Patent Publication Number: US-6705858-B2

Title: Door assembly for rotary furnace

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of application Ser. No. 10/126,332 filed Apr. 19, 2002, now U.S. Pat. No. 6,530,779, which is a continuation of application Ser. No. 09/770,025 filed Jan. 25, 2001, now U.S. Pat. No. 6,435,864, which is a continuation of application Ser. No. 09/558,696 filed Apr. 25, 2000, now U.S. Pat. No. 6,213,763. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to rotary furnaces of the type utilized in the recycling of aluminum, and more particularly to an improved door construction useful in conjunction with rotary furnaces to enhance the efficiency thereof. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The recycling of aluminum frequently involves the use of rotary furnaces. Typically, aluminum scrap and/or used aluminum products are received in a rotary furnace for melting. When melting is complete, the molten aluminum is discharged from the rotary furnace for further processing. 
     More specifically, rotary furnaces of the type utilized in aluminum recycling comprise a large drum which is supported for rotation about a longitudinal axis. One end of the drum is closed with the other end of the drum being normally closed by a door. At the start of each operating cycle, the drum is tilted upwardly for charging with aluminum to be melted. The drum is tilted downwardly into a horizontal orientation and the door is closed. The temperature within the drum is then raised sufficiently to melt the aluminum received therein. After the aluminum is melted, the drum is tilted downwardly to discharge the aluminum for further processing. 
     Heretofore, the doors used to close rotary furnaces during the melting of aluminum received therein have been supported independently from the drum of the furnace. This means that the door must be fully opened both during the charging of the drum with aluminum to be melted and during the discharge of the aluminum from the drum. The requirement of fully opening the drum to effect discharge of molten aluminum therefrom is disadvantageous because it allows the drum to cool thereby requiring substantial reheating for the next operating cycle. 
     The present invention comprises an improvement during construction for rotary furnaces which overcomes the foregoing and other difficulties which have long characterized the prior art. In accordance with the broader aspects of the invention, a rotary furnace is provided with a door which is supported for pivotal movement with the drum between its upwardly inclined charging orientation, its horizontal melting orientation, and its downwardly inclined discharging orientation. Because the door pivots with the drum, it is not necessary to fully open the door in order to discharge molten aluminum therefrom. Rather, the lower portion of the door is separately openable to permit discharging of molten aluminum, thereby retaining heat within the drum. 
     In accordance with more specific aspects of the invention, a rotary furnace includes a drum that is supported on a frame for pivotal movement between an upwardly inclined charging orientation, a horizontal melting orientation, and a downwardly inclined discharge orientation. A door for the drum is mounted on the same frame as the drum for pivotal movement therewith. The door is fully openable to facilitate charging of the drum with aluminum to be melted. The door includes a pour door comprising the lower portion thereof which is separately openable to facilitate the discharge of molten aluminum from the drum. 
     The door of the present invention further includes apparatus for heating the interior of the drum to melt the aluminum contained therein. Typically, the heating apparatus comprises a burner fueled by natural gas, however, other heating apparatus may be utilized in the practice of the invention. The heating apparatus is operated not only during the melting of the aluminum received in the drum, but also during the discharge of molten aluminum from the drum so that the interior of the drum is not significantly cooled during the discharging of the aluminum. In this manner the operational efficiency of rotary furnaces incorporating the door of the present invention is substantially increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings, wherein: 
     FIG. 1 is a perspective view of a rotary furnace incorporating a door comprising the present invention and illustrating the door in its closed position; 
     FIG. 2 is an illustration similar to FIG. 1 showing the door of the rotary furnace in its open position; 
     FIG. 3 is a bottom view of the rotary furnace of FIG. 1 further illustrating the open and closed positions of the door of the present invention; 
     FIG. 4 is a side view of the door of the present invention illustrating the construction and operation of the pouring door component thereof; 
     FIG. 5 is a view similar to FIG. 4 further illustrating the construction and operation of the pouring door; 
     FIG. 6 is a top view of the rotary furnace door of the present invention; 
     FIG. 7 is a front view of the rotary furnace door of the present invention; 
     FIG. 8 is a side view of a rotary furnace incorporating the door of the present invention showing the furnace in its upwardly inclined charging orientation; 
     FIG. 9 is an illustration of a rotary furnace incorporating the door of the present invention showing the rotary furnace in its horizontally disposed melting orientation; 
     FIG. 9A is an illustration of the drive mechanism for the rotary furnace of FIG. 1; and 
     FIG. 10 is an illustration of the rotary furnace of FIGS. 8 and 9 showing the rotary furnace in its downwardly disposed discharging orientation and illustrating the pouring door of the door of the present invention in its open configuration. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the Drawings, and particularly to FIGS. 1 and 2 thereof, there is shown a rotary furnace  20  incorporating the present invention. The rotary furnace  20  includes a frame  22  which is supported on an underlying surface  24 . A pair of support members  26  support the forward end  28  of the frame  22  on trunnions  30 . The rearward end  32  of the frame  22  is supported by fluid powered cylinders  34 , which are selectively extendable and retractable to pivot the frame  22  and the components carried thereby relative to the underlying surface  24  about a horizontal axis defined by the trunnions  30 . 
     The rotary furnace  20  further includes a drum  40  which receives aluminum and/or other materials for melting. The rearward end  42  of the drum  40  is closed. The forward end  44  of the drum  40  is normally closed by a door  46 . FIG. 1 illustrates the door  46  in its closed position, and FIG. 2 illustrates the door  46  in its opened position. 
     The drum  40  is provided with a pair of bearing rings  50 . Bearing assemblies  52  mounted on the frame  22  engage the bearing rings  50  to support the drum  40  for rotation about a nominally horizontal axis extending perpendicularly to the axis defined by the trunnions  30 . The drum  40  is rotated about its axis by a drive mechanism  54  including a drive motor  56  and a pinion  58  which is mounted in mesh with a ring gear  60  mounted on the drum  40 . 
     The relationship of the door  46  to the drum  40  is further illustrated in FIG. 3 wherein the door  46  is shown in its closed position in dashed lines and in its open position in full lines. The door  46  includes a swing arm  66  which supports the door  46  for pivotal movement relative to the frame  22  about a nominally vertically disposed axis  68  extending perpendicularly to the axis of rotation of the drum  40  and to the axis of pivotal movement of the drum  40  as defined by the trunnions  30 . The door  46  is pivoted between its opened and closed positions by a fluid powered cylinder  70  which extends between the frame  22  and a bell crank  72  mounted on the swing arm  66 . 
     The door  46  of the rotary furnace  20  is further illustrated in FIGS. 4,  5 ,  6 , and  7 . The door  46  supports a heating apparatus  80  which supplies the heat necessary to melt the aluminum and/or other material contained within the drum  40 . The heating apparatus  80  may comprise a North American ATP (adaptive thermal profile) low NOx natural gas combustion air burner, designation 4484-14. Other types and kinds of heating apparatus may be, utilized in the practice of the invention depending upon the requirements of particular applications thereof. 
     The lower portion of the door  46  comprises a pouring door  82  which is illustrated in its open position in FIG.  4  and in its closed position in FIG.  5 . The pouring door  82  is supported for pivotal movement about a nominally horizontal axis  84  between the positions illustrated in FIG.  4  and FIG.  5 . The pouring door  82  is actuated by a fluid powered cylinder  86  which operates the pouring door  82  through a linkage  88 . 
     The operation of the rotary furnace  20 , and in particular the door  46  thereof, is illustrated in FIGS. 8,  9 , and  10 . In FIG. 8, the drum  40  of the rotary furnace  20  is pivoted upwardly under the action of the fluid powered cylinders  34 . The door  46  is pivoted to its open position under the action of the fluid powered cylinder  70 . The forward end  44  of the drum  40  is thereby fully opened for charging with aluminum and/or other materials to be melted. 
     In FIG. 9, the axis of rotation of the drum  40  extends horizontally. The fluid powered cylinder  70  is actuated to close the door  46 . The drive mechanism  54  is actuated to rotate the drum  40  about its rotational axis, and the heating apparatus  80  is operated to heat the interior of the drum  40 , thereby melting the contents thereof. 
     After the contents of the drum are melted, the fluid powered cylinders  34  are actuated to pivot the drum  40  into the orientation illustrated in FIG.  10 . The fluid powered cylinder  86  is actuated to open the pouring door  82 , whereupon molten metal MM is discharged from the drum  40  into a suitable receiving vessel  90 . 
     During discharge of the molten metal MM from the interior of the drum  40  through the now open pouring door  82 , the door  46  remains closed. During the discharge of the molten metal MM into the vessel  90 , the heating apparatus  80  is operated at a low level. Because the door  46  remains closed and the operation of the heating apparatus  80  is continued, the interior of the drum  40  remains hot during the discharge of molten metal therefrom. In this manner, substantial cost savings are achieved since it is not necessary to reheat the interior of the drum  40  when the next charge of material to be melted is received therein. 
     Although preferred embodiments of the invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention.