EP0375242A2

EP0375242A2 - Manufacture of roving

Info

Publication number: EP0375242A2
Application number: EP89312927A
Authority: EP
Inventors: Elbert F. Morrison
Original assignee: Burlington Industries Inc
Current assignee: Burlington Industries Inc
Priority date: 1988-12-12
Filing date: 1989-12-11
Publication date: 1990-06-27
Also published as: CA2005018A1; JPH02259121A; EP0375242A3; CN1043353A

Abstract

A process and apparatus for the production of roving uses vacuum spinning techniques. Specifically, a fibre mass, or sliver (S), is drafted through a drafting zone (14) and passed into a hollow, rotatable shaft (26), the shaft having a central through passageway (31) and a plurality of radially oriented orifices (38). The shaft (26) is mounted in a housing (24) to which a vacuum is applied as the fibre mass passes through the rotating shaft. Trailing free ends of a minor portion of the fibres are pulled into the orifices (38) and, as the linear movement of the fibres continues, are pulled back out of the orifices and are wrapped about the remaining core fibres to form a roving.

Description

This invention relates to the manufacture of roving, an intermediate product between the initial sliver and final yarn product. More specifically, roving is generally considered to be in a condition one step removed from finished spun yarn. In other words, roving is fibre stock or sliver which has been drawn, drafted and usually twisted in preparation for a following operation, such as ring spinning, typically used in the production of yarn.
Those familiar with the roving process in yarn manufacturing appreciate the various problems associated with conventional roving forming techniques. Conventional flyer roving equipment (which imparts a real twist of .5 to 1.5 turns in the fibres), for example, has a number of complicated mechanical parts and mechanisms resulting in down time and maintenance problems; the equipment is relegated to slow speeds due to the use of a flyer, and it is subject to drafting problems in spinning due to actual twist variations. Additional difficulties are experienced in creeling and doffing operations, and automation of the process is problematic.
In conventional rub roving, the sliver strand is sandwiched between two aprons that oscillate in opposite directions causing the sliver to roll between the aprons, adding strength as a result of the rolling and interlocking of fibres. Rub roving equipment also has disadvantages however. For example, while permitting high speed and overall efficiency, it also has complicated mechanical assemblies and is costly to operate. In addition, the process lends itself to erratic drafting patterns, especially in dyed stocks, causing uneven yarn in spinning. This is also the result of the aprons not being consistent over the entire length of the roving surface, which in turn causes drafting forces to vary.
The present invention seeks to eliminate the above objections and disadvantages by utilizing a very simple mechanical device which produces a roving that does not have twist, either real or false.
According to one aspect of this invention there is provided a process for the production of roving, the process comprising the steps of:

(a) drafting a sliver of fibres to form a drafted sliver,
(b) forming the drafted sliver into a roving, and
(c) winding said roving on a take up reel; characterized in that step (b) comprises passing the drafted sliver through a rotating nozzle at a pressure below atmospheric pressure, to cause at least a minor portion of the fibres to be wrapped about a core of remaining fibres to form said roving.

Preferably step (a) comprises:

(i) feeding a sliver of fibres from a sliver storage area to a drafting zone;
(ii) drafting the sliver of fibres to a predetermined weight as the sliver passes through said drafting zone;

(i) passing the drafted sliver in a linear direction into a hollow shaft rotatable about an axis generally coincident with the said linear direction, the shaft having a plurality of orifices extending radially outwardly from the hollow shaft;
(ii) applying a vacuum through the orifices sufficient to attract free ends of a minor portion of the fibres into said orifices while a major portion of the fibres remains in the hollow shaft;
(iii) rotating said shaft as said drafted fibres pass therethrough to thereby wrap the said free ends of the minor portion of the fibres about the major portion of the fibres to form a roving; and

Conveniently said hollow shaft, upstream of the orifices, has a diameter of about 9.5 mm.
Advantageously said hollow shaft, downstream of the orifices, has a diameter of about 4.7 mm.
Preferably said orifices each comprise a tapered bore.
Conveniently said orifices taper from a diameter of about 9.5 mm to a diameter of about 4.7 mm.
Advantageously the process is carried out without applying substantially any twist to the fibres.
During step (c), the roving may be wound at about 90 to 136 m/min.
The sliver may have a grain weight of from about 1.49 grammes/m to about 12.96 grammes/m.
Conveniently the minor portion of fibres comprise about 5 to about 20% of the drafted sliver.
According to a second aspect, this invention provides an apparatus for the production of roving, said apparatus comprising means for drafting a sliver of fibres to form a drafted sliver; and means for forming said drafted sliver into a roving; characterized in that the roving forming means comprises a rotating nozzle maintained at sub-atmospheric pressure as the sliver of fibres are passed therethrough, the arrangement being such that trailing free ends of a minor portion of the fibres are wrapped around a core of remaining fibres to form the roving.
This invention applies known vacuum spinning techniques to the production of roving and, as a result, achieves high quality roving for use in subsequent yarn forming processes.
The application of vacuum spinning in the textile industry is not new. However, it has heretofore been applied only in the making of a yarn product. For example, in commonly assigned U.S. Patent Nos. 4,719,744, 4,713,931 and 4,507,913 methods and apparatus are described for producing vacuum spun yarns. In U.S. Patent No. 4,635,435 a method and apparatus are described for vacuum spinning yarns directly from sliver.
In the present invention, vacuum spinning technology is applied to the manufacture of roving which has neither real nor false twist. Moreover, the roving process of this invention eliminates many of the problems associated with conventional flyer and rub roving processes, and produces roving which is at least the equal in quality to roving formed by these conventional processes.
In one exemplary embodiment of the invention, sliver is coiled into a sliver can by conventional drawing equipment. The sliver, which may comprise long or short staple fibres, i.e. from about 2.5 cms (1 inch) to about 15 cms (6 inches) in length, is then fed from the can into a conventional draft system, e.g. the same type of drafting system used in conventional flyer and rub roving processes. As the drafted stock passes through the back draft roll into an apron zone, it is then drafted through the vacuum nozzle assembly as described below.
Fibres of the sliver are pushed and drawn into an entry slot formed in a hollow shaft, or nozzle rotatably mounted in a housing. At this point, the fibres are subject to the dual action of the feed rolls and a vacuum created (by any suitable means) within the nozzle. As the fibres pass through the nozzle, a small portion of the surface fibres' free ends are sucked radially outwardly relative to the direction of travel of the fibre mass, into peripherally located orifices. The radially displaced fibre ends are then immediately pulled out of the orifices as the fibre mass continues its linear movement, and are wrapped around the remaining centrally located core fibres by the rotation of the nozzle. These wrapper fibres preferably constitute from 5 to 20% of the fibres, and experiments have shown that approximately 10% of the wrapped fibres tend to straighten out during subsequent spinning drafting.
The number of wrapper fibres can be controlled by nozzle rpm, number and size of orifices in nozzle, vacuum pressure, etc. Due to this ability to control the number of fibres wrapped around the core and how tightly they are wrapped, a roving with superior drafting properties can be produced.
The roving is taken up by a take-up roll and wound onto a roving tube at high speed similar to a conventional yarn winder. Winding speed is between 91 and 136 m/min (100-150 yds/min). These roving tubes can be hung in a ring spinning frame creel for spinning either single or double creel, so that a wide variety of yarn counts can be produced.
The roving process in accordance with this invention is very flexible as to roving size. Moreover, tests show that if wrapper fibre ratio remains at 15% or less, and these fibres are not wrapped with high pressure, the yarn is equal in quality to roving produced by flyer and rub roving processes.
The process of this invention also lends itself to automation similar to that now employed in rub apron roving in long staple fibre production (but not in the short staple fibre production). It is believed that this invention will be applicable to both long and short staple fibre production.
Another advantage of preferred embodiments of the invention is that, as in known vacuum spinning processes, suction in the nozzle eliminates a large volume of heavy waste, such as vegetable matter, dirt, dust, etc., giving the stock a cleaner content.
Accordingly, preferred embodiments of this new roving concept have many advantages over current systems and techniques used to produce roving.
As described further herein, in adapting the known vacuum spinning technology to the production of roving, the configuration of the nozzle is similar to that utilized in the production of yarn, with the exception of having to provide a larger diameter through passageway and radial orifices in order to accommodate the much larger roving dimensions. In addition, the drafting system is necessarily larger and of heavier construction.
In order that the invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a schematic diagram of the apparatus utilized in this invention;
FIGURE 2 is a schematic side view of roving produced by the appartus of this invention;
FIGURE 3 is a side view of one design of nozzle for use in this invention; and
FIGURE 4 is a sectional view through the nozzle of Figure 3.

With reference to Figure 1, a schematic representation of apparatus in accordance with this invention is illustrated.
Generally, the apparatus 10 includes a sliver can or bin 12 from which a sliver S is drawn by a drafting assembly 14 which includes feed roll sets 16, 18 and 20. The draft system acts upon the fibres in the sliver S in a conventional manner and feeds the fibres into a vacuum nozzle assembly 22.
The nozzle assembly 22 comprises a housing 24 and an elongated hollow shaft 26 mounted for rotation therein. The shaft has a first entry end 28 and a second exit end 30. A through passageway 31 extends from the end 28 to the end 30. The passageway includes a first portion 32 adjacent the first end 28, an interior chamber portion 34 close to, but spaced from, the first end 28, and a third portion 36 that extends from the chamber portion 34 through the nozzle to the second end 30. The first or entry portion 32 has an entry diameter of about 9.5 mm (3/8 inch) significantly larger than the 4.7 mm (3/16 inch) diameter of the third or exit portion 36, and is connected thereto by a tapered conical portion 33.
About the periphery of the shaft, at the juncture of shaft passageway portions 32, 36, i.e. at the chamber portion 34, there are provided a plurality of orifices 38 extending from chamber 34 radially outwardly through the shaft 26, to provide communication with the interior of the housing 24. The number of orifices may be varied but is preferably within the range of two to six or more. In addition, the passages defined by the orifices may extend substantially perpendicular to the passageway 31, or at an inclined angle relative thereto.
In a preferred arrangement, the housing 24 is connected via inlet 50 to a vacuum pump or other vacuum source (not shown).
Bearings 40, 42 mount the shaft for rotation within the housing. A pulley or gear 44 is press-fit to an exterior cylindrical surface 46 of the shaft 26 so that rotation of the gear effects rotation of the shaft 26. Gear 46 is connected to a drive motor (not shown) or other suitable drive means via belt or chain 48.
A pair of take-off rolls 52 is mounted adjacent the outlet end of the nozzle, along with a take-up roll 54 and a roving tube 56 upon which the roving R is wound at speeds of up to 91 to 136 m/min (100-150 yds/min). A conventional transverse motion device 59 is utilized to facilitate winding of the roving on the tube 56.
In use, the fibre mass or sliver S, having a grain weight of from about 1.49 grammes/m (25 grains/yd) to about 12.96 grammes/m (220 grains/yd), is fed in a linear direction through the drafting assembly 14, after which the mass is pushed and drawn into the interior of the nozzle assembly 22. In this regard, it will be appreciated that the air flow created in the housing, e.g. via connection of a suitable vacuum source to the housing inlet 50, assists in drawing the fibres into the nozzle assembly along the linear feed direction, while they are at the same time being pushed by feed roll set 20.
As the fibres pass beyond the entry of the nozzle, some of the fibres, which have free trailing ends, are deflected, i.e. radially displaced, by reason of the air flow into the radially oriented orifices 38, but are immediately pulled back down by the continued linear movement of the fibre mass. At the same time, these radially displaced fibre ends are wrapped around the remaining core fibres by reason of the high speed rotation of the nozzle. It will be appreciated that the rotation of the shaft, simultaneously with the creation of the vacuum in the radially extending orifices, will create an air flow not only radially outwardly but, also in the direction of rotation of the shaft or nozzle. The wrapper fibres W, best seen in Figure 2, comprise approximately 5 to 20% of the fibres, and while the wrapper fibres may have some small degree of twist applied thereto, the remaining core fibres C have no twist at all, real or false. It is preferred that the wrapper fibres comprise 15% or less of the fibre mass. Control and adjustment of the amount of wrapper fibres may be achieved through adjustment of nozzle rpm, vacuum pressure and the number and size of the radially oriented orifices.
With reference to Figure 3, there is illustrated one exemplary nozzle design for use in a vacuum roving process in accordance with this invention.
The nozzle 60 has an inlet end 62 and an outlet end 64. A through passageway 66 extends through the nozzle along a longitudinal axis A from the inlet end to the outlet end. A first or entry portion 68 of the passageway includes a constant diameter bore portion 70 and a tapered portion 72 which extends between the inlet end 62 and an interior chamber portion 74. The bore 70 in the entry portion 68 in this exemplary embodiment has an inside diameter of about 9.5 mm (3/8 inch) and tapers to a remaining smooth bore outlet portion 76 which has an inside diameter of about 4.7 mm (3/16 inch) and extends between the chamber 74 and the outlet end 64.
Interior chamber 74 is created at the interface of entry portion 68 and outlet portion 76 by intersection with a plurality of, and preferably four, tapered bores 78 which extend inwardly from the circumferential surface 80 of the nozzle. Each bore tapers from a diameter of about 3.9 mm (5/32 inch) to about 3.2 mm (1/8 inch), and each bore is inclined relative to the longitudinal axis A, preferably away from the inlet end of the radially outward direction. The arrangement of the four bores 78 around the outlet portion 76 is shown more clearly in the sectional view of Figure 4.
The overall length of the nozzle is about 51 mm (2 inches) and the nozzle has an outside diameter of about 12.7 mm (1/2 inch). Toward the rearward or outlet end 64 of the nozzle, there is located a radial flange 82 which may engage a rear wall of the housing 24, while a rearward extension 84 protrudes beyond the housing for reception of a drive gear 44 or other suitable drive means, as shown in Figure 1.
It is to be understood that this invention is not limited to nozzle designs having only the above described dimensions. The dimensions may be modified as necessary depending on the roving characteristics desired.
The above described process, applicable to both long and short staple fibre roving production, is a high speed, yet simple and reliable process, the roving product of which is at least equal in quality to that produced by conventional flyer and rub roving processes.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements.

Claims

1. A process for the production of roving, the process comprising the steps of:
(a) drafting a sliver of fibres (S) to form a drafted sliver,
(b) forming the drafted sliver into a roving (R), and
(c) winding said roving (R) on a take-up reel (56);
characterized in that step (b) comprises passing the drafted sliver through a rotating nozzle (26,60) at a pressure below atmospheric pressure, to cause at least a minor portion of the fibres (W) to be wrapped about a core of remaining fibres to form said roving (R).

2. A process according to Claim 1 characterized in that step (a) comprises:
(i) feeding a sliver of fibres (S) from a sliver storage area (12) to a drafting zone (14);
(ii) drafting the sliver of fibres to a predetermined weight as the sliver passes through said drafting zone (14);
step (b) comprises:
(i) passing the drafted sliver in a linear direction into a hollow shaft (26,60) rotatable about an axis generally coincident with the said linear direction, the shaft (26,60) having a plurality of orifices (38,78) extending radially outwardly from the hollow shaft;
(ii) applying a vacuum through the orifices (38,78) sufficient to attract free ends of a minor portion of the fibres (W) into said orifices (38,78) while a major portion of the fibres remains in the hollow shaft;
(iii) rotating said shaft (26,60) as said drafted fibres pass therethrough to thereby wrap the said free ends of the minor portion of the fibres (W) about the major portion of the fibres to form a roving (R); and step (c) comprises:
winding the roving on a roving tube (56).

3. A process according to Claim 2 characterized in that said hollow shaft (26,60), upstream of the orifices (38,78), has a diameter of about 9.5 mm.

4. A process according to Claim 2 or Claim 3 characterized in that said hollow shaft (26,60), downstream of the orifices (38,78), has a diameter of about 4.7 mm.

5. A process according to Claim 2, 3 or 4 characterized in that said orifices (38,78) each comprise a tapered bore.

6. A process according to Claim 5 characterized in that said bores (38,78) taper from a diameter of about 9.5 mm to a diameter of about 4.7 mm.

7. A process according to any one of the preceding Claims characterized in that the process is carried out without applying substantially any twist to the fibres.

8. A process according to any one of Claims 1 to 7 characterized in that during step (c), the roving is wound at about 90 to 136 m/min.

9. A process according to any one of Claims 1 to 8 characterized in that the sliver has a grain weight of from about 1.49 grammes/m to about 12.96 grammes/m.

10. A process according to any one of the preceding Claims, characterized in that the minor portion of fibres (W) comprise about 5 to about 20% of the drafted sliver.

11. An apparatus for the production of roving, said apparatus comprising means (14) for drafting a sliver of fibres (S) to form a drafted sliver; and means (22) for forming said drafted sliver into a roving (R); characterized in that the roving forming means (22) comprise a rotating nozzle (26) maintained at sub-atmospheric pressure as the sliver of fibres (S) are passed therethrough, the arrangement being such that trailing free ends of the minor portion of the fibres (W) are wrapped around the core of remaining fibres to form the roving (R).