SEAL ASSEMBLY WITH LABYRINTH CHANNEL

Abstract

A seal assembly is for sealing a rotating device and includes a dynamic seal component frictionally engageable with a device rotor and a static seal component frictionally engageable with a device stator. The two seal components are formed therebetween with a contact seal based on a sealing lip and a non-contact seal based on a labyrinth gap. The labyrinth gap is located upstream of the sealing lip on the path of foreign matter entering the seal assembly. A thrust bumper is formed in the labyrinth gap and defines a gap width by its own height during the assembly process. The rotating device may be a hub unit of a vehicle or any rotating machine with a rotor and a stator as core components. The rotating equipment adopting the present seal assembly can obtain significantly improved sealing performance, and thus is fully adapted to severely polluted or extremely humid working conditions.

Claims

1. A seal assembly for sealing the annular space between a rotor and a stator of a rotating device, the seal assembly comprising: a dynamic seal component frictionally engageable with the rotor and having a dynamic labyrinth portion; and a static seal component frictionally engageable with the stator and having a static labyrinth portion; wherein one of the dynamic seal component and the static seal component includes a sealing lip contact portion and the other one of the dynamic seal component and the static seal component including at least one sealing lip engageable with the sealing lip contact portion to form a lip-contact seal; and wherein the dynamic labyrinth portion and the static labyrinth portion form a labyrinth non-contact seal with a labyrinth channel located upstream of the lip-contact seal on a path of foreign matter entering the seal assembly and a thrust bumper extends from the dynamic labyrinth portion or from the static labyrinth portion, the thrust bumper having a height defining a gap width of the labyrinth channel during assembly of the dynamic seal component and the static seal component and the thrust bumper is configured to be at least partially abraded during use of the rotating device.

2. The seal assembly according to claim 1, wherein the thrust bumper is formed as a plurality of protrusions spaced circumferentially apart about a centerline of the seal assembly.

3. The seal assembly according to claim 2, wherein the plurality of protrusions are equally spaced about the centerline of the seal assembly.

4. The seal assembly according to claim 2, wherein the plurality of protrusions includes between six protrusions and twelve protrusions.

5. The seal assembly according to claim 2, wherein at least a portion of each protrusion has a conical shape or a pyramidal shape.

6. The seal assembly according to claim 1, wherein: the rotating device is a vehicle wheel end assembly, the rotor is a vehicle hub, and the stator is a vehicle axle; the at least one sealing lip is formed on the dynamic seal component, the dynamic labyrinth portion being located radially outwardly of the at least one sealing lip; the sealing lip contact portion is formed on the static seal component, the labyrinth static portion being located radially outwardly of the sealing lip contact portion; the at least one sealing lip and the sealing lip contact portion form the lip-contact seal and the dynamic labyrinth portion and the static labyrinth portion form the labyrinth channel when the dynamic seal component and the static seal component are assembled; and the thrust bumper is formed on the dynamic labyrinth portion and abuts the static labyrinth portion to limit the gap width of the labyrinth channel during assembly of the dynamic and static seal components, the thrust bumper having an outer tip which is abraded by contact with the static labyrinth portion during use of the rotating device.

7. The seal assembly according to claim 6, wherein: the static seal component includes a rigid annular case, the case having C-shaped axial cross-sections and an open side facing the dynamic seal component, the case being formed with a bent portion on the radial outer edge on the open side providing the static labyrinth portion and an outer circumferential surface on the open side providing the sealing lip contact portion; and the dynamic seal component includes a seal member with a mating portion spaced axially and radially from the bent portion of the static seal component and providing the dynamic labyrinth portion, the seal member mating portion cooperating with the case bent portion to form the labyrinth channel.

8. The seal assembly according to claim 7, wherein the case of the static seal component is formed as a metal stamping and the dynamic labyrinth portion is formed with a groove located adjacent to a sheared edge of the case bent portion so as to provide clearance from any burrs on the metal stamping.

9. The seal assembly according to claim 7, wherein the labyrinth channel is formed with at least one turn partially defined by an inner circumferential surface of the seal mating portion and has an axial opening facing the inboard side of the seal assembly.

10. The seal assembly according to claim 9, wherein the inner circumferential surface of the seal mating portion has an outward inclination angle with a value of between five degrees and fifteen degrees.

11. The seal assembly according to claim 7, wherein: the at least one sealing lip includes two axial sealing lips and two radial sealing lips; and the two axial sealing lips are both inclined radially outwardly and a radially outer one of the two axial sealing lips has a length significantly greater than a length of a radially inner one of the two axial sealing lips.

12. A rotating device comprising: a rotor; a stator; and a seal assembly including: a dynamic seal component frictionally engageable with the rotor and having a dynamic labyrinth portion; and a static seal component frictionally engageable with the stator and having a static labyrinth portion; wherein one of the dynamic seal component and the static seal component includes a sealing lip contact portion and the other one of the dynamic seal component and the static seal component including at least one sealing lip engageable with the sealing lip contact portion to form a lip-contact seal; and wherein the dynamic labyrinth portion and the static labyrinth portion form a labyrinth non-contact seal with a labyrinth channel located upstream of the lip-contact seal on a path of foreign matter entering the seal assembly and a thrust bumper extends from the dynamic labyrinth portion or from the static labyrinth portion, the thrust bumper having a height defining a gap width of the labyrinth channel during assembly of the dynamic seal component and the static seal component and the thrust bumper is configured to be at least partially abraded during use of the rotating device.

13. A seal assembly for sealing the annular space between a rotor and a stator of a rotating device, the seal assembly comprising: a static inner seal component frictionally engageable with the stator and including an annular case with a radially outwardly extending bent portion; and a dynamic outer seal component frictionally engageable with the rotor and including an annular case and an elastomeric seal member disposed on the case, the seal member having at least one sealing lip engageable with the case of the inner seal component, a mating portion disposed adjacent to and spaced axially and radially from the bent portion of the inner seal component case so as to define a labyrinth channel with a radial section and an axial section, and a thrust bumper extending axially from the mating portion and having an outer end contacting the bent portion of the inner seal component case so as to define a gap width of the labyrinth channel during assembly of the inner seal component and the outer seal component.

14. The seal assembly according to claim 13, wherein the thrust bumper is configured to be at least partially abraded during use of the rotating device.

15. The seal assembly according to claim 14, wherein the thrust bumper is formed as a continuous annular shoulder or as a plurality of protrusions spaced circumferentially about a centerline of the seal assembly.

16. The seal assembly according to claim 13, wherein the at least one sealing lip includes two radial sealing lips engageable with an outer circumferential surface of the case of the inner seal component and two axial sealing lips engageable with a radial surface of the case of the inner seal component.

17. The seal assembly according to claim 13, wherein the mating portion of the seal member has a radial section spaced axially from the bent portion of the inner seal component case so as to define the radial section of the labyrinth channel and an axial section spaced radially outwardly from the bent portion the inner seal component case so as to define the axial section of the labyrinth channel.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0014] 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:

[0015] FIG. 1 is a schematic axial cross-sectional view of a truck wheel end assembly;

[0016] FIG. 2 is a broken-away, enlarged axial cross-sectional view of a prior art seal assembly disposed within the wheel end assembly of FIG. 1;

[0017] FIG. 3 is a broken-away, axial cross-sectional view of an improved seal assembly according to the present invention;

[0018] FIG. 4 is an enlarged view of a portion of FIG. 3, showing a labyrinth channel of the present seal assembly; and

[0019] FIG. 5 is an enlarged, perspective view of a protrusion forming a thrust bumper of the present seal assembly.

DETAILED DESCRIPTION OF THE INVENTION

[0020] 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. Further, as used herein, the words “connected” and “coupled” are each intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import. In addition, the same reference numerals are used throughout the drawings to denote the same or similar components.

[0021] FIG. 3 shows an axial cross-sectional view of an improved sealing assembly 11 of the present invention. In the illustrated embodiment, the seal assembly 11 is generally annular with a centerline L.sub.C and includes an outer annular seal component 20 and an inner annular seal component 30. In a presently preferred embodiment, the outer seal component 20 is a dynamic seal component frictionally engageable with a rotor 2 and has a dynamic labyrinth portion 29, the inner seal component 30 is a static seal component frictionally engageable with a stator 3 and has a static labyrinth portion 36.

[0022] The inner seal component 30 includes an annular stamping or case 32 having generally C-shaped axial cross-sections and a radial flange or “bent portion” 36 formed on the radial periphery of an open, inner side of the case 32 and providing the static labyrinth portion. The inner case 32 also has an outer circumferential surface 32C on the interior of the open side providing a sealing lip contact portion, as discussed below. The outer seal component 20 includes an annular stamping or case 22 and an elastomeric or polymeric annular seal member 24 disposed on the outer case 22 and having a “matching” or mating portion 29 providing the dynamic labyrinth portion and cooperating with the case bent portion 36 to form a labyrinth channel 44. Specifically, the seal member mating portion 29 is formed at a position corresponding to, and spaced both axially apart from and radially outwardly from, the bent portion 36 of the inner case 32, with a contour at least partially aligned with the bent portion 36 so as to “wrap about” or surround the bent portion 36 to form a curved or angled labyrinth channel 40. In other words, the labyrinth channel 40 is formed by the relative positioning of the seal mating portion 29 (i.e., the dynamic labyrinth portion) and the case bent portion 36 (i.e., the static labyrinth portion).

[0023] Preferably, the channel 40 extends both radially and axially between the case bent portion 36 and the seal mating portion 29 such that the channel 40 is “turned” or forms about a ninety-degree (90°) bend. That is, the labyrinth channel 40 preferably has a radial section 40a, which is defined between a radial surface 36A of the case bent portion 36 and a radial section 29a of the seal mating portion 29 spaced axially from the bent portion 36, and an axial section 40b defined between an outer axial end surface 36B of the case bent portion 36 and an axial section 29b of the seal mating portion 29 spaced radially outwardly from the bent portion 36, as best shown in FIG. 4.

[0024] In the improved sealing assembly 11, a thrust bumper 27 is preferably formed on and extends axially from a partially flat radial surface 29A of the inboard side of the seal mating portion 29, as best shown in FIG. 4, so as to be located within the labyrinth channel 40 after assembly of the seal components 20, 30. Being so located, the thrust bumper 27 defines the axial spacing distance between the outer seal component 20 and the inner seal component 30 by abutting against the bent portion 36 of the inner case 32 during the assembly process. Also, such a location of the thrust bumper 27 enables the bumper 27 to define the gap width of the labyrinth channel 40 as being the axial length or “height” (indicated by “h” in FIG. 4) of the bumper 27. As such, the gap width of the labyrinth channel 40 can be limited by the minimum protrusion height allowed by the seal material molding process and the labyrinth channel 40 constructed thereby is narrower than any labyrinth channel that can be formed by any other known methods. Actual measurement shows that the resulting labyrinth gap (also known as “gap width”) can be as low as one tenth of a millimeter (0.1 mm) or even less, which significantly improves the sealing capability of the labyrinth seal gap to the point of being sufficient to meet the non-contact sealing requirements under the most severe working conditions.

[0025] FIG. 4 is an enlarged view of a portion of FIG. 3, showing the labyrinth channel 40 in a state in which the thrust bumper 27 is supported on or abutted against a radial surface 36A on the inboard side of the inner case bent portion 36 after assembly of the seal components 20, 30. As depicted in FIG. 4, the thrust bumper 27 may be formed as a continuous annular rib or shoulder, i.e., continuously distributed about a circumference of the seal member 24. Preferably, the thrust bumper 27 extends axially from the radial surface 29A of the seal member 24 and circumferentially about the centerline L.sub.C, and has an outer end or tip 27a that forms a line contact (i.e., circular) with the bent portion surface 36A about the circumference. After a period of use of the seal assembly 11, the outer end/tip 27a is flattened or “disappeared” (i.e., worn away or abraded), due to the relative sliding motion between the metallic bent portion 36 of the inner case 32 and the softer, elastomeric/polymeric thrust bumper 27. As a result, the narrowest part or section of the labyrinth channel 40 is formed between the remaining part of the thrust bumper 27 and the radial surface 36A of the inner case bent portion 36.

[0026] Compared with the previously known seal shown in FIG. 2, the labyrinth channel 40 of the present seal assembly is a narrow and “turned” channel which extends both radially and axially as discussed above, and is partially defined by an axial flange section 29b of the seal mating portion 29 extending over the opening above the original thrust bumper 27 to prevent foreign matter from directly entering the inside of the seal assembly 11 from the opening. Additionally, the thrust bumper 27 also forms a narrow gap by projecting toward the bent portion surface 36A, to further increase the difficulty of foreign objects passing through the labyrinth channel 40.

[0027] Alternatively, as shown in FIG. 5, the thrust bumper 27 may be formed of a plurality of protrusions 31 spaced apart about the circumference of the seal member 24 (i.e., spaced circumferentially about the seal assembly centerline L.sub.C), with the tip/outer end 31a of each protrusion 31 collectively forming the outer end 27a of the bumper 27 and being in point contact with the bent portion surface 36A of the inner case 32. In this case, the debris generated after each tip 31a is worn or abraded away is far less than the total amount of debris generated after the continuous annular thrust bumper 27 is abraded, so as to greatly reduce the possible threat of debris as a pollutant to the downstream contact seal (see below for details) and the bearing sealed thereby.

[0028] Clearly, under the same thrust force F, the pressure borne by the thrust bumper 27 formed as a plurality of protrusions 31 each in point contact with the surface 36A is much greater than the pressure borne by a single, continuous annular thrust bumper 27 in line contact with the surface 36A. Therefore, in the case of the same initial height of the two types of bumpers 27, even considering the elastic recovery of the seal member 24, the amount of compression within the thrust bumper 27 formed as separate protrusions 31 distributed in discrete points that are compressed under the action of the thrust F will be significantly greater than the amount of compression of the thrust bumper 27 formed in a ring shape. As such, the net height (indicated by “h” in FIG. 4) after assembly of a thrust bumper 27 formed of protrusions 31 is significantly less than the net height h of a single, annular or “ring-shaped” thrust bumper 27. Therefore, when the minimum protrusion height allowed by the molding process remains the same, the labyrinth gap defined by the protrusion-formed thrust bumper 27 will also be significantly less than the labyrinth gap defined by the ring-shaped thrust bumper 27.

[0029] It should be noted that the labyrinth gap mentioned here does not refer to the narrow clearance (not shown) formed between the worn-out outer end/tip 27a and the bent portion radial surface 36A, but refers to the width h of a section of labyrinth corridor H defined by the height of the thrust bumper 27 after being squeezed during assembly of the seal components 20, 30, as indicated in FIG. 4. Obviously, the narrower labyrinth corridor defined by the net height of the protrusion-formed thrust bumper 27 can further limit the quantity and size of contaminants passing through the labyrinth channel 40.

[0030] As a further preferred embodiment, the protrusions 31 of the thrust bumper 27 may be distributed at equal intervals (i.e., angular intervals) about the circumferential direction or centerline L.sub.C, the present optimal number of protrusions 31 being between six (6) and twelve (12). The equal height thrust bumpers 27 evenly distributed about the circumference can obviously form a labyrinth corridor with equal gap width in the labyrinth channel 40.

[0031] The protrusions 31 of the thrust bumper 27 may be formed such that at least a portion of each protrusion 31 has a conical shape or a pyramidal shape, as shown in FIG. 5. Although such protrusions 31 have a relatively sharp tip 31a that is more likely to be worn off, resulting in “safe debris” with relatively large particles, but such particles are relatively fewer in number. Such particles are called “safe debris” because such debris is more likely to be blocked by the downstream lip-contact seal, as described below, and therefore less likely to pose a threat to a bearing protected by the seal assembly 11. On the other hand, the tapered tip 31a of such protrusions 31 can provide a greater compression ratio so as to define a narrower labyrinth corridor after compression.

[0032] As mentioned above, the inner and outer cases 32, 22, respectively, are preferably fabricated as metal stampings. Due to the nature of the stamping process, the stamped cases 32, 22 may occasionally have metal burrs remaining on any sheared edges, for example, protruding beyond the angular edge 37 of the bent portion 36 of the inner case 32. Such metal burrs may damage the mating portion 29 of the elastomeric/polymeric seal member 24 during the operation of the seal assembly 11, thereby causing damage to the formed labyrinth channel 40. To prevent such damage, the mating portion 29 of the seal member 24 may be provided with an annular groove 29B at a position corresponding to (i.e., located adjacent to) the edge 37 to avoid contact of possible metal burrs on the inner case 32 with the seal member 24. Although the groove 29B may cause the local broadening in the labyrinth channel 40, it will not significantly affect the overall sealing capability of the seal assembly 11.

[0033] As shown in FIG. 4, the labyrinth channel 40 preferably has substantially L-shaped axial cross sections, with a “right-angle” bend formed at a position corresponding to the inner case annular edge 37 and with the channel 40 opened toward the inboard side. Specifically, the labyrinth channel 40 has a radially-extending section 40a and an axially-extending section 40b, with the axially-extending section 40b preventing contaminants from directly entering the remainder of the labyrinth channel 40 under the action of gravity. Thus, the L-shaped bend further increases the difficulty of contaminants passing through the labyrinth channel 40.

[0034] To further improve the sealing efficiency or protective effect, the mating portion 29 of the seal member 24 has an inner circumferential surface 29C at the opening 41 of the labyrinth channel 40 which preferably defines an angle α with respect to the axial direction, and thus with respect to the seal assembly centerline L.sub.C. When the outer seal component 20 rotates with the hub 2, the angle α of the inner surface 29C is favorable for centrifugal force to direct contaminants, such as mud, outwardly from the channel 40 through the channel opening 41. Preferably, the inclination angle α is between five degrees (5°) and fifteen degrees (15°).

[0035] On the path of foreign matter intruding into the hub 2, the labyrinth channel 40 is located upstream of the sealing lips 26. To further improve the contact sealing effect, the present seal assembly 11 also increases the number of sealing lips 26 from three to four. The improved sealing lips 26 include two radial sealing lips 26a, 26b and two axial sealing lips 26c, 26d, with the axial sealing lips 26c, 26d both arranged to extend obliquely outward in the radial direction and elastically lean on or engage against the “smooth” radial inner surface 32B on the open side of the inner case 32. Compared with the existing axial sealing lip 26c (such as shown in FIG. 2), the additional, radially outer axial sealing lip 26d has an elongated length significantly greater than an elongated length of the radially inner axial sealing lip 26c, which substantially reduces the contact stress of the lip 26d against the inner case 32. In addition, since a lubricant is preferably injected between the sealing lips 26a-26d to reduce contact friction, the friction increase caused by the additional sealing lip 26d is completely within an acceptable range, but the resulting improvement in the sealing effect is quite significant.

[0036] A primary factor in seal design is to obtain the highest possible sealing performance with the lowest possible frictional resistance. On the one hand, the present invention provides a narrow labyrinth channel 40 through the thrust bumper 27, thereby improving the protective performance of the non-contact portion of the seal. On the other hand, the present invention further improves the sealing effect of the contact portion of the seal by a limited increase in the number of sealing lips. Through the combination of the above two design aspects, the overall protection performance of the seal assembly 11 is significantly improved at the cost of limited increase in friction.

[0037] It can be seen from the above description that the design concept of the present invention is fully applicable to rotating equipment in a broader sense; that is, to any rotating machine that includes a dynamic rotor and a static stator, and is not limited to the vehicle hub assembly described above. It is apparent that in the present seal assembly 11, as long as the dynamic seal component is assembled on the rotor and the static seal component on the stator, a narrow labyrinth channel can be constructed through the thrust bumper 27 to improve the sealing efficiency or effect.

[0038] Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention.

[0039] Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0040] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. The invention is not restricted to the above-described embodiments, and may be varied within the scope of the following claims.