can be operated satisfactorily also with regular polyester staple fiber, or indeed other fibrous materials, to form fiber clusters of such densities and uniformity as may be required. A further object is to provide a process and apparatus that may be used to form clusters from fibers of coarser denier, even above 10.
As will be noted hereinafter, we have made several modifications to a type of carding machine in order to achieve our results.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a process for preparing rounded clusters of fibers, comprising feeding a uniform layer of staple fiber onto the peripheral surface of a rotating main cylinder covered with card clothing, whereby the fiber is advanced around the peripheral surface by said clothing and is brought into contact with a plurality of frictional surfaces, whereby said fiber is formed into clusters that are rolled into rounded configurations on the peripheral surface, characterized in that there is provided at least one arcuate doffing screen, radially-spaced from said clothing, said doffing screen being provided with openings of sufficient size for the clusters to pass through said openings, and to be doffed by emerging through said openings.
Use of a screen to doff clusters is a significant difference from existing carding machines, which have generally used a roll to doff carded fiber.
We have doffed clusters very effectively using an arcuate ribbed screen that is provided with transverse ribs with bases that are spaced radially from the clothing on the main cylinder, and with openings that are the transverse spaces between these ribs. It will be understood herein that "transverse" means transverse to the machine direction, i.e. the direction of rotation of the main cylinder, so the "transverse" ribs of such doffing screen are parallel to the axis of the main cylinder.
According to another aspect of our invention, therefore, there is provided a cluster-forming machine that is an improvement in a staple fiber carding machine comprising a rotatable main cylinder having its peripheral surface covered with card clothing and adapted to rotate in close proximity with a plurality of cooperating frictional surfaces, means to feed staple fiber in a uniform layer onto said main cylinder, and doffing means, the improvement characterized in that said frictional surfaces cooperate with the card clothing on the peripheral surface of the main cylinder in such a way that fiber clusters are formed by the cooperation between the card clothing and said frictional surfaces, and the doffing means comprises a doffing screen provided with openings of sufficient size for the fiber clusters to emerge. Examples of "cooperating frictional surfaces" are described herein, and include stationary elements with frictional surfaces, such as plates and segments that may be smooth or covered with card clothing, and screens, and also movable elements, including worker and stripper rolls, such as are used on roller-top cards, and belt-driven flat elements, such as are used on revolving flat cards.
An important advantage according to the invention is that doffing and transportation of the emerging clusters may be assisted by suction and/or blowing. For instance, the rounded clusters may be blown directly into tickings and formed into pillows or other filled articles. Alternatively, the clusters may be packed and later processed as desired.
According to another aspect of our invention, there is provided an improved process for preparing rounded clusters of fibers, comprising feeding a uniform layer of staple fiber onto the peripheral surface of a rotating main cylinder covered with card clothing, providing a plurality of essentially arcuate frictional surfaces that are spaced radially from said clothing, wherein the radial spacing and frictional characteristics of said frictional surfaces and of said clothing and the rate of feed of said staple fiber are controlled so that said clothing becomes loaded with a compressible layer of fibers, whereby lofty rounded clusters of fibers are formed in the peripheral space between said clothing and said frictional surfaces, and doffing said clusters. As will be described herein, the fact that the card clothing is loaded with fiber is another significant difference from operating a conventional carding machine of this type. It is very surprising that rounded clusters are formed in the peripheral space when these (arcuate) frictional surfaces are so spaced and the process is so operated, as described herein.
The staple fiber that is fed to the main cylinder may be in various forms, e.g. a cross-lapped batt, or may be bale stock that has previously been baled, but is fed to the main cylinder after having been opened.
Preferably, especially for making pillows, filled articles of apparel, or like articles where such aesthetics are important, the staple fiber fed to the main cylinder may have been slickened.
For lower density and better insulation, staple fiber of hollow cross-section is preferred.
If desired, for making bonded support articles, the staple fiber fed to the main cylinder may be a blend of polyester fiberfill or other high melting fiber blended with lower melting binder fiber.
The denier of the feed fiber may be as high as 15 dpf (about 17 dtex), and will generally be at least 4 dpf (about 4 dtex) for use as filling material, especially for support purposes, but will be selected according to the desired end use. For instance, useful blends for apparel insulation have been made from fiber of denier as low as 1-2 dpf (about 1-2 dtex).
By use of our invention, as described hereinafter, we have found it possible to process staple fiber that has been mechanically crimped, and to produce desirable lofty fiberballs of uniform average density.
According to another aspect of our invention, therefore, there is provided a mass of lofty rounded staple fiber clusters of average dimension about 1 to about 15 mm, and of average density less than about 1 pound per cubic foot (about 16 Kg/cu m), consisting essentially of randomly-entwined, mechanically-crimped synthetic staple fiber of cut length about 10 to about 60 mm, provided the staple fibers are not fibers having both spiral and mechanical crimp in the same fiber. These lofty clusters are randomly- arranged and entwined as in Marcus fiber clusters prepared from spirally-crimped feed fiber; they are quite distinct from the hard neps or nubs that have been used in novelty yarns, and that are small knotted or tangled clumps of synthetic fibers or indeed of natural fibers, such as cotton. As indicated, preferred forms of our mechanically-crimped synthetic fiber may be slickened polyester staple fiber, and/or a blend with a lower melting binder fiber, that may, if desired, be a sheath/core bicomponent with a sheath of lower melting binder material, and a core of polyester or like high melting fiber-forming material.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic side-view in elevation of a preferred apparatus according to the present invention.
Figure 2 is a sketched representation of how a section cut through card clothing loaded with fiber that has been removed from a main cylinder, might show the topography of the surface, as will be described hereafter.
Figure 3 is a sketched representation of how carding teeth grip the fibers.
Figure 4 is a schematic view in perspective of a portion of a preferred ribbed screen according to the present invention.
Figure 5 is a sketched representation of an end-view of a portion of the main cylinder and doffing screen with the clusters emerging.

DETAILED DESCRIPTION OF THE INVENTION

A preferred apparatus according to the invention will be described with reference to the accompanying drawings. As indicated, in some respects, some of the features of this apparatus resemble a card (or carding machine) from which, for convenience, such elements and features have been adapted.
So, reference is made to the art on carding, including a Manual of Textile Technology, in the Short- staple Spinning Series, Volume 2, entitled "A Practical Guide to Opening and Carding", by W. Klein, The Textile Institute, 1987, and to a summary of available types, in an article by B. Wolf, in International Textile Bulletin 2/85, pages 9, 12, 16, 19 and 20, referred to on page 35 of Klein's Manual, both the Manual and the article being hereby incorporated herein, by reference.
The tasks of a card are listed in the former as:-

Opening to individual fibers-
Elimination of impurities-
Elimination of dust-
Disentangling of neps-
Elimination of short fibers-
Fiber blending-
Fiber orientation- and
Sliver formation.

Such are indeed the tasks of most cards. In other words, such tasks (of most cards) do not include forming ball-like fiber clusters. However, cards have been used by some to entangle fibers into bodies variously referred to by terms such as neps, nubs, and other terminology. This technology has been regarded as proprietary, so the literature on processes that may have been used for this purpose is sparse. Steinruck, however, disclosed an apparatus for making nubs in U.S. Patent No. 2,923,980. Steinruck indicated that, previously, as many as 10 machines in a row had been used to reduce the fiber stock to the desired small hard nubs. Steinruck said his machine could be operated to form nubs of the size and hardness desired by perhaps as few as 2 machines in sequence. Even this need for a sequence of 2 machines is, however undesirable, and so we have provided a machine that can make our desired clusters on a single machine. Steinruck wanted hard neps or nubs. In contrast, we want to make resilient lofty ball-like structures of controlled and uniform density. Another difference from prior art nep (or nub) formation is that these have generally been made from fibers of low dpf (denier or dtex per filament of less than 3) such as cotton and other low denier fibers that knot easily and can form hard neps that are useful in novelty yarns. When a filling is used for support purposes, such low dpf fiber is generally not as desirable as higher deniers of 4 (about 4 dtex) and above (even up to 15 denier, about 17 dtex) that are generally preferred, because of their resilience. This property, however, increases the difficulty of making clusters that will not later unravel. It should be understood that our process and machine may also be operated with low denier feed fiber that is easier to form into clusters. In other words, although higher denier synthetic fibers are generally preferred as filling material, lower denier synthetic and natural fibers may also be formed into fiber clusters by our process and machine.
As emphasized by Steinruck, his objective of forming nubs is almost the reverse of the primary function of operating an ordinary card (to lay individual fibers as much as possible in parallel lines and to remove any neps or nubs). Indeed, a book was published by Wira, entitled "Nep Formation in Carding", by P.P. Townend, to advise how to avoid the major problem of nep formation in the carding of staple fibers. Steinruck wanted to convert his fibrous mass into nubs which Steinruck would later incorporate into webs or slivers on a card in a subsequent operation. Steinruck used a (modified) roller-top card, and it is believed that other existing processes for making neps, nubs, etc., have generally used roller-top cards. In contrast, for a preferred machine according to the present invention, we have modified a card with carding plates (somewhat as shown in Figure 101 on page 45 of the Manual by Klein, or in Figure 22 on page 20 of the article by Wolf, both referred to hereinabove). Our objective is also the reverse of the primary function of operating an ordinary card.
Our preferred machine is illustrated in Figure 1 (which does not show the card clothing) and consists essentially of a main cylinder 10, of diameter 50 inches (about 1.3 m), that is covered with card clothing, and that is shown driven in a clockwise direction at a rate that largely determines throughput, being generally some hundreds of revolutions per minute (rpm), preceded by a roll 11 that is referred to as a licker-in (Klein refers to this as a "taker-in"), of diameter 9 inches (about 23 cm), that is also covered with clothing (but of much lower point density), and that is shown driven in a counter-clockwise direction, i.e., opposite to that of main cylinder 10, with an underlying basket 11 A, and itself preceded by a feed roll 12, that is shown driven also in a counter-clockwise direction (like licker-in 11), and that cooperates with a feed plate 13 in feeding opened fiber from a source of supply (not shown) at a uniform rate evenly across the width of licker-in 11. The periphery of main cylinder 10 is surrounded by a series of stationary cooperating frictional surface elements, indicated generally by 14, and more specifically (serially from licker-in 11) as 15, 16, 17, 18 and 19, all of which have arcuate frictional surfaces that are spaced-radially from the (teeth of the card clothing on) main cylinder 10 to allow processing (into clusters) fiber fed from licker-in 11 within the peripheral space around main cylinder 10, and defined on the outside periphery of such space by the arcuate frictional surfaces of these stationary elements 14. The radial spacing may be adjusted, and this can be an important means for controlling the process and the products produced.
As indicated, opened fiber is uniformly fed between feed plate 13 and feed roll 12, which latter is provided with teeth (or other means) to advance the fiber towards licker-in 11, more or less as shown in Figure 84, on page 39 of Klein's Manual. The clothing on licker-in 11 forwards the new fiber (fed from feed roll 12 and feed plate 13) past underlying basket 11A to the clothing on main cylinder 10. Both sets of clothing are travelling in the same direction, but that on main cylinder 10 is moving at a much higher speed. Thus, the new fiber is picked up by the teeth on main cylinder 10 and enters the space between the arcuate frictional surfaces of stationary elements 14 and main cylinder 10 (covered with card clothing). During start-up, new fiber (fed from licker-in 11) will load onto the card clothing on main cylinder 10, and so some minutes are likely to pass before any product is delivered in the form of ball-like clusters. Also, as will be evident, a certain amount of empiricism may be needed to adjust the feed rate of any particular feed fiber to the surface speed of the main cylinder, clothed with appropriate card clothing, and surrounded by appropriately spaced stationary elements 14, in order to obtain a satisfactory delivery of the desired clusters, and steady state operation. Once the processor reaches steady state operation, i.e. once the amount of fiber (in the form of rounded ball-like clusters) delivered by main cylinder 10 is the same as the amount fed to the processor, the card clothing on the main cylinder will have become loaded with fiber that has worked its way down the teeth, so the new fiber can only be collected at (or near) the outer extremities of the teeth of the card clothing. However, surprisingly, this fiber is not loaded uniformly in density or spatially (when the processor is run with a correct feed rate of fiber and main cylinder speed); in other words, there are relatively high locations loaded with more fiber and contrastingly lower locations loaded with less fiber across the width of the main cylinder and in the direction of rotation.
This loading of fiber on the main cylinder, according to this preferred aspect of our invention, is an important difference from a carding operation (using this type of machine, before modification). During such carding, it is desirable to doff all the fiber so that only a very thin layer of fiber is fed and so that all is doffed. In other words, during such carding, it is important to avoid loading the cylinder.
Such loading according to our invention is represented in a sketch in Figure 2, showing how a typical section might look if cut through the card clothing and fiber on a loaded main cylinder (not shown in Figure 2) in a simplified and idealized view. The upper portion 21 shows fiber while the lower portion 22 indicates the location of the card clothing (some of which would be gripping fiber). Figure 3 is a sketched representation of how fibers 24 are gripped by carding teeth 25 of a type that we have used. As some of the fiber shown in the upper portion 21 of Figure 2 is released in clusters 23, and is no longer gripped by the card clothing, such clusters pass through the space between the card clothing (loaded with fiber) and stationary frictional surface elements 14, and are believed to follow tortuous paths, and so to be rolled and become rounded clusters. As the clusters progress around main cylinder 10, they reach the space between the surface of main cylinder 10 and a doffing screen, which is one of the stationary elements 14, specifically element 17, which is a ribbed screen.
We have used as such a ribbed doffing screen 17, a screen such as has previously been used underneath commercial cards (probably shown under the main cylinder in Fig. 101 on page 45 of Klein's Manual) for the different purpose of removing waste. We prefer, however, to doff our fiber clusters through screens with larger spacings between the ribs. One type of preferred screen is described now with reference to Figure 4. The ribs 31 of such screen run transversely (i.e. parallel to the axis of main cylinder 10) and are shaped conveniently with triangular cross-sections, with smooth bases that are spaced radially from the surface of main cylinder 10, and are separated also transversely along their lengths from each neighboring rib, so the rounded fiber clusters may continue to roll in the arcuate space between main cylinder 10 and the frictional surfaces that are the bases of the ribs of the screen, but may also emerge between the ribs, because of centrifugal force. This is represented in Fig. 5, which shows clusters 23 emerging between ribs 31, after being released from the loaded fiber 21 in the peripheral space between the ribs 31 and main cylinder 10. Any loose fiber or incompletely-formed cluster is less likely to emerge from the processor through the transverse spaces, and such fiber masses as do not emerge may roll back down the sides of the ribs to reenter the arcuate space around main cylinder 10. As the fiber clusters emerge, they may be collected, e.g. under low suction, and delivered, e.g. for packing and shipping, or for further processing, by an air conveying system. An important advantage of fiberfill in the form of round clusters which do not readily entangle, is the ability to transport them easily by blowing.
As will readily be understood, a doffing screen may advantageously be used to doff clusters made on other types of machines, different from the preferred type according to our invention.
The next element 18 may also be a screen that acts as a further doffing screen, and performs a similar function. The last element 19 may also be a screen, referred to as a back bottom screen; this element is preferably, however, a plate to provide a frictional surface without doffing. Element 19 may be connected to licker-in basket 11A, as shown in Fig. 1, to avoid loss of fiber from the machine at this point.
Although five frictional surface elements 14 are shown in Fig. 1, it will be understood that the invention is not limited to only five such elements, and more or less may be used, if desired. Indeed a larger number were used is Example 3.
We have found the following aspects affect the process of our invention and the resulting products. With regard to the card clothing on the main cylinder, increasing point density generally reduces the potential to form a compressible fiber loading on the main cylinder, which leads to making clusters that are more dense, less rounded and less acceptable for end uses like pillows and bedding. Conversely, a lower point density generally allows for more fiber loading of the main cylinder, and generates a topography that is more conducive to fiber cluster making. A more aggressive tooth angle is preferred with fibers having higher degrees of slickness. Even a very aggressive tooth angle may not be sufficient when the point density gets extreme, e.g. more than 800 ppsi (points per sq in, and equivalent to about 124 points per sq cm), as this will eventually make loading practically impossible and so cluster formation will also not be possible. Less aggressive teeth will not hold highly slickened fibers, and this will reduce the potential to form an acceptable cluster. With semi-slick and dry fibers, a less aggressive tooth is required to (1) prevent overloading the main cylinder and (2) allow a stable load and topography due to higher fiber-fiber & fiber- metal friction to achieve good fiberball (cluster) formation. The speed of the main cylinder should be matched to the fiber feed rate. If the speed is not high enough, then the main cylinder, as well as the licker-in, can overload, and overloading leads to unacceptable cluster formation, and may even damage the machine. Once the main cylinder has reached a sufficient speed to satisfy the fiber feed rate, stable loading and good cluster formation will occur. Increasing the speed without increasing fiber feed will usually result in smaller, denser clusters. The fiber feed rate should be tuned to the spacings between the frictional surfaces and the main cylinder, and to the speed of the main cylinder. If the clearances are too tight, then this can overload the main cylinder, or make very tight, dense non-round clusters. As the clearance is increased, then the balls may become more hairy, i.e. have more free ends. Higher feed rates can be accommodated with appropriate clearances and speed to give good clusters. The clearances (spacings) between the main cylinder and the frictional surface elements should not be too tight, or this will cause very dense loading of clothing and lead to cluster forms that may be unacceptable. The spacings need to be adjusted to achieve a stable loading (topography) and can be used to help change the average ball diameter. These spacings may be adjusted by conventional means, such as slots in the rims of the elements 14, with bolts on the main cylinder and nuts to tighten and fix the elements at the desired spacing, as shown in Fig. 4.
As with conventional cards, the various elements 14 surrounding the circumference of the main cylinder may themselves be surrounded by removable sections of covering plates to retain any loose fiber that would otherwise escape, but these are not shown in the interests of clarity and simplicity.
The invention is further described with reference to the following Examples, in which all parts and percentages are by weight, unless otherwise indicated. For test procedures and in other respects, reference may be made to the Marcus U.S. Patent Nos. 4,618,531, 4,783,364 and 4,794,038, and 4,818,599, which are all hereby specifically incorporated herein, by reference. Different feed fibers may require different process and/or machine features for appropriate cluster-formation to be performed, so different feed fibers have been processed. Some of the different feed fibers are exemplified below, and others may be processed, by suitable adjustment of the various process and apparatus features mentioned. In the first Example, we processed slickened spirally-crimped fiber, because the 3-dimensional crimp of such fibers is preferred for ease of ball formation, and slickened fiberfill is also generally preferred for aesthetics.

EXAMPLE 1

A tow of asymmetrically jet-quenched, drawn, slickened, poly(ethylene terephthalate) filaments of 4.5 den (5 dtex) was prepared conventionally, without mechanically crimping, using a draw ratio of about 2.8X, applying a polysiloxane slickener in amount about 0.3% Si OWF, and relaxing at a temperature of about 175_°C in rope form. The rope was then cut into 32 mm (about 1.25 inches) staple, and relaxed again at about 175°C. The crimp developed by this process is 3-dimensional in nature and is a non-chemical approach to achieving a spiral-type of crimp. The staple was formed into a bale, compressed to a density of approximately 12 Ib/cu. ft (about 192 Kg/cu m).
The staple was opened using a Masterclean^R opener (available from John D. Hollingsworth On Wheels, Greenville, SC) and then manually charged to the hopper section of a CMC Evenfeed (available from Rando Machine Company, Macedon, NY), which presented a uniform amount of opened feed fiber across the width of the processor.
The processor was as shown in Figure 1, being a 40 inch (1 meter) wide card (available from John D. Hollingsworth on Wheels, Greenville, SC) modified so as to have the following essential elements:

(1) Feed roll 12 (2.25 inch diameter, i.e. almost 6 cm) with feed plate 13 whose function is to meter fiber to licker-in 11. Feed roll speed was controlled independently with a separate DC motor and drive. Fiber throughputs were determined by weighing product delivered by the processor over a prescribed time period. Feed roll 12 rotates in a counter-clockwise direction as shown.
(2) Licker-in roll 11 (9 inch diameter, about 23 cm) whose function is to remove fiber delivered from the space between feed roll 11 and feed plate 12 and present it to main cylinder 10. For this Example, the licker-in roll speed was ratioed to the main cylinder, i.e. both used the same mechanical drive. (This is not necessary, as independent speed control of the licker-in has been evaluated across a wide range of 100-950 rpm and found to have little effect on ball formation, or even on their uniformity and/or density). The licker-in clothing was standard 24 ppsi (about 4 pts/sq cm) wire (available from John D. Hollingsworth On Wheels, Greenville, SC). Licker-in roll 11 rotates in the same direction as feed roll 12, but at a higher surface speed.
(3) A 50 inch (about 1.3 meters) diameter main cylinder 10 clothed with a low point density (132 ppsi, about 20 pts/sq cm), moderately aggressive tooth angle (about 25 positive) clothing (available from John D. Hollingsworth On Wheels, Greenville, SC). This is a preferred clothing for use with fibers coated with polysiloxane slickeners. This clothing allowed highly slickened fibers to load the main cylinder under the conditions of operation herein in such a fashion as to form an equilibrium 3-dimensional surface topography of fibers embedded in the clothing voids, but still exposed enough of the wiring points to draw fibers away from the licker-in roll and not allow the licker-in to overload. Main cylinder 10 rotates in the opposite direction to licker-in 11 and feed roll 12.
(4) A set of stationary frictional surface elements 14 mounted on the periphery of main cylinder 10. For this Example, the entire periphery was covered with ribbed screens (available from Elliott Metal Works, Greenville, SC). The first screen 15 (referred to sometimes as the upper back screen) was positioned where a standard backplate would normally be positioned in a carding machine. Screen 15 had a rib spacing of a quarter of an inch (about 6mm) and contained 34 triangular shaped ribs, the base of the triangle being located closest to, but spaced from, main cylinder 10 and being nominally three eighths of an inch (about 10mm) in width. The next (top) screen 16 had 11 rectangular-based ribs, with one and a half inches (about 4 cm) rib width and quarter inch (about 6mm) spacing. Both screens 15 and 16 were standard screens that we used as processing screens, because of the narrow spacing between their ribs. The next (upper front) screen 17 was a doffing screen that was custom-made with 23 triangular ribs, of width three eighths inch (about 10mm), spaced half an inch (about 13 mm) apart. The other (bottom front and bottom back) screens 18 and 19 were processing screens, similar to upper back screen 15.

The configuration of these screens on the periphery of the main cylinder was such that staple fibers were forced to unite and begin rolling in the peripheral space around the main cylinder when it reached equilibrium loading (i.e. a steady state condition), which occurred within less than about 10 minutes. Spacing of all screens from the main cylinder was set at 0.080 inch (about 2mm) for this Example. These spacings are adjustable within limits, and may be varied to control cluster density and size.
As indicated, ribbed screens are not the only stationary elements with frictional surfaces which can be used to achieve a good cluster product. We have successfully used elements with smooth solid surfaces in place of the upper back, top and lower back screens, as shown in Figure 1. Solid clothed elements can also be used when mounted with the clothing reversed, so that the teeth point in the direction opposite to that used in carding, and with a wide range of point densities; (these are more expensive to make than smooth plates). Although the frictional elements 14 that we have used have been stationary, appropriate to the design of the type of card we have modified, some cards with movable frictional elements may also be modified for use according to our invention, for instance with rollers or belt-driven flat elements.
Control of product removal is accomplished by using one or more ribbed doffing screens (with adequately wide rib-to-rib spacing) according to our invention. These have been located at the upper and lower front screen locations on main cylinder 10, corresponding to where a card is generally doffed. This doffing location is conventional but is not essential, and an advantage may be obtained with other doffing locations, depending on the design and layout of the operation. Wider doffing spacings have been more useful when doffing with a lower screen, such as 18, as centrifugal force is assisted by gravity underneath main cylinder 10. On the upper front (doffing) screen 17, spacings wider than about half an inch (about 13 mm) have resulted in problems in getting the clusters propelled away from the proximity of the main cylinder. We have also noted that free fiber may emerge with the desired clusters if there in a "window" of width as much as three inches (8 cm). This may not be desirable, in general, when the object is to make clusters efficiently. For bonded products however, as indicated by Marcus, it may be desired to provide a mixture of rounded fiberballs and loose binder fiber, in which case free fiber may provide an advantage.
Several variations may prove effective and desirable. For instance, a screen and rib design similar to a venetian blind concept, using adjustable openings, and designs providing a Coanda effect may be used to assist centrifugal force in removing the clusters from the main cylinder.
For Example 1, the speed of main cylinder 10 was set and controlled at 250 rpm, and the speed of licker-in 11 was adjusted to provide a normalized fiber feed rate of about 80-90 pph/meter (of the order of 40 Kg/hr/m) card width. The speed of licker-in 11 was ratioed to the main cylinder, and was measured at 180 rpm. Spacing of the peripheral frictional elements 14 from the main cylinder (clothing) was set at 0.080 inch (about 2 mm). Using these settings, satisfactory clusters were produced having free fall bulk densities that were satisfactorily uniform, and measured between 0.55 and 0.70 Ibs/cuft (about 9 to about 11 Kg/cu m).
These clusters of our invention (INV) were tested, and compared with refluffable commercial clusters (ART) made from similar fiber using the prior art air-tumbling process described in U.S. Patent No. 4,618,531, measuring their cohesion (in Newtons) and their bulk (measured as heights, in cm, of the loose clusters, rather than for pillows) under loads of 0.01 psi and of 0.2 psi, (corresponding to about 7 and about 140 Kg/sq m) essentially as described in U.S. Patent No. 4,618,531. The clusters compared well with such prior clusters in these tests, as can be seen from the results in Table 1.

EXAMPLE 2

Four different feed fibers were fed in opened condition to the processor as described in Example 1 above, under essentially the same conditions, to demonstrate that ball-like clusters can be made from various types of mechanically-crimped fiber. All four different feed fibers were spun from poly(ethylene terephthalate) polymer supply on a single position of a multi-position commercial spinning machine. Sufficient ends of each type were creeled together to make a suitable crimper denier on a low capacity technical draw machine, were subsequently drawn, mechanically crimped, polysiloxane-slickened (approximately 0.3 % Si OWF), relaxed at 175 _°C to set the crimp structure and cure the slickener, and then cut to 1.125 inch (about 3 cm) staple having the following properties:
As in Example 1, the cohesion and bulk of the clusters were measured and compared with commercial clusters (ART). These measurements (given in Table 2B) indicate that their cohesion and bulk under load varied significantly, depending on the fiber used, and its crimp and configuration, and their cohesion values were not as good as for the spiral crimp fibers of Example 1. Some aspects of the cluster products from these different fibers could possibly be improved by varying the processing conditions.

EXAMPLE 3

The feed fiber for this Example was spun from poly(ethylene terephthalate), of 5.5 dpf (about 6 dtex), mechanically crimped (about 7 cpi, about 3/cm), similarly polysiloxane-slickened (about 0.3 % Si OWF), 7- hole fiber (total void content about 12%), cut to 1.25 inch (about 3cm) staple. This fiber was opened on a Masterclean^R opener, as in Examples 1 and 2, prior to feeding to a fiberball making apparatus.
For this Example, the configuration of the frictional surfaces 14 was somewhat different from that used in Example 1 (and as shown in Figure 1) but the apparatus was otherwise as described hereinbefore. The frictional surfaces 14 were, in order starting from licker-in 11 as follows, with spacings measured from the card clothing on the main cylinder, it being understood that the plates were all smooth or with their card clothing reversed from the normal carding direction, so as not to be opposed to the aggressive clothing on main cylinder 10.
Main cylinder 10 was driven at 270 rpm, and licker-in 11 at about 195 rpm, with a feed rate of fiber to provide about 80-90 pph of clusters. These clusters were well rounded, were easily transported by air, and remained discrete even after repeatedly being compressed by hand, although they had significantly more free ends than the clusters from Example 1. The product was blown into commercial pillow ticks of regular size, using 22 oz (625 g) filling weights equivalent to commercial pillows (filled with clusters), so that they could be rated visually, both when newly-filled and after three standardized stomp and laundry cycles, and were found only slightly less lofty and refluffable than such commercial cluster filling.
Although much emphasis has been given to the desirability of making round ball-like fiber clusters, such as have proved very desirable for filling purposes, our process and machine may be operated to make rounded clusters or other shapes, e.g. ellipsoids, if this is desired, by using a higher point density for the card clothing, and adjusting the clearances. Also hard, more compact fiber clusters may be produced by our process and machine if such are desired, as our invention provides for flexibility of operation.

Claims

1. Lofty rounded staple fiber clusters (23) of average dimension about 1 to about 15 mm, and of average density less than about 1 pound per cubic foot (16 kg/m³) consisting essentially of randomly-entwined, mechanically-crimped synthetic staple fiber of cut length about 10 to about 60 mm, provided the staple fibers are not fibers having both spiral and mechanical crimp in the same fiber.

2. Clusters according to Claim 1, wherein the staple fiber is slickened polyester staple fiber.

3. Clusters according to Claim 1, wherein the denier per filament of the staple fiber is about 4 to 15.

4. Clusters according to Claim 1, wherein the staple fiber is hollow.

5. Clusters according to any one of Claims 1 to 4, consisting essentially of a blend of the synthetic fiber blended with a lower melting binder fiber.

6. Clusters according to Claim 5, wherein the binder fiber is a sheath/core bicomponent with a sheath of lower melting binder material, and a core of polyester or like high melting fiber-forming material.

7. A process for preparing rounded clusters (23) of fibers, comprising feeding a uniform layer of staple fiber onto the peripheral surface of a rotating main cylinder (10) covered with card clothing, whereby the fiber is advanced around the peripheral surface by said clothing and is brought into contact with a plurality of frictional surfaces (14), whereby said fiber is formed into clusters (23) that are rolled into rounded configurations on the peripheral surface, characterized in that there is provided at least one arcuate doffing screen (17), radially-spaced from said clothing, said doffing screen being provided with openings of sufficient size for the clusters to pass through said openings, and to be doffed by emerging through said openings.

8. A process according to Claim 7, wherein said doffing screen (17) is provided with transverse ribs (31) with bases that are spaced radially from said clothing, and that said openings are transverse spaces between said ribs.

9. A process for preparing rounded clusters (23) of fibers, comprising feeding a uniform layer of staple fiber onto the peripheral surface of a rotating main cylinder (10) covered with card clothing, providing a plurality (14) of essentially arcuate frictional surfaces that are spaced radially from said clothing, wherein the radial spacing and frictional characteristics of said frictional surfaces and of said clothing and the rate of feed of said staple fiber are controlled so that said clothing becomes loaded with a compressible layer of fibers, whereby lofty rounded clusters (23) of fibers are formed in the peripheral space between said clothing and said frictional surfaces, and doffing said clusters.

10. A process according to Claim 9, wherein a doffing screen is provided with openings of sufficient size for the clusters (23) to pass through said openings and be doffed thereby.

11. A process according to Claim 10, wherein said doffing screen is provided with transverse ribs (31) with bases that are spaced radially from said clothing, and that said openings are transverse spaces between said ribs.

12. A process according to Claim 8 or 11, wherein said ribs (31) are of triangular cross-section with bases that are spaced radially from said clothing.

13. A process according to any one of Claims 7 to 11, wherein the fiber is advanced around the peripheral surface through a succession of zones between the cylinder clothing and a plurality (14) of arcuate plates spaced radially from the card clothing.

14. A process according to any one of Claims 7 to 11, wherein the fiber is advanced around the peripheral surface through a succession of zones between the cylinder clothing and a plurality (14) of transversely-ribbed arcuate screens with spaces between the transverse ribs.

15. A process according to any one of Claims 7 to 11, wherein at least some of said frictional surfaces comprise card clothing whose tooth orientation is not opposed to the direction of rotation of the main cylinder.

16. A process according to any one of Claims 7 to 11, wherein doffing and transportation of the emerging clusters (23) is assisted by suction and/or blowing.

17. A process according to Claim 16, wherein the rounded clusters are blown into tickings and formed into pillows or other filled articles.

18. A process according to any one of Claims 7 to 11, wherein the staple fiber is fed to the main cylinder (10) in the form of a cross-lapped batt.

19. A process according to any one of Claims 7 to 11, wherein the staple fiber fed to the main cylinder (10) has previously been baled, but is fed to the main cylinder after having been opened.

20. A process according to any one of Claims 7 to 11, wherein the staple fiber fed to the main cylinder (10) has been mechanically crimped.

21. A process according to any one of Claims 7 to 11, wherein the staple fiber fed to the main cylinder is of hollow cross-section.

22. A process according to any one of Claims 7 to 11, wherein the staple fiber fed to the main cylinder has been slickened.

23. A process according to any one of the Claims 7 to 11, wherein the staple fiber fed to the main cylinder is a blend of polyester fiberfill or other high melting fiber blended with lower melting binder fiber.

24. In a staple fiber carding machine comprising a rotatable main cylinder (10) having its peripheral surface covered with card clothing and adapted to rotate in close proximity with a plurality (14) of cooperating frictional surfaces, means to feed staple fiber in a uniform layer onto said main cylinder (10), and doffing means (17), the improvement characterized in that said frictional surfaces cooperate with the card clothing on the peripheral surface of the main cylinder in such a way that fiber clusters are formed by the cooperation between the card clothing and said frictional surfaces, and the doffing means (17) comprises a doffing screen provided with openings of sufficient size for the fiber clusters to emerge.

25. A machine according to Claim 24, wherein said cooperating frictional surfaces are arcuate plates (14,15,16,17,18) spaced radially from the card clothing.

26. A machine according to Claim 24, wherein at least some of said cooperating frictional surfaces comprise card clothing whose tooth orientation is not opposed to the direction of rotation of the main cylinder (10).

27. A machine according to Claim 25, wherein at least some of said cooperating frictional surfaces comprise card clothing whose tooth orientation is not opposed to the direction of rotation of the main cylinder (10).

28. A machine according to Claim 24, wherein said cooperating frictional surfaces are transversely-ribbed (31) arcuate screens with spaces between the transverse ribs, that are spaced radially from the card clothing.

29. A machine according to any one of Claims 24-27, wherein said doffing screen (17) is provided with transverse ribs (31) with bases that are spaced radially from said clothing, and that said openings are transverse spaces between said transverse ribs (31).

30. A machine according to Claim 29, wherein said ribs are of triangular cross-section with bases that are spaced radially from said clothing.