EP1497486B1

EP1497486B1 - Apparatus for condensing a drafted fibre sliver

Info

Publication number: EP1497486B1
Application number: EP03733008A
Authority: EP
Inventors: Barth Johannes; Heinrich Hans-Jurgen; Schwabe Bernhard; Sprod Peter
Original assignee: Lakshmi Machine Works Ltd
Current assignee: Lakshmi Machine Works Ltd
Priority date: 2002-04-19
Filing date: 2003-04-11
Publication date: 2010-01-13
Anticipated expiration: 2023-04-11
Also published as: CN1646742A; WO2003089701A3; CN1646742B; DE60330956D1; DE10217669A1; AU2003238672A1; WO2003089701A2; EP1497486A2; ATE455194T1

Abstract

Apparatus for condensing a drafted fibre sliver in a condensation area after the front roller pair on a drafting unit, where the condensation zone contains a suction element with a sliding surface with at least one suction slit essentially running in the direction of movement of the fibre sliver and a transport belt, which transports the fibre sliver over the sliding surface and which is at least air-permeable over parts of its surface, characterized by the following features: the transport belt (12), apart from the suction element (11), partially loops round a guide roller (13) placed at a distance from the suction element and flexibly arranged transversely on its axis of rotation, the guide roller (13) in the looping area and the transport belt (12) bear against a drive roller (14) and these are provided with the means to create a defined contact pressure between the guide roller (13) and the drive roller (14).

Description

The invention is concerned with apparatus for condensing a drafted fibre sliver in a condensation zone after the front roller pair on a drafting unit, where the condensation zone contains a suction element with a sliding surface with at least one suction slit essentially running in the direction of movement of the fibre sliver and a transport belt, which transports the fibre sliver over the sliding surface and is at least air-permeable over parts of its surface.
Apparatus of this kind is well-known, e.g. in file no. DE 199 03 531 A1 . The suction element has a sliding surface on the same side as the travel of the fibre sliver, cambered in the direction in which the fibre travels and is provided with a suction slit. An air-permeable transport belt is moved over this sliding surface, so transporting the fibre sliver. Beneath the suction element the transport belt loops round a transfer roller, which for its part is driven over a pair of gearwheels by a drive roller. A nipping roller presses from the top against the transport belt lying on the sliding surface to limit the condensation zone on the sliding surface. The disadvantage of this process is that the transport belt would have to have completely contradictory characteristics in order for the apparatus to function satisfactorily. On the one hand, it has to provide the highest possible degree of non-clinging qualities on the side touching the sliding surface, i.e. a low coefficient of friction. On the other hand, the same side of the transport belt has to provide the highest possible coefficient of friction and a low tendency to stick, in order to permit an adequate transfer of force through the transfer roller. If the coefficient of friction is not ideally set with the other parameters, which could be difficult to achieve, the result will either be insufficient drive movement with a high degree of slippage between the transfer roller and the transport belt, or the transport belt will move jerkily on the sliding surface as a result of too much friction. In both cases undesirable irregularities in the quality of the yarn are unavoidable. Regardless of this, a satisfactory level of power transmission can only be achieved via the transfer roller if the transport belt is kept very tight. This, however, leads to unnecessary wear on the transport belt and the sliding surface and is also detrimental to the smooth sliding movement of the transport belt on the sliding surface.
An alternative to this is well-known, in file no. DE 199 24 527 A1 . In this case the movement of the transport belt is created by friction drive created by the nipping roller limiting the condensation zone. The drive for the nipping roller is, for its part, derived from the upper roller of the front roller pair. The transport belt is subject to a high degree of wear in this embodiment. Among other things, this is due to the fact that the transport belt, which loops round the suction element under tension, has to be made to glide on the fixed suction element by the nipping roller, which requires a relatively high degree of contact pressure. Furthermore, the transport belt has to pass over a sharp corner before reaching the condensation zone equipped with the suction slit. The transport belt is therefore under a high degree of tensile stress in the condensation zone, which in the long term will lead to elongation. On the other hand, after passing over the nipping roller, the transport belt is under "thrust", so that there is a danger that excess length, which sets in with time, might extend to the condensation zone and there lead to defective support for the transport belt on the sliding surface. This, however, creates a situation where air can penetrate between the transport belt and the sliding surface laterally and can impair the condensation effect. A condensing apparatus according to the preamble of claim 1 is disclosed by DE 296 00 417 U1 .
The underlying task of the invention is therefore to create apparatus for condensing a drafted fibre sliver, where the drive system for the transport belt is guaranteed to be safe, subject to little wear and independent of the tension on the transport belt.
This task is resolved by the invention according to the distinctive part of patent claim 1. Claims 2 to 12 contain further advantageous features.
The apparatus that has been invented has the advantage over the current state of technology that the drive for the transport belt occurs independently of its tension. The transport belt can therefore be kept at a level of tension, which is ideal for the remaining functions, without any detrimental effects on the transmission of the drive torque. In particular the sliding pairing between the transport belt and the sliding surface on the suction element is not adversely affected.
The apron always sits precisely on the sliding surface as a result of the defined tension for the apron and the convex shape of the sliding surface. This means that a constant partial vacuum is achieved and air cannot penetrate the system laterally.
There is a further advantage to the invention in that no changes have to be made to the pressure arm or pendulum carrier normally found on ring spinning machines in order to apply the solution provided by this invention. The additional nipping roller required above the sliding surface is housed in a special upper roller retainer, which is supported on the axis of the front upper roller on the pressure arm. This upper roller retainer can be attached or removed in a very simple way without the need for any auxiliary assembly equipment. This means that ring spinning machines can be used both as standard machines and also as condensation machines with a minimum of effort required to retool them.
Hereinafter the invention is described in more detail using an embodiment example.
The accompanying illustrations show in

fig. 1: a side view of the invented apparatus and in
fig. 2: a suction element on the invented apparatus.

Fig. 1 shows the outlet area of a drafting unit 1, as found on ring spinning machines. Three driven bottom rollers, 2, 3 and 4 are arranged on shafts that are not illustrated, by which three upper rollers, 6, 7 and 8 housed in a pressure arm 5 are driven. The bottom roller 4 and the upper roller 8 jointly form the front pair of rollers 9 on the drafting unit 1. The drafting of the fibre sliver 10, which has been fed in, takes place in the drafting unit 1 up to this pair of front rollers 9 and this is a widely known process.
A condensation zone with a suction element 11, which will be described in greater detail later, is attached to the pair of front rollers 9. This suction element 11, as well as a guide roller 13, are both partly looped by an air-permeable transport belt 12. In the section covered by the transport belt 12, a guide roller 13 presses against a drive roller 14, which is linked to a motor drive unit, which is not illustrated. This drive roller 14 and the bottom rollers 2, 3 and 4 are preferably part of a drive shaft extending over several spinning positions or the complete machine length. The guide roller's 13 pressure on the drive roller 14 is created using a spring 15, which is attached at a retaining element 16, which is linked to the spinning machine frame. The spring 15 presses against the shaft 19, which - as is normal on spinning machines - carries the guide rollers 13 for two adjacent spinning points, and is locked in place temporarily at the retaining element 16 using a catch 20 which overlaps the retaining element's edge 17. The shaft itself 19 is not secured in a bearing, but simply rests on a catch 18 on the retaining element 16. This means that the guide roller 13 floats at right angles to the shaft 19. The spring 15, engaged between each two of the guide rollers 13, which are seated on the shaft 19, is so wide that it limits the axial mobility of the guide rollers 13.
A further spring 21 attached to the retaining element 16 presses against the transport belt 12 to provide it with the required tension.
A nipping roller 22, which is housed in the upper roller mounting 23, presses against the transport belt 12 moving over the suction element 11. This upper roller mounting 23 is once again secured in the shaft 24 of the upper roller 4 of the front roller pair 9 held in the pressure arm 5 and can be removed. A spring 25 supported on the pressure arm 5 provides the required contact pressure for the nipping roller 22 on the suction element 11.
The invention caters for a situation where the nipping roller 22 rests on the transport belt 12 with a low degree of active pressure amounting to roughly 1 to 2 daN. This means that it is possible to limit the condensation zone; the movement of the transport belt 12 on the suction element is not hindered, however. The nipping roller is also provided with a soft coating with a hardness in the 53° to 63° range on the Shore A hardness scale.
The suction element 11 consists of a hollow section, preferably a drawn steel section, which extends over several, or preferably two spinning points and is sealed off on the front side in an advantageous manner by two sealing caps 27 made of plastic. A common source of partial vacuum, which is not, however, illustrated, is assigned to all these spinning points via an extraction opening 26 on the suction element 11. The link with the partial vacuum source is created via a suction channel, which is linked to the suction element 11 by means of a detachable rubber gasket. A suction slit 28 is arranged for each fibre sliver 10 in the area covered by the transport belt 12 (sliding surface). The surface of the suction element 11 is given additional treatment, at least in the area around the sliding surface, in order to achieve a low coefficient of friction. In an embodiment made of a drawn steel section, this can take place using e.g. shot peening or by modifying the surface. If alternatively an extrusion press section made of aluminium is used, the surface is coated to guarantee both the required slide performance and the necessary hardness of the surface.
As part of the invention, the transport belt 12 has a coating with a low coefficient of friction on the side touching the sliding surface and a coating with a high coefficient of friction on the side not touching the sliding surface. When linked to the other features of this new invention, the movement of the transport belt 12 can be greatly enhanced. Disadvantages, as found on familiar apparatus of this kind, are avoided. The inner side of the transport belt 12 is not used to transmit power and can therefore be fitted with good sliding characteristics. The drive movement is fed into the transport belt 12, by pressing the guide roller 13 against the drive roller 14 by means of the perpendicular force exerted by the spring 15.
By providing the spring 15 with the correct dimensions, the normal force for the transmission of power is sufficiently large, but not too large. This feature prevents premature wear on the transport belt 12.
The apparatus in the invention is designed in such a way that all the elements, which are used to condense the fibre sliver 10, can be assembled or removed at the spinning point without any great effort. This means that it is possible to use the spinning point both in the conventional sense and also for condensation spinning. In order to create a conventional drafting unit 1, the upper roller mounting 23 with the nipping roller 22 is detached from the pressure arm 5, and the guide roller 13 is released by freeing the spring 15, so that the suction element 11, the transport belt 12 and the guide roller 13 can be simply removed from the spinning point.

Table of Reference Terms

1: drafting unit
2: lower roller
3: lower roller
4: lower roller
5: pressure arm
6: upper roller
7: upper roller
8: upper roller
9: front roller pair
10: fibre sliver
11: suction element
12.: transport belt
13: guide roller
14: drive roller
15: spring
16: retaining element
17: edge
18.: catch
19: shaft
20: catch
21: spring
22: nipping roller
23: upper roller mounting
24: shaft
25: spring
26: extraction opening
27: sealing cap
28: suction slit

Claims

Apparatus for condensing a drafted fibre sliver in a condensation area after the front roller pair on a drafting unit, where the condensation zone contains a suction element with a sliding surface with at least one suction slit essentially running in the direction of movement of the fibre sliver and a transport belt, which transports the fibre sliver over the sliding surface and which is at least air-permeable over parts of its surface, characterized by the following features:
- the transport belt (12), apart from the suction element (11), partially loops round a guide roller (13) placed at a distance from the suction element and flexibly arranged transversely on its axis of rotation,

- the guide roller (13) in the looping area and the transport belt (12) bear against a drive roller (14) and

- these are provided with the means to create a defined contact pressure between the guide roller (13) and the drive roller (14).
Apparatus according to claim 1, characterized by the fact that the guide roller (13) is routed transversely in a retaining element (16) and is pressed against the drive roller (14) by means of a spring element (15), which can be fixed in the retaining element (16).
Apparatus according to claim 2, characterized by the fact that the spring element (15) limits the mobility of the guide roller (13) in the direction of its axis.
Apparatus according to claim 1, characterized by the fact that the transport belt (12) has a coating with a low coefficient of friction on the side touching the sliding surface and a coating with a high coefficient of friction on the side not touching the sliding surface.
Apparatus according to claim 1, characterized by the fact that the suction element (11) consists of a drawn steel section.
Apparatus according to claim 5, characterized by the fact that the surface of the suction element (11), at least in the area of the sliding surface, is treated subsequently to achieve a low coefficient of friction.
Apparatus according to claim 1, characterized by the fact that the suction element (11) consists of an aluminium extrusion press section.
Apparatus according to claim 7, characterized by the fact that the surface of the suction element (11), at least in the area of the sliding surface, is treated subsequently to achieve a low coefficient of friction, a high degree of hardness and a high degree of resistance to wear.
Apparatus according to one or several of claims 1 to 8, characterized by the fact that the suction element (11) is shaped as a section, which is open on both sides and which is sealed laterally by sealing caps (27) made of plastic.
Apparatus according to one or several of claims 1 to 9, characterized by the fact that one nipping roller (22), which limits the condensation zone, rests on the transport belt (12) guided over the sliding surface with a low degree of active pressure amounting to approximately 1 to 2 daN.
Apparatus according to claim 10, characterized by the fact that the nipping roller (22) is provided with a soft coating with a degree of hardness in the 53° to 63° range on the Shore A hardness scale.
Apparatus according to claims 1 to 11, characterized by the fact that all the components related to condensing the fibre sliver (10) are arranged on the drafting unit in such a way that they can be removed, so that the drafting unit (1) can be used in a traditional manner.