Abstract:
A linear bearing plate, or liner, for use within a rolling mill stand, said liner including lubrication ports in fluid communication with a lubrication source. A centralized lubrication source can provide a predetermined lubrication to a plurality of mill stands in response to a signal, such as from a rolling facility operator. Lubrication ports provide areas of active lubrication which are surrounded by areas of passive lubrication so as to provide adequate lubrication during a rolling campaign.

Description:
RELATED APPLICATIONS 
     This application claims benefit of priority of U.S. Ser. No. 60/984,366, filed Oct. 31, 2007, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Linear bearings or liners have been used to provide a flat guiding module or plate-type bearing elements for rolling stand frames. These bearings typically have at least one slide-bearing surface in contact with another bearing surface and are particularly prone to wear and tear within the hostile rolling environment. Versions of linear bearings are disclosed in PCT applications, PCT/EP02/03010 and PCT/EP03/014573, each document being incorporated by reference herein. 
     To obtain precisely rolled products, all clearances throughout the rolling system must be evaluated and held to the tightest possible tolerances. Failure to maintain bearing clearances often results in a substantial economic reduction of the product, increased maintenance costs, excessive component wear, and other dangerous conditions. 
     It has been recognized that bearing wear is often determined by outside influences and mechanical effects such as abrasion, chamfer wear and wear of mounting surfaces. Abrasion may result from scale and abrasive particles, severely worn bearing surfaces from any relative movement between chock and housing, corrosion and localized overloads. Chamfer wear may result in damaged chamfers, reduced bearing surface area, imprecise guidance during chock loading, and open passages for water and abrasive particles. Corrosion (or erosion) may be caused by cooling water chemicals, high pressure descaling water and shimming. Corrosion may result in washed out lubrication, increased humidity, fretting defects and pop-outs of liner material. Wear of liners may also result from heavy impact loads, such as hammering, localized overloads and corrosion/erosion. 
     SUMMARY OF THE INVENTION 
     Addressing the deficiencies of the conventional art, embodiments in accordance with the present invention resolve many linear bearing problems in an efficient, cost effective manner. The present invention relates to a mill stand with a liner plate having a plurality of lubricant conduits and apertures and an apparatus for delivering lubricant to the plates. The system may include a centralized lubricant source or a plurality of discrete lubricant sources. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification and wherein like numerals and letters refer to like parts wherever they occur. 
         FIG. 1  is a perspective illustration of a mill stand and related components. 
         FIG. 2  is a depiction of a mill stand in a non-worn condition. 
         FIG. 3  is a depiction of the mill stand of  FIG. 2  in a worn condition. 
         FIG. 4  illustrates a typical wear pattern of a liner plate. 
         FIG. 5  illustrates poor quality yield of a worn mill stand. 
         FIG. 6  is a plane view of a liner plate adaptable for use with the mill stand of  FIG. 1 . 
         FIG. 7  is a graph showing a relationship between grease pressure and a distance from a grease outlet port on a liner plate. 
         FIG. 8  illustrates areas of active and passive lubrication on a liner plate. 
         FIG. 9  illustrates a system for supplying lubricant to a liner plate. 
         FIG. 10  illustrates a rolling facility having a plurality of mill stands and a centralized lubrication system. 
         FIG. 11  is a plan view of one side of a liner plate in accordance with the present invention. 
         FIG. 12  is a plan view of the other side of the liner plate of  FIG. 11 . 
         FIG. 13  is a cross-sectional view taken along lings A-A of  FIG. 11 . 
         FIG. 14  is a perspective view of the liner plate of  FIG. 1 . 
         FIG. 15  is a plan view of one side of another embodiment of a liner plate in accordance with the present invention. 
         FIG. 16  is a plan view of the other side of the liner plate of  FIG. 15 . 
         FIG. 17  is a perspective view of the liner plate of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  provides a perspective view of a mill stand  10  incorporating linear bearings (or “liners”)  12 , with the pair of working rolls  14  and chock set  15  depicted in a removed state relative to the mill stand (or “roll stand) housing  16 . During use, the linear bearings  12  engage linear bearings  18  attached to the roll stand housing  16  to limit movement of the rolls  14  to a generally horizontal direction. The bearings  18  include lubricant ports supplied via a lubrication delivery system as described in additional detail herein. Embodiments of linear bearings  16 ,  18  are disclosed in PCT applications, PCT/EP02/03010 and PCT/EP03/014573, each document being incorporated by reference herein. Additional linear bearings adaptable for use within a system in accordance with the present invention may be provided by Josua CORTS Sohn, Bearing Technology Division, of Remscheid DE. 
       FIG. 2   a  provides a side elevational view depiction of a mill stand incorporating linear bearings. The mill stand of  FIG. 2   a  depicts components in relatively new, unworn condition. The mill roll is held between mill stand sides by chocks  14  and liner pairs  16 . The chocks and chock liners move vertically during operation with the chock liners being in sliding contact with the housing liners. As depicted, slab product  17  moves through roll stand  16 . In such a condition, the impact of the rolling mill energy is dispersed across a substantial portion of the chock liner surfaces. 
       FIG. 2   b  is a top elevational view depiction of the mill stand of  FIG. 2   a.  The direction of slab movement is illustrated by the arrows.  FIG. 2   b  illustrates a mill stand in optimum condition, where the impact of the slab into the mill stand is dispersed throughout the liner surfaces. 
     A mill stand incorporating worn linear bearings is shown in  FIG. 3   a . The mill stand of  FIG. 3   a  depicts the bearing components in a worn condition. In such a condition, the impact of the slab into mill stand is dispersed across a relatively small portion of the chock liner surfaces creating “point loads.” Point loads can undesirably lead to localized mechanical failure.  FIG. 3   b  is a top view depiction of the mill stand of  FIG. 3   a  showing a non-parallel slab defect caused by worn liners. 
       FIG. 4  is a depiction of edge wear on a bronze liner plate. During use of the liners, significant edge wear can also be caused by contact during the roll exchange procedure. 
       FIG. 5  depicts results of non-rectangular rolling due to worm. Profile errors are found in the products as manifested by waves, crowns, chatter marks and other defects. Product manufactured with such flaws yields a significantly lower price per ton. Similarly, the economic consequences of non-rectangular rolling due to increased liner clearances are significant. Profile and other defects yield lower quality products, increased scrap and shutdowns, increased maintenance costs, all yielding a substantial reduction in product price. 
     A liner  18  incorporating aspects of a lubrication system of the present invention is shown in  FIG. 6 . Pressurized lubricant exits ports  60  within the grooves  62  during operation and is conveyed across portions of the liner surface. A substantial reduction in the coefficient of friction can be obtained using such a lubrication system. As shown in  FIG. 7 , grease pressure decreases outside of the grease feeding area as the distance from the grease feed aperture increases.  FIG. 8  illustrates areas of active lubrication and passive lubrication for a liner  18  used in accordance with the present invention. 
     An embodiment of lubrication system components for delivery of lubrication to a liner  18  is shown in  FIG. 9 . A pump  100  directs pressurized lubricant through filter  101  via conduit  104  and through fluid control valves  102  for delivery to liner inlet ports  103 . Pressurized lubricant is directed through liner  18  via a plurality of conduits  108 . The conduits  108  may be defined by a plurality of channels, machined or otherwise formed in the back or front surface of the liner  18 . Once installed on the housing  16 , the channels cooperate with a surface of housing  16  (or chock set) to define a plurality of closed conduits for feeding lubricant to the plurality of ports  60 . Inlet port  103  is shown on the side of the liner  18 , though in alternative embodiments an inlet port may exist on other surfaces of the liner. 
     Additional aspects of a centralized lubrication system in accordance with the present invention are shown in  FIG. 10 . A central lubrication system provides a lubricating film between the surfaces of liners  18  of a plurality of roll stands  16 , achieving a reduction of the temperature inside the liner, and limiting entry of cooling water or other contaminants into the bearing. 
     During operation, a centralized pump  100  and flow controls  102  may be controlled via a controller to distribute lubrication to various liners  18  within a facility. While the embodiment of  FIG. 10  shows a single lubricant source, alternative systems may utilize multiple different lubricants and provide different lubricants to different liners within the facility or at different times during a rolling campaign. In another example, a plurality of lubricant point sources may be positioned in the immediate vicinity of given mill stands. For example, a 55 gallon drum of a lubricant may be associated with one mill stand to supply a predetermined lubricant to the liner surfaces. A pump  100  feeds the lubricant directly, or via a distribution block to the liners  18 . An oil film is thus formed from the fed lubricant. Benefits of a centralized lubricant system include a reduction in lubricant consumption, prolonged anti-friction bearing life, a reduction in disposal and maintenance costs, and precise metering of lubricant. 
       FIGS. 11-14  show a liner plate  18  used in accordance with the present invention. The liner plate  18  includes a plurality of apertures  120  for securing the liner  18  to a housing  16  and a plurality of apertures  106  for emitting lubricant. The lubricant apertures  106  are connected to an internal conduit  108  to an inlet port, here shown located at the side of the liner  18 . 
     The lubrication-carrying conduits  108  may be associated with a single lubricant port  60  or may be associated with more than one lubricant port  60 . The lubricant ports include a cup-shaped generally cylindrical depression  110  suitable to contain a volume of lubricant during use. One benefit of the distributed lubricant ports  60  is an equalization of pressure across the liner  18  surface during operation. By maintaining equalized pressure, uneven wear of the liner  18  surface can be minimized. 
     The internal conduits may be formed by a machining operation whereby a channel is cut into the surface of the liner plate. In operation, the channel and a portion of the an adjacent liner together define a generally closed conduit capable of controlling the flow of lubricant toward the lubricant outlet ports. 
     As described above, lubricant is introduced into the liner  18  via inlet ports. These ports may be fed by a pressurized distribution system as described above. The same lubricant may be introduced into the inlet ports or different lubricants can be introduced in different inlet ports. 
     The liner plate of  FIGS. 11-14  also show a sensor wire conduit  132  extending across a portion of the liner  18  surface. A sensor wire (not shown) is received within the conduit  132  and is connected at one end to a sensor and to a connector at another end. The sensor may be a gap sensor  133  for determining a displacement between the liner plate and another surface. 
       FIGS. 15-17  show another embodiment of a liner plate  18  adaptable for use within a system in accordance with the present invention. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.