EP0095315B1 - Interrupteur de circuit sensible à la chaleur - Google Patents

Interrupteur de circuit sensible à la chaleur Download PDF

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Publication number
EP0095315B1
EP0095315B1 EP19830302817 EP83302817A EP0095315B1 EP 0095315 B1 EP0095315 B1 EP 0095315B1 EP 19830302817 EP19830302817 EP 19830302817 EP 83302817 A EP83302817 A EP 83302817A EP 0095315 B1 EP0095315 B1 EP 0095315B1
Authority
EP
European Patent Office
Prior art keywords
conductor
heat sensitive
circuit interrupter
sensitive circuit
electrical conductor
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
EP19830302817
Other languages
German (de)
English (en)
Other versions
EP0095315A1 (fr
Inventor
Neil Shaw C/O Heat Trace Limited Malone
Paul Michael Boshell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heat Trace Ltd
Original Assignee
Heat Trace Ltd
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 Heat Trace Ltd filed Critical Heat Trace Ltd
Publication of EP0095315A1 publication Critical patent/EP0095315A1/fr
Application granted granted Critical
Publication of EP0095315B1 publication Critical patent/EP0095315B1/fr
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
    • H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
    • H01H37/761—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material with a fusible element forming part of the switched circuit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
    • H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
    • H01H2037/768—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material characterised by the composition of the fusible material

Definitions

  • the present invention relates to a heat sensitive circuit interrupter.
  • an interrupter which operates to interrupt a circuit when exposed to a temperature at or above a predetermined critical temperature can be used to trigger an alarm or any other appropriate response.
  • One possible use of an interrupter is to monitor the temperature of an item of equipment and to shut down that equipment when the critical temperature is detected.
  • Thermostats of conventional type can perform the function of a circuit interrupter.
  • Thermostats do suffer however from the limitation that they can sense the temperature in their immediate vicinity but cannot detect overheating outside that vicinity.
  • thermostats can only be used if the expense of installing a larger number of them can be justified.
  • Thermostats cannot be used to detect localised overheating in cables at acceptable cost.
  • Heating cables which are used for example to protect process plant against frost are generally referred to as heating tapes. Such tapes are wrapped around pipework and covered in insulation. It is not possible to detect "hot spots" reliably in the tape by monitoring current supplied or the tape resistance and thus the tapes and the systems in which they are incorporated must be designed to be "fail safe” if they are to be used in hazardous areas.
  • a fail safe design is one in which any predictable fault cannot result in overheating.
  • a failsafe design is expensive because it requires a higher degree of complexity and a higher nominal capacity than would be the case if the design was not required to accommodate a variety of possible fault conditions.
  • British Patent No. 1 141 234 also refers to molten metal retention, and suggests overcoming the problem by providing a body which is capable of absorbing the molten metal.
  • Flux is used in conventional meltable alloys such as solder to help the molten metal "wet" a surface to which it is to adhere. Accordingly it could reasonably be assumed that introducing flux into a sheathed meltable wire would increase the probability of any molten portion of the wire maintaining electrical continuity. Surprisingly it has been discovered however that this is not the case.
  • a heat sensitive circuit interrupter comprising an electrical conductor made from a material of predetermined melting temperature and an electrically insulating member supporting the conductor the electrically insulating member being able to withstand temperatures higher than the melting temperature of the electrical conductor characterised in that the heat sensitive circuit interrupter is in the form of a flexible elongate cable along the length of which the electrical conductor extends, the electrical conductor is made from a solder which incorporates flux, and the electrically insulating member is a sheath which encases the electrical conductor, the material of the electrical conductor and the material of the electrically insulating member being such that when the electrical conductor is melted at any locale along the length of the cable the contact angle between the molten conductor and the electrically insulating member is sufficiently large for the molten conductor to flow into separated drops and thereby break the electrical continuity of the electrical conductor and provide an indication of overheating at said locale.
  • solders consisting of 60% tin, 40% lead and incorporating longitudinal cores of flux have proved particularly successful, such solders being used conventionally for making electrical connections.
  • the solder may be rolled to form a flat strip.
  • the present invention is based on the known theory of the behaviour of a liquid when placed on a solid flat surface, which behaviour is dependent upon the contact angle.
  • the contact angle is defined as the angle subtended by the flat surface and a tangent to the liquid surface drawn from the edge of the liquid in a plane perpendicular to the flat surface and the edge of the liquid. If this contact angle is small, the liquid will "wet" the flat surface. If the contact angle is large, the liquid will form drops or bubbles.
  • the contact angle is the resultant of three thermodynamic forces F,, F 2 and F 3 that act on each interface in the liquid/solid/surrounding vapour system. These forces are related as follows:
  • the flux is used to help the liquid to wet the surface.
  • flux is used to cause the liquid solder to separate into separated drops or bubbles. This contrast can be explained by considering the 3 possible effects that the flux has.
  • the illustrated heating tape comprises a sheath 1 within which two copper foils 2, 3 are encased.
  • a woven heating element 4 is positioned beneath the foils but electrically insulated from them by a web 5 of insulating material.
  • a pair of foils 6, 7 of solder are positioned on a support film 8 above the copper foils 2, 3 so as to be separated from the copper foils by a web 9 of insulating material.
  • the support film 8 may be of glass fibre or the plastics marked at "Kapton" 11. Connections are made between the copper foils 2, 3 and the heating element 4 by inserting rivets through the heating elements and the copper foils at spaced locations along the length of the tape.
  • rivets could be placed at one metre intervals along each foil, the rivets on one foil being staggered by 50 cm relative to the rivets on the other foil.
  • a heating tape having a woven heating element and foil conductor structure of this type is described in British Patent No. 1 523 129.
  • the illustrated heating tape is made up by forming a core comprising the foil conductors 2, 3 embedded in an insulating body including webs 5 and 9.
  • the outline of the core is indicated by a dashed line 10 in the drawing.
  • the solder foils 6,7 7 are then adhered to the film 8.
  • the heating element 4 is pressed against one side of the core, and secured by rivets to the foils 2, 3, and the film 8 is pressed against the other side.
  • the resulting assembly is then encased in the sheath 1 by an extrusion process.
  • the tape may have any convenient dimensions, e.g. 20 mm wide and 4 mm thick.
  • the solder foils 6, 7 may be formed by rolling out conventional fine multi-core lead/tin solder wire as used for making connections to electronic components to form a strip approximately 4 mm wide. It has been found that using such a solder foil a break of some 10 mm width occurs in the foil as soon as it is heated to its melting point, the molten solder flowing away from the break to thicken the ends of the foil on either side of the break.
  • Solders can be easily prepared which melt at well defined temperatures over a wide range of temperatures, e.g. 100°C to 300°C. Thus the illustrated tape can be used for a wide variety of purposes.
  • solder foils 6, 7 could be replaced by a nonfusible conductor of for example copper.
  • a monitoring tape could be produced having only one or two solder conductors within it and no heating element or separate supply conductors.
  • the monitoring tape could then be placed in areas where it is desired to detect excessive temperatures, e.g. in electrical cable circuit, or in the ceiling of a warehouse, and connected to a simple circuit adapted to sound an alarm if the solder conductor breaks.
  • the monitoring tape could also be incorporated in equipment, e.g. the windings of electric motors, to automatically shut the equipment down in the event of overheating.
  • solder conductors in the form of thin foils. It will however be appreciated that the solder may be in other forms to suit particular applications providing that once molten it is capable of flowing to form a break.
  • the described embodiment of the invention utilizes a solder in which flux is provided in the form of cores.
  • the solder could however be externally coated with flux.
  • solder is used herein to mean any electrically conductive fusible material. Generally solder will be in the form of a low melting point fusible alloy.
  • the flux can be of any suitable type, but care must be taken to ensure that the flux is stable at the normal temperatures to which it is in use exposed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Fuses (AREA)

Claims (7)

1. Interrupteur de circuit thermosensible comprenant un conducteur électrique constitué par un matériau ayant une température de fusion prédéterminée et un élément isolant électrique portant le conducteur, l'élément isolant électrique étant capable de supporter des températures plus élevées que la température de fusion du conducteur électrique, interrupteur caractérisé en ce que l'interrupteur de circuit thermosensible présente la forme d'un cable allongé flexible, le long duquel s'étend le conducteur électrique (6, 7), que le conducteur électrique est constitué par de l'étain comprenant un fondant et que l'élément isolant électrique est une gaîne (1) qui enveloppe le conducteur électrique, le matériau du conducteur électrique et le matériau de l'élément isolant électrique étant tels que, lorsque le conducteur électrique (6, 7) est fondu en n'importe quelle position le long du cable, l'angle de contact entre le conducteur fondu et l'élément isolant électrique (1) soit suffisamment élevé pour que le conducteur fondu s'écoule par des gouttes séparées et coupe ainsi la continuité électrique du conducteur électrique et fournisse une indication de surchauffe en ce point.
2. Interrupteur de circuit thermosensible selon la revendication 1, caractérisé en ce que le conducteur (6, 7) à la forme d'une bade aplatie.
3. Interrupteur de circuit thermosensible selon la revendication 1, caractérisé en ce que le conducteur (6, 7) est formé par enroulement à plat d'un fil d'étain cylindrique comprenant une pluralité d'âmes de fondant.
4. Interrupteur de circuit thermosensible selon l'une quelconque des revendications précédentes, comprenant deux conducteurs (6, 7) disposés parallèlement, dont au moins un est le conducteur constitué par un matériau à température de fusion prédéterminée, les conducteurs étant reliés entre eux à une extrémité de façon que leur continuité électrique puisse être commandée par l'autre extrémité.
5. Interrupteur de circuit thermosensible selon l'une quelconque des revendications précédentes, incorporé dans une bande chauffante électrique.
6. Interrupteur de circuit thermosensible selon la revendication 5, caractérisé en ce que le conducteur (6, 7) constitué par un matériau à température de fusion prédéterminée, forme un élément chauffant de la bande chauffante.
7. Interrupteur de circuit thermosensible selon l'une quelconque des revendications précédentes, caractérisé en ce que l'élément de support a la forme d'une gaîne (1, 5, 9) qui enveloppe le ou chaque conducteur électrique (6, 7).
EP19830302817 1982-05-22 1983-05-18 Interrupteur de circuit sensible à la chaleur Expired EP0095315B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8214998 1982-05-22
GB8214998 1982-05-22

Publications (2)

Publication Number Publication Date
EP0095315A1 EP0095315A1 (fr) 1983-11-30
EP0095315B1 true EP0095315B1 (fr) 1987-03-25

Family

ID=10530559

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830302817 Expired EP0095315B1 (fr) 1982-05-22 1983-05-18 Interrupteur de circuit sensible à la chaleur

Country Status (4)

Country Link
EP (1) EP0095315B1 (fr)
JP (1) JPS5937625A (fr)
CA (1) CA1194907A (fr)
DE (1) DE3370559D1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE514819C2 (sv) * 1994-02-24 2001-04-30 Ericsson Telefon Ab L M Elektrisk skyddskrets
DE19827374C2 (de) * 1998-06-19 2001-05-23 Daimler Chrysler Ag Sicherungselement für elektrische Anlagen
CN106405318A (zh) * 2016-08-31 2017-02-15 陕西千山航空电子有限责任公司 一种防护记录器热损坏判断方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3406384A (en) * 1966-08-26 1968-10-15 Robert L. Hartman Fire detector and preventer system
DE2121120C3 (de) * 1971-04-29 1973-11-22 Robert Bosch Gmbh, 7000 Stuttgart Übertemperatursicherung fur eine elektrische Wicklung
DE7723699U1 (de) * 1977-07-29 1979-01-25 Straeb, Hermann, Dipl.-Ing., 7022 Leinfelden-Echterdingen Temperatursicherung
DE2808319A1 (de) * 1978-02-27 1979-09-06 Uchihashi Metal Ind Co Ueberhitzungsschmelzsicherung

Also Published As

Publication number Publication date
EP0095315A1 (fr) 1983-11-30
JPS5937625A (ja) 1984-03-01
CA1194907A (fr) 1985-10-08
DE3370559D1 (en) 1987-04-30

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