CA1194907A - Heat sensitive circuit interrupter - Google Patents
Heat sensitive circuit interrupterInfo
- Publication number
- CA1194907A CA1194907A CA000428557A CA428557A CA1194907A CA 1194907 A CA1194907 A CA 1194907A CA 000428557 A CA000428557 A CA 000428557A CA 428557 A CA428557 A CA 428557A CA 1194907 A CA1194907 A CA 1194907A
- Authority
- CA
- Canada
- Prior art keywords
- conductor
- cable
- electrical
- sheath
- solder
- 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
Links
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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Fuses (AREA)
Abstract
HEAT SENSITIVE CIRCUIT INTERRUPTER
ABSTRACT
A heat sensitive circuit interrupter comprising an electrical conductor made from a material of predetermined melting temperature and encased in an electrically insulating sheath.
The sheath is designed to withstand temperatures higher than the melting temperature of the conductor, and the conductor in its molten state flows within the sheath to break the electrical continuity of the conductor. The materials of the conductor and the adjacent portions of the sheath are selected to provide a contact angle for the molten conductor which is sufficiently large for the molten conductor to flow into separated drops. The conductor may be a lead/tin solder incorporating a flux.
ABSTRACT
A heat sensitive circuit interrupter comprising an electrical conductor made from a material of predetermined melting temperature and encased in an electrically insulating sheath.
The sheath is designed to withstand temperatures higher than the melting temperature of the conductor, and the conductor in its molten state flows within the sheath to break the electrical continuity of the conductor. The materials of the conductor and the adjacent portions of the sheath are selected to provide a contact angle for the molten conductor which is sufficiently large for the molten conductor to flow into separated drops. The conductor may be a lead/tin solder incorporating a flux.
Description
HEAT SENSITIVE CIRCUIT INT~RRUPTER
The present inventlon relates to a heat sensitive circult interrupter.
There are ~any applications in which a reliable heat sensitive circuit interrupter can be used to adYantage. For example an interrupter whlch operates to ~nterrupt a c~rcult when exposed to a temperature at or above a predetermined critical temperature can be used to trigger an alarm or any other appro-priate response. One possible use of an interrupter is to monitor the temperature o~ an item of equ~p-ment and to shut down that equipment when the critical temperature is detected.
Thermostats of conYentional type can perform the function of a clrcuit interrupter. Thermostats do suffer however from the limitation that they can sense the temperature in their immediate vicinlty but cannot detect overheating outside that vlcinity.
Thus in many circumstances thermostats can only be used if the expense of installing a large number o~
them can be Justified. For example, it ~s highly desirable to be able to detect overheating o~ cables whether these cables are themselves used for heating purposes or are simply used to carry power or informa-tion slgnals. Thermostats cannot be used to detect localised overheating in cables at acceptable cost.
Heating cables which are used for example to ~' 4~1~7 protect process plant against frost are generally referred to a~ heating tapes. Such tapes are wrapped around pipewor~ and covered in insulatlon. It is not possible to detect "hot spots" reliably ln the tape by monltoring current supplied or the tape resistance and thus the tapes and the systems in which they are incorporated must be deslgned to be "fail safe" if they are to be used in hazardous areas~ A ~ail safe design is one in whlch any predictable fault cannot result in overheating.
A ~t-.5~fe design is expensive because lt requires a higher degree o~ complexlty and a higher nom1 n~l capacity than would be the case if the design was not required to accommodate a variety of possible fault conditions.
It has been known for many years that the heating of an electrical circuit above a critical temperature can be dstected by lncorporating in the circuit a circuit interrupter in the form o~
a wire which melts at the critical temperature.
For example British Patent No. 336 270 dated 1929 - proposes a heating element energised via a wire which melts to break the supply circuit when the heating element becomes overheated. Such arrange-ments have not found acceptance however becauselt ls generally necessary to cover the wire ln lnsulation and when the wire melts its insulation ~4~7 often retalns the molten metal in i~s initial position at least for some time, maint~n~ng electrical continuity.
This molten metal retention effect is described in Brltish Patent Nol 1 164 238 which proposes to overcome the problem by supporting the meltable wire without ~nsulation inside a stiff insulating tube defining sufficlent space lnternally to allow the molten metal to flow easily away from its init~al position. One way of providing this space is to ~ill the interior of th~ stiff tube with an insulating substance that is non-flammable and disintegrate~ or melts at a temperature lower than that at whlch the meltable wire melts. Examples of such ~lllers giYen are silicon grease or a paste flux.
British Patent No. 1 141 234 also refers to molten metal retention, and sugge~ts overcoming the problem by providing a body which is capable of absorblng the molten metal.
~oth the above suggested solut~ons to the problem of molten metal retention are undeslrable .
as they require non-standard extra feature~ which cannot be included in cables at low cost.
More recently, proposals have been made as described ln published PCT Applicat~on WO
83/01138 to provide a monitoring cable in which a meltable conductor ls separated from another conductor by a ~ermeable insulator. When over-heating occurs molten conductor diffuses through the insulatcr and the resultant drop in resistance between the two conductors is detected by suitable monltoring equlpment. Accordlngly this device relies upon the fact that the molten portion of the meltable conductor re~o ~ n-~ in electrical contact with the unmelted portion o~ the meltable conductor leading to the monitoring Pquipment.
Flux ~s used in conventional meltable alloys such as solder to help the molten metal "wet" a sur~ace to which lt ls to adhere. Accordingly it could reasonably be assumed that introducing flux lnto a sheathed meltable wlre would increase the probability o~ any molten portion of the wire maintalnlng electrical continu~ty. Surprisingly it has been discovered howeve~r that this ls not the case.
It ls an ob~ect of the present invention to provlde an lmproved circuit interrupter.
According to the present invention, there is provided a heat sensitive circuit interrupter compris-sing an electrical conductor made from a material of predetermined melting temperature and supported by an electrically insulating member which ls able ... ~L
~9~
5.
to withstand temperatures higher than the said melting temperature~ wherein the material of the electrical conductor and the material of the pol~ion of the insulating member with which it ls ~n contact are such that when the electrical conductor is melted the contact angle between the molten conductor and ths insulating member is sufficiently large ~or the molten conductor to flow into separated drops and thereby break the electrical continuity of the conductorO
Preferably, the conductor is made from a solder which incorporates flux. Solders consisting of 60% tin, 40% lead and lncorporating longitudinal cores of flux have proved particularly successful, such solders being used conventionally for r~kin~
electrical connections. The solder m~ be rolled to form a flat strip.
The present invent~on 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 liquld surface drawn from the edge of the liquld in a plane Z5 perpendicular to the flat surface and the edge of the liquid. If this contact angle is small, the liquid wlll "wet" the flat surface. If the contact 34~7 angle i8 large~ the liquid will form drops or bubbles.
The contact angle is the resultant of three thermodynamic forces F1, F~ and F3 that act on each interface in the llquid/solid/surrounding vapour system. These forces are related as follows:
F1 ~ F2 ~ F3 cos C
where C ~ contact angle ~ 1 = surface free energy of the solid/~apour interface F2 S sur~ace free energy of the solid~llquid interface F3 ~ surface free energy of the liquid/vapour interface (surface tension) The presence of a flux ln a molten solder modifies these thermodynamic forces and hence will af~ect the contact angle. It has been discovered that a melted solder without flux will ~e as a l~quid film and not contract into separated drops, whereas a melted solder with flux will contract into bubbles.
In con~entlonal solder, the flux is used to help the liquid to wet the surface. In contrast, in the present inYention, flux is used to cause the llquid solder to separate into separated drops or bubhles. This contrast can be explained by consldering the 3 possible ef~ects that the flux has .
~I ~L9~9~?~
1~ It chemically remoYes ( or corrodes ) any oxides or imperfections in the flat surface that tend to give the surface a high surfac~ energy.
The present inventlon relates to a heat sensitive circult interrupter.
There are ~any applications in which a reliable heat sensitive circuit interrupter can be used to adYantage. For example an interrupter whlch operates to ~nterrupt a c~rcult when exposed to a temperature at or above a predetermined critical temperature can be used to trigger an alarm or any other appro-priate response. One possible use of an interrupter is to monitor the temperature o~ an item of equ~p-ment and to shut down that equipment when the critical temperature is detected.
Thermostats of conYentional type can perform the function of a clrcuit interrupter. Thermostats do suffer however from the limitation that they can sense the temperature in their immediate vicinlty but cannot detect overheating outside that vlcinity.
Thus in many circumstances thermostats can only be used if the expense of installing a large number o~
them can be Justified. For example, it ~s highly desirable to be able to detect overheating o~ cables whether these cables are themselves used for heating purposes or are simply used to carry power or informa-tion slgnals. Thermostats cannot be used to detect localised overheating in cables at acceptable cost.
Heating cables which are used for example to ~' 4~1~7 protect process plant against frost are generally referred to a~ heating tapes. Such tapes are wrapped around pipewor~ and covered in insulatlon. It is not possible to detect "hot spots" reliably ln the tape by monltoring current supplied or the tape resistance and thus the tapes and the systems in which they are incorporated must be deslgned to be "fail safe" if they are to be used in hazardous areas~ A ~ail safe design is one in whlch any predictable fault cannot result in overheating.
A ~t-.5~fe design is expensive because lt requires a higher degree o~ complexlty and a higher nom1 n~l capacity than would be the case if the design was not required to accommodate a variety of possible fault conditions.
It has been known for many years that the heating of an electrical circuit above a critical temperature can be dstected by lncorporating in the circuit a circuit interrupter in the form o~
a wire which melts at the critical temperature.
For example British Patent No. 336 270 dated 1929 - proposes a heating element energised via a wire which melts to break the supply circuit when the heating element becomes overheated. Such arrange-ments have not found acceptance however becauselt ls generally necessary to cover the wire ln lnsulation and when the wire melts its insulation ~4~7 often retalns the molten metal in i~s initial position at least for some time, maint~n~ng electrical continuity.
This molten metal retention effect is described in Brltish Patent Nol 1 164 238 which proposes to overcome the problem by supporting the meltable wire without ~nsulation inside a stiff insulating tube defining sufficlent space lnternally to allow the molten metal to flow easily away from its init~al position. One way of providing this space is to ~ill the interior of th~ stiff tube with an insulating substance that is non-flammable and disintegrate~ or melts at a temperature lower than that at whlch the meltable wire melts. Examples of such ~lllers giYen are silicon grease or a paste flux.
British Patent No. 1 141 234 also refers to molten metal retention, and sugge~ts overcoming the problem by providing a body which is capable of absorblng the molten metal.
~oth the above suggested solut~ons to the problem of molten metal retention are undeslrable .
as they require non-standard extra feature~ which cannot be included in cables at low cost.
More recently, proposals have been made as described ln published PCT Applicat~on WO
83/01138 to provide a monitoring cable in which a meltable conductor ls separated from another conductor by a ~ermeable insulator. When over-heating occurs molten conductor diffuses through the insulatcr and the resultant drop in resistance between the two conductors is detected by suitable monltoring equlpment. Accordlngly this device relies upon the fact that the molten portion of the meltable conductor re~o ~ n-~ in electrical contact with the unmelted portion o~ the meltable conductor leading to the monitoring Pquipment.
Flux ~s used in conventional meltable alloys such as solder to help the molten metal "wet" a sur~ace to which lt ls to adhere. Accordingly it could reasonably be assumed that introducing flux lnto a sheathed meltable wlre would increase the probability o~ any molten portion of the wire maintalnlng electrical continu~ty. Surprisingly it has been discovered howeve~r that this ls not the case.
It ls an ob~ect of the present invention to provlde an lmproved circuit interrupter.
According to the present invention, there is provided a heat sensitive circuit interrupter compris-sing an electrical conductor made from a material of predetermined melting temperature and supported by an electrically insulating member which ls able ... ~L
~9~
5.
to withstand temperatures higher than the said melting temperature~ wherein the material of the electrical conductor and the material of the pol~ion of the insulating member with which it ls ~n contact are such that when the electrical conductor is melted the contact angle between the molten conductor and ths insulating member is sufficiently large ~or the molten conductor to flow into separated drops and thereby break the electrical continuity of the conductorO
Preferably, the conductor is made from a solder which incorporates flux. Solders consisting of 60% tin, 40% lead and lncorporating longitudinal cores of flux have proved particularly successful, such solders being used conventionally for r~kin~
electrical connections. The solder m~ be rolled to form a flat strip.
The present invent~on 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 liquld surface drawn from the edge of the liquld in a plane Z5 perpendicular to the flat surface and the edge of the liquid. If this contact angle is small, the liquid wlll "wet" the flat surface. If the contact 34~7 angle i8 large~ the liquid will form drops or bubbles.
The contact angle is the resultant of three thermodynamic forces F1, F~ and F3 that act on each interface in the llquid/solid/surrounding vapour system. These forces are related as follows:
F1 ~ F2 ~ F3 cos C
where C ~ contact angle ~ 1 = surface free energy of the solid/~apour interface F2 S sur~ace free energy of the solid~llquid interface F3 ~ surface free energy of the liquid/vapour interface (surface tension) The presence of a flux ln a molten solder modifies these thermodynamic forces and hence will af~ect the contact angle. It has been discovered that a melted solder without flux will ~e as a l~quid film and not contract into separated drops, whereas a melted solder with flux will contract into bubbles.
In con~entlonal solder, the flux is used to help the liquid to wet the surface. In contrast, in the present inYention, flux is used to cause the llquid solder to separate into separated drops or bubhles. This contrast can be explained by consldering the 3 possible ef~ects that the flux has .
~I ~L9~9~?~
1~ It chemically remoYes ( or corrodes ) any oxides or imperfections in the flat surface that tend to give the surface a high surfac~ energy.
2) It chemically removes (or corrodes) any oxldes of lead and tin that may have formed on the solder surfaoe.
~) Excess flux provides a thln low energy film upon which the liquid solder can move more easily.
In convent1onal ~oldering the removal of deposits on the solid surface is the ~o~ n~nt effect and hence the solder will wet the surface, whilst in the present invention ths removal of oxide film in the solder ~s the do~ nAnt effect and hence the surface tension of the liquid solder wlll cause it to flow lnto low energy forms 9 that is drops or bubbles.
An embodiment of the present invention will now be described, by way of example, with re~erence to the accompAnh1n~ drawing which ls an end view of a heating tape incorporating a heat sensitive clrcuit interrupter according to the inventlon.
The illustrated heating tape comprlses a sheath 1 within which two copper foils 2, 3 are encasedO A woven heating element 4 is positioned beneath the foils but electrically ~nsulated from 8.
them by a web 5 of lnsulatlng materlal. A palr of foils 6, 7 of solder are posltioned on a support fllm 8 above the copper foils 2, ~ so as to be separated ~rom the copper ~oils by a web 9 of insulatlng material. The support film 8 may ~e of glass fibre or th0 plastics marketed as 'tKapton"~
Connections are made between the copper foils 2,
~) Excess flux provides a thln low energy film upon which the liquid solder can move more easily.
In convent1onal ~oldering the removal of deposits on the solid surface is the ~o~ n~nt effect and hence the solder will wet the surface, whilst in the present invention ths removal of oxide film in the solder ~s the do~ nAnt effect and hence the surface tension of the liquid solder wlll cause it to flow lnto low energy forms 9 that is drops or bubbles.
An embodiment of the present invention will now be described, by way of example, with re~erence to the accompAnh1n~ drawing which ls an end view of a heating tape incorporating a heat sensitive clrcuit interrupter according to the inventlon.
The illustrated heating tape comprlses a sheath 1 within which two copper foils 2, 3 are encasedO A woven heating element 4 is positioned beneath the foils but electrically ~nsulated from 8.
them by a web 5 of lnsulatlng materlal. A palr of foils 6, 7 of solder are posltioned on a support fllm 8 above the copper foils 2, ~ so as to be separated ~rom the copper ~oils by a web 9 of insulatlng material. The support film 8 may ~e of glass fibre or th0 plastics marketed as 'tKapton"~
Connections are made between the copper foils 2,
3 and the heatlng element 4 by lnserting rivets through the heating elements and the copper ~oils at spaced locations along the length of the tape.
For example rivets could be placed at one metre intervals along each foil, the r~vets on one foil being staggered by 50 cm relat~ve to the rivets on the other foil. A heating tape having a woven heating element and foil conductor structure of this type is descr~bed 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 are ~hen adhered to the film 8. The heat~ng element 4 ls pressed against one side of the core, and secured by rivets to the folls 27 ~,and the fllm 8 ls pressed against the other slde. The resulting assembly ls then encased ln the sheath.
~L9 9.
1 by an extrusion proces~.
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 con~entional ~ine multi-core lead/tin solder wire as used for ~k~ n~
connection~ to electron~c components to form a strip approxlmately 4 mm wide. It has been found that using such a solder foil a break of some 10 mm width occurs ln the foll as soon as it is heated to lts melting point, the molten solder flowin~
away ~rom the break to thicken the ends of the foil on either side of the break.
Solders can be easily prepared whlch melt at well defined temperatures over a wide range o~
temperatures, e.g. 100C to 300C. Thus the illustrated tape can be used for a wide variety of purposes.
It is possible to dispense with the copper foils 2, ~ and use the solder folls 6, 7 to supply ener~y to the heating element. In some circumstances this might not be so advantageous however as i~
power is supplied via the solder sparks might occur when it melts and breaks. In contrast in the illustrated arrangement a low voltage monitoring circult could be connected between the foils 6, 7 at one end of the tape, the other enfls of the ~oils 6, 7 being connected together. With a low voltage 10.
monitorlng clrcuit there is no risk of sparklng.
It will be appreciated that one of the solder foils 6 9 7 could be replaced by a non-fusible conductor of for example copper~
It will be appreciated that the lnvention has appllcations not related to heating tapes. For example a monitoring tape could be produced having only one or two solder conductors withln lt and no heating element or separate supply conductors.
The monitoring tape could then be placed in areas where it is desired to detect excessi~e temperatures~
e~g. in electrical cable conduit, or in the ae~ e o~ a warehouse, and co~nected to a simple circuit adapted to sound an alarm i~ the solder conductor ~5 breaks. The monitorin~ tape could also be incorpora~
ted ~n equipment, e~g. the w~ nding5 of electrlc motors, to automatlcally shut the equipment down in the-event of overheating~
The lllustrated embodiment shows the A~older conductors in the form of thin foils. It will however be appreciated that the solder may be ln other forms to suit particular applications provid-lng that once molten it ls capable of flowlng to form a break.
Experlments have shown that both single and multl-core fluxed solder work satls~actori~y although multl-core solder ls particularly good as it flows more freely to form separate balls of molten metal. Simple unfluxed solder generally does not work as it melts but does not flow easily to form a break. Unfluxed solder lying in flux powder will also not work effectively if ~he fl~x powder is allowed to oxidise.
The described embodiment of the invention utilizes a solder in which flux is pro~ided ln the form of` cores. The solder could however be externally coated wi*h flux.
The term "solder" is used herein to mean any electrically conductive fusible material~ Generally solder will be ln the form of a low melting po~nt fusible alloy. The flux can be of any suitable type~
but care must be taken to ensure that the flux ls stable at the normal temperatures to which it is in use exposedO
..;, . i-d~
For example rivets could be placed at one metre intervals along each foil, the r~vets on one foil being staggered by 50 cm relat~ve to the rivets on the other foil. A heating tape having a woven heating element and foil conductor structure of this type is descr~bed 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 are ~hen adhered to the film 8. The heat~ng element 4 ls pressed against one side of the core, and secured by rivets to the folls 27 ~,and the fllm 8 ls pressed against the other slde. The resulting assembly ls then encased ln the sheath.
~L9 9.
1 by an extrusion proces~.
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 con~entional ~ine multi-core lead/tin solder wire as used for ~k~ n~
connection~ to electron~c components to form a strip approxlmately 4 mm wide. It has been found that using such a solder foil a break of some 10 mm width occurs ln the foll as soon as it is heated to lts melting point, the molten solder flowin~
away ~rom the break to thicken the ends of the foil on either side of the break.
Solders can be easily prepared whlch melt at well defined temperatures over a wide range o~
temperatures, e.g. 100C to 300C. Thus the illustrated tape can be used for a wide variety of purposes.
It is possible to dispense with the copper foils 2, ~ and use the solder folls 6, 7 to supply ener~y to the heating element. In some circumstances this might not be so advantageous however as i~
power is supplied via the solder sparks might occur when it melts and breaks. In contrast in the illustrated arrangement a low voltage monitoring circult could be connected between the foils 6, 7 at one end of the tape, the other enfls of the ~oils 6, 7 being connected together. With a low voltage 10.
monitorlng clrcuit there is no risk of sparklng.
It will be appreciated that one of the solder foils 6 9 7 could be replaced by a non-fusible conductor of for example copper~
It will be appreciated that the lnvention has appllcations not related to heating tapes. For example a monitoring tape could be produced having only one or two solder conductors withln lt and no heating element or separate supply conductors.
The monitoring tape could then be placed in areas where it is desired to detect excessi~e temperatures~
e~g. in electrical cable conduit, or in the ae~ e o~ a warehouse, and co~nected to a simple circuit adapted to sound an alarm i~ the solder conductor ~5 breaks. The monitorin~ tape could also be incorpora~
ted ~n equipment, e~g. the w~ nding5 of electrlc motors, to automatlcally shut the equipment down in the-event of overheating~
The lllustrated embodiment shows the A~older conductors in the form of thin foils. It will however be appreciated that the solder may be ln other forms to suit particular applications provid-lng that once molten it ls capable of flowlng to form a break.
Experlments have shown that both single and multl-core fluxed solder work satls~actori~y although multl-core solder ls particularly good as it flows more freely to form separate balls of molten metal. Simple unfluxed solder generally does not work as it melts but does not flow easily to form a break. Unfluxed solder lying in flux powder will also not work effectively if ~he fl~x powder is allowed to oxidise.
The described embodiment of the invention utilizes a solder in which flux is pro~ided ln the form of` cores. The solder could however be externally coated wi*h flux.
The term "solder" is used herein to mean any electrically conductive fusible material~ Generally solder will be ln the form of a low melting po~nt fusible alloy. The flux can be of any suitable type~
but care must be taken to ensure that the flux ls stable at the normal temperatures to which it is in use exposedO
..;, . i-d~
Claims (9)
EXCLUSIVE PROPERTY OR PRIVALEGE IS CLAIMED ARE
DEFINED AS FOLLOWS:
1. A flexible cable comprising a continuous heat sensitive circuit interrupter extending along the length of the cable for interrupting a circuit to provide an indication of overheating at one or more locales along the cable, the interrupter comprising an electrical conductor made from a material of predetermined melting temperature, said conductor being adapted to be coupled in circuit with said circuit, the interrupter further comprising an electrically insulating member for supporting the conductor, said member being able to withstand temperatures higher than the material melting temperature, wherein the material of the electrical conductor and the material of the portion of the insulating member with which it is in contact are such that when the electrical conductor is melted the contact angle between the molten conductor and the insulating member is sufficiently large for the molten conductor to flow into separated drops and thereby break the electrical continuity of the conductor to provide an indication of overheating at said locale.
2. A cable according to claim 1, wherein the electrical conductor is made from a solder which incorporates flux.
3. A cable according to claim 1, wherein the conductor is in the form of a flattened strip.
4. A cable according to claim 2, wherein the conductor is in the form of a flattened strip formed by rolling flat a cylindrical solder wire incorporating a plurality of cores of flux.
5. A cable according to claim 1, comprising two conductors arranged in parallel wherein at least one of which is the conductor made from a material of predetermined melting temperature, the conductors being connected together at one end such that their electrical continuity can be monitored from the other end.
6. A cable according to claim 1, wherein the cable is an electrical heating tape having a heating element.
7. A cable according to claim 6, wherein the conductor made from a material of predetermined melting temperature is adapted to supply power to the heating element of the heating tape.
8. A cable according to claim 1, wherein the support member is in the form of a sheath which encases the electrical conductor.
9. A cable for use with a monitoring circuit capable of detecting a discontinuity in an electrical circuit, said cable for detecting an overheat condition at a locale along the cable, said cable comprising:
a sheath of electrically insulative material, and a conductor comprising an electrically conductive material and flux, said conductor being meltable at a temperature in excess of a predetermined temperature, wherein said conductor is encased within the sheath leaving substantially no space between the sheath and conductors so that a temperature at a locale in excess of the predetermined temperature causes the conductor to melt and to separate producing a discontinuity in the conductor which is detachable by the monitoring circuit.
a sheath of electrically insulative material, and a conductor comprising an electrically conductive material and flux, said conductor being meltable at a temperature in excess of a predetermined temperature, wherein said conductor is encased within the sheath leaving substantially no space between the sheath and conductors so that a temperature at a locale in excess of the predetermined temperature causes the conductor to melt and to separate producing a discontinuity in the conductor which is detachable by the monitoring circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8214998 | 1982-05-22 | ||
| GB8214998 | 1982-05-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194907A true CA1194907A (en) | 1985-10-08 |
Family
ID=10530559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000428557A Expired CA1194907A (en) | 1982-05-22 | 1983-05-20 | Heat sensitive circuit interrupter |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0095315B1 (en) |
| JP (1) | JPS5937625A (en) |
| CA (1) | CA1194907A (en) |
| DE (1) | DE3370559D1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE514819C2 (en) * | 1994-02-24 | 2001-04-30 | Ericsson Telefon Ab L M | Electrical protection circuit |
| DE19827374C2 (en) * | 1998-06-19 | 2001-05-23 | Daimler Chrysler Ag | Fuse element for electrical systems |
| CN106405318A (en) * | 2016-08-31 | 2017-02-15 | 陕西千山航空电子有限责任公司 | Protection recorder thermal damage determining method |
Family Cites Families (4)
| 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 (en) * | 1971-04-29 | 1973-11-22 | Robert Bosch Gmbh, 7000 Stuttgart | Overtemperature protection for an electrical winding |
| DE7723699U1 (en) * | 1977-07-29 | 1979-01-25 | Straeb, Hermann, Dipl.-Ing., 7022 Leinfelden-Echterdingen | Thermal fuse |
| DE2808319A1 (en) * | 1978-02-27 | 1979-09-06 | Uchihashi Metal Ind Co | Thermal fuse with meltable substance between two wires - has shell of heat resistant resin surrounded by outer casing of inorganic material |
-
1983
- 1983-05-18 DE DE8383302817T patent/DE3370559D1/en not_active Expired
- 1983-05-18 EP EP19830302817 patent/EP0095315B1/en not_active Expired
- 1983-05-20 CA CA000428557A patent/CA1194907A/en not_active Expired
- 1983-05-23 JP JP8929883A patent/JPS5937625A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0095315B1 (en) | 1987-03-25 |
| EP0095315A1 (en) | 1983-11-30 |
| JPS5937625A (en) | 1984-03-01 |
| DE3370559D1 (en) | 1987-04-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR910008686B1 (en) | Current interrupter | |
| EP0270370B1 (en) | Electrical heaters | |
| US4368452A (en) | Thermal protection of aluminum conductor junctions | |
| RU2321930C2 (en) | Overvoltage protective device | |
| EP0141344B1 (en) | Time delay electric fuse | |
| US4538133A (en) | Passively detonated explosively-assisted fuse | |
| US4891500A (en) | Self-healing parallel heating tape | |
| US4581674A (en) | Thermal fuse device for protecting electrical fixtures | |
| US3377448A (en) | Thermal responsive miniature fuse | |
| CA1194907A (en) | Heat sensitive circuit interrupter | |
| FR2449959A1 (en) | THERMAL CIRCUIT BREAKER WITH FUSE | |
| EP0677206B1 (en) | A capacitor provided with internal protection | |
| EP2867911B1 (en) | Protecting electrical distribution equipment against overheating | |
| NZ197765A (en) | Electric blanket safety circuit | |
| CN215377360U (en) | Composite melt for fuse and fuse | |
| KR20220135384A (en) | Heating cable composed with linear temperature sensor | |
| JP2006190595A (en) | Heat sensitive wire and apparatus protection method | |
| JPS5457241A (en) | Heat-sensitive body | |
| JP2991406B2 (en) | Abnormal temperature prevention device for fixing device | |
| US5438474A (en) | Protective sheath | |
| JPS6439230A (en) | Protective device for superconducting circuit | |
| CN215068536U (en) | Signal switch for fire-fighting product | |
| SU1735935A1 (en) | Overheating protective gear for electric installations | |
| KR0119860Y1 (en) | Thermal sensing wire inserting cable | |
| CN215377359U (en) | Composite fuse wire for fuse and fuse |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |