Discharge device for conducting electrical currents

Abstract

The invention relates to a discharge device (10) for discharging electric currents from a machine rotor part, which is designed in particular with a shaft, into a stator part of the machine, comprising a contact element (12), a holding device (13), and a spring device (14). The holding device can be connected to a stator part in an electrically conductive manner, and the contact element is largely made of carbon. The contact element is received on the holding device in an axially movable manner and is connected to same in an electrically conductive manner. A contact force can be applied to the contact element by means of the spring device in order to form an electrically conductive sliding contact (17) between a contact element sliding contact surface (15) provided in order to form the sliding contact and an axial shaft contact surface (16) of the shaft, wherein the contact element is disc-shaped, and the sliding contact surface has an at least circular ring shape and can be arranged coaxially relative to the shaft contact surface.

Description

[0001] Discharge device for dissipating electrical currents

[0002] The invention relates to a discharge device for discharging electrical currents from a rotor part of a machine, in particular one formed with a shaft, into a stator part of the machine, and to a machine with a discharge device comprising a contact element, a holding device and a spring device, wherein the holding device can be electrically connected to a stator part, wherein the contact element is predominantly made of carbon, wherein the contact element is axially displaceable on the holding device and electrically connected to it, wherein the contact element can be subjected to a contact force by means of the spring device to form an electrically conductive sliding contact between a sliding contact surface of the contact element provided for forming the sliding contact and an axial shaft contact surface of the shaft.

[0003] Discharge devices of the type mentioned above are known in various embodiments from the prior art. In particular, it is known to use carbon brushes for discharging low-frequency direct currents. These brushes are arranged radially around a shaft on a slip ring and are contacted with a stator via connecting leads. Due to their low electrical resistance, the carbon brushes, which are held in a retaining device or brush holder, allow for the direct dissipation of electrical currents and can thus prevent unwanted current flow through the shaft's bearing points, which could lead to surface damage to the bearing bodies or bearing rings due to localized welding.

[0004] The term "shaft" is used here as a synonym for "rotor part" or "shaft". Therefore, the term "shaft" encompasses all rotating machine parts through which current can be transferred to a stationary stator part or machine part of a machine.

[0005] Current-discharge devices are also regularly used in railway technology, where alternating currents or operating currents can flow away via wheel axles. For example, DE 10 2010 039 847 AI discloses a current-discharge device in which an electrically conductive end cap is mounted at an axial end of a shaft or wheel axle of a wheelset. This end cap can be contacted by a plurality of carbon brushes arranged axially relative to the shaft and held by brush holders. Each carbon brush is connected directly to a grounding cable via a wire, and a spring exerts a contact force on the sliding contact surfaces of the carbon brushes.

[0006] Similar measures for deriving currents are also necessary for electrical machines in general, for example for motor vehicles.

[0007] Currents are required. Continuously fluctuating alternating voltages or currents and high-frequency current pulses can occur in motor drive shafts or connected transmission shafts, as well as other functional components. These can damage the bearings of a rotor shaft or transmission shaft, which is why current discharge devices are regularly required. However, a disadvantage of known current discharge devices is that their design requires a comparatively large amount of installation space. While solutions are known that use fiber or wire braids instead of carbon brushes, these braids exhibit high contact resistance due to the very small contact surface of a sliding contact, and only low currents can be discharged.To create a large contact surface with the shaft, however, a plurality of carbon brushes are required, which, due to their arrangement, each require brush holders with a comparatively large installation space and a corresponding assembly effort.

[0008] The present invention therefore aims to propose a discharge device that has a low contact resistance and is easy to mount in a small installation space. This objective is achieved by a discharge device with the features of claim 1 and a machine with the features of claim 23.

[0009] The inventive conduction device for conducting electrical currents from a rotor part of a machine, in particular one formed with a shaft, into a stator part of the machine comprises a contact element, a holding device, and a spring device, wherein the holding device is electrically connectable to a stator part, wherein the contact element is predominantly made of carbon, wherein the contact element is axially displaceable and electrically connected to the holding device, wherein the contact element can be subjected to a contact force by means of the spring device to form an electrically conductive sliding contact between a sliding contact surface of the contact element provided for forming the sliding contact and an axial shaft contact surface of the shaft, wherein the contact element is disk-shaped, wherein the sliding contact surface is at least annular, preferably circular,is designed and can be arranged coaxially relative to the shaft contact surface, wherein the holding device has a base plate, wherein the spring element is arranged between the base plate and a contact surface side with the pressure side of the contact element facing away from the sliding contact surface.

[0010] The discharge device is designed for mounting on a rotating shaft or axle of a machine. It is intended that the discharge device be positioned at an axial end of the shaft and that the electrically conductive sliding contact be formed by contacting the axial shaft contact surface at the axial end of the shaft or at an end face of the shaft with the contact element. The spring mechanism then applies a contact force to the contact element, acting axially in the direction of the shaft's axis of rotation, so that the contact element's sliding contact surface is pressed against the shaft contact surface. Since the contact element is disc-shaped, or in the form of a disk or plate, space can be saved compared to a conventional grinding wheel, as the contact element is then comparatively short and thin with respect to its axial extent.The disc or plate shape of the contact element makes it possible to design the contact element with at least an annular sliding contact surface, which can then be arranged coaxially relative to the shaft contact surface. The circular shape of the sliding contact surface results from a rotational movement of the shaft or shaft contact surface. This allows for a comparatively large sliding contact surface, enabling the formation of a sliding contact with low contact resistance. However, the disc or plate shape of the contact element can also be chosen such that a contour of the contact element extends beyond the sliding contact surface. The contact element can therefore also be polygonal and still have a circular sliding contact surface.Since abrasive wear of the sliding contact is reduced relative to the large sliding contact area, the contact element can also be designed in a disc-shaped or thin form without wearing out significantly sooner than a contact element with a small sliding contact area and a large length, as known from the prior art. Furthermore, it is no longer necessary to mount multiple contact elements on the shaft to achieve low contact resistance, since a single disc-shaped contact element can already form a sufficiently large sliding contact. The discharge device thus requires little installation space and can also be easily mounted.

[0011] The holding device according to the invention has a base plate, wherein the spring element is arranged between the base plate and a contact surface side of the contact element, the pressure side facing away from the sliding contact surface. The spring element is thus simply arranged between the base plate and the contact element. In a particularly simple embodiment of the discharge device, it can then consist of only three components that can be plugged into one another. This makes assembly of the discharge device particularly easy. If the spring device or spring element is a particularly flat spring, such as a disc spring, the installation space required for the discharge device can be reduced even further. The base plate can be easily attached to a stator part of a machine by means of a screw, plug, or adhesive connection.An electrically conductive connection of the base plate can be formed via this connection with the stator part or via a direct connection of a grounding cable to the base plate.

[0012] The outer diameter or maximum outer dimension of the disc-shaped contact element can be a multiple of the contact element's thickness. The contact element can be designed with an outer dimension to thickness ratio of 2:1, 3:1, 4:1, 5:1, or 10:1.

[0013] For example, the sliding contact surface, or an end face of the contact element, can be dimensioned so large relative to the axial end of the shaft that its radial dimensions exceed the diameter of the shaft at the axial end. Furthermore, the sliding contact surface can also be shaped like a full circle. The contact element can also be designed so that its radial extent approximates or corresponds to the diameter of the axial end of the shaft, as this allows for a particularly large sliding contact area.

[0014] The contact element can be formed in one piece and consist predominantly of carbon. For example, the contact element can be a carbon component formed by pressing and firing or sintering. The contact element can also be made of graphite,

[0015] The holding device consists of carbon black, carbon fibers, or a mixture of these materials, as well as particles of the metals iron, nickel, manganese, copper, zinc, silver, aluminum, and / or chromium, and a binder or binder phase. The holding device can be made of metal, preferably steel, aluminum, copper, or an alloy of these materials. The holding device can then be easily and cost-effectively manufactured in large quantities, for example, by injection molding or simple machining of semi-finished products made from these materials. The holding device can be directly attached to a stator part or a housing part of a

[0016] The machine can be securely and electrically connected, for example, by screwing it in place. A grounding cable can also be easily attached or mounted to the mounting device. The mounting device can be designed as a single piece or in multiple parts. The mounting device and the contact element together can form an anti-rotation device for the contact element. This allows the mounting device to be firmly attached to the stator part, and the contact element can then also be firmly positioned relative to a rotating shaft on the mounting device and made contact with the shaft. In particular, due to the annular shape and coaxial arrangement of the sliding contact surface, the contact element could otherwise follow the rotation of the shaft, resulting in no sliding contact with the shaft.The anti-rotation device can be easily formed by a positive locking connection of the contact element to the holding device, which allows axial movement of the contact element on the holding device and prevents radial movement of the contact element relative to the holding device.

[0017] The spring assembly can comprise a spring element, preferably a coil spring, compression spring, disc spring, leaf spring, conical spring, ring spring, or diaphragm spring, wherein the spring element can be arranged coaxially relative to the sliding contact surface or an axis of rotation of the shaft. This makes it possible to exert a contact force or spring force on the contact element by means of the spring assembly, acting in the direction of the axis of rotation of the shaft, and thus generate the contact force.

[0018] The contact element can be formed from at least two layers with different material mixtures. The contact element can therefore have at least two layers that exhibit different physical properties and thus different functionalities.

[0019] The layers can be arranged successively in the axial direction, with the sliding contact surface consisting of a sliding layer with a copper content of < 60% by mass and the contact surface consisting of a bonding layer with a copper content of > 80% by mass, preferably with an expansion layer formed between the sliding layer and the bonding layer. For example, the bonding layer can be solderable and weldable with a copper content of 90 to 99% by mass, with additions of tin or zinc up to 9% by mass, and a graphite content of a maximum of 3% by mass. This makes the bonding layer particularly wettable with lead-free solders and also weldable. In addition, the bonding layer exhibits a high flexural strength of over 100 MPa, which gives it high resistance to tensile, shear, and compressive stresses.The sliding layer can also have a copper content of less than 50% by mass or even be completely copper-free. This results in good sliding properties with low wear, and therefore a long service life and chemical stability.

[0020] Structurally, the different layers can also differ in their isotropy / anisotropy. The bonding layer can be isotropic, while the sliding layer can be either isotropic or anisotropic. The lubricating effect of the graphite used in the sliding layer can then be optimally utilized, particularly by orienting the graphite preferentially parallel to the sliding plane. The thermal expansion behavior of the sliding layer can be controlled by its isotropy / anisotropy. The optional expansion layer can serve to compensate for differing coefficients of thermal expansion between the sliding layer and the bonding layer.

[0021] The contact element can be formed by sintering, with a contoured transition zone between the layers. When the contact element is formed by sintering, the individual layers can be easily formed using appropriately selected powder mixtures. Furthermore, it can be provided that a contour is formed in the transition zone between the individual layers, so that the layers interlock in the axial direction. The contour can be formed by first compacting a first layer in a mold with a suitably contoured die, and then filling and compacting the second layer as a powder mixture.

[0022] The holding device can have at least one guide element arrangement extending axially, along which the contact element is axially displaceable. The guide element arrangement can have a profile that is continuous in the axial direction or along a rotational axis of the shaft, thus ensuring the axial displaceability of the contact element. The length of the guide element arrangement in the axial direction can always be dimensioned such that the contact element can be partially or completely worn away by abrasive wear without the contact element being able to detach from the guide element arrangement during axial displacement by means of the spring mechanism. The contact element can have a guide contour on its circumference that is inserted into the guide element arrangement.The guide element arrangement can therefore partially or completely encompass the contact element around its circumference. The circumference or guide contour of the contact element can be polygonal or partially or completely circular. Notches or grooves can also be formed on the circumference in the axial direction, into which the guide element arrangement engages. In principle, it is possible to design the contact element so that it is held on the base plate solely by the guide element arrangement around its circumference. The contact element can also have a guide recess into which the guide element arrangement or a guide pin of the shaft can engage. The guide recess can be formed along a longitudinal axis of the contact element in the form of a bore, so that the contact element then forms the annular sliding contact surface.The guide recess can be a through-hole in the contact element or a blind-hole recess in the contact element. Optionally or alternatively, the guide recess can be designed as a central bore in the contact element, allowing the contact element to be mounted onto a guide pin or a stepped diameter of the shaft. The shaft can thus serve to radially secure the contact element.

[0023] The guide recess and the guide element assembly can have matching cross-sections. This makes it possible to guide the contact element and thus allow axial movement. Depending on the selected cross-sectional shape, the matching cross-sections can also provide anti-rotation protection. For example, the cross-section can be circular, square, rectangular, or polygonal. Instead of a round bore, a polygonal guide recess with a matching guide pin can be provided, together forming an anti-rotation device. A clearance fit can also be formed between the guide recess and the guide element assembly.

[0024] The guide element arrangement can be positioned coaxially with the sliding contact surface. This ensures that the contact element is always centered relative to the shaft's axis of rotation at the axial end of the shaft. Consequently, the centroid of the sliding contact surface can always coincide with the centroid of the shaft contact surface, with both centroids potentially lying on the shaft's axis of rotation. The contact element can also be rotationally symmetrical.

[0025] The guide element arrangement can comprise at least one guide element, preferably a plurality of guide elements. A guide element can, for example, be a simple pin-shaped extension of the holding device. Furthermore, the guide element can be a

[0026] The guide element can be a screw of the holding device. It can also be a polygonal extension in cross-section and, in principle, any cross-sectional shape. Furthermore, it is possible to use multiple guide elements with the cross-sectional shapes described above, if this appears appropriate. The guide element can be integrally formed on a base plate of the holding device or inserted into the base plate. In a simple embodiment, the guide element can be a pin that is simply inserted into a bore in the base plate. Likewise, a pin-shaped guide element can be integrally formed on the base plate in the form of an extension. The base plate can also have a central bore into which a screw is inserted or screwed.

[0027] If the holding device has an integrated guide element, it can also be manufactured as a single piece. The holding device can be easily produced using an injection molding process or by machining a semi-finished product. An inner surface of the guide recess can be electrically conductively contacted with an outer surface of the guide element. This allows an electric current to be transferred from the contact element to the holding device with low contact resistance. If the guide recess is, for example, a bore, the inner surface of the bore can be contacted with an outer surface of a pin or stud as the guide element. The inner and outer surfaces, or rather their respective diameters, can form a clearance fit that always ensures low contact resistance.An axial displacement can be ensured solely by the carbon of the contact element and an advantageously designed friction pairing of the inner and outer surfaces.

[0028] The guide element can be arranged concentrically relative to the shaft contact surface on the holding device. Consequently, the guide element can always also be arranged centrally to the shaft contact surface. Additionally or alternatively, the guide element can be arranged eccentrically relative to the shaft contact surface on the holding device. In that case, however, there should be a plurality of guide elements arranged eccentrically to the shaft contact surface on the holding device, such that the guide elements are positioned relative to a

[0029] The rotation axes of the shaft are always evenly spaced, for example equidistantly spaced from each other.

[0030] The sliding contact surface can have at least one groove extending axially. Furthermore, multiple grooves can be formed in the sliding contact surface, extending radially outwards from a central point, for example. The groove can have a depth corresponding to the maximum wear depth of the contact element. Oil on the sliding contact or particles of abrasion can be collected by means of the groove and carried away radially within it. The groove can also be spirally shaped or arranged like a passer relative to a center point of the sliding contact surface.

[0031] Particularly efficient electrical current dissipation is achieved when the contact element is connected to the holding device via at least one electrically conductive wire or a flexible metal strip. The wire can be arranged within the contact element during its manufacture or attached to it, for example, by soldering or gluing. Preferably, the contact element also comprises a plurality of wires attached to its circumference and equidistant from one another. The wire can also be easily attached to the holding device by means of clamps, screws, or soldering. Using a wire can further reduce contact resistance. It is also possible to connect the wire directly to a stator part of the machine. The machine according to the invention includes a current-dissipation device according to the invention.Advantageous embodiments of a machine result from the features of the dependent claims relating back to device claim 1.

[0032] Advantageous embodiments of the invention will be explained in more detail below with reference to the accompanying drawings.

[0033] They show:

[0034] Fig. 1: a sectional view of a first embodiment of a

[0035] Discharge device on a shaft;

[0036] Fig. 2: a top view of a contact element after the first

[0037] Design of the discharge device;

[0038] Fig. 3 : a side view of the contact element from Fig. 2 ;

[0039] Fig. 4: a top view of a base plate according to the first embodiment of the discharge device;

[0040] Fig. 5 : a side view of the base plate from Fig. 4;

[0041] Fig. 6: a top view of a second embodiment of a

[0042] Contact element;

[0043] Fig. 7: a side view of the contact element from Fig. 6;

[0044] Fig. 8: a top view of a second embodiment of a

[0045] Base plate;

[0046] Fig. 9 : a side view of the base plate from Fig. 8;

[0047] Fig. 10: a top view of a third embodiment of a

[0048] Contact element;

[0049] Fig. 11 : a side view of the contact element from Fig. 10 ;

[0050] Fig. 12: a top view of a fourth embodiment of a

[0051] Contact element; Fig. 13: a side view of the contact element from Fig. 12;

[0052] Fig. 14: a top view of a fifth embodiment of a

[0053] Contact element;

[0054] Fig. 15: a side view of the contact element from Fig. 14; Fig. 16: a top view of a sixth embodiment of a

[0055] Contact element;

[0056] Fig. 17: a side view of the contact element from Fig. 16;

[0057] Fig. 18: a top view of a seventh embodiment of a

[0058] Contact element;

[0059] Fig. 19 : a side view of the contact element from Fig. 18 ;

[0060] Fig. 20: a top view of an eighth embodiment of a

[0061] Contact element;

[0062] Fig. 21 : a side view of the contact element from Fig. 20 ;

[0063] Fig. 22: a top view of a ninth embodiment of a

[0064] Contact element;

[0065] Fig. 23 : a side view of the contact element from Fig. 22 ;

[0066] Fig. 24: a top view of a tenth embodiment of a

[0067] Contact element;

[0068] Fig. 25: a side view of the contact element from Fig. 24; Fig. 26: a second embodiment of a discharge device in a sectional view on a shaft;

[0069] Fig. 27: a third embodiment of a discharge device in a sectional view on a shaft; Fig. 28: a fourth embodiment of a discharge device in a sectional view on a shaft;

[0070] Fig. 29 shows a fifth embodiment of a discharge device in a sectional view on a shaft; Fig. 30 shows a sixth embodiment of a discharge device in a sectional view on a shaft.

[0071] Fig. 1 shows a cross-sectional view of a discharge device 10 on a shaft 11. The discharge device 10 consists of a contact element 12, a holding device 13, and a spring assembly 14. The contact element 12 is predominantly made of carbon, is annular in shape, and has a sliding contact surface 15 that bears against an end face or axial shaft contact surface 16 of the shaft 11, thereby forming an electrically conductive sliding contact 17. The spring assembly 14 is formed by a disc spring 18, which bears against a pressure side 19 of the contact element 12 and exerts a contact force on the contact element 12 in the axial direction relative to an axis of rotation 20 of the shaft 11. The holding device 13 consists of a base plate 21 with an integrally formed guide element 22, which is circular in shape.Due to its annular shape, the contact element 12 has a guide recess 23 with which the guide element 22 is designed to align such that the contact element 12 is axially displaceable relative to the axis of rotation 20 on the holding device 13. The disc spring 18 is mounted on the guide element 22 and bears against the base plate 21. The base plate 21 and the guide element 22 are formed in one piece from a single metal and are attached to a stationary component of an electric machine, which is not shown in detail here. Overall, this allows for a good electrically conductive connection with low contact resistance from the shaft 11 to the holding device 13 via the contact element 12. The discharge device 10 can also be mounted on an electric machine particularly quickly and easily.

[0072] Figures 2 and 3 show a contact element 24, which is annular and rotationally symmetrical. The contact element 24 forms a sliding contact surface on one end face 25.

[0073] Figures 4 and 5 show a holding device 27, which is formed in one piece and has a rectangular base plate 28 with a guide element 29 molded into it, which is pin- or bolt-shaped. The contact element from Figure 2 can be attached to an outer surface 30 of the guide element 29.

[0074] A view of Figures 6 to 9 shows a contact element 31, which is disc-shaped and has a central bore 32 forming a guide recess 33. A holding device 34 has a guide pin 37 on a base plate 35, which is aligned with the bore 32. Furthermore, square guide pins 38 are formed on the base plate 35, which together with the guide pin 37 form a guide element arrangement 39. The guide pins 38 can engage in grooves 40 on a circumference 41 of the contact element 31, thus forming an anti-rotation device 42 for the contact element 32 on the holding device 34.

[0075] Figures 10 and 11 show a contact element 43, which, unlike the contact element from Figure 6, has a recess 44. The recess 44 is formed in a sliding contact surface 45 and serves to receive the screw head of a screw (not shown in detail here), which can be used to fasten and guide the contact element 43 to a holding device or base plate.

[0076] Figures 12 and 13 show a contact element 46 with three guide recesses 47, which are formed eccentrically and equidistantly from each other in the contact element 46 relative to a rotation axis 48 of a shaft not shown here.

[0077] Figures 14 to 15 show a contact element 49 with a slot-shaped guide recess 50.

[0078] Figures 16 and 17 show a contact element 5 1 with a polygon-shaped guide recess.

[0079] Figures 18 and 19 show a contact element 53 with strands 55 protruding from a circumference 54 of the contact element 53 (shown here only partially) and connectable to a holding device (not shown here). A central guide recess 56 and an equidistant arrangement of the strands 55 ensure that the contact element 53 is centered on the holding device.

[0080] Figures 20 and 21 show a contact element 57 which, unlike the contact element from Figure 2, has grooves 60 extending radially in a sliding contact surface 58, relative to a rotational axis 59 of a shaft (not shown here). A radial depth T of the grooves corresponds to a wear length of the contact element 57.

[0081] Figures 22 to 23 show a contact element 6 1 which, in contrast to the contact element from Figure 20, has a comparatively small guide recess 62.

[0082] Figures 24 and 25 show a contact element 63 which, unlike the contact element from Figure 22, has grooves 64 that run relative to an axis of rotation 65 of a shaft not shown here in the manner of a passant and thus do not intersect the axis of rotation 65, but are nevertheless arranged in a radial direction.

[0083] Fig. 26 shows a discharge device 66 on a shaft 67, which has a central recess 69 in an end face 68. The discharge device 66 is formed from a holding device 70 with a base plate 71 and a screw 72 attached thereto as a guide element 73, wherein a contact element 74 of the discharge device 66 has a recess 75 that serves to receive a screw head 76 of the screw 72. The recess 69 is also dimensioned so that the screw head 76 cannot come into contact with the end face 68 if the contact element 74 wears down. A disc spring 77 is arranged between the contact element 74 and the base plate 71 to generate a contact force. Fig. 27 shows a discharge device 78 with a contact element 79 which forms a conical sliding contact surface 80. A shaft 8 1 also forms a conical shaft contact surface 82, which is adapted to the sliding contact surface 80.This allows for simple centering of the contact element 79 on the shaft 81. Fig. 28 shows a discharge device 83 on a shaft 84, which has a pin 85 on an end face 86. The discharge device 83 comprises an annular contact element 87, which is mounted on the pin 85, a holding device 88 with a base plate 89, a disc spring 90, and wires 91 that protrude from the contact element 87 on a circumference 92 and are attached to the base plate 89. This ensures a particularly good electrically conductive connection between the contact element 87 and the base plate 89.

[0084] Fig. 29 shows a discharge device 93 which, unlike the discharge device from Fig. 1, has a contact element 94 formed with a sliding layer 95 and a bonding layer 96. The sliding layer 95 has a copper content of < 60% by mass, and the bonding layer 96 has a copper content of > 80% by mass. A transition zone 97 between the sliding layer 95 and the bonding layer 96 is contoured. The contact element 94 is manufactured by sintering various powder mixtures.

[0085] Fig. 30 shows a discharge device 98 which, unlike the discharge device from Fig. 29, has a contact element 99 with a sliding layer 100 and a bonding layer 101, with an expansion layer 102 formed between them. The expansion layer 102 compensates for the different coefficients of thermal expansion of the sliding layer 100 and the bonding layer 101.

Claims

Patent claims Conducting device (10, 66, 78, 83, 93, 98) for conducting electrical currents from a rotor part of a machine, in particular one having a shaft (11, 67, 81, 84), into a stator part of the machine, comprising a contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99), a holding device (13, 27, 34, 70, 88) and a spring device (14), wherein the holding device is electrically connectable to a stator part, wherein the contact element is predominantly made of carbon, wherein the contact element is axially displaceable on the holding device and electrically connected to it, wherein the contact element is moved by means of the spring device to form an electrically conductive sliding contact (17) between a The sliding contact surface (15, 26, 45, 58, 80) of the contact element and an axial shaft contact surface (16, 82) of the shaft can be subjected to a contact force for the formation of the sliding contact. thereby kenne nn zeil hn et , that the contact element is designed in a disc shape, wherein the sliding contact surface is at least annular in shape and can be arranged coaxially relative to the shaft contact surface, wherein the holding device has a base plate (21, 28, 35, 71, 89), wherein the spring element is arranged between the base plate and a pressure side (19) of the contact element facing away from a contact surface side with the sliding contact surface.

2. Drainage device according to claim 1, thereby kenne nn zeil hn et , that the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) is formed in one piece and consists predominantly of carbon.

3. Discharge device according to claim 1 or 2, thereby kenne nn zeil hn et , that the holding device (13, 27, 34, 70, 88) is made of metal, preferably of steel, aluminium, copper or an alloy of these materials.

4. Discharge device according to one of the preceding claims, thereby kenne nn zeil hn et , that the holding device (13, 27, 34, 70, 88) and the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) together form an anti-rotation device (42) for the contact element.

5. Discharge device according to one of the preceding claims, thereby kenne nn zeil hn et , that the spring device (14) comprises a spring element, preferably a coil spring, compression spring, disc spring (18, 77, 90), leaf spring, conical spring, ring spring or diaphragm spring, wherein the spring element is arranged coaxially relative to the sliding contact surface (15, 26, 45, 58, 80).

6. Discharge device according to one of the preceding claims, thereby kenne nn zeil hn et , that the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) consists of at least two layers (95, 96, 100, 101, 102) is formed with different material mixtures.

7. Discharge device according to claim 6, thereby kenne nn zeil hn et , that the layers (95, 96, 100, 101, 102) are formed successively in the axial direction, wherein the sliding contact surface (15, 26, 45, 58, 80) is formed by a sliding layer (95, 100) with a copper content of < 60 mass percent and the pressure side (19) by a bonding layer (96, 101) with a copper content of > 80 mass percent, wherein preferably an expansion layer (102) is formed between the sliding layer and the bonding layer.

8. Discharge device according to claim 6 or 7, thereby kenne nn zeil hn et , that the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) is formed by sintering with a contoured transition zone (97) between the layers (95, 96, 100, 101, 102).

9. Discharge device according to one of the preceding claims, thereby kenne nn zeil hn et , that the holding device (13, 27, 34, 70, 88) has at least one guide element arrangement (39) which extends in the axial direction and on which the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) is axially displaceable.

10. Drainage device according to claim 9, thereby kenne nn zeil hn et , that the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) has a guide con- on its circumference (41, 54, 92) has a tur which is inserted into the guide element arrangement (39).

11. Discharge device according to claim 9 or 10, thereby marked, that the contact element (12, 24, 31, 43, 46, 49, 51, 53, 57, 61, 63, 74, 79, 87, 94, 99) has a guide recess (23, 33, 47, 50, 52, 56, 62) into which the guide element arrangement (39) or a guide pin (85) of the shaft (11, 67, 81, 84) engages. Drainage device according to claim 11, thereby kenne nn zeil hn et , that the guide recess (23, 33, 47, 50, 52, 56, 62) and the guide element arrangement (39) have matching cross-sections. Drainage device according to one of claims 9 to 12, thereby kenne nn zeil hn et , that the guide element arrangement (39) is arranged coaxially to the sliding contact surface (15, 26, 45, 58, 80). Drainage device according to one of claims 9 to 13, thereby kennz eic hn et , that the guide element arrangement (39) has at least one guide element (22, 29, 36, 73), preferably a plurality of guide elements.

15. Drainage device according to claim 14, thereby kenne nn zeil hn et , that the guide element (22, 29, 36, 73) is attached to a base plate (21, 28, 35, 71, 89) of the holding device (13, 27, 34, 70, 88) is molded or inserted into the base plate.

16. Discharge device according to claim 14 or 15, thereby kenne nn zeil hn et , that the holding device (13, 27, 34, 70, 88) is formed in one piece.

17. Discharge device according to one of claims 14 to 16, thereby kenne nn zeil hn et , that an inner surface of the guide recess (23, 33, 47, 50, 52, 56, 62) is electrically conductively contacted with an outer surface (30) of the guide element (22, 29, 36, 73).

18. Discharge device according to one of claims 14 to 17, thereby kenne nn zeil hn et , that the guide element (22, 29, 36, 73) is arranged concentrically relative to the shaft contact surface (16, 82) on the holding device (13, 27, 34, 70, 88).

19. Discharge device according to one of claims 14 to 18, thereby kenne nn zeil hn et , that the guide element is arranged eccentrically relative to the shaft contact surface on the holding device.

20. Discharge device according to one of the preceding claims, thereby kenne nn zeil hn et , that at least one radially extending groove (60, 64) is formed in the grinding contact surface (58).

21. Discharge device according to one of the preceding claims, characterized by , that the contact element (53, 87) is connected to the holding device (88) via at least one electrically conductive wire (55, 91) or a flexible metal flat strip. Discharge device according to one of the preceding claims, characterized by , that the sliding contact surface (80) is conical, preferably cone-shaped, for contact with a correspondingly shaped shaft contact surface (82).

23. Machine with a discharge device (10, 66, 78, 83, 93, 98) according to one of the preceding claims.