Contact disc of a ground contact, tool for manufacturing the contact disc and method for manufacturing the contact disc

Abstract

The invention relates to a contact disc (1) of a ground contact of a rail-bound vehicle, wherein the contact disc (1) has a contact surface (2) for sliding contact with a brush body, wherein the contact surface (2) has a profile (3) and the profile (3) is embossed by a tool (9).

Description

[0001] 27.08.2025 XG / East

[0002] Our reference: STK231WO

[0003] Stemmann-Technik GmbH

[0004] Niedersachsenstraße 2, D-48465 Schüttorf

[0005] Grinding element of an earthing contact, tool for manufacturing the grinding element and method for manufacturing the grinding element

[0006] The invention relates to a grinding element of an earthing contact of a rail-bound vehicle according to the features in the preamble of claim 1, a tool for manufacturing such a grinding element according to the features of claim 10, and a method for manufacturing the grinding element according to the features of claim 15.

[0007] Rail vehicles have grounding contacts for returning operating or signal current and for vehicle grounding. Grounding is achieved via a wheel and the rail. A movable friction element rotates with a wheelset axle and, with the aid of a spring, presses against a carbon brush that is stationary. This principle of fixed and rotating parts can also be used in reverse. In either case, a sliding contact occurs between a more wear-resistant friction element and a brush body. It is known to use carbon brushes with a circular contact surface as the brush body, which are soldered or clamped into a cover. The rotating movement of the friction element against a stationary round carbon brush can cause temporary squeaking noises. These noises do not affect the function of the grounding contact, but they do have a negative impact on the vehicle's noise characteristics.The squeaking noise is sometimes perceived as unpleasant by people both inside and outside the rail vehicle. This squeaking is caused by the so-called stick-slip effect on the sliding elements. Efforts to prevent this squeaking have been underway for years. The stick-slip effect can occur when static friction is significantly greater than kinetic friction. It is known that the squeaking noises are sometimes influenced by the season or humidity. Investigating the cause is complex. Numerous approaches exist to solving the problem, such as modifying the surfaces of the friction partners, for example, by milling grooves into the sliding element. However, the annoying squeaking noises often persist despite these measures.

[0008] The invention aims to provide an abrasive body with which squeaking can be largely and, in particular, completely avoided. Furthermore, a method for manufacturing a suitable abrasive body and a suitable tool for its manufacture are to be presented.

[0009] These tasks are solved by a grinding body having the features of claim 1, by a tool according to claim 10 and a manufacturing method according to claim 15.

[0010] The invention relates to a grounding contact of a rail-bound vehicle with a grinding element. According to the invention, the grinding element has a contact surface with a profile. The contact surface is designed and configured for axial contact with a sliding partner. However, the profile is not milled, but rather embossed by a tool, so that an embossed structure is formed in the contact surface. The crucial difference is that milling involves material removal, whereas according to the invention, no material is removed, but only displaced. Surprisingly, the embossed profile has completely different properties than a milled profile. Comparative tests have shown that no squeaking occurred with an embossed profile compared to grinding elements with a milled groove. The tests were carried out with commercially available grinding elements.The examined grinding wheels were made of bronze, which was produced using the continuous casting process.

[0011] Bronze materials are particularly well-suited for manufacturing the grinding wheels according to the invention, as they can be more easily deformed by stamping using a tool than steel grinding wheels. According to the invention, the grinding wheels preferably consist of metal, in particular bronze, and most preferably CuSn6. The grinding wheels can be manufactured, in particular, from continuous casting GC-CuSn6 according to DIN 17662. GC-CuSn6 can have a nominal hardness of approximately 76 HB. Hot-rolled CuSn6 according to standard EN 1652 / 1997 is also suitable. It can have a hardness of approximately 114 HB. The hardness of continuous casting can also be higher, e.g., approximately 85 HB. However, when stamping, it must also be taken into account that the forming process becomes significantly more difficult with increasing hardness if the stamping is applied over a large area or to a deep depth. Therefore, the stamping may need to be carried out in several steps or at least in such a way that undesirable deformations of the workpiece do not occur.

[0012] Tests have shown that a groove-shaped depression yields particularly good results. Therefore, the tool for embossing the profile has at least one embossing ridge. With a circular contact surface, the groove-shaped depression should preferably extend substantially over the entire diameter of the contact surface, so that during the sliding movement of the contacting partners, the groove-shaped depression always lies in the path of motion of the sliding partners.

[0013] Particularly advantageous are several parallel, groove-shaped depressions. Tests were conducted with such profiled grinding wheels, and no squeaking occurred during these tests. One reason for this effect could be that the profiles do not have sharp edges at the transition from the groove-shaped depression to the contact surface. Furthermore, the effect could be attributed to the fact that material displaced from the groove-shaped depressions forms an embossed ridge adjacent to the depressions. This embossed ridge is rounded by the material flow.

[0014] Preferably, the grooves should have a depth in the range of 0.1 to 0.6 mm. These depths have yielded very good results. Regarding the center-to-center spacing of the grooves, a range of 2 to 12 mm, preferably 2 to 8 mm, and particularly preferably 3 to 6 mm is considered advantageous. Tests were carried out with groove spacings of 4.5 to 5 mm, at which no stick-slip effect was observed.

[0015] The embossed, groove-shaped depressions had a width of 0.5 to 1.5 mm, preferably 0.8 to 1.2 mm, and in particular widths of approximately 1 mm. Including the rounded transition areas to the essentially flat contact surface, the width of the groove-shaped depressions increases by approximately 20%. With an initial width of 1 mm, the width of the depression relative to the contact surface is therefore approximately 1.2 mm. The groove-shaped depressions had a straight profile.

[0016] The grounding contact according to the invention can be produced, in particular, with a tool having at least one embossing ridge, wherein the embossing ridge tapers from its base to its tip. This allows the embossing ridge to penetrate the material of the grinding body more easily and to create sufficiently wide depressions with increasing penetration depth. Lateral material displacement is desirable. As explained above, the depth should be in the range of 0.1 to 0.5 mm, with aperture widths of approximately 0.5 to 1.5 mm. Due to the shape of the embossing ridge, the width and depth of the depressions are also not constant in cross-section.

[0017] Several groove-shaped indentations can be produced in successive embossing steps. Preferably, the tool has several parallel embossing sections to prevent deformation of the contact surface due to uneven loading. In particular, the tool for producing the profiled contact surface is large enough that the contact surface can be profiled in a single stroke of the embossing tool.

[0018] The embossing ridge is preferably triangular, with its sides arranged at an angle of 80 to 100°, particularly 90°, to each other. The embossing ridges can follow one another directly, so that the tool has a zigzag profile on its embossing side. Such an embossing profile is cost-effective to manufacture. It is by no means necessary for the individual embossing ridges to penetrate the material of the contact surface to their entire height. A depth of just 0.1 mm is sufficient to form effective groove-shaped indentations.

[0019] Tests have shown that the stick-slip effect can be avoided with parallel, groove-shaped depressions. Similarly, it has also been found that the stick-slip effect is avoided when groove-shaped depressions intersect. Accordingly, a tool can be used in a process for manufacturing the grinding wheel that, in a first embossing step, produces depressions with a first orientation, and in a second embossing step, produces depressions with a second orientation, the orientations differing from each other and, in particular, intersecting at a 90° angle. It is expected that angles other than 90°, or a diamond pattern bounded by the depressions, will also effectively prevent squeaking. Depressions with other differing orientations can also be provided, e.g., for a triangular pattern.

[0020] Comparative tests of grinding wheels with exclusively non-intersecting parallel groove-shaped depressions and grinding wheels with multiple parallel groove-shaped depressions intersecting at 90° angles showed that after 100,000 revolutions, wear was significantly lower when the groove-shaped depressions intersected. No squeaking occurred in either case; however, the differences in wear of the friction partner were so pronounced that intersecting groove-shaped depressions are clearly preferable for wear optimization. The inventive method is particularly suitable for embossing grinding wheels that possess high conductivity and are easily deformable. Therefore, cast or rolled copper alloys are especially suitable.

[0021] The tool used to carry out the process preferably has a sharp point or edges that, due to their angular orientation, can penetrate sufficiently deeply into the surface without bending the entire grinding contact. The embossing is produced exclusively by material displacement. Sharp edges in the border region of the groove-shaped depressions should be avoided. Depending on the material selection and the geometry of the tool and the workpiece, sharp edges in the border region of the depressions can be avoided by carrying material along in the embossing direction, so that the flanks of the depression transition into a flow curve that represents a gently rounded transition to the contact surface. In particular, the depressions have walls that are at an angle to each other greater than 45°, for example, 90°. Smaller angles facilitate the embossing because the tool can penetrate more easily. Larger angles result in wider depressions.A 90° angle yielded good results. The tool is made primarily of steel, specifically a hardenable steel, with at least the tips of the tool penetrating the contact surface being hardened.

[0022] The term "embossing" as used in the invention refers to the displacement of material, not its removal. The direction of displacement is determined by the shape and movement of the tool during embossing. Embossing also includes the creation of multiple point-shaped indentations, as in dot peening or vibro-peening. These indentations can be created using very low force in these processes. If the point-shaped indentations are placed close together and / or overlap, linear profiles can be produced. The point-shaped indentations can be created using a carbide tip.

[0023] The term "marking" as used in the invention also includes scribing, in which a diamond or carbide tip is pressed into the workpiece surface and drawn through the material like a scribing needle. The force applied to the tool is minimal. The difference to, for example, needle marking, is that the tool is moved parallel to the contact surface and not essentially perpendicular to it.

[0024] The groove-shaped depressions typically have a straight, linear path. However, they can also have an arc-shaped or serpentine path. Grooves with differing paths, such as straight and odd paths, can be combined.

[0025] The subdivision of the contact surface into smaller contact area units by means of profiling effectively prevents the stick-slip effect on the more wear-resistant component of the friction pair by plastically deforming the contact surface. The advantages of the invention are demonstrably particularly evident in grounding contacts for rail vehicles. The brush bodies with embossed contact surfaces can also be used in other applications where squeaking noises need to be avoided.

[0026] The abrasive body and the brush body are in contact via a force acting axially along an axis of rotation. The axis of rotation is perpendicular to the contact surfaces of the abrasive body and the brush body. At least one of the contact surfaces is preferably circular. The embossing operations described above refer to a flat contact surface that is not curved.

[0027] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. The drawings show:

[0028] Figure 1 shows a contact surface of an abrasive body with a profile in a first embodiment;

[0029] Figure 2 shows a contact surface of an abrasive body with a second profile;

[0030] Figure 3 shows a perspective view of a tool for embossing a profile;

[0031] Figure 4 shows a detail of a profile in a contact surface in a top view; Figure 5 shows a cross-sectional view through an abrasive body with a profile according to the invention and

[0032] Figure 6 shows a grounding contact in longitudinal section.

[0033] Figure 1 shows an abrasive body with a view towards its circular axial contact surface 2, which has a profile 3 in the form of parallel groove-shaped recesses 5, 6. The groove-shaped recesses 5, 6, 7, 8 can also intersect, as can be seen in the embodiment shown in Figure 2. The contact surface 2 is perpendicular to an axis of rotation D, which in this representation is perpendicular to the plane of the drawing. The axis of rotation D is located at the center of the circular contact surface 2.

[0034] The profiling 3 in the contact surface 2 is produced by a tool 9, which is shown in Figure 3. The tool 9 is an embossing tool with several parallel embossing bars 10, which can be seen on the upper side of the illustrated tool as a zigzag profile. Embossing, as defined in the invention, refers to the deformation of the grinding body by changing the material thickness in certain areas between an upper and lower die, wherein the engraving of the upper die is not the counterpart to the engraving of the lower die. Figure 3 shows the engraving of the upper die. The lower die (not shown) serves as a support. A relatively shallow relief is produced in the axial contact surface of the grinding body by locally displacing the material.

[0035] The individual embossing bars 10 are triangular in cross-section and taper towards the apex 11, while the base 12 of each embossing bar 10 is wider. In this specific embodiment, the sides 13, 14 of all embossing bars 10 are at a 90° angle to each other.

[0036] With the tool 9 shown in Figure 3 for embossing a flat contact surface 2, the entire contact surface 2 can be provided with groove-shaped recesses 5, 6 in a single embossing stroke, extending almost to an edge 4 (Figure 1). A grinding body profiled in this way already effectively prevents the stick-slip effect. The stick-slip effect does not occur, in particular, if further recesses 7, 8 are formed in a second embossing step at a 90° angle to the first recesses 5, 6, as shown in Figure 2. The first recesses 5, 6 and all recesses parallel to them have a first orientation 01. The further recesses 7, 8 and all other recesses parallel to them have an orientation 02 at a 90° angle to the first orientation 01.

[0037] Figures 4 and 5 show, in a highly delayed view, a practical embodiment produced with the tool 9 of Figure 1. Figure 4 shows a top view of a portion of the contact surface 2, depicting intersecting recesses 5, 6, 7. Figure 5 shows a cross-section through an embossed grinding body 1, which is therefore provided with groove-shaped recesses 5, 6. Comparing the zigzag contour of the tool 9 with the profile produced in the contact surface 2, it can be seen that the tool 9 penetrated the contact surface 2 only with its tips 11. Between the adjacent groove-shaped recesses 6 to 8, contact surface areas with a width B1 remain, which are approximately 5 to 6 times larger than the width B2 of the groove-shaped recesses 5, 6. In Figure 5, the center-to-center distance A1 of the recesses is approximately 4.5 mm.The embossed, groove-shaped recesses have a width B2 of approximately 1 mm. Including the rounded flanks at the transition to contact surface 2, the width is 1.2 mm. The groove-shaped recesses 5 and 6 are not absolutely identical in this example, which is due to the manufacturing process.

[0038] Figure 5 shows that the contour of the groove-shaped depressions 5, 6 has a smooth, rounded transition into the contact surface 2. Particularly pronounced embossing ridges are not visible in the chosen representation; however, the embossing or pressing by the tool results in material displacement and not material removal. The material is typically displaced laterally towards the undeformed contact surfaces 2. These may be slightly convex after embossing, especially in the diamond design according to Figure 4. A metallographic examination can distinguish an embossed depression from a depression produced by material removal.

[0039] It should be noted that the maximum depth T1 shown here will decrease in the range of 0.1 to 0.6 mm with increasing wear of the grinding wheel 1, whereby any embossed ridges or protrusions are initially removed. However, long-term tests have shown that the stick-slip effect is still avoided even after any embossed ridges have been removed.

[0040] Figure 6 shows an example of an installation situation for an abrasive element 1 in a grounding contact 16. The abrasive element 1 is spring-loaded and pressed against a brush body 17 in a cover 18. The abrasive element 1 is arranged in a sleeve 19, against which a spring 20 presses. A cuff is arranged on the sleeve 19 to separate it from the interior of the cover 18.

[0041] Reference mark:

[0042] 1 - Grinding wheel

[0043] 2 - Contact area of ​​1

[0044] 3 - Profiling in 2

[0045] 4 - Edge of 2

[0046] 5 - Grooved indentation

[0047] 6 - Grooved indentation

[0048] 7 - Grooved indentation

[0049] 8 - Grooved depression

[0050] 9 - Tools

[0051] 10 - Embossing bridge

[0052] 11 - Top of 10

[0053] 12 - Base of 10

[0054] 13 - Page 10

[0055] 14 - Page 10

[0056] 15 - Contact area

[0057] 16 - Grounding contact

[0058] 17 - Brush body

[0059] 18 - Lid of 16

[0060] 19 - Sleeve

[0061] 20 - Spring

[0062] 21 - Cuff

[0063] A1 - Center-to-center distance between 5 and 6

[0064] B1 - Width of 15

[0065] B2 - Width of 5

[0066] D - axis of rotation

[0067] T 1 - Depth of 5 and 6

Claims

Patent claims 1. Grinding element (1 ) of an earthing contact (16) of a rail-bound vehicle, wherein the grinding element (1 ) has a contact surface (2) for a sliding contact with a brush body (17), wherein the contact surface (2) has a profile (3), characterized in that the profile (3) is formed by a tool (9).

2. Grinding body (1 ) according to claim 1 , characterized in that the profiling (3) has at least one groove-shaped recess (6-8).

3. Grinding body (1 ) according to claim 2, characterized in that the multiple recesses (5, 6: 7, 8) run parallel to each other.

4. Grinding body (1 ) according to claim 2, characterized in that the profiling (3) has several intersecting groove-shaped recesses (6-8).

5. Grinding body (1 ) according to claim 4, characterized in that the groove-shaped recesses (6-8) intersect at an angle of 90°.

6. Grinding body (1 ) according to claim 1 , characterized in that the profiling (3) has several point-shaped depressions produced by embossing.

7. Grinding body (1 ) according to one of claims 3 to 6, characterized in that the recesses (6-8) are arranged at a center distance (A1 ) of 2 to 12 mm, in particular at a center distance (A1 ) of 3 to 6 mm.

8. Grinding body (1 ) according to one of claims 2 to 7, characterized in that the recess (6-8) has a maximum depth (T1 ) of 0.1 to 0.6 mm.

9. Grinding body (1 ) according to one of claims 2 to 8, characterized in that an embossed bead projecting towards the contact surface (2) is arranged adjacent to the at least one recess (6 - 8).

10. Tool (9) for producing a profile (3) in a contact surface (2) of a grinding body (1 ) of an earthing contact with the features according to one of claims 1 to 8, characterized in that the tool (9) for producing the profile (3) in the contact surface (2) of the grinding body (1 ) has at least one embossing projection (10) which tapers from its base (12) to its tip (11 ).

11. Tool (9) according to claim 9, characterized in that the embossing projection (10) has a triangular cross-section, wherein its sides (13, 14) are arranged at an angle of 80 to 100°.

12. Tool (9) according to claim 9 or 10, characterized in that several of the embossing projections (10) are arranged parallel and form a zigzag profile on the tool (9).

13. Tool (9) according to one of claims 10 to 12, characterized in that the embossing projection (10) is arranged on an embossing die or that the embossing projection is an embossing tip of a scribing marking machine or a needle marking machine.

14. Tool (9) according to one of claims 10 to 13, wherein the embossing projection (10) is made of a hardened steel material.

15. Method for producing an abrasive body (1 ) according to the features of one of claims 1 to 14, characterized in that a profile (3) is pressed into the contact surface (2) of the abrasive body (1 ) using a tool (9).

16. Method according to claim 15, characterized in that at least one groove-shaped or dot-shaped depression (6 - 8) is produced with the tool (9), wherein the material displaced from the depression (6-8) forms an embossed bead adjacent to the depression (6-8).

17. Method according to claim 16, characterized in that the embossing of the profiling (3) is carried out in several embossing steps, wherein in a first embossing step depressions (5, 6) with a first orientation (01) are produced and in a second embossing step depressions (7, 8) with a second orientation (02) are produced, wherein the two orientations (01 , 02) differ from each other.

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