CA1038427A - Fuse element for a cartridge type fuse - Google Patents
Fuse element for a cartridge type fuseInfo
- Publication number
- CA1038427A CA1038427A CA252,685A CA252685A CA1038427A CA 1038427 A CA1038427 A CA 1038427A CA 252685 A CA252685 A CA 252685A CA 1038427 A CA1038427 A CA 1038427A
- Authority
- CA
- Canada
- Prior art keywords
- trough
- strip
- fuse element
- fuse
- high resistance
- 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
- 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
- H01H85/05—Component parts thereof
- H01H85/055—Fusible members
- H01H85/08—Fusible members characterised by the shape or form of the fusible member
- H01H85/10—Fusible members characterised by the shape or form of the fusible member with constriction for localised fusing
Abstract
Abstract:
A fusible strip of electrically-conducting metal, for incorporation into a cartridge fuse, is shaped at a location along its length to define a recess or trough to accommodate an applied mass of low-melting paint metal or alloy, and the strip is of reduced cross-section to form a high resistance zone or zones immediately adjacent one or both ends of the recess or trough.
A fusible strip of electrically-conducting metal, for incorporation into a cartridge fuse, is shaped at a location along its length to define a recess or trough to accommodate an applied mass of low-melting paint metal or alloy, and the strip is of reduced cross-section to form a high resistance zone or zones immediately adjacent one or both ends of the recess or trough.
Description
DP 26.4.76 .' ~ ' .
. ~ r!
~, 1038~Z7 :
This invention concerns fuse elements of the kind .
which are i~corporated in so-called cartridge fuses. .
It is advantageous, in fu~e practice, to design a fu3e that can withstand relati~ely high values of current :
: surge in the one to ten second region of the fuse time/
current characteristic, and yet which has a relati~ely ~
low value of minimum fusing currentO - .
~ . .
Such a fuse can be used in the protection of electrical apparatus (such as an electric motor) which in its normal operation, produce~ non~injurious surges :
of current of short duration, without unwanted fuse .
blowing. A fuse of this type avoids the need for ex- .
cessire over-fusing, and enables close protection to be given to the associated cables supplying the apparatu .
: A~ object of the in~ention is to provide such a fuse.
With this ob~ect in view, the present invention provides a fuse element comprising a strip o~ silver, copper or -other suitable electrically-conductive metal, said strip ha~ing a substantial mass of a lower melting point ~etal or metal alloy (for example, tin or a tin/lead al~oy) : located in a trough~ formed in the strip,and located at any ~uitable point along the length of the strip but preferably approximately at the centre, the ~trip beine reduced in section, to create a relatively high resistance zone, i~mediately adjacent to one or both of the bound-aries of the trough.
With such an element, at minimum fusing current suff~cient heat is produced in t~e reduced section or
. ~ r!
~, 1038~Z7 :
This invention concerns fuse elements of the kind .
which are i~corporated in so-called cartridge fuses. .
It is advantageous, in fu~e practice, to design a fu3e that can withstand relati~ely high values of current :
: surge in the one to ten second region of the fuse time/
current characteristic, and yet which has a relati~ely ~
low value of minimum fusing currentO - .
~ . .
Such a fuse can be used in the protection of electrical apparatus (such as an electric motor) which in its normal operation, produce~ non~injurious surges :
of current of short duration, without unwanted fuse .
blowing. A fuse of this type avoids the need for ex- .
cessire over-fusing, and enables close protection to be given to the associated cables supplying the apparatu .
: A~ object of the in~ention is to provide such a fuse.
With this ob~ect in view, the present invention provides a fuse element comprising a strip o~ silver, copper or -other suitable electrically-conductive metal, said strip ha~ing a substantial mass of a lower melting point ~etal or metal alloy (for example, tin or a tin/lead al~oy) : located in a trough~ formed in the strip,and located at any ~uitable point along the length of the strip but preferably approximately at the centre, the ~trip beine reduced in section, to create a relatively high resistance zone, i~mediately adjacent to one or both of the bound-aries of the trough.
With such an element, at minimum fusing current suff~cient heat is produced in t~e reduced section or
- 2 -" - . '. , : ,; ' ,: .: . .
~ , , DP 26.4.76 "'~ . 0 ' i038427 sections, if the current i~ su~tained e~entually to osuse melting of the low melting point metal or alloy in the ~' ad~ac0nt troughO The metal of the strip~ in contact with this molten metal, then diffuseq into the molten metal and the strip becomes severed in this region of ;:
reduced section~ thereby to interrupt the electric circuit in which the element i8 di8poged.
At currentq in the region of two to four times the fu~e'~ minimum fusing current, the reduoed sections again produce heat 9 but the quantity of metal or alloy in the trough immediately adjacent to the reduced section or oections provides a ready means o~ absorbing the heat, and the meltlng of the trough metal and of the adjacent reduced section i9 delayed ~or a significant period of time, so that fusing does not occur i~ such currents are maintained only ~or a short period of ti~e. -The in~ention will be described ~urther, by way of example, with reference to the accompanying drawings, in which:
j 20 Fig. 1 i9 an enlarged plan view o~ a first embodiment o~ the ~use element of the in~ention;
Fig. 2 i8 an ele~ation of the fuse element of Fig. 1;
Fig. 3 i8 sectional elevation, to a reduced scale compared with Figs. 1 and 2, illustrating a cartridge fuse incorporating the fuse element o~ Figs. 1 and 2;
~ , , DP 26.4.76 "'~ . 0 ' i038427 sections, if the current i~ su~tained e~entually to osuse melting of the low melting point metal or alloy in the ~' ad~ac0nt troughO The metal of the strip~ in contact with this molten metal, then diffuseq into the molten metal and the strip becomes severed in this region of ;:
reduced section~ thereby to interrupt the electric circuit in which the element i8 di8poged.
At currentq in the region of two to four times the fu~e'~ minimum fusing current, the reduoed sections again produce heat 9 but the quantity of metal or alloy in the trough immediately adjacent to the reduced section or oections provides a ready means o~ absorbing the heat, and the meltlng of the trough metal and of the adjacent reduced section i9 delayed ~or a significant period of time, so that fusing does not occur i~ such currents are maintained only ~or a short period of ti~e. -The in~ention will be described ~urther, by way of example, with reference to the accompanying drawings, in which:
j 20 Fig. 1 i9 an enlarged plan view o~ a first embodiment o~ the ~use element of the in~ention;
Fig. 2 i8 an ele~ation of the fuse element of Fig. 1;
Fig. 3 i8 sectional elevation, to a reduced scale compared with Figs. 1 and 2, illustrating a cartridge fuse incorporating the fuse element o~ Figs. 1 and 2;
- 3 -l DP 2704.76 J ~ '1,,) '_,~
Figs. 4 and 5 are respectively a plan view and a cor:responding elevation, illustrating a second embodiment of the fuse element of the invention;
Fi~o 6 is a sectional elevation, to a reduced ~cale compared with ~igs. 4 and 5, illu~trating a cartrldge fuse lnoorporating two of the fu~e elements of Figs. 4 and 5;
. Fig~o 7 and 8 are respectively a fragmentary plan and ¦ a oorre3ponding elevation, showin~ a third embodiment of the fuse element of the invention;
~ig~. 9 and 10 are views ~imilar to Fig~. 7 and 8 but showine a fourth embodiment;
.. Figs. 11 and 12 are view-R similar to Figs. 7 and 8 but ~howin~ a flrth embodiment, - -~
. Fi~so 13 and 14 are views si~ilar to Figs. 7 and 8 but showing a si~th embodiment; and Fies. 15 and 16 are views ~i~ilar to Figs. 7 and 8 but showing a seventh embodiment.
In the various figures, similar reYerence numeral~
have been allocated to similar parts.
1 20 The practical~embodiment of the fuse element illustrated in Figs. 1 and 2 comprises. a strip 10 of electrically-conductive material, conventionally silver, whose thick-ness t may be from one-and-a-half thousandths to ten-thousandths of an inch, and whose width 1~ may be, for d - 4-ln3s427 1 example, from one-sixtee~h to o~e-~uarter of an inch. Approx-imately at its middle, the strip 10 has a mass 11 of low melting point metal or alloy, e.g. a tin/lead alloy, located thereo~ in a trough 12 formed in the strip 10 by bending the latter.
At each side of the trough 12, immediatel~ adjacent thereto, the strip 10 is reduced in section to create relatively high resistance zones, by aligned notches having been cut into the strip 10 from opposite longitudinal edges thereof, these notches being of width x and leaving narrow necks 13 of width b approximately one third of the width W of the strip 10.
In addition to the notches defining the necks 13 immediately adjacent the mass 11, further notches, of width y, are formed in the strip 10 to define necks 15, 15 and 16, 16, of width a, which are successively spaced away from the mass 11~ - -Fig. 3 shows a cartridge fuse incorporating one of the elements of Figs. 1 and 2. The element, indicated generally by the reference numeral 17, is enclosed within a ceramic tube 18 having a particulate arc-quenching filling 19, for example of iron-free silica sand, and inner end caps 20 with which the respective ends of the element 17 are connected. Respective outer end caps 21 fit snugly over the inner end caps 20 so as to be electrically-conducting contact therewith whilst at the same time retaining respective protective discs 22, for example of asbestos, across the respective inner end caps 20.
- . : . - .. . ... . .
1 In suc~ a cartridge fuse, a fusible element 17 having the following dimensions will give a ~use of 20 ampere rating:
a = 0.030" t = O.OOZ8"
b = 0.030" C = 0.085"
y = 0.030~' D = 0.218"
x = 0.030" W = 0.090"
Precisely the same configuration of fusible element, of substantially similar dimensions, but different thicknesses can be used to give fuses of diffexent ratings Thus,for a 25 ampere fuse one would, for example, use dimensions as tabulated above but with the strip thickness altered to t = 0.0048" and for a 30 ampere fuse one would use a strip of thickness t = 0~.0065".
In the case of the 30 ampere fuse, the minimum fusing current is 40 amperes and the ten second current is 72 amperes;
the minimum fusing currents and ten second currents of the 20 and 25 ampere rated fuses are comparable. .
The reduced sections or necks 15, 16 of the element, having dimensions a and y, constitute short cicuit regions of the elément and in use deal with higher values of current, in excess of about four times the fuse's minimum fusing current. The portion of the strip 10 consisting of the necks 13, trough 12 ::
and mass 11 and having the dimensions x, b, C and D constitutes an overload region. It will be observed that the reduced-section : necks 13, of dimensions x and b, are each disposed immediately adjacent the respective boundary of the trough 12 whose dimensions are indicated at C and D and which is occupied by the mass 11 of low melting point metal or alloy which is shaded in /;:
the figures.
'.' '.
. ` '''.~ ' `
.
: ' ' ' .
1~38427 t The invention is not restricted to elements of the form shown in Figs. 1 and 2, and having the precise dimensions indicated above, which may be varied. The dimension x could also be made longer or shorter than dimension y and dimension b could be made wider than dimension a. Also, within practical limits, it is an advantage to make the dimensions C and D as great as possible.
Other variations are possible. Thus, as shown in Figs.
Figs. 4 and 5 are respectively a plan view and a cor:responding elevation, illustrating a second embodiment of the fuse element of the invention;
Fi~o 6 is a sectional elevation, to a reduced ~cale compared with ~igs. 4 and 5, illu~trating a cartrldge fuse lnoorporating two of the fu~e elements of Figs. 4 and 5;
. Fig~o 7 and 8 are respectively a fragmentary plan and ¦ a oorre3ponding elevation, showin~ a third embodiment of the fuse element of the invention;
~ig~. 9 and 10 are views ~imilar to Fig~. 7 and 8 but showine a fourth embodiment;
.. Figs. 11 and 12 are view-R similar to Figs. 7 and 8 but ~howin~ a flrth embodiment, - -~
. Fi~so 13 and 14 are views si~ilar to Figs. 7 and 8 but showing a si~th embodiment; and Fies. 15 and 16 are views ~i~ilar to Figs. 7 and 8 but showing a seventh embodiment.
In the various figures, similar reYerence numeral~
have been allocated to similar parts.
1 20 The practical~embodiment of the fuse element illustrated in Figs. 1 and 2 comprises. a strip 10 of electrically-conductive material, conventionally silver, whose thick-ness t may be from one-and-a-half thousandths to ten-thousandths of an inch, and whose width 1~ may be, for d - 4-ln3s427 1 example, from one-sixtee~h to o~e-~uarter of an inch. Approx-imately at its middle, the strip 10 has a mass 11 of low melting point metal or alloy, e.g. a tin/lead alloy, located thereo~ in a trough 12 formed in the strip 10 by bending the latter.
At each side of the trough 12, immediatel~ adjacent thereto, the strip 10 is reduced in section to create relatively high resistance zones, by aligned notches having been cut into the strip 10 from opposite longitudinal edges thereof, these notches being of width x and leaving narrow necks 13 of width b approximately one third of the width W of the strip 10.
In addition to the notches defining the necks 13 immediately adjacent the mass 11, further notches, of width y, are formed in the strip 10 to define necks 15, 15 and 16, 16, of width a, which are successively spaced away from the mass 11~ - -Fig. 3 shows a cartridge fuse incorporating one of the elements of Figs. 1 and 2. The element, indicated generally by the reference numeral 17, is enclosed within a ceramic tube 18 having a particulate arc-quenching filling 19, for example of iron-free silica sand, and inner end caps 20 with which the respective ends of the element 17 are connected. Respective outer end caps 21 fit snugly over the inner end caps 20 so as to be electrically-conducting contact therewith whilst at the same time retaining respective protective discs 22, for example of asbestos, across the respective inner end caps 20.
- . : . - .. . ... . .
1 In suc~ a cartridge fuse, a fusible element 17 having the following dimensions will give a ~use of 20 ampere rating:
a = 0.030" t = O.OOZ8"
b = 0.030" C = 0.085"
y = 0.030~' D = 0.218"
x = 0.030" W = 0.090"
Precisely the same configuration of fusible element, of substantially similar dimensions, but different thicknesses can be used to give fuses of diffexent ratings Thus,for a 25 ampere fuse one would, for example, use dimensions as tabulated above but with the strip thickness altered to t = 0.0048" and for a 30 ampere fuse one would use a strip of thickness t = 0~.0065".
In the case of the 30 ampere fuse, the minimum fusing current is 40 amperes and the ten second current is 72 amperes;
the minimum fusing currents and ten second currents of the 20 and 25 ampere rated fuses are comparable. .
The reduced sections or necks 15, 16 of the element, having dimensions a and y, constitute short cicuit regions of the elément and in use deal with higher values of current, in excess of about four times the fuse's minimum fusing current. The portion of the strip 10 consisting of the necks 13, trough 12 ::
and mass 11 and having the dimensions x, b, C and D constitutes an overload region. It will be observed that the reduced-section : necks 13, of dimensions x and b, are each disposed immediately adjacent the respective boundary of the trough 12 whose dimensions are indicated at C and D and which is occupied by the mass 11 of low melting point metal or alloy which is shaded in /;:
the figures.
'.' '.
. ` '''.~ ' `
.
: ' ' ' .
1~38427 t The invention is not restricted to elements of the form shown in Figs. 1 and 2, and having the precise dimensions indicated above, which may be varied. The dimension x could also be made longer or shorter than dimension y and dimension b could be made wider than dimension a. Also, within practical limits, it is an advantage to make the dimensions C and D as great as possible.
Other variations are possible. Thus, as shown in Figs.
4 and 5, just a single neck 13 may be provided to one side only of the trough 12, and, as shown in Fig. 6, two of the fusible elements, indicated by the numerals 23, may be incorporated into a cartridge fuse composed of substantially similar components ;~
to those of the fuse of Fig. 3 so as to be spaced apart and provide parallel current paths bet~een the two outer end caps 21.
In such a cartridge fuse, two fusible elements 23 having the following dimensions will give a fuse 40 ampere rating: , :-a = 0.061" t = 0.0018"
b = 0.080" C = 0.093"
y = 0.030" D = 0.125"
x = 0.125" - W = 0.180"
As already described above in relation to Fig. 3, higher fuse ratings are achieved simply by using thicker strips, whilst keeping all the other dimensions the same. This may be exemplified by the following table:
. .
1~38~,27 Fuse ra~ihg Thickness- t of the two " fusible elem-ents 23 the-r of 45 amperes 0.0026"
50 amperes 0.003"
60 amperes 0.004"
amperes 0.0045"
amperes 0.0055"
amperes 0.0065"
100 amperes 0.0085"
' lO In the case of the 60 ampere fuse according to the above table, the minimum fusing current is 78 amperes, with a ten second current of the order of 200 amperes, and the minimum -~
fusing currents and ten second currents of the other fuses are comparable.
The reduction in the element section both adjacent the trough 12 and spaced therefrom may be accomplished by any , of the means normally used in fuse practice; for example by use of necks (as in the elements of Figs. 1 and 2 and F}gs.~ ~ and
to those of the fuse of Fig. 3 so as to be spaced apart and provide parallel current paths bet~een the two outer end caps 21.
In such a cartridge fuse, two fusible elements 23 having the following dimensions will give a fuse 40 ampere rating: , :-a = 0.061" t = 0.0018"
b = 0.080" C = 0.093"
y = 0.030" D = 0.125"
x = 0.125" - W = 0.180"
As already described above in relation to Fig. 3, higher fuse ratings are achieved simply by using thicker strips, whilst keeping all the other dimensions the same. This may be exemplified by the following table:
. .
1~38~,27 Fuse ra~ihg Thickness- t of the two " fusible elem-ents 23 the-r of 45 amperes 0.0026"
50 amperes 0.003"
60 amperes 0.004"
amperes 0.0045"
amperes 0.0055"
amperes 0.0065"
100 amperes 0.0085"
' lO In the case of the 60 ampere fuse according to the above table, the minimum fusing current is 78 amperes, with a ten second current of the order of 200 amperes, and the minimum -~
fusing currents and ten second currents of the other fuses are comparable.
The reduction in the element section both adjacent the trough 12 and spaced therefrom may be accomplished by any , of the means normally used in fuse practice; for example by use of necks (as in the elements of Figs. 1 and 2 and F}gs.~ ~ and
5~, holes 24 trough the strip 10 (Figs; i and 8~ or ii~denting the strip,l0-,(as ,at 25 in Figs. 9 and 10). Just as the necks 13 may be provided either at both side or one side only of the trough 3~2! '~
so can the holes 24 or indentations 25. ' The mass 11 of low melting point metal or alloy may be contained in a trough or troughs of configuration different , ,~
from those discussed ln relation to Figs. 1 to 10. One such ~
possibility is shown in Figs. 11 and 12 which illustrate a -;
trough 26 of rectangular section. Figs. 13 and 14 show an arrangement of a circular rod-like mass 11 oE alloy located in a ';
semi-circular trough 12.
~"
--8-- ~
., ' ,',, :
~,~J,''', ~
1~38~27 1 In the embodiment of Figs. 15 and 16 of the drawings, two troughs 27 and 28 are provided, these being spaced apart by a distance just sufficient to accomodate a single neck 13 therebetween. In this embodiment, of course, further reduced sections, e.g. in the form of necks 13, holes 17 or indentations ~-18 may be provided at one or both of the boundaries, remote from the illustrated neck 13, of the troughs 27, 28.
In the embodiment of Figs. 1 and 2, the necks 15 and 16 spaced away from the trough 12, and providing regions which melt rapidly upon occurrence of short-circuit currents, may be more or fewer in number than in the illustrated case and can, of course, be omitted. Naturally such necks or similar reduced-section regions may be provided, if desired, in each of the elements of Figs. 4 to 16.
.
~0 ~.
- , .
,.:
_g_ ~. ' ".
:
.
, ' ' ' ' ': : ~
so can the holes 24 or indentations 25. ' The mass 11 of low melting point metal or alloy may be contained in a trough or troughs of configuration different , ,~
from those discussed ln relation to Figs. 1 to 10. One such ~
possibility is shown in Figs. 11 and 12 which illustrate a -;
trough 26 of rectangular section. Figs. 13 and 14 show an arrangement of a circular rod-like mass 11 oE alloy located in a ';
semi-circular trough 12.
~"
--8-- ~
., ' ,',, :
~,~J,''', ~
1~38~27 1 In the embodiment of Figs. 15 and 16 of the drawings, two troughs 27 and 28 are provided, these being spaced apart by a distance just sufficient to accomodate a single neck 13 therebetween. In this embodiment, of course, further reduced sections, e.g. in the form of necks 13, holes 17 or indentations ~-18 may be provided at one or both of the boundaries, remote from the illustrated neck 13, of the troughs 27, 28.
In the embodiment of Figs. 1 and 2, the necks 15 and 16 spaced away from the trough 12, and providing regions which melt rapidly upon occurrence of short-circuit currents, may be more or fewer in number than in the illustrated case and can, of course, be omitted. Naturally such necks or similar reduced-section regions may be provided, if desired, in each of the elements of Figs. 4 to 16.
.
~0 ~.
- , .
,.:
_g_ ~. ' ".
:
.
, ' ' ' ' ': : ~
Claims (9)
1. A fuse element comprising a strip of silver, copper or other suitable electrically-conductive metal, said strip having a substantial mass of a lower melting point metal or metal alloy located in a trough formed in the strip, the strip being reduced in section, to create a relatively high resistance zone, immediately adjacent one boundary of the trough.
2. A fuse element as claimed in claim 1 wherein the strip is also reduced in section to create a further relatively high resistance zone adjacent the other boundary of the trough.
3. A fuse element as claimed in claim 1 wherein the trough is U-shaped in section.
4. A fuse element as claimed in claim 1 or 2 wherein the trough is rectangular in section.
5. A fuse element as claimed in claim 1, 2 or 3 wherein the or each relatively high resistance zone is provided by a narrow neck.
6. A fuse element as claimed in claim 1, 2 or 3 wherein the or each relatively high resistance zone is provided by holes through the strip.
7. A fuse element as claimed in claim 1, 2 or 3 wherein the or each relatively high resistance zone is provided by an indentation in the strip.
8. A fuse element as claimed in claim 1, 2 or 3 wherein one or more further reduced section regions are provided at location spaced away from the trough.
9. A fuse element as claimed in claim 1, 2 or 3 and having a further trough accomodating a respective mass of low
9. A fuse element as claimed in claim 1, 2 or 3 and having a further trough accomodating a respective mass of low
Claim 9 continued...
melting point metal or alloy and spaced away from the first mentioned trough by the first mentioned relatively high resistance zone.
melting point metal or alloy and spaced away from the first mentioned trough by the first mentioned relatively high resistance zone.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2108875A GB1476870A (en) | 1975-05-17 | 1975-05-17 | Fuse element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038427A true CA1038427A (en) | 1978-09-12 |
Family
ID=10157011
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA252,685A Expired CA1038427A (en) | 1975-05-17 | 1976-05-17 | Fuse element for a cartridge type fuse |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1038427A (en) |
| GB (1) | GB1476870A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD201072B1 (en) * | 1981-11-09 | 1986-03-12 | Zwickau Ing Hochschule | UNIFORM MELT FOR ELECTRICAL FUSES |
| GB8327862D0 (en) * | 1983-10-18 | 1983-11-16 | Marbourn Ltd | Electrical device |
-
1975
- 1975-05-17 GB GB2108875A patent/GB1476870A/en not_active Expired
-
1976
- 1976-05-17 CA CA252,685A patent/CA1038427A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1476870A (en) | 1977-06-16 |
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