Grounding ring and arrangement encompassing such a grounding ring

Description

Technical field

[0001] The invention relates to an earthing ring and an arrangement comprising such an earthing ring. State of the art

[0002] An earthing ring and an arrangement comprising such an earthing ring are known from DE 10 2018 105 376 A1.

[0003] The grounding ring is designed as a pre-seal for a sealing ring and consists of an electrically conductive material which, during its intended use, is in contact with the surface of a first machine element to be grounded. A second machine element, which, like the first machine element, consists of an electrically conductive material and is arranged concentrically to the first machine element, is grounded to a defined ground potential, with the first and second machine elements being electrically connected by the grounding ring.

[0004] From DE 10 2013 000 982 A1, a seal is known that comprises a sealing ring with at least one dynamically stressed sealing lip and a pre-seal designed as a grounding ring. The pre-seal is arranged axially adjacent to the sealing lip and is made of an electrically conductive material. The sealing lip and the pre-seal enclose a surface to be sealed on a first machine element, the first machine element being arranged radially adjacent to a second machine element. The sealing ring and the pre-seal are arranged in the gap formed by the radial distance. The second machine element is grounded to a defined ground potential, with the first and second machine elements being in contact with each other by the pre-seal and thus electrically connected.

[0005] The upstream seal is designed as a potential equalization ring and consists, for example, of an electrically conductive nonwoven fabric impregnated with PTFE. Mechanical damage to the machine elements due to electrical breakdown is therefore impossible.

[0006] Without electrical equipotential bonding, mechanical damage to the machine elements that are to be sealed against each other could occur due to the equalization of differing electrical potentials between the machine elements through electrical breakdown. Such a breakdown is more likely the closer the machine elements with differing electrical potentials are located to each other. A breakdown can cause material loss on the machine element with the relatively lower charge and alter the material structure in the area where the breakdown occurs.

[0007] A further upstream seal is known from DE 10 2014 010 269 A1. The upstream seal comprises a substantially annular disc made of an electrically conductive and air-permeable material and a support body, wherein the disc – in relation to the support body – is designed as a separately manufactured component and connected to the support body.

[0008] The supporting body can be formed by a sealing ring.

[0009] The upstream seal not only serves to provide electrical equipotential bonding, but also to prevent contaminants from the environment from penetrating to the sealing lip of the sealing ring. The upstream seal acts as a decoupled electrical bridge. In this context, "decoupled" means that the sealing function of a sealing ring, for example, when combined with the upstream seal, is decoupled from the function of the electrical bridge, namely to prevent voltage breakdown and to achieve electrical equipotential bonding between the machine elements.

[0010] From WO 2017 / 148586 A1, a shaft grounding ring is known which serves to dissipate induced voltages or electrical charges from a first machine element, preferably a shaft, to a second machine element. The shaft grounding ring has an annular housing made of electrically conductive material, which is electrically connected to one of the machine elements and is in electrically conductive contact with at least one discharge element. The discharge element is also made of an electrically conductive material and is in electrically conductive contact with the other machine element. The discharge element is a disk-shaped discharge body extending at least over part of its circumference.

[0011] From JP H07 253165 A, an earthing ring is known, according to the preamble of claim 1, which is used in a ferrofluid seal. The ferrofluid is held in the sealing gap between two machine elements to be sealed against each other by a suitable magnetic field.

[0012] The grounding ring has an annular cross-section and extends, in the circumferential direction of the shaft to be sealed, in a wave-like pattern within a circumferential gap bounded by the two concentrically arranged machine elements. The grounding ring serves to provide electrical equipotential bonding. This is intended to prevent mechanical damage to the machine elements caused by electrical breakdown.

[0013] Another grounding ring is known from CN 105 305 357 A. This grounding ring has the form of a sleeve on which radially extending sliding contacts are arranged around the outer circumference. These sliding contacts are designed to deflect from an axial to a radial direction relative to the sleeve. The sliding contacts are arranged adjacent to one another at uniform intervals in the circumferential direction, with the circumferential distance between adjacent sliding contacts being at least equal to the width of the sliding contacts in the circumferential direction and remaining constant during intended use.

[0014] US Patent 2016 / 050781 A1 discloses a movable grounding ring used in conjunction with a capacitively coupled plasma processing chamber with an adjustable gap. The grounding ring has a substantially L-shaped cross-section with an annular axial leg, which is connected at one end to a radial leg. The radial leg has several projections, evenly distributed around the circumference and extending radially.

[0015] US Patent 2014 / 0041938 A1 discloses a grounding adapter in which a grounding ring is used. The grounding ring comprises an annular hub and several L-shaped tongues arranged circumferentially on the outside of the hub, extending in the circumferential direction. The tongues arranged adjacent to each other circumferentially are always spaced at a constant distance from one another, with a substantially V-shaped circumferential gap always present between the adjacent tongues. Description of the invention

[0016] The invention is based on the objective of further developing a grounding ring in such a way that essentially the entire circumference of the machine element in contact with the sliding contacts is used for contact by the sliding contacts, thereby equalizing different electrical potentials of the machine elements electrically connected by the grounding ring. Voltage breakdowns between the machine elements are to be effectively prevented.

[0017] Furthermore, the grounding ring should be cost-effective and process-reliable in terms of economics and manufacturing technology.

[0018] This problem is solved according to the invention by an earthing ring according to claim 1 and an arrangement according to claim 9.

[0019] Advantageous embodiments of the grounding ring are referred to in the claims directly or indirectly referring back to claim 1, and advantageous embodiments of the arrangement are referred to in the claims directly or indirectly referring back to claim 9.

[0020] To solve the problem, an earthing ring is provided, comprising a substantially annular hub and at least two circumferentially extending sliding contacts arranged radially on the outside of the hub, which in the manufacturing state of the earthing ring are arranged adjacent to each other at a distance in the circumferential direction and whose sides facing each other in the circumferential direction define a substantially V-shaped circumferential gap and wherein the circumferential gap is substantially bridged by the mutually facing and non-overlapping sides during the intended use of the earthing ring.

[0021] The sliding contacts of the grounding ring according to the invention are designed for external contact in the radial direction. In principle, the grounding ring according to the invention is used in an arrangement with a first and a second machine element during its intended use, wherein the grounding ring and the two machine elements each consist of an electrically conductive material. The first machine element, which is formed, for example, by a shaft or axle, is enclosed on its outer circumference at a radial distance by the second machine element, which is formed by a housing surrounding the shaft or axle at a radial distance. The externally contacting grounding ring is arranged in the gap formed by this distance. The two machine elements are electrically connected to each other by the grounding ring.During intended use, the grounding ring ensures electrical potential equalization between the machine elements and thus prevents electrical breakdown.

[0022] In its manufactured state, the grounding ring essentially has the shape of an annular disc, which on the inside in a radial direction comprises the annular hub and on the outside in a radial direction comprises the sliding contacts arranged adjacent to each other in the circumferential direction with the circumferential gap.

[0023] During intended use, i.e., when the grounding ring is installed, an overlap between the machine element to which the sliding contacts rest and the sliding contacts is necessary to ensure electrically conductive contact at all times, even if the machine element and the sliding contacts are not arranged exactly concentrically to each other and / or the machine element and / or the sliding contacts have an imbalance during intended use.

[0024] This necessary overlap requires the sliding contacts to be reduced from their manufacturing state to a smaller diameter for intended use, making slotting between the individual sliding contacts unavoidable. Without slotting, the outer circumference would be compressed and wrinkled circumferentially during installation of the grounding ring.

[0025] However, the unavoidable slotting means that, depending on the design of the slots, the entire circumference of the adjacent machine element can no longer be touched by the sliding contacts.

[0026] If part of the inner circumference of the machine element is not in contact with the sliding contacts, the effectiveness of the electrical potential equalization is impaired, so that despite an earthing ring in the arrangement, an undesired electrical breakdown can occur between the machine elements.

[0027] To prevent this, the grounding ring according to the invention is designed so that the circumferential gap is essentially bridged by the opposing, non-overlapping sides during the intended use of the grounding ring. Such a grounding ring, which makes external contact in the radial direction, has the advantage that practically the entire inner circumference of the machine element radially adjacent to the sliding contacts is in contact with the sliding contacts. This virtually complete contact of the inner circumference of the machine element radially adjacent to the sliding contacts ensures the best possible electrical equipotential bonding and the greatest protection against electrical breakdowns and damage to the machine elements.

[0028] Overlapping of circumferentially adjacent sliding contacts during intended use would also be disadvantageous, because the overlapping sides of adjacent sliding contacts prevent full contact with the adjacent machine element.

[0029] The circumferential gap of the grounding ring is essentially V-shaped in its manufactured state. This V-shaped limitation of the circumferential gap is advantageous in several respects. When the grounding ring is installed, the circumferential gap can be bridged almost completely without the facing sides of adjacent sliding contacts overlapping. This ensures particularly good, virtually continuous contact with the machine element surrounding the sliding contacts on their outer circumference. Furthermore, the V-shaped circumferential gap provides the sliding contacts with a particularly good and strong restoring effect, because the base of the sliding contacts, which secures them to the hub, is comparatively wide.

[0030] The contact force of the sliding contacts against the inner circumference of the radially adjacent machine element is increased by the wide base. This prevents relaxation even during long periods of use, and the sliding contacts always maintain a constant preload against the adjacent machine element.

[0031] In an advantageous embodiment, it can be provided that the number of sliding contacts is 4 to 50.

[0032] The preferred number is 8 to 12.

[0033] This number of sliding contacts achieves a good compromise between the cost-effective manufacturing of the grounding ring and the ability to adapt the sliding contacts to the inner diameter of the machine element surrounding them. The circumferential gaps are essentially bridged by the facing sides of adjacent sliding contacts, without any adverse overlap of the sides of neighboring sliding contacts in the circumferential direction.

[0034] The circumferential gap can have a radial extent of 2 mm to 20 mm. A large radial extent of the circumferential gap is advantageous if the first and second machine elements each have large diameters.

[0035] As previously stated, the sliding contacts can have a base on their side facing the hub in the radial direction and a free end on their side opposite in the radial direction, wherein the base has a first width in the circumferential direction, wherein the free end has a second width in the circumferential direction, and wherein the first width is greater than the second width.

[0036] Preferably, the ratio of the first width to the second width is 1.25 to 1.5. With such a ratio, the circumferential gap can be largely bridged by the facing sides of adjacent sliding contacts, resulting in a particularly large contact area between the sliding contacts and the inner circumferential surface of the machine element surrounding the grounding ring. Furthermore, with such a ratio, the sliding contacts exhibit a sufficiently large restoring force in the installed state during their intended use, ensuring reliable contact and thus reliable electrical equipotential bonding in all operating states of an arrangement encompassing the grounding ring.

[0037] The hub and the sliding contacts can be integrally formed and made of a single material, consisting of an electrically conductive material.

[0038] The electrically conductive material can be a metallic material. Electrically conductive metallic materials are available in a wide variety of specifications and are largely inexpensive. Furthermore, they are easy, cost-effective, and reliable to process into a grounding ring.

[0039] As previously explained, the grounding ring and the two machine elements of the arrangement are each made of an electrically conductive material. The first machine element is enclosed by the second machine element at a radial distance, and the grounding ring, which makes radial external contact, is located in the gap formed by this distance. The grounding ring is connected to the first machine element in a relatively rotationally fixed and electrically conductive manner. It makes electrically conductive, relatively rotatable contact with the second machine element, bearing against it on its inner side in a radial direction under elastic preload. The second machine element surrounds the first machine element circumferentially. The grounding ring provides electrically conductive connection between the two machine elements and ensures electrical equipotential bonding between them.

[0040] The sliding contacts can be assigned to the second machine element with a radial outer overlap of 1 mm to 6 mm.

[0041] The sleep contacts can be assigned to the first machine element with a radial inner overlap of 0.2 mm to 1.2 mm.

[0042] The aforementioned coverings ensure a particularly reliable and good potential equalization between the machine elements through the grounding ring.

[0043] The bending direction of the sliding contacts in the radial direction on the outside of the second machine element can be executed in both axial directions, depending on the mounting direction of the grounding ring.

[0044] The grounding ring is preferably connected to the first machine element by force-fit and / or form-fit. This creates a simple and cost-effective, rotationally rigid connection.

[0045] Generally speaking, it is possible that the grounding ring and the first machine element rotate together, and that the sliding contacts of the grounding ring are thus supported against the inner circumference of the stationary second machine element. It is also possible that the second machine element rotates around the first machine element and the grounding ring.

[0046] The current flow between the grounding ring and the first machine element, to which it is rotationally fixed, can alternatively occur by the hub of the grounding ring and the first machine element being in direct contact or indirectly through an electrically conductive adhesive.

[0047] Preferably, the first machine element and the grounding ring form a pre-assembled unit that performs a relative rotary movement to the second machine element. Brief description of the drawing

[0048] Three examples of an earthing ring are described in theFigure 1a , 1b , 2a , 2b and 3 Each is shown schematically and is described in more detail below. In Figure 1a Figure 1 shows an embodiment of the grounding ring according to the invention in a side view from the right and in its manufacturing state. Figure 1b is an exemplary arrangement according to the invention with the grounding ring made of Figure 1a shown, in Figure 2a is an embodiment of an earthing ring not belonging to the invention, also shown in a side view from the right and in its manufacturing state and in Figure 2b is an exemplary arrangement with the grounding ring made of Figure 2a shown. In Figure 3Another embodiment of the grounding ring according to the invention is shown, which is formed in two parts and is electrically conductive with a radial inner overlap on the first machine element and with a radial outer overlap on the second machine element. Implementation of the invention

[0049] The Figure 1a and 1b show an embodiment of a grounding ring and an arrangement comprising the grounding ring.

[0050] In Figure 1aThe grounding ring is shown in a side view from the right in its manufactured state. The grounding ring comprises the annular hub 1 and twelve sliding contacts 4.1, 4.2, ..., 4.12 arranged radially 2 on the outside of the hub 1. The sliding contacts 4.1, 4.2, ..., 4.12 extend circumferentially 3 and are arranged adjacent to each other at a distance 5 along the circumferential direction 3. The sides 6, 7 of adjacent sliding contacts 4.1, 4.2, ..., 4.12 facing each other in the circumferential direction 3 define the circumferential gap 8, which in the illustrated embodiment is essentially V-shaped.

[0051] In Figure 1b is the grounding ring made of Figure 1a also shown in a view from the right, but during its intended use, installed in an arrangement according to the invention.

[0052] The grounding ring is non-rotatably connected to the first machine element 13, which is designed as a shaft 15 or axle 16, by means of its hub 1. The grounding ring is enclosed on its outer circumference in the radial direction by the second machine element 14, which in the illustrated embodiment is formed by a housing 17. The grounding ring is arranged in the gap 18 between the first machine element 13 and the second machine element 14.

[0053] The grounding ring and the two machine elements 13, 14 each consist of an electrically conductive material.

[0054] During the installation of the grounding ring in the gap 18, the outer diameter of the sliding contacts 4.1, 4.2, ..., 4.12 is reduced to achieve the necessary overlap for pressing the sliding contacts 4.1, 4.2, ..., 4.12 against the inner circumference of the second machine element 14. This overlap causes the sliding contacts 4.1, 4.2, ..., 4.12 to contact the inner circumference of the second machine element 14 under radial preload.

[0055] By mounting the grounding ring together with the first machine element 13 into the second machine element 14, the circumferential gap 8 between the adjacent sliding contacts 4.1, 4.2, ..., 4.12 is essentially completely closed, so that the inner circumference of the second machine element 14 is in virtually continuous contact with the sliding contacts 4.1, 4.2, ..., 4.12 in the circumferential direction. This enables a particularly effective electrical equipotential bonding.

[0056] As especially in Figure 1a As can be clearly seen, the base 9 of the sliding contacts 4.1, 4.2, ..., 4.12 is wider on the side facing the hub 1 in radial direction 2 than the free end 10 opposite the base 9 in radial direction 2.

[0057] In the illustrated embodiment, the ratio of the first width 11 of the base 9 to the second width 12 of the free end 10 is approximately 1.3.

[0058] In the illustrated embodiment, the hub 1 and the sliding contacts 4.1, 4.2, ..., 4.12 are integrally formed and made of a single material, consisting of an electrically conductive metallic material.

[0059] In Figure 2a A non-inventive embodiment of an earthing ring is shown, in which the circumferential gap 8 between the sliding contacts 4.1, 4.2, ..., 4.9 is limited in a U-shape.

[0060] Referring to the V-shaped circumferential gap 8 from Figure 1aThe U-shaped circumferential gap 8 is made of Figure 2a less advantageous because the contact area of ​​the sliding contact 4.1, 4.2, ..., 4.9 to the second machine element 14 is somewhat smaller during the intended use of the grounding ring than in the embodiment shown. Figure 1a is.

[0061] In Figure 2b is the grounding ring made of Figure 2a also shown in a view from the right, but during its intended use, installed in an arrangement according to the invention.

[0062] The grounding ring made of Figure 1a This has the advantage that the sliding contacts 4.1, 4.2, ..., 4.12 / 4.9 do not overlap each other during intended use, which would lead to a reduction of the contact area on the inner circumference of the second machine element 14.

[0063] In Figure 3Another embodiment of the grounding ring is shown, which is formed in two parts and is electrically conductively in contact with the first machine element 13 via a radial inner overlap 20 and with the second machine element 14 via a radial outer overlap 19. In the embodiment shown here, the radial outer overlap 19 is approximately 5 mm, while the radial inner overlap 20 is approximately 1 mm.

[0064] The circumferential gaps 8 in the previously shown embodiments each have a radial extent of 2 mm to 20 mm, depending on the size of the diameters of the two machine elements 13 and 14.

[0065] The circumferential gaps 8 in the previously shown embodiments each have a radial extent of 2 mm to 20 mm, depending on the size of the diameters of the two machine elements 13 and 14.

Claims

1. Earthing ring, comprising a substantially circular-ring-shaped hub (1) and at least two sliding contacts (4.1, 4.2, ...) which are arranged on the outside of the hub (1) in a radial direction (2) and extend in a circumferential direction (3), characterized in that, in the production state of the earthing ring, the sliding contacts are arranged adjacent to one another in the circumferential direction (3) with a spacing (5) and, by way of their sides (6, 7) facing one another in the circumferential direction (3), delimit a substantially V-shaped circumferential gap (8), and in that, during the intended use of the earthing ring, the circumferential gap (8) is substantially bridged by the mutually facing and mutually non-overlapping sides (6, 7).

2. Earthing ring according to Claim 1, characterized in that the number of sliding contacts (4.1, 4.2, ...) is 4 to 50.

3. Earthing ring according to one of Claims 1 or 2, characterized in that the number of sliding contacts (4.1, 4.2, ...) is 8 to 12.

4. Earthing ring according to Claim 1, characterized in that the circumferential gap (8) has a radial extent of 2 mm to 20 mm.

5. Earthing ring according to one of Claims 1 to 3, characterized in that the sliding contacts (4.1, 4.2, ...) have a base (9) on their side facing the hub (1) in the radial direction (2) and have a free end (10) on their opposite side in the radial direction (2), in that the base (9) has a first width (11) in the circumferential direction (3), in that the free end (10) has a second width (12) in the circumferential direction (3), and in that the first width (11) is greater than the second width (12).

6. Earthing ring according to Claim 5, characterized in that the ratio of first width (11) to second width (12) is 1.25 to 1.5.

7. Earthing ring according to one of Claims 1 to 6, characterized in that the hub (1) and the sliding contacts (4.1, 4.2, ...) are formed from the same material and in a manner transitioning integrally into one another and consist of an electrically conductive material.

8. Earthing ring according to Claim 7, characterized in that the electrically conductive material is a metallic material.

9. Arrangement, comprising an earthing ring according to one of Claims 1 to 8 and a first machine element (13) and a second machine element (14), each of which consists of an electrically conductive material, wherein the first machine element (13) is formed by a shaft (15) or an axle (16) and the second machine element (14) is formed by a housing (17) which surrounds the shaft (15) or axle (16) with a radial spacing, wherein the radially externally contacting earthing ring is arranged in the gap (18) formed by the spacing.

10. Arrangement according to Claim 9, characterized in that the earthing ring is connected in a relatively rotationally fixed manner to the first machine element (13), and makes contact with the second machine element (14) relatively rotatably and in a manner abutting at the inside in the radial direction (2).

11. Arrangement according to one of Claims 9 or 10, characterized in that the sliding contacts (4.1, 4.2, ...) are assigned to the second machine element (14) with a radially outer overlap (19) of 1 mm to 6 mm.

12. Arrangement according to one of Claims 9 to 11, characterized in that the brushing contacts (4.1, 4.2, ...) are assigned to the first machine element (13) with a radially inner overlap (20) of 0.2 mm to 1.2 mm.

13. Arrangement according to one of Claims 9 or 12, characterized in that the earthing ring is connected in a force-fitting and / or form-fitting manner to the first machine element (13).