CA2176323A1 - Thermal cutoff and fuse - Google Patents
Thermal cutoff and fuseInfo
- Publication number
- CA2176323A1 CA2176323A1 CA 2176323 CA2176323A CA2176323A1 CA 2176323 A1 CA2176323 A1 CA 2176323A1 CA 2176323 CA2176323 CA 2176323 CA 2176323 A CA2176323 A CA 2176323A CA 2176323 A1 CA2176323 A1 CA 2176323A1
- Authority
- CA
- Canada
- Prior art keywords
- thermal cutoff
- lead
- leads
- fuse
- fusible
- 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.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/10—Adaptation for built-in fuses
-
- 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
- H01H37/764—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material in which contacts are held closed by a thermal pellet
- H01H37/765—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material in which contacts are held closed by a thermal pellet using a sliding contact between a metallic cylindrical housing and a central electrode
-
- 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
- H01H2037/769—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 insulating fusible materials, e.g. for use in the thermal pellets
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H37/00—Thermally-actuated switches
- H01H37/002—Thermally-actuated switches combined with protective means
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Fuses (AREA)
Abstract
A unitary electrical circuit component for protecting against both excessive temperature and excessive current is defined by a temperature responsive thermal cutoff having a current responsive fusible electrical lead.
Description
. ~
~76323 THERMAL CUTOFF AND FUSE
BACKG~OUND OF THE INVENTION
This application relates to the art of 5 electrical circuit protectors and, more particularly, to such protectors that respond to either excessive heat or excessive current to interrupt the circuit. The invention is particularly applicable to thermal cutoffs of the 10 type having a thermal pellet that melts above a predetc~rm; n-~d temperature to interrupt a circuit by opening a pair of contacts and will be described with cp~ifi~ reference thereto. However, it will be appreciated that the invention has broader 15 aspects and can be used with other types of thermal cutof f s .
Electric circuit protection against both excessive heat and excessive current is commonly provided by the use of a thermal cutoff and a fuse.
20 Installing two separate devices in a circuit is time ~ ncllming and expensive, and it would be desirable to have a single device that could be installed in a circuit for providing both types of protection.
SU~ARY OF THE INVENTION
A unitary device that provides electrical circuit protection against both excessive heat and excessive current i n~ p~ a thermal cutoff and a fuse. In a preferred arrangement, the thermal cutoff has electrical leads and the fuse that responds to excessive current is integrally provided in one of the leads. Installation of the device in a circuit simply requires connection of the thermal CLCORPOI Doc~ 32 1 cutof f electrical leads to provide protection against both excessive heat and excessive current.
The fusible section of the lead is preferably integral with the lead although it will be recognized that it is possible to weld or solder a fuse into the lead.
The circuit protector of the present application has a normal operating current rating that is between about 15-20 amps and the fusible section Lu~LuLes when it is subjected to current between about 500-1,000 amps.
It is a principal object of the present invention to provide a unitary device that affords circuit protection against both excessive heat and excessive current.
It is also an object of the invention to provide a circuit protector in the form of a combined thermal cutoff and fuse.
It is an additional object of the invention to provide a combined thermal cutoff and fuse in a compact package that is easy to manuf acture and insta l l .
BRIEF DESCRIPTION OF THE DRAWING
Figure l is a cross-sectional elevational view of a combined thermal cutof f and fuse constructed in accordance with the present application; and Flgure 2 is a perspective illustration of a thermal cutoff lead having a fusible section integrally formed therein.
CLCOElPOI Doc~ 3' 1 2~7~:~23 DESCRIPTION OF A ~ ;LI EMBODIMENT
Referring now to the drawing, wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not 5 for purposes of limiting same, FLgure 1 shows a combined thermal cutoff and fuse constructed in accordance with the present application. The thermal cutoff - , ^nt; n~ P~ a cylindrical metal housing 10 having an elongated electrical lead 10 12 attached to bottom end 14 thereof.
A dielectric thermal pellet 16 positioned within housing 10 adjacent bottom 14 thereof is solid at the normal operating temperature environment of device A, and melts at and above a 15 predetPrminpd excessive temperature. Many different organic chemical compositions may be used for thermal pellet 16 and examples include caffeine and animal protein.
A spring 20 compressed between metal 20 washers 22, 24 normally biases a sl i~h~l~ star contact 26 into Pn~3 nt with a fixed contact 28 on an electrical lead 30. Star contact 26 has a plurality of circumferentially-spaced resilient peripheral fingers slidably engaging the interior 25 surface of housing 10.
A coil spring 32 partly positioned around a reduced diameter end portion of a ceramic bushing 34 engages star contact 26 on the opposite side thereof from spring 20. Bushing 34 is closely 30 received within housing 10 and the open end of housing 10 is crimped inwardly as indicated at 40 to retain bushing 34 therein. A potting compound such CLCORPOI Doc: 18513~ 1 ~176323 a6 epoxy 42 is positioned over bushing 34 and crimped housing end 40 around lead 30 to seal the interior of housing lo.
Nhen thermal pellet 16 is solid as shown 5 in Figure 1, the biasing force of spring 20 is substantially greater than the biasing force of spring 32 so that star contact 26 is held in en~ nt with fixed contact 28 on lead 30. This provides a complete circuit between leads 12, 30 10 through housing 10 and contacts 26, 28. When thermal pellet 16 melts, spring 20 expands and the biasing force of spring 32 becomes greater than the biasing force of spring 20 so that slidable star contact 26 is moved away from fixed contact 28 to 15 open the circuit.
Electrical lead 30 extends through a central hole 44 in bushing 34 and has an enlarged end that def ines f ixed contact 2 8 . Lead 3 0 has a free t~rm;n~l end 46 and is provided with a fusible 20 section located intermediate t~ormin~l end 46 and the thermal cutoff component portion of device A. In the arrangement shown, the fusible section is generally indicated at 50 as having a cross-sectional area that is substantially less than the 25 cross-sectional area of the rr~-; nA~r of lead 30.
Fusible section 50 is preferably located substantially remote from terminal end 46 so that it will not be affected by heat if lead 30 is soldered into a circuit and will not otherwise be damaged by 30 attachment of lead 30 into a circuit. Fusible section 50 is shown as having been formed by CLCORPOI Doc: 18513;!_1 2~7B323 stamping lead 3 0 to provide a small section of substantially reduced cross-sPc~ion ll area.
Figure 2 shows fusible section 50 as being located int~ te slightly reduced SDCti nnc 52, 5 54 o~ lead 30. In the preferred arr~ L shown, fusible section 50 Ls of the same material as lead 30 which may be a copper silver alloy. It will be recognized that it is also possible to weld, solder or otherwise secure a fusible section of other 10 materials and shapes int~ te a lead 3 0 so that it becomes a unitary and integral part of hi ned device A. In the preferred arr~ t, in-~device A has a normal operating current rating that is between about 15-20 amps. Excessive current of 15 about 500-1,000 amps will heat fusible section 50 sufficiently to cause rupture of same and interrupt the circuit. Excessive heat other than that provided by excessive current will melt thermal pellet 16 to interrupt the circuit by operation of 20 the thermal cutoff portion of the - ' in~.~ device.
Although the invention has been shown and described with respect to a pref erred P~ho~ t, it is obvious that equivalent alterations and modif ications will occur to others skilled in the 2 5 art upon the reading and understanding of this specif ication . The present invention i n~ c all such equivalent alterations and modifications, and is limited only by the scope of the claims.
CLCORPOI DCG 185132_~
~76323 THERMAL CUTOFF AND FUSE
BACKG~OUND OF THE INVENTION
This application relates to the art of 5 electrical circuit protectors and, more particularly, to such protectors that respond to either excessive heat or excessive current to interrupt the circuit. The invention is particularly applicable to thermal cutoffs of the 10 type having a thermal pellet that melts above a predetc~rm; n-~d temperature to interrupt a circuit by opening a pair of contacts and will be described with cp~ifi~ reference thereto. However, it will be appreciated that the invention has broader 15 aspects and can be used with other types of thermal cutof f s .
Electric circuit protection against both excessive heat and excessive current is commonly provided by the use of a thermal cutoff and a fuse.
20 Installing two separate devices in a circuit is time ~ ncllming and expensive, and it would be desirable to have a single device that could be installed in a circuit for providing both types of protection.
SU~ARY OF THE INVENTION
A unitary device that provides electrical circuit protection against both excessive heat and excessive current i n~ p~ a thermal cutoff and a fuse. In a preferred arrangement, the thermal cutoff has electrical leads and the fuse that responds to excessive current is integrally provided in one of the leads. Installation of the device in a circuit simply requires connection of the thermal CLCORPOI Doc~ 32 1 cutof f electrical leads to provide protection against both excessive heat and excessive current.
The fusible section of the lead is preferably integral with the lead although it will be recognized that it is possible to weld or solder a fuse into the lead.
The circuit protector of the present application has a normal operating current rating that is between about 15-20 amps and the fusible section Lu~LuLes when it is subjected to current between about 500-1,000 amps.
It is a principal object of the present invention to provide a unitary device that affords circuit protection against both excessive heat and excessive current.
It is also an object of the invention to provide a circuit protector in the form of a combined thermal cutoff and fuse.
It is an additional object of the invention to provide a combined thermal cutoff and fuse in a compact package that is easy to manuf acture and insta l l .
BRIEF DESCRIPTION OF THE DRAWING
Figure l is a cross-sectional elevational view of a combined thermal cutof f and fuse constructed in accordance with the present application; and Flgure 2 is a perspective illustration of a thermal cutoff lead having a fusible section integrally formed therein.
CLCOElPOI Doc~ 3' 1 2~7~:~23 DESCRIPTION OF A ~ ;LI EMBODIMENT
Referring now to the drawing, wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not 5 for purposes of limiting same, FLgure 1 shows a combined thermal cutoff and fuse constructed in accordance with the present application. The thermal cutoff - , ^nt; n~ P~ a cylindrical metal housing 10 having an elongated electrical lead 10 12 attached to bottom end 14 thereof.
A dielectric thermal pellet 16 positioned within housing 10 adjacent bottom 14 thereof is solid at the normal operating temperature environment of device A, and melts at and above a 15 predetPrminpd excessive temperature. Many different organic chemical compositions may be used for thermal pellet 16 and examples include caffeine and animal protein.
A spring 20 compressed between metal 20 washers 22, 24 normally biases a sl i~h~l~ star contact 26 into Pn~3 nt with a fixed contact 28 on an electrical lead 30. Star contact 26 has a plurality of circumferentially-spaced resilient peripheral fingers slidably engaging the interior 25 surface of housing 10.
A coil spring 32 partly positioned around a reduced diameter end portion of a ceramic bushing 34 engages star contact 26 on the opposite side thereof from spring 20. Bushing 34 is closely 30 received within housing 10 and the open end of housing 10 is crimped inwardly as indicated at 40 to retain bushing 34 therein. A potting compound such CLCORPOI Doc: 18513~ 1 ~176323 a6 epoxy 42 is positioned over bushing 34 and crimped housing end 40 around lead 30 to seal the interior of housing lo.
Nhen thermal pellet 16 is solid as shown 5 in Figure 1, the biasing force of spring 20 is substantially greater than the biasing force of spring 32 so that star contact 26 is held in en~ nt with fixed contact 28 on lead 30. This provides a complete circuit between leads 12, 30 10 through housing 10 and contacts 26, 28. When thermal pellet 16 melts, spring 20 expands and the biasing force of spring 32 becomes greater than the biasing force of spring 20 so that slidable star contact 26 is moved away from fixed contact 28 to 15 open the circuit.
Electrical lead 30 extends through a central hole 44 in bushing 34 and has an enlarged end that def ines f ixed contact 2 8 . Lead 3 0 has a free t~rm;n~l end 46 and is provided with a fusible 20 section located intermediate t~ormin~l end 46 and the thermal cutoff component portion of device A. In the arrangement shown, the fusible section is generally indicated at 50 as having a cross-sectional area that is substantially less than the 25 cross-sectional area of the rr~-; nA~r of lead 30.
Fusible section 50 is preferably located substantially remote from terminal end 46 so that it will not be affected by heat if lead 30 is soldered into a circuit and will not otherwise be damaged by 30 attachment of lead 30 into a circuit. Fusible section 50 is shown as having been formed by CLCORPOI Doc: 18513;!_1 2~7B323 stamping lead 3 0 to provide a small section of substantially reduced cross-sPc~ion ll area.
Figure 2 shows fusible section 50 as being located int~ te slightly reduced SDCti nnc 52, 5 54 o~ lead 30. In the preferred arr~ L shown, fusible section 50 Ls of the same material as lead 30 which may be a copper silver alloy. It will be recognized that it is also possible to weld, solder or otherwise secure a fusible section of other 10 materials and shapes int~ te a lead 3 0 so that it becomes a unitary and integral part of hi ned device A. In the preferred arr~ t, in-~device A has a normal operating current rating that is between about 15-20 amps. Excessive current of 15 about 500-1,000 amps will heat fusible section 50 sufficiently to cause rupture of same and interrupt the circuit. Excessive heat other than that provided by excessive current will melt thermal pellet 16 to interrupt the circuit by operation of 20 the thermal cutoff portion of the - ' in~.~ device.
Although the invention has been shown and described with respect to a pref erred P~ho~ t, it is obvious that equivalent alterations and modif ications will occur to others skilled in the 2 5 art upon the reading and understanding of this specif ication . The present invention i n~ c all such equivalent alterations and modifications, and is limited only by the scope of the claims.
CLCORPOI DCG 185132_~
Claims (5)
1. A combined thermal cutoff and fuse comprising: a thermal cutoff including a housing containing normally closed separable contacts and a thermally responsive device that responds to an elevated temperature for separating said contacts, electrical leads external of said housing for connecting said contacts in an electrical circuit, and one of said leads including a fusible section that ruptures responsive to excessive current.
2. The device of claim 1 wherein said fusible section is integral with said one lead.
3. The device of claim 1 wherein said one lead has a terminal end and said fusible section is located intermediate said terminal end and said housing.
4. The device of claim 1 wherein said device has a normal operating current rating between about 15-20 amps and said fusible section ruptures when subjected to currents between about 500-1,000 amps.
5. A thermal cutoff including a pair of electrical leads connected electrically through said thermal cutoff, said thermal cutoff including a thermally responsive device that responds to an elevated temperature for interrupting the electrical connection between said leads, and one of said leads being fusible responsive to excessive current.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52675995A | 1995-09-12 | 1995-09-12 | |
| US08/526,759 | 1995-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2176323A1 true CA2176323A1 (en) | 1997-03-13 |
Family
ID=24098683
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2176323 Abandoned CA2176323A1 (en) | 1995-09-12 | 1996-05-10 | Thermal cutoff and fuse |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0762455A1 (en) |
| JP (1) | JPH0982192A (en) |
| CA (1) | CA2176323A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090108980A1 (en) | 2007-10-09 | 2009-04-30 | Littelfuse, Inc. | Fuse providing overcurrent and thermal protection |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH103324A (en) * | 1922-12-30 | 1924-02-01 | W Schaufelberger & Co Dr | Safety device against overheating for electrically heated heaters. |
| US2259053A (en) * | 1939-06-06 | 1941-10-14 | Constantine P Xenis | Limiter |
| FR1218795A (en) * | 1959-03-12 | 1960-05-12 | Equip Specialites Electr Sa De | Fuse holder inserting directly into an electrical line |
| US3231966A (en) * | 1962-07-26 | 1966-02-01 | Burndy Corp | Method of manufacturing a one piece fusible connector |
| GB1095264A (en) * | 1964-03-17 | 1967-12-13 | Lucas Industries Ltd | Safety means for electrically heated appliances |
| DE1916596A1 (en) * | 1969-04-01 | 1970-10-15 | Licentia Gmbh | Electrical component, in particular capacitor or resistor |
| DE2002268A1 (en) * | 1970-01-20 | 1971-07-29 | Raukamp & Co | Thermostat for small electrical kitchen appliances and toys |
| GB1252239A (en) * | 1970-02-26 | 1971-11-03 | ||
| GB1356578A (en) * | 1970-09-04 | 1974-06-12 | Beswick Kenneth E Ltd | Switching devices |
| DE3539425A1 (en) * | 1985-11-07 | 1987-05-14 | Limitor Ag | THERMOBI METAL SWITCH |
| US4837547A (en) * | 1987-11-02 | 1989-06-06 | Therm-O-Disc, Incorporated | Thermal cutoff assembly |
| JP2820703B2 (en) * | 1989-01-25 | 1998-11-05 | 株式会社オリエント | Temperature current sensor |
-
1996
- 1996-05-10 CA CA 2176323 patent/CA2176323A1/en not_active Abandoned
- 1996-08-01 JP JP21921296A patent/JPH0982192A/en active Pending
- 1996-08-08 EP EP96630044A patent/EP0762455A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0762455A1 (en) | 1997-03-12 |
| JPH0982192A (en) | 1997-03-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |
Effective date: 19990510 |