Friction False-Twisting Unit

The present invention relates to a friction false-twisting unit which is used for friction texturing endless filaments, particularly manufactured filament material used as yarn. Yarn is drawn past a plurality of partially interleaved, overlapping, rotating friction discs, and the friction of the yarn against the discs imparts a false twist to the yarn as it is drawn past the discs. The discs are supported on a plurality of shafts arranged so that the discs overlap at one edge portion or area. For example, three such shafts are provided, preferably arranged in an equilateral triangular array. The invention is particularly concerned with damping the oscillations of the false-twisting unit and with maintaining the desired orientation of the unit whose oscillations are being damped.

A friction false-twisting unit is known from German Patent application DE-OS No. 29 36 845 in which bearings for the shafts, arranged in the support plate, are mounted with little radial oscillation by interposed rubber rings. In this way, absolutely quiet operation is assured, even upon high speeds of shaft rotation.

However, there are disadvantages. While the disturbances, which come, for instance, from the filaments or threads to be false-twisted or from the tangential drive belt for the shafts, are damped, nevertheless the relative axial positions of and the parallel relationship between the three shafts change for a short time, and this leads to yarn defects. Furthermore, close tolerances cannot be obtained between three shafts which are damped by rubber rings. Further still, the force of application of the tangential drive belt presses the individually driven, damped mount away to one side. This changes the geometry of the unit and thus also the quality of the yarn.

The object of the invention is to eliminate the above drawbacks and to improve a friction false-twisting unit so that damping of oscillation of the entire unit and the installation is effected simply without yarn quality being impaired.

This problem is solved in accordance with the invention. The friction false-twisting unit is fastened to the supporting machine bed through damping elements interposed between the unit and the machine bed. These damping elements are elastomeric, and may be comprised of rubber or plastic. They are preferably electrically conductive to conduct away electrostatic charge generated by the discs spinning in contact with the filaments.

The friction false-twisting unit including its shafts are supported on a base plate. The damping elements are interposed between the machine bed and the base plate. For this purpose, there is a holding mandrel on the base plate. There is a guide sleeve into which the mandrel is inserted. There is a mount fastened to the machine bed. The guide sleeve rests in the mount via the damping elements.

Typically, the shafts of the false-twisting unit are all located to one side of the holding mandrel. The shafts and the base plate apply weight on the holding mandrel and they tend to urge the mandrel which, in turn, urges the guide sleeve, to pivot or twist. The damping elements resist such pivoting or twisting motion and maintain the orientation of the base plate and the shafts thereon. With the base plate and its shafts removed from the holding mandrel, the guide sleeve is normally inclined at an angle from its orientation when the base plate is in place, and the damping elements assure that the guide sleeve has this inclined orientation. One of the shafts is driven by a tangential belt which runs along a drive whorl on that shaft. The tangential belt has a substantial width dimension and at the line of contact between the drive whorl and the belt, the tangential belt should be in the plane of the drive whorl. The damping elements assure that with the base plate and shafts in place and operating, the side of the drive whorl in contact with the tangential belt is in the plane of the tangential belt where it contacts the drive whorl.

Interposing damping elements between the false-twisting unit and the machine bed solves the problem. It has the further advantage that the unit can be placed with initial tension against the tangential drive belt without additional tensioning means being required for this.

The use of damping elements of elastomeric material affords the further possibility of obtaining different damping properties by simple means in the different directions of force since such elastomeric materials respond differently to sheer and/or compressive and/or tensile oscillations.

The invention is explained below in further detail with reference to an illustrative embodiment.

FIG. 1 is a side elevational view of a friction false-twisting unit according to the invention;

FIG. 2 is a section through the mount, without the friction false twisting unit; and

FIG. 3 is a top view of the mount, without the friction unit.

Referring to FIG. 1, the friciton false twisting unit has a base plate 1. Three vertically uptanding shafts 2 are rotatably mounted in the base plate. (The third shaft is hidden behind the shaft at the right, as can be seen by the discs 3 on all of the shafts.) The shafts 2 are arranged in an array of an equilateral triangle. The shafts pass through the base plate. Above the base plate 1, each shaft carries a series of spaced apart friction disks 3. The disks are sized so the disks on the adjacent shafts are interleaved or overlapped at the disk edge portions where they meet.

Beneath the base plate and spaced away from the shafts 2, there is a holding mandrel 4 which, for instance, is a square cross-section. The mandrel is inserted into a guide bushing 5, which has a correspondingly shaped bore. The guide bushing 5 rests via a cross arm 5a on the damping elements 6 and the damping elements are arranged between the unit and a mount 8 that is connected with the machine bed 7.

The unit is driven from a tangential belt 9 via the drive whorl 10. The other two shafts 2 are placed in rotation by a toothed belt 11 which surrounds all three shafts. The drive whorl 10 may lie in front of or behind the tangential belt 9 so that the direction of rotation of the disks can be selected, for producing S or Z twist to the yarn.

As can be noted from FIG. 2, when the false twisting unit is not in place, the guide bushing 5 is arranged inclined by the angle .alpha. to the spindle rail 7 of the machine bed and to the plane of the tangential belt 9, which extends parallel to the rail. The angle .alpha. corresponds to the elastic deformation of the damping elements 6 which is to be expected when the bushing 5 is loaded by the weight of the unit. After the false-twisting unit has been put in place, the axis of the drive whorl is again parallel to the plane of the tangential belt. In this way, the oblique orientation of the unit, which occurs due to the eccentrically acting force of the weight of the unit and to the elastic elements is again compensated for. The angle .alpha. is preferably about or slightly greater than 20', i.e. a fraction of 1.degree..

FIG. 3 shows how the oblique orientation of the guide bushing is obtained. The cross arms which are fastened above and below the mount 8 respectively are shifted somewhat with respect to each other, whereby the damping elements 6 are also held fast. In this way, it is possible to bring the drive whorl 10 against the tangential belt 9 with a certain initial tension, so that no special tensioning devices are needed for pressing the tangential belt against the drive whorl.

The damping elements 6 may, for instance, be known rubber-metal bushings or intermediate plates made of plastic. In order to lead away the electrostatic charge which occurs in operation, the damping elements are made electrically conductive.

Although the present invention has been described in connection with a preferred embodiment thereof, many variations and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.