US3204398A

US3204398A - False twisting method and apparatus

Info

Publication number: US3204398A
Application number: US221238A
Authority: US
Inventors: Leendert Van Assendelft
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1961-09-12
Filing date: 1962-09-04
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07
Also published as: DE1435597A1; AT240742B; ES280686A1; GB1001454A; CH434042A

Description

Sept. 7, 1965 L. VAN ASSENDELFT 3,204,398

FALSE TWISTING METHOD AND APPARATUS Filed Sept. 4, 1962 FIG. 1

FIG. 2

INVENTOR. LEENDERT VAN ASSENDELFT BY w M ATTORNEY United States Patent 3,204,398 FALSE TWISTING METHOD AND APPARATUS Leendert van Assendelft, Arnhem, Netherlands, assignor to American Enka Corporation, Enka, N.C., a corporation of Delaware Filed Sept. 4, 1962, Ser. No. 221,238 Claims priority, application Netherlands, Sept. 12, 1961, 269,191 8 Claims. (Cl. 5777.3)

This invention relates generally to a method and apparatus for false twisting running yarn and more particularly to a method and apparatus in which false twist is imparted to the yarn by causing it to be slidingly wrapped around a rapidly rotating member, said member preferably rotating around a vertical axis.

It is known that a false twist can be imparted to running yarn by causing it to be rotated along its axis using various types of false twist spindles. False twist is often applied for crimping filament yarns, the yarn being subjected to a setting treatment while in a state of high twist. Although the yarn, after passing through the false twisting device, returns to an untwisted state, it retains a tendency to crimp as a result of the setting treatment. In order that the false twisting process may be carried out economically, the apparatus used should be extremely simple and inexpensive, require little power and be easily maintained. Moreover, the apparatus should be capable of high speeds and be simple to operate.

With known methods and apparatus the obstacle which has always limited simplification and speeding up of production and reduction in cost thereof is the problem of supporting the rapidly rotating member. The member must be supported both radially and axially. From past experience, the axial bearing has always presented the greatest difficulties. In the known apparatus the axial bearing usually comprises either ball bearings, roller bearings, or gas bearings. Also constructions have been proposed in which a false twisting spindle is provided with grooves for receiving the rims of support wheels, thus holding the spindle from both radial and axial movement. All of the methods are either costly, or do not always permit the high speeds desired. Moreover, even if high speeds are attained, the apparatus wears out extremely fast.

Therefore, it is an object of this invention to provide a method and apparatus for false twisting yarn that does not have the disadvantages of the prior art methods and apparatus.

Another object of this invention is to provide a method for false twisting yarn that will permit high production speeds and is not expensive to operate.

Still another object is to provide an apparatus for false twisting yarn that is simple to operate, inexpensive to construct, capable of high speeds and subject to little wear.

A further object is to provide a false twisting apparatus that does not require the aid of conventional type bearings for axial support.

A still further object is to provide a method for axially supporting a false twisting apparatus without the aid of conventional bearings.

These and other objects will be apparent from the following detailed description.

The invention comprises axially supporting the false twisting device solely by means of the running yarn. This is accomplished by passing the yarn diagonally from the rapidly rotating member or false twisting device to a fixed coaxially positioned thread guide such that at least on the end of the rapidly rotating member that tends to move under the combined influence of its weight and the yarn tension the path of the yarn between the thread guide and rotating member runs at an oblique angle with the axis of rotation, the radial component of which is of the same magnitude as is the axial component. As a result of the yarn running in such direction and because it is wrapped around the rotating member, said member assumes a stable position of axial suspension during operation. Thus, there is no need for conventional bearings to maintain the rotating member in an axial position, the axial support being provided by the running yarn itself. This is an unusual and unexpected phenomenon.

To explain this phenomenon, the forces between the rapidly rotating member and the yarn passing around it must be considered. It was found that by the method of this invention the resultant force exerted by the yarn on the rapidly rotating member may at any time be resolved into two components. One of the components, which is resolved in axial direction, appears to always be in equilibrium with all the other forces acting in axial direction on the rotating member, such as its own weight, etc. The force component perpendicular thereto and towards the axis has a constant magnitude, with its direction rotating at the same speed in the surrounding space as the rotating member. As a result of the high speed at which this force component moves, it is substantially impossible to upset the position of radial equilibrium of the rapidly rotating member. A surprisingly, additional advantage is that this method of suspension appears to have a stabilizing effect on the yarn tension. Fluctuations, if any, in the tension of the running yarn are counteracted by small displacements of the rapidly rotating member. These small displacements are accomplished by changes in the total angle of wrap of the yarn and consequently by an increase in tension of the Wrapped yarn.

The false twisting device used in carrying out the method of this invention comprises a rotatable member that can move in longitudinal direction, near at least one end of which a fixed thread guide is coaxially positioned. The first and last contact points on the wrapping surface of the rotatable member are positioned much farther from the axis of rotation than is the inner surface of the thread guide. By thus positioing the wrapping surface relative to the thread guide, the yarn is caused to travel to said guide along the desired path forming an oblique angle with the axis of rotation.

Obviously, a fixed thread guide may be provided near both ends of the rotatable member. It has been found that this is not always necessary, particularly if the apparatus is provided with a known type of radial bearing. However, if it is also possible for the rotatable member to move transversely the requirements are somewhat different. Generally, in such case it is not possible to use a conventional type mechanical drive system. With an embodiment of this type the rotatable member is formed by the short circuit armature of an electric motor. The armature is actuated without being in mechanical contact with any driving means. In this case, the rotatable member is supported axially by the wrapped yarn. Displacement of the armature transverse to the axis of rotation and out of the position of equilibrium results in a change in the path of the yarn, as a result of which the armature is returned to its position of equilibrium. It has been found that this type of false twisting device is far less sensitive with regard to correct balancing of the rotatable member than is any other known false twisting device. Apparently, this is because the rotatable member will always tend to rotate about a main axis regardless of its shape.

A preferred embodiment of the short circuit armature is obtained if it is shaped like a ring. The path of the yarn between the two thread guides is chosen so that at one point the yarn is wrapped around the ring one or more times.

The false twisting device may also advantageously be constructed so that the rotatable member is supported radially with the aid of known means. With this embodiment, a fixed thread guide is necessarily only near one end of the rotatable member which under certain circumstances simplifies threading the yarn. The apparatus, if provided with a known radial bearing, can then be placed in a position other than that in which the axis of rotation is vertical. For instance, if the axis of rotation is horizontal, the weight of the rotatable member is entirely supported by the radial bearing, so that no radial displacement takes place. 1

The embodiments of the apparatus may be mounted on most knovm types of false twisting devices without requiring drastic modification. In one embodiment the drive system comprises at least one blow pipe :and the rotatable member is provided with blades. The apparatus is driven with the aid of compressed air or some other gas under pressure. Such an embodiment may be used in combination with radial gas bearings.

In a much simpler construction the rotatable member comprises a tubular spindle, the axis of which coincides with the axis of rotation, the spindle being supported radially by freely rotatable supporting discs. In this case, it is advantageous to drive the spindle mechanically instead of by compressed air. F or example, there are two pairs of supporting discs, each pair of which forms a wedge-shaped space, the tubular spindle being kept in these wedge-shaped spaces by a driving belt which runs in contact with said spindle.

The tubular spindle is provided at one end with a wrapping surface. Thus, attached to said tube may be one or more radially directed arms having thread guides at their end-s. With this apparatus, the yarn is successively passed through the tube, along an arm, through a thread guide, and then through the coaxially positioned fixed thread guide. A very suitable device for accurate mass production comprises a tubular spindle having an expanded end provided with a number of symmetrically positioned passages. The yarn is threaded into the tube, passed one or more times through the passages, thus being wrapped around the edge of the expanded end and then fed to the fixed thread guide.

For purposes of illustration and not by way of limitation, the invention will now be described with reference to the accompanying drawings, wherein- -FIGURE 1 is a view in vertical section showing a false twisting spindle which is supported'by the yarn axially.

FIGURE 2 is a side view partly in section of another rapid rotary motion and is held in suspension above the plate-shaped thread guide 6.

The function of grooves 4 is twofold. First, they ensure that the yarn 1 is taken along by the ring so that it does not roll over the surface of the ring, thus preventing loss of twist. 'Second, they serve to prevent the yarn from being damaged while the ring 3 is starting up and still in contact with the plate 6. The tensional forces in the yarn keep the ring 3 in equilibrium vertically. It has been found that this state of suspension equilibrium can be retained even if the false twisting device is placed in a somewhat inclined position.

Referring now to FIGURES 2 and 3, there is shown respectively a side view, partly in section, and a plan view of a different embodiment of the false twist device of the invention. The numeral 7 refers to a tubular false twist spindle, .a large part of the outer surface of which is cylindrical. The spindle is flared at its lower end. In the flared end 8 there are four passages 9 symmetrically arranged. Near the lower end of the spindle 7 and coaxial therewith there is a fixed thread guide 10. Yarn 1 is successively passed through the tubular spindle 7, through one of the passages 9, and through the thread .guide 10. The yarn supply and discharge systems (not shown) are identical with those of the false twisting device shown in FIGURE 1. Alternatively, yarn 1 may be passed through several of the passages 9 before being led to the thread guide 10.

The false twist spindle 7 is set in rotary motion by belt '11 moving in contact with the spindle at a very small angle, as a result of which the spindle is held from radial movement. The radial bearing comprises four supporting wheels, only three of which are shown, '12, 13 and 16, coupled in pairs, each pair forming a single freely rotatable system. The supporting

wheels

12 and 13 are coaxially coupled by bushing 14. The bushing 14 is supported by a holder 15 such that it is freely rotatable. Similarly, supporting wheel 16 is coaxially coupled with another supporting wheel (not shown) by means of a bushing -(not shown), said bushing being supported in the same manner as bushing 14. The two systems together form the wedge-shaped spaces between the supporting wheels, in which the spindle 7 fits. In these wedge-shaped spaces the spindle 7 is pressed against the supporting wheels by the belt 11.

In FIGURE 2 are designated three yarn points A, B, and C. At point A the yarn first comes into contact with the spindle. At point B the yarn runs in vertical direction before leaving the spindle, and at point C the yarn leaves the spindle surface. Since the supporting wheels and the belt '11 can only exert forces on the spindle which are directed transverse to the axis of rotation thereof, the

tensional forces in the yarn, at the points of first and last contact with the spindle, are the only external forces grammatically. The magnets are positioned so that within the circle encompassed by them a rapidly rotating electromagnetic field is maintained. Inside the circle there is a metal ring 3. As a result of the eddy currents induced in this ring by the rotating magnetic field a torsional moment is exerted on the ring. At diametrically opposite points two radially directed grooves 4 are provided on the lower side of the ring 3.

Coaxial with the circle of coils 2 and on each side thereof are positioned thread guides 5 and 6, the latter forming the bottom of a cylinder with the coils 2 forming the side. Ring 3 lies on guide 6 while in a state of rest. The y-arn 1 passes through the thread guide 5, wrapped at least once around the ring 3 in one of grooves 4 and subsequently discharged through the thread guide 6. When the yarn is moved .by supply and discharge mechanisms (not shown) and the coils 2 excited, the ring 3 is set in which can counter-balance the weight of the spindle. This is in contrast with known false twisting devices in which the yarns runs substantially parallel to or along the axis of rotation of the spindle.

FIGURE 4 diagrammatically shows the tensional forces acting in the yarn 1 at the points A and C. The tensional force at A is indicated by P and at B by P The path of the yarn leaving the spindle at point C makes an angle at with the axis of the spindle. Therefore, the tensional force at point C has a magnitude of P .e where f is the coefiicient of friction of the yarn over the spindle, and e the base of the natural logarithm. The force P .e can be resolved into an axial componentand a radial component'directed towards the spindle axis, the components having a magnitude of P .e .cos 0c, and P .e .sin 0c, respectively. If the weight of the spindle is G, then the following relation holds for the vertical equilibrium thereof:

When the yarn runs practically parallel to or along the axis of the spindle, as in the known false twisting apparatus, the angle a. is and the above-mentioned equation consequently becomes:

Since P is always greater than P it is obvious that the known apparatus cannot operate without an axial bearing since the latter equation cannot be satisfied. However, it should be added that with known false twisting apparatus, the yarn can run upward in which case the yarn tensions can be adjusted so that the equation P -P +G:0 is satisfied. Nevertheless, even in this case axial support is necessary since the apparatus is not very stable.

In the false twisting device of this invention, the spindle is practically always in axial equilibrium since the function e .cos a. decreases continuously as on increases from 1 to 180 and becomes 0 when o :90. Thus, the abovementioned mathematical relation is satisfied.

The apparatus of FIGURES 2 and 3 may also be advantageously used in a position in which the axis of spindle rotation is horizontal. When the spindle is in this position, the following relation holds for the axial equilibrium:

For the yarn (shown in FIGURE 2) passing through the apparatus this relation may always be satisfied, irrespective of the values of P and P The mathematical relations describing the equilibrium of forces also show that this equilibrium is stable. This accounts for the spindle automatically taking up its proper position at the beginning of the process.

It should be added that, in addition to the aforementioned axial forces, a torsional moment, and a transverse force having a magnitude of P .e ".sin or act on the spindle. However, said torsional moment and force change direction twice every revolution. Owing to the high speeds of the spindle, i.e. up to 200,000 revolutions per minute, said moment and said transverse force cannot upset the position of spindle equilibrium.

The setting treatment of the yarn, if it is to be crimped by the false twisting process, consists of softening and subsequently hardening the yarn in a known manner while it is in a state of high twist. With yarn made from a thermoplastic material, the setting process may consist of successive heating and cooling of the yarn.

While the invention has been illustrated by the foregoing specific examples, it will be apparent to those skilled in the art that it may be used with many different types of false twist devices and other twisting apparatus and that numerous modifications, variations and embodiments within the scope of the invention are possible. Therefore, the invention is intended to be limited only as set forth in the following claims.

What is claimed is:

1. A twisting device comprising a rotatable member capable of axial displacement provided with at least one yarn wrapping means, means for driving said member, and a thread guide means coaxially positioned adjacent one end of said member, said yarn wrapping means disposed farther outside the axis of rotation of said member than the thread guide means whereby the path of yarn passing from said rotatable member to said fixed thread guide runs at an oblique angle with the axis of rotation of said member to support said rotatable member in the axial direction solely by means of the yarn.

2. A false twisting device comprising a rotatable tubular spindle flared at one end, means for driving said spindle, passage means in said flared portion of said spindle for slidably wrapping yarn therethrough, and a fixed coaxially positioned thread guide means adjacent said flared portion whereby the yarn path from said passage means in said flared portion to said thread guide means forms an oblique angle with the axis of rotation of said spindle to support said spindle during rapid rotation solely by means of the running yarn.

3. The false twisting device of claim 2 in which the spindle is radially supported by means of two pairs of supporting discs, said spindle held in position against said discs by means of a driving belt.

4. The false twisting device of claim 2 in which the wrapping means comprises a plurality of symmetrically positioned passages.

5. A false twisting device comprising a rotatable tubular member flared at one end and adapted for the passage of yarn longitudinally through its center, rotatable elements to support said member against radial displacement, drive means to impart rotation to said member and for urging it into contact with said rotatable elements, yarn passage means in the outer periphery of said flared portion of said member, and a thread guide means positioned coaxially with said member and adjacent the flared portion whereby the yarn after it passes through said member and said passage means runs at an oblique angle with the axis of rotation of the member to support said member during rapid rotation solely by means of the running yarn.

6. The false twisting device of claim 5 in which the rotatable member is supported radially by at least two pairs of discs rotatable about spaced axes, the discs of each pair overlapping to form a throat for receiving said tubular member and in which said drive means comprises an endless drive belt.

7. In a method of axially supporting a rotatable fluted tube, the fluted end portion of the tube having perforations in the wall thereof, the steps of (a) passing a thread into the tube and along the rotational axis, thereof,

(b) directing the thread radially outward through one of said perforations to slidably engage the outer rim of said fluted portion; and

(c) passing the thread from said rim through a thread guide positioned adjacent said fluted end portion and located on the axis of rotation of the tube whereby an oblique angle is created by the thread path and the axis of rotation.

8. A method of axially supporting a rotatable yarn twisting member solely by means of the yarn being twisted thereby, which comprises the steps of (a) passing a yarn along the axis of rotation of said member,

(b) displacing the yarn radially from said axis to a yarn gripping position located on said member, and

(c) passing the yarn from said gripping position to a coaxially positioned thread guide whereby an oblique angle is created by the yarn between the yarn path thus created and the axis of rotation.

References Cited by the Examiner UNITED STATES PATENTS 3,035,399 5/62 Scragg 5777.3

FOREIGN PATENTS 1,190,688 10/59 France.

775,075 5/57 Great Britain. 775,076 5/ 57 Great Britain. 786,580 11/57 Great Britain. 807,529 1/ 59 Great Britain. 815,650 7/ 59 Great Britain.

MERVIN STEIN, Primary Examiner.