WO1991011892A1 - Electric tubular heating element and method for making the same - Google Patents

Electric tubular heating element and method for making the same Download PDF

Info

Publication number
WO1991011892A1
WO1991011892A1 PCT/SE1991/000045 SE9100045W WO9111892A1 WO 1991011892 A1 WO1991011892 A1 WO 1991011892A1 SE 9100045 W SE9100045 W SE 9100045W WO 9111892 A1 WO9111892 A1 WO 9111892A1
Authority
WO
WIPO (PCT)
Prior art keywords
sheath tube
corrugation
heating element
tubular heating
wall thickness
Prior art date
Application number
PCT/SE1991/000045
Other languages
French (fr)
Inventor
Kjell-Åke ELOFSSON
Lennart Hedman
Original Assignee
Backer Elektro-Värme Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Backer Elektro-Värme Ab filed Critical Backer Elektro-Värme Ab
Publication of WO1991011892A1 publication Critical patent/WO1991011892A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H05B3/50—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material heating conductor arranged in metal tubes, the radiating surface having heat-conducting fins
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H05B3/52—Apparatus or processes for filling or compressing insulating material in tubes

Definitions

  • the present invention relates to an electrically- operated tubular heating element comprising a metal sheath tube filled with an e.g. pulverulent insulating material, and at least one helical resistance wire embedded in said insulating material.
  • the invention also concerns a method for making such a heating element, comprising the steps of arranging at least one helical resistance wire in a metal sheath tube, and filling said tube with a pulverulent insulating mate ⁇ rial.
  • the necessary compression of the in ⁇ sulating material is carried out by rolling or hammering.
  • the main disadvantages of these techniques is that the sheath tube is made longer, which makes it difficult to keep given tolerances, in particular as to length; that local variations in degree of filling result in varying compression and, consequently, varying thermal conductivi ⁇ ty from the resistance wire to the sheath tube; and that a subsequent bending of the tubular heating element may loosen the insulating material locally, thus reducing thermal conductivity and electric insulating power.
  • tubular heating elements produced by these conventional methods have a limited heat emission surface, which either reduces the effect emitted or necessitates much-to-large outer dimensions.
  • the changes of temperature occurring during an operating cycle, as well as the ensuing alteration of length, may further lead to such stress on the resistance wire that its oxide layer cracks, resulting in a much shorter service life of the tubular heating element.
  • the sheath tube must have a comparatively thick wall, which is particularly disadvantageous in sheath tubes of rather expensive materials, such as stainless steel.
  • the object of the invention is, therefore, to provide a tubular heating element, and a method for making the same, obviating or at least reducing these disadvantages of conventional tubular heating elements.
  • this object is achieved by an electrically-operated tubular heating element of the type stated in the introduction to this specification, and characterised in that the sheath tube presents transverse corrugations having a width substantially exceeding the wall thickness of said sheath tube, the transverse corru ⁇ gations imparting the necessary compression to the pul ⁇ verulent insulating material.
  • the corrugations further have a depth substantially exceeding the wall thickness of said sheath tube.
  • the invention it is possible to greatly mini ⁇ mise lengthening of the sheath tube upon compression of the insulating material. Also, local variations in the degree of filling of the insulating material can, with the invention, be equalised in an advantageous fashion. Further, the invention simplifies a subsequent bending of the tubular heating element without any risk of local loosening of the insulating material.
  • the invention substan ⁇ tially enlarges the heat emission surface.
  • the stress on the resistance wire caused by the changes of temperature occurring during an operating cycle will be considerably reduced as a result of the ability of the transverse corrugations to take up alterations of length.
  • the transverse corrugations give a considerable increase of the mechanical strength so that the wall thickness of the sheath tube may be reduced, which means an important saving of material.
  • the improved compression resulting from the transverse corrugation and the reduced wall thickness improves the thermal dissipation through the insulating material and increases the electric strength thereof, and consequently of the entire tubular heating element.
  • the corrugation width is more than three times, preferably more than five times, and most preferably more than ten times, as large as the wall thickness of said sheath tube, while the corrugation depth suitably is approximately half as large as the corrugation width.
  • the tube wall thickness may be made less than 0.4 mm, pre ⁇ ferably less than 0.3 mm.
  • the above-mentioned objects are achieved by a method for making an electri ⁇ cally-operated tubular heating element of the type men ⁇ tioned in the introduction to this specification, in which method the necessary compression of the pulverulent in- sulating material is achieved by transversely corrugating said sheath tube, the corrugation width substantially exceeding the wall thickness of said sheath tube.
  • the transverse corrugations are given a depth substantially exceeding the wall thickness of said sheath tube.
  • the maximum effect of the transverse corrugation is obtained by making the largest outside diameter of the sheath tube after corrugation approximately equal to the tube outside diameter before said corrugation. Further, the transverse corrugation may be carried out by roll threading.
  • FIG. 1 shows a longitudinal section of a tubular heating element before compression
  • Fig. 2 is a side view of the tubular heating element in Fig. 1 after the inventive compression
  • Fig. 3 shows an enlarged longitudinal section of part of the tubular heating element in Fig. 2.
  • the tubular heating element shown in Fig. 1 comprises a sheath tube 1 which is filled with a pulverulent insula ⁇ ting material 2, e.g. magnesium oxide.
  • a pulverulent insula ⁇ ting material e.g. magnesium oxide.
  • a helical resistance wire 3 is embedded in the pulverulent insulating material 2.
  • the ends of the wire 3 are interconnected by terminals 4, 5 extending axially beyond the ends of the sheath tube 1 and mounted at these ends by means of bushings 6, 7.
  • the tubular heating element has the appearance shown in Fig. 2 and, in more detail, in Fig. 3.
  • transverse corrugations 8 having a width B and a depth D which substantially exceed the wall thickness of the sheath tube 1.
  • the corrugation width B is made more than three times, pre- ferably more than five times, and most preferably more than ten times, as large as the wall thickness of the sheath tube 1, more precisely the average thickness of the tube wall after corrugation.
  • the corrugation depth D is made approximately half as large as the corrugation width B.
  • the transverse corrugation can be achieved with such tools as are used for pressure or rolling threading, and it suitably has the form of a threading, even if peri ⁇ pheral, self-contained corrugations are conceivable.
  • the largest outside diameter of the sheath tube 1 after transverse corrugation should be approximate ⁇ ly equal to the tube outside diameter before transverse corrugation is carried out, thereby achieving maximum compression as well as optimum control of the shape of the transverse corrugations.
  • a degree of compression of the insulating material amounting to 75% is quite easily attained, the degree of compression being defined as the ratio of the volume enclosed by the sheath tube after compression, to the volume enclosed by the tube before compression.
  • transverse corrugation according to the invention also substantially enlarges the circumferential surface of the sheath tube 1. It is, for instance, possible to achieve a surface enlargement in the order of 40%.
  • the invention makes it possible to save as much material as about 50%.
  • a sheath tube of stainless steel having a wall thickness of 0.25 mm and a diameter of 10 mm obtained, after compression according to the invention by forming threaded transverse corruga ⁇ tions, an average wall thickness of 0.18 mm, the corruga ⁇ tion width B being about 2.5 mm and the corrugation depth being about 1.2 mm.
  • the inventive transverse corrugation of the sheath tube is the only measure used for compressing the pulverulent insulating material, which considerably facilitates the making of tubular heating elements.
  • the inventive transverse corrugation of the sheath tube greatly facilitates a subsequent bending, if any, of the tubular heating element, since the corrugated tube then acts in the manner of a bellows.
  • the alteration of the total length of the tubular heating element may be completely, or at least substantially, eliminated. This is highly advantageous by making it possible to keep given tolerances, in particular as to the length of the tubular heating element.
  • the considerable surface enlargement results in an improved heat emissive power enabling a reduction of the dimensions of the heating element when the surface temperature is maintained, or an increase of the total effect emitted. If the total effect is maintained, a saving of material is possible.
  • the tubular heating element according to the inven ⁇ tion is suited for heating gaseous, liquid as well as solid media. If, in the latter case, the transverse corrugation is threaded and the tubular heating element is straight, the heating element is simply screwed into a threaded hole of the member to be heated.
  • the inventive transverse corrugation is also advantageous when the tubular heating element is to be embedded, since it substantially reduces relative movements between the heating element and the member in which it is embedded.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)

Abstract

An electrically-operated tubular heating element comprises a metal sheath tube (1) filled with an e.g. pulverulent insulating material (2), and at least one helical resistance wire (3) embedded in the insulating material. The sheath tube (1) presents transverse corrugations (8) having a width (B) substantially exceeding the wall thickness of the sheath tube, the transverse corrugations haivng achieved the necessary compression of the pulverulent insulating material. In a method for making such an electrically-operated tubular heating element, the necessary compression of the pulverulent insulating material (2) is achieved by transversely corrugating the sheath tube (1), the corrugation width (B) substantially exceeding the wall thickness of the sheath tube.

Description

ELECTRIC TUBULAR HEATING ELEMENT AND METHOD FOR MAKING THE SAME.
The present invention relates to an electrically- operated tubular heating element comprising a metal sheath tube filled with an e.g. pulverulent insulating material, and at least one helical resistance wire embedded in said insulating material. The invention also concerns a method for making such a heating element, comprising the steps of arranging at least one helical resistance wire in a metal sheath tube, and filling said tube with a pulverulent insulating mate¬ rial. Conventionally, the necessary compression of the in¬ sulating material is carried out by rolling or hammering. The main disadvantages of these techniques is that the sheath tube is made longer, which makes it difficult to keep given tolerances, in particular as to length; that local variations in degree of filling result in varying compression and, consequently, varying thermal conductivi¬ ty from the resistance wire to the sheath tube; and that a subsequent bending of the tubular heating element may loosen the insulating material locally, thus reducing thermal conductivity and electric insulating power.
Moreover, the tubular heating elements produced by these conventional methods have a limited heat emission surface, which either reduces the effect emitted or necessitates much-to-large outer dimensions. The changes of temperature occurring during an operating cycle, as well as the ensuing alteration of length, may further lead to such stress on the resistance wire that its oxide layer cracks, resulting in a much shorter service life of the tubular heating element. To obtain the requisite mechani- cal strength, the sheath tube must have a comparatively thick wall, which is particularly disadvantageous in sheath tubes of rather expensive materials, such as stainless steel. SUBSTITUTE SHEE The object of the invention is, therefore, to provide a tubular heating element, and a method for making the same, obviating or at least reducing these disadvantages of conventional tubular heating elements. According to the invention, this object is achieved by an electrically-operated tubular heating element of the type stated in the introduction to this specification, and characterised in that the sheath tube presents transverse corrugations having a width substantially exceeding the wall thickness of said sheath tube, the transverse corru¬ gations imparting the necessary compression to the pul¬ verulent insulating material. Suitably, the corrugations further have a depth substantially exceeding the wall thickness of said sheath tube. With the invention, it is possible to greatly mini¬ mise lengthening of the sheath tube upon compression of the insulating material. Also, local variations in the degree of filling of the insulating material can, with the invention, be equalised in an advantageous fashion. Further, the invention simplifies a subsequent bending of the tubular heating element without any risk of local loosening of the insulating material.
Compared with the prior art, the invention substan¬ tially enlarges the heat emission surface. The stress on the resistance wire caused by the changes of temperature occurring during an operating cycle will be considerably reduced as a result of the ability of the transverse corrugations to take up alterations of length. Further, the transverse corrugations give a considerable increase of the mechanical strength so that the wall thickness of the sheath tube may be reduced, which means an important saving of material. Finally, the improved compression resulting from the transverse corrugation and the reduced wall thickness improves the thermal dissipation through the insulating material and increases the electric strength thereof, and consequently of the entire tubular heating element. In a preferred embodiment, the corrugation width is more than three times, preferably more than five times, and most preferably more than ten times, as large as the wall thickness of said sheath tube, while the corrugation depth suitably is approximately half as large as the corrugation width.
When the sheath tube is made of stainless steel, the tube wall thickness may be made less than 0.4 mm, pre¬ ferably less than 0.3 mm. According to the invention, the above-mentioned objects are achieved by a method for making an electri¬ cally-operated tubular heating element of the type men¬ tioned in the introduction to this specification, in which method the necessary compression of the pulverulent in- sulating material is achieved by transversely corrugating said sheath tube, the corrugation width substantially exceeding the wall thickness of said sheath tube. Suitably, the transverse corrugations are given a depth substantially exceeding the wall thickness of said sheath tube.
The maximum effect of the transverse corrugation is obtained by making the largest outside diameter of the sheath tube after corrugation approximately equal to the tube outside diameter before said corrugation. Further, the transverse corrugation may be carried out by roll threading.
The invention will now be described in more detail below, reference being had to the accompanying drawings, in which Fig. 1 shows a longitudinal section of a tubular heating element before compression,
Fig. 2 is a side view of the tubular heating element in Fig. 1 after the inventive compression, and
Fig. 3 shows an enlarged longitudinal section of part of the tubular heating element in Fig. 2. The tubular heating element shown in Fig. 1 comprises a sheath tube 1 which is filled with a pulverulent insula¬ ting material 2, e.g. magnesium oxide. In the centre of the sheath tube 1, a helical resistance wire 3 is embedded in the pulverulent insulating material 2. The ends of the wire 3 are interconnected by terminals 4, 5 extending axially beyond the ends of the sheath tube 1 and mounted at these ends by means of bushings 6, 7.
In Fig. 1, no compression of the pulverulent insulat- ing material has yet taken place, and the tubular heat¬ ing element therefore is of essentially conventional appearance.
After compression in accordance with the invention, the tubular heating element has the appearance shown in Fig. 2 and, in more detail, in Fig. 3. According to the invention, there are formed transverse corrugations 8 having a width B and a depth D which substantially exceed the wall thickness of the sheath tube 1. Preferably, the corrugation width B is made more than three times, pre- ferably more than five times, and most preferably more than ten times, as large as the wall thickness of the sheath tube 1, more precisely the average thickness of the tube wall after corrugation. In a preferred embodiment, the corrugation depth D is made approximately half as large as the corrugation width B.
The transverse corrugation can be achieved with such tools as are used for pressure or rolling threading, and it suitably has the form of a threading, even if peri¬ pheral, self-contained corrugations are conceivable. Suitably, the largest outside diameter of the sheath tube 1 after transverse corrugation should be approximate¬ ly equal to the tube outside diameter before transverse corrugation is carried out, thereby achieving maximum compression as well as optimum control of the shape of the transverse corrugations. A degree of compression of the insulating material amounting to 75% is quite easily attained, the degree of compression being defined as the ratio of the volume enclosed by the sheath tube after compression, to the volume enclosed by the tube before compression.
Further, the transverse corrugation according to the invention also substantially enlarges the circumferential surface of the sheath tube 1. It is, for instance, possible to achieve a surface enlargement in the order of 40%.
Compared with a conventional tubular heating element, the invention makes it possible to save as much material as about 50%.
As an example, it may be mentioned that a sheath tube of stainless steel having a wall thickness of 0.25 mm and a diameter of 10 mm obtained, after compression according to the invention by forming threaded transverse corruga¬ tions, an average wall thickness of 0.18 mm, the corruga¬ tion width B being about 2.5 mm and the corrugation depth being about 1.2 mm.
It should be emphasised that the inventive transverse corrugation of the sheath tube is the only measure used for compressing the pulverulent insulating material, which considerably facilitates the making of tubular heating elements.
Moreover, the inventive transverse corrugation of the sheath tube greatly facilitates a subsequent bending, if any, of the tubular heating element, since the corrugated tube then acts in the manner of a bellows.
When making the transverse corrugations by e.g. roll threading, the alteration of the total length of the tubular heating element may be completely, or at least substantially, eliminated. This is highly advantageous by making it possible to keep given tolerances, in particular as to the length of the tubular heating element.
Naturally, the considerable surface enlargement results in an improved heat emissive power enabling a reduction of the dimensions of the heating element when the surface temperature is maintained, or an increase of the total effect emitted. If the total effect is maintained, a saving of material is possible.
The tubular heating element according to the inven¬ tion is suited for heating gaseous, liquid as well as solid media. If, in the latter case, the transverse corrugation is threaded and the tubular heating element is straight, the heating element is simply screwed into a threaded hole of the member to be heated. The inventive transverse corrugation is also advantageous when the tubular heating element is to be embedded, since it substantially reduces relative movements between the heating element and the member in which it is embedded. It goes without saying that the invention is by no means restricted to the embodiment described above, and thus can be modified within the scope of the appended claims.

Claims

1. An electrically-operated tubular heating element comprising a metal sheath tube (1) filled with an e.g. pulverulent insulating material (2), and at least one helical resistance wire (3) embedded in said insulating material, c h a r a c t e r i s e d in that the sheath tube (1) presents transverse corrugations (8) having a width (B) substantially exceeding the wall thickness of said sheath tube, the transverse corrugations imparting the necessary compression to said pulverulent insulating material.
2. The tubular heating element of claim 1, c h a - r a c t e r i s e d in that the transverse corrugations
(8) further have a depth (D) substantially exceeding the wall thickness of said sheath tube (1).
3. The tubular heating element of claim 1 or 2, c h a r a c t e r i s e d in that the corrugation width (B) is more than three times, preferably more than five times, and most preferably more than ten times, as large as the wall thickness of said sheath tube (1).
4. The tubular heating element of claim 2, c h a ¬ r a c t e r i s e d in that the corrugation depth (D) approximately is half as large as the corrugation width (B).
5. The tubular heating element of any one of claims 1-4, c h a r a c t e r i s e d in that the wall thick¬ ness of the sheath tube (1) is less than 0.4 mm, prefer- ably less than 0.3 mm.
6. Method for making an electrically-operated tubular heating element, comprising the steps of arranging at least one helical resistance wire (3) in a metal sheath tube (1), and filling said tube with an e.g. pulverulent insulating material (2), c h a r a c t e r i s e d in that the necessary compression of the pulverulent insulat¬ ing material (2) is achieved by transversely corrugating said sheath tube (1), the corrugation width (B) sub¬ stantially exceeding the wall thickness of said sheath tube.
7. The method of claim 6, c h a r a c t e r i s e d in that the corrugations (8) are given a depth (D) substantially exceeding the wall thickness of said sheath tube (1).
8. The method of claim 6, c h a r a c t e r i s e d in that the corrugation width (B) is made more than three times, preferably more than ten times, as large as the wall thickness of said sheath tube (1), and that the corrugation depth (D) is made approximately half as large as the corrugation width (B) .
9. The method of any one of claims 6-8, c h a - r a c t e r i s e d by making the largest outside dia¬ meter of the sheath tube (1) af er transverse corrugation approximately equal to the tube outside diameter before said transverse corrugation.
10. The method of any one of claims 6-9, c h a - r a c t e r i s e d in that the transverse corrugation
(8) is the only measure employed for compressing the pulverulent insulating material (2) .
11. The method of any one of claims 6-10, for making tubular heating elements comprising sheath tubes of stainless steel, c h a r a c t e r i s e d by using a sheath tube having a wall thickness of less than 0.4 mm, preferably less than 0.3 mm.
12. The method of any one of claims 6-11, c h a ¬ r a c t e r i s e d in that at least part of the sheath tube (1) is bent after the transverse corrugation.
13. The method of any one of claims 6-12, c h a ¬ r a c t e r i s e d in that the transverse corrugation (8) is carried out by roll threading.
PCT/SE1991/000045 1990-01-24 1991-01-23 Electric tubular heating element and method for making the same WO1991011892A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9000244-5 1990-01-24
SE9000244A SE9000244L (en) 1990-01-24 1990-01-24 ELECTRICAL POWER HEATING ELEMENT AND WAY TO MANUFACTURE THE SAME

Publications (1)

Publication Number Publication Date
WO1991011892A1 true WO1991011892A1 (en) 1991-08-08

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ID=20378334

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1991/000045 WO1991011892A1 (en) 1990-01-24 1991-01-23 Electric tubular heating element and method for making the same

Country Status (2)

Country Link
SE (1) SE9000244L (en)
WO (1) WO1991011892A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2699107A1 (en) * 1992-12-16 1994-06-17 Hotset Heizpatronen Zubehoer Electric heating body for injection molds.
GB2309874A (en) * 1996-02-02 1997-08-06 Emerson Electric Co Electrical heating elements
WO1997038556A1 (en) * 1996-04-04 1997-10-16 Systems Elemental Pty. Limited Compaction of sheathed electric heating elements
EP1037507A2 (en) * 1999-03-18 2000-09-20 Hotset Heizpatronen u. Zubehör GmbH Manufacturing process of electrical heating elements in an injection moulding tool
WO2003007313A2 (en) * 2001-07-03 2003-01-23 Cci Thermal Technologies, Inc. Corrugated metal ribbon heating element
DE202019105668U1 (en) * 2019-10-15 2021-01-19 Türk & Hillinger GmbH Electric tubular heater

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE800583C (en) * 1948-10-02 1950-11-20 Voigt & Haeffner Akt Ges Electric tubular heater with high load capacity
US2958121A (en) * 1955-09-20 1960-11-01 Gen Electric Method of forming integral finned sheathed heaters
DE1565576A1 (en) * 1966-07-02 1970-06-25 Kabel Metallwerke Ghh Heating conductor
FR2230142A1 (en) * 1973-05-17 1974-12-13 Raquin Pierre Flexible heating element for liquids in laboratories - has resistance wire in corrugated tube with end connections
DE2626075B2 (en) * 1976-06-10 1979-06-13 Siemens Ag, 1000 Berlin Und 8000 Muenchen Bending process for electrical tubular heating elements and electrical tubular heating elements manufactured using the bending process

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE800583C (en) * 1948-10-02 1950-11-20 Voigt & Haeffner Akt Ges Electric tubular heater with high load capacity
US2958121A (en) * 1955-09-20 1960-11-01 Gen Electric Method of forming integral finned sheathed heaters
DE1565576A1 (en) * 1966-07-02 1970-06-25 Kabel Metallwerke Ghh Heating conductor
FR2230142A1 (en) * 1973-05-17 1974-12-13 Raquin Pierre Flexible heating element for liquids in laboratories - has resistance wire in corrugated tube with end connections
DE2626075B2 (en) * 1976-06-10 1979-06-13 Siemens Ag, 1000 Berlin Und 8000 Muenchen Bending process for electrical tubular heating elements and electrical tubular heating elements manufactured using the bending process

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2699107A1 (en) * 1992-12-16 1994-06-17 Hotset Heizpatronen Zubehoer Electric heating body for injection molds.
GB2309874A (en) * 1996-02-02 1997-08-06 Emerson Electric Co Electrical heating elements
WO1997038556A1 (en) * 1996-04-04 1997-10-16 Systems Elemental Pty. Limited Compaction of sheathed electric heating elements
EP1037507A2 (en) * 1999-03-18 2000-09-20 Hotset Heizpatronen u. Zubehör GmbH Manufacturing process of electrical heating elements in an injection moulding tool
EP1037507A3 (en) * 1999-03-18 2002-05-29 Hotset Heizpatronen u. Zubehör GmbH Manufacturing process of electrical heating elements in an injection moulding tool
WO2003007313A2 (en) * 2001-07-03 2003-01-23 Cci Thermal Technologies, Inc. Corrugated metal ribbon heating element
WO2003007313A3 (en) * 2001-07-03 2003-08-21 Cci Thermal Technologies Inc Corrugated metal ribbon heating element
US6963053B2 (en) * 2001-07-03 2005-11-08 Cci Thermal Technologies, Inc. Corrugated metal ribbon heating element
DE202019105668U1 (en) * 2019-10-15 2021-01-19 Türk & Hillinger GmbH Electric tubular heater

Also Published As

Publication number Publication date
SE9000244L (en) 1991-07-25
SE9000244D0 (en) 1990-01-24

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