ELECTRICAL TUBULAR HEATING ELEMENT WITH CONNECTING PIN AND MANUFACTURING METHOD FOR ELECTRICAL TUBULAR HEATING ELEMENT WITH CONNECTING PIN

Abstract

An electrical tubular heating element is disclosed with a tubular metal sheath, in whose interior at least one electrical heating element, which is constructed as a resistive wire, arranged electrically insulated from the tubular metal sheath at least in sections, in which the electrical heating element has a base body, which consists of one or more sections of the electrical heating element each with essentially constant cross section, and two end sections and that at least one end section of at least one of the electrical heating elements is subjected to a shape-changing process, so that the cross section of the end section is reduced at least in sub-areas of the end section in comparison to the cross section in each section of the base body. A method for manufacturing such an electrical tubular heating element is also disclosed.

Claims

1-19. (canceled)

20. An electrical tubular heating element for providing electric heat, the electrical tubular heating element comprising: a tubular metal sheath having an interior; an electrical heating element positioned within the interior, the electrical heating element constructed of a resistive wire, the electrical heating element arranged electrically insulated at least in sections from the tubular metal sheath, the electrical heating element having a base body, the base body comprised of one or more sections of the electrical heating element, each of the one or more sections of the electrical heating element having an essentially constant cross section and two end sections including a first end section and a second end section, the first end section being subjected to a shape-changing machining process so that a cross section of the first end section at least in sub-areas of the first end section is reduced in comparison to the essentially constant cross section of the base body.

21. The electrical tubular heating element according to claim 20, wherein at least one of a connecting wire and a connecting pin is in electrically conductive connection with one of the first and second end sections within the tubular metal sheath.

22. The electrical tubular heating element according to claim 21, wherein the electrically conductive connection with one of the first and second end sections is realized via an end section of the at least one of the connecting wire and the connecting pin, the end section of the at least one of the connecting wire and the connecting pin is subjected to a shape-changing machining process such that the end section of the at least one of the connecting wire and the connecting pin has a complementary shape to a shape of the first end section to which the end section of the at least one of the connecting wire and the connecting pin is connected.

23. The electrical tubular heating element according to claim 21, wherein the base body and the at least one of the connecting wire and the connecting pin, is electrically insulated from the tubular metal sheath by an electrical insulation, the electrical insulation comprised of one of a magnesium oxide powder, a magnesium oxide granulate, and pushed-on ceramic tubes.

24. The electrical tubular heating element according to claim 23, wherein the electrical insulation is distributed across an entire inner surface of the tubular metal sheath by a single pushed-on ceramic tube.

25. The electrical tubular heating element according to claim 21, wherein the at least one of the connecting wire and the connecting pin has a base body, the base body of the at least one of the connecting wire and the connecting pin having a cross section that corresponds at least in one section to the cross section of the first end section.

26. The electrical tubular heating element according to claim 25, wherein an outer periphery of a cross section of an assembly formed by the electrical heating element and the at least one of the connecting wires and the connecting pin is constant over an entire area of the assembly, which is arranged within the tubular metal sheath.

27. The electrical tubular heating element according to claim 21, wherein the cross section of the first end section of the electrical heating element tapers in a direction toward an end of the electrical heating element in one of steps and continuously.

28. The electrical tubular heating element according to claim 20, wherein the first end section of the electrical heating element is formed by a projection at an end-side end surface of the base body of the electrical heating element.

29. The electrical tubular heating element according to claim 28, wherein the projection has one of an undercut and a thread.

30. The electrical tubular heating element according to claim 20, wherein an outer contour of the first and second end sections of the electrical heating element correspond to an outer contour of a section of the base body of the electrical heating element, the first end section having one of a recess and an opening that starts from an end-side end of the electrical heating element.

31. The electrical tubular heating element according to claim 30, wherein the one of the recess and the opening has one of an undercut and a thread.

32. The electrical tubular heating element according to claim 21, wherein the electrical heating element is connected with the at least one of the connecting wire and the connecting pin, the electrical heating element is arranged in the interior of the tubular metal sheath and the one or more sections of the electrical heating element are electrically insulated relative to the tubular metal sheath, the first end section is subjected to a shape-changing machining process so that a cross section of the first end section at least in sub-areas of the first end section is reduced in comparison to the essentially constant cross section of the base body.

33. The electrical tubular heating element according to claim 32, wherein before connecting the electrical heating element with the at least one of the connecting wire and the connecting pin at least one end section of the at least one of the connecting wire and the connecting pin is subjected to shape-changing machining complementary to the shape-changing machining process of the first end section.

34. The electrical tubular heating element according to claim 32, wherein the electrical heating element is arranged together with the at least one of the connecting wire and the connecting pin in the interior of the tubular metal sheath.

35. The electrical tubular heating element according to claim 20, wherein the electrical heating element is electrically insulated from the tubular metal sheath by filling the interior with one of a powdered magnesium oxide, a granulate magnesium oxide and a ceramic tube pushed into the interior.

36. The electrical tubular heating element according to claim 21, wherein the electrical heating element is electrically insulated from the tubular metal sheath together with sections of the at least one of the connecting wire and the connecting pin by a single ceramic tube is pushed into the interior.

37. The electrical tubular heating element according to claim 20, wherein the shape-changing machining is performed by one of metal cutting, pressing, and hammering.

38. The electrical tubular heating element according to claim 20, wherein the electrical tubular heating element is compacted one of completely and in sections.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0037] The foregoing summary, as well as the following detailed description of the preferred invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the preferred invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[0038] FIG. 1a is a side elevational, partial cross-sectional view of a first embodiment of an electrical tubular heating element in accordance with the preferred invention;

[0039] FIG. 1b is a detail cross-sectional view of a first detail of the electrical tubular heating element from FIG. 1a, taken from within circle A of FIG. 1a;

[0040] FIG. 1c is a detail cross-sectional view of a second detail of the electrical tubular heating element from FIG. 1a, taken from within circle B of FIG. 1a before and after the compacting process;

[0041] FIG. 2 is a side elevational, partial cross-sectional view of a second embodiment of an electrical tubular heating element in accordance with the preferred invention;

[0042] FIG. 3a is a side perspective, fragmentary schematic view of a first step for connecting an electrical heating element and a connecting wire according to a first preferred procedure;

[0043] FIG. 3b is a side elevational, fragmentary schematic view of a second step for connecting the electrical heating element and the connecting wire according to the first procedure of FIG. 3a;

[0044] FIG. 3c is a side elevational, fragmentary schematic view of a third step for connecting the electrical heating element and the connecting wire according to the first procedure of FIG. 3a;

[0045] FIG. 4a is a side perspective, fragmentary schematic view of a first step for connecting an electrical heating element and a connecting wire according to a second preferred procedure;

[0046] FIG. 4b is a cross-sectional view of the step from FIG. 4a, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 4a;

[0047] FIG. 4c is a cross-sectional view of a second step for connecting the electrical heating element and the connecting wire according to the second procedure, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 4a;

[0048] FIG. 4d is a cross-sectional view of a third step for connecting the electrical heating element and the connecting wire according to the second procedure, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 4a;

[0049] FIG. 5a is a side perspective, fragmentary schematic view of a first step for connecting an electrical heating element and a connecting wire according to a third preferred procedure;

[0050] FIG. 5b is a cross-sectional view of the step from FIG. 5a, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 5a;

[0051] FIG. 5c is a cross-sectional view of a second step for connecting the electrical heating element and the connecting wire according to the third procedure, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 5a;

[0052] FIG. 6a is a side perspective, fragmentary schematic view of a first step for connecting an electrical heating element and a connecting wire according to a fourth preferred procedure;

[0053] FIG. 6b is a side elevational view of the step from FIG. 6a;

[0054] FIG. 6c is a side elevational view of a second step for connecting the electrical heating element and the connecting wire according to the fourth procedure of FIG. 6a;

[0055] FIG. 7a is a side perspective, fragmentary schematic view of a first step for connecting an electrical heating element and a connecting wire according to a fifth preferred procedure;

[0056] FIG. 7b is a cross-sectional view of the step from FIG. 7a, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 7a

[0057] FIG. 7c is a cross-sectional view of a second step for connecting the electrical heating element and the connecting wire according to the fifth procedure, taken generally along a longitudinal axis of the electrical heating element and connecting wire of FIG. 7a;

[0058] FIG. 8a is a side elevational first schematic view of a first way to modify a cross section of the electrical heating element of the preferred embodiments;

[0059] FIG. 8b is a front elevational, second schematic view of the first way to modify the cross section of the electrical heating element from FIG. 8a;

[0060] FIG. 8c is a side elevational, third schematic view of the first way to modify the cross section of the electrical heating element from FIG. 8a;

[0061] FIG. 8d is a side elevational schematic view of a second way to modify the cross section of the electrical heating element from FIG. 8a; and

[0062] FIG. 8e is a side elevational schematic view of a third way to modify the cross section of the electrical heating element from FIG. 8a.

DETAILED DESCRIPTION OF THE INVENTION

[0063] FIG. 1a shows an electrical tubular heating element 10 with tubular metal sheath 11 and electrical heating element 12. The electrical heating element 12 is constructed as a linear, elongated resistive wire, which runs concentric to the tube axis within the tubular metal sheath 11.

[0064] The electrical heating element 12 has two end sections 12a, 12b, which are shown enlarged in the detail views of details A and B according to FIG. 1b and FIG. 1c, respectively, and a base body 12c with essentially constant cross section. Especially in cases in which an electrical tubular heating element is compacted to very different degrees in different sections, the different compacting can lead to different changes of the electrical heating element, which then leads to a base body with multiple sections corresponding to the zones of different compaction with essentially constant cross section.

[0065] As the detail A shown in FIG. 1b illustrates, the end section 12a is welded with an electrically conductive ring 13, which is welded on its side with the tubular metal sheath 11. Accordingly, there is here an electrical connection between the end section 12a of the electrical heating element 12 and the tubular metal sheath 11; the tubular metal sheath 11 is used as a return line.

[0066] As the detail B shown in FIG. 1c before and after the compacting of the electrical tubular heating element 10 illustrates, the end section 12b of the electrical heating element 12 is, in contrast, subjected to a shape-changing machining process, so that its cross section is reduced, namely stepped. The stepped end section 12b of the electrical heating element 12 engages in a complementary stepped recess 15 that starts from the end side of the connecting wire or connecting pin 14 facing the heating element 12 and that is arranged in its end section 14a, so that there is an electrical and mechanical contact between the electrical heating element 12 and the connecting wire or connecting pin 14. At the same time, the outer contours of the electrical heating element 12 and the connecting wire or connecting pin 14 are adapted to each other so that their outer surfaces abut flush against each other. Furthermore, a section of the connecting pin 14 or its base body 14b emerges from the tubular metal sheath 11.

[0067] The sections of the electrical heating element 12 located within the tubular metal sheath 11, with the exception of the end section 12a and the connecting pin 14, are electrically insulated from the tubular metal sheath 11 by a single ceramic tube 16.

[0068] The manufacture of the electrical tubular heating element 10 is to be performed in an extremely simple way. The end section 12b of the electrical heating element 12 is subjected to a shape-changing machining process, for example, turned, in order to generate the stepped contour. The connecting pin 14 is drilled in its end section 14a on its end side, in order to form the complementary recess 15.

[0069] Then the ring 13 can be placed on the end section 12a, the end section 12b can be inserted into the complementary recess 15, and the assembly formed in this way—optionally after welding or soldering the components to each other—can be inserted into the tubular metal sheath 11. Then the ring 13 is welded with the tubular metal sheath 11 and the ceramic tube 16 is pushed on, before the electrical tubular heating element 10 is completed by compacting. It should still be noted that if one wants to eliminate the welding or soldering, a compacting process can already produce a usable press contact.

[0070] The electrical tubular heating element 20 shown in FIG. 2 has a tubular metal sheath 21 and an electrical heating element 22 with end sections 22a, 22b, which are both subjected to shape-changing machining processes in this example analogous to the end section 12b of the electrical heating element 12 of the electrical tubular heating element 10, so that their cross sections are each reduced by steps at the ends of the electrical heating element. Here, two connecting wires or connecting pins 23, 24 are now present, which have end sections 23a, 24a that are provided with recesses 25, 27 in a way analogous to connecting pin 14 or its end section 14a with shape-changing machining. The complete electrical insulation of the assembly consisting of the electrical heating element 22 and connecting pin 23, 24 relative to the tubular metal sheath 21 in this embodiment is guaranteed by a single ceramic tube 26.

[0071] For the manufacturing of the connection between an electrical heating element 30 and a connecting wire or connecting pin 35, whose base bodies 31, 36 have the same cross section, shown in FIGS. 3a to 3c, as can be seen particularly well in FIG. 3a, the end section 30a of the electrical heating element 30 and the end section 35a of the connecting wire or connecting pin 35 are each angled at the same cut angle in the same cutting direction. Accordingly, in these end sections 30a, 35a the cross sections are each reduced in comparison to the respective base body by shape-changing machining.

[0072] The contact surfaces 32, 37 generated in this way can then be placed one above the other in a precisely fitting way, as FIG. 3b shows, and are welded with each other, as can be seen in FIG. 3c. It can be seen immediately that through this procedure, the contact surface is increased significantly in comparison to an abutting, end-side contact, which considerably reduces the relevance of any local contact problems.

[0073] For the manufacturing of the connection between an electrical heating element 40 and a connecting wire or connecting pin 45, whose base bodies 41, 46 have the same cross section, shown in FIGS. 4a to 4d, as can be seen particularly well in FIGS. 4a and 4b, the end section 40a of the electrical heating element 40 is constructed stepped by radial removal of material of the resistive wire, while the end section 45a of the connecting wire or connecting pin 45 has a complementary stepped recess 47, which starts from the end side of the connecting wire or connecting pin 45. Accordingly, the cross sections are reduced in comparison to the cross section of the base body 41, 46 by shape-changing machining also in the end sections 40a, 45a.

[0074] Accordingly, the end section 40a of the electrical heating element 40 can be inserted into the recess 47 of the connecting wire or connecting pin 45, as shown in FIG. 4c, and can then be guaranteed by compacting the electrical contact, as shown in FIG. 4d.

[0075] Of course, such an arrangement can also be realized with the roles swapped, i.e., a stepped recess extending into an electrical heating element and starting from an end side of this electrical heating element for receiving a complementary stepped end section of the connecting wire or connecting pin. The selection of one of these alternatives can be motivated, for example, by the materials actually being used and their behavior during machining.

[0076] For the manufacturing of the connection between an electrical heating element 50 and a connecting wire or connecting pin 55, whose base bodies 51, 56 have the same cross section, shown in FIGS. 5a to 5c, as can be seen particularly well in FIGS. 5a and 5b, the end section 50a of the electrical heating element 50 is constructed tapering conically by radial removal of material of the resistive wire, while the end section 55a of the connecting wire or connecting pin 55 has a complementary conically tapering recess 57, which starts from the end side of the connecting wire or connecting pin 55. Accordingly, the cross sections are reduced in comparison to the cross section of the base body 51, 56 by shape-changing machining also in the end sections 50a, 55a.

[0077] Accordingly, the end section 50a of the electrical heating element 50 can be inserted into the recess 57 of the connecting wire or connecting pin 55, as shown in FIG. 5c, and then guaranteed, for example, by compacting the electrical contact.

[0078] Of course, this arrangement can also be realized with the roles of electrical heating element on one side and connecting wire or connecting pin on the other side reversed.

[0079] For the manufacturing of the connection between an electrical heating element 60 and a connecting wire or connecting pin 65, whose base bodies 61, 66 have the same cross section, shown in FIGS. 6a to 6c, as can be seen particularly well in FIGS. 6a and 6b, the end section 60a of the electrical heating element 60 is shaped by removal of material of the resistive wire into a projection 62, which also has, in this example, an undercut. The end section 65a of the connecting wire or connecting pin 65 has a complementary constructed groove 67, which starts from the end side of the connecting wire or connecting pin 55.

[0080] Accordingly, the end section 60a of the electrical heating element 60 or its projection 62 can be inserted into the groove 67 of the connecting wire or connecting pin 65, as shown in FIG. 6c.

[0081] Of course, this arrangement can also be realized with the roles of electrical heating element on one side and connecting wire or connecting pin on the other side reversed.

[0082] For the manufacturing of the connection between an electrical heating element 70 and a connecting wire or connecting pin 75, whose base bodies 71, 76 have the same cross section, shown in FIGS. 7a to 7c, as can be seen particularly well in FIGS. 7a and 7b, the end section 70a of the electrical heating element 70 is constructed by removal of material of the resistive wire to form a cylindrical projection 72, in which a thread is formed. The end section 75a of the connecting wire or connecting pin 75 has a complementary constructed hole 77, which starts from the end side of the connecting wire or connecting pin 65, and in which a matching counter-thread is cut.

[0083] Accordingly, the end section 70a of the electrical heating element 70 or its projection 72 can be screwed into the hole 77 of the connecting wire or connecting pin 75, as shown in FIG. 6c. Also for this connection, the roles of electrical heating element 70 and connecting wire or connecting pin 75 can be reversed.

[0084] FIGS. 8a to 8e show three different procedures for the shape-changing machining of an end section 80a of an electrical heating element 80, which is formed by a heating element that, however, can be used in the same way on connecting wires or connecting pins.

[0085] FIGS. 8a to 8c show, as a first variant, the hammering of a specified profile. In FIG. 8a, the hammering dies 81 are shown opened up in cross section, before the electrical heating element 80 is inserted. In FIG. 8b, the arrangement of the hammering dies 81 and inserted electrical heating element 80 is shown from above. In FIG. 8c, the state of this arrangement during the hammering process can be seen.

[0086] FIG. 8d illustrates the metal-cutting machining of the electrical heating element 80 or of its end section 80a by turning with a turning tool 82 shown schematically; FIG. 8e illustrates the metal-cutting machining of the electrical heating element 80 or its end section 80a by turning with a milling tool 83 shown schematically.

[0087] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

LIST OF REFERENCE SYMBOLS

[0088] 10, 20 Tubular heating element [0089] 11, 21 Metal sheath [0090] 12, 22, 30, 40, 50, 60, 70, [0091] 80 Electrical heating element [0092] 12a, 12b, 22a, 22b, 30a, [0093] 40a, 50a, 60a, 70a, 80a End section [0094] 12c, 22c, 31, 36, 41, 46, [0095] 51, 56, 61, 66, 71, 76 Base body [0096] 13 Ring [0097] 14, 23, 24, 35, 45, 55, 65, [0098] 75, 85 Connecting wire or connecting pin [0099] 14a, 23a, 24a, 35a, 45a, [0100] 55a, 65a, 75a End section [0101] 15, 25, 27, 47, 57 Recess [0102] 16, 26 Ceramic tube [0103] 32, 37 Contact surface [0104] 62, 72 Projection [0105] 67 Groove [0106] 77 Hole [0107] 81 Hammering die [0108] 82 Turning tool [0109] 83 Milling tool