GB2582351A

GB2582351A - Seal

Info

Publication number: GB2582351A
Application number: GB1903848.8A
Authority: GB
Inventors: Viljoen Abraham
Original assignee: Weir Minerals Africa Pty Ltd
Current assignee: Weir Minerals Africa Pty Ltd
Priority date: 2019-03-20
Filing date: 2019-03-20
Publication date: 2020-09-23
Also published as: GB201903848D0

Abstract

A seal 28 comprising a primary seal 60 and at least one outwardly-directed protrusion 166. The protrusion (166, Fig. 7), which may be an annular rib, has axially inner (168, Fig. 7) and outer (170, Fig. 7) surfaces, the inner surface (166, Fig. 7) extending inwardly at an angle of at least 0° relative to a lateral plane. The primary seal 60 may be a labyrinth seal. Also disclosed is a gearbox 12 containing two parallel shafts 14, 16 drivingly-interconnected by gears 22 mounted on the portions of the shafts within the gearbox 12; and a seal 28. Further disclosed is a method of modifying a piece of equipment with a labyrinth seal including a labyrinth ring. The method involves removing the labyrinth ring and replacing it with a labyrinth ring 32 of the seal of the first aspect.

Description

SEAL

This invention relates to seals. More particularly, it relates to a seal arrangement, to a labyrinth ring for use in the seal arrangement, to a gearbox incorporating such a seal, and to a method of modifying an article of equipment.

The Inventor is aware of an exciter which comprises a gearbox and two parallel shafts which are mounted to the gearbox for rotation about parallel axes. The shafts are drivingly interconnected by gears mounted on each of the portions of the shafts positioned within the gearbox such that the shafts rotate in opposite directions.

End portions of the shafts protrude from the gearbox and eccentric weights are mounted on the protruding end portions of the shafts such that rotation of the shafts sets up a vibration which can be transmitted to a screen or the like.

The shafts are supported in bearings mounted in the gearbox. Oil is contained in the gearbox to lubricate the gears and the bearings. To prevent the oil escaping from the gearbox a seal arrangement is provided at each of the points where the shafts penetrate the gearbox.

In one exciter of which the Inventor is aware, each seal arrangement is of composite construction and comprises an annular bearing cover which is mounted to the gearbox housing and a labyrinth ring which is mounted to the shaft for rotation therewith. The bearing cover and labyrinth ring have complementary concentric annular ribs and recesses which overlap in an axial direction to form a labyrinth seal. An annular oil flinger is mounted on the shaft axially inwardly of the labyrinth ring, i.e. between the labyrinth ring and the adjacent bearing. An elastomeric seal, typically a V-ring seal is provided between the bearing cover and the labyrinth ring.

Adjacent to an inner end of the labyrinth seal, the bearing cover and the labyrinth ring define between them an annular gap having a radially inner surface formed by the labyrinth ring and a radially outer surface formed by the bearing cover. The oil flinger is positioned adjacent to an axially inner end of the annular gap.

By virtue of the construction of the labyrinth seal and the centripetal forces generated by the rotation of the labyrinth ring, oil which enters the labyrinth seal generally is displaced outwardly along the convoluted path defined between the bearing cover and the labyrinth ring and can be discharged from an outer end of the labyrinth seal.

The V-ring seal typically includes a cantilever arrangement configured to inhibit the ingress of foreign matter into the gearbox through the labyrinth seal. However, it is not particularly effective in inhibiting the passage of oil or the like in the other direction, i.e. from inside the gearbox to outside the gearbox through the labyrinth seal. It is accordingly desirable to inhibit the passage of oil from the interior of the gearbox into the labyrinth seal.

To this end, a plurality of radially outwardly directed axially arranged annular ribs or peaks is provided on the surface of the labyrinth ring defining the annular gap. The ribs are machined into the surface of the labyrinth ring using a lathe and a conventional cutting tool having a tapered nose. This results in each rib having a generally v-shaped cross-section having an axially inner surface which is inclined axially outwardly and an axially outer surface which is inclined axially inwardly. The inner and outer surfaces of each rib are typically arranged symmetrically about a plane which extends perpendicular to the axis of rotation. In particular the axially inner and outer surfaces typically define an included angle of about 60°.

The purpose of the ribs is, as the labyrinth ring rotates, to displace oil which enters the annular gap outwardly under the influence of centripetal forces and inhibit its entry into the labyrinth seal. However, by virtue of the axially outward inclination of the axially inner surface of each rib the force applied to oil which flows along and is discharged from the axially inner surfaces of the ribs has both a radial component and an axial component which can discharge the oil towards the inner end of the labyrinth seal.

It is an object of this invention to provide means which the inventor believes will at least ameliorate this problem.

According to one aspect of the invention there is provided a seal arrangement for providing a seal between a shaft and a housing through which the shaft extends, the seal arrangement including a primary seal and at least one outwardly directed protrusion which is mounted for rotation together with the shaft about an axis of rotation and which is positioned inwardly of the primary seal to inhibit the flow of oil contained in the housing towards the primary seal, the protrusion having an axially inner surface and an axially outer surface, the axially inner surface extending at an angle of at least 0° in an inward direction relative to a plane which is perpendicular to the axis of rotation.

In other words, the axially inner surface will extend perpendicular to the axis of rotation or inwardly such that any axial component of force exerted on oil flowing along the axial inward surface will be at most perpendicular to the axis of rotation or axially inwardly thereby inhibiting the flow of oil towards the primary seal.

The protrusion may be in the form of an annular rib.

The seal arrangement may include a plurality of axially spaced ribs.

The primary seal may be in the form of a labyrinth seal. More particularly, the seal arrangement may include an annular bearing cover which is mounted to the housing and a labyrinth ring which is mounted to the shaft for rotation therewith, the bearing cover and labyrinth ring having complementary concentric annular ribs and recesses which overlap in an axial direction to form the labyrinth seal.

The rib(s) may be positioned adjacent to an operatively inner or upstream end of the labyrinth seal. In a preferred embodiment of the invention, the ribs are provided on the labyrinth ring.

The rib(s) may comprise an inner surface (an upright surface) substantially parallel to a plane perpendicular to the axis of rotation and an outer surface (a sloping surface) sloping with respect to the plane perpendicular to the axis of rotation. The angle between the upright surface and the sloping surface (the rib angle) may be less than 60 degrees. Advantageously, the rib angle may be less than 50 degrees, or less than 45 degrees. In one particular embodiment, the rib angle is approximately 30 degrees.

According to another aspect of the invention there is provided a labyrinth ring for use in the seal arrangement.

According to another aspect of the invention there is provided a gearbox having a housing and two parallel shafts which are mounted to the gearbox for rotation about axes of rotation, the shafts being drivingly interconnected by gears mounted on each of the portions of the shafts positioned within the gearbox, at least one of the shafts penetrating the gearbox housing and having a seal arrangement of the type described above to provide a seal between the housing and the portion of the shaft penetrating the housing.

A bearing may be mounted in the housing and support the shaft for rotation about an axis of rotation, the bearing being positioned adjacent to the seal 10 arrangement.

The seal arrangement may include an annular oil flinger mounted to the shaft and positioned between the bearing and an annular gap having a radially inner surface formed by the labyrinth ring and a radially outer surface formed by the bearing cover, the or each rib being provided on and protrude outwardly from the surface of the labyrinth ring forming the radially inner surface of the annular gap.

The gearbox may form part of an exciter of the type described above.

According to another aspect of the invention, there is provided a method of modifying an article of equipment which includes a labyrinth seal including a labyrinth ring incorporating at least one radially outwardly directed rib which in use is positioned upstream of the labyrinth seal, the or each rib having a generally v-shaped cross-section having an axially inner surface which is inclined axially outwardly and an axially outer surface which is inclined axially inwardly, which method includes the step of removing the labyrinth ring and replacing it with a labyrinth ring forming part of the seal arrangement in accordance with the invention.

The article of equipment may comprise an exciter.

According to yet another aspect of the invention, there is provided a seal arrangement for providing a seal between a shaft and a housing through which the shaft extends, the seal arrangement including a primary seal and at least one outwardly directed protrusion which is mounted for rotation together with the shaft about an axis of rotation and which is positioned inwardly of the primary seal to inhibit the flow of oil contained in the housing towards the primary seal, the protrusion having an axially inner surface and an axially outer surface, the axially inner surface extending in a radial direction and substantially parallel to a plane which is perpendicular to the axis of rotation.

These and other aspects of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows a three-dimensional view of an exciter in accordance with one embodiment of the invention; Figure 2 shows another three-dimensional view of the exciter of Figure 1; Figure 3 shows an axial sectional elevation taken at in Figure 2; Figure 4 shows, on an enlarged scale, an upper part of a seal arrangement of the exciter of Figure 1; Figure 5 shows, on an enlarged scale, a lower part of the seal arrangement of the exciter of Figure 1; Figure 6 shows a sectional view of a prior art seal arrangement of an exciter, including on an enlarged scale, details of a rib arrangement in the prior art seal arrangement; and Figure 7 shows on an enlarged scale, the ribs of the seal arrangement of Figure 4.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT

The following description of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that many changes can be made to the embodiments described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances, and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not a limitation thereof.

In the drawings, reference numeral 10 refers generally to an exciter in accordance with an embodiment of the invention.

The exciter 10 includes a housing or gear box 12 and two parallel shafts 14, 16 which are mounted to the gear box for rotation about parallel axes 18, 20. The shafts 14, 16 are drivingly interconnected by gears 22 (one of which is shown in Figure 3 of the drawings) mounted on each of the portions of the shafts 14, 16 positioned within the gearbox 12 such that the shafts 14, 16 rotate in opposite directions.

End portions 14.1, 16.1 of each of the shafts 14, 16 protrude from the gearbox 12 and eccentric weights 24 are mounted on the protruding end portions 14.1, 16.1, such that rotation of the shafts 14, 16 sets up a vibration which can be transmitted to a screen (on which the exciter 10 may be mounted, and of which the exciter 10 may be a part) or the like. A power source such as an electric motor (not shown) is drivingly connected to one of the shafts 14,16.

The shafts 14, 16 are supported in bearings 26 (best seen in Figure 3) mounted in the gearbox 12. Oil is contained in the gearbox 12 to lubricate the gears 22 and the bearings 26. To prevent the oil escaping from the gearbox 12, a seal arrangement, generally indicated by reference numeral 28, is provided at each of the points where the shafts 14, 16 penetrate the gearbox 12. Each of the seal arrangements 28 is substantially identical and accordingly only one of the seal arrangements is described in more detail.

With a view to providing some context to the invention, prior to describing the seal arrangement 28 in detail, reference is made to Figure 6 of the drawings, in which reference numeral 30 refers generally to a prior art seal arrangement.

The seal arrangement 30 includes a labyrinth ring 32 which is mounted to the associated shaft 14 for rotation therewith and an annular bearing cover 34 which is mounted to the gearbox housing. The labyrinth ring 32 includes an inner annular collar 36 which is a friction fit on the shaft 14 and an annular web 38 which protrudes from the collar 36. Radially spaced concentric annular ribs 40 and 42 protrude from the web 38 such that an annular recess 44 is defined between the ribs 40, 42 and an annular recess 46 is defined between the collar 36 and the rib 40.

The bearing cover 34 includes an annular outer collar 48 and an annular web 50 which protrudes radially inwardly from a radially inner surface of the collar 48. Radially spaced axially extending ribs 52, 54 protrude from the web and define concentric axially extending recesses 56, 58 between the ribs 52, 54 and between the collar 48 and the rib 52. The ribs 40, 42, 52, 54 and recesses 42, 44, 56, 58 are arranged such that the ribs 40, 42 are received, with clearance, in the recesses 58, 56 and the ribs 52, 54 are received, with clearance, in the recesses 44, 46 such that they together define a primary or labyrinth seal, generally indicated by reference numeral 60.

An annular oil flinger generally indicated by reference numeral 62 is mounted on the shaft 14 axially inwardly of the labyrinth ring 32 and adjacent the bearing 26.

Adjacent to an operatively inner end of the labyrinth seal 60 the labyrinth ring 32 and bearing cover 34 define between them an annular gap 64. More particularly the annular gap 64 is defined between a radially outer surface of the collar 36 and a radially inner surface of the rib 54. The oil flinger 62 is positioned adjacent to an axially inner end of the gap 64.

By virtue of the convoluted path defined by the labyrinth seal 60 and the fact that centripetal forces will urge matter contained in the path in an outer direction, the labyrinth seal 60 is effective in inhibiting the ingress of foreign matter from entering the gearbox through the labyrinth seal. Further, if desired, an elastomeric seal can be provided in the pathway of the labyrinth seal.

However, by virtue of the centripetal forces, oil entering the inner end of the pathway may work its way outwardly and be discharged from the labyrinth seal and it is accordingly desirable to inhibit the entry of oil which passes the oil flinger 62 into the labyrinth seal.

To this end, the prior art seal arrangement 30 includes three axially spaced annular ribs 66. The ribs 66 are machined into the radially outer surface of the collar 36 in a conventional fashion making use of a lathe and a cutting tool having a tapered nose. This results in each rib 66 having a generally inverted V-shaped cross-section having an axially inner surface 68 and an axially outer surface 70. The inner and outer surfaces 68, 70 are typically arranged symmetrically about a plane which extends perpendicular to the axis of rotation and in the prior art of which the Inventor is aware they define an included angle of about 60°.

The Inventor has found that, by virtue of the centripetal forces acting on any oil on the surfaces of the ribs 66, the oil is subjected to a force which has both a radial component and an axial component by virtue of the inclination of the surfaces 68, 70. Accordingly, oil which flows along the inner surfaces 68 may well be displaced in the direction of the labyrinth seal 60 which eventually could lead to oil seepage through the seal 60.

Reference is now made to Figures 4, 5 and 7 of the drawings, in which, unless otherwise indicated, the same reference numerals used above are used to designate similar parts.

The main difference between the seal arrangement 30 and the seal arrangement 28 is in the configuration of the ribs 166 in Figure 7 compared with ribs 66 in Figure 6. In particular, in the seal arrangement 28, the inner surface 168 of each rib 166 lies in a plane which is perpendicular to the axis of rotation.

Accordingly, oil which is on the axially outer surfaces 170 of the ribs 166 will be provided with both a radial component and an axial component which urges the oil back towards the interior of the gearbox 12 (due to the inward slope of outer surface 170). However, oil which is on the axially inner surfaces 168 of the ribs 166 of the seal arrangement 28 is provided with a radial component of force but no axial component which thereby reduces the risk that the oil will be urged to flow in the direction of the labyrinth seal 60 which, the Inventor believes will reduce the risk of the oil entering and seeping from the labyrinth seal 60. In this embodiment, the axially inner surface 168 and the axially outer surface 170 define an angle of approximately 30 degrees, which is half the angle of the prior art design of Figure 6.

It will be appreciated, that the seal arrangement 30 of an exciter can be replaced with the seal arrangement 28. Further, the exciter incorporating the seal arrangement 30 may be modified by simply replacing the labyrinth ring 32 of the seal arrangement 30 with a labyrinth ring incorporating the modified ribs, described above, or by replacing the entire seal arrangement 30 with a new labyrinth ring and complementary bearing cover, thereby creating exciter 10 rather than the prior art exciter.

Claims

CLAIMS1. A seal arrangement for providing a seal between a shaft and a housing through which the shaft extends, the seal arrangement including a primary seal and at least one outwardly directed protrusion which is mounted for rotation together with the shaft about an axis of rotation and which is positioned inwardly of the primary seal to inhibit the flow of oil contained in the housing towards the primary seal, the protrusion having an axially inner surface and an axially outer surface, the axially inner surface extending at an angle of at least 0° in an inward direction relative to a plane which is perpendicular to the axis of rotation.
2. A seal according to claim 1, wherein the axially inner surface extends perpendicular to the axis of rotation or inwardly such that any axial component of force exerted on oil flowing along the axial inward surface is at most perpendicular to the axis of rotation or axially inwardly thereby inhibiting the flow of oil towards the primary seal.
3. A seal according to claim 1 or 2, wherein the protrusion is in the form of an annular rib.
4. A seal according to any preceding claim, wherein the seal arrangement includes a plurality of axially spaced ribs.
5. A seal according to any preceding claim, wherein the primary seal comprises a labyrinth seal.
6. A seal according to claim 5, wherein the seal arrangement includes an annular bearing cover which is mounted to the housing and a labyrinth ring which is mounted to the shaft for rotation therewith, the bearing cover and labyrinth ring having complementary concentric annular ribs and recesses which overlap in an axial direction to form the labyrinth seal.
7. A seal according to claim 6, wherein the ribs are positioned adjacent to an operatively inner or upstream end of the labyrinth seal.
8. A seal according to claim 6 or 7, wherein the ribs are provided on the labyrinth ring.
9. A gearbox having a housing and two parallel shafts which are mounted to the gearbox for rotation about axes of rotation, the shafts being drivingly interconnected by gears mounted on each of the portions of the shafts positioned within the gearbox, at least one of the shafts penetrating the gearbox housing and having a seal arrangement, as claimed in claim 1, to provide a seal between the housing and the portion of the shaft penetrating the housing.
10. A method of modifying an article of equipment which includes a labyrinth seal including a labyrinth ring incorporating at least one radially outwardly directed rib which in use is positioned upstream of the labyrinth seal, the or each rib having a generally v-shaped cross-section having an axially inner surface which is inclined axially outwardly and an axially outer surface which is inclined axially inwardly, which method includes the step of removing the labyrinth ring and replacing it with a labyrinth ring forming part of the seal arrangement, as claimed in claim 1.