GB2096844A - Electrical fuse - Google Patents

Electrical fuse Download PDF

Info

Publication number
GB2096844A
GB2096844A GB8210584A GB8210584A GB2096844A GB 2096844 A GB2096844 A GB 2096844A GB 8210584 A GB8210584 A GB 8210584A GB 8210584 A GB8210584 A GB 8210584A GB 2096844 A GB2096844 A GB 2096844A
Authority
GB
United Kingdom
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Withdrawn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
GB8210584A
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.)
BESWICK KENNETH E Ltd
Original Assignee
BESWICK KENNETH E 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
Priority to GB8111420 priority Critical
Application filed by BESWICK KENNETH E LTD filed Critical BESWICK KENNETH E LTD
Priority to GB8210584A priority patent/GB2096844A/en
Publication of GB2096844A publication Critical patent/GB2096844A/en
Application status is Withdrawn legal-status Critical

Links

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00Protective 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
    • H01H85/02Details
    • H01H85/36Means for applying mechanical tension to fusible member
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00Protective 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
    • H01H85/02Details
    • H01H85/04Fuses, i.e. expendable parts of the protective device, e.g. cartridges
    • H01H85/041Fuses, i.e. expendable parts of the protective device, e.g. cartridges characterised by the type
    • H01H85/044General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified
    • H01H85/045General constructions or structure of low voltage fuses, i.e. below 1000 V, or of fuses where the applicable voltage is not specified cartridge type
    • H01H85/0452General 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
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H85/00Protective 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
    • H01H85/0039Means for influencing the rupture process of the fusible element
    • H01H85/0047Heating means
    • H01H85/0052Fusible element and series heating means or series heat dams

Abstract

A time delay electrical fuse has a fuse element comprising a conductive wire 5, a spiral spring 7 and a fusible solder connection 6 connecting the wire and spring in series. The fuse element is mounted between two conductive posts 3, 4 with the spring under tension. Surrounding the wire adjacent the fusible connection 6 is a resistor 8 which is connected in series with the fuse element via the post 3. In addition to its current limiting function, the resistor also serves as a heat source for heating the fusible connection and assisting fusing of the latter upon sustained overload currents, whilst improving the fuse's ability to withstand surge and transient currents. <IMAGE>

Description

SPECIFICATION Electrical fuse The present invention relates to electrical fuses and, more 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, time 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 funciton. The resistor, which may comprise a resistance wire, such as, a coppernickel or nickelchromium 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 semiconducting device, for example, a diode, diac thyristor, transistor or metal oxide varistor.

The resistor 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 seriesconnected 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 out 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 parameters.

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 poses 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 8. The latter may typically comprise a resistance wire, for example, a coppernickel or nickel-chromium wire, spirally wound in a multiplicity of turns about an insulating core, which may be of glass-fibre. One end of the resistance wire is connected to a conductive layer 9 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 1 2.

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 connection 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 canti-lever 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 pose 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 base board 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. 1 545205.

The fuse element may have a eutectic blob affixed to the central active turns.

Claims (12)

1 A time delay electrical fuse comprising a fuse element and a resistor or other electrical circuit component 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, in which a resistor is arranged in one or more turns about the fuse element.
3. A fuse as claimed in claim 1, in which the fuse element is electrically connected to a conductive support for the element, and the resistor 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, in which 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, in which the fuse element comprises a spring member secured in a stressed position via a fusible link or connection.
6. A fuse as claimed in claim 5, in which the fuse element comprises a spiral spring member and a conductive wire connected in series by the fusible link or connection and mounted under tension.
7. A fuse as claimed in claim 5, in which the fuse element comprises a torsion spring member secured in a stressed position to a conductive support by the fusible link or connection.
8. A fuse as claimed in claim 5, in which the fuse element comprises a leaf spring member and a conductive wire connected in series by the fusible link or connection, 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, in which 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, in which the fuse element and resistor are disposed nan insulating housing having terminal means for connecting the fuse element and resistor to an external circuit.
11. A time delay electrical fuse constructed substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.
12. A time delay electrical fuse constructed substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.
1 3. A time delay electrical fuse constructed substantially as hereinbefore described with reference to Figures 5 and 6 of the accompanying drawings.
GB8210584A 1981-04-10 1982-04-08 Electrical fuse Withdrawn GB2096844A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB8111420 1981-04-10
GB8210584A GB2096844A (en) 1981-04-10 1982-04-08 Electrical fuse

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8210584A GB2096844A (en) 1981-04-10 1982-04-08 Electrical fuse

Publications (1)

Publication Number Publication Date
GB2096844A true GB2096844A (en) 1982-10-20

Family

ID=26279121

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8210584A Withdrawn GB2096844A (en) 1981-04-10 1982-04-08 Electrical fuse

Country Status (1)

Country Link
GB (1) GB2096844A (en)

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2182811A (en) * 1985-11-08 1987-05-20 Cooper Ind Inc Time lag electrical fuse
WO1990011608A1 (en) * 1989-03-17 1990-10-04 Skyline Holding Ag Fuse
US6813983B2 (en) 2000-09-29 2004-11-09 Sd3, Llc Power saw with improved safety system
US6826988B2 (en) 2000-09-29 2004-12-07 Sd3, Llc Miter saw with improved safety system
US7100483B2 (en) * 2000-08-14 2006-09-05 Sd3, Llc Firing subsystem for use in a fast-acting safety system
US7681479B2 (en) 2000-08-14 2010-03-23 Sd3, Llc Motion detecting system for use in a safety system for power equipment
US7707920B2 (en) 2003-12-31 2010-05-04 Sd3, Llc Table saws with safety systems
US7712403B2 (en) 2001-07-03 2010-05-11 Sd3, Llc Actuators for use in fast-acting safety systems
US7784507B2 (en) 2000-09-29 2010-08-31 Sd3, Llc Router with improved safety system
US7789002B2 (en) 2000-09-29 2010-09-07 Sd3, Llc Table saw with improved safety system
US7788999B2 (en) 1999-10-01 2010-09-07 Sd3, Llc Brake mechanism for power equipment
US7827890B2 (en) 2004-01-29 2010-11-09 Sd3, Llc Table saws with safety systems and systems to mount and index attachments
US7832314B2 (en) 2000-08-14 2010-11-16 Sd3, Llc Brake positioning system
US7836804B2 (en) 2003-08-20 2010-11-23 Sd3, Llc Woodworking machines with overmolded arbors
US7895927B2 (en) 1999-10-01 2011-03-01 Sd3, Llc Power equipment with detection and reaction systems
CN101427327B (en) 2006-04-26 2011-04-06 德恩及索恩两合股份有限公司 Process for the dimensioning of an separation device of overvoltage discharger
US7921754B2 (en) 2000-08-14 2011-04-12 Sd3, Llc Logic control for fast-acting safety system
US7991503B2 (en) 2003-12-31 2011-08-02 Sd3, Llc Detection systems for power equipment
US8061245B2 (en) 2000-09-29 2011-11-22 Sd3, Llc Safety methods for use in power equipment
US8065943B2 (en) 2000-09-18 2011-11-29 Sd3, Llc Translation stop for use in power equipment
US8100039B2 (en) 2000-08-14 2012-01-24 Sd3, Llc Miter saw with safety system
US8186255B2 (en) 2000-09-29 2012-05-29 Sd3, Llc Contact detection system for power equipment
US8459157B2 (en) 2003-12-31 2013-06-11 Sd3, Llc Brake cartridges and mounting systems for brake cartridges
US9724840B2 (en) 1999-10-01 2017-08-08 Sd3, Llc Safety systems for power equipment
US9927796B2 (en) 2001-05-17 2018-03-27 Sawstop Holding Llc Band saw with improved safety system

Cited By (47)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2182811A (en) * 1985-11-08 1987-05-20 Cooper Ind Inc Time lag electrical fuse
GB2182811B (en) * 1985-11-08 1990-09-19 Cooper Ind Inc Time lag electrical fuse
WO1990011608A1 (en) * 1989-03-17 1990-10-04 Skyline Holding Ag Fuse
AU640917B2 (en) * 1989-03-17 1993-09-09 Skyline Holding Ag Fuse
US8408106B2 (en) 1999-10-01 2013-04-02 Sd3, Llc Method of operating power equipment with detection and reaction systems
US9969014B2 (en) 1999-10-01 2018-05-15 Sawstop Holding Llc Power equipment with detection and reaction systems
US7895927B2 (en) 1999-10-01 2011-03-01 Sd3, Llc Power equipment with detection and reaction systems
US8196499B2 (en) 1999-10-01 2012-06-12 Sd3, Llc Power equipment with detection and reaction systems
US9925683B2 (en) 1999-10-01 2018-03-27 Sawstop Holding Llc Table saws
US9724840B2 (en) 1999-10-01 2017-08-08 Sd3, Llc Safety systems for power equipment
US9522476B2 (en) 1999-10-01 2016-12-20 Sd3, Llc Power equipment with detection and reaction systems
US10335972B2 (en) 1999-10-01 2019-07-02 Sawstop Holding Llc Table Saws
US7788999B2 (en) 1999-10-01 2010-09-07 Sd3, Llc Brake mechanism for power equipment
US8291797B2 (en) 1999-10-01 2012-10-23 Sd3, Llc Table saw with improved safety system
US9038515B2 (en) 2000-08-14 2015-05-26 Sd3, Llc Logic control for fast-acting safety system
US7832314B2 (en) 2000-08-14 2010-11-16 Sd3, Llc Brake positioning system
US8522655B2 (en) 2000-08-14 2013-09-03 Sd3, Llc Logic control for fast-acting safety system
US7681479B2 (en) 2000-08-14 2010-03-23 Sd3, Llc Motion detecting system for use in a safety system for power equipment
US7100483B2 (en) * 2000-08-14 2006-09-05 Sd3, Llc Firing subsystem for use in a fast-acting safety system
US8191450B2 (en) 2000-08-14 2012-06-05 Sd3, Llc Power equipment with detection and reaction systems
US7921754B2 (en) 2000-08-14 2011-04-12 Sd3, Llc Logic control for fast-acting safety system
US8151675B2 (en) 2000-08-14 2012-04-10 Sd3, Llc Logic control for fast-acting safety system
US8100039B2 (en) 2000-08-14 2012-01-24 Sd3, Llc Miter saw with safety system
US8065943B2 (en) 2000-09-18 2011-11-29 Sd3, Llc Translation stop for use in power equipment
US6826988B2 (en) 2000-09-29 2004-12-07 Sd3, Llc Miter saw with improved safety system
US8061245B2 (en) 2000-09-29 2011-11-22 Sd3, Llc Safety methods for use in power equipment
US7784507B2 (en) 2000-09-29 2010-08-31 Sd3, Llc Router with improved safety system
US7789002B2 (en) 2000-09-29 2010-09-07 Sd3, Llc Table saw with improved safety system
US8186255B2 (en) 2000-09-29 2012-05-29 Sd3, Llc Contact detection system for power equipment
US6813983B2 (en) 2000-09-29 2004-11-09 Sd3, Llc Power saw with improved safety system
US9927796B2 (en) 2001-05-17 2018-03-27 Sawstop Holding Llc Band saw with improved safety system
US7712403B2 (en) 2001-07-03 2010-05-11 Sd3, Llc Actuators for use in fast-acting safety systems
US7836804B2 (en) 2003-08-20 2010-11-23 Sd3, Llc Woodworking machines with overmolded arbors
US8459157B2 (en) 2003-12-31 2013-06-11 Sd3, Llc Brake cartridges and mounting systems for brake cartridges
US8489223B2 (en) 2003-12-31 2013-07-16 Sd3, Llc Detection systems for power equipment
US7866239B2 (en) 2003-12-31 2011-01-11 Sd3, Llc Elevation mechanism for table saws
US7707920B2 (en) 2003-12-31 2010-05-04 Sd3, Llc Table saws with safety systems
US7827893B2 (en) 2003-12-31 2010-11-09 Sd3, Llc Elevation mechanism for table saws
US7991503B2 (en) 2003-12-31 2011-08-02 Sd3, Llc Detection systems for power equipment
US8122807B2 (en) 2003-12-31 2012-02-28 Sd3, Llc Table saws with safety systems
US9623498B2 (en) 2003-12-31 2017-04-18 Sd3, Llc Table saws
US8498732B2 (en) 2003-12-31 2013-07-30 Sd3, Llc Detection systems for power equipment
US8087438B2 (en) 2003-12-31 2012-01-03 Sd3, Llc Detection systems for power equipment
US8505424B2 (en) 2004-01-29 2013-08-13 Sd3, Llc Table saws with safety systems and systems to mount and index attachments
US7827890B2 (en) 2004-01-29 2010-11-09 Sd3, Llc Table saws with safety systems and systems to mount and index attachments
US10052786B2 (en) 2004-01-29 2018-08-21 Sawstop Holding Llc Table saws with safety systems and systems to mount and index attachments
CN101427327B (en) 2006-04-26 2011-04-06 德恩及索恩两合股份有限公司 Process for the dimensioning of an separation device of overvoltage discharger

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)