Abstract:
The coating device ( 10 ) for coating a metal band or strip ( 12, 12′ ) in a melted metal mass ( 14  ) comprises a shaft ( 16, 18 ) rotatably supported in the melted metal mass ( 14 ) by a slide bearing ( 26   1   , 26   2 ) is formed by a bearing housing ( 32 ) and an open bearing shell ( 34 ) held therein, with two bearing surfaces ( 36 ) . Between the two bearing surfaces ( 36 ), the bearing shell ( 34 ) comprises a deformation zone ( 40 ) with a deformation element ( 44 ) . With high radial forces of the shaft occurring, the two bearing shell halves ( 38   1   , 38   2 ) are slightly spread. The flexible deformation zone ensures that the two bearing shell halves remain interconnected and resist breaking in this area.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a coating device for coating a metal band in a melted mass of a metal. 
   Coating devices are used for coating metal bands and sheets with zinc, aluminum, tin, lead, galvalum or galfan. In doing so, the metal band or sheet is drawn through a several hundred degrees Celsius hot melted metal mass of the coating metal: The metal band continuously dips downward into the melted metal mass, is deflected upward by a rotating shaft in the melted metal mass, steadied by a stabilizing shaft and travels upward out of the melted metal mass again. The bearing of the deflecting shaft and/or the stabilizing shaft in the melted mass is effected in open slide bearings that are designed as wearing bearings. Each of the slide bearings is formed by a bearing housing and a non-closed integral bearing shell held therein, with a single pair of bearing surfaces. With high radial loads of the deflecting and stabilizing shafts, respectively, the two bearing surfaces are spread by the shaft journal. In case of strong radial forces, bending forces may occur between the two rigidly interconnected bearing surfaces which are so high that the bearing shell breaks in this area. After the bearing shell has broken, it has to be exchanged. The exchange of the bearing shell takes up several hours, which represents a considerable damage with coating plants having a value of up to 200 million DM. 
   Therefore, it is the object of the invention to avoid a break of the bearing shell even with high radial loads. 
   SUMMARY OF THE INVENTION 
   In the coating device according to the invention, the bearing shell comprises a deformation zone with a deformation element between the two bearing surfaces. This means that the two neighboring bearing surfaces of the bearing shell are no longer rigidly and therefore break-susceptibly interconnected, but are connected to each other by a deformation element that is configured such that it permits distortions while maintaining the connection of the two bearing surfaces or bearing shell parts. Thereby, an undesired break of the bearing shell is avoided. The expensive exchange of broken bearing shells is eliminated. 
   Preferably, the deformation zone is formed by a continuous radial gap in the bearing shell, filled up by the deformation element that consists of a material different from that of the two bearing shell parts. The radial gap separates the bearing shell into two separate parts only connected with each other by the deformation element. The deformation element is configured in the form of a strip completely filling up the radial gap. 
   The deformation zone, however, can also be configured differently, for example as a rotational joint or in the form of a film hinge with a film-like thin connection bridge between the two bearing surfaces or bearing shell parts. 
   According to a preferred embodiment, the bearing shell is made of ceramics. Preferably, the deformation element is a graphite sheet arranged in the radial gap between the two bearing shell parts and interconnecting them. As tests have shown, the graphite sheet has a sufficient flexibility for movements between the two bearing shell parts occurring with high radial forces. At the same time, the graphite sheet is sufficiently resistant against the possibly very aggressive melted metal mass. 
   According to a preferred embodiment, the gap width is smaller than 2.0 mm, particularly between 0.3 mm and 1.0 mm. As tests have shown, a graphite sheet with a thickness of 0.5–0.8 mm in particular is well suitable as deformation element in a radial gap of the same width. 
   According to a preferred embodiment, the shaft is a stabilizing shaft for stabilizing the metal band against fluttering. 

   
     BRIEF DESCRIPTION OF THE DRAWING  
     The invention may take from in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the invention. 
     Hereinafter, an embodiment of the invention is explained in detail with reference to the drawings. 
     In the Figures: 
       FIG. 1  shows a coating device according to the invention, with a deflecting shaft and a stabilizing shaft in a melted metal mass in side view, 
       FIG. 2  shows the coating device of  FIG. 1  in front view, 
       FIG. 3  shows a longitudinal section of a slide bearing of the coating device of  FIG. 1 , and 
       FIG. 4  shows a cross-section of a slide bearing of the coating device of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , a coating device  10  is illustrated in side view in a simplified manner, with the deflecting shaft in partial cross-section. A metal band  12  is led through a melted metal mass  14  to provide the surface of the metal band  12  with a thin metal coating. The melted metal mass may consist of liquid zinc, lead, tin, aluminum, galvalum, galfan or other metals suitable for the coating of metal. Depending on the type of the melted metal, the melted metal mass  14  has a temperature of 400–1000° C. 
   The metal band  12  is introduced into the melted metal mass  14  at an angle of 30–45° to the horizontal and deflected upward in the melted mass  14  by means of a rotatable deflecting shaft  16  so that the metal band  12 ′ is led vertically upward out of the melted metal mass  14  again. The angle of contact of the metal band  12 , 12 ′ about the deflecting shaft  16  amounts to about 130°. The tensile force of the metal band  12  amounts to between 1.0–8.5 tons. 
   For stabilizing the metal band  12 , 12 ′, a stabilizing shaft  18  abuts on the metal band  12 ′ moving vertically out of the melted metal mass  14  in order to dampen and to reduce the horizontal fluttering of the metal band  12 ′. The stabilizing shaft  18  is suspended at a movable guide arm  20  that is pivotally supported and biased toward the metal band  12 ′ in horizontal direction. Further, the guide arm  20  of the stabilizing shaft is dampened in its horizontal movement by a corresponding dampening element. Both the deflecting shaft  16  and the stabilizing shaft  18  are permanently dipped into the melted metal mass  14  during operation. 
   At both sides of the vertically extending metal band  12 ′ emerging from the melted metal mass  14 , gas nozzles  22 , 24  are arranged through which a gas flow is applied on both sides of the metal band  12 ′. Due to the gas flow, the liquid metal layer on the metal band  12 ′ is reduced to a definite constant layer thickness. 
   By two pivot arms  17   1 ,  17   2 , the deflecting shaft  16  is held in the melted metal mass  14 . The deflecting shaft  16  is adapted to be lifted out of the melted metal mass  14  for the purposes of maintenance and repair. For this purpose, the guide arm  20  with the stabilizing shaft  18  is also adapted to be lifted out of the melted metal mass  14 . The arms  17   1 ,  17   2 ,  20  are lifted out of the melted metal mass  14  by means of a non-illustrated change-over tie-bar to which they are mounted. 
   As can be seen in  FIGS. 1–4 , slide bearings  26   1 ,  26   2  are provided at each of the two dipped ends of the pivot arms  17   1 ,  17   2 , in which the deflecting shaft  16  is rotatably supported. The two slide bearings  26   1 ,  26   2  are wearing bearings substantially formed by a bearing housing  32  and a non-closed bearing shell  34  axially inserted therein. Each bearing shell  34  forms two bearing surfaces  36  that are inclined to each other at an angle of about 130°. In longitudinal section, the bearing surfaces  136  are arched towards the bearing center in a slightly convex manner, as can be seen in  FIG. 3 , and in cross-section, they have a straight configuration, as can be seen in  FIG. 4 . In a non-worn-out bearing shell  34 , the shaft journal  28  and the bearing surfaces  36  practically touch each other only on a punctual contact area. 
   The bearing shell  34  consists of two bearing shell halves  38   1 ,  38   2  between which a deformation zone  40  is provided. The deformation zone  40  is formed by a radially and axially continuous radial gap  42  comprising a graphite sheet as deformation element  44 . The gap width of the radial gap  42  and thus the thickness of the graphite sheet amounts to about 0,5 mm. 
   The bearing shell  34  is inserted into a corresponding segment-like recess  33  of the bearing housing  32 . The two bearing shell halves  38   1 ,  38   2  consist of zirconium oxide, but can also consist of another ceramic material, such as, for example, silicon nitride or silicon carbide. 
   In the region of the closed bottom of the bearing housing, an axial abutment plate  46  of ceramics is respectively let in. 
   As results particularly from  FIG. 1 , the force resultant R of the radial forces acting upon the two slide bearings  26   1 ,  26   2 , resulting from the two tensioned metal band legs, acts approximately in the direction of the median line of the two legs of the metal band  12 , 12 ′. The two bearing surfaces  36  are arranged at both sides of the radial force resultant R at approximately the same angle, i.e., the radial force resultant R lies about centrally between the two bearing surfaces  36 . 
   In case of strong tensile forces of the metal band  12 , 12 ′, high radial forces are transferred from the deflecting shaft  16  or its shaft journals  28  onto the slide bearings  26   1 ,  26   2 . Due to a certain elasticity, i.e. resilience, of the metal bearing housing  32 , deformations are permitted in the region of the deformation zone  40 . By the deformation zone  40  in the form of the flexible graphite sheet, a breakage and separation of the connection between the two bearing shell halves  38   1 ,  38   2  is reliably avoided. Thereby, a damaging or a breaking of the bearing shell  34  is excluded and the reliability and average service life of the bearing shells  34  are improved. 
   With its shaft journals, the stabilizing shaft  18  is also supported in slide bearings corresponding to those of the deflecting shaft  16 . 
   By providing a deformation zone with a deformation element between the two bearing surfaces  36 , the two bearing shell halves  38   1 ,  38   2  can be bent to each other when high radial forces occur, without a material breakage and hence a destruction of the bearing shell being able to occur in the zone between the two bearing shell halves  38   1 ,  38   2 . 
   The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.