Abstract:
A plurality of cylinder sections are welded together to form a milling cylinder, wherein, prior to welding, individual cylinder sections are machined in the region of their end edges to be welded, using at least one machining tool. Furthermore, the cylinder section to be machined is provided with inwardly oriented bracing means, wherein a temporary axle is fitted on the bracing means such that the temporary axle is oriented in the mid-axis of the cylinder section, and wherein the at least one machining tool is fastened to the temporary axle by means of a holder and the machining tool is rotated relative to the cylinder section about or with the temporary axle during the machining of the end edges.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is the U.S. national phase application of International Application No. PCT/EP2013/065802 filed Jul. 26, 2013, which claims priority to German Patent Application No. DE 102012108163.8 filed Sep. 3, 2012. Each of these applications is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates generally to the field of manufacturing large mill cylinders. More specifically, the invention relates to a method for manufacturing large mill cylinders, wherein the mill cylinder is composed of a plurality of cylinder sections which are welded to one another. 
     Description of the Related Art 
     Mill cylinders comprising a plurality of cylindrical sections welded to one another may display diameters of 3 to 12 m and more and are employed for ball mills, autogenous mills, and semi-autogenous mills, for example. These mills typically are circumferentially mounted, wherein raceways which interact with correspondingly configured friction bearings are provided on the end regions of the mill cylinder, as shown for example in German Patent Application No. DE 89 13 313 U1. It is of decisive significance in the case of this type of mounting that the individual cylinder sections are exactly aligned in relation to the common mill axis and also the end edges to be welded to one another are aligned so as to be concentric and orthogonal in relation to the raceway face. 
     On account of the large dimensions, the complete mill cylinder cannot be shipped any more. Therefore, it is typical that the individual cylinder sections are shipped to the construction site having end edges which are prepared for welding and are welded to one another only on site. To this end, the applicant has developed what is referred to as the Polweld® method. 
     Since ever larger mill cylinders have been built in recent times, shipping of the individual cylinder sections to the construction site is also associated with enormous costs. Here, not only the shipping costs but also any applicable import duties on semi-finished products have to be taken into account. Therefore, it has been proposed in DE 89 13 313 U1 to divide the mill cylinders and the raceways in the longitudinal direction and to interconnect the component parts using flanges. 
     German Patent Application No. DE 12 81 810 A1 discloses a centering device for large cylinder sections to be welded to one another, in particular in the case of tube mills. 
     SUMMARY 
     The invention is based on the object of providing a method for manufacturing large mill cylinders which are composed of a plurality of cylinder sections, which method is distinguished from the prior art by virtue of the lower manufacturing costs, for example. 
     In a method according to an exemplary embodiment of the invention, a plurality of cylinder sections are welded to one another, wherein prior to welding at least individual cylinder sections, in the region of their end edges to be welded, are machined using at least one machining tool. Moreover, the cylinder portion to be machined is provided with inwardly aligned reinforcements, wherein a temporary axle is attached to the reinforcements in such a manner that the temporary axle is aligned in the central axis of the cylinder section, and wherein the at least one machining tool is fastened to the temporary axle by means of a mount, and rotation of the machining tool in relation to the cylinder section about or together with the temporary axle takes place during machining of the end edges, and the temporary axle is dismantled and removed post machining of the end edges. 
     Another aspect of the invention, according to an embodiment, relates to machining of the raceways of the mill cylinder, wherein on two of the cylinder sections which are welded to one another, on their circumferential face, in each case one raceway is provided for mounting the mill cylinder. Here too, the mill cylinder which is composed of the cylinder sections, which are welded to one another is provided with inwardly aligned reinforcements, wherein at least one temporary axle is attached to the reinforcements in such a manner that the temporary axle is aligned in the central axis of the mill cylinder. In turn, the machining tool is fastened to the temporary axle by means of a mount, such that rotation of the machining tool in relation to the mill cylinder about or together with the temporary axle takes place during machining of the raceways using the machining tool, and the at least one temporary axle is dismantled and removed post machining of the raceways. 
     A temporary axle can be fastened to the reinforcements and aligned in the central axis of the cylinder section, or the mill cylinder, respectively, in a comparatively simply manner. A mount element which is fastened to this temporary axle enables machining of the end edges of the individual cylinder sections, or of the raceways provided on the circumferential face of the mill cylinder, respectively, in a manner which is concentrically and orthogonally aligned in relation to said axle. It is also ensured in this way that concentric raceways or raceway surfaces, respectively, are created. 
     A grinding tool and/or a milling tool and/or a turning tool and/or a boring tool may be employed in particular as a machining tool. The mount of the machining tool preferably is aligned such that machining of the end edges of the cylinder sections takes place in a concentric and orthogonal manner in relation to the temporary axle. Machining of the raceways of the mill cylinder also takes place in a concentric manner in relation to the temporary axle. 
     According to another embodiment of the invention, the cylinder sections are manufactured from rolled sheet material, wherein this is preferably carried out at the construction site. Moreover, the sheet material required therefor can be shipped significantly more cost effectively than prefabricated cylinder sections. 
     It is furthermore expedient for the individual machined cylinder sections to be welded to one another at the future operating site of the mill cylinder. This has the advantage that the construction of additional, expensive foundations for the mounting during welding can be dispensed with. It is, therefore, also expedient for machining of the raceways to take place at the future operating site of the mill cylinder, using mill foundations which are provided there for the future mounting of the mill cylinder, wherein the at least one temporary axle is mounted in temporary bearings and the temporary bearings are directly or indirectly supported on the mill foundations which are provided for the future mounting. 
     The reinforcements are dismantled and disposed of during the final commissioning of the mill/mill cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures and wherein: 
         FIG. 1  shows a front view of a cylinder section having reinforcements; 
         FIG. 2  shows a side view of the cylinder section of  FIG. 1 ; 
         FIG. 3  shows a schematic illustration of machining the end edges of a cylinder section, using a machine tool rotating about the temporary axle; 
         FIG. 4  shows a schematic illustration of machining the end edge and the raceway of a cylinder section, using a machine tool rotating about the temporary axle; 
         FIG. 5  shows a schematic illustration of machining the end edge and the raceway of a cylinder section, using a machine tool rotating together with the temporary axle; 
         FIG. 6  shows a schematic illustration of the cylinder section when applying borings in the cylinder sleeve, using a boring tool rotating about the temporary axle; 
         FIG. 7  shows a schematic illustration during machining of the raceways of a mill cylinder; and 
         FIG. 8  shows a schematic illustration of the mill cylinder mounted in temporary bearings, having a mill unit. 
     
    
    
     DETAILED DESCRIPTION 
     The cylinder section which is illustrated in  FIGS. 1 and 2  is manufactured from rolled sheet material and displays a wall thickness in the range of 30 mm to 220 mm, and an outer diameter of 3 m to 14 m, for example. The length of the cylinder section  1  typically is in the range of 1.5 m to 6 m. 
     The cylinder section is provided with inwardly aligned reinforcements  2  which is in each case arranged in proximity of the end edges  1   a ,  1   b . These reinforcements in each case are composed of a central disk  2   b  and a multiplicity of radial stays  2   a , the radial stays  2   a  being welded to the inner side of the cylinder section  1 . 
     In order to now be able to weld a plurality of these cylinder sections to one another to form a mill cylinder, the end edges  1   a ,  1   b  have to be machined using a machining tool ( FIG. 3 ). To this end, a temporary axle  3  is inserted through the cylinder section  1  and attached in such a manner in the region of the reinforcements  2  that the temporary axle is exactly aligned in the central axis of the cylinder section. To this end, the central disk  2   b  of the reinforcement  2  is provided with a central opening  2   c  which in diameter is somewhat larger than the diameter of the temporary axle  3 . Readjustment means  2   d , by way of which the temporary axle can be fastened to the reinforcement  2  and exactly aligned in the central axis of the cylinder section, are provide in the region of the opening  2   c  ( FIG. 1 ). These readjustment means may be formed by readjustment screws, for example, or any type of clamping, such as clamping screws, setting screws, readjustment wedges, cams.  FIG. 3  shows the situation with the aligned temporary axle  3 . The cylinder section expediently is mounted in the region of its circumferential face  1   e  in suitable bearing shoes. 
     As can be identified from  FIG. 3 , on the two ends of the temporary axle  3  which project out of the cylinder section  1 , there is in each case a machining tool  4  having a mount  4   a  which is mounted on the fixed temporary axle  3  by way of a bearing  4   b . Furthermore, a displacement mechanism  4   c  which carries the actual tool  4   d  and enables displacement of the tool  4   d  in the direction of and perpendicularly to the temporary axle  3  (arrows  16 ), and is thus adjustable in the direction of and perpendicularly to the central axis  1   c  of the cylinder section  1 , is provided on the mount  4   a . A turning tool or a milling tool, for example, is employed as a tool  4   d  for machining the end edges  1   a ,  1   b.    
     The end edges  1   a  and  1   b  are turned or milled from the inside and the outside, such that a central web  1   d  is created. The outer end face of this web  1   d  here lies exactly in a plane which is perpendicularly aligned to the central axis  1   c.    
     During later welding of a plurality of cylinder sections, the webs of adjacent cylinder sections directly abut one another and in this way can be exactly aligned and welded in that the material previously removed by the machining tool is filled in again with welding material. 
       FIG. 4  shows machining of a cylinder section  1  which on its outer side is provided with a raceway  1   f . The raceway is formed by a region of the cylinder sleeve  1   e , which displays a greater wall thickness. In order to ensure later smooth revolving of the mill cylinder, the running surface of the raceway  1   f  has to be aligned so as to be absolutely parallel with the central axis  1   c  of the cylinder section  1 . This may also take place by way of the machining tool  4 . The mount  4   a  and the displacement mechanism  4   c  here are configured such that the complete raceway  1   f  can be machined. 
     Instead of a fixedly disposed temporary axle  3  about which the machining tool  4  rotates, it may also be provided that the temporary axle  3  is rotatably mounted in the region of the reinforcements  2  and the machining tool is connected to the temporary axle  3  in a rotationally fixed manner ( FIG. 5 ). For this purpose, the temporary axle would have to be mounted on the reinforcements  2  with the aid of bearings  5 , in particular in the region of the central disk  2   a.    
     In both variants of the embodiment the mount  4   a  and, in particular, the connection to the temporary axle  3 , are to be configured such that the tool  4   d  which comes into machining contact with the cylinder section is guided so as to be exactly in a plane which is perpendicular to the temporary axle  3 . 
     Using the concept of a machining tool with rotates together with or about a temporary axle, is it also possible for borings which are aligned in an exactly radial manner to be incorporated in the cylinder sleeve  1   e  of the cylinder section  1  (see  FIG. 6 ). To this end, a machining tool  6  is mounted in the interior of the cylinder section  1  by means of a bearing  6   b  on the temporary axle  3 . The mount  6   a , in turn, carries a displacement mechanism  6   c  and a drill  6   d  which is aligned in an exactly radial manner. Displacement of the machining tool in the direction of the temporary axle  3  expediently takes place in the region of the bearing  6   b  by way of a suitable mechanism which is not illustrated in more detail here. 
     According to a preferred exemplary embodiment, welding of the prepared cylinder sections at the future operating site of the mill cylinder takes place using mill foundations  7  which are provided there for the future mounting of the mill cylinder. To this end, a temporary support structure  8  having support bearings  9 ,  10 , or seats, respectively, which are provided for each cylinder portion, is disposed between the mill foundations  7 . The support bearings  9 ,  10  are adjustable for height and thus enable exact alignment of the cylinder sections  1  which are to be welded to one another and which during welding touch one another by way of their webs  1   d.    
     The welded mill cylinder  11 , on both its ends, displays the cylinder sections  1  which are provided with the raceways if and which, in turn, are provided with reinforcements  2  which mount the temporary axles  3 ′ which, in turn, are aligned to the mill-cylinder axle  11   a  of the mill cylinder. In this exemplary embodiment the temporary axles  1 ′ are configured as axle stubs. However, a continuous axle would also be conceivable. The temporary axles  3 ′, in turn, are mounted in temporary bearings  12  which are directly or indirectly supported on the mill foundations  7  which are provided for the future mounting. In the illustrated exemplary embodiment, supports  7   a  for carrying the temporary bearings  12  are attached to the foundations  7 . 
     During machining according to  FIGS. 4 and 5 , the raceway if expediently are only pre-machined, such that the final manufacturing of the running surface takes place after welding of the cylinder sections, wherein the mill cylinder is mounted by way of the temporary axles  3 ′ and the running surface thus does not yet come in contact with the future friction-shoe bearings  13 . In turn, a machining tool  14  which again comprises a mount  14   a , a bearing  14   b , a displacement mechanism  14   c , and a tool  14   d , is provided for final machining of the raceways  1   f.  The machining tool  14  is disposed with the bearing  14  on the temporary shaft  3 ′, such that said machining tool  14  can rotate together with or about the temporary axle and here comes into machining contact with the raceway  1   f . A grinding tool may be applied here as the tool  14   b , for example. 
     After completion of the raceways  1 ′ e , the mill cylinder  11  is lowered, so as to establish contact between the raceways  1 ′ e  and the friction-shoe bearings  13 . The temporary axles  3 ′ and the reinforcements are dismantled and removed. Here, the temporary axles  3 ′ not only enable rotation of the machining tool  14  but also serve for rotation of the mill cylinder  11 , such that all regions of the raceway  1 ′ e  can be approached and machined by the machining tool  14 . 
     The exemplary embodiment according to  FIG. 8  additionally provides a sheet-metal roller  15  which is screwed to the foundation  7 , or to the supports  7   a  thereof, respectively. Using this sheet-metal roller  15 , the individual cylinder sections  1  are manufactured. By way of a suitable displacement mechanism the individual cylinder portions then can be displaced toward the left onto the support structure  8  for machining. The support structure  8 , having its support bearings  9 ,  10 , is also suitable for mounting the cylinder sections for machining the end edges thereof, according to  FIGS. 3 to 6 . This means that the individual cylinder sections  1  are held by the support bearings  9 ,  10  via the cylinder sleeves of said cylinder sections  1 , and the temporary axles  3  merely serve for mounting the machining tools  4 . As soon as all cylinder portions have been prepared for the welding operation, they may be welded together there and then. To this end, in particular the Polweld® method of the applicant, which is known in practice, is applied. 
     The application of the Polweld® method requires a very exacting preparation of the weld seam, in that the front edges of the webs  1   d  of the cylinder portions  1  lie exactly in one plane which is aligned so as to be perpendicular to the central axis of the cylinder portion. This preparation of the weld seam may reliably take place using the machining tool  4  which is rotatable about or together with the temporary axle  3 . In this way it is possible for only the flat sheet metal plates, or the sheet material, respectively, to be shipped to the construction site and for the cylinders to be able to be rolled and correspondingly machined on site. On account thereof, the shipping costs and also the import duties can be significantly reduced. 
     Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.