mechanical seal arrangement

Abstract

The invention relates to a mechanical seal arrangement comprising a mechanical seal (2) with a rotating sliding ring (3) and a stationary sliding ring (4), which define a sealing gap (5) between their sliding surfaces, and a secondary sealing element (6), wherein the secondary sealing element (6) has a U-shape in section with a base region (60), a first arm region (61) and a second arm region (62), and wherein an outer surface of the secondary sealing element (6) has a wave-like shape with a first sealing line (11; 14) and a second sealing line (12; 15).

Description

[0001] The present invention relates to a mechanical seal arrangement with an improved secondary sealing element.

[0002] Mechanical seal arrangements are known in various designs from the prior art. O-rings are frequently used as secondary sealing elements. However, applications have recently emerged where the sealing requirements are significantly higher with regard to pressures (greater than 650 × 10⁻⁶). 5 Pa) and temperatures (greater than 350°C) are constantly increasing. One solution is to manufacture secondary sealing elements from different materials, as disclosed, for example, in DE 10 2012 022 465 A1. Another possibility is so-called secondary sealing elements, which have a U-shape in cross-section (U-cups) and often incorporate metallic expansion elements for additional stiffening and sealing.

[0003] The object of the invention is to provide a mechanical seal arrangement which, with a simple design and simple, cost-effective manufacturing, exhibits improved sealing performance, particularly in the area of ​​secondary sealing elements, for higher temperatures and pressures.

[0004] This problem is solved by a mechanical seal arrangement having the features of claim 1, the dependent claims showing preferred embodiments of the invention.

[0005] The mechanical seal assembly according to the invention, with the features of claim 1, has the advantage that not only the actual mechanical seal can withstand very high temperatures and very high pressures, but also the secondary sealing elements used. In particular, the risk of extrusion of the secondary sealing elements, in which material of the secondary sealing elements is extruded into a gap and weakens the secondary sealing element, is prevented. This is achieved according to the invention by the mechanical seal assembly comprising a mechanical seal with a rotating and a stationary sliding ring. The rotating sliding ring has a first sliding surface and the stationary sliding ring has a second sliding surface, with a sealing gap defined between the two sliding surfaces. The mechanical seal assembly further comprises a secondary sealing element which has a U-shape in cross-section.The U-shape comprises a base section and a first and second arm section. The base section connects the two arm sections. One outer surface of the secondary sealing element has a wave-like shape, creating a first and second sealing line. Thus, the secondary sealing element has a U-profile with at least two sealing lines on its outer surface. This ensures a consistently high sealing effect. Particularly under pressure, unlike conventional U-cups, it does not create a flat sealing surface, but rather at least two spatially separated contact lines. This allows for a high level of sealing. Furthermore, the secondary sealing element can be used not only in static applications where it seals against two stationary components, but also in so-called...Dynamic applications where at least one sealing surface moves. This is the case, for example, with mechanical seal arrangements when one of the sliding rings is axially displaced, which is held in particular by a sliding ring carrier, with the secondary sealing element sealing against the sliding ring carrier, which is arranged to be axially movable. In this case, the secondary sealing element according to the invention can in particular prevent so-called "hang-ups", i.e., blockages that are released abruptly, in which the secondary sealing element can be damaged due to relative movements on the surfaces to be sealed.

[0006] Preferably, the first and second sealing lines are arranged together on the outer side of one of the arm sections. The arm section is preferably the section where there is a risk of material from the secondary sealing element extruding into a gap.

[0007] Preferably, two sealing lines are also formed on the outer side of the other arm area. Thus, preferably at least two sealing lines are provided on each of the two arm areas.

[0008] Preferably, a further sealing line is formed on the base region of the secondary sealing element, either on the radially outward-facing outer side and / or on the radially inward-facing side. Thus, preferably, three sealing lines are formed on the radially outward-facing side of the secondary sealing element and three sealing lines are formed on the radially inward-facing side of the secondary sealing element.

[0009] To reliably prevent extrusion into a gap, the secondary sealing element is preferably made of polyetheretherketone (PEEK). PEEK is a relatively rigid material with excellent chemical resistance. Therefore, a wide range of media can be sealed using PEEK. The secondary sealing element can be made entirely of PEEK or of a composite material comprising PEEK and other materials.

[0010] The areas around the sealing lines on the secondary sealing element are particularly preferably coated. The coating preferably has a lower coefficient of friction than the material of the secondary sealing element. The coating is preferably a PTFE coating or a DLC coating.

[0011] Preferably, the arm sections of the secondary sealing element are designed such that, at a first pressure P1 up to a predetermined threshold pressure, which is present in the inner area between the arm sections of the secondary sealing element, only the first sealing line on one, preferably both, arm sections seals. This ensures that, up to the predetermined threshold pressure, only one sealing line on one side of the secondary sealing element comes into contact with the counter-sealing surface. The second sealing line on this side of the secondary sealing element is not in contact with the counter-sealing surface.

[0012] Preferably, the secondary seal seals at both the first and second sealing lines when a second pressure P2 exceeds the predetermined threshold pressure. Thus, two sealing lines are in contact with the respective counter-sealing surface at at least one, preferably both, arm regions.

[0013] Preferably, the arm sections are arranged on the base section such that, in the unpressurized state, the arm sections project from the base section at an acute angle α to a central axis of the secondary sealing element. The acute angle α is preferably less than 30°, particularly less than 20°. In the unpressurized state, the secondary sealing element thus has V-shaped arm sections. The acute angle α of the first arm section is preferably different from the acute angle of the second arm section.

[0014] Preferably, the first and second sealing lines are arranged on the arm areas at wave crests of the wave-like shape on the outer surfaces of the secondary sealing element. The wave crests preferably have different radii. The radii refer to the radii of curvature in the cross-section of the secondary sealing element. In particular, the smallest radius of the wave crest is formed at the crest that is located furthest from the base area.

[0015] Preferably, no prestressing element or separate stiffening element is arranged on or in the secondary sealing element. That is, the secondary sealing element is manufactured entirely from a single material without any internal stiffening elements. The recess between the arm sections of the secondary sealing element is preferably designed with an undercut. Preferably, the recess between the arm sections is shaped like a tab on a puzzle piece.

[0016] A volume of the base area is also preferred, as is the sum of the volumes of the first and second arm areas.

[0017] A mechanical seal arrangement according to a preferred embodiment of the invention is described in detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 a schematic sectional view of a mechanical seal arrangement according to a preferred embodiment of the invention, Fig. 2 a schematic sectional view of a secondary sealing element of the mechanical seal assembly of Fig. 1 in the unpressurized, uninstalled state, Fig. 3 a schematic sectional view of the secondary sealing element in the installed state under a first pressure below a threshold pressure, and Fig. 4 A schematic sectional view of the secondary sealing element in the installed state under a second pressure above the threshold pressure.

[0018] The following refers to the Fig. 1 to 4 describe in detail a mechanical seal arrangement 1 according to a first preferred embodiment of the invention.

[0019] The mechanical seal assembly 1 comprises a mechanical seal 2 with a rotating sliding ring 3 and a stationary sliding ring 4. A sealing gap 5 is defined between the sliding surfaces of the sliding rings 3 and 4. The rotating sliding ring 3 is rigidly connected to a rotating component 9, e.g., a shaft. The stationary sliding ring 4 is arranged on a housing 10.

[0020] The mechanical seal arrangement 1 is designed to seal a first area 21, which is under high pressure, against a second area 22, which is, for example, the atmospheric area.

[0021] The stationary sliding ring 4 is connected to the housing 10 via a sliding ring carrier 43 and a plurality of pins 44. The pins 44 are fixed in the housing 10, but axial movement XX is possible between the pins 44 and the sliding ring carrier 43 because the sliding ring carrier 43 is axially preloaded by spring elements (not shown). This axially preloads the stationary sliding ring 4 relative to the rotating sliding ring 3.

[0022] What's next? Fig. As can be seen in Figure 1, a secondary sealing element 6 is arranged between the sliding ring carrier 43 and the housing 10. The secondary sealing element 6 is shown in detail below. Fig. 2 to 4 are visible.

[0023] As from Fig. As can be seen in Figure 1, the secondary sealing element 6 is arranged at an extrusion gap 7 between the housing 10 and the sliding ring carrier 43. In this area, there is a very high pressure gradient across the secondary sealing element 6, so that during operation there is a risk that the material of the secondary sealing element 6 could be extruded into the extrusion gap 7.

[0024] The secondary sealing element 6 according to the invention can, however, prevent such extrusion into the extrusion gap 7. As shown from Fig. As can be seen in Figure 2, the secondary sealing element 6 comprises a base area 60, a first arm area 61 and a second arm area 62. The secondary sealing element 6 is made entirely of PEEK.

[0025] Fig. Figure 2 shows the secondary sealing element 6 in its unloaded state, in which the secondary sealing element 6 is not installed in the mechanical seal assembly 1. The secondary sealing element 6 forms a U-profile with the base region 60 and the first and second arm regions 61, 62. In the unloaded state, the first arm region 61 is arranged on a first axis X1 and the second arm region 62 on a second axis X2. As shown in Fig. As can be seen in Figure 2, the first axis X1 and the second axis X2 are arranged at an acute angle α to a center line M of the secondary sealing element. The angle α is preferably 20°. In the unpressurized state, the secondary sealing element 6 thus has arm sections 61, 62 in a V-shape. The acute angles α can be of equal or different magnitudes.

[0026] The U-profile has a central recess 65 formed between the two arm sections 61, 62. The volume of the base section 60 is greater than the sum of the volumes of the first and second arm sections 61, 62.

[0027] A radially outwardly directed outer surface 63 of the secondary sealing element 6 has a wave-like shape with a first sealing line 11, a second sealing line 12, and a third sealing line 13. The first sealing line 11 and the second sealing line 12 are formed at the first arm region 61. The third sealing line 13 is formed at the base region 60.

[0028] The secondary sealing element 6 can be designed symmetrically to the central axis M.

[0029] On the second arm section 62, a fourth sealing line 14 and a fifth sealing line 15 are formed on a radially inwardly directed outer surface 64. Furthermore, a sixth sealing line 16 is formed on the radially inwardly directed side of the base section 60.

[0030] Thus, the secondary sealing element 6 has three sealing lines on a radially outward-facing outer surface 63 and also three sealing lines on a radially inward-facing outer surface 64.

[0031] The three sealing lines on the outer surfaces 63, 64 have three different radii of curvature. The first sealing line 11 and the fourth sealing line 14 have a first radius R1. The second sealing line 12 and the fifth sealing line 15 have a second radius R2. The third sealing line 13 and the sixth sealing line 16 have a third radius R3. The first radius R1 is smaller than the second radius R2, and the second radius R2 is smaller than the third radius R3.

[0032] In the Fig. 3 and Fig. Figure 4 shows the secondary sealing element 6 in its installed state. The secondary sealing element 6 seals in Fig. 3 compared to a first pressure P1 from and into Fig. 4 against a second pressure P2. The second pressure P2 is greater than the first pressure P1. The recess 65 is directed towards the medium to be sealed.

[0033] The initial pressure P1 is below a predetermined threshold pressure, causing the secondary sealing element 6 to deform into a defined, predetermined shape. Details are provided in Fig. As shown in Figure 3, with the first pressure P1, a seal is only formed at the first arm area 61 at the first sealing line 11 and at the second arm area 62 at the fourth sealing line 14.

[0034] The first print P1 in Fig. 3 lies below the predetermined threshold pressure. A reliable seal is therefore only possible by the application of the front sealing lines 11, 14, which are directed towards the mechanical seal 2. These have the smallest radius R1 of the sealing lines and thus enable a relatively narrow sealing line. As in Fig. The V-arrangement of arm sections 61, 62 shown in the uninstalled state is pressed against the respective counter-sealing surfaces when installed. This creates a seal at the sealing lines 11, 14. Since PEEK is a relatively stiff material and the arm sections 61, 62 are radially prestressed, sufficient sealing against the initial pressure P1 is possible. This results in a first cavity 17 on the outer side 63 and a second cavity 18 on the inner side 64.

[0035] A dimension of the secondary sealing element 6 at the base area 60 is chosen such that the third sealing line 13 and the sixth sealing line 16 are fitted as a match to the housing 10 and to the sliding ring carrier 43 respectively.

[0036] Fig. Figure 4 shows the secondary seal 6 at a second pressure P2, which is greater than the first pressure P1 and greater than the specified threshold pressure. At this pressure P2, the arm sections 61, 62 undergo additional deformation such that a seal is formed at the first sealing line 11 and the second sealing line 12 on the first arm section 61, and a seal is formed at the fourth sealing line 14 and the fifth sealing line 15 on the second arm section 62. Due to the stiffness of the secondary sealing element, the first cavity 17 remains between the first sealing line 11 and the second sealing line 12, and the second cavity 18 remains between the fourth sealing line 14 and the fifth sealing line 15 (see Figure 4). Fig. 4) A third cavity 19 is formed between the second sealing surface 12 and the third sealing surface 13, and a fourth cavity 20 is formed between the fifth sealing line 15 and the sixth sealing line 16.

[0037] The overall shape of the rigid secondary sealing element 6 remains unchanged even under the very high second pressure P2. The second pressure P2 thus only causes a deformation of the secondary sealing element 6 in the area of ​​the first and second arm sections 61, 62, so that each arm section has two sealing lines to the corresponding counter-sealing surfaces.

[0038] The predetermined threshold pressure is preferably in the range of 100 × 10 5 Pa. If necessary, the areas with the sealing lines can be coated, for example with PTFE to increase the sealing effect or DLC to increase the sliding properties of the secondary sealing element 6. Since, in the described embodiment, the stationary sliding ring 4 is axially movable in the axial direction XX, the sealing lines 14, 15, 16 could be coated with DLC and the sealing lines 11, 12, 13 with PTFE.

[0039] For a simple coating process, it is also possible to coat the entire radially outward-facing side or the entire radially inward-facing side of the secondary sealing element 6.

[0040] Thus, according to the invention, both a static sealing point and a dynamic sealing point (axial movement of the sliding ring carrier 43) can be reliably sealed on the secondary sealing element 6. An optimum has been achieved in meeting seemingly opposing requirements for the secondary sealing element: sufficient stiffness to prevent extrusion into the extrusion gap 7 and sufficient sealing effect. Therefore, the secondary sealing element according to the invention can also be used at pressures of up to 650 × 10 5 Pa can be used. No support ring or internal metal material for stiffening or the like is required on the secondary sealing element. This allows the costs for the secondary sealing element 6 to be kept low.

[0041] Thus, a pressure-dependent support effect can be achieved via additional sealing lines as the pressure increases in the interior of the recess 65 of the secondary sealing element. The sealing lines are located at the crests of the corrugated outer surfaces 63, 64. The increasing pressure therefore supports the sealing effect in addition to the existing inherent elasticity of the secondary sealing element 6, starting from the in Fig. 2 V-shaped arrangement of arm areas 61, 62 shown.

[0042] It should be noted that each of the arm areas 61, 62 can also have more than two sealing lines, for example three sealing lines or four sealing lines.

[0043] Preferably, all sealing lines on one of the arm areas always have different radii of curvature in cross-section.

[0044] The distance in the axial direction between adjacent sealing lines is also preferably always different. Reference symbol list 1 Mechanical seal assembly 2 mechanical seals 3 rotating sliding ring 4 stationary sliding ring 5 Sealing gap 6 Secondary sealing element 7 Extrusion gap 9 rotating component 10 cases 11 first sealing line 12 second sealing line 13 third sealing line 14 fourth sealing line 15 fifth sealing line 16 sixth sealing line 17 first cavity 18 second cavity 19 third cavity 20 fourth cavity 21 first area 22 second area / atmospheric area 43 Sliding ring carriers 44 pens 60 Basic area 61 first arm area 62 second arm area 63 radially outward facing outer surface of the secondary sealing element 64 radially inwardly directed outer side of the secondary sealing element 65 Exclusion M center line of the secondary sealing element P1 first print P2 second pressure R1 first radius R2 second radius R3 third radius XX Axial direction X1 first axis of the first arm area 61 X2 second axis of the second arm area 62 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 022 465 A1

[0002]

Claims

[1] Mechanical seal assembly comprising: - a mechanical seal (2) with a rotating sliding ring (3) and a stationary sliding ring (4), which define a sealing gap (5) between their sliding surfaces, and - a secondary sealing element (6), - wherein the secondary sealing element (6) has a U-shape in section with a base area (60), a first arm area (61) and a second arm area (62), and - wherein an outer surface of the secondary sealing element (6) has a wave-like shape with a first sealing line (11; 14) and a second sealing line (12; 15). [2] Mechanical seal arrangement according to claim 1, wherein the first sealing line (11; 14) and the second sealing line (12; 15) are arranged on a radially outward and / or radially inward directed outer side of the arm areas (61, 62). [3] Sliding ring seal arrangement according to one of the preceding claims, wherein the secondary sealing element (6) further comprises a third sealing line (13; 16) at the base area. [4] Mechanical seal arrangement according to one of the preceding claims, wherein the secondary sealing element (6) is made of PEEK or is made of a composite material comprising PEEK. [5] Mechanical seal arrangement according to one of the preceding claims, wherein in the assembled state a cavity (17; 18) is formed between the first sealing line (11; 14) and the second sealing line (12; 15). [6] Mechanical seal arrangement according to one of the preceding claims, wherein the areas of the secondary sealing element (6) on which the sealing lines are arranged are coated. [7] Sliding ring seal arrangement according to one of the preceding claims, wherein the arm areas (61, 62) are designed such that at a first pressure (P1) up to a predetermined threshold pressure in a recess (65) between the arm areas (61, 62) only the first sealing line (11; 14) seals. [8] Sliding ring seal arrangement according to claim 7, wherein at a second pressure (P2) above the threshold pressure in the recess (65) between the arm areas (61, 62) the first sealing line (11; 14) and the second sealing line (12; 15) seals. [9] Sliding ring seal arrangement according to one of the preceding claims, wherein the arm regions are arranged on the base region (60) such that in the unpressurized state the arm regions (61, 62) project at an acute angle (a) to the center line (M) of the secondary sealing element. [10] Sliding ring seal arrangement according to claim 9, wherein the acute angles (a) to the center line of the secondary sealing element are of different sizes. [11] Mechanical seal arrangement according to one of the preceding claims, wherein the first sealing line (11; 14) and the second sealing line (12; 15) are arranged on wave crests of the wave-like shape of the outside of the secondary sealing element. [12] Mechanical seal arrangement according to claim 11, wherein the first sealing line (11; 14) has a first radius (R1) and the second sealing line (12; 15) has a second radius (R2) which is different from the first radius (R1). [13] Sliding ring seal arrangement according to claim 12, wherein the first radius (R1) is smaller than the second radius (R2). [14] Mechanical seal arrangement according to claim 12 or 13, wherein a smallest radius of the wave crests of the arm regions (61, 62) is spaced furthest from the base region (60).

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