FIELD OF THE INVENTION

The present invention relates to mechanical pressure elements for top weighting arms in weighting units of a ring spinning machine for drafting fiber roving between drafting rollers and spinning the drafted fiber roving into a yarn.

BACKGROUND OF THE INVENTION

In the state of the art, pressure elements for top weighting arms in ring spinning machines for running and drawing fibers into a yarn are well known. It is advantageous, if the pressure on the top rollers or on the stretching cylinders to run and draw the fibers can be adjusted according to the prevailing conditions. Therefore, mechanic or pneumatic force generator elements are typically used as pressure elements for this purpose.

GB830614 A for example, published on March 1 6, 1 960, discloses a loading device for pressure rollers of drafting systems, in which the saddle provided with two or more pressure rollers is loaded, guided and fixed in a horizontal plane by means of a spring. The spring is retained by screws, which may be inserted into any of a number of holes in order to vary pressure exerted on the saddle by the spring.

Furthermore, CH41 9923 A for example, published on August 31 , 1 966 in the name of SKF Kugellagerfabriken GmbH, discloses a loading device for a drafting device, wherein springs are provided as loading means for the loading device. The pressure values of the springs can be adjusted or corrected by an abutment, which can be adjusted by means of a screw. The disadvantage of these mechanical force generator systems, however, is that the pressure of the spring impacts on a large contact surface of the saddle and the saddle then has to divide the pressure further to the pressure rollers. This often results in an unbalanced distribution, which leads to unfavorable pressure conditions and therefore to a less than optimal spinning

5 result.

Therefore, DE10201 5109269 A1 , published on November 24, 201 6 in the name of Maschinenfabrik Riefer AG, discloses another possible variation for a top weighting arm for top rollers of a drafting device, wherein the force generator is a mechanical force generator in the form of a compression spring. By fixing the compression spring in an opening of the first0 bridge or the guide rail of the top weighting arm, different lever arms on the transmission can be adjusted. As a result, the distance between the pressure surface and the axis of rotation of the output roller is enlarged or reduced, thereby causing different forces on the transmission device or the clamping device.

A further disadvantage of all these known mechanical force generator systems, however, is that the mechanical pressure element is arranged directly in the top weighting arm. Therefore, when the mechanical pressure element shall be repaired or replaced respectively, the whole drafting unit, i.e. the top and the lower rollers must be removed from the top weighting arm. Furthermore, in such arrangements, the access to the pressure elements is often difficult. Therefore, the pressure elements are often arranged in a supporting rod, wherein the top0 weighting arm is swivel-mounted to the supporting rod, and wherein the pressure rollers of the top weighting arm are loaded together by the pressure element arranged in the supporting rod.

US61 34752 A for example, published on October 24, 2000 in the name of Rieter Ingolstadt

Spinnereimaschinenbau AG, discloses a top weighting arm for a drafting device, in which all the top rollers of a top weighting arm are jointly loaded by means of a pneumatic force generator arranged in the supporting rod. In these pneumatic pressure elements, a rubber tube is provided inside the tube-shaped supporting rod, into which pressurized air can be admitted. However, pneumatic pressure elements have hereby the disadvantage that the rubber tube is subject to a high level of wear and material fatigue leads to fluctuations in pressure and/or to leakage.

W02005/052230 A1 for example, published on June 6, 2005 in the name of Maschinenfabrik Riefer AG, discloses possible options for loading a top weighting arm containing a pneumatic pressure element without the application of the rubber tube arranged in the supporting rod. This includes for example the variation in which mechanical levering devices or small pneumatic cylinders are arranged in the supporting rod, which can load the top rollers of the top weighting arms. However, this variation, which functions without the fault-prone rubber tube, has the disadvantage that the top rollers of the drafting device often cannot be pressed against the lower rollers with the necessary force required for drafting the fibre strand.

Therefore, IN01 31 1 K02006 A, published on July 1 1 , 2008 also in the name of Maschinenfabrik Riefer AG, and DE 102006004554 A1 , published on August 2, 2007 in the name of Wilhelm Stahlecker GmbH, disclose another possible option for loading a top weighting arm. In these variations, instead of a pneumatic pressure element, a mechanical pressure element comprises at least one cup spring or a helical spring. However, in their application, cup springs have the disadvantage that assembly and maintenance are timeconsuming because many individual discs are arranged in stacks. Furthermore, there is also a risk of malfunction due to incorrect assembly or layering of the individual discs and therefore, a mandrel or a sleeve is always necessary to guide the cup spring stack. Furthermore, the unfavorable fibre orientation of the material in cup springs favors the occurrence of material failure. A disadvantage of using a helical spring as a mechanical pressure element is its vibration sensitivity, which means that a helical spring has hardly any inherent damping. Another disadvantage of using a spring as a pressure element is that the pre-setting of the initial load of the spring force cannot be done optimally.

5 SUMMARY OF THE INVENTION

It is an overall objective of the present invention to advance the state of the art regarding the spring unit for top weighting arms. Favorably, one or more of the before-mentioned disadvantages of the prior art are overcome fully or partly.

In a general way, the overall objective is achieved by the subject-matter of the independent0 claims. Particularly advantageous embodiments are defined by the dependent claims and claim combinations, as well as the overall disclosure.

In an aspect, the overall objective is achieved by a mechanical pressure element for a top weighting arm in a ring spinning machine. The mechanical pressure element comprises a spring unit for providing a spring force for the top weighting arm and an adjustment device for regulating the spring force. The mechanical pressure element is characterized in that it is designed for receiving a discrete number of elements for selecting discrete spring force values of the spring unit. In particular, the mechanical pressure element is characterized in that it is designed for receiving a discrete number of at least two elements for selecting at least two discrete spring force values of the spring unit. In embodiments, the mechanical pressure0 element for a top weighting arm in a ring spinning machine comprises a spring unit and an adjustment device and is arranged in a supporting rod, whereby the top weighting arm is swivel-mounted on the supporting rod. Typically, the top weighting arm consists of a base part, which is swivel-mounted to the supporting rod and a movable bracket, onto which top rollers, to which the initially spring load is transmitted, are mounted while the bracket is rotatable mounted to a swivel axle of the base part. In order that the initial spring force can be transmitted to the top rollers and thus the top rollers can be pressed against the lower rollers, typically a rocking lever mounted in an axle is attached to the base part of the top weighting arm, which loads the bracket via a pressure bolt and thus presses the top rollers

5 against the respective lower rollers. For this purpose, the rocking lever has an extension on its side facing away from the pressure bolt, which projects through an opening into the inside of the supporting rod and thus into the mechanical pressure element. By selecting a preload force and/or a spring force characteristic of the spring, the extension is now pushed in the direction out of the supporting rod, whereby the force is transmitted via the rocking lever to0 the bracket of the top weighting arm and thus to the top rollers. As a result, all top rollers, which are arranged on the movable bracket of the top weighting arm, can jointly be loaded by means of the mechanical pressure element and all these top rollers are pressed against the lower rollers with the same initial spring force, which is required for running and drawing the fiber strands. Thereby the mechanical pressure element may comprise any spring unit, which is suitable for providing the desired initial loads.

In the context of this disclosure, it is understood that one weighting unit, which comprises a top weighting arm and at least one drafting unit, can be assigned to two drafting units. This means, that two drafting units can be adjusted by one mechanical pressure element in a top weighting arm. Furthermore, the ring spinning machine may comprise several weighting units0 with at least two drafting units per weighting unit.

In embodiments, the spring unit of the mechanical pressure element can be designed to be used in a supporting rod having a torsional moment of inertia, wherein the supporting rod can be formed by a hollow profile or by a solid profile, which only comprises recesses for the mechanical pressure element. In order to be able to adjust the desired initial spring force acting on the extension at the top weighting arm, i.e. in order to be able to adjust the desired spring force to the prevailing conditions accordingly for running and drawing of thefiber, an adjustment device is arranged to the spring unit of the mechanical pressure element. The adjustment device controls the

5 initial spring force by adjusting the spring force of the spring unit in a discrete number of graded steps. The adjustment device of the mechanical pressure element comprises a space for receiving at least one element, wherein the adjustment device and thus the element(s) is or are attached to the spring unit for selecting the discrete spring force values. By completely inserting or removing the element(s) in the space of the adjustment device, the initial spring0 force on the spring unit can be changed in graded steps with a predetermined discrete number of pretensioning spring forces. In particular, each element can be completely inserted or removed individually. Therefore, the discrete value of the initial spring force on the spring unit can be predetermined and adjusted in discrete graduated steps.

In embodiments, the adjustment device of the mechanical pressure element comprises a space for receiving at least two elements, wherein the adjustment device and thus the at least two elements are attached to the spring unit for selecting the discrete spring force values. The at least two discrete elements do not allow to select continuous spring force values of the spring unit.

In embodiments, e.g. depending on the application, the element(s) may be spring-0 pretensioning elements, in particular for selecting a preload force and/or a spring force characteristic of the spring unit, wherein the element may be any elements designed for such a preload force and/or spring force characteristic.

In embodiments, the element(s) may be spring-modifying elements, e.g. bolts, in particular for selecting a preload force and/or a spring force characteristic of the spring unit. In embodiments, the element(s) may be spring-pretensioning elements, e.g. platelet inserts for selecting a preload force and/or a spring force characteristic of the spring unit.

In embodiments, the mechanical pressure element is arranged in a housing, which comprises a recess such that the spring unit can be pressed onto by the top weighting arm through the

5 recess. Furthermore, the spring unit of the mechanical pressure element may be arranged in the housing under a defined pretension, and may be adjusted by the adjustment device. The housing of the mechanical pressure element may be made of plastic such as PVC and may be formed integrally or may be composed of two half shells, in particular of two identical half shells that have clips for being clipped together and for pretensioning the spring unit there¬0 between. The clips are designed in such a way that the two identical half shells can releasably be clipped together.

The housing can be used for an easier purpose of guiding and positioning the mechanical pressure element in the supporting rod. In such embodiments, the mechanical pressure element can be inserted, together with its housing, into the inside of the supporting rod and is positioned exactly on the spot at which the extension of the rocking lever of the top weighting arm projects into the inside of the supporting rod. Preferably, the housing can be designed as a hexagonal profile, which is fittable into a hexagonally shaped, in particular hexagonally hollow, supporting rod for the top weighting arm in the ring spinning machine. Typically, the respective width across flats of the housing is dimensioned in such a way that0 the housing may be inserted precisely into the inner of the supporting rod, whereby the wall thickness of the housing depends on the torsional moment of inertia of the supporting rod and may thus serve as an additional reinforcement to the wall thickness of the supporting rod.

The position of the recess is on the side of the housing where the opening of the supporting rod is located, i.e. the position of the recess is on the side of the housing such that the recess of the housing and the opening of the supporting rod can lie one above the other, and therefore the extension of the rocking lever of the top weighting arm can continue to project into the supporting rod respectively into the mechanical pressure element when bringing the top weighting arm into a closed state. Furthermore, the recess of the housing may be a

5 square-, a round- or an oval-shaped recess and can be dimensioned in its size at least such that the extension of the rocking lever of the top weighting arm can protrude into the opening and can be pushed back in the direction out of the supporting rod by the initially loaded force.

Since a ring spinning machine may comprise several weighting units with at least two drafting units per weighting unit, the respective housings may be releasably connected to each other0 for even easier guiding and positioning of the respective housing and therefore the respective mechanical pressure element in the supporting rod.

The term "releasably connected" used herein broadly encompasses that the connection can be released without destroying the connected components, respectively parts thereof. Furthermore, the two components are in the non-connected state completely separated from each other. For example, a material bonding, such as gluing or welding is not a releasable connection, because it cannot be released without destroying, respectively altering, the two connected components. Additionally, a releasable connection can undergo multiple connection/disconnection cycles. Preferably, the releasable connection can be released without applying considerable forces. 0 In embodiments, depending on the application, the housing may comprise a groove at one end and a corresponding tongue at the other end in the longitudinal direction in order to detachably connect the individual housings to each other by a groove-tongue form-fit.

In embodiments, depending on the application, the housing may comprise a connection element. The connection element can comprise a connection groove and a connection tongue, wherein the connection groove and the connection tongue are corresponding to the tongue respectively groove of the housing and may be releasably attached to the housing by means of a groove-tongue form-fit. The connection element releasably connect the housings to each other at their respective ends in longitudinal direction by a groove-tongue form-fit.

5 The connection elements may be used for connecting several housings in a row and as a spacer between the individual housings. Therefore, the connection elements are designed in such a way that the recess of the respective housing and the respective opening of the supporting rod can lie one above the other, and therefore the extension of the rocking lever of the top weighting arm can continue to project into the supporting rod respectively into the0 mechanical pressure element when bringing the top weighting arm into a closed state.

In embodiments, depending on the application, the element(s) is or are spring-pretensioning element(s) for selecting a preload force and/or a spring force characteristic of the spring unit. In particular, the element(s) is or are platelet inserts that are arranged on the spring unit for reducing a distance to the recess. Thereby the extension will be pushed back with a higher spring force in the direction out of the supporting rod and thus all the top rollers are jointly loaded with a higher spring force respectively a higher pressure against the lower rollers. By completely inserting or removing individual platelet inserts, the preload spring force can thus be adjusted in graded steps with a discrete number of pretensioning spring forces.

In embodiments, the discrete graded steps of the pretensioning spring forces for adjusting the0 preloaded spring force can be predetermined by selecting a number and/or thickness of the platelet inserts. In particular, the platelet inserts of equal and/or different thicknesses can be selected. In other words, by completely inserting or removing one or more platelet inserts of equal and/or different thicknesses, the initial load of the preload spring force can be set at a predetermined discrete value and can be varied in discrete graded steps by inserting or removing one or more platelet inserts. In such embodiments, the spring unit of the mechanical pressure element can be a C-shaped spring or a leaf spring.

In embodiments, depending on the application, the adjustment device further comprises an additional pusher. The pusher may be arranged between the spring unit and the spring-

5 pretensioning element(s) for reducing the distance to the recess. In such embodiments, the spring-pretensioning element(s) for selecting a preload force and/or a spring force characteristic of the spring unit will be arranged on the pusher of the adjustment device.

In embodiments, depending on the application, the spring unit of the mechanical pressure element is a leaf spring, wherein the leaf spring comprises at least one leaf spring element. In0 such embodiments, the element(s) is or are spring-modifying elements, for selecting a preload force and/or a spring force characteristic of the spring unit. In particular, the element(s) is or are bolts that are arranged underneath and at one end of the leaf spring for reducing an effective length of the leaf spring. Thereby the extension will be pushed back with a higher spring force in the direction out of the supporting rod and thus all the top rollers are jointly loaded with a higher spring force respectively a higher pressure against the lower rollers. By inserting or removing the elements, in particular the bolts, at the predetermined positions underneath of the leaf spring, the preload spring force can thus be adjusted in graded steps with a predetermined discrete number of pretensioning spring forces by reducing the effective length of the leaf spring, wherein each of the element in particular each0 of the bolts, can be inserted or removed individually.

In embodiments, a predetermined preload spring force and/or a modified spring force characteristic of the spring unit can be adjusted by varying the number of the elements, in particular the bolts, and/or varying the size, in particular diameter, of the elements, in particular of the bolts, and/or by varying the distance between the arranged elements, in particular bolts, underneath of the leaf spring. If more than one element, in particular more than one bolt, is used to adjust the predetermined discrete preload spring force and/or to modify the spring force characteristic of the spring unit, the elements, respectively the bolts, used together preferably all have the same diameter.

5 In embodiments, the adjustment device can comprise insertion spaces for receiving and holding the elements, in particular the bolts. In Particular, the insertion spaces can be semicircular insertion spaces. Moreover, in particular, the insertion spaces can determine the available preselected distances for reducing the effective length of the leaf spring. In embodiments, the shape and/or the size of the insertion spaces can be adaptable to the size,0 in particular to the diameter, of the elements, in particular of the bolts.

In embodiments, at least one element is provided for the adjustment device of the mechanical pressure element for regulating a preload force and/or a spring force characteristic of the spring unit .The number of the element(s) can depend on the number of desired adjustable graded steps and can be provided in such a way that an optimal preloaded spring force and/or spring force characteristic is ensured for the respective process of running and drawing the fiber strands. By inserting or removing the elements, the preload spring force can be increased or decreased in determined graded steps, wherein the element(s) may be spring- pretensioning elements, i.e. platelet inserts for example, or spring-modifying elements, i.e. bolts for example. 0 BRIEF DESCRIPTION OF THE DRAWINGS

The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered to be limiting to the invention, which is described in the appended claims. The drawings show in:

5 Fig. 1 A perspective view of a variation of a weighting unit containing a mechanical pressure element in a top weighting arm and two drafting units for a ring spinning machine according to the invention;

Fig. 2 A perspective view of a variation of a top weighting arm mounted on a supporting rod containing a mechanical pressure element for a ring spinning machine0 according to the invention;

Fig. 3 A top weighting arm according to Fig. 2 in a) an opened position and b) a closed position;

Fig.4 A perspective view of a variation of a housing for a mechanical pressure element for a ring spinning machine according to the invention;

Fig. 5 A housing according to Fig. 4 in a) a cross-sectional view on the sectional plane B-B b), a side view, and c) in a cross-sectional view on the sectional plane A-A;

Fig. 6 A mechanical pressure element in a housing according to the invention in a) a front view and b) a cross-sectional view on the sectional plane C-C;

Fig. 7 A perspective view of an alternative variation of a mechanical pressure element0 according to the invention; Fig. 8 A mechanical pressure element according to Fig. 7 in a) a front view and b) a cross-sectional view through the sectional plane D-D;

Fig. 9 A perspective view of an alternative embodiment of a mechanical pressure element according to the invention;

Fig. 10 A mechanical pressure element according to Fig. 9 in a a) a front view and b) a cross-sectional view through the sectional plane E-E;

Fig. 1 1 Perspective views of a connection element in a) and b), of a housing in c) and d), and of connected housings e) of a mechanical pressure element according to the invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Embodiments disclosed herein may be embodied in many different forms, may include variations in one of more features or aspects, and may in general be combined with one another. Embodiments should not be construed as being limiting; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. In general, same reference numbers shall refer to same or similar components or parts.

Figure 1 shows an embodiment of a top weighting unit for a ring spinning machine. The top weighting unit 1 is mounted on a supporting rod 6 and comprises a top weighting arm 2, which comprises a base part 7 and a bracket 8, and two drafting units 3, wherein each drafting unit 3 contains three top rollers 4 and three lower rollers 5. The mechanical pressure element 1 2 in these embodiments adjust and control two drafting units 3 with its initial spring force of the spring unit.

Figure 2 shows an embodiment of a top weighting arm mounted on a supporting rod containing a mechanical pressure element for a ring spinning machine, wherein the top

5 weighting arm 2 comprises a base part 7 and a movable, e.g. openable and closable, bracket 8. Furthermore, the bracket 8 of the top weighting arm 2 comprises three support elements 27 to each of which a top roller for the two drafting units can be attached. In this embodiment, the supporting rod 6 can be formed as a hexagonal hollow profile and can have a torsional moment of inertia. The mechanical pressure element can be arranged in a housing 9, wherein0 the housing 9 is designed as a hexagonal profile dimensioned in such a way, that the housing 9 can be inserted precisely into the inner of the supporting rod 6.

In the opened position, the spring unit 1 3 of the mechanical pressure element 1 2 does not push the extension 1 1 of the rocking lever, which is mounted to the base part 7 of the top weighting arm 2, with an initial spring force in the direction out of the supporting rod 6. Therefore, the extension 1 1 projects in a higher amount through the recess 14 of the housing 9 onto the spring unit 1 3 of the mechanical pressure element, as illustrated in Figure 3a. Because of the torsional moment of inertia, the extension 1 1 of the rocking lever is pushed outwards, i.e. in the direction out of the supporting rod 6, when the top weighting arm 2 is in its closed position, as illustrated in Figure 3b. By selecting a preload force and/or modifying a0 spring force characteristic of the spring unit 1 3, the extension 1 1 is now pushed back with a higher spring force in the direction out of the supporting rod 6, whereby the force is transmitted via the rocking lever on the bracket 8 of the top weighting arm 2 and thus on the top rollers. As a result, all top rollers, which are arranged on the movable bracket 8 of the top weighting arm 2, are jointly loaded by means of the mechanical pressure element and thus all top rollers are pressed against the lower rollers with the same initial spring force, which is required for running and drawing the fiber strand.

Figure 4 to Figure 5 show a variation of a housing 9 for a mechanical pressure element arranged inside (not visible). The housing 9 comprises a recess 14 and is composed of two

5 identical half shells 1 5, which are releasably clipped together by clips 10 as can be seen best in detail of Figure 5c. When the two identical half shells 1 5 are clipped together by clips 10, the two half shells 1 5 form a stable guide rail 1 6 on each side, as can be seen best in detail of Figure 5a, to stabilize the two half shells 1 5 and to prevent a moving of the two half shells 1 5 against each other. 0 Figure 6 shows a variation of a mechanical pressure element 1 2 in a housing 9 composed of two identical half shells 1 5. In this variation, one platelet insert 18 is used to select a preload force and/or to modify a spring force characteristic of the C-shaped spring 1 7. The platelet insert 18 is arranged e.g. on the C-shaped spring 1 7 and reduces the distance to the recess 1 4 and therefore in the closed position of the top weighting arm, pushes back the extension in direction out of the recess 14 and the supporting rod with the preloaded spring force being biased according to the selected discrete number of the platelet insert 18.

Figure 7 to Figure 8 show another variant of a mechanical pressure element 1 2 in a housing 9. In this variant, four bolts 21 are used to select a preloaded force and/or to modify a spring force characteristic of the leaf spring 1 9. The bolts 21 of the adjustment device 20 are0 arranged underneath at one end of the leaf spring 1 9. By inserting or removing the bolts 21 at the predetermined position underneath the leaf spring 1 9, the preload spring force can thus be adjusted in graded steps by reducing or expanding the effective length of the leaf spring 1 9. In this variation, the initial spring force can be selected out of for example four graded steps by inserting or removing the four bolts 21 . Figure 9 to Figure 10 show another variant of a mechanical pressure element 1 2 in a housing 9. In this variant one platelet insert 18 is used to select a preload force and/or to modify a spring force characteristic of the leaf spring 1 9. Furthermore, in this variant, the adjustment device 20 comprises an additional pusher 28, which is arranged between the leaf spring 1 9

5 and the platelet insert 18, to reduce the distance to the recess 14. The platelet insert 18 can be arranged on the pusher 28 and therefore in the closed position of the top weighting arm, pushes back the extension in direction out of the recess 14 and the supporting rod with the preloaded spring force being biased according to the selected discrete number of the platelet inserts 18. 0 Since a ring spinning machine may comprise several weighting units 1 with at least two drafting unis 3 per weighting unit 1 the housings 9, which each contain a mechanical pressure element, may for easier guiding and positioning in the supporting rod 6 can be releasably connected to each other. For the correct positioning of each of the housings 9 in the supporting rod 6 in such a way that the recess of the respective housing 9 and the respective opening of the supporting rod 6 can lie one above the other, the housings 9 can be releasably connected to each other via a connection element 22 as exemplarily shown in Figure 1 1 e. Therefore, each of the connection elements 22 can comprise a connection groove 23 and a connection tongue 24 as seen best in Figure 1 1 a and 1 1 b. The connection groove 23 and connection tongue 24 correspond to the tongue 26 and groove 25 of the housing 9, which0 can be seen best in Figure 1 1 c and 1 1 d, and the connection elements 22 can be releasably attached to the housing 9 by a groove-tongue form-fit. LIST OF DESIGNATIONS

1 Weighting unit 1 5 Half shells

2 Top weighting arm 1 6 guide rails

3 Drafting unit 1 7 C-shaped spring

5 4 Top rollers 18 Element, platelet insert

5 Lower rollers 1 9 Leaf spring

6 Supporting rod 20 Adjustment device

7 Base part 21 Element(s), bolt(s)

8 Bracket 22 Connection element0 9 Housing 23 Connection groove

1 0 Clips 24 Connection tongue

1 1 Extension 25 Groove

1 2 Mechanical pressure element 26 Tongue

1 3 Spring unit 27 Support element5 1 4 Recess 28 Pusher