Aerodynamic Spinning Of Composite Yarn

Abstract

It has been found that with the use of air vortex at the initial stages of yarn formation, one can impart a desired light twist to the yarn. This light twist can be used as a pre-twist which supplements regular yarn spinning and provides a yarn with increased twist retention.

Description

This invention relates to a novel aerodynamic method and apparatus for spinning of composite yarn.

Basically, the invention provides a novel and very advantageous method of applying light twist to composite fiber strand at the very beginning of the yarn forming operation. The light twist can also be used as a pre-twist and the strand so pre-twisted can then be subjected to a regular spinning operation to achieve final yarn with increased twist retention.

The method of this invention essentially comprises introducing fibers, alone or together with a tacky substrate, into a defined chamber and forming an air vortex in said chamber. Due to this air vortex, the fibers become helically rearranged and twisted and are then consolidated in such helically twisted condition with a tacky substrate to form spun composite yarn which can be linearly wound-up on a collecting roll. According to another embodiment of this invention, after such initial twisting by an air vortex, the fibers and the substrate may be further twisted by conventional twisting or by means of a false twist spindle prior to their consolidation into yarn. This produces a composite spun yarn with increased twist retention.

The consolidation of the helically twisted fibers with the tacky substrate is effected in accordance with a preferred embodiment of this invention within a groove of a rotatable circumferentially grooved roll into which the fibers combined with the tacky substrate are introduced upon emergence from the air vortex chamber and in which they are condensed and consolidated to form spun yarn. Additional fibers of the same or different type can be introduced directly into the groove of the roll during consolidation; these additional fibers will be combined with the other components and will form a modified yarn with desired characteristics. The groove of the circumferentially grooved roll is preferably provided with slots at its bottom and air suction means are then mounted within the grooved roll to impart suction through these slots and thereby produce a strong holding and wrapping action of the yarn against the bottom of the groove during consolidation.

It should also be noted that the grooved consolidating roll can be rotated at very high speeds since, according to this invention, output speeds of above 1000 feet per minute are achievable. However, it has been found that when speeds in excess of about 300 feet per minute are used the fiber-polymer stream supplied into the groove of the consolidating roll will be exposed to strong centrifugal and air friction forces. These forces amplify as the speed of the roll increases and even when the roll is provided with suction means therewithin, the control and consolidation of the fibers with the polymer within the groove, which is generally V-shaped, is rendered very difficult. In particular, the upper layer of the fiber mass, not adequately engaged by the suction from within the consolidating roll, may slip or shift during high speed operation thereby resulting in the formation of unevenness in the yarn. This is particularly pronounced in the production of coarser yarns, requiring a greater amount of fibers, as well as in the case of long, coarse and heavy fibers such as bast fibers, asbestos fibers, glass whiskers or metallic fibers which have a tendency to shift or even fly off the roll due to insufficient suction forces at high rotational speeds of the roll, particularly at output speeds exceeding 300 feet per minute.

It has been found that these problems can be substantially reduced or entirely obviated by providing a suction not from within the roll but rather from outside of the grooved roll with approximate design of the groove such as to retain said fiber generally on the sides of said groove and then at a predetermined point, removing the suction and blowing said fibers from the sides towards the center of the groove where they will be combined and consolidated with the polymer substrate. In this manner, the suction forces are not offset by the centrifugal forces but rather aided thereby to achieve a more satisfactory fiber control and consolidation and to eliminate to a substantial degree the fiber surface to air friction dragging forces.

One design of the grooved roll which will achieve this objective comprises forming a circumferential channel over and above each side of the V-grooved surface of the roll, which channel is provided at the top with holes or slots leading to the outside of the roll where a suction device is mounted. When the fibers are introduced into such channeled groove and air suction is applied through said slots, the fibers will be projected into said channel, aided by the centrifugal forces of the roll axially revolving at high speed. The fibers will remain within said channel on the sides of the V-grooved roll until the suction is withdrawn and eventually replaced by blowing air from an air blowing device positioned at a predetermined point of the roll's path of travel. At this point the fibers will be projected towards the middle of the groove and will be combined and consolidated with the polymer substrate which is present therein. It should be noted that the channels on each side of the grooved surface of the roll can be of any desired shape or configuration, although they will usually be U or V shaped. The fibers may be supplied into the groove and subsequently into the channels from one or two separate sources, thus resulting in the accumulation in each channel of the same or different fiber materials or blends thereof. This fiber supply is preferably effected by means of a double position fiber lickerin roller having protruding sharp teeth or needles and eventually interposed projecting blades on its peripheral surface. Such likerin rollers shred a fleece or a fiber web into desired fibers and the fiber feed from these rollers is transferred by suction or the like into the vortex chambers or directly into the groove of the grooved roll.

In this regard, it should be noted that although this invention primarily concerns the imparting of the twist to yarn by an air vortex means, the embodiment whereby the fibers are accumulated on the sides of the groove in channels especially provided for that purpose is applicable to any yarn producing process and apparatus using such grooved rolls for fiber-polymer consolidation, irrespective of whether or not a vortex pre-twist has been imparted.

Furthermore, the air vortex may be applied both to the fiber and the tacky substrate simultaneously or it can be applied only to the fibers which will thereby achieve the desired helical configuration. These fibers will then be transferred onto the grooved roll from the air vortex chamber and will be combined and consolidated therein with a tacky substrate which will be supplied at the same time into said groove.

The air vortex forces are applied in a specially provided vortex chamber positioned just above the groove of the consolidating roll. Usually, such chamber is of generally tubular or conical shape. Two such chambers may be used side by side to supply fibers from different sources as already mentioned above.

Following the grooved roll there may be provided a twist imparting device, such as a false twist spindle, through which the resulting yarn will pass. This twisting device will impart additional twist to the yarn, which will be transferred by the yarn itself to the point of consolidation within the groove of the roll. At this point, the twist will be substantially retained in the yarn due to interfiber and intermolecular slippage occuring during twisting, aided by the restraining braking forces produced by air suction and the centrifugal forces of the axially rotating roll, and enhanced by the cohesion forces of the vortex feed-in material in already pre-twisted condition. A good spun yarn with increased twist retention is obtained in this way.

The tacky substrate which is used with the fibers in accordance with the present invention, and which may be introduced either into the air vortex chamber or directly into the groove of the consolidating roll may be in any desired condition. For example it may be in the form of extruded tacky polymer strands or filaments or in the form of a mist or spray of tacky particles or something of this sort. Polymers such as polyethylene, polypropylene, polyamid, polyester, PVC and the like are eminently suitable for this purpose. Similarly suitable forms of thermosetting resins can be also utilized such as acrylic latices, phenolics, urea compounds, alkyds, epoxies and the like. Other fiber bonding materials such as the acrylonitriles, rubber and silicone based compounds, polyurethanes and plastisols can be applied. The staple fibers may also be any desired natural or man-made fibers, including glass fibers, metallic fibers, asbestos fibers, fibrids and the like.

The apparatus according to the present invention basically comprises: at least one air vortex chamber; means for introducing staple fibers into said vortex chamber; means for imparting vortex forces to said staple fibers within said chamber; a consolidating roll with at least one circumferential groove below said chamber; means for transfering the fiber supply from the air vortex chamber into the groove of said consolidating roll; means for simultaneously introducing a tacky substrate into the groove of the roll; and means for consolidating said fibers with said tacky substrate within the groove of said roll to produce spun yarn which can subsequently be linearly wound on a collecting roll.

The tacky substrate can be introduced either directly into the groove of the consolidating roll or through the air vortex chamber, in which case it is first introduced into the air vortex chamber and then into the groove of the roll together with the fibers. In this latter situation the fibers will already be helically arranged around the tacky substrate within the vortex chamber, and will then be transferred together with said tacky substrate into the groove of the consolidating roll. In addition to the tacky substrate, there may be fed into the vortex chamber and/or into the groove of the consolidating roll a carrier strand about which the yarn is eventually formed and about which the consolidation takes place.

As already mentioned above, the groove of the consolidating roll is preferably V-shaped and is provided with holds or slots at the bottom thereof while suction means are provided within the roll to hold by suction the fibers and the substrate against the bottom of the groove during consolidation thereof into yarn. In another embodiment, channels may be provided over and above the sides of the groove with holes or slots at the top and suction means are provided outside of the roll to hold the fibers against the sides of the groove within said channels, then the suction is withdrawn and preferably blowing air is applied to move the fibers towards the center of the groove and combine and consolidate them with the tacky substrate in the said center of the groove. This second embodiment is particularly preferred at high output speeds in excess of 300 feet per minute.

Furthermore, a twist imparting device, such as a false twist spindle, may be provided following the consolidating roll, through which the obtained yarn is passed. The twist generated by this device is transferred back into the groove and is applied to the yarn being formed as a positive additional twist. In this connection, it has been established that the amount of retained true twist imparted to the fiber-polymer substrate strand by a suitable false twist type friction spindle is closely related to the degree of interfiber and intermolecular slippage produced within the fibers and the polymer matrix. Thus, the pre-twist obtained by air vortex means minimizes and offsets the counter twist created by the positive twisting torque of the false twist spindle at the initial point of consolidating engagement of the fibers with the polymer substrate within the groove of the consolidating roll, and enables to produce a spun yarn with substantially increased twist retention.

The invention will now further be described with reference to the appended drawings, in which:

FIG. 1 is a partly sectional side elevation view of one embodiment in accordance with this invention showing an air vortex pre-twist chamber in the initial stage of composite yarn producing operation;

FIG. 2 is a partly sectional plan view of another embodiment of this invention showing two air-vortex pre-twist chambers for fiber pre-twisting; and

FIG. 3 is a partly sectional side view of still another embodiment of the arrangement in accordance with this invention.

In FIG. 1, an air vortex chamber 10, which is of a generally tubular shape, is provided within a metal block 11 and air vortex is produced within said chamber by sources of compressed air 12 and 13. Fibers are fed into the air vortex chamber 10 from a lickerin roller 14 mounted within the same block 11 and having outwardly projecting needles 15 on its surface. The fibers are forwarded from a fiber web 16, through supply roller 17, onto the surface of lickerin roller 14 where they are attenuated by the projecting needles 15. These fibers are then blown out into the air vortex chamber by means of an air blowing device 18 mounted within roller 14. Preferably two such fiber feeding arrangements are provided within the block 11, one on each side of air vortex chamber 10.

A tacky polymer substrate is introduced simultaneously with the fibers into air vortex chamber 10 from an extrusion nozzle 19. In this particular example the substrate is extruded in the form of a tacky polymer filament into the air vortex chamber 10 where the fibers wrap around such tacky filament assuming a helical configuration and forming a slight twist or pre-twist in the composite strand 20 issuing from said air vortex chamber 10.

In addition, a ready made filament 21 or yarn 22 can be introduced through the middle of the extrusion nozzle 19 or in any other desirable manner into the air vortex chamber 10 where it may serve as a carrier. In this manner, the polymer substrate and the fibers will be held and carried by such carrier and the latter will constitute the core of the ultimately formed yarn. Preferably, such carrier is fed through the extrusion nozzle in such a way that when it leaves the same, it becomes coated with a film of tacky substrate supplied from the extruder. The fibers are then wrapped around this tacky strand in helically rearranged manner in the air vortex chamber 10. To facilitate downward movement of the materials in this air vortex chamber 10, additional air is blown from above by air blowing devices 23 and 24.

Upon its exit from the air vortex chamber 10, the strand 20 which has acquired a light twist is forwarded to and through the groove of a rotatable grooved consolidating roll 25. This groove 26 provided circumferentially on the roll 25 is generally V-shaped and at the bottom thereof there may be holes or slots 27 leading inside the roll 25 where an air suction device (not shown) may be mounted. This strand 20 is consolidated within such groove 26 of rotating roll 25 and the air suction from inside, when provided, helps to produce a stronger hold against the bottom of the groove during consolidation. This is particularly important if one desires to incorporate additional fibers at this consolidation stage, when the substrate is still somewhat tacky. Such additional fibers can be fed by another lickerin roller 28 having needles 29 projecting on its surface. The fibers are formed by supplying a fibrous web 30, through supply roller 31, onto the surface of such lickerin roller 28, where the web is shred into staple fibers, which are then transferred onto the surface of the roll 25 and within its circumferential groove by suction from within said roll 25.

Upon consolidation within the groove 26 of the rotating roll 25 and coagulation of the tacky substrate, the obtained yarn with a liqht twist can simply be forwarded through a tension roller 32 to the winding arrangement 33 where it is wound on a collecting roll 34.

If desired, the yarn can also pass through oscillating rolls 35, 36 to further condense the same into a round strand which is then wound on the collecting roll 34.

However, the preferred treatment of this yarn is to apply to it a strong twist by a twist imparting device 37. This twist is transmitted through the yarn itself and is retained in the yarn at the point of consolidation within the groove 26 of the roll 25, due to interfiber and intermolecular slippage at this point. This enables to form a yarn with increased twist retention which is then simply and linearly wound on the collecting roll 34.

In the embodiment shown in FIG. 2, instead of having one air vortex chamber, there are provided two air vortex chambers 40a and 40b, positioned side by side within block 39. The air vortex within these chambers is imparted from a source of compressed air 41 and the fibers are supplied from two lickerin rollers 42a and 42b also positioned side by side and provided with needles 43 projecting upwardly on their surface and eventually with blades 44 mounted in staggered arrangement between the needles. This enables a good shredding of the incoming fiber web into staple fibers which are fed into the air vortex chambers 40a and 40b and imparted with a twist therein. The so twisted or pre-twisted fibers are then fed within the V-shaped groove 46 of a rotating consolidating roll 45. Due to a very fast axial rotation of this roll 45 (above 300 feet per minute) it is impractical to use suction from within to hold the fibers against the groove and instead of this a channel 47 is formed over and above each face of the V-groove 46. At the top of these channels, holes or slots 48 are provided leading towards suction imparting devices 49, 50 within block 39. These suction devices, aided by the fast axial rotation of the roll 45 pull the fibers entering the grooves 46 from air vortex chambers 40a and 40b into the channels 47 wherein these fibers are held while they travel on the consolidating roll 45. At a predetermined point, these fibers are blown towards the middle of the groove 46 by air blowing devices 51, 52 while a tacky substrate is also introduced into the middle of the groove at 53. The whole is combined and consolidated by imparting a twist from below to form spun yarn 54 with increased twist retention, which can be linearly wound-up on a collecting roll. In particular, when two air vortex pre-twist chambers are employed side by side a yarn with plyed effect can be directly produced in accordance with this arrangement.

In the embodiment of FIG. 3, an air-vortex chamber 40 is provided and air vortex is produced therein by a source of compressed air 41. Fibers are introduced into said air vortex chamber 40 from lickerin roller 42 provided with needles 43 and blades 44 on its surface. This lockerin roller 42 is driven by a driving mechanism 55 in the direction shown by the arrow in the middle of said roller 42. The fibers are produced by this licker-in roller by shredding a fleece or fiber web 56 is fed by supply roller 57 driven by driving mechanism 58 in the direction shown by the arrow in the middle of said roller.

Simultaneously, a carrier strand 60 is unwound from bobbin 59 and forwarded through extruder 61 and into the air vortex chamber 40, aided by an air flow through tube 62. Also, a tacky polymer substrate is introduced into extruder 61 through inlet 63 and extruded into the air vortex chamber 40 so as to coat the carrier 60 with a layer of tacky substrate. Within the air vortex chamber 40 the fibers are helically wrapped around such tacky carrier to provide a desired pre-twist. Then, upon its exit from the air vortex chamber, the combined material is consolidated within the V-shaped groove 46 of the rotating consolidation roll 45 driven by driving mechanism 64. Air is blown into the groove of said roll 45 through inlet 65 to help in the consolidation of the yarn and a protective plate 66 is provided at this point to prevent any fly-away of the fibers. The yarn exiting from the consolidation roll 45 is further twisted by a false twist spindle 67 and then forwarded through a tension roller 68 towards a winding station.

It should be noted that the specifically described and illustrated embodiments are not at all limitative and many variations thereto may be made by men familiar with this art. The provision of air vortex means at the beginning of the yarn forming operation is the gist of this invention and any application thereof to form spun yarn falls within the scope of the invention as defined by the following claims.

Claims

The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:

1. Method for producing spun yarn which comprises forming an air vortex in a defined chamber, introducing into said chamber staple fibers and permitting said fibers to become helically twisted by said air vortex, consolidating said helically twisted fibers with a tacky substrate to form spun yarn, and linearly winding up said yarn on a collecting roll.

2. Method according to claim 1, in which said tacky substrate is also introduced into said air vortex chamber and the fibers are helically twisted about said substrate therein and after said fibers have been so twisted about said substrate in said chamber, they are further twisted by a false-twist spindle outside of said chamber to produce yarn with increased twist retention.

3. Method according to claim 2, wherein together with the tacky substrate and staple fibers, there is introduced into the defined air vortex chamber a ready strand about which the yarn is formed.

4. Method according to claim 2, wherein the tacky substrate is directly extruded into said defined chamber and the fibers are fed thereinto from each side of the extruded substrate and into the air vortex within said chamber.

5. Method according to claim 1, comprising forwarding simultaneously and helically twisted fibers from the air vortex chamber and said tacky substrate into and through a groove of a rotatable circumferentially grooved roll and imparting to said fibers and said substrate a strong holding and wrapping action against said groove whereby said fibers and said substrate are condensed and consolidated to form spun yarn.

6. Method according to claim 5, comprising providing the bottom of said groove of the circumferentially grooved roll with slots and imparting suction to said slots from within the roll, thereby producing the strong holding and wrapping action of said fibers and said substrate against the bottom of the groove required during formation of said spun yarn.

7. Method according to claim 5, comprising forming said groove of the circumferentially grooved roll as a general V-shaped groove, providing said groove with circumferential channels over and above its side faces, forming slots at the upper end of said channels and imparting suction through said slots so as to produce a holding action for the fibers within said circumferential channels on the side faces of the V-shaped groove and, when the fibers have thus accumulated within said channels removing said suction to allow said fibers to project from the channels towards the middle of the V-shaped groove of the roll and be condensed and consolidated there with the tacky substrate to form spun yarn.

8. Method according to claim 7, further comprising, upon removal of said suction, subjecting said fibers within said circumferential channels to an air blowing action to facilitate projecting of the fibers towards the middle of the V-shaped groove.

9. Method according to claim 5, comprising further twisting said yarn being formed within said groove to produce spun yarn with increased twist.

10. Apparatus for producing spun yarn which comprises at least one air vortex chamber, means for introducing staple fibers into said vortex chamber, means for imparting vortex forces to said staple fibers within said chamber, a consolidating roll with at least one circumferential groove below said chamber, means for transferring the fibers from the air vortex chamber into the groove to said consolidating roll, means for simultaneously introducing a tacky substrate into the grooves of the roll and means for consolidating said fibers with said substrate within the groove of said roll to produce spun yarn which can subsequently be linearly wound on a collecting roll.

11. Apparatus according to claim 10, wherein said tacky substrate is adapted to pass through said vortex chamber prior to being introduced into said groove of the consolidating roll.

12. Apparatus according to claim 10, further comprising a twist imparting device following said consolidating roll and means to pass the yarn coming out of the consolidating roll through said twist imparting device to impart to said yarn additional twist.

13. Apparatus according to claim 12, wherein said twist imparting device is a false twist spindle.

14. Apparatus according to claim 10, wherein the groove of the circumferentially grooved roll is provided with slots at the bottom and air suction means are mounted within said grooved roll to impart suction through said slots and thereby produce a strong holding and wrapping action of the yarn against the bottom of the groove.

15. Apparatus according to claim 10, wherein the groove of the circumferentially grooved roll is generally V-shaped and is provided with circumferential channels over and above its side faces, said channels having slots at the top, and air suction means are provided outside of the roll to impart suction through said slots and thereby produce a holding action for the fibers within said circumferential channels on the side faces of the V-shaped groove, and means are provided to remove said air suction at a predetermined point and thereby allow the fibers accumulated within the channel to project towards the middle of the V-shaped groove of the roll and be condensed and consolidated there with the tacky substrate.

16. Apparatus according to claim 15, wherein at the point where air suction is removed, air blowing means are provided to facilitate projection of the fibers towards the middle of the groove.

17. Apparatus according to claim 16, further comprising guide means in front of the grooved roll so that staple fibers being blown towards the middle of the groove cannot fly out due to rotational forces of the roll and air blowing.

18. Apparatus according to claim 10, further comprising an extruder above said vortex chamber for extruding the tacky substrate directly into said chamber.

19. Apparatus according to claim 10, in which said means for introducing staple fibers into said vortex chamber consists of a double position fiber lickerin roll having sharp teeth or needles projecting from its surface and blades mounted in staggered arrangement among said teeth or needles.

20. Apparatus according to claim 10, further comprising means for introducing a ready made carrier strand into said vortex chamber around which yarn is ultimately formed.