Holding device for a twin pressure roller of a drafting unit

Abstract

A holding device for a twin pressure roller of a drafting unit includes a number of bottom rollers. The twin pressure roller includes a stationary axle and two rotatably supported upper rollers. The holding device includes at least one positioning element assigned to the axle of the twin pressure roller and at least one force transmission element, wherein the positioning element is arranged in the area of the center of the axle of the twin pressure roller and thus permits the twin pressure roller to move in a pendulum fashion around the center. The holding device, together with the twin pressure roller may be lifted from the bottom roller. At least one catch bearing for approximate positioning during placement on the bottom rollers is assigned to the twin pressure roller. It may further be provided that the force transmission element is arranged separately from the positioning element and that the catch bearing is integrated into the force transmission element.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of German Application No. 10 2005 027 194.4, filed Jun. 6, 2005, the disclosure of which is expressly incorporated by reference herein.

The present invention relates to a holding device for a twin pressure roller of a drafting unit comprising a number of bottom rollers, the twin pressure roller comprising a stationary axle and two rotatably supported upper rollers, the holding device comprising at least one positioning element assigned to the axle of the twin pressure roller and at least one force transmission element, whereby the positioning element is arranged in the area of the center of the axle of the twin pressure roller and thus permits the twin pressure roller to move in pendulum fashion around the center and whereby the holding device, together with the twin pressure roller, can be lifted from the bottom roller.

A holding device of the above mentioned type is prior art in German published patent application 38 23 872. In the case of the known holding device, the twin pressure roller is held in the center of its axle by use of a positioning element and positioned in relation to the respective bottom roller. The positioning element is adjustable in fiber transport direction and permits the adjustment of a so-called recess or overhang of the upper rollers. The rotational axis of the upper rollers in relation to the fiber transport direction are arranged to the rotational axis of the bottom rollers either somewhat forwards or backwards out-of-line. The axle of the twin pressure roller is taken up in the positioning element in such a way that moving in pendulum fashion around the center is permitted. Because of this permitted moving in pendulum fashion in connection with an overhang or recess, the twin pressure roller is aligned parallel to the bottom roller when pressed thereon.

An exact parallelism of the twin pressure roller to the bottom rollers is important in order that an even drafting of the fiber strand can take place. When an upper roller is not aligned parallel to its respective bottom roller, then the nipping of the fiber strand over the width of the roller is different and thus the fiber strand will be drafted unevenly.

The force transmission of a pressing force for the loading of the upper rollers takes place integrated in the positioning element in the center of the axle of the twin pressure roller.

The known holding device has proved itself well in practice in drafting units having a relatively small gauge, for example, in the case of drafting units for ring spinning machines. After the twin pressure roller is raised from the bottom rollers, which action may, for example, be necessary for the purposes of eliminating a fault, the upper rollers, when replaced on the bottom rollers, automatically find their position in the set overhang or recess, and the twin pressure roller, due to the permitted movement in pendulum fashion, aligns itself again exactly to the bottom roller. The holding device with the positioning element does not need to be aligned parallel to the bottom rollers. This a crucial advantage, as for the purposes of fixing and loading the holding device by the use of the pressure force, usually a large number of components are applied, in the case of which, because of the addition of individual tolerances, good parallelism of the positioning element with the bottom rollers cannot be guaranteed.

In the case of an increased gauge of over 100 mm it can however easily occur that even a small oscillation angle will result in such a large misalignment of one upper roller of the twin pressure roller to the other upper roller that one upper roller is placed with an overhang, while the other upper roller of the twin pressure roller is placed with a recess to the bottom roller. In particular, in the case of drafting units for air spinning machines, which have a large gauge of 200 mm and over, these known holding devices are no longer reliable in their application. When the twin pressure roller is replaced after being raised, the upper rollers do not find their set position, as the oscillation angle cannot be limited by the positioning element to such an extent that placing one upper roller with a overhang and the other roller with a recess can be prevented in the long run.

A drafting unit with a large gauge is known in German published patent application 39 07 745, in which the twin pressure roller is positioned and loaded by way of two holding devices in close proximity to both upper rollers. In the case of this configuration, a false positioning of the upper rollers onto the bottom rollers is prevented; however, a movement in pendulum fashion of the twin pressure roller is not possible, so that the twin pressure roller cannot align itself parallel to the bottom roller. Rather, both holding devices must be absolutely exactly aligned to the bottom roller, so that both upper rollers of the twin pressure roller are also in the correct position. This cannot be always ensured, despite complicated adjustment work.

It is an object of the present invention to improve the known holding device and to permit movement in a pendulum fashion of the twin pressure roller also in the case of drafting units with a large gauge, without permitting a false positioning of the upper rollers when the twin pressure roller is replaced on the bottom roller.

This object has been achieved in accordance with the present invention in that at least one catch bearing is assigned to the twin pressure roller for approximate positioning of the twin pressure roller when placed onto the bottom rollers.

By providing at least one catch bearing, the capacity of the twin pressure roller to move in pendulum fashion may be adjusted in the long run in such a way, that when the twin pressure roller is placed on the bottom rollers, a false positioning of both upper rollers is excluded and that despite this, when the pressure force is applied, a parallel alignment of the twin pressure roller to the bottom rollers can take place. The catch bearings act thereby at least shortly before the replacing of the twin pressure roller and secure advantageously an approximate parallel alignment of the twin pressure roller to such an extent that the upper rollers of the twin pressure roller, depending on the chosen adjustment, are either both placed on the bottom rollers with an overhang or both with a recess. The capacity to move in pendulum fashion provided within the approximate parallel alignment permits the twin pressure roller, when the pressure force is applied, to align itself exactly parallel to the bottom rollers. Placement of one upper roller with overhang and the other upper roller with recess is thus effectively prevented.

The catch bearing may be designed in different ways. Advantageously, it acts from the center of the axle at the greatest possible distances on the twin pressure roller. The further the catch bearing is arranged from the center of the axle of the twin pressure roller, which represents the fulcrum in the pendulum movement, the easier the rather contradictory functions of the catch bearing are reliably realized. On the one hand, the catch bearing should limit the oscillation movement of the twin pressure roller to such an extent that a false positioning of the upper rollers is prevented, on the other hand, however, there must be sufficiently large oscillation capacity, so that an exact parallel alignment under the action of the pressure force is permitted. The catch bearing is therefore designed in such a way that it guides the twin pressure roller to the point of placement on the bottom rollers, but then does not hinder the twin pressure roller in their oscillating alignment parallel to the bottom rollers.

The catch bearing may be assigned to an upper roller of the twin pressure roller, it acts, however, particularly advantageously on the axle of the twin pressure roller, as this does not begin to rotate when the twin pressure roller is placed on the bottom roller. In an advantageous embodiment of the present invention, it is provided when two catch bearings are arranged at a distance to one another in close proximity to the upper rollers. A symmetrical embodiment of the components, especially of the holding device, is thus permitted in a simple way. It is further advantageous when the force transmission element, which transmits the pressure force for the upper rollers to the axle of the twin pressure roller, is integrated in the positioning element. The force transmission thus takes place together with the positioning in the center of the axle of the twin pressure roller, and the force is distributed evenly on both upper rollers.

Depending on the required pressing force in ratio to the chosen diameter of the axle of the twin pressure roller, a very high bowing of the axle under load can occur if the force transmission element is arranged in the center of the axle. This bowing under load results in a slanting of the two upper rollers and a deviation from the parallel position. In order to avoid too great a deflection of the axle it is advantageous to arrange the force transmission element separately from the positioning element. Particularly advantageous is the configuration of at least two force transmission elements each in close proximity to the upper rollers. It must be heeded, however, that no coerced positioning due to the force transmission elements takes place which would hinder the oscillating alignment of the twin pressure roller.

In the case of the force transmission element separated from the positioning element, it can be advantageous to integrate the catch bearing in the force transmission element, in order to permit both to act in close proximity to the upper rollers on the axle of the twin pressure roller.

The catch bearing advantageously has a fork-like design and prevents the twin pressure roller from advancing too far out of its position when it is raised from the bottom roller.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings wherein:

FIG. 1 shows a partly intersectional side view of a partly shown drafting unit including holding devices for twin pressure roller;

FIG. 2 shows a view of a holding device for a twin pressure roller along the intersectional surface II-II of FIG. 1; and

FIG. 3 shows a view of a holding device for a twin pressure roller along the intersectional surface III-III of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

The drafting unit 1 partly shown in FIG. 1 includes a number of roller pairs 2, 3 and 4, 5, which transport a fiber strand 6 in fiber transport direction A through the drafting unit 1 and draft it to the desired degree of fineness. Guiding belts 7, 8 are assigned in the known way to the roller pair 4, 5. It can be provided that the drafting unit 1 includes further roller pairs, arranged upstream of the roller pair 4, 5 or downstream of the roller pair 2, 3. The fiber strand 6, drafted to the desired degree of fineness, is fed subsequently to a twist device of choice downstream of the drafting unit, for example an airjet arrangement, where the fiber strand 6 receives its spinning twist. The upper rollers 3 and 5 are positioned in relation to the driveable bottom rollers 2 and 4 and pressed by way of two holding devices 9. The upper rollers 3 and 5 themselves are hereby not driven, but rather are taken along by the motion of the bottom rollers 2, 4.

The holding device 9 is loaded with a pressing force F by way of loading devices (not shown) in the known and optional way, which holding device 9 can be raised together with the upper rollers 3 and 5 from the bottom rollers 2 and 4. The pressing force F can be applied by pneumatic or magnetic force generating elements or by means of metal springs.

As can be seen in FIG. 3, the upper rollers 3 of two adjacent spinning positions are combined by a joint axle 10 to form a twin pressure roller 11. Both bottom rollers 2 of these adjacent spinning positions can hereby be individual bottom rollers having separate drives. They can also be just as well designed as a continuous bottom cylinder extending in machine longitudinal direction in the way denoted by the broken line.

According to FIG. 1, the upper rollers 3, 5 are arranged in relation to the respective bottom roller 2, 4 with a slight overhang or recess. The arrangement of the upper roller 5 to the bottom roller 4 is denoted as recess when the upper roller 5, as seen in transport direction A, is arranged somewhat further upstream than the bottom roller 4. The roller pair 2, 3 shows an overhang of the upper roller 3, in which the upper roller 3 in the fiber transport direction A is arranged downstream of the bottom roller 2.

FIG. 2 shows a top view onto the roller pair 2, 3, whereby the holding device 9 is intersected along the intersectional surface II-II of FIG. 1. In the area of the center 12 of the axle 10 of the twin pressure roller 11, a positioning element 13, contained in the holding device 9, is provided. The positioning element 13 has a positioning surface 14, which acts together with the axle 10 and ensures the positioning of the twin pressure roller 11 with the desired overhang in relation to the bottom rollers 2. The positioning surfaces 14 have hereby a clearance fit with the axle 10, so that the twin pressure roller 11 can execute a movement like a pendulum in arrow directions B and C around the center 12. The capacity to move in pendulum fashion in arrow direction B and C in connection with the adjusted overhang or recess effects a self-regulatory alignment of the twin pressure roller parallel to the bottom rollers 2. An uneven nipping of the fiber strand 6, caused by a slanting of the upper roller 3 in relation to the bottom roller 2, and the consequent uneven drafting thereof is hereby avoided. The positioning surface 14 can hereby be designed slightly convex.

The larger the gauge E of the drafting unit 1 is, the larger the swivel distance which the upper roller 3 executes along the fiber transport direction A with the same oscillation angle of the axle 10 around the center 12. In the case of drafting units having a large gauge E of over 100 mm, as are applied as standard in airjet spinning machines, the oscillation motion of the twin pressure roller 11 becomes so large that when the twin pressure roller 11, having been raised from the bottom rollers 2 in order to eliminate a fault in the spinning process, are replaced on the bottom rollers 2, a faulty positioning of the twin pressure roller 11 can occur. It may happen that the axle 10 of the twin pressure roller 11 inclines to such an extent that one upper roller 3 with an overhang and the other upper roller 3 with a recess are disposed on the respective bottom rollers 2. This configuration renders the spinning process impossible. It is therefore provided that at least one catch bearing 15 is assigned to the twin pressure roller 11. The catch bearing 15 serves to approximately position the twin pressure roller 11 when being replaced on the bottom rollers 2 and to prevent faulty positioning of the twin pressure roller 11. The catch bearing 15 can hereby be arranged to the axle 10 of the twin pressure roller 11. The catch bearing 15 includes at least one catch surface 16, which limits the twin pressure roller 11 in its oscillation motion in direction B or C as soon as the oscillation angle exceeds a certain size. The catch bearing 15 is preferably arranged as far from the center 12 of the twin pressure roller 11 as possible. The catch surfaces 16 are thereby arranged at such a distance from the axle 10 of the twin pressure roller 11, that the surfaces 16 prevent a faulty placement of the twin pressure roller 11 on the bottom rollers 2, while not hindering the movement in pendulum fashion for the parallel alignment of the twin pressure roller 11. This aim can be more easily achieved the further away the catch bearing 15 is from the center 12.

The pressing force F must be transmitted through the holding device 9 into the axle 10 of the twin pressure roller. This can occur in that a force transmission element is integrated into the positioning element 13. In this embodiment (not shown), the pressing force F is distributed through the axle 10 onto both of the upper rollers 3 of the twin pressure roller 11. In the case of the drafting unit shown here having a large gauge E and having, in comparison thereto, a relatively small diameter D of the axle 10 of the twin pressure roller 11, the bowing under load of the axle 10 can, depending on the strength of the pressing force F, be so great that a slanted position of the upper rollers 3 due to the deforming occurs, which then in turn impairs the evenness of the drafted fiber strand. In the case of drafting units 1 for airjet spinning machines, the diameter D of the axle 10 is often less than a tenth of the gauge E. In order to avoid the unfavorably high deflection, it is advantageous to arrange force transmission elements 17, as shown in FIG. 3, separately from the positioning elements 13. The force transmission element is hereby arranged as closely as possible to the upper roller 3 and transmits the pressing force F from the holding device 9 through the pressing surfaces 18 onto the axle 10. The deflection of the axle 10 can thus be minimized. The pressing surfaces 18 are advantageously designed as even surfaces, which transmit the pressing force F onto the axle 10, without influencing the position of the axle 10 and without forcing the twin pressure roller into a position which may be false.

In an advantageous embodiment of the present invention, the catch bearing 15 is integrated into the force transmission element 17. The integrated component can be advantageously fork-like in design, in which the fork base comprises the pressure surfaces 18 and the lateral surfaces of the fork comprise the catch surfaces 16.

In the embodiment according to FIG. 3, in which the force transmission element 17 is arranged separated from the positioning element 13, it is important that the holding device 9 comprises a gap 19 in the positioning element 13, so that no force can be transmitted to the center 12 of the axle 10. In this embodiment, depending on the loading aggregate used, it can be advantageous to provide two pressing forces F′, denoted by a broken arrow, exactly on the force transmission elements 17, instead of one applied pressing force F in the center 12.

The upper roller 5 with the guiding belt 8 can, of course, be also designed, identical to the above described upper roller 3, as twin pressure roller 11, which is positioned in the same manner by way of a holding device 9 and loaded with a pressing force F.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

1. A holding device for a twin pressure roller of a drafting unit including a number of bottom rollers, the twin pressure roller including a stationary axle and two rotatably supported upper rollers, the holding device comprising: at least one positioning element assigned to the axle of the twin pressure roller and at least one force transmission element, wherein the positioning element is arranged in a center area of the axle of the twin pressure roller and permits the twin pressure roller to move in a pendulum fashion around the center; wherein the holding device, together with the twin pressure roller are liftable from the bottom roller; and at least one catch bearing assigned to the twin pressure roller for approximate positioning of the twin pressure roller when placed on the bottom rollers.

2. The holding device according to claim 1, wherein the catch bearing is assigned to the axle of the twin pressure roller.

3. The holding device according to claim 1, wherein at least two catch bearings are arranged at a distance to one another and in close proximity to the upper rollers.

4. The holding device according to claim 2, wherein at least two catch bearings are arranged at a distance to one another and in close proximity to the upper rollers.

5. The holding device according to claim 1, wherein the force transmission element is arranged separately from the positioning element.

6. The holding device according to claim 2, wherein the force transmission element is arranged separately from the positioning element.

7. The holding device according to claim 3, wherein the force transmission element is arranged separately from the positioning element.

8. The holding device according to claim 1, wherein the catch bearing is integrated into the force transmission element.

9. The holding device according to claim 5, wherein the force transmission element is arranged separately from the positioning element.

10. The holding device according to claim 1, wherein the force transmission element is integrated into the positioning element.

11. The holding device according to claim 2, wherein the force transmission element is integrated into the positioning element.

12. The holding device according to claim 3, wherein the force transmission element is integrated into the positioning element.