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Патент USA US2108843

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Feb. 22, 1938.
E. F. BOOTHE
FUSE LINK
Filed May 25, 1936
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2,108,843
Patented Feb. 22, 1938
UNITED STATES PATENT OFFICE
2,108,843
FUSE LINK
Eugene F. Boothe, St. Louis, Mo.,A assigner to
James R. Kearney Corporation, St. Louis, Mo.,
a corporation of Missouri
Application May 25, 1936, Serial No. 81,636
4 Claims. (Cl. 20D-117)
This invention relates generally to fuse links,
and more specifically to fuse links of the tension
type provided with strain-absorbing means for
relieving the fusible elements of the link of tensile
strains which would be otherwise imposed there-
termined that an unstressed fuse wire which is
intended tc become ruptured upon passage there
through of, say, three~fourths of an ampere, when
held under mechanical tension of the order pro
duced by spring means found in the usual .types of
on, the predominant object of the invention being
to provide a fuse link with strain-relieving means
protective apparatus, is ruptured by currents of a
magnitude substantially less than the figure
specified.
The purpose of this invention, therefore, is to
provide a fuse link construction which will not 10
be harmfully affected by the application thereto
of relatively high mechanical forces by relieving
of such construction and arrangement that, while
the unruptured fuse link is provided with great
in tensile strength, quick separation of parts of the
fuse link on rupture of the fusible element thereof is not unduly interfered with by the strainlabsorbing means.
Another extremely important object of the inl5 vention is to provide a fuse link which is so con-
in an improved manner the fusible element of
the improved fuse link structure of the forces
predueed by the tensioning means, and Whieh iS 15
structed and arranged that during a switching or
lightning surge of current the improved fuse link
less likely to open during passage of a surge of
current due to switching 0r lightning than Were
is less likely to open than the conventional fuse
fuse links not constructed in accordance with
link not constructed and arranged in accordance
90 with this invention. This results from the fact
that an arcing gap is provided in the fuse 1ink
structure between the Strain-absorbing means
and an adjacent portion of the fuse link structure,
and when the surge passesr through the fusible
this invention.
Fig. 1 is a VieW, partly in Vertical SeCtiOn and 20
partly in side elevation, of a fuse cartridge hav
ing the improved fuse link associated therewith.
Fig. 2 is a fragmentary View, partly in Vertical
section and partly in elevation, of a portion of the
lO 5 element 0f the fuse link Structure there is a, voltage drop across the arcing gap sufficient to cause
frena a different angle-
the gap to break down and by-pass a portion of
the current over the gap. kThe time duration involved is so small that the strain-absorbing means
30 is not burned in 13W() by the lay-passed euï‘rent,y
In the drawing, Whel'ein is ShOWn fOr the D111’
Pese 0f illustration, merely, One embodiment of
the inVentiOn, A designates a fuse Cartridge adja
Celli) t0 the IOWBI‘ end Of WhlCh a, terminal mem- im
and hence the fuse link is not damaged by the
Surge current,
Fuse links of the type referred to above 0rdinarily are adapted to be hel-d under mechanical tension produced either by spring means
.which form parts of the fuse link structures, or
parts of the protective apparatus with which the
fuse links are associated, the purpose being to
create a wide gap between the severed ends of the
„0 fusible element of the fuse link after the same
has become ruptured by passage of abnormal ourrent, and to quickly extinguish any are attend-
bei’ B is ilXed, Seid terminal member B being
adapted to aid in electrically associating the fuse
cartridge A with a switch apparatus (not shown).
At its upper end the fuse Cartridge A has aSSO
ing the blowing of the fusible nement by causing
the ruptured ends thereof to fly apart under the
terminal member of the fuse link, said contact
heed being arranged in COnteCt With the t0n faee
„ action of the spring tension.
A heretofore prevailing difficulty inherent in
tension fuse links, particularly those of low or
fractional ampere current carrying capacity, resulted from the tendency of the fusible element
5 to become severed by reason of the mechanical
forces applied thereto, or if not actually severed
the application of such forces to the fusible element for a long period of time resulted in altera*
tion of 'the operating characteristics, or rating,
ofthe fuse link. In other words, it has been de-
Structure illustrated Íl’l Fig. l, but Viewing Same n,
b
Cieted With it en adapter C Which COInDrlses a' Q@
Snert tubular Dertien Cn that iS eXtended dOWn- "
Werdly into the tube A’ Of the fuse Cartridge A,
end en Outstanding annular ilenge Cb Which 00n
tette With the tOD face 0f Said tube
The iInDrOVed fuse link includes e eûntaet head
l which is ñxedly located at the outer end of a
strip 2 of conducting material which serves as a
of the flange Cb of the adapter C, and said strip 2 4
being' eXtended ldOVVnWardly inte the tube A’ Of
the cartridge A- Extended upwardly thrOugh the
cartridge tube A' is an electrical conductor 3,
which serves as a terminal element of the fuse
link, the end 3’ of said conductor which is located 50
within the tube A’ being spaced a considerable
distance from the inner or lower end of the strip
2. The opposite end portion of the conductor 3
is turned about the lower end of the fuse cartridge
and is extended upwardly with respect thereto, 55
2
2,108,843
as indicated at 3iL in Fig. l, said upwardly ex
tended portion of said conductor being mechan
ically and electrically clamped to the terminal
member B of the fuse cartridge through the in
edge of the expulsion tube 9. A button I3 is se
cured to the conductor 3, and this button holds the
tubular element in its elevated position so that
the coil spring l2 is maintained in compression.
In the use of the improved fuse link disclosed
strumentality of a suitable clamping screw D.
The strip 2 and the conductor 3 are connected < herein, the strain wire 4 is not in direct electrical
together by connecting means which includes a
contact with the strip 2 because of the presence of
strain wire 4 that is extended thr-ough apertures
5’ formed through a pair of blocks 5 formed of
10 fiber or other suitable electrical insulating ma
terial. These blocks 5 are secured to the strip 2
at opposite side faces thereof by means of a rivet
the fusible element S.
When a fault occurs in
6 or other suitable fastening means which passes
the line protected by the improved fuse link, the
through apertures formed through the blocks 5
and the strip 2 (see Fig. l). The portion ¿le of
the strain wire which extends through the aper
fusible element 8 melts and thereafter the cur
tures 5’ of the blocks 5 may be described as a
wire in the form of an arc.
bridge portion, and extended from the opposite
duced breaks the strain wire at the bridge portion ¿la thereof, allowing the separated ends of
said bridge portion to be pulled out of the aper
tures 5' of the blocks 5 by the associated switch
mechanism or by the coil spring l2, and thus
permit the fuse link to separate. The importance
ends of this bridge portion are substantially
20 parallel strain wire portions 4b, end p-ortions of
which are arranged parallel and in Contact with
the adjacent end portion of the conductor 3. The
end portions of the strain wire portions 4b are se
cured to the conductor 3 by a sleeve l formed of
conducting material which closely embraces the
end portion of the conductor and the portions
of the strain wire portions lib which contact there~
with. As shown in Figs. l and 2, the sleeve l,
which by preference is formed of suitable metal,
is flattened as is the end portion of the conductor
3, and therefore the end portions of the strain wire
portions 4b are very securely clamped to the con
ductor 3 by said flattened sleeve i. In order to
eliminate any chance that the tensional strains
to which the strain wire 4 is subjected may result
in the strain wire portions [ib being pulled from
between the sleeve 'l and the conductor 3, said
portions 4b are preferably bent double, as shown
by dotted lines in Fig. 2, and also at bent ends
4C of said strain wire portions 4b, which extend
slightly
producedoutside
which of
iirmly
the sleeve
securel,the
soldered
strain`joints
wire and
the sleeve 'l together.
With regard to the strain wire il, it is of exe
treme importance to note that a gap G (see Fig. l)
is present between the strain wire and the strip 2,
and this gap takes the strain wire out of direct
electrical connection with the strip E and under
normal conditions prevents the strain wire from
being a direct part of an electrical circuit of
which the fuse link forms a part.
Li
the gap G which separates the bridge portion 4a
of said strain wire from said strip, hence all elec
trical current conducted by the fuse link under
normal operating conditions must flow through
Secured by solder or otherwise at one end to
the strip 2 and by solder or otherwise at the op
posite end to the sleeve l is the fusible element 8
of the fuse link. As shown to the best advantage
in Fig. 2, the fusible element 8 is out of direct
electrical connection with the strain wire d.
Extended downwardly from the strip 2 is an
expulsion tube 9 formed of electrical insulating
material which embraces the extreme lower porn
tion of the strip il, the lower ends of the blocks
5, the strain wire 4, the sleeve l, a portion of the
conductor 3, _and a large part of the fusible ele
ment 8. The lower portion 2’ of the strip 2 which
extends into the expulsion tube is of reduced
width, whereby said strip is provided with
shoulders 2St which contact with the upper edge of
the expulsion tube. Extended upwardly into the
rent flows through the strain wire 4, said current
passing from the end of the strip 2 to said strain
The arc thus pro
of the gap- G resides in the fact that a small fraction of an ampere through an arc will break a
strain wire of the required strength, whereas, if
the strain wire were continuous, several amperes
would be required in order to melt the strain wire
and break the circuit.
[i further important advantage of the gap G is 30
that during a surge of current through the im
proved fuse link due to switching or lightning, the
fuse link is much less likely to open than a fuse link
not provided with such a gap. This results from
the fact that when the surge passes through the
fusible element, for instance, 10,000 amperes in 3
or 4 micro-seconds, there is a Voltage drop across
the arcing gap G sufficient to cause the gap to
break down and by-pass a portion of this current
over the gap, and because the time duration of 40
such lay-passing of current is so small the strain
wire is not burned in two and the fuse link is not
damaged by the surge of current.
I claim:
l. A fuse link assembly including a pair of
spaced terminal members, a fusible element for
electrically connecting said terminal members,
and connecting means for mechanically connecte
ing said terminal members so as to relieve said
fusible element of tension applied to the fuse
link assembly, said connecting means including
a strain wire connected to one of said terminal
members and insulating means for connecting
said strain wire to the other of said terminals
in spaced relation with respect thereto, so as to
provide a gap between said strain wire and said
terminal, which electrically separates same dur
normal operation of the fuse link assembly
and over which current passes during abnor
mal passage of current through the fuse link
assembly, said insulating means including a
block secured to said terminal member and pro
vided with an aperture through which said strain
wire passes so as to provide a portion of the
strain wire which is disposed in spaced aline
ment with the adjacent terminal to produce said
gäp
expulsion tube 9 from a point a considerable dis
2. A fuse link assembly including a pair of
spaced terminal members, a fusible element for
tance below the lower edge of said expulsion tube
is an elongated tubular element i0, which at its
and connecting means for mechanically connect
lower end is provided with an outstanding, annu
ing said terminal members so as to relieve said
lar flange ll, and an expansible coil spring l2 is
interposed under compression between said annu
lar flange of the tubular element l0 and the lower
fusible element of tension applied to the fuse
link assembly, said connecting means including
electrically connecting said terminal members,
a strain wire connected to one of said terminal
2,108,848
members and insulating means for connecting
said strain wire to the other of said terminals
in spaced relation with respect thereto, so as to
3
of spaced blocks secured to said terminal mem
ber at opposite sides thereof and provided with
apertures through which said strain Wire passes
provide a gap between said strain wire and said
so as to provide a portion of the strain wire
terminal, which electrically separates same dur
ing normal operation of the fuse link assembly
which is disposed in spaced alinement with the
and over which current passes during abnor
mal passage of current through the fuse link
assembly, said insulating means including a pair
of spaced blocks secured to said terminal mem
ber at opposite sides thereof and provided with
apertures through which said strain wire passes
so as to provide a portion of the strain wire which
is disposed in spaced alinement with the adja
cent terminal to produce said gap.
3. A fuse link assembly including a pair of
spaced terminal members, a fusible element for
electrically connecting said terminal members,
and connecting means for mechanically connect
ing said terminal members so as to relieve said
fusible element of tension applied to the fuse
link assembly, said connecting means includ
adjacent terminal to produce said gap, and a
sleeve for attaching the strain Wire to the other
terminal member.
4. A fuse link assembly including a pair of
spaced terminal members, a fusible element for
electrically connecting said terminal members,
and connecting means for mechanically connect
ing said terminal members so as to relieve said
fusible element of tension applied to the fuse link
assembly, said connecting means including a
strain wire connected to one of said terminal
members and insulating means for connecting
said strain Wire to the other of said terminal
members in spaced relation with respect there
to, so as to provide a gap between said strain
wire and said terminal member which electrical
ly separates same during normal operation of
ing a strain Wire connected to one of said ter
minal members and insulating means for con
the fuse link assembly and over which current
passes during abnormal passage of current
necting said strain wire to the other of said ter
minals in spaced relation with respect thereto, so
through the fuse link assembly, said insulating
as to provide a gap between said strain Wire and
said terminal, which electrically separates same
during normal operation of the fuse link assem
bly and over which current passes during ab
normal passage of current through the fuse link
assembly, said insulating means including a pair
means being secured to said terminal member
and having the strain wire so associated and as
sembled therewith as to space a portion of the
strain Wire from the adjacent terminal member
to produce said gap.
EUGENE F. BOOTHE.
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