Patent Publication Number: US-4094628-A

Title: Rotary drum

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to rotary drums for treating materials; and, more particularly, to rotary drums having unitary material treating members forming a portion of the drum shell wall. 
     2. Description of the Prior Art 
     Rotary drums are used in a variety of industrial processes for treating liquid, pulverous and granular materials. Rotary kilns, for example, provide a familiar example of the use of such drums. 
     Rotary drums typically comprise a plurality of joined ring-shaped sections including one or more sections having material treating members such as scoops, cooling pipe supports and aperture coamings, extending radially inwardly or outwardly to facilitate treating or advancing the material. The ring-shaped sections are typically made of rolled and welded steel plate, and there is relatively little difference between the sections containing the material treating members and the remaining sections, except that the former may be made of an increased thickness plate for greater strength and rigidity. 
     The material treating members do not form a part of the wall but rather are attached to an already formed wall. Typically, these members are made of steel plate parts welded to one another and to the shell plate. Alternatively, they may comprise castings welded to the internal or external surfaces of one or more of the shell plates. 
     There are serious problems associated with the manufacture and use of the material treating members of these drums. The welded treating members are very difficult to fabricate. They typically require very complex welding operations at locations which are nearly inaccessible, e.g., the space beneath and between the tubes of a planetary cooler. In addition, the welded seams in these treating members often produce undesirable shearing stresses and, as a result, a weakening of the welded joints. 
     Drums with cast treating members attached to the wall have also been difficult to fabricate. The abrupt changes in thickness at the juncture between the rolled shell plates and the cast members has required the use of very high preheating temperatures with the consequence that manual welding is impractical. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a rotary drum for treating materials comprises a drum shell having a generally tubular configuration wall and one or more unitary material treating members forming a portion of the wall. In a preferred embodiment, the drum shell comprises a plurality of ring-shaped sections mechanically joined together in axial alignment wherein at least one of the sections has a unitary material treating member forming a portion of the section wall. In typical applications, the treating members are cast steel members and the remaining portions of the drum shell are predominantly rolled plate steel. 
     The advantages of this drum include easier fabrication with a reduction in the extent of welding, avoidance of welding in inaccessible locations, elimination of abrupt changes in thickness and, in operation, a reduction of unwanted shearing stresses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The advantages, nature and various features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with the accompanying drawing in which: 
     FIG. 1 is a schematic side view of one end of a rotary drum in accordance with the invention illustratively shown as the outlet end of a rotary kiln; 
     FIG. 2 is a cross-section showing a section of the rotary drum of FIG. 1 which includes a material treating member comprising an aperture member; 
     FIG. 3 is a section taken on the line 3--3 in FIG. 2 to further illustrate the features of the aperture member; 
     FIG. 4 is a cross-section of the rotary drum of FIG. 1 which includes a material treating member comprising a cooler tube support base; 
     FIG. 5 is a longitudinal section taken on the line 5--5 in FIG. 4; and 
     FIG. 6 is a cross-section of the rotary drum of FIG. 1 which includes a material treating member comprising a scoop support base. 
    
    
     For convenience of reference, corresponding structural elements are denoted by the same reference numeral throughout the drawing. 
     DETAILED DESCRIPTION 
     Referring to the drawings, FIG. 1 illustrates a rotary drum in accordance with the invention illustratively shown as the outlet end of a rotary kiln. Rotary drum 1 is comprised of ring-shaped sections 1a, 1b, 1c and 1d, each of shaped metal plate such as rolled steel, and one or more ring-shaped sections 2a, 2b and 2c, each containing at least one unitary material treating member forming a portion of the drum wall and the section wall. The term unitary material treating member as used herein refers broadly to any member having a circumferential portion forming part of the drum wall and a radially portion extending in the radial direction to facilitate the treatment or advancement of material. It includes unitary support members upon which further radial projections can be mounted. 
     Each of the ring-shaped sections is joined to its adjacent sections on either side as by welding along circumferential cross seams. The elements of the individual sections are joined together as by welding along longitudinal seams. 
     Ring-shaped section 2a comprises a plurality of unitary aperture members 3 each mechanically joined along its edges, as by welding, to the remainder of the section 2a and to the adjacent sections 1a and 1b on either side of section 2a. These aperture sections, which are preferably made of cast steel, permit material to be discharged from the drum into cooler tubes 6 along a path indicated by arrow. For the sake of clarity, only two of the cooler tubes are shown but the others are evenly distributed around the drum periphery in planetary fashion. 
     Ring-shaped sections 2b and 2c comprise a plurality of unitary support base members. In this particular embodiment, each ring-shaped section 2b and 2c is composed alternatively of support base members 4 and shaped metal plate elements 5. The respective elements are mechanically joined together along their edges and to the edges of adjacent sections as by welding. Preferably the support base members are made of cast steel and the shaped metal plates are rolled plate steel. The support base members 4 act as the bases for supports 7 of the cooler tubes 6. 
     The rotary drum is rotatably supported by live rings 8; and, in application as a kiln, a burner pipe (undesignated) projects into one end. 
     FIGS. 2 and 3 illustrate in greater detail the features of a material treating member providing a coamed aperture and utilized as the outlet members in ring-shaped section 2a of FIG. 1. Each outlet member is a unitary member comprising a circumferential portion 3 and a radially projecting coaming portion 13 surrounding a round or oval aperture 14. The circumferential portion 3 is preferably in the form of a curved rectangular plate having a curvature in the circumferential direction corresponding to that of the drum and a longitudinal dimension corresponding to the longitudinal width of the associated ring-shaped section. In preferred embodiments, the coaming 13 includes a circular flange 13a as illustrated by the dotted line circle in FIG. 3. The aperture member is preferably made of cast steel and is joined to the remaining portion of its associated section by welding respective edges along longitudinal seams 15 and to adjacent sections by welding respective edges along circumferential seams. The coaming 13 may be provided with holes 16 for permitting the attachment by bolts of a lining pipe (not shown) coupled to aperture 14. 
     In application, the flange of an outlet pipe (not shown) may be welded, riveted or bolted to flange 13a. 
     FIGS. 4 and 5 illustrate in greater detail the features of a material treating member providing a support base for the cooler tubes 6 and utilized as the support base members in ring-shaped sections 2b and 2c of FIG. 1. The unitary support base member 4 comprises a circumferential portion 4a in the form of a curved rectangular plate and radially projecting base portions 4. The circumferential portion 4a has a curvature corresponding to that of the drum. 
     An upper support member 10 is shown attached to the support base as by welding aling the surfaces 11. Alternatively, the upper support member could be attached by providing both the support base and the upper support with corresponding flanges and bolting or riveting. The upper support member includes a flange 12 curved to permit nesting of tube 6. 
     The support base 4 is a unitary member preferably of cast steel. If forms a portion of the drum wall and is preferably joined to the remaining portion of the drum wall as by welding longitudinal seams 9a along its longitudinal edges and circumferential cross seams 9b between its edges and the respective edges of adjacent sections on either side. 
     FIG. 6 shows in detail the features of a material treating element which forms a unitary support base 17 for a scoop member 18 mounted inside a rotary drum for advancing material through the drum during rotation of the drum. The support base includes a circumferential portion forming a portion of the drum wall and a radially projecting portion providing support for scoop 18. The support base member is joined to the remaining portion of the drum wall as by welded seams along its edges 9a. Both support base 17 and scoop member 18 are preferably cast steel, and adjacent elements 5 may be rolled steel plate. The arrow indicates the direction of drum rotation. 
     A number of significant advantages accrue from this combination of drum wall and material treating members. The extent of welding is substantially reduced. In addition, the necessity of welding at inaccessible points is avoided, and the risk of producing undesired shearing stresses is reduced. The use of cast members rather than rolled and welded members avoids sharp variations in thickness, permitting freer scope for selecting thickness of material, which further reduces the risk of damaging stresses. The required welding is limited to welding electroslag seams between the individual elements of a shell section and between adjacent sections. Suich electroslag welds are relatively easy to perform and control; and they permit the intense preheating of plate material and cast material. In addition, the cast parts may be made with smoother and more uniform transitions between materials of different thickness so that the heat stresses to which the material is subjected are reduced. Finally, it is possible to prefabricate divided shell sections corresponding to a fraction of the shell circumference (e.g. one-third or one-fourth), thereby reducing the welding required during installation. 
     A shell section as described above may consist of cast elements alternating with rolled plate elements or exclusively of cast elements, depending on the circumstances. Further, the cast element, or at least one of the cast elements, may form a coaming surrounding an aperture in the element. In use, such an aperture allows material to pass through the shell wall. 
     If the drum is a rotary kilm or a cooler drum a cast coaming surrounding an aperture may act as a coupling for a pipe leading from the drum shell to a cooler tube mounted on the outside of the shell. In addition, the cast element, or at least one of the cast elements, can form at least part of the support for a cooler tube mounted on the outside of the drum shell. Alternatively, the cast element may act as a lifter or scraper within the shell or as a support for such a lifter or scraper. 
     While the invention has been described in connection with a small number of specific embodiments, it is to be understood that these embodiments are merely illustrative of the many possible specific embodiments which can represent applications of the principles of the invention. Thus, numerous and varied other devices can be made by those skilled in the art without departing from the spirit and scope of the present invention.