Bearing isolator with porous seal

A bearing isolator assembly for sealing a rotating shaft with a porous sealing element including a rotor configured to sealingly engage with a shaft, and a stator configured to sealingly engage with a housing of an assembly. The rotor and stator are configured to engage with each other to define a labyrinthine pathway and one or more cavities, in which may be disposed a unitizing element and a porous sealing element. The porous sealing element provides a barrier to particulate contaminants from entering the interior of the housing, and to prevent egress of lubricants from the interior of the housing. The unitizing element limits axial and/or radial movement of the rotor with respect to the stator, and helps prevent wear of the rotor and/or stator by helping prevent the rotor from contacting the stator during operation.

FIELD OF THE INVENTION

The present invention relates to rotary shaft seals. More particularly, the invention relates to labyrinth seals.

BACKGROUND

Labyrinth-type rotary shaft seals typically include two concentric ring structures which comprise a rotor and a stator. The rotor is sealingly engaged with a rotating shaft and the stator is sealingly engaged with a bearing housing. Many different types of seals have been used to try to seal the space between the spinning rotor and the fixed stator. These include O-rings, rubber lip seals, and labyrinth paths. Labyrinth type seals tend to be the most effective type of seal. Specifically contoured pathways or grooves are formed on the interior surfaces of the seal rings to create a labyrinth extending between the exterior of the bearing housing and the interior of the bearing housing. The labyrinth pathway serves as a hydrodynamic barrier to maintain fluid lubricants within the bearing housing and prevent contaminants from entering the bearing housing. The more elaborate the pathway, the less chance there is that contaminating materials will pass through the structure and into the bearing housing.

In addition, in a typical rotor and stator configuration, some minimum clearance must be maintained to keep the rotor and stator from contacting one another. In some applications, such as aircraft landing gear, the rotor may spin at speeds in excess of about 5000 rpm. If a surface of the rotor contacts a surface of the stator at these speeds, frictional heat develops, the components wear, and the overall efficiency and working life of the apparatus declines. It is, therefore, important to keep the rotor and stator separate.

Further, seals are used to prevent the migration of contaminants from the exterior of the bearing housing and rotor to the interior, as well as prevent loss of lubricating fluid from the interior of the bearing housing and rotor. Contaminants which migrate into the system need to be expelled quickly. Build up of particulate matter within the seal or housing can damage the seal and/or cause increased wear of the rotor and stator. Furthermore, any lubricating fluid forced out of the system must likewise be recaptured and returned to the interior of the rotor. Loss of lubricating fluid will lead to damaged parts and increase the frictional heat of the system

Contaminants which do migrate into the system need to be expelled as quickly as possible. Build up of particulate matter can damage the seal and/or cause increased wear of the rotor and stator. Furthermore, any lubricating fluid forced out of the system must likewise be recaptured and returned to the interior of the rotor. Loss of lubricating fluid will increase the frictional heat of the system and will lead to damaged parts.

It would, therefore, be desirable to provide a labyrinth sealing device with improved particulate exclusion characteristics which would be particularly useful in dusty environments, such as coal pulverizers and cement grinders, as well as an improved capability to reduce the chance or duration of contact between the rotor and stator.

It is to these perceived needs that the present invention is directed.

SUMMARY

An embodiment of the present invention provides a seal comprising a rotor configured to sealingly engage with a shaft, and a stator configured to sealingly engage with a housing. The stator and rotor are configured to engage with each other to define a labyrinthine pathway. A unitizing element and a porous sealing element may be disposed within the labyrinthine pathway to provide contaminant exclusion characteristics and reduce the chance of the rotor and stator contacting each other.

As will be realized by those of skill in the art, many different embodiments of a seal with a unitizing element and a porous sealing element are possible. Additional uses, objects, advantages, and novel features of the invention are set forth in the detailed description that follows and will become more apparent to those skilled in the art upon examination of the following or by practice of the invention.

DETAILED DESCRIPTION

An embodiment of the present invention comprises a rotor, a stator, a unitizing element, and a porous sealing element for use between a rotating shaft and a bearing housing. The rotor is configured to engage and rotate with a shaft located within a housing, while the stator is configured to engage with and remain stationary with respect to the housing. The rotor and stator are also configured to engage each other, but not to contact each other, though contact may occur. When engaged, the rotor and stator define a labyrinthine pathway extending from the exterior of the housing to the interior of the housing, as well as a first and second cavity. The labyrinthine pathway may help prevent the migration of lubricants from the interior of the housing, and/or may help prevent the migration of contaminants into the interior of the housing. The first cavity is configured to receive a unitizing element, and the second cavity is configured to receive a porous sealing element.

In an embodiment, the unitizing element is an annular ring shaped to fit one or more of the cavities defined by the rotor and stator. The unitizing element unitizes the rotor and stator, and may prevent separation and may restrict movement. This unitizing element may also contain a rear member which, in the case of axial movement, may provide a non-metallic component to prevent contact of the rotor and stator. In addition, a porous sealing element may be disposed within at least one of the annular cavities. The porous sealing element may increase the airborne particulate exclusion capability of the seal formed by the rotor and stator by providing a physical barrier for particulate matter.

An illustrative embodiment of the present invention comprises a rotor that is configured to engage and rotate with the shaft, while a stator is configured to engage with and remain stationary with respect to the housing. The rotor and stator engage and define a labyrinthine pathway which may connect the exterior of the housing to the interior of the housing. While engaged, the rotor and stator may be configured to remain out of contact with each other to prevent wear of their respective components. The labyrinthine pathway may be configured to help prevent the migration of contaminants into the interior of the housing, as well as help prevent the migration of lubricating material to the exterior of the housing. As contaminants attempt to pass along the labyrinthine pathway towards the interior of the housing, the shape of the pathway may aid in impeding the contaminants' movement. In addition, contaminants may encounter the porous sealing element. The porous sealing element may be configured to prevent the contaminants from passing through the porous sealing element. For example, if the pores within the porous sealing element have a pore diameter smaller than the diameter of a contaminant particle, that particle may be prevented from passing through the porous sealing element. Further, as lubricating fluid travels within the pathway, it may be guided back towards the interior of the housing by the shape of the labyrinthine pathway. In addition, the lubricating fluid may be prevented from escaping the housing by the porous sealing element.

The invention will now be further described by way of specific embodiments thereof, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention. Exemplary embodiments of the present invention are shown in the figures where like numerals refer to like aspects of the various embodiments.

Referring now toFIGS. 1-4, a bearing isolator according to one embodiment of the present invention comprises a stator10, a rotor50, a unitizing element30and a porous sealing element40. The rotor50and the stator10engage to form labyrinthine pathway20, as well as first cavity90and second cavity80. Unitizing element30and porous sealing element40are disposed within the cavities80,90. In an embodiment of the present invention, the rotor50and stator10may only define one cavity, wherein both the unitizing element30and the porous sealing element40may be disposed. As the rotor50turns, the unitizing element30may prevent the rotor50from contacting the stator10by providing a low friction buffer between the two components, and further may retain lubrication within and exclude contaminants from the bearing housing. Further, the porous sealing element40may provide a barrier to prevent contaminants from entering the housing, and may prevent lubrication from exiting the bearing housing.

A porous sealing element40, according to an embodiment of the present invention, may comprise a microcellular material. For example, in one embodiment of the present invention, the microcellular material may comprise a silicone foam. In an embodiment of the present invention, the porous sealing element40may comprise one or more resins, such as polyurethane, polysulfone, or polyethylene. In an embodiment of the present invention, the porous sealing element40may comprise a fibrous material.

Some embodiments of the present invention may comprise porous sealing element40, wherein the pores defined within the porous sealing element40may have a diameter of approximately 500 to 600 microns (approximately 0.020 to 0.023 inches). In some embodiments of the present invention, the porous sealing element40may have a diameter less than approximately 100 microns (approximately 0.004 inches). Some embodiments of the present invention may comprise pores with diameters greater than or equal to 100 microns.

In some embodiments of the present invention, a plurality of porous sealing elements may be used. In an embodiment of the present invention, each of the plurality of porous sealing elements may comprise pores of approximately the same diameter. In another embodiment of the present invention, each of the plurality of porous sealing elements may comprise pores having different diameters. For example, a seal according to the present invention may comprise two porous sealing elements, where the first porous sealing element has pores with diameters larger than the pores of the second porous sealing element. In still another embodiment of the present invention comprising a plurality of porous sealing elements, some of the plurality of porous sealing element may comprise pores having approximately the same diameters, while some of the porous sealing elements may comprise pores having different diameters.

In an embodiment of the present invention, the unitizing element30may be configured to limit the radial and/or axial movement of the rotor50with respect to the stator10. For example, while the shaft and rotor50are in motion, there may be loads placed upon the shaft and/or housing causing the shaft and rotor50to move axially with respect to the housing and stator10(i.e. move along the axis of rotation). This movement may cause the rotor50to move towards the stator10. The unitizing element30may provide resistance to that axial movement and may help prevent the rotor50from contacting the stator10, thereby potentially damaging the rotor50and/or the stator10. Further, if a load is put on the shaft which causes it to move radially with respect to the shaft (i.e. move perpendicularly to the axis of rotation), the unitizing element30may provide resistance to that radial movement, and may help prevent the rotor50from contacting the stator10, again potentially preventing damage to the rotor50and/or the stator10. In an embodiment of the present invention, the unitizing element30may comprise a void that allows a portion of the unitizing element to deflect and thereby absorb some force caused by axial and/or radial motion of the rotor with respect to the stator.

An embodiment of the present invention may comprise a plurality of unitizing elements. For example, it may be advantageous to incorporate multiple unitizing elements into a bearing seal according to an embodiment of the present invention for use in an environment where significant axial or radial loads are expected on the rotor and/or stator. The use of multiple unitizing elements may spread help extend the functional life of the bearing seal by spreading the force of contact of the rotor across multiple unitizing elements. The use of multiple unitizing elements may also provide increased contaminant exclusion or lubricant retention characteristics.

In an embodiment of the present invention, the unitizing element30of the present invention comprises a material suitable for its intended purpose. The selection of such a material may be made based on one or more factors including, but not limited to, anticipated operating temperature ranges, operating pressure ranges, coefficient of friction of the material, or other operating conditions (such as the likelihood of significant axial or radial movement of the rotor, as in aircraft landing gear, or a very dirty environment). Common materials for use in a unitizing element30that may be used in some embodiments of the present invention comprise fluorinated polymers or resins. In one embodiment of the present invention, the unitizing element30comprises a lubricious plastic material. In another embodiment of the present invention, the unitizing element30comprises rubber, such as hydrogenated NBR. In another embodiment of the present invention, the unitizing element30comprises polytetrafluoroethylene (PTFE). In an embodiment of the present invention, the unitizing element30comprises filled PTFE. Filled PTFE comprises PTFE with a filler dispersed throughout. Fillers include, but are not limited to, structural fillers such as glass, and lubricants such as graphite, molybdenum disulphide, other carbon fillers, and other solid lubricants.

The unitizing element30may be viewed in more detail inFIG. 5, which shows a cross-sectional view of the unitizing element. Viewed in cross section, the unitizing element comprises a rotor engaging member33, a rear member32and an stator engaging member31.

In one embodiment of the present invention, the radially outer surface of the unitizing element comprises two areas of differing diameter. The differing diameters include, one diameter in the area of the rear member32and a differing diameter in the area of the rotor engaging member33. A wall34is formed by the disparity in diameter between the rear member32and the rotor engaging member33. This wall34may function to retain the unitizing element within a rotor50during assembly, and/or to unitize the rotor50and stator10after assembly. In a preferred embodiment of the present invention, the wall34is positioned at about the axial midpoint of the unitizing element. However, one skilled in the art will recognize the position of the wall34may vary. For example, in an embodiment of the present invention, the position of the wall34may depend on the functionality required of the unitizing element and/or the configuration of the rotor and stator assembly. In a preferred embodiment of the present invention, the wall34is substantially perpendicular to the axis of rotation.

The stator engaging member31extends from the radially inner side of the unitizing element30. The stator engaging member31extends from about the midpoint of the unitizing element30at an angle. The length and location of the stator engaging member31may depend upon rotor50and/or stator10characteristics, and/or ease of assembly concerns. The stator engaging member31may have sufficient strength to unitize the sealing assembly, while being flexible enough to deflect during assembly. In an embodiment of the present invention, there may a void35formed by the area between the rotor engaging member33and the stator engaging member31. This void35may provide an area for the stator engaging member31to deflect into when the rotor50, stator10, porous sealing element40, and unitizing element30are brought together into a sealing assembly.

The dimensions of the wall34, rear member32, rotor engaging member33and stator engaging member31as well as that of the unitizing element30itself may vary according to the intended use of the unitizing element. These modifications in dimension will be apparent to one skilled in the art and fall within the scope of this invention. Thus, a unitizing element30according to an embodiment of the present invention is not limited to sealing applications of any particular size, and has a wide range of uses.

In an embodiment of the present invention, viewable inFIGS. 6 and 7, a sealing assembly is provided comprising a unitizing element30according to an embodiment of the present invention. The sealing assembly comprises a rotor50, stator10, porous sealing element40, and unitizing element30. The rotor50is sealingly engaged to a shaft running through the center of the sealing assembly. The rotor50comprises an axially extending annular flange52comprising a rotor groove54located on a radially inward side of the flange52. The stator10is sealingly engaged to a bearing housing and comprises an axially extending annular flange12comprising a stator groove14located on a radially outward side of the flange12. A unitizing element30comprising a rotor engaging member33, an stator engaging member31, and a rear member32resides within the area formed by the space between the rotor annular flange52and the stator annular flange12. The unitizing element30may reside partially within each of the rotor groove54and stator grove14with the rear member32extending toward the stator rear wall19.

FIG. 7shows an embodiment of the present invention without the unitizing element30in place. In one embodiment of the present invention, the sealing assembly includes a rotor50, which is sealingly engaged to the shaft by an O-ring60. The rotor includes an annular flange52, which contains a groove54located on a radially inward side thereof. The groove54comprises two opposing walls58aand58b. Similarly, the stator10comprises an annular flange12containing a groove14. The stator groove14also comprises two opposing walls18aand18b. In a preferred embodiment of the present invention, the opposing walls of the rotor groove58a,58band the opposing walls of the stator groove18a,18bare about perpendicular to the axis of the shaft.

In one embodiment of the present invention, each opposing wall of the rotor groove is axially aligned with the corresponding opposing wall of the stator groove, such that opposing wall58ais axially aligned with opposing wall18aand opposing wall58bis axially aligned with opposing wall18b. This configuration forms an area of rectangular cross section in which the rotor engaging member33and inner engagement member31of the unitizing element30are housed.

In an embodiment of the present invention, at least one of the walls of the stator groove54and corresponding wall of the rotor groove14are offset, such that one of the pairs of rotor groove wall58aor58band corresponding stator groove wall18aor18bare not in axial alignment.

In a further embodiment of the present invention, the stator10further comprises an expulsion port located on the stator's atmospheric side. The expulsion port allows any contaminants that migrate into the seal area to be expelled from the assembly.

In an embodiment of the present invention, the sealing assembly comprises the rotor50and stator10with the unitizing element30housed therein. The rotor engaging member33of the unitizing element30engages the rotor groove54such that the axially outer sides of the rotor engaging member33contact the opposing walls of the rotor groove54. In an embodiment of the present invention, the rotor engaging member33“floats” within the rotor groove54so as to minimize contact and friction during operation. When there is an axial shift of the rotor and stator relative to each other, the rotor engaging member36may then contact the corresponding wall of the rotor groove54.

Similarly, the stator engaging member31contacts the stator groove and/or the groove wall18a. During operation, the unitizing element “floats” within the cavity formed between the rotor and stator. However, the stator engaging member31, being flexibly attached to the unitizing element30, may provide a means to keep the unitizing element30in position by contacting the wall18aof the stator groove14should the assembly shift during operation.

In an embodiment of the present invention, the unitizing element30also contains a rear member32. The rear member32may prevent the rotor50and stator10from directly contacting one another in the event of axial movement toward each other. If the rotor50shifts toward the stator10, the rear member32of the unitizing element30may contact the rear wall of the stator19before the rotor50and stator10make direct contact. The rotor50may contact and/or press against the unitizing element30via one of the opposing walls58aof the rotor groove54. This action may force the rear member34of the unitizing element30against the stator rear wall19. In an embodiment where the unitizing element30is constructed of a lubricious plastic material, the frictional force between the unitizing element30and the rotor50, and the unitizing element30and the stator10may be significantly less than direct contact between the rotor50and stator10. The unitizing element30thereby may provide a wear-resistant buffer between the rotor50and stator10components. This may serve to prolong the useful life of the rotor and stator by minimizing wear of these two parts. When the unitizing element30reaches the end of its useful life, it may be replaced, with less operational downtime and replacement cost than that associated with replacing the rotor and stator.

In an embodiment of the present invention, the unitizing element30unitizes the rotor50and the stator10by filling a cavity90and contacting the opposing walls of the rotor groove58a,58b. The engaging member31rests within the groove14on the stator10, but does not contact opposing walls18a,18bduring normal operation. If an axial force is applied moving the rotor50away from the stator10, opposing wall58bmay contact the rotor engaging member33in the area of the wall34. This may force the unitizing element30to move with the rotor50. Movement of the unitizing element30may be arrested by contact of the stator engaging member31with opposing wall18aof the stator groove14. By this action, the sealing assembly comprising the rotor50, unitizing element30, porous sealing element40, and stator10, may be unitized.

In an embodiment of the invention, in addition to the unitizing effect in the sealing assembly, the unitizing element30may also create a non-contacting relationship between the rotor50and stator10. In the event of axial movement of the rotor50toward the stator10, the rotor may contact the unitizing element30and force the rear member32into contact with the stator rear wall19. The unitizing element30may be designed such that the rear member32extends toward the stator farther than the rotor annular flange52. Thus, the rotor annular flange52is prevented from contacting the rear wall of the stator, thereby increasing the useful life of the rotor50and stator10by preventing undue wear of the components.

Although the present invention has been described with reference to particular embodiments, it should be recognized that these embodiments are merely illustrative of the principles of the present invention. Those of ordinary skill in the art will appreciate that the unitizing element and assembly of the present invention may be constructed and implemented with other materials and in other ways and embodiments. Accordingly, the description herein should not be read as limiting the present invention, as other embodiments also fall within the scope of the present invention.