Bearing system, roll assembly, and metal coating line assembly including same

A bearing system that accepts a journal of a roll includes a housing defining a cavity and having a forward wall that defines an opening into the cavity, the opening configured to accept the journal through the opening and into the cavity. A sleeve is positioned within the cavity of the housing, the sleeve configured to surround the end of the journal. A first seal is positioned within the cavity of the housing adjacent to the forward wall of the housing, the first seal having an engagement surface. A second seal is positioned within the cavity of the housing and operably connected to the sleeve, the second seal having an engagement surface in contact with the engagement surface of the first seal.

TECHNICAL FIELD

The present invention relates to bearing systems for use with a roll assembly configured to be submerged in a corrosive environment, such as molten metal as part of a galvanizing line assembly. More specifically, the present invention relates to a bearing system that includes internal seals and a pressurized cavity which removably accepts the journal of a roll.

BACKGROUND OF THE INVENTION

The present invention relates generally to a metal coating line assembly, such as a galvanizing line assembly. A typical metal coating line assembly is used to plate a metal layer (e.g. zinc) on a steel sheet by submerging the steel sheet in a hot dipping bath of the molten plating metal.

FIG. 5illustrates a typical zinc pot in a continuous galvanizing line100. As shown inFIG. 5, a steel sheet101is continuously supplied and submerged into molten zinc103contained within a zinc pot102. As shown, the steel sheet101is turned upward by one or more roll assemblies104before exiting the molten zinc103. The coated steel sheet is cold solidified and wound into a coil through a tension reel (not illustrated).

As shown inFIG. 5, the roll assemblies104are immersed in the zinc pot102filled with hot molten zinc103having a temperature of about 450° C. to 460° C. This is a highly corrosive environment, and, as such, it is typical that a simple plain bearing is used at the ends of each of the rolls as other bearing types are not well suited for the highly corrosive environment of a zinc pot. The plain bearings used in the typical zinc pot are made from a variety of wear resistant materials, but nevertheless, the bearings used with these roll systems have a short operational life. Furthermore, plain bearings have extremely high rotational friction loads, and in order to prevent sheet slippage, designers have reduced journal diameter. As a result, these narrow journals frequently break off during service. Further still, plain bearings create chatter and vibration which leads to inconsistent coating quality and thickness.

SUMMARY OF THE INVENTION

The present invention relates to bearing systems for use with a roll assembly configured to be submerged in a corrosive environment, such as molten metal as part of a galvanizing line assembly.

With respect to the bearing assemblies in particular, one exemplary bearing assembly, or bearing system, of the present invention includes a housing that defines a cavity which accepts the journal of a roll. More specifically, the housing includes a forward wall that defines an opening into the cavity and the opening in the forward wall is configured to accept the journal through the opening. The housing further defines a rear end opening away from the forward wall. A cover plate is removably positioned over the rear end opening to selectively provide access to the cavity.

The exemplary bearing system further includes a sleeve positioned within the cavity of the housing and which is configured to surround the end of the journal. In some embodiments of the present invention, the sleeve is comprised of a material having a coefficient of thermal expansion which is less than the coefficient of thermal expansion of the journal. Accordingly, as the journal is heated, the journal will expand more than the sleeve, thus locking the sleeve onto the journal. When the journal cools and shrinks the sleeve will release from the journal. In this way, the exemplary sleeve is removably secured to the journal through a self-locking mechanism. Accordingly, the roll can be readily changed without requiring disassembly of the entire bearing system simply by removing the roll from the molten zinc and allowing the roll to cool until the sleeve releases from the journal. The journal can then slide out of the opening in the forward wall of the housing and the journal of a replacement roll can then be similarly installed.

The exemplary bearing system further includes a first seal positioned within the cavity of the housing adjacent to the forward wall of the housing so as to completely surround the opening in the forward wall of the housing. The first seal includes a rear engagement surface which, in some embodiments, is sloped towards the forward wall of the housing. A second seal is also positioned within the cavity of the housing and operably connected to the sleeve. In particular, the second seal defines a substantially cylindrical through hole with an internal surface which is positioned around and operably connected to the sleeve. The second seal is configured to be inserted through the first seal such that a substantially cylindrical exterior engagement surface of the second seal is in contact with the internal engagement surface of the first seal and a sloped forward engagement surface of the second is in contact with the sloped rear engagement surface of the first seal. Similar to the sloped rear engagement surface of the first seal, the forward engagement surface of the second seal is sloped towards the forward wall of the housing. In some exemplary bearing systems of the present invention, the second seal not only extends through the first seal but also through the opening in the forward wall of the housing to directly contact the roll around the journal.

In some embodiments of the present invention, a bearing is also positioned within the cavity of the housing to facilitate rotation of the roll and the sleeve.

In some exemplary bearing systems of the present invention, the cavity of the housing is pressurized by a gas line which is in fluid communication with the cavity. The gas line supplies gas into the cavity at sufficient pressure to push the second seal against the first seal to maintain the seal. Furthermore, in the event that a momentary thrust load from the roll temporarily breaks the contact of the seals, it is contemplated that the positive pressure within the cavity is sufficient to force gas out of the cavity with enough pressure to prevent the molten metal from entering the cavity.

Some exemplary bearing systems of the present invention further include a spring within the cavity of the housing positioned between the bearing and the cover plate. The spring bias the second seal forward such that the seals are in contact. Advantageously, the spring is capable of providing enough force to maintain the necessary contact between the seals even when the cavity is not pressurized.

In addition to accommodating rotation of the roll around its longitudinal axis, some exemplary bearing systems of the present invention further allow for rotation of the roll in a direction perpendicular to the longitudinal axis of the roll. In some embodiments, an arm is connected to an exterior housing which partially encloses the housing of the bearing system to form a ball joint which allows the housing to rotate relative to the exterior housing perpendicular to the longitudinal axis of the roll. In particular, the exterior housing has a curved inner surface and the housing includes a curved exterior surface configured to engage the curved inner surface of the exterior housing.

The bearing system of the present invention prevents molten metal from entering the cavity of the housing. The bearing system, and in particular the bearing itself, will therefore experience significantly less wear, extending the operational life of the bearing system of the present invention. As such, it is contemplated that, in some embodiments, the roll used in conjunction with the bearing system of the present invention includes a coating along the exterior surface of the main body which further increases the operational life of the roll by improving at least one of wear resistance, hardness, thermal stability, resistance to corrosion by acids, and/or reduced coefficient of friction. Of course, other coatings or treatments are also contemplated to extend the operational life of the bearing system and/or roll in order to reduce the frequency of equipment changes which reduces the time in which the galvanizing line assembly is not operational.

In some embodiments of the present invention, the bearing system described above is used for each of two bearing assemblies connected to either side of a roll as part of a roll assembly. The roll assembly of the present invention is configured to be submerged in a corrosive environment, such as molten metal. As such, the roll assembly can be used, for example, in a metal coating line assembly, such as a galvanizing line assembly. It is contemplated that the present invention is also suitable for other metal coating system including, but not limited to, assemblies for the production of galvannealed steel, galvalum, and aluminized metals. Likewise, any application in which a bearing system is subjected to a corrosive environment would benefit from the bearing system of the present invention.

DESCRIPTION OF THE INVENTION

The present invention is a bearing system for use with a roll assembly configured to be submerged in a corrosive environment, such as molten metal as part of a galvanizing line assembly.

Referring first toFIG. 1, similar to previous galvanizing lines, in one exemplary embodiment of the present invention, a roll assembly104includes a roll20that is supported on either end by arm109a,109b. The roll20is typical in the art in that it includes a substantially cylindrical main body22with two journals (one journal26shown inFIGS. 2-3) extending from either end of the main body22along the longitudinal axis of the main body22. However, unlike in previously known galvanizing lines, instead of utilizing plain bearings, the roll assembly104includes bearing assemblies10a,10bwhich are configured to accept the journal26of the roll20. Additional features of the roll20, the arms109a,109b, and roll assembly104in general will be described in further detailed below.

With respect to the bearing assemblies10a,10bin particular, and turning now toFIGS. 2-3, one exemplary bearing assembly10, or bearing system10, of the present invention representative of the bearing assemblies10a,10bshown inFIG. 1includes a housing40that defines a cavity46which accepts the journal26of the roll20. More specifically, the housing40includes a forward wall42that defines an opening44into the cavity46and the opening44in the forward wall42is configured to accept the journal26through the opening44. The housing40further defines a rear end opening49away from the forward wall42. A cover plate50is removably positioned over the rear end opening49to selectively provide access to the cavity46while also preventing molten metal from entering the cavity46through the rear end opening49when the housing40is submerged. As perhaps best shown inFIG. 3, an internal surface47of the housing40extends between the forward wall42and the rear end opening49with the internal surface47being substantially cylindrical. An interior surface43of the forward wall42of the housing40is angled relative to the internal surface47of the housing40such that the forward wall42narrows in the direction of the opening44, as further discussed below.

The exemplary bearing system10further includes a sleeve30positioned within the cavity46of the housing40and which is configured to surround the end of the journal26. As discussed in further detail below, the sleeve30has a forward exterior surface32, an intermediate exterior surface34, and a rear exterior surface36with each increasing in diameter.

In some embodiments of the present invention, the sleeve30is comprised of a material having a coefficient of thermal expansion which is less than the coefficient of thermal expansion of the journal26. Accordingly, as the journal26is heated, for example from submerging the roll20into molten metal, the journal26will expand more than the sleeve30, thus locking the sleeve30onto the journal26. When the journal26cools and shrinks, the sleeve30will release from the journal26. In this way, the exemplary sleeve30is removably secured to the journal26through a self-locking mechanism. Accordingly, the roll20can be readily changed without requiring disassembly of the entire bearing system10simply by removing the roll20from the molten metal and allowing the roll20to cool until the sleeve30releases from the journal26. The journal26can then slide out of the opening44in the forward wall42of the housing40and the journal of a replacement roll can then be similarly installed.

Of course, it is contemplated that in other embodiments, the sleeve30can be removably secured to the journal26by other means without departing from the spirit and scope of the present invention. For example, one or more screws (not shown) can be inserted through the end of the sleeve30and into the end of the journal26by way of the rear end opening49of the housing40. In such an embodiment, the roll20can still be readily changed without requiring disassembly of the entire bearing system10by removing the cover plate50and mechanically releasing the sleeve30from the journal26. Referring still toFIGS. 2-3, the exemplary bearing system10further includes a first seal60positioned within the cavity46of the housing40adjacent to the forward wall42of the housing40so as to completely surround the opening44in the forward wall42of the housing40. In particular, the first seal60defines a substantially cylindrical through hole with an internal engagement surface64which is substantially the same size as the opening44in the forward wall42of the housing40. According to some exemplary embodiments of the present invention, the first seal60is press fit in place within the cavity46. As such, the first seal60has a sloped forward surface66which is positioned immediately next to the interior surface43of the forward wall42. The first seal60also includes a rear engagement surface62which is sloped towards the forward wall42of the housing40, as described further below. It is contemplated, however, that in some other embodiments the first seal60can be removably secured to forward wall42of the housing40by other means without departing from the spirit and scope of the present invention. For example, a first seal formed in substantially the same shape as the first seal60shown inFIGS. 2-3can be inserted into the housing40by way of the rear end opening49of the housing40and then one or more screws can be used to secure the first seal60to the forward wall42of the housing40by way of the rear end opening49of the housing40. Likewise, it is contemplated that an anti-rotation pin or screw (not shown) can further be included so as to extend through the first seal60and into the forward wall42of the housing40to ensure that the first seal60does not rotate relative to the forward wall42of the housing40.

Referring still toFIGS. 2-3, a second seal70is also positioned within the cavity46of the housing40, but the second seal70is operably connected to the sleeve30. In particular, as shown inFIG. 3, the second seal70defines a substantially cylindrical through hole with an internal surface76which is positioned around and operably connected to the forward exterior surface32of the sleeve30, as discussed further below.

The second seal70is configured to be inserted through the first seal60such that a substantially cylindrical exterior engagement surface74of the second seal70is in contact with the internal engagement surface64of the first seal60forming a substantially tight fit between the exterior engagement surface74of the second seal70and the internal engagement surface64of the first seal60, the features and advantages of which are discussed further below. Furthermore, a sloped forward engagement surface72of the second seal70is in contact with the sloped rear engagement surface62of the first seal60. Similar to the sloped rear engagement surface62of the first seal60, the forward engagement surface72of the second seal70is sloped towards the forward wall42of the housing40.

Referring now specifically toFIG. 2, in the exemplary bearing system10, the second seal70not only extends through the first seal60but also through the opening44in the forward wall42of the housing40to directly contact the roll20around the journal26. As such, the second seal70provides a seal around the journal26of the roll and thus prevents molten metal from entering between the journal26and the sleeve30.

Referring once again toFIGS. 2-3, to facilitate rotation of the roll20and the sleeve30, the bearing system10further includes a bearing80positioned within the cavity46of the housing40. Specifically, the exemplary bearing80includes an inner race82positioned around and operably connected to the intermediate exterior surface34of the sleeve30, an outer race84positioned adjacent to the interior surface47of the housing40, and a plurality of balls86positioned between the inner race82and the outer race84. As such, the bearing80shown in this exemplary embodiment is a typical rolling bearing. It is contemplated that the bearing80included in the exemplary bearing system10of the present invention reduces strip vibrations during coating which decreases the amount of zinc applied to the steel sheet and increases the quality and value of the coated steel. In some exemplary embodiments, the bearing80, or at least some component parts, is comprised of heat resistant steel, hybrid steel and ceramic, or full ceramic. Of course, it is contemplated that other bearings known in the art can be used as part of the bearing system10of the present invention without departing from the spirit and scope of the present invention.

Referring once again toFIG. 3, as previously mentioned, the first seal60and the second seal70are configured to maintain a seal between the two engagement surfaces62,72. As such, when the bearing system10is submerged in the bath of molten metal, the molten metal cannot enter the cavity46of the housing40. To this end, the exemplary bearing system10of the present invention includes multiple features to ensure proper contact is maintained between the two engagement surfaces62,72of the seals60,70.

Referring now toFIGS. 1-4, in the exemplary bearing system10of the present invention, the cavity46of the housing40is pressurized by a gas line107which is in fluid communication with the cavity46. In particular, the gas line107is connected to the housing40by a fitting108which extends through an opening52defined in the cover plate50at the rear of the housing40. The configuration of the gas line107and fitting108is not particularly limited, but it is contemplated that, in at least some embodiments, the connection of the gas line107and fitting108to the housing40prevents unwanted rotation of the housing40. Regardless, as perhaps best shown inFIG. 4in particular, the exemplary gas line107runs substantially parallel, but independent of, the arm109, as discussed further below.

The gas line107supplies gas into the cavity46at sufficient pressure to push the second seal70against the first seal60and provide the necessary contact between the engagement surfaces62,72of the seals60,70to maintain the seal between the two engagement surfaces62,72. Furthermore, in the event that a momentary thrust load from the roll20temporarily breaks the contact of the seals60,70, it is contemplated that the positive pressure within the cavity46is sufficient to force gas out of the cavity46with enough pressure to prevent the molten metal from entering the cavity46. For example, in some embodiments, the pressure within the cavity46is maintained in a range of about 25 psi to about 50 psi. However, it is contemplated that the bearing system10of the present invention is operable with pressures as low as about 5 psi maintained within the cavity46and with pressures as high as about 300 psi maintained within the cavity46. Of course, the particular pressure within the cavity will vary depending on the intended application of the bearing system of the present invention. Regardless of the particular pressure supplied by the gas line107, it is preferable that an inert gas, for example nitrogen, is used with the bearing system10of the present invention.

Referring once again toFIGS. 2-3in particular, the exemplary bearing system10further includes a spring90within the cavity46of the housing40positioned between the bearing80and the cover plate50. The spring90bias the second seal80forward such that the engagement surfaces62,72of the seals60,70are in contact. Advantageously, the spring90is capable of providing enough force to maintain the necessary contact between the engagement surfaces62,72of the seals60,70to maintain the seal between the two engagement surfaces62,72, even when the cavity46is not pressurized. In the exemplary embodiment shown inFIGS. 2-3, the spring90is formed from a plurality of Belleville washers which surround a rear exterior surface36of the sleeve30, but other springs can be used without departing from the spirit and scope of the present invention. Preferably, the spring90is configured to only contact the outer race84of the bearing80such that the sleeve30and inner race82of the bearing80can freely rotate. Having now described each of the primary components of the bearing system10of the present invention, and referring still toFIGS. 2-3, in operation, once the roll20and bearing system10are heated such that the sleeve30is secured to the journal26of the roll20, as the roll20rotates around its longitudinal axis, the sleeve30will rotate along with the roll20. Due to the connection of the internal surface76of the second seal70to the forward exterior surface32of the sleeve30, the second seal70will also rotate along with the roll20. Likewise, due to the connection of the inner race82of the bearing80to the intermediate exterior surface34of the sleeve30, the inner race82of the bearing80will also rotate along with the roll20. In contrast, the first seal60and outer race84of the bearing80will remain stationary within the housing40. As such, the first seal60and the second seal70will rub against one another as the roll20rotates. The bearing system10therefore includes several features which allow the journal26of the roll20, and the attached sleeve30, to rotate relative to the housing40around the axis of the roll20while maintaining a seal.

As previously discussed, the exterior engagement surface74of the second seal70is in contact with the internal engagement surface64of the first seal60forming a substantially tight fit between the exterior engagement surface74of the second seal70and the internal engagement surface64of the first seal60. In some embodiments of the present invention, the first seal60and the second seal70are comprised of non-wetting materials, such that the substantially tight fit between the exterior engagement surface74of the second seal70and the internal engagement surface64of the first seal60naturally rejects molten metal by the meniscus effect of liquids on non-wetting surfaces. Furthermore, providing such a small clearance will increase the velocity of gas escaping in the event that momentary thrust load from the roll20temporarily breaks the contact of the seals60,70. This high velocity gas will more readily prevent the molten metal from entering the cavity46and maintain air pressure in the cavity.

As previously discussed, the rear engagement surface62of the first seal60and the forward engagement surface72of the second seal70are similarly sloped towards the forward wall42of the housing40. As the first and second seals60,70wear down, these corresponding sloped surfaces provide for automatic adjustment of the seals60,70to maintain the seal between the two engagement surfaces62,72of the seals60,70. The particular slope of the rear engagement surface62of the first seal60and the forward engagement surface72of the second seal70is not limited and, in some embodiments, there can be no slope at all. In embodiment where the engagement surfaces62,72are flat, e.g., perpendicular to the longitudinal axis of the roll20, radial loading is maintained entirely on the bearing80. By comparison, when the engagement surfaces62,72are sloped, radial loading is shared between the bearing80and the seals70,80. The particular angle of the slope will affect how the radial load is balanced between the bearing80and the seals60,70, and therefore will vary depending on the intended application of the bearing system of the present invention. It is contemplated, however, that the lowest preferred angle is about 7°.

Regardless of the automatic adjustment of the seals60,70, the exemplary seals60,70are preferably comprised of a resilient material, such as a ceramic, carbide, or other similar carbonic material, which is preferably resistant to mechanical, chemical, and/or thermal deterioration. For example, in some exemplary embodiments, the first seal60, the second seal70, or the first seal60and the second seal70are comprised of a ceramic including, but not limited, to one or more of the follow: carbon, carbon-carbon, tungsten carbide, M50 steel, zirconia, silicon nitride, silicon carbide, 440C stainless steel, 52100 steel, stellite, sialon, cobalt alloys and the like.

As previously mentioned, the internal surface47of the forward wall42of the housing40is sloped and the forward surface66of the first seal60is similarly sloped. It is contemplated that in the event of that any one of the housing40, the first seal60, or the second seal70have varying coefficients of thermal expansion, upon heating the bearing system10, the resulting differential expansion is automatically adjusted for by each of these pairs of corresponding sloped surfaces (e.g., the rear engagement surface62of the first seal60and the forward engagement surface72of the second seal70; and the internal surface47of the forward wall42of the housing40and the forward surface66of the first seal60). Once again, this advantageously maintains the seal between the two engagement surfaces62,72of the seals60,70.

In addition to accommodating rotation of the roll20around its longitudinal axis, the bearing system10of the present invention further allows for rotation of the roll20in a direction perpendicular to the longitudinal axis of the roll20. Referring now toFIGS. 2-4, the arm109is connected to an exterior housing54which partially encloses the housing40of the bearing system10to form a ball joint which allows the housing40to rotate relative to the exterior housing54perpendicular to the longitudinal axis of the roll20. In particular, the exterior housing54has a curved inner surface56and the housing40includes a curved exterior surface48configured to engage the curved inner surface56of the exterior housing54. As previously mentioned, the gas line107is not connected to the arm109. As such, the gas line107and the arm109can move, at least somewhat, independent of each other. Accordingly, the gas line107and the arm109can accommodate rotation of the housing40within the exterior housing54as well as lateral motion of the housing40relative to the exterior housing54along the longitudinal axis of the roll20.

As discussed above, the bearing system10of the present invention prevents molten metal from entering the cavity46of the housing40. The bearing system10, and in particular the bearing80itself, will therefore experience significantly less wear, extending the operational life of the bearing system10of the present invention. As such, it is contemplated that, in some embodiments, the roll20used in conjunction with the bearing system10of the present invention includes a coating along the exterior surface of the main body22which further increases the operational life of the roll. For example, in some exemplary embodiments, a steel roll is subject to boriding, or boronizing, in order to improve at least one of the wear resistance, hardness, thermal stability, resistance to corrosion by acids, and/or reduced coefficient of friction. Of course, other coatings or treatments are also contemplated to extend the operational life of the bearing system and/or roll in order to reduce the frequency of equipment changes which reduces the time in which the galvanizing line assembly is not operational. For example, in some exemplary embodiments, the roll is provided with a coating including, but not limited, to one or more of the follow: tungsten carbide, chrome carbide, WC—WB—Co, Alumina Zircona, TAMoB25NC3, and the like.

Referring once again toFIG. 1in particular, in some embodiments of the present invention, the bearing system10described above with respect toFIGS. 2-4, is used for each of two bearing assemblies10a,10bconnected to either side of a roll20as part of a roll assembly104. The roll assembly104of the present invention is configured to be submerged in a corrosive environment, such as molten metal. As such, the roll assembly104can be used, for example, in a metal coating line assembly, such as a galvanizing line assembly.

Although the above embodiments are described with respect to a galvanizing line assembly, it is contemplated that the present invention is also suitable for other metal coating system including, but not limited to, assemblies for the production of galvannealed steel, galvalum, and aluminized metals. Likewise, any application in which a bearing system is subjected to a corrosive environment would benefit from the bearing system of the present invention.

One of ordinary skill in the art will recognize that additional embodiments are possible without departing from the teachings of the present invention. This detailed description, and particularly the specific details of the exemplary embodiment disclosed therein, is given primarily for clarity of understanding, and no unnecessary limitations are to be understood therefrom, for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit or scope of the invention.