Spring unit for top weight arm

Abstract

The invention relates to a mechanical pressure element for a top weight arm (2) in a ring spinning machine. The mechanical pressure element comprises a spring unit (13) for providing a spring force for the top weight arm (2) and an adjusting device for adjusting the spring force. The mechanical pressure element is characterized in that it is designed to receive a discrete number of elements for selecting discrete spring force values of the spring unit (13).

Description

Technical Field

[0001] The invention relates to a mechanical pressure element of a top counterweight arm for use in a counterweight unit of a ring spinning machine for drafting a fiber roving between drafting rollers and spinning the drafted fiber roving into yarn. Background Art

[0002] Pressure elements for top counterweight arms in ring spinning machines for extending and stretching fibers into yarn are well known in the prior art. It is advantageous if the pressure on the top roller or on the stretching drum for extending and stretching the fibers can be adjusted according to the prevailing conditions. Therefore, mechanical or pneumatic force generator elements are typically used as pressure elements for this purpose.

[0003] For example, GB830614A published on March 16, 1960 discloses a loading device for a pressure roller of a drafting system, in which a 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 held by a screw which can be inserted into any one of a plurality of holes in order to change the pressure applied by the spring on the saddle.

[0004] Furthermore, for example, CH419923A published on August 31, 1966 in the name of SKF Kugellagerfabriken GmbH discloses a loading device for a drafting device, wherein a spring is provided as a loading means for the loading device. The pressure value of the spring can be adjusted or corrected by a support, which can be adjusted by means of a screw.

[0005] However, the disadvantage of these mechanical force generator systems is that the pressure of the spring impinges on the large contact surface of the saddle, and the saddle must then distribute the pressure further to the pressure roller. This usually leads to an unbalanced distribution, which leads to unfavorable pressure conditions and therefore to less than optimal spinning results.

[0006] Thus, DE 10 2015 109 269 A1 published on November 24, 2016 in the name of Maschinenfabrik Rieter AG discloses another possible variant of a top counterweight arm for a top roller 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 the opening of the first bridge part or guide rail of the top counterweight arm, different lever arms on the transmission can be adjusted. As a result, the distance between the pressure surface and the rotation axis of the output roller is enlarged or reduced, thereby causing different forces on the transmission or clamping device.

[0007] However, a further disadvantage of all these known mechanical force generator systems is that the mechanical pressure element is arranged directly in the top counterweight arm. Therefore, when the mechanical pressure element is to be repaired or replaced, respectively, the entire drafting unit, i.e. the top roller and the lower roller, must be removed from the top counterweight arm. Furthermore, in such an arrangement, access to the pressure element is usually difficult. Therefore, the pressure element is usually arranged in a support rod, wherein the top counterweight arm is pivotally mounted to the support rod and wherein the pressure rollers of the top counterweight arm are loaded together by the pressure element arranged in the support rod.

[0008] For example, US6134752A, published on October 24, 2000 in the name of Rieter Ingolstadt Spinnereimaschinenbau AG, discloses a top counterweight arm for a drafting device, in which all top rollers of the top counterweight arm are loaded together by means of a pneumatic force generator arranged in a support rod. In these pneumatic pressure elements, a rubber tube is arranged inside the tubular support rod, into which pressurized air can be admitted. However, pneumatic pressure elements thus have the disadvantage that the rubber tube is subject to a high level of wear and material fatigue leads to fluctuations in pressure and / or leaks.

[0009] For example, WO 2005 / 052230 A1 published on June 6, 2005 in the name of Maschinenfabrik Rieter AG discloses possible options for loading a top counterweight arm comprising a pneumatic pressure element without the use of a rubber tube arranged in the support rod. This includes variants in which, for example, a mechanical lever arrangement or a small pneumatic cylinder is arranged in the support rod, which can load the top roller of the top counterweight arm. However, such variants, which function without a rubber tube that is prone to failure, have the disadvantage that the top roller of the drafting device cannot usually be pressed against the lower roller with the necessary force required for drafting the fiber bundle.

[0010] Therefore, IN01311KO2006A, also published on July 11, 2008 in the name of Maschinenfabrik Rieter AG, and DE102006004554A1, published on August 2, 2007 in the name of Wilhelm Stahlecker GmbH, disclose another possible option for loading the top counterweight arm. In these variants, instead of a pneumatic pressure element, the 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 time-consuming because many individual discs are arranged in a stack. In addition, there is also a risk of failure due to incorrect assembly or delamination of the individual discs, and therefore, a spindle or sleeve is always required to guide the cup spring stack. In addition, the unfavorable fiber orientation of the material in the cup spring is conducive to the occurrence of material failure. The disadvantage of using a helical spring as a mechanical pressure element is its vibration sensitivity, which means that the helical spring has almost no inherent damping. Another disadvantage of using a spring as a pressure element is that the presetting of the initial load of the spring force cannot be done optimally. Summary of the invention

[0011] A general object of the present invention is to advance the prior art relating to spring units for top counterweight arms. Advantageously, one or more of the aforementioned disadvantages of the prior art are overcome in whole or in part.

[0012] In general, this general object is achieved by the subject matter of the independent claims. Particularly advantageous embodiments are defined by the dependent claims and claim combinations as well as the overall disclosure.

[0013] In one aspect, the overall purpose is achieved by a mechanical pressure element for a top counterweight arm in a ring spinning machine. The mechanical pressure element includes a spring unit for providing a spring force to the top counterweight arm and an adjustment device for adjusting the spring force. The mechanical pressure element is characterized in that it is designed to receive a discrete number of elements for selecting a discrete spring force value of the spring unit. In particular, the mechanical pressure element is characterized in that it is designed to receive at least two elements of a discrete number of at least two discrete spring force values ​​for selecting the spring unit. In an embodiment, the mechanical pressure element for the top counterweight arm in the ring spinning machine includes a spring unit and an adjustment device, and is arranged in a support rod, whereby the top counterweight arm is swivel mounted on the support rod. Typically, the top counterweight arm consists of a base portion and a movable bracket, the base portion is swivel mounted to the support rod, the top roller is mounted on the movable bracket, the initial spring load is transmitted to the top roller, and the bracket can be rotatably mounted to the swivel shaft of the base portion. In order to make the initial spring force transferable to the top roller and thus the top roller can be pressed against the lower roller, a rocker typically mounted in an axle is attached to the base portion of the top counterweight arm, which loads the bracket via a pressure bolt and thus presses the top roller against the corresponding lower roller. For this purpose, the rocker has an extension on its side facing away from the pressure bolt, which protrudes through an opening into the interior of the support rod and thus into the mechanical pressure element. By selecting the preload force and / or spring force characteristics of the spring, the extension is now pushed in the direction away from the support rod, whereby the force is transferred to the bracket of the top counterweight arm via the rocker and thus to the top roller. As a result, all the top rollers arranged on the movable bracket of the top counterweight arm can be loaded together by means of the mechanical pressure element, and all these top rollers are pressed against the lower roller with the same initial spring force, which is required to extend and stretch the fiber bundle. Therefore, the mechanical pressure element can include any spring unit suitable for providing the desired initial load.

[0014] In the context of the present disclosure, it is understood that one counterweight unit comprising a top counterweight arm and at least one drafting unit can be assigned to two drafting units. This means that the two drafting units can be adjusted by one mechanical pressure element in the top counterweight arm. Furthermore, the ring spinning machine can comprise several counterweight units, each having at least two drafting units.

[0015] In an embodiment, the spring unit of the mechanical pressure element can be designed for use in a support rod having a torsional moment of inertia, wherein the support rod can be formed by a hollow profile or by a solid profile which comprises only a recess for the mechanical pressure element.

[0016] In order to be able to adjust the desired initial spring force acting on the extension at the top counterweight arm, that is, in order to be able to adjust the desired spring force accordingly for the extension and stretching of the fiber for the conditions at the time, an adjustment device is arranged to the spring unit of the mechanical pressure element. The adjustment device controls the initial spring force by adjusting the spring force of the spring unit in a discrete number of graduated steps. The adjustment device of the mechanical pressure element includes a space for receiving at least one element, wherein the adjustment device and therefore (one or more) elements are attached to the spring unit for selecting discrete spring force values. By completely inserting or removing (one or more) elements in the space of the adjustment device, the initial spring force on the spring unit can be changed in graduated steps using a predetermined discrete number of pre-tensioning spring forces. In particular, each element can be completely inserted or removed individually. Therefore, the discrete values ​​of the initial spring force on the spring unit can be predetermined and adjusted in discrete graduated steps.

[0017] In an embodiment, 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 discrete spring force values. The at least two discrete elements do not allow selecting continuous spring force values ​​of the spring unit.

[0018] In an embodiment, e.g. depending on the application, the element(s) may be a spring pretensioning element, in particular for selecting a preload force and / or spring force characteristics of the spring unit, wherein the element may be any element designed for such a preload force and / or spring force characteristics.

[0019] In an embodiment, the element(s) may be a spring modification element, such as a bolt, in particular for selecting a preload force and / or a spring force characteristic of the spring unit.

[0020] In an embodiment, the element(s) may be a spring pretensioning element, such as a plate-like insert for selecting a preload force and / or a spring force characteristic of the spring unit.

[0021] In an embodiment, the mechanical pressure element is arranged in a housing, which comprises a recess, so that the spring unit can be pressed onto it by the top counterweight arm through the recess. Furthermore, the spring unit of the mechanical pressure element can be arranged in the housing under a defined pretension and can be adjusted by an adjustment device. The housing of the mechanical pressure element can be made of a plastic such as PVC and can be formed in one piece or can consist of two half shells, in particular of two identical half shells, which have a clip for being clipped together and for pretensioning the spring unit therebetween. The clip is designed so that the two identical half shells can be releasably clipped together.

[0022] The housing can be used for the easier purpose of guiding and positioning the mechanical pressure element in the support rod. In such an embodiment, the mechanical pressure element can be inserted into the interior of the support rod together with its housing and precisely positioned at the point where the extension of the rocker of the top counterweight arm protrudes into the interior of the support rod. Preferably, the housing can be designed as a hexagonal profile, which can be fitted into a hexagonal, in particular hexagonal hollow, support rod for the top counterweight arm in a ring spinning machine. Typically, the corresponding width dimension across the flat part of the housing is designed in such a way that the housing can be precisely inserted into the interior of the support rod, whereby the wall thickness of the housing depends on the torsional moment of inertia of the support rod and can therefore serve as an additional reinforcement to the wall thickness of the support rod.

[0023] The position of the recess is on the side of the housing where the opening of the support rod is located, i.e. the position of the recess is on the side of the housing so that the recess of the housing and the opening of the support rod can be located one above the other and thus when the top counterweight arm is brought into the closed state, the extension of the rocker of the top counterweight arm can continue to protrude into the support rod, into the mechanical pressure element, respectively. Furthermore, the recess of the housing can be a square, circular or oval recess and can be dimensioned in size so that at least the extension of the rocker of the top counterweight arm can protrude into the opening and can be pushed back in the direction away from the support rod by the initial loading force.

[0024] Since the ring spinning machine can comprise several counterweight units, each having at least two drafting units, the respective housings can be releasably connected to one another in order to even more easily guide and position the respective housing and therefore the respective mechanical pressure element in the support rod.

[0025] As used herein, the term "releasably connected" broadly encompasses a connection that can be released without destroying the connected components, or (respectively) parts thereof. In addition, two components are in a non-connected state that is completely separated from each other. For example, a material bond such as gluing or welding is not a releasable connection because it cannot be released without destroying or changing the two connected components. In addition, a releasable connection can undergo multiple connect / disconnect cycles. Preferably, a releasable connection can be released without applying considerable force.

[0026] In an embodiment, 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.

[0027] In an embodiment, depending on the application, the housing may include a connecting element. The connecting element may include a connecting groove and a connecting tongue, wherein the connecting groove and the connecting tongue correspond to the tongue, the groove of the housing, respectively, and can be releasably attached to the housing by means of a groove-tongue form fit. The connecting element releasably connects the housings to each other at their respective ends in the longitudinal direction by means of a groove-tongue form fit. The connecting element can be used to connect several housings in a row and serve as a spacer between separate housings. Therefore, the connecting element is designed in such a way that the recess of the corresponding housing and the corresponding opening of the support rod can be located one above the other, and therefore when the top counterweight arm is brought into the closed state, the extension of the rocker of the top counterweight arm can continue to protrude into the support rod or into the mechanical pressure element.

[0028] In an embodiment, the element(s) are spring pretensioning elements(s) for selecting the preload force and / or the spring force characteristics of the spring unit, depending on the application. In particular, the element(s) are plate-like inserts arranged on the spring unit for reducing the distance to the recess. Thus, the extension will be pushed back with a higher spring force in the direction away from the support rod and thus all top rollers will be loaded together with a higher spring force or a higher pressure against the lower rollers. By completely inserting or removing a separate plate-like insert, the preload spring force can thus be adjusted in graduated steps with a discrete number of pretensioning spring forces.

[0029] In an embodiment, the discrete graduated steps of the pretensioning spring force for adjusting the preload spring force can be predetermined by selecting the number and / or thickness of the plate-like inserts. In particular, plate-like inserts with the same and / or different thicknesses can be selected. In other words, by completely inserting or removing one or more plate-like inserts with equal and / or different thicknesses, the initial load of the preload spring force can be set to a predetermined discrete value and can be varied in discrete graduated steps by inserting or removing one or more plate-like inserts. In such an embodiment, the spring unit of the mechanical pressure element can be a C-shaped spring or a leaf spring.

[0030] In an embodiment, depending on the application, the adjustment device further comprises an additional pusher. The pusher may be arranged between the spring unit and the spring pretensioning element(s) for reducing the distance to the recess. In such an embodiment, the spring pretensioning element(s) for selecting the preload force and / or the spring force characteristics of the spring unit will be arranged on the pusher of the adjustment device.

[0031] In an embodiment, 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. In such an embodiment, the element(s) are spring modifying elements for selecting the preload force and / or spring force characteristics of the spring unit. In particular, the element(s) are bolts arranged below the leaf spring and at one end of the leaf spring for reducing the effective length of the leaf spring. Thus, the extension will be pushed back with a higher spring force in the direction away from the support rod, and thus all top rollers will be loaded together with a higher spring force or a higher pressure against the lower rollers. By inserting or removing an element, in particular a bolt, at a predetermined position below the leaf spring, the preload spring force can therefore be adjusted in stepped steps by reducing the effective length of the leaf spring with a predetermined discrete number of pretensioning spring forces, wherein each of the elements, in particular each of the bolts, can be inserted or removed individually.

[0032] In an embodiment, the predetermined preload spring force and / or the modified spring force characteristic of the spring unit can be adjusted by changing the number of elements, in particular bolts, and / or changing the size, in particular the diameter, of the elements, in particular bolts, and / or by changing the distance between the elements, in particular bolts, arranged below 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 or bolts used together preferably all have the same diameter.

[0033] In an embodiment, the adjustment device can include an insertion space for receiving and holding the element, in particular the bolt. In particular, the insertion space can be a semicircular insertion space. Furthermore, in particular, the insertion space can determine the available preselected distance for reducing the effective length of the leaf spring. In an embodiment, the shape and / or size of the insertion space can be adapted to the size, in particular the diameter, of the element, in particular the bolt.

[0034] In an embodiment, at least one element is provided for the adjustment device of the mechanical pressure element for adjusting the preload force and / or the spring force characteristics of the spring unit. The number of element(s) may depend on the desired number of adjustable step sizes and may be provided in such a way that an optimal preload spring force and / or spring force characteristics are ensured for the respective processes of extending and stretching the fiber bundle. The preload spring force may be increased or decreased in defined step sizes by inserting or removing elements, wherein the element(s) may be a spring pretensioning element, i.e., for example a plate-shaped insert, or a spring modifying element, i.e., for example a bolt. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention described herein will be more fully understood from the detailed description given below and the accompanying drawings, which should not be considered as limiting the invention described in the appended claims. The accompanying drawings show the following:

[0036] Figure 1 A perspective view showing a variant of a counterweight unit for a ring spinning machine according to the invention, the counterweight unit comprising two drafting units and a mechanical pressure element in the top counterweight arm;

[0037] Figure 2 A perspective view showing a variant of a top counterweight arm for a ring spinning machine according to the invention, the top counterweight arm being mounted on a support rod containing a mechanical pressure element;

[0038] Figure 3 Shown in a) open position and b) closed position according to Figure 2 The top counterweight arm;

[0039] Figure 4 A perspective view showing a variant of a housing for a mechanical pressure element for a ring spinning machine according to the invention;

[0040] Figure 5 a) a sectional view on the section plane BB, b) a side view and c) a sectional view on the section plane AA show the Figure 4 Shell;

[0041] Figure 6 The mechanical pressure element in the housing according to the invention is shown in a) a front view and b) a sectional view on the section plane CC;

[0042] Figure 7 A perspective view showing an alternative variant of the mechanical pressure element according to the invention;

[0043] Figure 8 a) a front view and b) a sectional view through the section plane DD according to Figure 7 Mechanical pressure elements;

[0044] Fig. 9 A perspective view showing an alternative embodiment of a mechanical pressure element according to the invention;

[0045] Fig.10 a) a front view and b) a sectional view through the section plane EE according to Fig. 9 Mechanical pressure elements;

[0046] Fig.11 A perspective view of the connecting element in a) and b), a perspective view of the housing in c) and d) and a perspective view of the connected housing e) of a mechanical pressure element according to the invention are shown. DETAILED DESCRIPTION

[0047] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all, features are shown. The embodiments disclosed herein may be embodied in many different forms, may include variations in one or more features or aspects, and generally may be combined with one another. The embodiments should not be construed as limiting; rather, these embodiments are provided so that the disclosure will satisfy applicable legal requirements. In general, the same reference numerals shall refer to the same or similar components or parts.

[0048] Figure 1 An embodiment of a top counterweight unit for a ring spinning machine is shown. The top counterweight unit 1 is mounted on a support rod 6 and comprises a top counterweight arm 2 (which comprises a base part 7 and a bracket 8) and two drafting units 3, wherein each drafting unit 3 comprises three top rollers 4 and three lower rollers 5. In these embodiments, the mechanical pressure element 12 adjusts and controls the two drafting units 3 using the initial spring force of its spring unit.

[0049] Figure 2 An embodiment of a top counterweight arm mounted on a support rod comprising a mechanical pressure element for a ring spinning machine is shown, wherein the top counterweight arm 2 comprises a base portion 7 and a movable (e.g., openable and closable) bracket 8. In addition, the bracket 8 of the top counterweight arm 2 comprises three support elements 27, to each of which a top roller for two drafting units can be attached. In this embodiment, the support 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, wherein the housing 9 is designed as a hexagonal profile, the dimensions of which are designed in such a way that the housing 9 can be precisely inserted into the interior of the support rod 6.

[0050] In the open position, the spring unit 13 of the mechanical pressure element 12 does not push the extension 11 of the rocker mounted to the base part 7 of the top counterweight arm 2 with an initial spring force in the direction away from the support rod 6. Therefore, the extension 11 protrudes by a higher amount through the recess 14 of the housing 9 onto the spring unit 13 of the mechanical pressure element, as shown in FIG. Figure 3 Due to the torsional moment of inertia, when the top counterweight arm 2 is in its closed position, the extension 11 of the rocker is pushed outward (ie, in a direction away from the support rod 6), as shown in FIG. Figure 3b. By selecting the preload force and / or modifying the spring force characteristics of the spring unit 13, the extension 11 is now pushed back with a higher spring force in the direction away from the support rod 6, whereby this force is transmitted via the rocker to the bracket 8 of the top counterweight arm 2 and thus to the top roller. As a result, all top rollers arranged on the movable bracket 8 of the top counterweight arm 2 are loaded together by means of the mechanical pressure element and thus all top rollers are pressed against the lower roller with the same initial spring force, which is required to extend and stretch the fiber bundle.

[0051] Figures 4 to 5 A variant of a housing 9 for a mechanical pressure element arranged inside (not visible) is shown. The housing 9 comprises a recess 14 and is composed of two identical half-shells 15 which are releasably clamped together by a clip 10, as in Figure 5 When two identical half shells 15 are clamped together by the clip 10, the two half shells 15 form a stable guide rail 16 on each side, as in Figure 5 a) to stabilize the two half-shells 15 and prevent the two half-shells 15 from moving relative to each other.

[0052] Figure 6 A variant of the mechanical pressure element 12 in the housing 9 consisting of two identical half-shells 15 is shown. In this variant, a plate-shaped insert 18 is used to select the preload force and / or to modify the spring force characteristics of the C-shaped spring 17. The plate-shaped insert 18 is arranged, for example, on the C-shaped spring 17 and reduces the distance to the recess 14 and thus pushes the extension back in the closed position of the top counterweight arm in the direction away from the recess 14 and the support rod with a preload spring force that is biased according to the selected discrete amount of the plate-shaped insert 18.

[0053] Figures 7 and 8 Another variant of the mechanical pressure element 12 in the housing 9 is shown. In this variant, four bolts 21 are used to select the preload force and / or modify the spring force characteristics of the leaf spring 19. The bolts 21 of the adjustment device 20 are arranged below at one end of the leaf spring 19. By inserting or removing the bolts 21 at a predetermined position below the leaf spring 19, the preload spring force can thus be adjusted in stepped steps by reducing or enlarging the effective length of the leaf spring 19. In this variant, by inserting or removing the four bolts 21, the initial spring force can be selected from, for example, four stepped steps.

[0054] Figures 9 and 10Another variant of the mechanical pressure element 12 in the housing 9 is shown. In this variant, a plate-shaped insert 18 is used to select the preload force and / or to modify the spring force characteristics of the leaf spring 19. Furthermore, in this variant, the adjustment device 20 comprises an additional pusher 28, which is arranged between the leaf spring 19 and the plate-shaped insert 18 to reduce the distance to the recess 14. The plate-shaped insert 18 can be arranged on the pusher 28 and thus push the extension back in the closed position of the top counterweight arm in the direction away from the recess 14 and the support rod with a preload spring force that is biased according to a discrete amount selected by the plate-shaped insert 18.

[0055] Since the ring spinning machine may comprise several counterweight units 1, each counterweight unit 1 having at least two drafting units 3, the housings 9, which each contain a mechanical pressure element for easier guidance and positioning in the support rod 6, may be releasably connected to one another. In order that each of the housings 9 is correctly positioned in the support rod 6 in such a way that the recess of the respective housing 9 and the respective opening of the support rod 6 can be located one above the other, the housings 9 may be releasably connected to one another via a connecting element 22, such as Fig.11 Thus, each of the connecting elements 22 may include a connecting groove 23 and a connecting tongue 24, as shown in FIG. Fig.11 a and Fig.11 b. The connecting groove 23 and the connecting tongue 24 correspond to the tongue 26 and the groove 25 of the housing 9, which are Fig.11 c and Fig.11 d, and the connecting element 22 can be releasably attached to the housing 9 by a groove-tongue form fit.

[0056] Name List 1 Counterweight unit 15 Half shell 2 Top counterweight arm 16 Guide rail 3 Drafting unit 17 C-spring 4 Top Rollers 18 Element, Plate Insert 5 Lower roller 19 Leaf spring 6 Support rod 20 Adjustment device 7 Base part 21 (one or more) components, (one or more) bolts 8 Bracket 22 Connecting element 9 Shell 23 Connection groove 10 Clip 24 Connection tongue 11 extension 25 groove 12 Mechanical pressure element 26 Tongue 13 Spring unit 27 Support element 14 Recessed portion 28 Pushing member.

Claims

1. A mechanical pressure element (12) for a top counterweight arm (2) in a ring spinning machine, comprising: a) a spring unit (13), the spring unit (13) being used to provide spring force for the top counterweight arm (2); b) an adjustment device (20), the adjustment device (20) being used to adjust the spring force; Features c) The mechanical pressure element (12) is designed to receive a discrete number of elements (18, 21) for selecting discrete spring force values ​​of the spring unit (13).

2. The mechanical pressure element (12) according to claim 1, wherein: The spring unit (13) provides a spring force for adjusting the contact pressure of the top counterweight arm (2) on the top rollers (4) of the paired drafting units (3) of the ring spinning machine.

3. The mechanical pressure element (12) according to any one of the preceding claims, wherein: The mechanical pressure element (12) is arranged in a housing (9), which comprises a recess (14) so ​​that the spring unit (13) can be pressed onto it by the top counterweight arm (2) through the recess (14).

4. The mechanical pressure element (12) according to any one of the preceding claims, wherein The spring unit (13) is arranged in the housing (9) under a defined pretension.

5. The mechanical pressure element (12) according to any one of the preceding claims, wherein The adjustment device (20) comprises a space for receiving the discrete number of the elements (18, 21) for selecting the discrete spring force values.

6. The mechanical pressure element (12) according to claim 5, wherein: Each of the discrete number of the elements (18, 21) is individually fully insertable into or removable from the space for selecting the discrete spring force value.

7. The mechanical pressure element (12) according to claim 5 or 6, wherein: The adjustment device (20) comprises an additional pusher (28) arranged in mechanical contact with the springs (17, 19) of the spring unit (13).

8. The mechanical pressure element (12) according to any one of the preceding claims, wherein The element(s) is a spring pretensioning element (18, 21), in particular for selecting a preload force and / or modifying a spring force characteristic of the spring unit (13).

9. The mechanical pressure element (12) according to any one of the preceding claims, wherein The element(s) is a plate-like insert (18) arranged in contact with the spring unit (13) for reducing the distance to the recess (14) in discrete graduated steps defined by the thickness and / or the number of the plate-like inserts (18), in particular by selecting plate-like inserts (18) with equal and / or different thicknesses.

10. The mechanical pressure element (12) according to any one of the preceding claims, wherein The spring unit (13) is a C-shaped spring (17).

11. The mechanical pressure element (12) according to any one of the preceding claims 1 to 9, wherein: The spring unit (13) is a leaf spring (19).

12. The mechanical pressure element (12) according to any one of the preceding claims 1 to 8 and 10 to 11, wherein The element(s) is a spring modification element (21), such as a bolt, in particular for selecting a preload force and / or modifying a spring force characteristic of the spring unit (13).

13. The mechanical pressure element (12) according to claim 11 or 12, wherein: The element(s) is a bolt (21) arranged below the leaf spring (19) and preferably at one end of the leaf spring (19) for reducing the effective length of the leaf spring (19) by a preselected distance in discrete, stepped steps.

14. The mechanical pressure element (12) according to claim 13, wherein: The preselected distance for determining the preload force and / or modifying the spring force characteristic of the spring unit (13) can be adjusted by changing the number of the elements, in particular the bolts (21), and / or changing the size, in particular the diameter, of the elements, in particular the bolts (21), and / or by changing the distance between the elements, in particular the bolts (21) arranged below the leaf spring (19).

15. The mechanical pressure element (12) according to claim 13 or 14, wherein: The adjustment device (20) comprises an insertion space, in particular a semicircular insertion space, for receiving and retaining the bolt (21), in particular wherein the insertion space determines a preselected distance available for reducing the effective length of the leaf spring (19).

16. The mechanical pressure element (12) according to any one of the preceding claims, wherein The housing (9) is designed as a hexagonal profile that can be fitted into a hexagonal hollow support rod (6) for supporting the top counterweight arm (2) in the ring spinning machine.

17. The mechanical pressure element (12) according to any one of the preceding claims, wherein The housing (9) is composed of two half shells (15), in particular two identical half shells (15), which have a clip (10) for being clipped together and for prestressing the spring unit (13) therebetween.

18. The mechanical pressure element (12) according to any one of the preceding claims, wherein The housing (9) comprises a groove (25) and a tongue (26) for releasably connecting the housing (9) to a further, in particular identical, housing (9) in the longitudinal direction.

19. The mechanical pressure element (12) according to claim 18, wherein The housing (9) comprises a connecting element (22) for releasably connecting the housing (9) to another housing (9) in a longitudinal direction, wherein the connecting element (22) comprises a connecting groove (23) and a connecting tongue (26).

20. The mechanical pressure element (12) according to any one of the preceding claims, wherein At least one element (18, 21) is provided for the adjustment device (20) for adjusting the preload force and / or the spring force characteristic of the spring unit (13).

21. Ring spinning machine, comprising: At least one stretching unit (3), the at least one stretching unit (3) having an upper roller (4) and a lower roller (3) for stretching fiber roving; and a support rod (6), the support rod (6) being used to mount (one or more) the stretching units (3) in the ring spinning machine, and also comprising a top counterweight arm (2) for providing contact pressure between the upper roller (4) and the lower roller (5) of the stretching unit (3), wherein the support rod (6) accommodates a mechanical pressure element (12) according to any of the preceding claims.

22. The ring spinning machine according to claim 21 comprises a pair of said drafting units (3), and for each pair of said drafting units (3) further comprises a top counterweight arm (2), said one top counterweight arm (2) cooperating with one of said mechanical pressure elements (12) so that said mechanical pressure element (12) limits said contact pressure applied between said upper roller (4) and said lower roller (5) of said pair of drafting units (3) when said top counterweight arm (2) is in a closed state.

23. The ring spinning machine according to any one of claims 21 to 22, wherein: The contact pressure is selected to a desired value by selecting the number of elements (18, 21) of the spring unit (13) for prestressing or modifying the mechanical pressure element (12).

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