Pressure-activated, contactless seals and seal assemblies

Abstract

Pressure-activated, contactless seals and seal assemblies A pressure-activated, contactless seal for sealing against a rotating cylindrical surface located between a high-pressure region and a low-pressure region includes a seal member carrier spaced from the rotating surface and defining a seal member chamber in fluid communication with the high-pressure region. The seal member is supported on the seal member carrier for radial movement. A secondary seal is mounted between a face of the seal member and a face of the seal member chamber to provide a pressure barrier around the seal member. The seal member includes a sidewall extending toward the rotating surface, defining a seal cavity. An end of the sidewall defines a contactless seal surface. The seal member further includes a bleed port extending between the seal cavity and the seal member chamber on the high-pressure side of the secondary seal. In use, high pressure within the seal member chamber urges the seal member toward the rotating surface until it is forced out until it equilibrates with the pressure within the seal cavity, and the contactless seal surface maintains a contactless sealing relationship with the rotating surface. The seal assembly includes multiple seals circumferentially arranged around the rotating surface.

Description

[Technical Field] 【0001】 The present invention relates to seals and seal assemblies. In particular, the present invention relates to pressure-activated, contactless seals. The present invention also relates to seal assemblies including an arrangement of multiple seals. [Background technology] 【0002】 Seals can be used to provide a pressure barrier around a rotating shaft, such as the shaft of a turbine. In turbines, such as gas turbines, it is often necessary to have a shaft that passes through regions of different fluid pressure, and seals are provided to maintain the pressure in these regions. One form of seal is a brush seal, in which bundled filaments extend between the seal and the rotating shaft, maintaining a small gap so that a pressure barrier is maintained. As the filaments wear, the seal performance deteriorates, and eventually the seal must be replaced. 【0003】 Wear is a problem for all forms of contact seals. Summary of the Invention [Problem to be solved by the invention] 【0004】 It is an object of the present invention to provide a contactless seal, i.e., a seal that maintains a gap between the seal and the shaft small enough to allow rotation while still providing an adequate pressure barrier. It is also desirable that the seal be pressure activated, i.e., the seal is formed when pressure across the seal rises to a predetermined level. [Means for solving the problem] 【0005】 A first aspect of the present invention includes a pressure-activated, contactless seal for sealing between high-pressure and low-pressure regions relative to a rotating cylindrical surface, e.g., the outer periphery of a rotating shaft. The contactless seal includes a seal member carrier positioned radially from the rotating cylindrical surface and defining a seal member chamber in fluid communication with the high-pressure region; a seal member supported by the seal member carrier for movement radially relative to the rotating cylindrical surface and having a contactless sealing surface adjacent the rotating cylindrical surface; and a secondary seal attached between a surface of the seal member facing the seal member carrier, e.g., the outer surface of the seal member, and an opposite surface, e.g., the inner surface, of the seal member chamber, providing a pressure barrier around the seal member between the high-pressure and low-pressure regions. The seal member includes side walls extending radially toward the rotating cylindrical surface, which define a seal cavity, and an end, e.g., a radially inner end, which defines a contactless sealing surface adjacent the rotating cylindrical surface. The seal member further includes a bleed port connecting the seal cavity and the seal member chamber, the port being located outside the seal member on the high-pressure side of the secondary seal. In use, high pressure within the seal member chamber axially biases the seal member, forcing it out until balanced by pressure within the seal cavity, causing the non-contacting seal face to maintain a non-contacting sealing relationship with the shaft. 【0006】 The rotating cylindrical surface may be the outer surface of a rotating shaft or cylinder, or the inner surface of a rotating hollow cylinder or hollow shaft. 【0007】 During use, the high pressure in the seal member chamber presses the seal member against the rotating cylindrical surface, bringing the seal face closer to the rotating cylindrical surface. The pressure in the seal cavity also increases due to pressure transmission through the bleed port, and the pressure in the seal cavity balances with the pressure in the seal member chamber, maintaining the seal face away from the rotating cylindrical surface. 【0008】 The seal member side walls can be located at both ends of the seal member (i.e., the high-pressure end and the low-pressure end), and one or more intermediate walls can be located between the side walls to form multiple seal cavities. The seal can further include bleed ports extending around the seal member on the high-pressure side of the secondary seal, connecting each seal cavity to the seal member chamber. The sealing behavior of the seal can be adjusted by selecting the sizes of the seal cavities and bleed ports. 【0009】 The secondary seal may be attached to the seal member and configured to be biased (i.e., outwardly biased) against an opposing wall, e.g., an inner wall of the seal member chamber, or the secondary seal may be attached to a wall of the seal member chamber and configured to be biased (i.e., inwardly biased) against an opposing wall, e.g., an outer surface of the seal member that faces the seal member carrier. 【0010】 The secondary seal may be located at a location between the high pressure and low pressure ends of the seal member, the exact location determining the area of ​​the seal member's exterior surface exposed to high pressure. 【0011】 The face of the seal member facing the seal member carrier may extend radially to form an axially facing face portion, and the opposing face of the seal member chamber may also have a corresponding axially facing face portion, and the secondary seal may be mounted between these two axially facing faces. 【0012】 The seal member carrier may be disposed at the low-pressure end and include an axially extending end wall facing the axis, such that the low-pressure end of the seal member abuts the end wall, thereby resisting axial movement of the seal member due to a pressure drop across the seal. 【0013】 The end wall may have a pocket formed toward the low-pressure end of the seal member carrier, and the pocket may be in pressure communication with a seal member chamber exterior to the seal member on the high-pressure side of the secondary seal. A pressure port may extend between the pocket and the seal member chamber exterior to the seal member on the high-pressure side of the secondary seal, or between the pocket and a seal cavity extending through a bleed port to the seal member chamber exterior to the high-pressure side of the secondary seal. The end wall of the seal member carrier and the low-pressure end of the seal member may be axially spaced from the non-contacting seal surface. 【0014】 Alternatively, the seal member carrier may include an end wall disposed at the high pressure end and extending toward the rotating cylindrical surface, and a leaf spring may extend between the end wall and the high pressure end of the seal member to resist axial loads resulting from pressure drop across the seal and to guide movement of the seal member. 【0015】 The leaf spring may include a pair of radially spaced apart leaf springs. 【0016】 A second aspect of the present invention involves a seal assembly including a plurality of seals circumferentially disposed about a rotating cylindrical surface. 【0017】 The seal assembly may further include a seal carrier, and each seal may include a formation that engages a corresponding formation on the seal carrier to resist rotational movement of the seal, thereby helping to prevent the seal from rotating with the rotating cylindrical surface. 【0018】 The seal assembly may further include a spring, such as a coil spring or a leaf spring, disposed between adjacent seals and configured to urge them apart, thereby urging the seals away from the rotating cylindrical surface when not actuated by high pressure. 【0019】 The edges of adjacent seals may be stepped so that the stepped edges engage with each other to prevent a direct path between adjacent seals. The steps may be radial and / or axial. 【0020】 Further aspects of the invention are described below with reference to the drawings. [Brief explanation of the drawings] 【0021】 [Figure 1] FIG. 1 shows a first embodiment of the seal in an unactuated and actuated state. [Figure 2] FIG. 2 shows a first embodiment of the seal in an unactuated and actuated state. 【0022】 [Figure 3] FIG. 3 shows an alternative configuration of the seal member for the embodiment of FIGS. [Figure 4] FIG. 4 shows an alternative configuration of the seal member for the embodiment of FIGS. 【0023】 [Figure 5] FIG. 5 shows yet another form of seal member for the embodiment of FIGS. [Figure 6] FIG. 6 shows yet another form of seal member for the embodiment of FIGS. 【0024】 [Figure 7] FIG. 7 shows yet another form of seal member for the embodiment of FIGS. [Figure 8] FIG. 8 shows yet another form of seal member for the embodiment of FIGS. 【0025】 [Figure 9] FIG. 9 shows an end view of the seal member shown in FIG. 7 or FIG. 【0026】 [Figure 10]FIG. 10 shows a portion of a seal assembly according to the present invention. 【0027】 [Figure 11] FIG. 11 shows an alternative embodiment of the seal assembly of FIG. [Figure 12] FIG. 12 shows an alternative embodiment of the seal assembly of FIG. 【0028】 [Figure 13] FIG. 13 shows a partial axial and radial view of adjacent seals in a seal assembly. [Figure 14] FIG. 14 shows a partial axial and radial view of adjacent seals in a seal assembly. 【0029】 [Figure 15] FIG. 15 shows a second embodiment of the seal in an unactuated and actuated state. [Figure 16] FIG. 16 shows a second embodiment of the seal in an unactuated and actuated state. 【0030】 [Figure 17] FIG. 17 shows an alternative to the embodiment of FIGS. [Figure 18] FIG. 18 shows an alternative to the embodiment of FIGS. 【0031】 [Figure 19] FIG. 19 shows a detail of the embodiment of FIGS. 【0032】 [Figure 20] FIG. 20 shows a variation of the seal type shown in FIGS. 【0033】 [Figure 21] FIG. 21 shows a modification corresponding to FIG. 20 to the type of seal shown in FIGS. 【0034】 [Figure 22] FIG. 22 shows a portion of an embodiment of a seal member. [Figure 23] FIG. 23 shows a portion of an embodiment of a seal member. 【0035】 [Figure 24] FIG. 24 shows a modification of the embodiment of FIG. 【0036】 [Figure 25] FIG. 25 shows a further variation of FIG. DETAILED DESCRIPTION OF THE INVENTION 【0037】 The seal shown in FIGS. 1 and 2 is a cross-section of a seal used on a rotating cylindrical shaft 10 that extends through a gas turbine between a high-pressure region HP and a low-pressure region LP and rotates about axis XX. The seal includes a seal member carrier 12 spaced from the shaft 10. An inner portion of the seal member carrier 12 defines a seal member chamber 14. The low-pressure end of the seal member carrier 12 has an end wall 16 that extends toward the shaft 10. The inner wall of the seal member chamber 14 has a locating groove 18 within which an inwardly biased secondary seal ring 20 is mounted. FIG. 2 shows an embodiment in which the seal member carrier 12 is constructed from two pieces for ease of assembly, and in this case, the groove 18 may be formed at the interface between the pieces. 【0038】 The seal member 22 is disposed within the seal member chamber 14 so as to be movable in the radial direction rr. The secondary seal ring 20 is biased against an outer surface 24 of the seal member 22 facing the seal member carrier 12, forming a pressure barrier across the seal member chamber 14. The seal member carrier 12 is open to high-pressure fluid at one end 26 and to low-pressure fluid at the other end 28. Thus, the seal member chamber 14 has a high-pressure zone on the high-pressure side of the secondary seal 20 and a low-pressure zone on the low-pressure side. 【0039】 The seal member 22 has end walls 30, 32 extending toward the axis 10. Intermediate walls 34, 36 are disposed between the end walls 30, 32 and are generally parallel to the end walls 30, 32. Ends 38, 40, 42, 44 of the end walls 30, 32 and intermediate walls 34, 36 are flush with one another and define non-contacting sealing surfaces. The end walls 30, 32 and intermediate walls 34, 36 form seal cavities 46, 48, 50. 【0040】 Each cavity 46, 48, 50 communicates with the high pressure zone of the seal member chamber 14 through a corresponding bleed port 52, 54, 56, respectively. 【0041】 In use, the seal is in the configuration shown in FIG. 1 due to the action of the mounting springs (described below). Pressure builds up at the high-pressure end HP. While the spaces between the ends 38, 40, 42, and 44 and between the bleed ports 52, 54, and 56 allow fluid to pass through the seal, the size of these spaces and ports is small enough to create resistance to fluid flow, resulting in a pressure drop. Due to this pressure drop, high pressure acting on the outer surface of the seal member 22 pushes the seal member toward the shaft 10, reducing the spacing between the ends 38, 40, 42, and 44 and the outer surface of the shaft 10. Fluid continues to flow through the bleed ports 52, 54, and 56 into the cavities 46, 48, and 50, but the proximity of the ends 38, 40, 42, and 44 to the cylindrical outer surface 11 of the shaft 10 causes the pressure in the cavities 46, 48, and 50 to build up and balance with the pressure in the high-pressure zone acting on the outer surface of the seal member 22. At this point (FIG. 2), ends 38, 40, 42, 44 are spaced a very small distance from shaft 10, so they are not in contact, but still maintain enough resistance to fluid flow to maintain a pressure differential across the seal. The seal is self-adjusting; if the space between ends 38, 40, 42, 44 becomes too small, the pressure in cavities 46, 48, 50 will rise, lifting seal member 22 off the shaft, causing the increased spacing to reduce pressure. 【0042】 The end wall 16 of the seal member carrier, by abutting the low pressure end wall 32 of the seal member 22, prevents axial movement of the seal member 22 due to pressure drop across the seal. 【0043】 In the embodiment of Figures 1 and 2, there are three cavities of approximately equal size. In other embodiments, the number and relative sizes of the cavities can vary. Figure 3 shows an embodiment in which the seal member 22a has one intermediate wall 58 and two cavities 60, 62. In this case, the intermediate wall 58 is located at the low-pressure end of the seal member 22a, and the cavities are unequal in size. Also, instead of the groove 18 and inward-spring seal 20 in the seal member carrier 12, the outer surface of the seal member 22a has a groove 64 with an outwardly biased seal ring 66 that engages the inner wall of the seal member carrier chamber 14. 【0044】 Figure 4 shows an alternative seal member 22b for use with the embodiment of Figure 3. In this case, there is no intermediate wall and only a single cavity 68 is formed. 【0045】 It is not necessary to provide a bleed port for each cavity, nor are the bleed ports necessarily of identical size. The number and relative sizes of cavities and bleed ports can be adjusted as required. 【0046】 The location of the secondary seal between the ends of the seal member carrier chamber defines the size of the high pressure zone and therefore the force applied to the seal member 22 . 【0047】 FIG. 5 illustrates another embodiment similar to FIG. 2. As is conventional, the seal member carrier end wall 16 abuts the low-pressure end wall 32 of the seal member 22 to prevent axial movement of the seal member 22 due to a pressure drop across the seal. In use, friction between the end walls 16, 32 can prevent free movement of the seal member 22. In the embodiment of FIG. 5, the seal member end wall 32 is provided with a pressure balance pocket 70 facing the seal member carrier end wall 16. This pressure balance pocket 70 is connected to the high-pressure zone of the carrier chamber 14 via a pressure balance supply port 72. This reduces friction between the contacting surfaces when the seal is under pressure. 【0048】 6 shows an alternative configuration of the seal member 22 in which the pressure balance supply port 72 is replaced by an end wall port 74 connecting the pressure balance pocket 70 to the adjacent cavity 50, which in turn is connected to the high pressure zone of the carrier chamber 14 via the bleed supply port 56. 【0049】 Figures 7 and 8 show further variations of the seal member 22 shown in Figures 5 and 6. In each case, the seal member end wall 32 is replaced with an enlarged end wall 76, thereby creating an enlarged pressure balance pocket 78 having approximately the same area as the upstream end wall 30 of the seal member 22. The enlarged pressure balance pocket 78 is connected to the high-pressure zone by a pressure balance supply port 72 or end wall port 74 that connects the pressure balance pocket 70 to the adjacent cavity 50 and, via the bleed supply port 56, to the high-pressure zone of the carrier chamber 14. 【0050】 5-8 show only one pressure balance supply port 72 or end wall port 74, but multiple ports may be provided. Figure 9 shows an end view of seal member 22 with two pressure balance supply ports 72 opening into an enlarged pressure balance pocket 78. 【0051】 The present invention also provides a seal assembly, as partially shown in Figure 10. The seal described above is intended to be mounted about a rotating shaft by using a plurality of arcuate seal segments 100, 102, 104. Each segment includes any of the seals described above and is retained circumferentially about the shaft by a seal carrier 106. Each seal has a lug 108 that engages in a slot 110 in the seal carrier 106. The interengagement of these formations prevents the seal from rotating with the shaft. 【0052】 To maintain the seals away from the shaft upon actuation, adjacent seals 100, 102, 104 are provided with springs that push them apart. These springs may be coil springs 112 (FIG. 11) or fork / leaf springs 114 (FIG. 12). 【0053】 To prevent leakage through gaps between adjacent seals 100, 102, 104, the seal edges may be provided with interlocking stepped features. The stepped features may be radially 116 as shown in FIG. 13 or axially 118 as shown in FIG. 14. 【0054】 Figures 15 and 16 illustrate a second embodiment of a seal according to the present invention. In this embodiment, a seal member 170 has a configuration generally similar to that of Figure 1, but a seal member carrier 172 has a different configuration. A low-pressure end 174 of the seal member carrier 172 includes a groove 176 for mounting an inwardly biased secondary seal ring 178. A high-pressure end 180 of the seal member carrier 172 is spaced from a high-pressure end 182 of the seal member 170. A pair of leaf springs 184, 186 extend within a seal member carrier chamber 188 between the high-pressure end 180 of the carrier 172 and the high-pressure end 182 of the seal member 170. The leaf springs 184, 186 are radially spaced apart. 【0055】 The leaf springs 184, 186 resist axial loads acting on the seal member 170 and allow controllable radial movement of the seal member 170 when actuated by high pressure, keeping it parallel to the shaft surface (see FIG. 16). 【0056】 Figures 17 and 18 show an alternative embodiment to that shown in Figures 15 and 16. In this embodiment, instead of groove 176 and inwardly biased secondary seal ring 178 in carrier 172, a groove 190 in the outer surface of seal member 170a is fitted with an outwardly biased secondary seal ring 192 which acts against the inner surface of the low pressure end of carrier 172. 【0057】 As will be described in more detail below, seal member 170 has an arcuate shape. Figure 19 shows leaf springs 184, 186 attached to seal member 170. Leaf springs 184, 186 are planar and act only in a single plane. 【0058】 Figure 20 shows a variation of the seal type shown in Figures 1-8. In this embodiment, a low-pressure end 215 of a seal member chamber 214 and an end 223 of a corresponding seal member 222 extend radially away from an axis (not shown). A secondary seal ring 220 is disposed within the wall of the extended end 215 of the seal member chamber 214 and is configured to extend axially and seal against a corresponding axial surface 224 of the extended end 223 of the seal member 222. The secondary seal ring 220 may be biased against the axial surface 224 by a spring element (not shown). The seal member chamber 214 is still open to the low-pressure fluid at an end 228. 【0059】 Figure 21 shows a variation corresponding to Figure 20, but adapted for a seal of the type shown in Figures 15-18. In this embodiment, a groove 276 in the low-pressure end 274 of the seal member carrier 272 extends axially. The low-pressure end 271 of the seal member 270 extends radially outward from the axis 210, such that a secondary seal ring 278 in the groove 276 seals against the axial face of the end 271 of the seal member 270. Again, a spring element (not shown) may be provided to bias the secondary seal ring 278 against the end 271. 【0060】 The variations shown in Figures 20 and 21 may be useful in large diameter seals where the radially extending rings become too large to be properly installed. 【0061】 22 and 23 illustrate a portion of an embodiment of a seal member 322 that may be used as seal member 222 of FIG. 20 or seal member 270 of FIG. 21. The edge of seal member 322 is provided with a multi-tiered, interlocking configuration consisting of notches 316 and corresponding protrusions 318. In use, the protrusions 318 of one seal member 322 engage with the corresponding notches 316 of an adjacent seal member 322. This engagement helps seal the gap between adjacent seal members 322. Additionally, the secondary seal ring 220 or 278 may seal against a portion 317 of seal member 322 that is located above notch 316, further enhancing the sealing effect. 【0062】 FIG. 24 shows a variation of the embodiment of FIG. 20. In this embodiment, the seal member end wall 432 and seal member carrier end wall 416, which have pressure balance pockets 470, extend axially outward from the seal member 422 and shaft 410. This allows the areas of the seal member end wall 432 and pressure balance pockets 470 to match without interference from the seal member 422 or shaft 410. This also allows the centers of pressure in the high-pressure zone and the low-pressure zone to remain approximately the same, reducing torsional moments on the seal that can occur when the centers of pressure are not aligned. This variation is also applicable to the embodiments of FIGS. 1-8. 【0063】 FIG. 25 illustrates yet another variation of FIG. 20 . While in the previous embodiments the seal acts against the outer circumferential surface of the rotating shaft, in the embodiment of FIG. 25 the seal acts against the inner surface of a rotating cylinder or hollow shaft 510, forming a pressure barrier within the cylinder. In this configuration, the basic components are similar, with a groove 576 in the low-pressure end 574 of a seal member carrier 572 extending axially. A low-pressure end 571 of a seal member 570 extends radially outward from the cylinder 510, with a secondary seal ring 578 in groove 576 sealing against the axial surface of end 571 of seal member 570. Again, a spring element (not shown) can be provided to urge secondary seal ring 578 against end 571. All of the other embodiments described above can be implemented in this “inverted configuration” with appropriate modifications. 【0064】 Further modifications can be made within the scope of the invention.

Claims

[Claim 1] A pressure-operated non-contact seal for sealing a rotating cylindrical surface between a high-pressure region and a low-pressure region, A seal member carrier is positioned radially apart from the rotating cylindrical surface and defines a seal member chamber that is in fluid communication with the high-pressure region, A seal member is supported by a seal member carrier so as to be movable in the radial direction of a rotating cylindrical surface, and has a non-contact seal surface adjacent to the rotating cylindrical surface, A secondary seal is installed between the surface of the sealing member facing the sealing member carrier and the surface opposite the sealing member chamber, providing a pressure barrier around the sealing member between the high-pressure region and the low-pressure region. Equipped with, The sealing member extends radially toward the rotating cylindrical surface and has side walls that define a seal cavity, and the end of the side wall adjacent to the rotating cylindrical surface defines a non-contact sealing surface. The sealing member further comprises a seal cavity and a bleed port extending between the seal member chamber on the high-pressure side of the secondary seal. During use, the high pressure within the seal member chamber presses the sealing member toward the rotating cylindrical surface, pushing it out until it is balanced by the pressure within the seal cavity, so that the non-contact sealing surface maintains a non-contact sealing relationship with the rotating cylindrical surface. seal. [Claim 2] The rotating cylindrical surface is the axis of rotation, the outer surface of the cylinder, or the inner surface of the rotating cylinder. The seal according to claim 1. [Claim 3] The side walls of the sealing member are located at both ends of the sealing member, and one or more intermediate walls are arranged between the side walls to define a plurality of sealing cavities. The seal according to claim 1 or 2. [Claim 4] Each seal cavity further comprises a bleed port extending between the seal member chamber surrounding the seal member on the high-pressure side of the secondary seal. The seal according to claim 3. [Claim 5] The secondary seal is attached to the sealing member and is biased toward the opposing wall of the sealing member chamber. The seal according to claim 1. [Claim 6] The secondary seal is attached to the opposing wall of the seal member chamber and is biased toward the surface of the seal member facing the seal member carrier. The seal according to claim 1. [Claim 7] The secondary seal is positioned between the high-pressure end and the low-pressure end of the sealing member. The seal according to claim 1. [Claim 8] The surface of the sealing member facing the sealing member carrier extends radially and defines a surface portion facing axially, and the opposing surface of the sealing member chamber has a corresponding surface portion facing axially, and the secondary seal is mounted between these two axially facing surfaces. The seal according to claim 1. [Claim 9] The seal member carrier is positioned at the low-pressure end and includes an end wall extending axially, such that the low-pressure end of the seal member abuts against the end wall. The seal according to claim 1. [Claim 10] The end wall has a pocket formed toward the low-pressure end of the seal member carrier, and the pocket is in pressure communication with the seal member chamber on the outside of the seal member on the high-pressure side of the secondary seal. The seal according to claim 9. [Claim 11] A pressure port is provided between the pocket and the seal member chamber surrounding the seal member on the high-pressure side of the secondary seal, or between the pocket and a seal cavity having a bleed port extending into the seal member chamber surrounding the seal member. The seal according to claim 10. [Claim 12] The end wall of the seal member carrier and the low-pressure end of the seal member are spaced apart in the axial direction from the non-contact sealing surface. The seal according to any one of claims 9 to 11. [Claim 13] The seal member carrier is located at the high-pressure end and has an end wall extending toward the rotating cylindrical surface, with a leaf spring extending between the end wall and the high-pressure end of the seal member. The seal according to claim 1. [Claim 14] The leaf spring includes a pair of leaf springs spaced apart in the radial direction. The seal according to claim 13. [Claim 15] The plurality of seals according to claim 1 are arranged circumferentially around the rotating cylindrical surface, Seal assembly. [Claim 16] Furthermore, the seal carrier is provided, and each seal includes a forming portion that engages with a corresponding forming portion on the seal carrier to resist the rotational movement of the seal. The seal assembly according to claim 15. [Claim 17] It further comprises a spring positioned between adjacent seals and configured to push them apart from one another. The seal assembly according to claim 15 or 16. [Claim 18] The edges of adjacent seals are formed with a stepped shape, and these stepped edges engage with each other to prevent a direct path from extending between adjacent seals. The seal assembly according to claim 15. [Claim 19] The step of the stepped end is formed in the radial and / or axial direction. The seal assembly according to claim 18.

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