Muffle convection brazing/annealing system

Abstract

A convection muffle furnace for brazing and/or annealing a workpiece includes a muffle having towers formed integrally therewith and being mounted movable relative to a top wall of a furnace. Circulation fans are mounted in the towers so as to move along with the muffle during its expansion and contraction for producing forced convection heat transfer.

What is claimed is: 
     
       1. A convection muffle furnace for brazing and/or annealing a workpiece comprising: a heating chamber formed by a bottom wall, a pair of side walls, a front wall, a rear wall and a top wall;   a .Iadd.D-shaped .Iaddend.muffle formed by side walls, a floor and a roof;   the side walls of said muffle being disposed in a parallel, spaced-apart relationship to said side walls of said heating chamber and extending from the front wall of said heating chamber to the rear wall thereof;   said muffle being divided into a plurality of successive individual convection brazing zones which are spaced apart from each other;   a plurality of towers each being formed integrally with the roof of said muffle in each brazing zone and being mounted movably relative to the top wall of said heating chamber;   a plurality of fans each being mounted and sealed in a corresponding one of said plurality of towers for creating an atmospheric convection current in each of said brazing zones; and   direct-fired burners for heating the exterior of said muffle so as to increase the temperature of the atmospheric convection current;   whereby said plurality of fans in said plurality of towers are movable along with said muffle during its expansion and contraction so as to provide increased heating rates and high thermal efficiencies.   
     
     
       2. A convection muffle furnace as claimed in claim 1, wherein said muffle has its one end adjacent said front wall of the heating chamber being fixed and has its other end adjacent said rear wall thereof being freely movable. 
     
     
       3. A convection muffle furnace as claimed in claim 1, further comprising expansion zone means disposed adjacent the front and rear walls of said heating chamber for permitting longitudinal expansion and contraction of said muffle. 
     
     
       4. A convection muffle furnace as claimed in claim 1, wherein said side walls, floor and roof of said muffle are corrugated so as to impart rigidity thereto. 
     
     
       5. A convection muffle furnace as claimed in claim 1, further comprising expansion cylinder means disposed adjacent the rear wall of the heating chamber so as to maintain a constant tension on said muffle and thereby preventing its deformation. 
     
     
       6. A convection muffle furnace as claimed in claim 1, wherein said towers are mounted in openings formed in said top wall of the heating chamber, said openings being somewhat larger than the diameter of said towers to define spaces which permits lateral movement of said towers relative to said top wall for absorbing expansion and contraction of said muffle. 
     
     
       7. A convection muffle furnace as claimed in claim 6, further comprising sliding seal means disposed over said openings in said top wall to provide a gas-tight seal between said top wall and said towers. 
     
     
       8. A convection muffle furnace as claimed in claim 1, further comprising an entrance chamber disposed upstream of said front wall of the heating chamber for preventing contamination of the atmosphere in said brazing zone as workpieces to be heat-treated are supplied. 
     
     
       9. A convection muffle furnace as claimed in claim 8, further comprising an exit chamber disposed downstream of said rear wall of the heating chamber for preventing contamination of the atmosphere in said brazing zone as the workpieces that have been heat-treated are removed. 
     
     
       10. A convection muffle furnace for brazing and/or annealing a workpiece comprising: a heating chamber formed by a bottom wall, a pair of side walls, a front wall, .Iadd.a .Iaddend.rear wall and a top wall;   muffle means disposed inside of said heating chamber and extending longitudinally from the front wall of said heating chamber to the rear wall thereof.Iadd., said muffle means comprising a D-shaped muffle having planar side walls parallel to the side walls of the heating chamber, a planar floor connected to the planar side walls and a dome-shaped roof positioned above and connected to the planar side walls;.Iaddend.   said muffle means including tower means formed integrally therewith and being mounted movably relative to the top wall of said heating chamber;   circulating means being mounted and sealed in said tower means for creating an atmospheric convection current; and   direct-fired burners for heating the exterior of said muffle means so as to increase the temperature of the atmospheric convection current,   whereby said circulating means in said tower means are movable along with said muffle means during its expansion and contraction so as to provide increased heating rates and high thermal efficiencies.   
     
     
       11. A convection muffle furnace as claimed in claim 10, wherein said muffle means has its one end adjacent said front wall of the heating chamber being fixed and has its other end adjacent said rear wall thereof being freely movable. 
     
     
       12. A convection muffle furnace as claimed in claim 10, further comprising expansion zone means disposed adjacent the front and rear walls of said heating chamber for permitting longitudinal expansion and contraction of said muffle means. 
     
     
       13. A convection muffle furnace as claimed in claim 10, wherein said muffle means .[.includes side walls, a floor and a roof which.]. are corrugated so as to impart rigidity thereto. 
     
     
       14. A convection muffle furnace as claimed in claim 10, further comprising expansion cylinder means disposed adjacent the rear wall of the heating chamber so as to maintain a constant tension on said muffle means and thereby preventing its deformation. 
     
     
       15. A convection muffle furnace as claimed in claim 10, wherein said tower means are mounted in openings formed in said top wall of the heating chamber, said openings being somewhat larger than the diameter of said tower means to define spaces which permits lateral movement of said tower means relative to said top wall for absorbing expansion and contraction of said muffle .Iadd.means.Iaddend.. 
     
     
       16. A convection muffle furnace as claimed in claim 15, further comprising sliding seal means disposed over said openings in said top wall to provide a gas-tight seal between said top wall and said towers. 
     
     
       17. A convection muffle furnace as claimed in claim 10, further comprising an entrance chamber disposed upstream of said front wall of the heating chamber for preventing contamination of the atmosphere in said muffle means as workpieces to be heat-treated are supplied. 
     
     
       18. A convection muffle furnace as claimed in claim 17, further comprising an exit chamber disposed downstream of said rear wall of the heating chamber for preventing contamination of the atmosphere in said muffle means as the workpieces that have been heat-treated are removed. 
     
     
       19. A convection muffle furnace for brazing and/or annealing a workpiece comprising: a heating chamber formed by a bottom wall, a pair of side walls, a front wall, a rear wall and a top wall;   a .Iadd.D-shaped muffle having planar side walls parallel to the side walls of the heating chamber, a planar floor connected to the planar side walls and a dome-shaped roof positioned above and connected to the planar side walls, said .Iaddend.muffle having at least one tower formed integrally therewith which is mounted movably relative to the top wall of said heating chamber; and   a circulating fan being mounted in said at least one tower so as to move along with said muffle during its expansion and contraction. .Iadd.   
     
     
       20.  A convection muffle furnace for brazing and/or annealing a workpiece, comprising: a heating chamber formed by a bottom wall, a pair of side walls, a front wall, a rear wall and a top wall;   D-shaped muffle means disposed inside of said heating chamber and extending longitudinally from the front wall of said heating chamber to the rear wall thereof;   said muffle means including tower means formed integrally therewith and being mounted movably relative to the top wall of said heating chamber;   a first thermocouple positioned within the muffle means and a second thermocouple positioned outside the muffle means and within the heating chamber, said first and second thermocouples providing temperature signals;   circulating means being mounted and sealed in said tower means for creating an atmospheric convection current; and   direct-fired burners for heating the exterior of said muffle means so as to increase the temperature of the atmospheric convection current,   whereby said circulating means in said tower means are movable along with said muffle means during its expansion and contraction so as to provide increased heating rates and high thermal efficiencies..Iaddend..Iadd.   
     
     
       21.  A convection muffle furnace for brazing and/or annealing a workpiece comprising: a heating chamber formed by a bottom wall, a pair of side walls, a front wall, a rear wall and a top wall;   a D-shaped muffle having at least one tower formed integrally therewith which is mounted movably relative to the top wall of said heating chamber;   a first thermocouple positioned within the muffle and a second thermocouple positioned outside the muffle means and within the heating chamber, said first and second thermocouples providing temperature signals; and   a circulating fan being mounted in said at least one tower so as to move along with said muffle during its expansion and contraction..Iaddend.