REINFORCED SEAL FOR ROTARY SHAFTS

- AKTIEBOLAGET SKF

A seal for sealing a space between a housing and a rotatable shaft disposed within the housing includes an annular, elastomeric seal body disposeable about the shaft. The body has a central axis, an outer portion disposeable within a housing recess, and an inner portion with a lip engageable with the shaft. At least a portion of the seal body is configured to bendingly deflect when fluid pressure exerted on the body exceeds a predetermined value such that at least a section of the body inner portion displaces radially outwardly to permit fluid flow between the shaft and the seal body. A rigid support member is disposed within the body outer portion so as to be located at least partially within the housing recess and is configured to reduce bending deflection of the body inner portion so as to prevent disengagement of the body from the recess.

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Description

The present invention relates to seals, and more particularly to seals for retaining grease within bearings.

Seals for sealing about rotatable shafts are generally known and may be formed of various known constructions. FIG. 1 depicts one such type of seal that includes a seal body having a lip sized to engage the shaft with an interference fit, such that no biasing member (e.g., a garter spring) is required to maintain contact with the shaft. The seal has an outer portion disposed within a groove of a static housing so as to secure the seal. Such a seal is often used to retain grease or other lubricant within a bearing and may experience a relatively high pressure under certain conditions, such as excessive lubrication.

In order to reduce excessive pressure, these seals have been designed to bend or deflect by means of the pressure so as to move the lip off of the shaft to thereby release a portion of the grease or other lubricant. However, with many such known seal assemblies, the elevated pressure may deflect/bend the seal body to such an extent that the portion of the seal body disposed in the housing groove is pulled radially inwardly so as to be disengaged from the groove, as shown in FIG. 1B, thus preventing proper functioning of the seal.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a seal for sealing a space between a housing and a rotatable shaft disposed at least partially within the housing, the housing having an annular recess and the shaft having an outer surface. The seal comprises a generally annular, elastomeric seal body disposeable about the shaft, the body having a central axis, a radially outer portion disposeable at least partially within the housing recess so as to couple the seal with the housing, and a radially inner portion with a lip sealingly engageable with the shaft outer surface. At least a portion of the seal body is configured to bendingly deflect when fluid pressure exerted on the body exceeds a predetermined value such that at least a section of the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the seal body. Further, at least one generally rigid support member is disposed within the body outer portion so as to be located at least partially within the housing recess when the seal is coupled with the housing, the support member being configured to at least reduce bending deflection of the body inner portion so as to prevent disengagement of the body from the recess.

In another aspect, the present invention is a shaft assembly comprising a housing having an inner circumferential surface defining a central bore and a recess extending generally radially outwardly from the inner surface, a rotatable shaft disposed within the housing bore such that a generally annular space is defined between the shaft and the housing inner surface, and a bearing disposed within the housing and configured to rotatably support the shaft, the bearing containing a lubricant fluid. A seal is configured to seal the annular space and includes generally annular, elastomeric seal body with a central axis and at least one generally rigid support member disposed within the body. The seal body is disposeable about the shaft and has a radially outer portion disposed at least partially within the housing recess and a radially inner portion with a lip sealingly engaged with the shaft outer surface. The seal body is configured to bendingly deflect when fluid pressure on the body exceeds a predetermined value such that the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the body. Further, the at least one support member is disposed within the seal body outer portion so as to be located at least partially within the housing recess and configured to at least reduce bending deflection of the body inner portion to prevent disengagement of the seal body from the recess.

In a further aspect, the present invention is again a seal for sealing a space between a housing and a rotatable shaft disposed at least partially within the housing, the housing having an annular recess and the shaft having an outer surface. The seal comprises a generally annular, elastomeric seal body disposeable about the shaft, the seal body having a central axis, a radially outer portion disposeable at least partially within the housing recess so as to couple the seal with the housing, and a radially inner portion with a lip sealingly engageable with the shaft outer surface. The seal body is configured to bendingly deflect when pressure on the body exceeds a predetermined value such that at least a section of the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the seal body. Further, the body has a high pressure axial end exposable to a relatively higher fluid pressure and an opposing, low pressure axial end exposable to a relatively lower fluid pressure. At least one generally rigid support member is disposed within the seal body outer portion so as to be located at least partially within the housing recess when the seal is coupled with the housing. The support member includes a generally annular body with an axial portion and a radial portion extending radially-inwardly with respect to the axial portion. Furthermore, the support member is arranged within the seal body outer portion such that support member radial portion is disposed at least generally adjacent to the seal body high pressure end and the support member axial portion extends generally axially from the radial portion in a direction generally toward the seal body low pressure end.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIGS. 1A and 1B, collectively FIG. 1 are each an axial cross-sectional view of an upper portion of a prior art seal assembly, FIG. 1A showing the seal under normal pressure conditions and FIG. 1B showing the seal when bended under elevated pressure;

FIG. 2 is a partly broken away, axial cross-sectional view of a shaft assembly including a seal in accordance with the present invention;

FIG. 3 is an enlarged view of the seal shown in FIG. 2;

FIG. 4 is an a greatly enlarged view of an upper portion of the seal, shown separate from a housing and shaft;

FIGS. 5A and 5B, collectively FIG. 5, are each a broken-away, axial cross-sectional view of a portion of the shaft assembly of FIG. 2, FIG. 5A showing the seal in normal pressure conditions and FIG. 5B showing the seal when bended under elevated pressure; and

FIG. 6 is a broken-away, perspective view of the seal in accordance with the present invention.

 DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “inner”, “inwardly” and “outer”, “outwardly” refer to directions toward and away from, respectively, a designated centerline or a geometric center of an element being described, the particular meaning being readily apparent from the context of the description. The words “connected” or “coupled” are each intended to include direct connections between two members without any other members interposed therebetween, indirect connections between members in which one or more other members are interposed therebetween, and operative connections or couplings with a physical separation between two or more members. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.

Referring now to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown in FIGS. 2-6 a seal 10 for sealing an annular space S between a housing 1 and a rotatable shaft 2 disposed at least partially within the housing 1. The housing 1 has an inner circumferential surface 3 defining a bore 4 and an annular recess 5 extending generally radially outwardly from the surface 3. The shaft 2 has a central axis 2a and outer surface 2b, and is preferably a pin of a trunion joint. The seal 10 basically comprises a generally annular, elastomeric seal body 12 disposeable about the shaft 2 and configured to substantially seal the annular space S, and at least one generally rigid support member 14 disposed within the seal body 12. The seal body 12 has a central axis 13 substantially collinear with the shaft axis 2a, a radially outer portion 16 disposeable at least partially within the housing recess 5 to couple the seal 10 with the housing 1, and a radially inner portion 18 with a lip 20 sealingly engageable or contactable with the shaft outer surface 2b. The seal body 12 has a first, “high pressure” axial end 12a exposable to a relatively higher pressure fluid (e.g., bearing lubricant fluid), an opposing, second or “low pressure” axial end exposable to a relatively lower pressure fluid (e.g., air), and an outer circumferential surface 12b extending generally between the two axial ends 12a, 12b and disposable generally against an inner circumferential surface 5a of the housing recess 5.

Further, the seal body inner portion 18 has a radially outer end 18a connected with the body outer portion 16 and a radially inner end 18b providing the sealing lip 20. The seal body inner portion 18 is angled with respect to the central axis 13 such that the inner end 18b is spaced axially with respect to the outer end 18 in a direction generally toward the seal body low pressure end 12b and the lip 20 is offset axially from a center C of the body 12 toward the low pressure end 12b. With this structure, the seal body 12 is configured to bendingly deflect when fluid pressure PF on the body 12 exceeds a predetermined value (e.g., 50 psi) such that the body inner portion 18 displaces generally radially outwardly with respect to the axis 13 to permit fluid flow between the shaft 2 and the body 12, as depicted in FIG. 5B.

Further, the at least one reinforcing support member 14 is disposed within the body outer portion 16 so as to be located at least partially within the housing recess 5 when the seal 10 is coupled with the housing 1. The support member 14 increases the rigidity of the body 12 and is thus configured to limit or at least reduce bending deflection the body outer portion 16 to prevent disengagement of the body 12 from the recess 5. Therefore, by having a support member 14 that reduces or eliminates deflection of the body outer portion 16 when the body 12 is exposed to higher fluid pressures, the seal 10 remains coupled with the recess 5 instead of disengaging therefrom, which often occurred with previously known seals as discussed in the Background section above.

Preferably, the support member 14 includes a single, generally annular body 22 extending circumferentially and entirely about the axis 13 (i.e., is formed as an integral ring). More specifically, the support member body 22 is preferably formed having a generally axial portion 24 and a generally radial portion 26 extending radially-inwardly from the axial portion 24, such that the body 22 has generally “L-shaped” axial cross-sections. Further, the preferred support member 14 is preferably located within the seal body 12 so as to increase rigidity or stiffness at the first, high pressure end 12a of the body 12 while permitting a greater degree of deflection or compression at the second, low pressure end 12b to facilitate assembly into the recess 5, as discussed below. Furthermore, the support member 14 is preferably molded within the seal body 12, but may be separately attached to, or inserted within, the body 12. Also, the seal body 12 is preferably formed of urethane and the support member 14 is formed of a rigid polymer, such as for example, nylon.

Although preferably formed as described above, the support member 14 may be formed in any other appropriate manner. For example, the support member 14 may include a plurality of separate, generally arcuate segments spaced circumferentially about the axis 13 and/or may have cross-sections of any other appropriate shape (e.g., circular, rectangular, C-shaped, etc). Further, the seal body 12 and/or the support member 14 may be formed of any other appropriate material, such as for example, fabricating the seal body 12 of synthetic rubber and the support member 14 of Delrin.

Referring to FIGS. 3 and 4, the support member 14 is preferably located within the seal body 12 such that the support member radial portion 26 is disposed at least generally adjacent to the seal body high pressure end 12a and the support member axial portion 24 extends generally axially from the radial portion 26 in a direction generally toward the seal body low pressure end 12b, and is preferably generally adjacent to the seal body outer surface 12c. As such, when the seal body 12 is located within the housing recess 5, the two portions or legs 24, 26 of the support member 14 tend to act against adjacent surfaces 5a, 5b, respectively of the recess 5 to resist bending of the seal body 12. Thus, the support member 14 provides a substantially increased bending resistance at a first end 16a of the body outer portion 16, which prevents disengagement of the body 12 from the recess 5, as discussed in greater detail below. Further, the support member radial portion 26 is spaced from a second, opposing end 16b of the seal body outer portion 16, such that the body outer portion 16 is compressible to a certain extent at the second end 16b, which facilitates assembly into the housing recess 5.

Furthermore, the seal body 12 has a central bore 21 defined by the sealing lip 20 which is configured to receive a portion of the shaft 2. Preferably, the central bore 21 is sized having a inner diameter DI (FIG. 4) that is lesser than an outer diameter DO (FIG. 3) of the shaft 2 when the seal 10 is separate from the shaft 2, as depicted in FIG. 4. As such, the sealing lip 20 engages the shaft outer surface 2b with an interference fit, so that sealing contact is generally maintained between the lip 20 and the shaft 2 without the need of a biasing component, such as a garter spring. Furthermore, the seal body 12 also preferably includes at least one secondary sealing lip 30 extending at least partially axially from the body outer portion 16 at the body second, low pressure end 12b. The secondary lip 30 is engageable with the housing recess 5 to prevent fluid flow between the body outer portion 16 and the recess 5.

As discussed above, the body inner portion 18 is preferably generally angled with respect to the central axis 13 such that the sealing lip 20 is offset axially from a center C (FIG. 3) of the body 12 and has a first surface 19A at the body first end 12a which faces generally toward the axis 13 and a second end surface 19B at the body second end 12b which faces generally away from the axis 13. With this structure, the body inner portion 18 bends or deflects to displace generally radially outwardly with respect to the axis 13 when fluid pressure PF on the first end surface 19A exceeds the predetermined value, to thereby disengage the lip 20 from the shaft outer surface 2b. Further, the seal body 12 also preferably includes a substantially radially-extending central portion 17 extending between and integrally connecting the outer and inner portions 16, 18, respectively. The body outer and central portions 16, 17 have a relatively greater axial thickness than the body inner portion 18, such that elevated pressure tends to primarily bend/deflect the body inner portion 18 about an inner end 17a of the central portion 17. However, the seal body 12 may alternatively be formed with the outer and inner portions 16, 18 directly connected or formed together, such that the inner portion 18 bends about an inner end 16a of the outer portion 16.

Referring specifically to FIG. 2, the seal 10 is preferably used with a shaft assembly that further includes a bearing 6 configured to rotatably support the shaft 2. The housing 1 is located generally adjacent to the bearing 6 and may be disposed within an outer casing 7 enclosing both the housing 1 and the bearing 6 (as depicted), but the housing 1 may alternatively be provided by the casing 7 or even a portion of the bearing outer race 6a. The seal 10 is arranged such that at least a portion of the body first end 12a is exposable to fluid (e.g., grease or oil) within the bearing 6. As such, radial displacement of the body inner portion 18 to lift the lip 20 from the shaft 2 releases a portion of the fluid F from the bearing 6.

Thus, the seal 10 is capable of “burping” and releasing some bearing fluid F (i.e., lubricant) when the fluid pressure PF increases beyond an undesirable or unacceptable level, as may occur when the bearing 6 is provided with an excessive amount of lubricant. Typically, only one of more circumferential sections of the lip 20 will be lifted from the shaft 2 during such a burping process, but the body inner portion 18 may disengage the entire lip 20 off of the shaft 2 in certain situations. In any case, due to the reinforcement of the first end 16a of the body outer portion 16, the bending stresses generated within the outer portion 16 by fluid pressure PF acting on the first side 12a of the body 12 are not sufficient to deflect the outer portion 16 to any significant extent. As such, the body outer portion 16 remains disposed within the housing recess 5 so that the seal 10 continues to seal the annular space S as intended.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as generally defined in the appended claims.

Claims

1. A seal for sealing a space between a housing and a rotatable shaft disposed at least partially within the housing, the housing having an annular recess and the shaft having an outer surface, the seal comprising:

a generally annular, elastomeric seal body disposeable about the shaft, the body having a central axis, a radially outer portion disposeable at least partially within the housing recess so as to couple the seal with the housing, and a radially inner portion with a lip sealingly engageable with the shaft outer surface, at least a portion of the seal body being configured to bendingly deflect when fluid pressure exerted on the body exceeds a predetermined value such that at least a section of the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the seal body; and
at least one generally rigid support member disposed within the body outer portion so as to be located at least partially within the housing recess when the seal is coupled with the housing, the support member being configured to at least reduce bending deflection of the body inner portion so as to prevent disengagement of the body from the recess.

2. The seal as recited in claim 1 wherein the support member includes a generally annular body having an axial portion and a radial portion extending generally radially-inwardly with respect to the axial portion.

3. The seal as recited in claim 1 wherein the seal body inner portion is generally angled with respect to the central axis such that the lip is offset axially from a center of the body, the body inner portion having a first end surface facing generally toward the axis at the body first end and a second end surface facing generally away from the axis at the body second end.

4. The seal as recited in claim 3 wherein the body inner portion displaces generally radially outwardly with respect to the axis when fluid pressure on the first end surface exceeds the predetermined value such that the lip disengages from the shaft outer surface.

5. The seal as recited in claim 1 wherein the seal body further includes a substantially radially-extending central portion extending between and integrally connecting the inner and outer portions.

6. The seal as recited in claim 1 wherein:

the seal body has a high pressure axial end exposable to a relatively higher pressure fluid and an opposing, low pressure axial end exposable to a relatively lower pressure fluid, the body inner portion has a radially outer end connected with the body outer portion and a radially inner end providing the sealing lip, the seal body inner portion being angled with respect to the central axis such that the inner end is spaced axially with respect to the outer end in a direction generally toward the seal body low pressure end; and
the support member includes a generally annular body with a generally axial portion and a generally radial portion extending radially-inwardly with respect to the axial portion, the support member being arranged within the seal body outer portion such that support member radial portion is disposed at least generally adjacent to the seal body high pressure end and the support member axial portion extends generally axially from the radial portion in a direction generally toward the seal body low pressure end.

7. The seal as recited in claim 6 wherein the seal body further includes at least one secondary sealing lip extending at least partially axially from the seal body low pressure end and being engageable with the housing recess to prevent fluid flow between the seal body outer portion and the recess.

8. The seal as recited in claim 1 wherein the support member is molded within the seal body.

9. The seal as recited in claim 8 wherein the seal body is formed of urethane and the support member is formed of a rigid polymer.

10. A shaft assembly comprising:

a housing having an inner circumferential surface defining a central bore and a recess extending generally radially outwardly from the inner surface;
a rotatable shaft disposed within the housing bore such that a generally annular space is defined between the shaft and the housing inner surface;
a bearing disposed within the housing and configured to rotatably support the shaft, the bearing containing a lubricant fluid; and
a seal configured to seal the annular space and including a a generally annular, elastomeric seal body with a central axis and at least one generally rigid support member disposed within the body, the body being disposeable about the shaft and having a radially outer portion disposeable at least partially within the housing recess and a radially inner portion with a lip sealingly engageable with the shaft outer surface, the body being configured to bendingly deflect when fluid pressure on the body exceeds a predetermined value such that the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the body, the at least one support member being disposed within the body outer portion so as to be located at least partially within the housing recess and configured to at least reduce bending deflection of the body inner portion so as to prevent disengagement of the body from the recess.

11. The seal as recited in claim 10 wherein the support member includes a generally annular body having an axial portion and a radial portion extending generally radially-inwardly with respect to the axial portion.

12. The seal as recited in claim 10 wherein the seal body inner portion is generally angled with respect to the central axis such that the lip is offset axially from a center of the body, the body inner portion having a first end surface facing generally toward the axis at the body first end and a second end surface facing generally away from the axis at the body second end.

13. The seal as recited in claim 12 wherein the body inner portion displaces generally radially outwardly with respect to the axis when fluid pressure on the first end surface exceeds the predetermined value such that the lip disengages from the shaft outer surface.

14. The seal as recited in claim 10 wherein the seal body further includes a substantially radially-extending central portion extending between and integrally connecting the inner and outer portions.

15. The shaft assembly as recited in claim 10 wherein the seal body has opposing first and second axial ends, at least a portion of the body first end being exposable to the fluid within the bearing such that radial displacement of the body inner portion releases a portion of the fluid from the bearing.

16. The seal as recited in claim 10 wherein:

the seal body has a high pressure axial end exposable to a relatively higher pressure fluid and an opposing, low pressure axial end exposable to a relatively lower pressure fluid, the body inner portion has a radially outer end connected with the body outer portion and a radially inner end providing the sealing lip, the seal body inner portion being angled with respect to the central axis such that the inner end is spaced axially with respect to the outer end in a direction generally toward the seal body low pressure end; and
the support member includes a generally annular body with a generally axial portion and a generally radial portion extending radially-inwardly with respect to the axial portion, the support member being arranged within the seal body outer portion such that support member radial portion is disposed at least generally adjacent to the seal body high pressure end and the support member axial portion extends generally axially from the radial portion in a direction generally toward the seal body low pressure end.

17. The shaft assembly as recited in claim 13 wherein the seal body is formed of urethane, the support member is formed of a rigid polymer, and the support member is molded within the seal body.

18. A seal for sealing a space between a housing and a rotatable shaft disposed at least partially within the housing, the housing having an annular recess and the shaft having an outer surface, the seal comprising:

a generally annular, elastomeric seal body disposeable about the shaft, the seal body having a central axis, a radially outer portion disposeable at least partially within the housing recess so as to couple the seal with the housing, and a radially inner portion with a lip sealingly engageable with the shaft outer surface, the seal body being configured to bendingly deflect when pressure on the body exceeds a predetermined value such that at least a section of the body inner portion displaces generally radially outwardly with respect to the axis to permit fluid flow between the shaft and the seal body, the body having a high pressure axial end exposable to a relatively higher fluid pressure and an opposing, low pressure axial end exposable to a relatively lower fluid pressure; and
at least one generally rigid support member disposed within the seal body outer portion so as to be located at least partially within the housing recess when the seal is coupled with the housing, the support member including a generally annular body with an axial portion and a radial portion extending radially-inwardly with respect to the axial portion, the support member being arranged within the seal body outer portion such that support member radial portion is disposed at least generally adjacent to the seal body high pressure end and the support member axial portion extends generally axially from the radial portion in a direction generally toward the seal body low pressure end.

19. The seal as recited in claim 18 wherein the support member is configured to at least reduce bending deflection of the body inner portion so as to prevent disengagement of the body from the recess.

20. The seal as recited in claim 1 wherein the seal body inner portion is generally angled with respect to the central axis such that the lip is offset axially from a center of the body, the body inner portion having a first end surface facing generally toward the axis at the body high pressure end and a second end surface facing generally away from the axis at the body low pressure end, the body inner portion displacing generally radially outwardly with respect to the axis when fluid pressure on the first end surface exceeds the predetermined value such that the lip disengages from the shaft outer surface.

Patent History
Publication number: 20140064936
Type: Application
Filed: Jan 27, 2012
Publication Date: Mar 6, 2014
Applicant: AKTIEBOLAGET SKF (Goteborg)
Inventor: Scott Michael Barth (West Riverton, UT)
Application Number: 13/982,293
Classifications
Current U.S. Class: Bearing, Seal, Or Liner Between Runner Portion And Static Part (415/170.1)
International Classification: F01D 25/24 (20060101);