GB2276681A

GB2276681A - Sealing arrangements

Info

Publication number: GB2276681A
Application number: GB9306923A
Authority: GB
Inventors: Nigel Henry New
Original assignee: Glacier Metal Co Ltd
Current assignee: Federal Mogul Engineering Ltd
Priority date: 1993-04-02
Filing date: 1993-04-02
Publication date: 1994-10-05
Anticipated expiration: 2013-04-02
Also published as: GB9306923D0; GB2276681B

Abstract

A stationary floating seal arrangement for sealing between a floating shaft 11 and housing 14 comprises an annular sealing member 32 carried in sealing relationship on the shaft and extending radially into annular recess 17', being biased axially to form a face seal with the recess wall 24' by an annular bias member 36 to which it is coupled by spring units 41. The bias member 36 may form a further identical sealing member Fig 4 (not shown) arrangement provides face sealing independently of axial force on an annular sealing member derived from elevated pressure within the housing in a convenient self-contained form. The bias member may also form a labyrinth seal. <IMAGE>

Description

Improvements relating to sealing arranaements This invention relates to seal arrangements for fluid-containing housings through which rotating shafts extend and in particular relates to seal arrangements of the stationary floating type which are supported by such a shaft and located with respect to a housing in accordance with shaft position whilst not rotating with the shaft.

An example of a known stationary floating seal arrangement is shown in sectional elevation at 10 in Figure 1 in relation to a rotating shaft 11 extending along an axis 12. The shaft extends by way of opening 13 from a housing 14 of a machine 15, such as a bearing unit, which contains a fluid, such as lubricating oil 16. In machines such as the aforementioned bearing unit, the shaft may move in position relative to the housing as a result of coupling with external components or by external transverse loading, that is, float transversely to the longitudinal axis 12.

Accordingly the aperture 13 is significantly larger than the shaft to permit variation in shaft disposition-relative to the housing.

Operation of the bearing unit typically results in above ambient pressure in the housing and egress of the fluid by way of the opening 13 between the shaft and housing. The housing 14 is not necessarily filled with fluid but even then droplets of fluid entrained by the housing atmosphere at above ambient pressure to egress by way of the opening 13.

The housing 14 includes, about the aperture 13, an annular recess 17 facing the shaft.

The stationary floating seal arrangement 10 comprises an annular sealing member 18 having a radially inner surface 19, adapted to supported the member on the shaft by way of a fluid sealing interface that is a sliding fit on the shaft, and having a radially extending part 20 adapted to extend into the recess 17.

One face 21 of the radially extending part is adapted to conform with outboard wall 22 of the recess to provide a face seal between the sealing member and the housing when urged into abutment by an axially directed sealing force.

The sealing member is typically formed as a unitary ring fed axially along the shaft or from two semi-circular segments assembled about the shaft and held with a radially inward bias by a garter spring 23 extending about the periphery of the member. The sealing member is inhibited from rotation with the shaft by locating-means-(not shown) between the member and'the housing and furthermore is a loose fit within the recess, whereby the actual radial disposition of the sealing member with respect to the recess wall is able to vary as a -function of shaftdisposition with respect to the housing and the housing atmosphere has access to the inboard radially extending face of the member.

In operation, the elevated pressure within the housing acting on the member is employed to bias it axially against the wall 22 of the recess to form said face seal and prevent the egress of fluid between the sealing member and the housing, notwithstanding that the actual position of the shaft with respect to the housing is not fixed and variable with shaft float.

The radially inner surface 19 of the sealing member may be a simple sealing face of close tolerance to the shaft and of relatively short axial extent, as shown, and be contained in a correspondingly short recess defined by inboard radially extending wall 24. Alternatively, it may extend further along the shaft to form a labyrinth seal; in such a construction the radially extending part 20 is normally also of corresponding axial extent to support the labyrinth seal and the recess in the housing extends correspondingly further in an axial direction as illustrated by ghosted inboard wall 24'.

It will be appreciated that a sealing arrangement as described may be analogously employed within a machine between two parts thereof separated within a common housing.

In machine arrangements as described the efficacy of the face seal is dependant upon the existence of axial force on the member and this in turn is dependant upon the existence of a pressure difference across the seal, whether by above-ambient pressure within the housing in relation to a seal about an external shaft or pressure differences between housing parts separated by an internal seal. It is known, however, in some applications that such pressure difference is very low, or possibly transiently negative, as a result of which the sealing member may not only fail to make proper sealing abutment with the recess wall but may also move about axially within the recess departing from a plane perpendicular to the axis 12 and allow fluid to pass freely around the seal.

In a situation as described above wherein the housing comprises an atmosphere containing fluid, even if in the form of dispersed droplets, such fluid may egress between the sealing member and the housing.

Hitherto it has been known in practice to mitigate such leakage by inserting a flexible sealant material into the recess between the radially outer edge (garter spring) and the bight of the recess. However, it will be appreciated that such action in eliminating radial clearance between sealing member and housing, also destroys-the ability of the seal to float radially with shaft disposition.

Having regard to the floating nature of the seal arrangement it is an object of the present invention to provide a stationary floating seal arrangement for such application which in simple manner ensues both shaft and face sealing without dependence on housing pressure.

According to a first aspect of the present invention a stationary floating seal arrangement for preventing egress of fluid from a housing by way of an opening therein surrounded by an annular recess and through which a shaft extends comprises (i) an annular sealing member adapted to support the member on the shaft to provide a shaft seal-permitting axial and rotational motion of the shaft with respect to the member, and having a radially extending part adapted to extend into said recess and provide with a wall of said recess, in response to axially directed sealing force urging the member into abutment with the wall, a face seal between the sealing member and the housing, and (ii) an annular bias member, apertured to contain the shaft, disposed coaxially with the sealing member and containing spring bias means extending to the sealing member and operable to bias the members apart axially, said bias and sealing members being adapted to be contained within said recess and mutually biased apart axially by the spring bias means into abutment with opposite walls of the recess to exert axial sealing force between the sealing member seal face and the housing.

The annular-bias member may comprise a further sealing member-having a radially inner surface adapted to be supported by the shaft by way of- a fluid sealing interface permitting axial and rotational motion of the shaft with respect to the member and a radially extending part adapted to provide in response to axially directed sealing force urging the member into abutment with the recess wall a face seal with said wall of the recess.

According to a second aspect of the present invention a machine includes a rotatable shaft supported in a housing, an annular recess in the housing surrounding the shaft, having facing recess walls separated in an axial direction, and a stationary floating seal arrangement, as defined by the two preceding paragraphs, carried by the shaft in sealing relationship therewith and having said annular sealing member and bias member extending into said housing recess and biassed apart axially into abutment with respective recess walls such that at least the sealing member provides a fluid seal between a radially extending face thereof and the recess wall.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1, described above, is a sectional elevation through a portion of a rotatable shaft and machine housing from which the shaft extends and a conventional stationary floating sealing arrangement comprising a sealing member borne by the shaft for preventing egress of fluid from the housing, defining a shaft seal between the sealing member and shaft and a face seal between the sealing member and housing energised by pressure within the housing acting axially on the sealing member, Figure 2 is a sectional elevation through part of a shaft and housing similar to that of Figure 1 but including a stationary floating seal arrangement in accordance with a first embodiment of the present invention, comprising in addition to an annular sealing member, an annular bias member containing axial spring bias means, Figure 3 is an enlarged view of the encircled portion III of Figure 2 showing in greater detail a form of spring bias means, and Figure 4 is a sectional elevation through a part of a shaft and housing arrangement similar to Figure 2 but including a stationary floating seal arrangement in accordance with a second embodiment of the present invention in which the annular bias member comprises a further annular sealing member.

Referring to Figures 2 and 3, the machine 30 is similar to the machine 15 described above with reference to Figure 1 and insofar as many parts are common, identical reference numbers are used where appropriate. The machine comprises a bearing arrangement including bearing surfaces (not shown) and lubricating oil 16 which is thrown over the bearing components by rotation of the shaft whereby an above ambient pressure develops within the housing which entrains oil- -droplets to egress -by way of the aperture 13. Because of the nature of the shaft and bearing arrangement the shaft can float in relation to the housing within the aperture 13.

The housing 14 contains surrounding the aperture 13 and opening thereto, a recess 17' which is similar to recess 17 of Figure 1 but of greater axial extent, that is, bounded axially by the above described radially extending walls 22 and 24' usually associated with a labyrinth sealing member.

A floating seal arrangement 31 comprises an annular sealing member 32 having a radially inner surface 33, adapted to support the member on-the shaft 11 to provide a fluid sealing interface permitting axial and rotational motion of the shaft with respect to the member, and a radially extending part 34 adapted to extend into the recess 17' with a face 35 of the member adjacent inboard recess wall 24'.

The seal arrangement further comprises an annular bias member 36, apertured at 37 to contain the shaft, disposed coaxially with the sealing member and containing spring bias means shown generally at 38 extending axially to the sealing member. The bias member extends radially so as to be disposed in the recess 17' adjacent the radially extending outboard wall 22 and the spring bias means operates to mutually bias the members 32 and 36 apart axially and into abutment with the opposite walls 22 and 24' of the recess, particularly to exert an axial sealing force on -the sealing member and between the seal face 35 and the housing.

The sealing member 32 is composed of two or more segments so as to be assembled about the shaft and held together by radially compressive garter spring 39 in a unitary annular member. The bias member 36 may likewise be formed of segments and held in a unitary annular form by garter spring 40.

Conveniently, the spring bias means 38 comprises a plurality of individual spring units 41 arrayed about the axis 12. Where said members are formed by assemblies of segments, it is appropriate for the corresponding, axially aligned, segments of sealing and bias member to be of equal arcuate length; and furthermore, if individual spring units are employed, for each segment of the sealing member to be coupled to a corresponding segment of the bias member by at least one spring unit.

Conveniently the spring units 41 and these attachments with the members are identical. A portion of Figure 2 within a circle III is shown enlarged in Figure 3.

Each spring unit 41 comprises a helical compressing spring 42 and a tie bar 43, of axial length less than the axial length of the recess, extending along the axis of the spring substantially parallel to shaft axis 12 and into-the member parts 34 and 36.

The tie bar is movable in an axial direction with respect to one, and preferablyboth, of-the members to-permit the-members-to be biased apart further than the axial length of said housing recess when not constrained thereby, that is, so that the axial length of the recess, not the length of the tie bar, limits the axial separation of the members in operation.

To retain the members in relation to each other when not contained in the recess, each member 34 or 36 in relation to which the tie bar is movable contains a through-aperture 44 extending axially thereof having a first part 45, proximate the other member, forming a clearance fit for the tie bar and a second part 46, of increased cross section, forming a cavity 47 facing away from the other member and opening into the member face which in operation abuts, and may form a seal face with, a wall of the housing recess.

The tie bar extends through said through-aperture and is terminated by a boss or enlargement 48 wholly containable within the cavity 47 so as not to interfere with engagement between the member face and recess wall.

Conveniently, the tie bar is of uniform cross section along its length and each boss is provided by a frictionally engaging washer located onto the tie bar adjacent its end as shown at 49.

It will be appreciated that axial motion of the tie~may be in relation to one member only, the end of the tie bar being fixed in relation to the other member by a simple screw thread or interference fit in an aperture.

As illustrated, the aperture 37 in the bias member provides a clearance fit for the shaft such that the bias member 36 is supported by its connection with the sealing member by way of the spring bias means 38 which is therefore constrained to provide such support in operation when the sealing member, supported on the shaft is caused to float radially with respect to the housing.

Alternatively, the aperture 37 in the bias member may be dimensioned to bear on the shaft by lands or pads or the -like such that the bias member is borne by the shaft and constrained to move radially with the sealing member in accordance with shaft disposition.

Operation, with the seal arrangement installed, is conventional in respect of the sealing member providing both a journal seal in relation to the shaft and a face seal in relation to wall 24' of the housing recess. However, it will be seen that the sealing member is biased axially to effect a face seal by spring bias means with an inboard recess wall and in opposition to any axial force due to pressure within the housing.

Such disposition ensures that the bias member and spring units are not contaminated by exposure to the housing contents and that the sealing surfaces inboard of the opening.l3 to minimise damage and contamination from external sources.

However, the sealing force is opposed by above-ambient pressure in the housing and such seal arrangement disposition is therefore beneficial only insofar as the spring bias pressure is assuredly stronger than axial forces that can be generated by housing pressure.

It will be appreciated that if desired or necessary the seal arrangement 31 may be reversed such that the sealing member 32 abuts the outboard recess wall 22 and face sealing is enhanced by housing pressures.

It will be appreciated that in such event the bias member, even if borne on the shaft for radial position location, will allow fluid to pass to cause correct operation of the outboard sealing member.

Referring to Figure 4, this shows in similar sectional elevation a portion of machine 30' containing like numbered parts but a different form of seal arrangement 50 according to a second embodiment of the invention. Many components of the seal arrangement 50 are similar to those of arrangement 31, and identically referenced in respect of sealing member 32 and spring bias means 38 formed of separate spring units 41. The annular bias member 36' comprises a further sealing member identical with the member 32 in having a radially-inner-surface 33' supported sealingly on shaft 15 and a radially extending face seal 35' for sealing abutment with wall 22 of the recess.

It may be found desirable to ensure that the inboard sealing member 32 permits some leakage of lubricant to assist in sealing efficiency and longevity of the outboard sealing member in a manner corresponding to when a single sealing member is disposed outboard of a non-sealing bias member. Such leakage may be by way of through-apertures arrayed about the shaft but displaced therefrom, as indicated by dotted lines 51, or similar apertures formed as grooves at the radially inner surface 33.

It will be appreciated that the seal arrangement, and machine incorporating such seal arrangement, requires no modification of the housing of an existing machine other than providing a recess of axial extent typical for the use of a floating labyrinth seal in which to locate the axially shorter sealing member and bias member/further sealing member.

Furthermore, the seal arrangement is self-contained and axial bias provided without interfering with the radial floating function or requiring connection between the seal arrangement and housing beyond conventional anti-rotation provisions.

It will be appreciated that many minor changes may be effected in respect of the spring bias means and sealing co-operation between the sealing member(s) and housing and shaft. The shaft seal, although shown as being of the same axial extent as the thickness of the sealing member may be of greater axial length, particularly in the direction between the members, with the parts 33 and/or 33' formed as labyrinth seals.

It will be appreciated that the sealing member and bias member may be formed as a unitary ring where there is access to feed the arrangement along the shaft before disposing it with respect to the housing such that the members are contained within a recess defined thereby.

It will be appreciated that references above to the shaft extending internally to externally of a housing are appropriate in where the shaft is contained within a machine and extends between enclosures thereof, separated by a housing wall containing a seal arrangement as described. One enclosure part of the machine may be considered as providing the "housing" containing fluid whose egress is undesirable whilst the other enclosure part may be considered as exterior of the "housing".

Claims

CLAINS

1. A stationary floating seal arrangement for preventing egress of fluid from a housing by way of an opening therein surrounded by an annular recess and through which a shaft extends, comprising (i) an annular sealing member having a radially inner surface adapted to support the member on the shaft to provide a shaft seal permitting axial and rotational motion of the shaft with respect to the member, and having a radially extending part adapted to extend into said recess and provide with a wall of said recess, in response to axially directed sealing force urging the member into abutment with the wall, a face seal between the sealing member and the housing, and (ii) an annular bias member, apertured to contain the shaft, disposed coaxially with the sealing member and containing spring bias means extending to the sealing member and operable to bias the members apart axially, said bias and sealing members being adapted to be contained within said recess and mutually biased apart axially into abutment with opposite walls of the recess to exert axial sealing force between the sealing member seal face and the housing.

2. A seal arrangement as claimed in claim 1 in which said seal member is arranged to be operationally disposed inboard of the annular bias member.

3. A seal arrangement as claimed in claim 1 or claim 2 in which the annular bias member is apertured to have a radially inner surface adapted to support the member on the shaft in predetermined radial relationship with the sealing member.

4. A seal arrangement as claimed in any one of the preceding claims in which the annular bias member comprises a further sealing member having a radially inner surface adapted to support the member on the shaft to provide a shaft seal permitting axial and rotational motion of the shaft with respect to the member and having a radially extending part adapted to provide in response to axially directed sealing force urging the member into abutment with the recess wall a face seal with said wall of the recess.

5. A seal arrangement as claimed in any one of the preceding claims in which the spring bias means comprises a plurality of individual spring units arrayed about the annular axis.

6. A seal arrangement as claimed in claim 5 in which each spring unit comprises a helical compression spring, a tie bar, of axial length less than the axial length of said housing recess, extending along the axis of the spring and into the members such as--to be movable in an axial direction with respect to at least one of the members to permit the faces of said members to be biased apart further than the axial length of said housing recess.

7. A seal arrangement as claimed in claim 6 in which each member, in relation to which the tie bar is movable, contains a through-aperture, extending in an axial direction having a first part proximate the other member forming a clearance fit for the tie bar and a second part of increased cross section forming a cavity facing away from the other member, the tie bar extends through said aperture and is terminated by a boss wholly containable within said cavity.

8. A seal arrangement as claimed in claim 7 in which the tie bar is of uniform cross section along its length and each said boss is provided by a frictionally engaging washer carried adjacent the end of the tie bar.

9. A seal arrangement as claimed in any one of the preceding claims in which the sealing member comprises a plurality of separate segments extending about the axis and bound together into a unitary annular member, and the bias member comprises a plurality of separate segments corresponding in length to the segments of the sealing member axially aligned therewith and bound together into a unitary annular member.

10. A sealing-arrangement as claimed in claim 9 when dependent on claim 5 in which each segment of the sealing member is coupled to a corresponding segment of the bias member by at least one spring unit.

11. A seal arrangement substantially as herein described with reference to, as shown in, Figures 2 and 3 or in Figure 4 of the accompanying drawings.

12. A machine substantially as herein described with reference to, and as shown in, Figures 2 and 3 or Figure 4 of the accompanying drawings.

12. A machine including a rotatable shaft supported in a housing, an annular recess in the housing surrounding the shaft having facing recess walls separated in an axial direction and a stationary floating seal arrangement as claimed in any one of the preceding claims carried by the shaft in sealing relationship therewith and having said annular sealing member and bias member extending into said housing recess and biassed apart axially into abutment with respective recess walls such that at least the sealing member provides a fluid seal between a radially extending face thereof and a recess wall.

13. A machine substantially as herein described with reference to, and as shown in, Figures 2 and 3 or Figure 4 of the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A stationary floating seal arrangement for preventing egress of fluid from a housing by way of an opening therein surrounded by an annular recess and through which a shaft extends, comprising (i) an annular sealing member having a radially inner surface adapted to support the member on the shaft and movable radially therewith to provide a shaft seal permitting axial and rotational motion of the shaft with respect to the member, and having a radially extending part adapted to extend into said recess and provide with a wall of said recess, in response to axially directed sealing force urging the member into abutment with the wall, a radially floating face seal between the sealing member and the housing, and (ii) an annular bias member, apertured to contain the shaft, disposed substantially coaxially with the sealing member and in the recess containing spring bias means, operable to bias the members apart axially into abutment with opposite walls of the recess to exert axial sealing force between the sealing member seal face and the housing, comprising a plurality of individual spring units arrayed about the annular axes of the members and extending axially between the members including a spring bearing on the members to bias them apart and means to limit the separation of the biased members.

2. A seal arrangement as claimed in claim 1 in which each spring unit comprises a helical compression spring, a tie bar, of axial length less than the axial length of said housing recess, extending along the axis of the spring and into the members such as to be movable in an axial direction with respect to at least one of the members to permit the faces of said members to be biased apart further than the axial length of said housing recess.

3. A seal arrangement as claimed in claim 2 in which each member, in relation to which the tie bar is movable, contains a through-aperture, extending in an axial direction having a first part proximate the other member forming a clearance fit for the tie bar and a second part of increased cross section forming a cavity facing away from the other member, the tie bar extends through said aperture and is terminated by a boss wholly containable within said cavity.

4. A seal arrangement as claimed in claim 3 in which the tie bar is of uniform cross section along its length and each said boss is provided by a frictionally engaging washer carried adjacent the end of the tie bar.

5. A seal arrangement as claimed in any one of the preceding claims in which the sealing member comprises a plurality of separate segments extending about the axis and bound together into a unitary annular member, and the bias member comprises a plurality of separate segments corresponding in length to the segments of the sealing member axially aligned therewith and bound together into a unitary annular member.

6. A sealing arrangement as claimed in claim 5 in which each segment of the sealing member is coupled to a corresponding segment of the bias member by at least one spring unit.

7. A seal arrangement as claimed in any one of the preceding claims in which said seal member is arranged to be operationally disposed inboard of the annular bias member.

8. A seal arrangement as claimed in any one of the preceding claims in which the annular bias member is apertured to have a radially inner surface adapted to support the member on the shaft in predetermined radial relationship with the sealing member.

9. A seal arrangement as claimed in any one of the preceding claims in which the annular bias member comprises a further sealing member having a radially inner surface adapted to support the member on the shaft to provide a shaft seal permitting axial and rotational motion of the shaft with respect to the member and having a radially extending part adapted to provide in response to axially directed sealing force urging the member into abutment with the recess wall a face seal with said wall of the recess.

10. A seal arrangement substantially as herein described with reference to, as shown in, Figures 2 and 3 or in Figure 4 of the accompanying drawings.

11. A machine including a rotatable shaft supported in a housing, an annular recess in the housing surrounding the shaft having facing recess walls separated in an axial direction and a stationary floating seal arrangement as claimed in any one of the preceding claims carried by the shaft in sealing relationship therewith and having said annular sealing member and bias member extending into said housing recess and biassed apart axially into abutment with respective recess walls such that at least the sealing member provides a fluid seal between a radially extending face thereof and a recess wall.