EP0076284A1 - Electrical fuse - Google Patents

Electrical fuse

Info

Publication number
EP0076284A1
EP0076284A1 EP82900981A EP82900981A EP0076284A1 EP 0076284 A1 EP0076284 A1 EP 0076284A1 EP 82900981 A EP82900981 A EP 82900981A EP 82900981 A EP82900981 A EP 82900981A EP 0076284 A1 EP0076284 A1 EP 0076284A1
Authority
EP
European Patent Office
Prior art keywords
fuse
fuse element
resistor
wire
connection
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.)
Withdrawn
Application number
EP82900981A
Other languages
German (de)
French (fr)
Inventor
David GEC Industrial Products WATSON
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.)
Kenneth E Beswick Ltd
Original Assignee
Kenneth E Beswick 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 Kenneth E Beswick Ltd filed Critical Kenneth E Beswick Ltd
Publication of EP0076284A1 publication Critical patent/EP0076284A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/36—Means for applying mechanical tension to fusible member
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/02—Details
    • H01H85/04—Fuses, i.e. expendable parts of the protective device, e.g. cartridges
    • H01H85/041—Fuses, i.e. expendable parts of the protective device, e.g. cartridges characterised by the type
    • H01H85/044—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified
    • H01H85/045—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified cartridge type
    • H01H85/0452—General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified cartridge type with parallel side contacts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00—Protective devices in which the current flows through a part of fusible material and this current is interrupted by displacement of the fusible material when this current becomes excessive
    • H01H85/0039—Means for influencing the rupture process of the fusible element
    • H01H85/0047—Heating means
    • H01H85/0052—Fusible element and series heating means or series heat dams

Definitions

  • the present invention relates to electrical fuses and, core particularly, to time lag or time delay fuses.
  • the invention consists in a time delay electrical fuse in ' which a fuse element and a resistor or other electrical circuit component are connected in series and the electrical circuit component serves as a heat source arranged to heat the fuse element.
  • the heat source is a resistor
  • the latter also provides the fuse with a current limiting function.
  • the resistor which may comprise a resistance wire, such as, a copper-nickel or nickel-chromium wire, spirally wound in a multiplicity of turns about an insulating core, typically, a glass fiber core, may be arranged in one or more turns about the fuse element.
  • the resistor may comprise a resistance wire wound upon a support member which may, in turn, enclose the entire fuse element.
  • any other electrical circuit component which produces heat may be used and be so disposed as to heat and assist in the operation of the fuse element.
  • Such other component may comprise a semi-conducting device, for example, a diode, diac thyristor, transistor or metal oxide varistor.
  • the resis ⁇ or or other electrical circuit component is arranged so that convected, radiated and/or conducted heat from the circuit component assists in the operation of the fuse element. This results in a minimum fusing current lower than that which would otherwise be obtained from the fuse element alone.
  • the fuse element behaves in exactly the same manner as would a similar fuse element without the series-connected resistor or other circuit component because the operation is so fast that there is insufficient time for the circuit component to respond. In order to achieve such an overload, however, sufficient voltage must exist to over-ride the current limiting effect of any resistance.
  • the fuse element may comprise a spring member secured in a stressed position by a fusible link or connection.
  • it may comprise a thin fuse wire spirally wound in a multiplicity of turns about an insulating core.
  • the end sections of the fuse wire winding may be shorted cut to leave only a minimum of active, fusible turns at its centre or a similarly wound fuse element may have an eutectic blob affixed to the central active turns.
  • the fuse is mounted in an insulating flame retardant box with contact pins projecting from the box for connecting the fuse to a printed circuit board.
  • the fuse may, alternatively, be mounted within a cylindrical housing suited to mounting in fuse clips or holders or may be mounted in any manner enabling it to conform with known external fuse perameters.
  • Figure 1 is a part-sectional side view of one embodiment of a time delay fuse constructed in accordance with the present invention
  • Figure 2 is a view from above of the fuse of Figure 1
  • Figure 3 is a side view of another embodiment
  • Figure 4 is a view from above of the embodiment of Figure 3
  • Figure 5 is a side view of a still further embodiment
  • Figure 6 is a view from above of the embodiment of Figure 5.
  • Figures 1 and 2 illustrate an electrical fuse including an insulating flame retardant housing or box 1 having contact pins 2, 2' for mounting the fuse on a printed circuit board.
  • the pins- are secured to an insulating base board 10 clipped inside the bottom of the housing and project through the housing bottom.
  • Mounted on the base board within the housing are two conductive posts 3,4 having a fuse element secured between the posts.
  • the fuse element comprises a conductive wire 5 having one end secured to the post 3 and its opposite end soldered at 6 to one end of a spiral spring 7 having its opposite end secured to the post 4.
  • the solder 6 provides the fusible link or connection which melts when an overload current flows through the fuse element.
  • the spring 7 is held under tension by the wire 5 so that melting of the solder connection 6 is followed by rapid separation between the wire and spring to make a clean break in the circuit, thereby avoiding arcing.
  • a current limiting resistor 3 Surrounding the wire 5 in a number of turns adjacent the solder connection 6 is a current limiting resistor 3.
  • the latter may typically comprise a resistance wire, for example, a copper-nickel or nickel- chromium wire, spirally wound in a multiplicity of turns about an insulating core, which may be of glassfibre.
  • One end of the resistance wire is connected to a conductive layer S photo-etched onto the insulating base board 10, this conductive layer providing an electrical connection between the pin 2 and the resistor.
  • the other end of the resistance wire is connected to the post 3 by a photo-etched conductive layer 11 and the post 4 is connected to the pin 2' by a photo-etched conductive layer 12.
  • the resistor 8 is connected in series with the fuse element, which is formed by the wire 5, fusible connection 6 and spring 7, between the contact pins 2,2'.
  • the resistor 8 acts as a heat source which is arranged to heat the fuse element.
  • the fuse is responsive to a minimum fusing current lower than would otherwise be required to fuse the fusible connection 6, alone.
  • the fusible connection 6 behaves in exactly the same manner as would a similar fusible element not provided with the current limiting resistor because the operation is so fast that there is insufficient time for the resistor 8 to respond. In order to achieve such overloads, sufficient voltage must exist to override the current limiting effect of the resistor.
  • Figures 3 and 4 illustrate a second embodiment in which integers common to the previously described embodiment have also been given the same reference numerals.
  • the fuse element comprises a torsion spring wire 20 arranged in cantilever fashion and extending from a short post 3.
  • the spring 20 is turned from its unstressed position (shown in broken lines in Figure 4) and is soldered to the post 2' and 6.
  • the current limiting resistor 8 comprises an insulated resistance wire wound about the post 4 and having one end electrically connected to the post 4. The resistor 8 is thus connected in series with the fuse element, with the connections between the pins 2,2' and the post 3 and other end of the fuse wire being provided by photo-etched conductive layers 9,12.
  • Figures 5 and 6 illustrate a third embodiment in which the current limiting resistor 8 is constructed and arranged similarly to that of the first embodiment whilst the fuse element comprises a leaf spring member 30 connected in series with a conductive wire 5 by a fusible solder connection 6.
  • the leaf spring is secured to a short conductive post 4 and is held under tension by the conductive wire 5 which is secured at its end remote from the fusible connection to the post 3.
  • the various connections between the pins 2,2', the resistor 8 and the posts 3,4 are provided by means of photo-etched conductive layers 9,11,12 formed on the baseboard 10 in the fuse housing.
  • a fuse element comprising a spirally wound fuse wire having its end sections shorted out to leave only a minimum of active fusible turns at the centre, this element being wound around a flexible support of non-conductive material.
  • a fuse element is fully described in the specification of our British Patent No. 1545205.
  • the fuse element may have a eutectic blob affixed to the central active turns.

Landscapes

  • Fuses (AREA)

Abstract

Un fusible electrique a temporisation possede un element de fusible comprenant un fil conducteur (5), un ressort en spirale (7) et une connexion de soudure fusible (6) connectant le fil et le ressort en serie. L'element de fusible est monte entre deux tiges conductrices (3, 4), le ressort etant sous tension. Une resistance (8) entourant le fil adjacent a la connexion fusible (6) est connectee en serie avec l'element de fusible par l'intermediaire de la tige (3). En plus de sa fonction de limitation de l'intensite du courant, la resistance sert egalement de source de chaleur pour chauffer la connexion fusible et contribuer a la fusion de cette derniere, lorsqu'il y a des courants de surcharge prolonges, tout en ameliorant la capacite du fusible a supporter les courants de choc et transitoires. L'element de fusible et la resistance sont disposes dans un boitier isolant (1) et peuvent etre connectes a un circuit exterieur par des broches de contact (2, 2').An electric time delay fuse has a fuse element including a conductive wire (5), a spiral spring (7) and a fusible solder connection (6) connecting the wire and the spring in series. The fuse element is mounted between two conductive rods (3, 4), with the spring under tension. A resistor (8) surrounding the wire adjacent to the fuse connection (6) is connected in series with the fuse element via the rod (3). In addition to its function of limiting the current intensity, the resistance also serves as a heat source to heat the fuse connection and contribute to the melting of the latter, when there are prolonged overload currents, while improving the ability of the fuse to withstand surge and transient currents. The fuse element and the resistor are arranged in an insulating housing (1) and can be connected to an external circuit via contact pins (2, 2').

Description

ELECTRICAL FUSE
The present invention relates to electrical fuses and, core particularly, to time lag or time delay fuses.
It is known to manufacture miniature time delay cartridge fuses using spring-type or spirally wound fuse elements, with either type of fuse element it is possible to achieve sufficiently long operating periods at ten times rated current to withstand switching surges and transients which occur in many circuits. However, when very high energy electrical pulses occur, both these known constructions will operate unless the circuit is "overfused". An "overfused" circuit is one which incorporates a fuse having a rating very much higher than the rating of the circuit to be protected. An object of the present invention is to mitigate the need to "overfuse". To this end, the invention consists in a time delay electrical fuse in' which a fuse element and a resistor or other electrical circuit component are connected in series and the electrical circuit component serves as a heat source arranged to heat the fuse element.
When the heat source is a resistor, the latter also provides the fuse with a current limiting function. The resistor, which may comprise a resistance wire, such as, a copper-nickel or nickel-chromium wire, spirally wound in a multiplicity of turns about an insulating core, typically, a glass fiber core, may be arranged in one or more turns about the fuse element. Alternatively, the resistor may comprise a resistance wire wound upon a support member which may, in turn, enclose the entire fuse element. Instead of a resistor, any other electrical circuit component which produces heat may be used and be so disposed as to heat and assist in the operation of the fuse element. Such other component may comprise a semi-conducting device, for example, a diode, diac thyristor, transistor or metal oxide varistor.
The resisτor or other electrical circuit component is arranged so that convected, radiated and/or conducted heat from the circuit component assists in the operation of the fuse element. This results in a minimum fusing current lower than that which would otherwise be obtained from the fuse element alone. When very high surge or transient overloads occur, the fuse element behaves in exactly the same manner as would a similar fuse element without the series-connected resistor or other circuit component because the operation is so fast that there is insufficient time for the circuit component to respond. In order to achieve such an overload, however, sufficient voltage must exist to over-ride the current limiting effect of any resistance.
The fuse element may comprise a spring member secured in a stressed position by a fusible link or connection. Alternatively, it may comprise a thin fuse wire spirally wound in a multiplicity of turns about an insulating core. The end sections of the fuse wire winding may be shorted cut to leave only a minimum of active, fusible turns at its centre or a similarly wound fuse element may have an eutectic blob affixed to the central active turns.
Conveniently, the fuse is mounted in an insulating flame retardant box with contact pins projecting from the box for connecting the fuse to a printed circuit board. The fuse may, alternatively, be mounted within a cylindrical housing suited to mounting in fuse clips or holders or may be mounted in any manner enabling it to conform with known external fuse perameters.
In order that the present invention may be more readily understood, various embodiments thereof will now be described by way of example, and with reference to the accompanying drawings, in which:-
Figure 1 is a part-sectional side view of one embodiment of a time delay fuse constructed in accordance with the present invention,
Figure 2 is a view from above of the fuse of Figure 1,
Figure 3 is a side view of another embodiment, Figure 4 is a view from above of the embodiment of Figure 3,
Figure 5 is a side view of a still further embodiment, and
Figure 6 is a view from above of the embodiment of Figure 5. Referring to the drawings, Figures 1 and 2 illustrate an electrical fuse including an insulating flame retardant housing or box 1 having contact pins 2, 2' for mounting the fuse on a printed circuit board. The pins- are secured to an insulating base board 10 clipped inside the bottom of the housing and project through the housing bottom. Mounted on the base board within the housing are two conductive posts 3,4 having a fuse element secured between the posts. The fuse element comprises a conductive wire 5 having one end secured to the post 3 and its opposite end soldered at 6 to one end of a spiral spring 7 having its opposite end secured to the post 4. In this embodiment, the solder 6 provides the fusible link or connection which melts when an overload current flows through the fuse element. The spring 7 is held under tension by the wire 5 so that melting of the solder connection 6 is followed by rapid separation between the wire and spring to make a clean break in the circuit, thereby avoiding arcing. Surrounding the wire 5 in a number of turns adjacent the solder connection 6 is a current limiting resistor 3. The latter may typically comprise a resistance wire, for example, a copper-nickel or nickel- chromium wire, spirally wound in a multiplicity of turns about an insulating core, which may be of glassfibre. One end of the resistance wire is connected to a conductive layer S photo-etched onto the insulating base board 10, this conductive layer providing an electrical connection between the pin 2 and the resistor. The other end of the resistance wire is connected to the post 3 by a photo-etched conductive layer 11 and the post 4 is connected to the pin 2' by a photo-etched conductive layer 12.
It will thus be seen that the resistor 8 is connected in series with the fuse element, which is formed by the wire 5, fusible connection 6 and spring 7, between the contact pins 2,2'. In addition to its current limiting function, the resistor 8 acts as a heat source which is arranged to heat the fuse element. As the resistor is located close to the fusible connectio 6, convected and radiated heat from the resistor assists in the operation of this fusible connection. As a result, the fuse is responsive to a minimum fusing current lower than would otherwise be required to fuse the fusible connection 6, alone. However, when the fuse is subjected to very high surge or transient overloads, the fusible connection 6 behaves in exactly the same manner as would a similar fusible element not provided with the current limiting resistor because the operation is so fast that there is insufficient time for the resistor 8 to respond. In order to achieve such overloads, sufficient voltage must exist to override the current limiting effect of the resistor.
Figures 3 and 4 illustrate a second embodiment in which integers common to the previously described embodiment have also been given the same reference numerals. In this second embodiment, the fuse element comprises a torsion spring wire 20 arranged in cantilever fashion and extending from a short post 3. The spring 20 is turned from its unstressed position (shown in broken lines in Figure 4) and is soldered to the post 2' and 6. The current limiting resistor 8 comprises an insulated resistance wire wound about the post 4 and having one end electrically connected to the post 4. The resistor 8 is thus connected in series with the fuse element, with the connections between the pins 2,2' and the post 3 and other end of the fuse wire being provided by photo-etched conductive layers 9,12. Figures 5 and 6 illustrate a third embodiment in which the current limiting resistor 8 is constructed and arranged similarly to that of the first embodiment whilst the fuse element comprises a leaf spring member 30 connected in series with a conductive wire 5 by a fusible solder connection 6. The leaf spring is secured to a short conductive post 4 and is held under tension by the conductive wire 5 which is secured at its end remote from the fusible connection to the post 3. As in the previous embodiments, the various connections between the pins 2,2', the resistor 8 and the posts 3,4 are provided by means of photo-etched conductive layers 9,11,12 formed on the baseboard 10 in the fuse housing.
Whilst particular embodiments have been described, it will be understood that modifications can be made without departing from the scope of the invention as defined by the appended claims. For example, similar results may be achieved by utilising, in place of the various spring type elements, a fuse element comprising a spirally wound fuse wire having its end sections shorted out to leave only a minimum of active fusible turns at the centre, this element being wound around a flexible support of non-conductive material. Such a fuse element is fully described in the specification of our British Patent No. 1545205. The fuse element may have a eutectic blob affixed to the central active turns.

Claims

1. A time delay electrical fuse characterised by a fuse element (5,6,7) and a resistor or other electrical circuit component (8), such as a semi-conductive device, connected in series, and the electrical circuit component serving as a heat source arranged to heat the fuse element.
2. A fuse as claimed in claim 1, characterised in that a resistor (8) is arranged in one or more turns about the fuse element.
3. A fuse as claimed in claim 1, characterised in that the fuse element (6,20) is electrically connected to a conductive support (4) for the element, and the resistor (8) is wound about the conductive support and has its turns insulated from the support.
4. A fuse as claimed in claim 1, 2 or 3, characterise in that the resistor comprises a resistance wire wound in a multiplicity of turns about an insulating core.
5. A fuse as claimed in any one of the preceding claims, characterised in that the fuse element comprises a spring member (7,20,30) secured in a stressed position via a fusible link or connection (6).
6. A fuse as claimed in claim 5, characterised in that the fuse element comprises a spiral spring member (7) and a conductive wire (5) connected in series by the fusible link or connection (6) and mounted under tension.
7. A fuse as claimed in claim 5, characterised in that the fuse element comprises a torsion spring member (20) secured in a stressed position to a conductive support (4) by the fusible link or connection (6).
8. A fuse as claimed in claim 5, characterised in that the fuse element comprises a leaf spring member (30) and a conductive wire (5) connected in series by the fusible link or connection (6), said fuse element being mounted with the wire retaining the spring member in a stressed position.
9. A fuse as claimed in any one of the preceding claims 1 to 4, characterised in that the fuse element comprises a fusible wire spirally wound in a multiplicity of turns about an insulating core.
10. A fuse as claimed in any one of the preceding claims, characterised in that the fuse element and resistor are disposed in an insulating housing (1) having terminal means (2,2') for connecting the fuse element and resistor to an external circuit.
EP82900981A 1981-04-10 1982-04-08 Electrical fuse Withdrawn EP0076284A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8111420 1981-04-10
GB8111420 1981-04-10

Publications (1)

Publication Number Publication Date
EP0076284A1 true EP0076284A1 (en) 1983-04-13

Family

ID=10521091

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82900981A Withdrawn EP0076284A1 (en) 1981-04-10 1982-04-08 Electrical fuse

Country Status (3)

Country Link
EP (1) EP0076284A1 (en)
IT (1) IT1235568B (en)
WO (1) WO1982003724A1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3234826A1 (en) * 1982-09-21 1984-03-22 Loewe Opta Gmbh, 8640 Kronach Thermal fuse element
DE102006036598A1 (en) * 2006-04-26 2007-10-31 Dehn + Söhne Gmbh + Co. Kg Separating device dimensioning method for over-voltage protection, involves adjusting force distribution so that small force acts on soldered joint of switching guide, and large force executes switching movement during soldering process
DE102008025917A1 (en) 2007-06-04 2009-01-08 Littelfuse, Inc., Des Plaines High voltage fuse

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE542637A (en) *
DE498994C (en) * 1930-08-21 Siemens & Halske Akt Ges Melting cartridge with one or more heating elements soldered together by means of an easily meltable solder, especially for telephone systems
US1792299A (en) * 1930-04-18 1931-02-10 Gen Electric Thermal cut-out
US2084495A (en) * 1935-11-06 1937-06-22 Schweitzer & Conrad Inc Fuse
DE699140C (en) * 1938-01-22 1940-11-22 Siemens Schuckertwerke Akt Ges Overcurrent carrier short-circuit-proof fuse cartridge
FR968991A (en) * 1948-07-06 1950-12-11 Fabrication Electro Radiotechn Thermal flywheel fuse circuit breaker
US3246105A (en) * 1963-02-06 1966-04-12 Mc Graw Edison Co Protector for electric circuits
NL134303C (en) * 1967-05-24
GB1545205A (en) * 1975-05-22 1979-05-02 Beswick Ltd K Electric fuse-links
GB1582054A (en) * 1978-05-26 1980-12-31 Beswick Kenneth E Ltd Fusible power resistors

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8203724A1 *

Also Published As

Publication number Publication date
IT8246821A0 (en) 1982-04-13
IT1235568B (en) 1992-09-11
WO1982003724A1 (en) 1982-10-28

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Inventor name: WATSON, DAVIDGEC INDUSTRIAL PRODUCTS