GB2182069A

GB2182069A - Draw-off nozzle for roving and spinning frames

Info

Publication number: GB2182069A
Application number: GB08620974A
Authority: GB
Inventors: Bernhard Schwabe
Original assignee: Kombinat Textima VEB
Current assignee: Kombinat Textima VEB
Priority date: 1985-08-29
Filing date: 1986-08-29
Publication date: 1987-05-07
Also published as: FR2586594A1; CS570186A1; DD255054A3; DE3619356A1; GB8620974D0

Abstract

The invention relates to a draw-off nozzle for roving and spinning frames and can be used on ring and open-end rotor spinning machines for rotating threads in fixed thread guides or with rotating thread guides on flyer heads. The nozzle comprises a body (2) with an insert eg a spiral wire insert (1), fitted thereto having a thread bearing surface which is generally arcuate. The wire insert (1) is secured in the upper and lower parts of the nozzle body by means of a shoulder (4) and an annular rim (3). <IMAGE>

Description

SPECIFICATION Draw-off nozzle for roving and spinning frames This invention mlates to a draw-off nozzle for use in the flying head of flyers, as a thread guide on ring spinning machines and as a yarn draw-off nozzle in open-end rotor spinning machines.

In some cases, in roving or yarn production, either the thread rotates about a fixed deflection point or the thread guide rotates relative to a fixed thread movement path. It is thereby possible for the thread to roll on the surface of the thread guide, also called a draw-off nozzle or a draw-off funnel. This rolling results in the generation of false or unwanted twists in the region in front of the thread guide relative to the direction of transport of the thread.

As a result of the thread pulling force which occurs, the thread in contact with the surface of the thread guide experiences a flattening effect which impedes its rolling capacity. This prevents both the propagation of the twist between its place of origin and the rotating thread portion and the generation of false or unwanted twist in this region with the result that thread breaks occur.

One known device has axial and radial spiral projections but the thread has to make relatively abrupt changes in direction so the thread or yarn is bent sharply and its rolling and twist propagation are considerably impeded. Moreover, the annular projections provide a further obstruction to the radial propagation of the twist up to the collecting groove and this can be detrimental.

The production of the draw-off nozzle as a casting or pressed article presents difficulties since there is no freedom of undercut.

Another known device eliminates the twist threshold for the radial propagation of the yard twists but it nevertheless still fails to provide a continuous and smooth transition from the axial part of the draw-off nozzle to the radial part with a sufficiently gradual curvature. In another design based on a false twist spiral used for carded-yarn ring spinning machines, a bend of the thread at the annular edge of the basic nozzle body occurs as a result of the lack of radial transition so the twist propagation is impeded.

The aim of the invention is to provide a draw-off nozzle which will increase productivity in the production of rovings and yarns, especially open-end rotor yarns. The yarns will make it possible to achieve a softer feel in the sheet-like textile structure and thread breaks will be reduced. Furthermore, the manufacture of the draw-off nozzles is to be made less expensive.

It is an objective of the invention to provide a draw-off nozzle with an insert for roving and spinning frames, which makes it possible to obtain a continuous and gradual transition of the direction of travel of the roving or yarn while it is being transported and twisted. At high rotor speeds and where temperature-sensitive fibre materials are concerned, it will be possible to eliminate the heat effectively. Furthermore, it must be possible to change the insert quickly and easily, without interfering with the basic nozzle body.

According to the invention, there is provided a draw-off nozzle for roving and spinning frames, comprising a body with an insert fitted thereto, said insert having a bearing surface for thread or yarn drawn from the nozzle which is arcuate or curved so as to provide a gradual smooth transition for the yarn or thread from its axial travel into its radial travel with respect to the body, the body having a shoulder at its lower end and an annular rim at its upper end to receive and retain the insert in the body.

The shoulder at the lower end of the nozzle body serves to secure the insert axially whereas the annular rim at the upper end of the nozzle body serves to secure the insert both radially and axially.

The bearing surface for the insert, which preferably is of wire and of a spiral design, is made in the form of a circular arc or is curved in a similar way to provide a gradual smooth transition for the yarn or thread from its axial travel into its radial travel with respect to the nozzle body.

The pitch of the spiral wire can be selected according to the twist count and the yarn draw-off speed. Since the twist transport direction and the thread drawing-off direction are opposite to one another for the abovementioned fields of use, the wire pitch in the axial part of the wire insert must be at least somewhat greater than the pitch of the yarn twists in order to use the device effectively.

Where the thread transport and twist transport are in the same direction, this condition does not have to be satisified.

Because the piece of yarn is positioned freely between two wire turns, dirt particles in the fibre materials and points of adhesion do not impede the rolling capacity. Also a constant rolling speed is obtained so thread breaks are avoided. This makes it possible to ensure the effective processing of fibre materials with increased impurities and defects.

By means of the nozzle of the invention, a continuous and gradual change in the direction of travel of the thread from an axial to a radial movement is achieved, and twist propagation is assisted. Even at high rotor speeds, the gentle and smooth change in direction ensures low yarn draw-off forces, the continuous movement of the take-off point in the rotor groove and a constant size of the twist tie-in zone.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross section through a drawoff nozzle of the invention, and Figure 2 shows a detail of the body of the nozzle of Figure 1.

Referring to Figure 1, there is shown a draw-off nozzle for an open-end rotor spinning machine which is characterised by a wire insert 1 fitted to its basic body 2. The wire insert 1 rests firmly on the surface of the basic body 2 and is attached mechanically at the upper end of the axial portion by means of an annular rim 3 (Figure 2) and at the lower end by means of a radial shoulder 4.

The curve of the thread bearing surface of the wire insert 1 corresponds generally to the shape of the opening in the body 2 on which it is fitted and is designed as a circular arc but some other curve form can also be used.

The pitch of the wire can be constant or variable. However, a greater pitch in the axial portion is beneficial, so that sufficient twists can be grasped between two wire turns and transported into the radial portion. However, the pitched selected should not be too large otherwise a roughening of the yarn occurs.

The wire diameter must also be selected with this in mind.

Since the thread movement takes place predominantly in the peripheral direction, the thread pulling force is insignificantly increased by the wire 1. The wire is preferably circular but other profiles enabling twist transport can be used. The wire 1 only results in a very slight frictional resistance to the thread in its longitudinal direction and is appropriately produced from wear-resistant unalloyed or alloyed spring-steel.

The pitch direction of the wire corresponds to the pitch direction of the fihres in the yarn.

Where very large pitches are concerned, a multiple spiral can be used to reduce surface pressure. The number of bearing points of the thread is increased in this way. As the thread does not come into contact with the basic body 2, so the latter does not undergo any wear. When there is a substantial variation in the technological parameters of the spinning process or in the event of wear of the wire, the wire insert 1 can easily be changed. The reliability of the piecing operation on open-end rotor spinning machines is increased substantially as a result of the wire insert 1.

The wire insert guarantees a continuous and gradual change in direction of the path of travel of the thread from its initially vertical or axial movement with respect to the nozzle body through to its radial movement with respect to the nozzle body and therehy achieves a uniform generation of false twists of the necessary size.

Claims

1. A draw-off nozzle for roving and spinning frames, comprising a body with an insert fitted thereto, said insert having a bearing surface for thread or yarn drawn from the nozzle which is arcuate or curved so as to provide a gradual smooth transition for the yarn or thread from its axial travel into its radial travel with respect to the body, the body having a shoulder at its lower end and an annular rim at its upper end to receive and retain the insert in the body.

2. A draw-off nozzle according to claim 1, wherein the insert is a spiral wire insert whose pitch and wire diameter are variable as a function of the thread fineness and thread twist count.

3. A draw-off nozzle according to claim 2, wherein the wire of the spiral wire insert is made circular or with another profile necessary for twist transport.

4. A draw-off nozzle according to claims 2 or 3, wherein the spiral wire insert is made single-flight or multiple-flight.

5. A draw-off nozzle for roving and spinning frames comprising a body having a shoulder at one end and an annular rim at the other end to receive and locate an insert therein to guide a thread or yarn as it travels through the nozzle.

6. A draw-off nozzle substantially as herein described with reference to the accompanying drawings.