US3716693A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tubular heating element
Assignee: Individual
•
Filing: 1971-05-17
•
Granted: 1973-02-13
•
Expires: 1991-05-17
Abstract
Abstract An electrical tubular heating element comprises an outer tube of metal and at least one electrical heating resistance, which is arranged in the outer tube. The zone adjacent to the inner wall of the outer tube is filled with magnesium oxide or another insulating material with a high melting point. Immediately adjacent to the heating resistance at least one layer or glass or another additional insulating material is provided so that when the temperature of the outer tube reaches a certain maximum value, a leakage current sufficient for switching off the tubular heating element flows between the coils of the heating resistance or a wire core arranged inside this heating resistance.
Inventors
- 👤 R Bleckmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 10:52
CPC Classifications
H; H05; H05B; H05B3/00; H05B3/40; H05B3/42; H05B3/46; H05B3/10; H05B3/18; H05B3/48
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
149 words
In an electrical tubular heating element comprising an outer metal tube and at least one electrical resistance coil heating element having electrical terminals mounted and electrically insulated from the outer tube to define a heating zone therebetween; a high melting point first insulating material filling said zone, said first insulating material being refractory and heat conductive; an additional insulating material arranged immediately adjacent the heating element, said additional insulating material having a lower softening and melting point than said first insulating material and being more electrically conductive when so softened and melted, the point of softening and melting being so chosen that a flow of current suitable to short circuit an over-heated portion of the resistance coil takes place through the additional insulating material when the temperature immediately adjacent to the heating element reaches a value at which the temperature of the outer tube exceeds the permissible maximum value.
Claim 2
Dependent Claim
149 words
In an electrical tubular heating element comprising an outer metal tube and at least one electrical resistance coil heating element having electrical terminals mounted and electrically insulated from the outer tube to define a heating zone therebetween; a high melting point first insulating material filling said zone, said first insulating material being refractory and heat conductive; an additional insulating material arranged immediately adjacent the heating element, said additional insulating material having a lower softening and melting point than said first insulating material and being more electrically conductive when so softened and melted, the point of softening and melting being so chosen that a flow of current suitable to short circuit an over-heated portion of the resistance coil takes place through the additional insulating material when the temperature immediately adjacent to the heating element reaches a value at which the temperature of the outer tube exceeds the permissible maximum value.
Claim 3
Dependent Claim
149 words
In an electrical tubular heating element comprising an outer metal tube and at least one electrical resistance coil heating element having electrical terminals mounted and electrically insulated from the outer tube to define a heating zone therebetween; a high melting point first insulating material filling said zone, said first insulating material being refractory and heat conductive; an additional insulating material arranged immediately adjacent the heating element, said additional insulating material having a lower softening and melting point than said first insulating material and being more electrically conductive when so softened and melted, the point of softening and melting being so chosen that a flow of current suitable to short circuit an over-heated portion of the resistance coil takes place through the additional insulating material when the temperature immediately adjacent to the heating element reaches a value at which the temperature of the outer tube exceeds the permissible maximum value.
Claim 4
Dependent Claim
149 words
In an electrical tubular heating element comprising an outer metal tube and at least one electrical resistance coil heating element having electrical terminals mounted and electrically insulated from the outer tube to define a heating zone therebetween; a high melting point first insulating material filling said zone, said first insulating material being refractory and heat conductive; an additional insulating material arranged immediately adjacent the heating element, said additional insulating material having a lower softening and melting point than said first insulating material and being more electrically conductive when so softened and melted, the point of softening and melting being so chosen that a flow of current suitable to short circuit an over-heated portion of the resistance coil takes place through the additional insulating material when the temperature immediately adjacent to the heating element reaches a value at which the temperature of the outer tube exceeds the permissible maximum value.
Claim 5
Dependent Claim
17 words
A tubular heating element as claimed in claim 1, in which the additional insulating material is glass.
Claim 6
Dependent Claim
20 words
A tubular heating element as claimed in claim 1, in which the additional insulating material is a glass fiber fabric.
Claim 7
Dependent Claim
28 words
A tubular heating element as claimed in claim 1, in which the additional insulating material is a glass hose, whose wall thickness lies between 0.2 and 0.5 mm.
Claim 8
Dependent Claim
39 words
A tubular heating element as claimed in claim 1, in which the element is a heating helix in which at least one electrically conductive core is arranged, and is insulated from the heating coil by the additional insulating material.
Claim 9
Dependent Claim
61 words
A tubular heating element as claimed in claim 5, in which the electrically conductive core is formed by a wire extending substantially concentrically to the outer tube, the additional insulating material being arranged in a layer of a thickness of 0.2 to 0.5 mm with the coils of the heating element lying directly on the layer of the additional insulating material.
Claim 10
Dependent Claim
30 words
A tubular element as claimed in claim 6, in which on the electrically conducting core a glass fiber fabric hose is arranged with a thickness of 0.2 to 0.5 mm.
Claim 11
Dependent Claim
26 words
A tubular heating element as claimed in claim 1, in which the heating element is covered by a hose which consists of the additional insulating material.
Claim 12
Dependent Claim
21 words
A tubular heating element as claimed in claim 5, in which the electrically conductive core is coateD with an enamel layer.
Claim 13
Dependent Claim
29 words
A tubular heating element as claimed in claim 1, in which the resistance wire of the heating element has spun round it a thread of the additional insulating material.
Claim 14
Dependent Claim
26 words
A tubular heating element as claimed in claim 10, in which the resistance wire of the heating element has a thread-like glass material spun round it.
Claim 15
Dependent Claim
33 words
A tubular heating element as claimed in claim 5, in which the electrically conductive core is connected with one of the two terminal ends of the heating element in an electrically conductive manner.
Claim 16
Dependent Claim
77 words
A tubular heating element as claimed in claim 5, in which at least one heating helix is provided, two parallel electrically conductive wire-shaped cores inside said at least one helix with the two core wires insulated from each other by means of the additional insulating material and a connection end of the heating helix is connected in an electrically conductive manner with one core and the other connecting end of the heating helix with the other core.
Claim 17
Dependent Claim
42 words
A tubular heating element as claimed in claim 10, in which several heating helices are provided in the form of a double or multiple helix with the resistance wires of the heating helices being insulated from each other by means of glass.
Claim 18
Dependent Claim
26 words
A tubular heating element as claimed in claim 1, in which the resistance wire is a helix arranged on a strand of the additional insulating material.
Claim 19
Dependent Claim
39 words
A tubular heating element as claimed in claim 1, in which the surface loading of the heating element is less than 25 watt per square centimeter so that it can be used again after actuating the overcurrent protection device.
Claim 20
Dependent Claim
18 words
A tubular heating element as claimed in claim 1, in which the additional insulating material is mineral wool.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-13 | 1976-08-14 | 1977-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-13 | 1980-08-14 | 1981-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-13 | 1984-08-14 | 1985-02-13 | $7700.00 | Window Closed / Lapsed |