SELF-ALIGNING SEAL ASSEMBLY

Abstract

A seal assembly (10, 110) has an inner seal carrier (14, 114) with seals (16, 116, 18, 118), an outer carrier (30, 130) with inner curved surface (144) matching an outer curved surface (146) of the inner seal carrier for angular pitch adjustment of 3° to 5° for the inner seal carrier within the outer carrier, a flexible seal (36, 136) between the outer carrier and the bearing housing (28, 128), and oil within a cavity (20, 120) between the seals, preferably above atmospheric pressure. Shoulder bolts (140) allow lateral movement of the seal assembly with respect to the bearing housing. The seal assembly allows for misalignment and lack of parallelism of the shaft relative to the bearing housing whilst preventing contamination of the bearing.

Claims

1: A seal assembly for a rotatable shaft supported by a bearing in a bearing housing, the seal assembly including an inner seal carrier supporting seals for engagement with the shaft, the outer carrier supporting the inner seal carrier and having an inner curved surface, the inner seal carrier having an outer curved surface allowing angular positional adjustment of the inner seal carrier within the outer carrier, a flexible seal between the outer carrier and the bearing housing, and the seal assembly including oil within a cavity between the seals.

2: The seal assembly of claim 1, wherein the oil is within the cavity at a pressure at or above atmospheric pressure at the location of the seal assembly.

3: The seal assembly of claim 2, wherein the oil is at a pressure between atmospheric and about 1.0 bar above atmospheric.

4: The seal assembly of claim 3, wherein the oil is at a pressure between about 0.1 bar and about 0.8 bar.

5: The seal assembly of claim 4, wherein the inner seal carrier has at least one oil hole for filling oil and/or purging air from the cavity between the seals in the inner seal carrier.

6: The seal assembly of claim 5, wherein the at least one oil hole is sealed by at least one corresponding sealing means.

7: The seal assembly of claim 6, wherein the at least one sealing means includes a respective valve that retains pressure within the cavity and openable when pressure is applied externally to apply oil into the cavity or replenish oil into the cavity.

8: The seal assembly of claim 7, wherein the outer carrier including holes allowing the seal assembly to be sufficiently fastened by bolts to a face of the housing whilst allowing movement of the seal assembly for maintaining alignment with the shaft with the flexible seal maintaining sealing between the outer carrier and the housing.

9: The seal assembly of claim 8, wherein the holes are oversized in bore or diameter with respect to diameter of bolts used to fasten the outer carrier to the bearing housing.

10: The seal assembly of claim 9, wherein the bolts include shoulder bolts providing for sufficient fastening of the seal assembly to seal to the bearing housing via the flexible seal whilst allowing lateral movement of the seal assembly with respect to the bearing housing.

11: The seal assembly of claim 10, including a radial gap having a distance of about 1 mm to about 3 mm between the outer surface of the shaft of the bolt and the internal bore of the respective hole providing for lateral movement of the seal assembly mounting to the bearing housing.

12: The seal assembly of claim 11, the flexible seal having a thickness in a range from about 0.01 mm to about 5 mm.

13: The seal assembly of claim 12, wherein the inner seal carrier including at least one inner seal carrier seal provided around the curved outer surface of the inner seal carrier.

14: The seal assembly of claim 13, wherein the inner seal carrier seal is provided towards an outer face of the inner seal carrier.

15: The seal assembly of claim 14, wherein the inner seal carrier having up to about +/−5° angular freedom with respect to the centre of axis of rotation of the shaft within the outer carrier to accommodate for a lack of parallelism with respect to the shaft.

16: The seal assembly of claim 15, wherein the angular freedom of the inner seal carrier being about +/−4°.

17: The seal assembly of claim 16, wherein including a space between the inner seal carrier and the bearing housing allowing the inner seal carrier to pitch about the centreline of the shaft by up to a about +1-5° angular degrees without hitting the front face of the bearing housing or the flexible seal.

18: The seal assembly of claim 17, wherein the angular degrees of pitch are about +/−5°.

19: The seal assembly of claim 18, wherein the inner seal carrier includes a support for the seals and which extends inwardly towards the shaft and between the seals.

20: The seal assembly of claim 19, wherein the support supports the seals when the angular adjustment of the inner seal carrier relative to the outer carrier is at or beyond a threshold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 shows a front view of a seal assembly according to an embodiment of the present invention mounted to a bearing housing.

[0050] FIG. 2 shows a cross sectional view (A-A in FIG. 1) of the seal assembly of FIG. 1 mounted to the aforementioned bearing housing.

[0051] FIG. 3 shows a front view of a seal assembly according to an alternative embodiment of the present invention mounted to a bearing housing.

[0052] FIG. 4 shows a cross sectional view along A-A in FIG. 3.

[0053] FIG. 5 shows detail B identified in FIG. 4.

[0054] FIG. 6 shows a front view of a seal assembly according to an alternative embodiment of the present invention mounted to a bearing housing.

[0055] FIG. 7 shows a cross sectional view along C-C in FIG. 6.

[0056] FIG. 8 shows detail D identified in FIG. 7.

DESCRIPTION OF PREFERRED EMBODIMENT

[0057] A seal assembly 10 of the present invention has two key components: A seal carrier 12 and a pressurised oil sealing medium 14.

[0058] The seal carrier 12 locates, in use, two contact lip style oil seals 16, 18.

[0059] The cavity 20 between the two oil seals 16, 18 is filled with oil that is maintained under pressure.

[0060] The seal carrier 12 is alignable relative to a shaft 22 in order to maintain a positive seal with respect to the shaft 22, the shaft supported by a bearing 24 protected from contamination by the seal assembly 10.

[0061] The seal carrier 12 fulfils requirements to maintain a positive seal with respect the shaft 22. These requirements are: [0062] Misalignment in three (3) axes—vertical, horizontal and radial [0063] Parallelism with the shaft

[0064] The seal must accommodate these various (3 axes) misalignments whilst maintaining parallelism with the shaft.

[0065] The self-aligning pressurised oil seal embodying the present invention utilises pressurised oil as the sealing medium. It has the capacity to maintain parallel alignment with the shaft when the housing that it is mounted on is misaligned radially, vertically and horizontally.

[0066] The seal carrier of the seal assembly has the ability to misalign on a housing face 26 of a bearing housing 28 horizontally and vertically as well as maintaining parallelism with the shaft 22. The seal carrier includes an inner seal carrier 14 and an outer carrier 30. The inner seal carrier can adjust alignment radially within the outer carrier 30.

[0067] As shown in the embodiment in FIG. 1, the seal assembly 10 has three primary components:

1. An outer carrier 30, such as arranged to mount to a housing face 26 of a bearing housing 28;
2. An inner seal carrier 14;

3. Oil Seals 16, 18

[0068] Holes 32 within the inner seal carrier 14 allow for oil filling and air purging. The holes are required for:

1. filling the void/cavity 20 between seals 16, 18;
2. purging air from the void/cavity 20;
3. attaching pressurised oil source to pressurise the oil within the void.

[0069] FIG. 2 shows a cross sectional view A-A through the bearing housing, bearing, shaft and seal assembly shown in FIG. 1.

[0070] During operation, the shaft 22 may not maintain parallelism with the housing 28 and so the entire seal assembly 10 is able to move with respect to the housing (vertically and horizontally).

[0071] Furthermore, the shaft 22 can axially misalign about the centre line C of the bearing 24.

[0072] To maintain seal parallelism with respect to the shaft 22 during this misalignment, the alignable inner seal carrier 14 moves within the outer carrier 30.

[0073] The seal assembly 10 is sealed to the housing 28 with a flexible seal 36. The flexible seal 36 allows for the relative movement between the bearing housing 28 and the seal assembly 10 and resists contamination ingress at the interface between the bearing housing 28 and the seal assembly 10.

[0074] To allow for the relative movement of the seal assembly and bearing housing, mounting holes 34 for the mounting bolts 40 are machined oversized.

[0075] The bolts are tightened (or spaced) to allow for adequate sealing force between the bearing housing and the seal assembly.

[0076] Operation—Sealing Medium: For the seal assembly in use, the oil seal cavity 20 is filled with an oil. The viscosity grade of the oil can vary depending upon the application for the seal assembly 10.

[0077] The oil within the cavity is pressurised to a minimum 0.5 Bar (50 kPa) above atmospheric pressure. Any material attempting to breach the seal will be forced out along with a small quantity of oil. This oil pressure will vary depending on the application.

[0078] The seal assembly utilises its own oil reservoir to maintain pressure whilst lubricating lip faces of the seals sealing the shaft. Depending on the application, this oil pressure could also be sourced from the equipment using the oil.

[0079] The present invention utilises pressurised oil between the oil seals 16, 18 to maintain a contamination barrier from the item requiring sealing on a rotatable shaft.

[0080] As shown in FIGS. 3 to 5, a seal assembly 110 includes a seal carrier 112 including an inner carrier 114.

[0081] The inner seal carrier supports therein at least two seals 116, 118 which respectively contact a shaft 122.

[0082] The inner seal carrier is retained within an outer carrier 130.

[0083] Holes 134 can be oversized in their diameter/bore with respect to bolts 140. This provides for a constrained amount of lateral freedom (13) of the seal assembly with respect to the bearing housing. For example, the seal assembly can move upwards or sideways (i.e. laterally) across the face of the bearing housing.

[0084] The inner seal carrier can angularly adjust in pitch by an angular amount of degrees (a) with respect to the centreline of the shaft to accommodate a misalignment in parallelism of the shaft with respect to the outer carrier and/or bearing housing.

[0085] It will be appreciated that, as one portion of the inner seal carrier adjusts towards the bearing housing (reducing the clearance between the bearing housing and the inner seal carrier) another (opposite) portion of the annular inner seal carrier moves away from the bearing housing.

[0086] The bolts 140 are preferably shoulder bolts providing limited fastening depth into the bearing housing due to the shoulder 142.

[0087] The inner surface 144 of the outer carrier and the outer surface 146 of the inner seal carrier outer surface can have matching curvature with respect to the centre of axis of rotation of the shaft, such as matching radius of curvature.

[0088] An interface seal 148 (such as a circle or rectilinear cross section O-ring seal) can be provided on the outer surface of the inner seal carrier to interface seal against contamination between the inner seal carrier and the outer carrier. The interface seal acts to wipe clean the inner surface of the outer carrier when angular adjustment occurs and prevent contamination (dirt, dust and water) ingressing into the seal between the inner and outer surfaces 144, 146 of the respective carriers.

[0089] A support 150 is provided within the inner seal carrier 114. The support can support the seals 116, 118. The support 150 may be provided as a spine extending around the internal periphery of the inner seal carrier. The seal assembly according to one or more forms of the present invention can adjust/accommodate for misalignment between the seals and the shaft but only to a limit of the angular adjustment and lateral adjustment. The support 150 (such as an inner spine) prevents excessive load and excessive misalignment angle of the seals 116, 118 (such as lip seals) and thus prevents failure of the seal assembly from excessive adjustment.

[0090] A head 152 of the bolt 140 can include a head shoulder 154 that applies a compressive force to the outer carrier 130 sufficient to compress the flexible seal 136 between the outer carrier and the bearing housing to prevent contamination entering the seal assembly from that interface.

[0091] In the case of shoulder bolts or similar, the shoulder prevents the respective bolt tightening further than the limited length of the thread extending beyond the shoulder. Consequently, with the flexible seal of desired thickness in place, the bolts can sufficiently tighten to compress the flexible seal and prevent ingress of contamination whilst allowing some lateral movement within the limits of the radial spacing between the shank of each bolt 140 and the inner bore of each respective hole 134.

[0092] At least one sealing means 164 plugs a passageway 166 to the cavity 120 to retain oil within the inner seal carrier 114. One or more galleries 162 can be provided from the passageway to feed the cavity 120.

[0093] The support 150 can have at least one aperture 168 therethrough to allow for oil flow/pressure between the two seals 116, 118.

[0094] The sealing means 164 can include a valve to retain oil pressure within the seal assembly but allow refiling with oil when required.

[0095] A space 160 between the inner seal carrier 114 and the bearing housing 128 allows a portion of the inner seal carrier to have the angular freedom to pitch about the centreline of the shaft by a few degrees towards the bearing housing (preferably about +/−5°, more preferably about)+/−3° without hitting the front face 170 of the bearing housing or the flexible seal 136.