GB2119820A

GB2119820A - Process and apparatus for making yarn from roving

Info

Publication number: GB2119820A
Application number: GB08310865A
Authority: GB
Inventors: Dr Ernst Fehrer
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-07
Filing date: 1983-04-21
Publication date: 1983-11-23
Also published as: FR2526450B1; GB2119820B; CZ278681B6; IT8312501A0; CH660036A5; DE3310285C2; DE3310285A1; FR2526450A1; IT1171142B; CZ322183A3; GB8310865D0

Abstract

In a process of making a yarn from a drawn roving, fibre ends which protrude from the roving when it has been twisted are helically wound around the roving. In order to ensure a proper winding, the fiber ends protruding from the roving are wound around the latter in a sense which is opposite to the sense in which the roving is twisted.

Description

SPECIFICATION Process and apparatus for making a yarn from a drawn roving This invention relates to a process of making a yarn from a drawn roving, wherein the roving is twisted and fiber ends protruding from the roving are helically wound around the roving, and to apparatus for carrying out the process.

It is known from Austrian Patent Specification 367,104 that a yarn can be made in that a drawn roving is pulled through the generally triangular space between two suction drums, which rotate in the same sense and are provided with two mutually opposite roughening rings, which are axially spaced from that end of the drum from which the yarn is withdrawn. The roving is twisted and roughened between the two suction drums and the fiber ends which are pulled out of the roving as the latter is roughened are wound around the roving between the suction drums at an angle of lead which differs from the angle of lead of the twisted roving.As the extent to which said fiber ends are wound will depend on the slip between the roving and the suction drums by which the roving is twisted, the strength of the resulting yarn will be restricted particularly because the proportion of the fiber ends wound around the roving should be comparatively small.

It is an object of the invention so to improve a method which is of the kind described first hereinbefore that a yarn can be made which has a desired strength although the fiber ends wound around the roving constitute only a small proportion of the yarn. Besides, it should be possible to carry out the process with simple apparatus.

This object is accomplished according to the invention in that the fiber ends protruding from the roving are wound around the roving in a sense which is opposite to the sense in which the roving is twisted.

The invention is based on the recognition that in the known winding processes the fiber ends protruding from the roving are always wound around the roving in the sense in which the roving is twisted so that the tendency of the twisted roving to untwist in a false-twisting sense will cause an untwisting torque to be exerted on the fiber ends wrapped around the roving and the coherence of the roving will be reduced as well as the strength of the yarn.Because in accordance with the invention the protruding fiber ends are wound around the twisted roving in a sense which is opposite to the sense in which the roving is twisted, the torque acting in a false-twisting sense will promote the twisting of the fiber ends which are wrapped around the roving so that the coherence of the fibers will be promoted too and the resulting yarn will have a high strength and will contain a relatively small proportion of fiber ends wound around the roving.

For an effective winding of the protruding fiber ends around the roving in a sense which is opposite to the sense in which the roving is twisted, the protruding fiber ends which are carried around by the rotating roving may be deflected transversely to the axis of the roving when the same is in contact with at least one sliding surface with is engaged by the roving and the protruding fiber ends may thus be wound around the roving. Owing to the rotation iniparted to the roving as it is twisted, the fiber ends protruding from the roving are successively moved into contact with the sliding surfaces and are forced against the roving transversely to its axis.

As a result; the protruding fiber ends are necessarily wound around the roving in a sense which is opposite to the sense in which the roving is twisted. As the protruding fiber ends are moved into contact with the sliding surface, it is obviously necessary that said sliding surface has in the direction of the axis of the roving at least the length required to ensure that the protruding fiber ends spaced around the periphery of the roving will actually be deflected transversely to the axis of the roving by the sliding surface during one revolution of the roving. That minimum length will depend on the twist of the roving and on the velocity at which the yarn is withdrawn.

For a tight winding of the protruding fiber ends around the roving it is essential that the roving is in snug contact with the sliding surface because only in case of such a snug contact can the protruding fiber ends be forced against the rotating roving. To ensure a snug contact of the roving with the sliding surface, the roving may desirably be sucked to the sliding surface.

The winding of the fiber ends protruding from the roving around the latter by means of a sliding surface in contact with the roving will depend on the rotation of the roving relative to the sliding surface. To ensure that said rotation will not be resisted, the roving is desirably moved in a tensionless state. In this connection a movement of the roving in a tensionless state means that the resulting yarn is withdrawn at a velocity which is lower than or as high as the velocity at which the drawn roving is supplied because the withdrawal of the resulting yarn will necessarily involve a tension of the roving. As the roving is moved in a tensionless state, the convolutions of the fiber ends helically wound around the roving cannot be pu!led apart and the fibers of the roving cannot be forced out in a disturbing manner between the wound fiber ends.

The winding process which has been described can be carried out in a simple manner with an apparatus comprising a drawing frame, a twisting device disposed between the drawing frame and, withdrawing rollers and serving'to twist the roving, and a device which is disposed between the twisting device and the withdrawing rollers and serves to wind the protruding fiber ends around the roving. That apparatus is characterized in accordance with the invention in that the device for winding the protruding fiber ends around the roving consists of at least one sliding surface, which is engaged by the rotating roving. By that sliding surface the protruding fiber ends are deflected transversely to the axis of the roving are forced against the roving to extend in its peripheral direction so that the protruding fiber ends are helically wound around the roving as the latter is axially withdrawn.

That sliding surface may desirably be permeable to air and subjected to a vacuum adjacent to the roving so that a snug contact of the roving with the sliding surface and an effective forcing of the protruding fiber ends against the surface of the roving will be ensured.

It has already been stated that the roving must be sufficiently rotated relative to the sliding surface. For this reason the sliding surface must not substantially resist the rotation of the roving so that the sliding surface should be quite smooth.

A lower friction between the sliding surface and the roving will not adversely affect the winding of the protruding fiber ends around the roving because the protruding fiber ends are deflected as they are forced against the sliding surface so that the forces applied in a direction which is substantially transverse to the protruding fiber ends and to the sliding surface rather than in the longitudinal direction of the protruding fiber ends or in the direction in which the roving is rotated.

A movement of the sliding surface in a direction which is transverse to the roving will change the relative velocity of the roving and the sliding surface. This will influence the sliding friction between the sliding surface and the roving and the behaviour of the protruding fiber ends as they are moved into contact with the sliding surface and wound around the roving. Particularly desirable winding conditions can thus be obtained, particularly by a movement of the sliding surface in a direction which is opposite to the direction of rotation of the roving. A movement of the sliding surface in the direction in which the protruding fiber ends are wound around the roving will result in a desirable smoothening.

By a movement of the sliding surface along the roving, the relative velocity in the sliding surface and the roving can be changed in the direction of yarn withdrawal and the angle of lead of the wound fiber ends can thus be influenced.

Movements of the sliding surface with components of movement in the direction of the axis of the roving and at right angles thereto will permit an adaptation to various conditions. A sliding surface which is to be moved is desirably formed on a revolving member, preferably a solid of revolution.

The process according to the invention will be explained in more detail with reference to the drawing, in which Figure 1 is a diagrammatic transverse sectional view showing how fiber ends protruding from the roving are deflected, Figure 2 is a side elevation showing a sliding surface which is movable transversely to the roving, Figure 3 is a side elevation showing a sliding surface which is movable along the roving, Figure 4 is a side elevation showing apparatus according to the invention for carrying out the process, Figure 5 is a top plan view showing that apparatus, Figure 6 is a sectional view taken on line VI--VI in Figure 4 and Figure 7 is a sectional view taken on line VIl-VIl in Figure 4.

For winding fiber ends 2 protruding from a roving 1 around the latter, the roving is rotated and as it is rotated is moved along a sliding surface 3, as is shown in Figure 1. The fiber ends are carried around by the roving 1 as it rotates in the direction of the arrow 4 and are forced against the sliding surface 3 and wound around the roving 1 transversely to its axis so that the fiber ends are helically wound as the roving 1 is axially moved at the same time. For that winding operation it is essential that the roving 1 is in snug contact with the sliding surface so that the fiber ends 2 will be forced against and tightly wound around the roving.For that purpose the sliding surface 3 is designed to be permeable to air and a vacuum is appiied to it so that the suction flow through the sliding surface 3 causes the roving 1 to be forced against the sliding surface 3 in the direction indicated by the arrow 5. Whereas that forcing of the roving 1 against the sliding surface 3 is desired for the winding of the fiber ends 2 around the roving, it should not substantially resist the rotation of the roving because the winding of the fiber ends 2 around the roving 1 will depend on the rotation of the roving 1 relative to the sliding surface. For this reason the sliding surface 3 is rather smooth.

The winding operation can be influenced by an additional movement of the sliding surface 3 relative to the roving because that winding operation depends on the relative movement of the roving 1 and the sliding surface 3. In accordance with Figure 2 the sliding surface 3 shown as an endless belt 7, which is trained around reversing pulleys 6, is moved transversely to the axis of the roving in a direction which adjacent to the roving is opposite to the direction of the rotation of the roving so that the winding of the fiber ends 2 around the roving.1 opposite to the twist of the roving will be promoted.

In accordance with Figure 3 the endiess belt 7 which forms the sliding surface 3 is trained around reversing pulleys 6 having axes which are transverse to the axis of the roving so that the sliding surface is moved parallel to the roving 1.

The angle of lead of the helically wound fiber ends can be influenced by such a movement of the sliding surface. The engagement of the roving 1 with the belt 7 can be ensured by a vacuum duct 8.

The fiber ends 2 bearing on a sliding surface 3 cannot be deflected unless the roving 1 is rotated adjacent to the sliding surface. For this reason the twisting of the roving is of decisive importance in practice. In accordance with Figures 4 and 5 the apparatus for carrying out the process according to the invention comprises a twisting device 9, which closely succeeds a drawing frame 10 and consists of two juxtaposed, closely spaced apart suction drums 11, which rotate in the same sense Said suction drums 11 are provided with vacuum inserts 12, which constitute suction zones 13 adjoining the generally triangular space defined by the drums and produce suction streams by which the roving 1 is drawn into the triangular region so that the roving 1 will be in snug contact with the surfaces of the two drums regardless of the thickness of the roving.As a result, a proper twisting torque can be exerted on the roving by the surfaces of both drums. This twisting torque can be increased if the surfaces of the drums are rough, provided that the fine structure of the surfaces of the drum precludes a positive connection between the fibers of the roving and the surfaces of the drum so that a separation of individual fibers from the roving will be prevented.

The twisting device 9 is succeeded by a second pair of suction drums 14, which rotate in a sense that is opposite to the sense of rotation of the suction drums 11 and have smooth surfaces. The suction drums 14 are also provided with vacuum inserts 15, which define suction zones 1 6 by which the roving 1- extending through the generally triangular space is sucked into said triangular space. This will ensure a snug contact of the roving with the surfaces of both suction drums 14 so that the suction drums 14 are eminently suitable for the formation of sliding surface 3, by which the protruding fiber ends 2 can be deflected. The protruding fiber ends are deflected substantially by the surface of that suction drum 1 4 which rotates away from the generally triangular space.That suction drum which rotates into the generally triangular space will promote the winding operation which has been initiated and will smoothen-the resulting yarn. Because the surfaces of the drum14 are smooth and the sliding friction between the roving and the surfaces of the drums 14 can be only low, the rotation imparted to the roving by the twisting device 9 will be effective also adjacent to the suction drums 14, which rotate in a sense that is opposite to the sense of rotation of the roving 1 to ensure that the protruding fiber ends will be wound around the roving in a sense which is opposite to the sense in which the roving is twisted and that the roving will be in snug contact with the sliding surfaces.After the fiber ends have been wound around the roving, the resulting yarn will be torsionally balanced and can be withdrawn by means of a pair of withdrawing rollers 17. The winding of the protruding fiber ends around the roving 1 as a result of the rotation of the roving can be promoted in that the roving is moved in a tension less state during the winding operation. For this purpose the velocity at which the yarn is withdrawn by the withdrawing rollers 1 7 is lower than the velocity at which the roving is delivered by the drawing frame 10. That requirement for a movement of the roving in a tensionless state obviously does not preclude the exertion of any tension force by the withdrawing rollers 1 7 and results in an improved rotation of the roving and ensures that the convolutions of the fiber ends wound around the roving will not be pulled apart.

To ensure that the twisting device 9 is closely spaced from the suction drums 14 so that an adequate rotation of the roving adjacent to the suction drums 14 will be ensured, the vacuum inserts 1 2 and 1 5 of each pair of coaxial suction drums 11 and 14 constitute a continuous vacuum insert 18, on which the associated suction drums are rotatably mounted. These suction drums are driven by belts 1 9 and 20.

Claims

1. A process of making a yarn from a drawn roving, wherein the roving is twisted and fiber ends protruding from the roving are helically wound around the roving, characterized in that the fiber ends protruding from the roving are wound around the roving in a sense which is opposite to the sense in which the roving is twisted.

2. A process according to claim 1, characterized in that the protruding fiber ends which are carried around by the rotating roving are deflected transversely to the axis of the roving in contact with at least one sliding surface, which is engaged by the roving, and the protruding fiber ends are thus wound around the roving.

3. A process according to claim 2, characterized in that the roving is sucked to the sliding surface.

4. A process according to any of claims 1 to 3, characterized in that the roving is moved in a substantially tensionless state during the winding of the protruding fiber ends around the roving.

5. Apparatus for carrying out the process according to any of claims 1 to 4, comprising withdrawing rollers for withdrawing a yarn made from the roving and a twisting device which precedes said withdrawing rollers and is operable to twist a drawn roving, and a device which is disposed between the twisting device and the withdrawing rollers and serves to wind the protruding fiber ends around the roving, characterized in that the device for winding the protruding fiber ends around the roving consists of at least one sliding surface, which is engaged by the rotating roving.

6. Apparatus according to claim 5, characterized in that the sliding surface is permeable to air and subjected to a vacuum adjacent to the roving.

7. Apparatus according to claim 5 or 6, characterized in that the sliding surface is smooth.

8. Apparatus according to any of claims 5 to 7, characterized in that the sliding surface is movable transversely to the roving.

9. Apparatus according to claim 8, characterized in that the direction of movement of the sliding surface is opposite to the direction of rotation of the roving.

10. Apparatus according to any of claims 5 to 7, characterized in that the sliding surface is movable along the roving.

11. Apparatus according to any of claims 5 to 10, characterized in that it comprises a drawing frame for delivering said drawn roving to said twisting device.

12. A process substantially as hereinbefore described.