Abstract:
An insulating flight for a dryer incorporates inner and outer plates with insulation between them. The concave surfaces of the inner and outer plates provide a space for the insulation and allow for thermal expansion without stressing the welds between the inner and outer plates.

Description:
BACKGROUND OF THE INVENTION 
   This application claims priority from provisional application Ser. No. 60/405,499 filed Aug. 23, 2002. 

   The present invention relates to dryers for heating and drying aggregate or soil, and, in particular, to special insulating flights for lining the combustion area of the dryers. 
   SUMMARY OF THE INVENTION 
   The present invention improves over the prior art combustion flights by providing combustion flights that are insulated. This protects the shell structure and saves energy. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is sectional view of a typical prior art dryer with only some of the flights shown for clarity; 
       FIG. 2  is a view along line  2 — 2  of  FIG. 1 ; 
       FIG. 3  is a perspective view of an insulating flight made in accordance with the present invention; 
       FIG. 4  is a plan view of two side-by-side insulating flights of the type shown in  FIG. 3 , as they would typically be mounted inside a dryer; 
       FIG. 5  is a view along line  5 — 5  of  FIG. 4 ;  
       FIGS. 6–8  are broken away, sectional views showing the insulated flights of  FIG. 3  mounted on various diameters of dryer shells, showing that the amount of overlap may vary slightly, depending upon the diameter of the shell. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a typical prior art dryer  10 . The material to be heated enters the dryer  10  on the right end  12  and leaves on the left end  14 . The burner is located on the left end  14 . In the left-most section  16  of the dryer  10 , for about 6–12 feet, are combustion flights  20 , the end views of which are shown in  FIG. 2 . These flights are convex on their inner surfaces, facing toward the axis  18  of the dryer  10 , and they are concave on their outer surfaces, facing toward the dryer shell  22 . The flights  20  overlap each other to provide a kind of lining for the dryer  10 , protecting the dryer shell  22  from the direct heat of the burner. The flights  20  are secured to the dryer  10  by being bolted onto L-shaped clips  24 , which are welded to the dryer shell  22 . 
     FIGS. 3–8  depict insulating flights  120  made in accordance with the present invention.  FIG. 3  is a perspective view of one of these insulating flights  120  which may be designed to be a direct replacement for the combustion flights  20  found in the prior art. The insulating flights  120  include a thick, convex inner metal plate  126  but, on the concave outer surface  128  (See  FIG. 5 ) of the inner plate  126  is a sheet  130  of two-inch thick ceramic fiber insulation (similar to fiberglass batting used to insulate buildings, but made with ceramic fibers that can withstand higher temperatures than can fiberglass). The sheets  130  that  have been used include Premier Brand ceramic fiber blankets, which are rated either at 1,900° F. or 2,400° F., but it is understood that other insulating materials and other thicknesses may be used without departing from the scope of this invention. 
   On the outside of the ceramic fiber insulation  130  is an outer metal plate  132 , which is convex toward the dryer shell  22  and concave toward the axis  18  of the dryer. The outer metal plate  132  preferably is made of a thinner gauge material than the inner plate  126  and is tack welded to the inner plate along its edge, forming a hollow compartment between the inner and outer plates  126 ,  132 , which houses the ceramic fiber insulation  130 . Thus, a type of sandwich is formed, with inner and outer plates  126 ,  132 , and with ceramic fiber insulation  130  between the plates  126 ,  132 . These insulating flights  120  are then bolted to L-shaped clips  124  (see  FIGS. 3 and 4 ) by means of bolts  134 , and the clips  124  are welded to the inside of the drier shell  22  in the same manner as were the uninsulated flights  20  of the prior art. 
     FIGS. 6 ,  7 , and  8  show the insulating flights  120  mounted on various diameters of dryer shells  122 , showing that the amount of overlap may vary slightly, depending upon the diameter of the shell  122 . 
     FIG. 4  is taken from inside the dryer looking outwardly. It shows the innermost surface  126  of the insulated flights  120  as well as the L-shaped clips  124  and the bolts  134  that secure the flights  120  to the clips  124 . The outer edge of each clip  124  is welded to the inner surface of the shell  122 .  
   When the burner is fired up, the inner plates  126  of the insulating flights  120  will heat up and expand. The convex shape of the outer metal plate  132  permits it to straighten out as the inner plate  126  expands, without stressing the welds between the inner and outer plates  126 ,  132 . The ceramic fiber insulation  130  also flexes to accommodate expansion and contraction of the plates  126 ,  132 . 
   A prior art dryer  10 , as shown in  FIG. 1 , may be converted to an insulated dryer by replacing the old, uninsulated flights  20  with the new, insulating flights  120 . The conversion simply requires unbolting the old flights  20  and bolting in the new flights  120 . The result is a dryer  10  that can operate at higher temperatures without harming the shell  22  and that can operate more efficiently, with less wasted energy. Also, since the insulated flights  120  prevent the shell  22  from getting so hot, this design creates a better work environment for anyone who works around the dryer  10 . 
   It will be obvious to those skilled in the art that modifications may be made to the embodiment described above without departing from the scope of the present invention.