Resistance furnace with tubular heating element

1. A resistance furnace comprising: a tubular heating element having a vertically oriented longitudinal axis, said heating element having a shell surface defined by an upper side and a lower side and surrounding a furnace chamber, and being connected to at least two supply terminals by means of which heating current is introduced at power supply points into said heating element, wherein said supply terminals comprise a surrounding upper annular collar adjacent said upper side and a surrounding lower annular collar adjacent said lower side, wherein regions of lower electrical conductivity are formed in said annular collars for branching the supplied heating current into at least four current paths leading to favored power supply points uniformly distributed over a circumference of said heating element, and wherein said power supply points of said upper annular collar are offset circumferentially relative to said power supply points of said lower annular collar.

2. A resistance furnace comprising: a tubular heating element having a vertically oriented longitudinal axis, said heating element having a shell surface defined by an upper side and a lower side and surrounding a furnace chamber, and being connected to at least two supply terminals by means of which heating current is introduced at power supply points into said heating element, wherein said supply terminals comprise a surrounding upper annular collar adjacent said upper side and a surrounding lower annular collar adjacent said lower side, and wherein each of said annular collars comprises an electrode terminal feeding said heating current, and wherein said electrode terminal of said upper annular collar is offset circumferentially relative to said electrode terminal of said lower annular collar.

3. The resistance furnace according to claim 2 , wherein each of said annular collars is provided with at least two electrode terminals uniformly distributed circumferentially around said annular collar.

4. The resistance furnace according to claim 2 wherein regions of lower electrical conductivity are formed in said annular collars for branching the supplied heating current into at least four current paths leading to favored power supply points uniformly distributed over a circumference of said heating element.

5. The resistance furnace according to claim 2 wherein said heating element comprises a heating tube having a wall thickness, said heating tube being extended at both sides by means of at least one contact tube having a front side following a front side of the heating tube and having a greater wall thickness, each of said annular collars being supported on said contact tube.

6. The resistance furnace according to claim 5 , wherein there is provided a clamping means which comprises a plurality of clamping elements by means of which said contact tubes, said heating tube and said annular collars are axially clamped relative to one another.

7. The resistance furnace according to claim 6 , wherein at least four tension rods which are uniformly distributed over a circumference of said heating element are provided as clamping elements.

8. The resistance furnace according to claim 2 wherein regions of lower electrical conductivity are formed in said annular collar for branching the supplied heating current into at least eight current paths leading to favored power supply points uniformly distributed over a circumference of said heating element.

9. The resistance furnace according to claim 2 wherein said annular collars each comprise a connection cone matching a respective conical connection region of said heating element.

10. The resistance furnace according to claim 3 wherein said annular collars each comprise a connection cone matching a respective conical connection region of said heating element.

11. The resistance furnace according to claim 4 wherein said annular collars each comprise a connection cone matching a respective conical connection region of said heating element.

12. The resistance furnace according to claim 2 wherein said annular collars have a first surrounding cooling channel having a first coolant inlet.

13. The resistance furnace according to claim 3 wherein said annular collars have a first surrounding cooling channel having a first coolant inlet.

14. The resistance furnace according to claim 9 , wherein said connection cone is an inner cone and the connection region of said heating element is an outer cone.

15. The resistance furnace according to claim 12 , wherein said annular collars have a second surrounding cooling channel adjacent said first cooling channel and spatially separated therefrom, said second surrounding cooling channel having a second coolant inlet, said second coolant inlet arranged at a side of said annular collar circumferentially opposite said first inlet.

16. The resistance furnace according to claim 2 wherein said heating element is surrounded by a protective jacket of a controllable temperature whose outer wall has detachably secured thereto cooling plates within which a cooling liquid is flowing.

17. A resistance furnace comprising: a tubular heating element having a vertically oriented longitudinal axis, said heating element having a shell surface defined by an upper side and a lower side and surrounding a furnace chamber, and being connected to at least two supply terminals by means of which heating current is introduced at power supply points into said heating element, wherein said supply terminals comprise a surrounding upper annular collar adjacent said upper side and a surrounding lower annular collar adjacent said lower side, and wherein the heating element has an outside and an interior, and the interior of said heating element is sealed to the outside by means of quartz wool.

18. The resistance furnace according to claim 17 , wherein said quartz wool consists of synthetically produced SiO 2 .

19. A resistance furnace comprising: a tubular heating element having a vertically oriented longitudinal axis, said heating element having a shell surface defined by an upper side and a lower side and surrounding a furnace chamber, and being connected to at least two supply terminals by means of which heating current is introduced at power supply points into said heating element, wherein said supply terminals comprise a surrounding upper annular collar adjacent said upper side and a surrounding lower annular collar adjacent said lower side, and wherein gas flushing is provided by a system which comprises a gas inlet which is branched in at least one branch stage, into a plurality of secondary lines of equal pressure loss, said secondary lines terminating in a plurality of gas outlets which are uniformly distributed over an envelope circle and directed into said furnace chamber.

20. The resistance furnace according to claim 19 , wherein said gas outlets are formed in a flush ring which is arranged above said upper annular collar and is composed of at least two separate circular segments, said secondary lines each terminating in one of said circular segments.

21. The resistance furnace according to claim 19 , wherein said gas outlets are formed in a flush ring which is arranged above said upper annular collar and is composed of at least four separate circular segments, said secondary lines each terminating in one of said circular segments.

22. The resistance furnace according to claim 19 wherein said gas inlet is branched in at least three branch stages, into said plurality of secondary lines of equal pressure loss.

23. The resistance furnace according to claim 1 wherein said annular collars each comprise a connection cone matching a respective conical connection region of said heating element.

24. The resistance furnace according to claim 1 wherein said annular collars have a first surrounding cooling channel having a first coolant inlet.

25. The resistance furnace according to claim 2 wherein said annular collars consist of copper or a copper alloy.

26. The resistance furnace according to claim 3 wherein said annular collars consist of copper or a copper alloy.

27. The resistance furnace according to claim 4 wherein said annular collars consist of copper or a copper alloy.

28. The resistance furnace according to claim 1 wherein said annular collars consist of copper or a copper alloy.

29. The resistance furnace according to claim 5 wherein said heating element is surrounded by a protective jacket of a controllable temperature whose outer wall has detachably secured thereto cooling plates within which a cooling liquid is flowing.

30. The resistance furnace according to claim 6 wherein said heating element is surrounded by a protective jacket of a controllable temperature whose outer wall has detachably secured thereto cooling plates within which a cooling liquid is flowing.

31. The resistance furnace according to claim 7 wherein said heating element is surrounded by a protective jacket of a controllable temperature whose outer wall has detachably secured thereto cooling plates within which a cooling liquid is flowing.

32. The resistance furnace according to claim 1 wherein said annular collars have a first surrounding cooling channel having a first coolant inlet.

33. The resistance furnace according to claim 32 , wherein said annular collars have a second surrounding cooling channel adjacent said first cooling channel and spatially separated therefrom, said second surrounding cooling channel having a second coolant inlet, said second coolant inlet arranged at a side of said annular collar circumferentially opposite said first inlet.

34. The resistance furnace according to claim 1 wherein said heating element comprises a heating tube having a wall thickness, said heating tube being extended at both sides by means of at least one contact tube having a front side following a front side of the heating tube and having a greater wall thickness, each of said annular collars being supported on said contact tube.

35. The resistance furnace according to claim 34 , wherein there is provided a clamping means which comprises a plurality of clamping elements by means of which said contact tubes, said heating tube and said annular collars are axially clamped relative to one another.

36. The resistance furnace according to claim 35 , wherein at least four tension rods which are uniformly distributed over a circumference of said heating element are provided as clamping elements.

37. The resistance furnace according to claim 1 wherein said heating element is surrounded by a protective jacket of a controllable temperature whose outer wall has detachably secured thereto cooling plates within which a cooling liquid is flowing.

38. The resistance furnace according to claim 1 wherein regions of lower electrical conductivity are formed in said annular collar for branching the supplied heating current into at least eight current paths leading to favored power supply points uniformly distributed over a circumference of said heating element.

39. The resistance furnace according to claim 17 wherein said heating element comprises a heating tube having a wall thickness, said heating tube being extended at both sides by means of at least one contact tube having a front side following a front side of the heating tube and having a greater wall thickness, each of said annular collars being supported on said contact tube.

40. The resistance furnace according to claim 39 , wherein there is provided a clamping means which comprises a plurality of clamping elements by means of which said contact tubes, said heating tube and said annular collars are axially clamped relative to one another.

41. The resistance furnace according to claim 40 , wherein at least four tension rods which are uniformly distributed over a circumference of said heating element are provided as clamping elements.

42. A resistance furnace comprising: a tubular heating element having a vertically oriented longitudinal axis, said heating element having a shell surface defined by an upper side and a lower side and surrounding a furnace chamber, and being connected to at least two supply terminals by means of which heating current is introduced at power supply points into said heating element, wherein said supply terminals comprise a surrounding upper annular collar adjacent said upper side and a surrounding lower annular collar adjacent said lower side, and wherein regions of lower electrical conductivity are formed in said annular collars for branching the supplied heating current into at least four current paths leading to favored power supply points uniformly distributed over a circumference of said heating element, and wherein said annular collars have a first surrounding cooling channel having a first coolant inlet.