Mechanical seal arrangement for a rotary union

Description

[0001] The present invention relates to an internally pressurized mechanical seal arrangement for a rotary feedthrough, in which a medium to be sealed is passed through the interior of the mechanical seal. The present invention further relates to a rotary feedthrough with a mechanical seal arrangement according to the invention.

[0002] Mechanical seal assemblies are known in various configurations from the prior art. Typically, mechanical seals are used for sealing shafts or other rotating components, with the seal being pressurized externally, where the medium to be sealed is located radially outside the sealing gap. However, in a wide variety of industrial applications, connections between stationary and rotating components must be bridged using rotary unions, which must be appropriately sealed. Particularly in the food industry, when filling liquids, for example, the seals on the rotary union must prevent any contamination of the filling medium. Furthermore, appropriate cleaning and sterilization processes must be possible without disassembling the rotary union.the sealing components are necessary.

[0003] Furthermore, DE 10 2014 221000 B3 discloses a mechanical seal arrangement according to the preamble of claim 1.

[0004] WO 2004 / 051130 A1 and EP 0 392 838 A2 disclose a mechanical seal arrangement with a preloading device located in the fluid channel.

[0005] Further mechanical seal arrangements are known from DE 38 10 060 A1 and DE 83 30 159 U1.

[0006] It is therefore an object of the present invention to provide an internally pressurized mechanical seal assembly which can be used in particular in rotary feedthroughs and which, in addition to being simple in design and easy and cost-effective to manufacture, can also be cleaned easily and safely without disassembly and, if necessary, can also be sterilized. Furthermore, it is an object of the present invention to provide a rotary feedthrough with a mechanical seal assembly, in particular for conveying liquid foodstuffs.

[0007] This problem is solved by a mechanical seal arrangement with the features of claim 1 or a rotary feedthrough with the features of claim 11. The dependent claims describe preferred embodiments of the invention.

[0008] The mechanical seal assembly according to the invention, with the features of claim 1, has the advantage that the mechanical seal assembly is pressurized internally, thus allowing the medium to pass through the interior of the mechanical seal assembly. This enables a reliable seal of the internally conveyed medium and also allows for simple and quick cleaning without disassembly. Furthermore, the mechanical seal assembly can also be sterilized without the need for disassembly. According to the invention, this is achieved by the mechanical seal assembly comprising a pressurized mechanical seal with a rotating sliding ring and a stationary sliding ring, which define a sealing gap between them. At the sealing gap, the inner diameter of the rotating sliding ring is equal to the inner diameter of the stationary sliding ring.This prevents steps or similar formations directly at the sealing gap, thus minimizing the accumulation of particles or similar substances near the sealing gap during use of the mechanical seal assembly. Furthermore, this also allows for very effective cleaning of the mechanical seal at the sealing gap. The mechanical seal assembly also includes a preloading device that axially preloads one of the sliding rings against the other. Preferably, the preloading device is arranged on the stationary sliding ring. The mechanical seal assembly includes a secondary seal, which is arranged on the axially preloaded sliding ring such that the secondary seal moves axially with the preloaded sliding ring, i.e., in the direction of flow through the mechanical seal.Thus, according to the invention, it is ensured that the secondary seal always remains in the same position relative to the axially preloaded sliding ring, in contrast to when the secondary seal is located on the component to be sealed and does not move axially together with the axially preloaded sliding ring. Therefore, the secondary seal can always remain in the optimal sealing position on the axially preloaded sliding ring.

[0009] Furthermore, the preloading device is positioned on the mechanical seal in such a way that there is no contact with the medium being sealed. This has the advantage that the preloading device, which can be, for example, coil springs, wave springs, or the like, has no hard-to-clean spaces, undercuts, or similar features. This significantly simplifies cleaning and sterilization.

[0010] Furthermore, the axially preloaded sliding ring has a main region and a secondary region, with a sliding surface of the sliding ring arranged in the main region and the secondary region having a smaller outer diameter than the outer diameter of the main region. The secondary seal is arranged in the secondary region of the axially preloaded sliding ring. This design also has the advantage that the secondary region provides a certain degree of guidance for the medium flowing through the inside of the mechanical seal assembly.

[0011] Furthermore, the rotating sliding ring and the stationary sliding ring each have a bandage. The bandages are preferably identical. More preferably, the bandages are designed such that the radial height of the bandages is greater than the maximum radial height of the rotating and stationary sliding rings.

[0012] Preferably, the secondary seal is arranged on a radially outward-facing side of the axially preloaded sliding ring. The position of the secondary seal on the axially preloaded sliding ring is preferably at an end facing away from a sliding surface of the axially preloaded sliding ring. This arrangement of the secondary seal on the axially movable sliding ring offers particular advantages during cleaning, as it places the sealing point between the sliding ring and an external component as close as possible to the end of the sliding ring opposite the sealing gap, thus preventing unwanted forces from being introduced onto the sliding ring near the sealing gap via the secondary seal.

[0013] The bands are preferably arranged on the sliding ring such that a center of gravity of the band and a center of gravity of the sliding ring lie in a common plane perpendicular to a central axis of the mechanical seal assembly. Thus, in the radial direction, the centers of gravity of the sliding ring and band are aligned. This ensures that the mechanical seal can be designed for high pressures without causing damage to the sliding rings.

[0014] According to a further preferred embodiment of the present invention, the pretensioning device is arranged such that it engages exclusively with the bandage. This has the advantage that no additional forces are exerted directly on the sliding ring by the pretensioning device during operation. Preferably, the pretensioning device engages with a radially innermost region of the bandage.

[0015] The secondary seal is particularly preferably arranged in a circumferential groove on the adjacent region of the axially preloaded sliding ring. Here, a flange forms one end region of the axially preloaded sliding ring. The first width of the flange is smaller than the second.

[0016] Width of the circumferential groove. Preferably, the outer diameter of the flange is smaller than the outer diameter of the secondary area. This allows the secondary seal to be slightly compressed in the assembled state and to cover a radial outer surface of the flange. This enables particularly reliable and sterile cleaning in this area of ​​the mechanical seal assembly.

[0017] According to a further preferred embodiment of the invention, the sliding ring seal assembly also comprises fixing elements, wherein the fixing elements are provided for fixing the sliding rings. The fixing elements are arranged on the bandage. This eliminates the need for recesses or the like on the sliding rings for the fixing elements, and the sliding rings are fixed via the bandages. This significantly simplifies the manufacture of the sliding rings.

[0018] The mechanical seal assembly preferably further comprises a stationary component against which the preloading device is supported, wherein the inner diameter of the support component is preferably larger than the inner diameter of the axially preloaded sliding ring. This ensures that the flow velocity through the mechanical seal assembly increases in the area of ​​the mechanical seal, as the flow cross-section at the mechanical seal assembly is reduced.

[0019] Preferably, the inner diameter of the rotating sliding ring and the inner diameter of the stationary sliding ring are constant over the entire axial length of the sliding rings. This prevents areas and depressions on the inner surfaces of the sliding rings where contamination or similar substances could occur within the mechanical seal assembly.

[0020] Furthermore, the present invention relates to a rotary feedthrough with a mechanical seal arrangement according to the invention. The rotary feedthrough is preferably used in the food industry, particularly in systems for handling beverages or water, for example, filling plants.

[0021] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawing. In the drawing, identical or functionally equivalent parts are designated by the same reference numerals. The drawing shows: Fig. 1 a schematic sectional view of a rotary feedthrough with a mechanical seal arrangement according to a first embodiment of the invention, Fig. 2 an enlarged, schematic sectional view of a secondary seal of Fig. 1 , Fig. 3 a schematic sectional view of a rotary feedthrough with a mechanical seal arrangement according to a second embodiment of the invention, and Fig. 4 a schematic sectional view of a rotary feedthrough with a mechanical seal arrangement according to a third embodiment of the invention.

[0022] The following refers to the Fig. 1 and 2 A mechanical seal arrangement 1 of a rotary feedthrough is described in detail.

[0023] The rotary feedthrough is located in a food processing machine and serves to connect a pipe section to a rotating, hollow shaft. The hollow shaft is a rotating component 13 and the pipe section is a stationary component 14.

[0024] As from Fig. 1 As can be seen, the mechanical seal arrangement 1 comprises a mechanical seal 2 with a rotating sliding ring 3 and a stationary sliding ring 4. The rotating sliding ring 3 and the stationary sliding ring 4 define a sealing gap 5 between their sealing surfaces 3', 4'.

[0025] The mechanical seal 2 is an internally pressurized mechanical seal in which the medium to be sealed flows inside the mechanical seal 2. Arrow 10 in Fig. 1 This indicates the direction of flow through the mechanical seal assembly 1. In this embodiment, the medium flows from the stationary component 14 into the rotating component 13.

[0026] The mechanical seal assembly 1 further comprises a preloading device 6. In this embodiment, the preloading device 6 preloads the stationary sliding ring 4 against the rotating sliding ring 3.

[0027] The preload device 6 comprises a plurality of cylindrical helical springs arranged along the circumference in recesses 14a of the stationary component 14. The helical springs are arranged at equal intervals along the circumference. Preferably, 3 to 9 helical springs are provided.

[0028] As from Fig. 1 As can be seen, the rotating sliding ring 3 has a first bandage 30 and the stationary sliding ring 4 has a second bandage 40. The two bandages 30 and 40 are identical in construction. As can be seen from Fig. 1 As can be seen, the radial height H of the bandages 30, 40 is each greater than the maximum radial thickness 11 of the rotating sliding ring 3 and the stationary sliding ring 4. The sliding rings have the same radial thickness 11.

[0029] What's next? Fig. 1 As can be seen, the first bandage 30 is arranged on the rotating sliding ring 3 such that a center of gravity S1 of the rotating sliding ring 3 and a center of gravity S3 of the first bandage 30 lie in a common plane, which is perpendicular to a central axis XX of the mechanical seal assembly 1. In other words, the center of gravity S1 and the center of gravity S3 are radially aligned. The stationary sliding ring 4 and the second bandage 40 also each have a center of gravity S2 and S4, which are radially aligned, i.e., in a common plane perpendicular to the central axis XX.

[0030] The bandages 30 and 40 each enclose the rotating and stationary sliding rings, respectively, with a force-fit connection between the sliding rings 3 and 4 and the bandages 30 and 40. As further explained below... Fig. 1 As can be seen, the pretensioning device 6 engages the stationary sliding ring 4 on the second bandage 40, so that the stationary sliding ring 4 is axially pretensioned via the second bandage 40 in the direction of the rotating sliding ring 3.

[0031] What's next? Fig. 1 As can be seen, the mechanical seal assembly 1 further comprises a fixing device 9. The fixing device 9 fixes, on the one hand, the rotating sliding ring 3 to the rotating component 13 and, on the other hand, the stationary sliding ring 4 to the stationary component 14. The fixing device 9 includes several fixing pins 90, which are arranged in through-holes in the second bandage 40 and thus fix the bandage 40 to the stationary component 14. Several fixing pins 90 are provided evenly distributed around the circumference of the second bandage 40. The first bandage 30 is fastened to the rotating component 13 by means of fixing screws 91. In the same manner as the fixing pins 90, the fixing screws 91 are arranged around the circumference of the first bandage 30, thus screwing the first bandage 30 to the rotating component 13.

[0032] In the circumferential direction, fixing pins 90 of the fixing device 9 and coil springs of the preloading device 6 can be arranged alternately on the stationary component 14.

[0033] The mechanical seal arrangement 1 further comprises a secondary seal 7, which is arranged on the axially preloaded stationary sliding ring 4 such that the secondary seal 7 moves together with the axially preloaded sliding ring 4 in the axial direction (direction of the central axis XX).

[0034] Here, a circumferential groove 4a is arranged on a radially outwardly directed side of the stationary sliding ring 4. As shown from Fig. 1 As can be seen, the circumferential groove 4a is provided on an end side of the stationary sliding ring 4 facing away from a sliding surface of the stationary sliding ring 4. To prevent the secondary seal 7 from falling out, a circumferential flange 4b ​​is provided. The circumferential flange 4b ​​also forms the axial termination at the end side of the stationary sliding ring 4 facing away from the sealing gap (see figure). Fig. 2 ).

[0035] Here, the first width B1 of the flange 4b ​​is smaller than the second width B2 of the circumferential groove 4a.

[0036] The secondary seal 7 is an O-ring with a square cross-section. This allows the O-ring to be positioned precisely in the circumferential groove 4a.

[0037] During operation, when the stationary sliding ring 4 performs movements in axial directions, the secondary seal 7 is moved together with the stationary sliding ring 4 in the axial direction.

[0038] The stationary sliding ring 4, as shown in Fig. 1 The figure shows a main area 41 and a secondary area 42. The sliding surface of the stationary sliding ring 4 is provided on the main area 41. The second bandage 40 is also arranged on the main area 41. The secondary seal 7 is arranged on the secondary area, which has a smaller radial thickness than the main area.

[0039] Furthermore, the main area 41 has a first outer diameter D5 and the secondary area 42 has a second outer diameter D6. The outer diameter D6 of the secondary area 42 is smaller than the first outer diameter D5 of the main area.

[0040] What's next? Fig. 2 As can be seen, flange 4b ​​has a third outer diameter D7, which is smaller than the second outer diameter D6. This creates a radial gap 70 on flange 4b. The medium to be sealed thus flows directly onto the secondary seal 7, which is pressurized during operation and deformed, resulting in an even better seal between the secondary seal 7 and the stationary component 14. The O-ring can also be compressed in the assembled state and partially deformed within the gap 70.

[0041] Furthermore, the first inner diameter D1 of the rotating sliding ring 3 is equal to the second inner diameter D2 of the stationary sliding ring 4. This prevents the presence of depressions, recesses, or similar features on the inner surface of the sliding ring seal assembly 2, through which the medium to be sealed flows, which would be difficult to clean or sterilize. The inner diameters D1 and D2 remain constant in the axial direction over the entire axial length of the rotating and stationary sliding rings 3 and 4.

[0042] A third inner diameter D3 of the stationary component 14 is slightly larger than the inner diameters D1 and D2. This ensures the axial mobility of the stationary sliding ring 4. A fourth inner diameter D4 of the rotating component 13 is again the same as the first and second inner diameters D1 and D2, so that there is no flow obstruction for the medium flowing in the flow direction 10 when it exits the mechanical seal assembly.

[0043] What's next? Fig. 1 As can be seen, an O-ring 8 is provided on a side of the rotating component 13 facing the rotating sliding ring 3, which seals a gap between the rotating component 13 and the rotating sliding ring 3 in the radial direction.

[0044] Thus, the mechanical seal assembly 1 according to the invention, with its internally pressurized mechanical seal 2, can be easily and thoroughly cleaned and sterilized. The transition at the different inner diameters D2 and D3 can also be cleaned easily and reliably, since the secondary region 42 of the stationary sliding ring 4 has a relatively small radial thickness. Furthermore, the step between the third inner diameter D3 and the second inner diameter D2 is also relatively small.

[0045] Fig. 3 Figure 1 shows a mechanical seal arrangement with an internally pressurized mechanical seal according to a second embodiment of the invention. The second embodiment corresponds essentially to the first embodiment, except that, unlike the first embodiment, the preloading device in the second embodiment comprises a circumferential wave spring 60. The circumferential wave spring 60 is arranged in a circumferential recess 14a in the stationary component 14. As in the first embodiment, the wave spring 60, as the preloading device, exerts a direct preload force only on the second bandage 40. Thus, the stationary sliding ring 4 is preloaded axially via the force-fit connection with the second bandage 40. Otherwise, this embodiment corresponds to the first embodiment, so reference can be made to the description given therein.

[0046] Fig. 4 Figure 1 shows a mechanical seal arrangement of an internally pressurized mechanical seal according to a third embodiment of the invention. The third embodiment corresponds essentially to the first embodiment and, like the first embodiment, has a preload device 6 comprising a plurality of cylindrical helical springs arranged along the circumference in recesses 14a of the stationary component 14. In contrast to the first embodiment, however, the plurality of helical springs are arranged such that the helical springs exert a preload force in the axial direction simultaneously on the bandage 40' and the stationary sliding ring 4 (see Figure 1). Fig. 4 This results in a particularly uniform force transmission into both the bandage 40' and the stationary sliding ring 4. As further explained below... Fig. 4 As can be seen, the bandages are designed with a substantially square cross-section. This places the centers of gravity S3 and S4 of bandages 30' and 40' closer to the central axis XX and thus also closer to the centers of gravity S1 and S2 of the stationary and rotating sliding ring. As further explained... Fig. 4 As can be seen, the short radial height of the bandages 30' and 40' allows for fixation by means of fixing pins 90 or fixing screws 91 such that bandages 30' and 30' have semi-open recesses, which can be designed as half-cylinders and / or half-ovals. Otherwise, this embodiment corresponds to the first embodiment, so reference can be made to the description given there.

[0047] As illustrated in the exemplary embodiments, a simply constructed mechanical seal assembly can thus be provided according to the invention, which enables sealing in a rotary feedthrough, particularly of foodstuffs such as water or beverages, or the like. Cleaning and sterilization of the mechanical seal assembly can also be carried out easily. Reference symbol list

[0048] 1 Mechanical seal assembly 2 Mechanical seal 3 Rotating sliding ring 3` Sealing surface of the rotating sliding ring 4 Stationary sliding ring 4' Sealing surface of the stationary sliding ring 4a Circumferential groove 4b Flange 5 Sealing gap 6 Preload device 7 Secondary seal 8 O-ring 9 Fixing device 10 Flow direction 11 Maximum radial thickness of the sliding rings 13 Rotating component 14 Stationary component 14a Recess 30, 30' First bandage 40,40' Second bandage 41 Main area of ​​the stationary sliding ring 42 Secondary area of ​​the stationary sliding ring 60 Circumferential wave spring 70 Intermediate space 90 Fixing pin 91 Fixing screws B1 Width of the flange B2 Width of the circumferential groove D1 Inner diameter of the rotating sliding ring D2 Inner diameter of the stationary sliding ring D3 Inner diameter of the stationary component D4 Inner diameter of the rotating component D5 Outer diameter of the main area 41 D6 Outer diameter of the secondary area 42 D7 Outer diameter at the flange H Radial height of the bandage S1 Center of gravity of the rotating sliding ring S2 Center of gravity of the stationary sliding ring S3 Center of gravity of the first bandage S4 Center of gravity of the second bandage X-X Center axis,

Claims

1. A mechanical seal arrangement comprising - a internally pressurised mechanical seal (2) having a rotating sliding ring (3) and a stationary sliding ring (4), which define a sealing gap (5) therebetween, - wherein at the sealing gap a first inner diameter (D1) of the rotating sliding ring (3) is equal to a second inner diameter (D2) of the stationary sliding ring (4), - a biasing device (6), which biases one of the sliding rings in axial direction (X-X) against the other of the sliding rings, and - a secondary seal (7), which moves in axial direction together with the axially biased sliding ring, wherein the secondary seal (7) is arranged at the axially biased sliding ring, wherein the biasing device is arranged at the mechanical seal (2), so that no contact with the medium to be sealed exists, - the mechanical seal arrangement comprises a first bandage (30) at the rotating sliding ring (3) and / or a second bandage (40) at the stationary sliding ring (4), characterised in that the axially biased sliding ring comprises a main portion (41) and a secondary portion (42) with a smaller outer diameter (D6) than the outer diameter (D5) of the main portion, and the secondary seal (7) is arranged at the secondary portion (42).

2. The mechanical seal arrangement according to claim 1, wherein the secondary seal (7) is arranged at a radially outwardly directed side of the axially biased sliding ring.

3. The mechanical seal arrangement according to claim 2, wherein the secondary seal (7) is arranged at an end side of the biased sliding ring facing away from the sliding surfaces of the biased sliding ring.

4. The mechanical seal arrangement according to one of the previous claims, wherein the first and / or second bandage (30, 40) is arranged at the rotating and / or stationary sliding ring (3, 4), so that a gravity centre (S3) of the first bandage (30) and a gravity centre (S1) of the rotating sliding ring (3) and / or a gravity centre (S4) of the second bandage (40) and a gravity centre (S2) of the stationary sliding ring (4) each lie in a common plane perpendicular to a central axis (X-X) of the mechanical seal arrangement.

5. The mechanical seal arrangement according to claim 3 or 4, wherein the biasing device is arranged exclusively at one of the bandages (30, 40).

6. The mechanical seal arrangement according to claim 5, wherein the biasing device (6) engages at a radially innermost portion of the bandage.

7. The mechanical seal arrangement according to claim 1, wherein the secondary seal (7) is arranged in a circumferential groove (4a) at the secondary portion (42) so that a flange (4b) forms an end portion of the axially biased sliding ring, wherein a first width (B1) of the flange (4b) is smaller than a second width (B2) of the circumferential groove (4a).

8. The mechanical seal arrangement according to claim 7, wherein the flange (4b) comprises a third diameter (D7), which is smaller than the outer diameter (D6) of the secondary portion (42), so that an intermediate space (70) is formed radially outwards on the flange (4b).

9. The mechanical seal arrangement according to one of claims 4 to 7, further comprising a fixing device (9), which is arranged at the first and / or second bandage (30, 40) to fix the bandage via fixing elements (90, 91).

10. The mechanical seal arrangement according to one of the preceding claims, wherein a first inner diameter (D1) of the rotating sliding ring (3) and a second inner diameter (D2) of the stationary sliding ring (4) are each constant in axial direction.

11. A rotary feedthrough of a food processing device comprising a mechanical seal arrangement (1) according to one of the preceding claims.