Abstract:
A linear bearing assembly including a linear bearing plate, a base plate to support the linear bearing plate within a machine, a sealing structure to seal a volume defined between the linear bearing plate and the base plate, and a fluid adapted to be injected into the volume via at least one injection port. The fluid is injected at a sufficient pressure so as to alter an orientation of the linear bearing plate or the base plate toward an initial geometric orientation.

Description:
TECHNICAL FIELD 
     The present disclosure is directed to linear bearing technology. More particularly, the disclosure relates to a variety of steel and compound steel linear bearings including, but not limited to, rolling mill stands and other heavy equipment. A variety of flat and ring bearings may be manufactured or modified utilizing the present invention. 
     BACKGROUND OF THE INVENTION 
     The invention relates to linear bearings, such as used in heavy equipment, which provide linear load support and guidance particularly in applications where the area loads are too high to utilize the support and guidance through other kinds of rotational bearing elements, for example, due to the fact that the high area loads and resulting Hertzian stresses created in the contact zone would result in plastic deformation. 
     Linear bearing are used to support the lateral movement requested by the various processes and equipment such as bearing plates in mill windows of steel rolling mills. The bearing surfaces of those bearing plates are normally exposed to three major wear factors which include area loads, abrasion and corrosion. Wear, abrasion and corrosion typically lead to changes in the bearing plate geometry. 
     Abrasion and corrosion effectively increase the gap or play between two matching bearing surfaces and this increased play undesirably allows for relative movement of the equipment components. Due to the high dynamic energy of the moving components, the dynamic loads are proportional to the bearing play or gap. When dynamic loads reach a specific level, bearing plates transfer dynamic loads to bearing mounting and reference surfaces. The gap quickly grows and the output quality of the mill stand quickly degrades. 
     A direct relation between the hardness and stiffness of the material used for the bearing plates exists, because the hardness of any material is directly proportional to the stiffness and inflexibility of the material. A harder bearing plate material will deform a softer counterpart and as soon as the hardness of the bearing plate exceeds the hardness of the related mounting surface, the bearing plate will apply dynamic loads to its mounting counterpart with the potential to elastically and plastically deform the mounting surface. With this resulting deformation the connection between the bearing plate and the mounting surface will gradually yield gaps. These gaps permit, through a capillary effect, humidity and wetness to seep between the matching surfaces of the bearing. 
     Humidity and wetness between the matching surfaces, e.g., between the bearing plate and the mounting surface, will initiate another wearing factor called contact corrosion. Both mounting surfaces start transforming iron into iron oxide which then is washed out by more humidity pumped in by the relative movement under the constant dynamic loads created by the process. The result is a constantly increasing play or gap not only between the matching bearing surfaces of the equipment components involved but also between the bearing plates and their related mounting surfaces. 
     With sufficient moisture, a liquid layer is formed between the bearing plates and their related mounting surfaces. When high dynamic loads are applied to this liquid layer, cavitation occurs and leads to another wear mechanism. Cavitation increases the washout of the mounting surfaces which in turn gradually changes the geometry of those mounting surfaces. Due to the fact that mounting surfaces are at the same time the reference surfaces for the installation of the linear bearing plates, the equipment is gradually altered from its desired geometrical set-up. 
     Changes of the basic equipment geometry, for example a window of a rolling mill, will have a direct influence on the basic function of the equipment. In case of a rolling mill the changes of the mill window geometry change the geometrical relation of the rolls to each other which then in return has a direct influence on the rolling process as well as the geometry of the rolled products. 
     When any combination of the given process related limits are exceeded, the mill window geometry and reference base for the bearing plates has to be corrected. For such corrections there have been two basic processes. Prior to the present invention the play, gap or volume created be the erosion and wear and tear have been compensated by filling the gap with shims or injecting an appropriate resin material. Next, the surfaces are re-machined to new accuracy and the increased opening of the mill window compensated with the increasing of the bearing plate thickness. The selection of the correction method is driven by cost and time because the complete rolling mill has to be fully stopped to be able to apply the desired compensation technology. The quickest and cheapest approach has often been shimming or filling with resin and finally re-machining. 
     The prior art approach of applying the resin included steps of first mechanically adjusting the bearing plate geometry by using a combination of thrust and tension screws to provide a specific spacing between the bearing and mounting surface. Next, a seal was provided to surround the bearing plate and finally resin was injected between the bearing plate and the adjacent mounting surface.  FIG. 10  illustrates such a process wherein a resin material  200  is injected between the housing liner  202  and the housing body  204 . The resin material is injected under pressure and is maintained by a seal structure  206  surrounding the housing liner  202 . The injected resin material  200  fills the interior volume defined between the housing liner  202  and the worn surface of the housing body  204 . The success and durability of this methodology is strongly dependant on the preparation and cleanliness of the surfaces which are in direct contact with the resin. Due to the extremely hostile environment of the equipment to be repaired, the constant presence of oil and grease and also the dimensions and mostly vertical orientation of the mounting surfaces, it is very difficult to insure cleanliness of the resin-engaging surfaces necessary for rehabilitation of the bearing system. Due to the fact the resin has to be injected it has to be based on a 2-component epoxy which also needs a specific environmental temperature to be correctly applied. Also desirable temperature conditions for resin-setting are difficult, if not impossible, to maintain under the normal conditions of the facility. 
     There exist several negative effects of the application of plastic filling material or resin on the mounting surfaces of the mill housing body. Due to the difficulty of cleaning the mounting surface of the housing body, the contact between the resin and the worn out mounting surface is often not adequately maintained. Subsequent dynamic loads on the bearing plate further open a gap or create contact zones between the resin and the mounting surface allowing chemicals and liquid to seep in and cause corrosion. The plastic filling material or resin may also form bubbles which promote de-lamination and corrosion. 
     Thus, a need exists for a safe, economically efficient and robust approach so as remove the limitations of the prior art approaches to bearing maintenance and operation, particularly for linear bearings operating in hostile environments. 
     SUMMARY OF THE INVENTION 
     The invention relates to linear bearings, such as used in heavy equipment, which provide linear guidance particularly in applications where the area loads are too high to utilize the guidance through other kinds of rotational bearing elements. 
     Embodiments of the present invention provide a novel approach and combination of the advantages in methods, manufacturing and application of the existing solutions. With this new solution the two major targets of time reduction and cost optimization for the re-machining of the equipment can be reached. This increased security of the overall repair procedure is an especially important aspect, because the on-site conditions for the repair work are mostly non-optimal. 
     Embodiments of the invention may utilize the exceptional abrasion and corrosion protection abilities of the bearing surfaces through the proven technology of compound steel bearings (see PCT Application No. PCT/IB2009/007920 (International Publication No. WO 2010/064145), which is incorporated by reference herein in its entirety) and the geometrical flexibility of mounting those bearing plates in a mill window, which lost its original reference and mounting surface by filling the gap between the worn out mounting surface and the backside of the bearing plate by an appropriate resin (see German Patent Nr. DE 102005004483A1-10.08.2006, which is incorporated by reference herein in its entirety). 
     Embodiments of the present invention integrate a resin or other fluid into a volume defined between the bearing plate and the base plate. The surface conditions within the volume are more easily controlled. The cleanliness of the surfaces as well as the temperature within the volume can be controlled to a far better degree. In one example, the integration of a base plate, the combination of thrust and tension screw, the surrounding sealing structure as well as the cleanliness of the injection volume offer the advantages of better preparation to the repair and re-machining work, more secure technical conditions for the injection as well as better and more secure protection of a corroded mounting surface against further corrosion after the repair. The application of the embodiments of the present invention are only limited by the maximum strength which can be used with resin. In areas where this strength of the resin is not high enough to withstand the area loads created by the process a re-machining of the mounting surfaces and the increasing of the bearing plate thickness may be unavoidable to secure the future process stability. 
     Embodiments of the present invention may also include the integration of a pressure sensor between the bearing and base plate to collect load data and injection pressures. The pressure sensor may be used to control machine parameters or even control a pressure applied to the fluid volume between the bearing plate and the base plate. The pressure sensor may be utilized to provide dynamic leveling of the bearing plate. 
     Embodiments of the present invention may also provide bearing optimization by selectively providing a pressurized fluid into a controlled volume defined between the bearing plate and the base plate and the sealing structure. The fluid pressure and/or flow rate may be controlled to adjust or maintain dimensions between the bearing components. In one embodiment, a dynamically controlled bearing assembly is provided by dynamically adjusting the pressures applied to one or multiple control volumes. In this manner, the fluid pressures can be controlled in response to measurements or other conditions signaling a deterioration or change of bearing dimensions. 
     Other purposes will appear in the ensuing specification, drawings and claims. 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 
         FIG. 1  is an illustration of a metal rolling stand upon which an embodiment of the present invention may be utilized; 
         FIG. 2  is another illustration of a metal rolling stand; 
         FIG. 3  illustrates a portion of the mill stand; 
         FIG. 4  illustrates a portion of the mill stand; 
         FIG. 5  is a cross-sectional view taken through a linear bearing assembly in accordance with the present invention; 
         FIG. 6  is a cross-sectional view of the bearing assembly of  FIG. 5  after a period of use; 
         FIG. 7  is a cross-sectional view taken through another embodiment of a linear bearing assembly in accordance with the present invention; 
         FIG. 8  is a cross-sectional view of the bearing assembly of  FIG. 7  after a period of use; 
         FIG. 9  is an illustration of yet another embodiment of the present invention; and 
         FIG. 10  is an illustration of a prior art approach to linear bearing rehabilitation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a typical “4-High” steel rolling mill stand  10  having a mill housing  12 , back-up chocks  14  and  16  and work-roll chocks  18  and  20  while the bearing plates are mounted on the chocks and housings body. Such a mill stand is further disclosed in U.S. Pat. No. 6,408,667, incorporated by reference herein. The chocks  14 ,  16 ,  18 ,  20  are supported upon the bearing plates. Flat bearings are critical components in maintaining optimal rolling conditions, protecting housings and chocks from damage and reducing downtime related to maintenance of key mill components. 
       FIG. 2  shows an example of a steel mill stand  30  having a housing  31  with a mill window  32 , chocks  34  and rolls  36 . Mill window bearing plates  40  and chock bearing plates  42  cooperate to support the chocks  34  and rolls  36 . In operation, bearing plates  40  and  42  engage each other to provide linear guidance to the chocks  34  and rolls  36 . In typical steel production facilities the bearing plates  40  and  42  operate in extremely hostile environments and are subject to high dynamic loads, abrasive elements, aggressive chemicals and high heat. While  FIG. 2  depicts a typical application of linear bearing plates in rolling mills, other embodiments of this invention are not limited to such an application. It should be appreciated that a variety of flat bearing systems may utilize the teaching of the present invention. 
     Additional descriptions of linear bearings particularly suitable with the present invention are disclosed in applicant&#39;s U.S. patent application Ser. No. 12/263,260, filed Oct. 31, 2008, entitled “Linear Bearing Plate for Rolling Mill,” having Publication No. US2009/0165521A1, and being incorporated by reference herein. 
       FIG. 3  depicts a plurality of mill window bearing plates  40  within housing  31 . The bearing plates  40  are secured to the housing  31  via a plurality of threaded fasteners  43 . Each of the bearing plates  40  is subject to a different load profile and environmental conditions. 
       FIG. 4  depicts a somewhat exaggerated wear-profile  44  on worn bearing plates  40  in the mill window of mill housing  31 . The wear profile  44  is non-linear with certain portions of the bearing plates  40  being significantly more worn than other portions. 
       FIG. 5  depicts a cross-sectional view of a bearing assembly in accordance with the present invention.  FIG. 5  illustrates one embodiment of the present invention where the bearing plate  50  and the base plate  52  define an inner volume  53 , surrounded by an appropriate sealing structure  54  to contain an injected resin or other fluid  56 . The base plate  52  is preferably be made from an appropriate, semi-elastic material to bear the loads of the rolling mill application. Base plate  52  may also be selected of a material suitable to engage the mounting surface  57  of the machine body  60  (e.g., mill housing  31 ). The base plate  52  is supported, for example in a vertical orientation, on the mounting surface  57 . The resin or other fluid  56  can be injected into volume  53  during, for example, a maintenance procedure or during normal operating conditions. 
     The resin or other fluid  56  may be injected via an injection port located on the base plate  52  or the bearing plate  50  or the sealing structure  54 . The injection port may be integrated into the design of the base plate or bearing plate with an external coupling being made to a pressurized fluid source. 
       FIG. 6  illustrates the bearing plate  50  and base plate  52  separated by variable thickness resin layer  56 . A variable height sealing structure  54  maintains the injected resin within the desired volume. In this illustration, the base plate  52  and mounting surface  57  of the machine body  60  are substantially worn. The surrounding seal structure  54  can be designed to accommodate the non-parallel relation between the bearing plate  50  and the base plate  42  caused by wear. A layer of corrosion protection  59  can be applied between the base plate  52  and the machine body  60 . 
     Referring now to  FIGS. 7 and 8 , another embodiment of the invention is shown with bearing plate  70  positioned relative to base plate  72 . The bearing plate  70  is fixed to the base plate  72  by a combination of a threaded thrust bushing  74  and a tension bolt  75 . The surrounding seal structure  54  is secured to the bearing plate  70  and/or base plate  72 . The surrounding seal structure  54  is shown partially positioned in channels of the base plate  72  and bearing plate  70 . 
     As the mounting surface  80  of the machine body  60  is worn out and becomes non-parallel to the bearing surfaces, the bearing plate  70  is adjusted by the combination of threaded thrust bushing  74  and tension bolt  75 . It is desirable that the base plate  72  be semi-elastic in order to compensate for the differing orientation of the bearing plate  70  and the mounting surface  80  of the machine body  60  to each other. After the bearing plate  72  is adjusted, resin  84  can be securely injected into the protected and sealed volume  81  between the bearing plate  70  and the base plate  72 . An anti-corrosion agent  59  is provided between the base plate  72  and the machine body  60  for the long term corrosion protection of the mounting surface  80 . 
     The volume  81  defined between the bearing plate  70  and the base plate  72  and bounded by the sealing structure  54  may be filled with resin or other fluid, for example during a maintenance procedure. The volume may comprise a single or multiple portions. For example, the sealing structure  54  may define a plurality of separate resin/fluid volumes. The plurality of volumes may be independently filled with resin or other fluid or may be interconnected and filled during a single resin or fluid injection. The resin or other fluid can be injected at various pressures and flow rates depending on the needs of the overall system. In the case of an injected fluid which is non-setting, the fluid may be withdrawn after a period of time or additional fluid may be injected at a later time. 
     In another embodiment of the present invention, a non-setting fluid is introduced into the volume  81  and the fluid remains pressurized during subsequent use of the system. The fluid pressure may be controlled, for example, by a remote controller to adjust the parameters of the bearing. For example, a non-setting fluid may be dynamically controlled to vary the dimensions between the bearing plate  70  and the base plate  72  by dynamically changing the pressure of the fluid introduced into one or more volumes  81 . 
     The sealing structure  54  may include O-rings or other flexible sealing devices. The sealing structure  54  may be adhered to either the bearing plate  70  or the base plate  72  or both. The sealing structure  54  may define a single wall or include multiple walls affording additional protection against blow-outs or other failures. The sealing structure  54  may be inserted into a channel or other relief to minimize movement of the sealing structure  54 . 
     Another embodiment of the present invention is provide in  FIG. 9 , wherein a pressure sensor  90  is mounted between the bearing plate  92  and base plate  94 . The pressure sensor  90  is calibrated before, during or after injection of the resin material  96 . The pressure sensor  90  is connected to the appropriate control panel  98  by the signal cable  99 . The application of a pressure sensor  90  provides data leading to an improved understanding of the maximum loads on the bearing plate  92 , such as for further analysis and benchmarking. 
     A variety of linear bearings may utilize aspects of the present invention. For example, during a repair procedure, resin may be injected one or more ports of a bearing plate with other ports acting as vent ports. In one embodiment, the resin is a polymer-concrete combination having crystalline particles of different sizes to optimize filling of the volume between the bearing plate and the base plate. The polymer may be between 5% to 10% of the total volume to yield a resin of relatively high strength and pressure resistance. 
     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.