Year: 1894

page_text: Date of Application, 5th June, 1594
Complete Specification Left, 5th Apr., 1895-Accepted, 18th May, 1895
SEBASTIAN ZIANI DE FERRANTI, Charterhouse Square in the County of
London, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
This invention has for its object an improved form of fuse specially suitable for
breaking high tension currents when the amount of current flowing through the
fusé becomes too great.
According to my invention I prefer to form the fuse of a thin copper wire
supported in its centre on a ridge of porcelain or other refractory non-conductor,
and having each of its ends attached to a spring which spring is in turn attached
to the terminals of the apparatus. The springs are drawn up to the level of the
fuse wire and being surrounded by a vessel are immersed in thick oil. The fuse
wire itself is in air and is very short. The current passes from one terminal
through the spring attached to it, through the fuse wire down by the other spring,
and out by the terminal. When the current becomes too strong the fuse wire
melts and the springs on each side of the insulating ridge spring back into the oil
and become entirely immersed so putting out the arc which follows on the breaking
of a high tension fuse.
The pull which the springs exert on the wire tend to break it before its actual
fusion and there is thus a less tendency for arcing to take place.
According to another method I hold the fuse wire on two rigid supports which
are immersed in oil, the fuse only projecting for a portion of its length.
When the current becomes too great the fuse is melted and burned away a little
below the oil, which then rushes back and seals over the ends of the supports, thus
stopping any are which may follow.
In either of the above mentioned arrangements the fuse can be entirely covered
with oil provided it is kept near the surface of the oil, as if it is not the oil will be
badly carbonised and blown away when the fuse burns.
1 prefer to make safety fuses according to any of the following methods.
I take two porcelain or earthenware tubes closed at their lower ends by means
of metal blocks, which act as terminals, and which may have the wires attached
direct to them, or which may be made to fit into spring contacts so as to be
removable. On to the metal blocks I fix spiral springs which in their turn carry
the fuse wire. Sometimes I place two of these tubes side by side and put the fuse
wire between the ends of the two springs.
According to another method I use only one of these tubes and make a terminal
on top of it to which to attach the other end of the fuse wire.
According to another method I make the fuse pot an oblong box with a spring
at an angle coming up through the oil to the fuse, the other end of which is
attached to a terminal.
I sometimes place two of these side by side. Then both the terminals are below
the level of the oil and the fuse wire is stretched over the edge of the pots from
one spring to the other. I sometimes mould the fuse blocks in pairs instead of
putting two together as above described, to form one fuse.
}

page_text: Where the terminals are made with spring contacts so that the fuse blocks are
removable I provide short-circuiting plugs which can be inserted before removing
the fuse blocks for changing a fuse.
Dated this Fifth day of June One thousand eight hundred and ninety-four.
Improvements.in Electric-Safety Fuses or Cut-outs.
SEBASTIAN ZIANI DE FERRANTI, Charterhouse Square, in the County of
London, Electrical Engineer, do bereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement: :―
This invention has for its object an improved form of fuse suitable for breaking
high tension currents when the amount of current flowing through the fuse becomes
too great.
Figure 1 is a section of a type of fuse specially suitable for switchboards.
Figure 2 is a plan of Figure 1.
Figure 3 is an end elevation of the handle of same.
Figure 4 is a plan through a second form of fuse specially suitable for
transformers.
Figure 5 is a section C. D. through Figure 4.
Figure 6 shows another form of fuse without spring.
Figure 7 shows sectional elevation of Figure 6.
Figure 8 shows a sectional elevation of fuse with springs.
Figure 9 section through A. B. of Figure 8.
Figure 10 plan of Figure 8.
Figure 11 sectional elevation of single spring fuse.
Figure 12, plan of Figure 11.
Figure 13, sectional elevation of a fuse with side contacts for connection at an
angle.
Figure 14 sectional elevation on C. D. of Figure 13.
Figure 15 plan of Figure 13.
Figures 16, 17, 18 and 19 show plug and method of putting same into main
switchboard for withdrawing a fuse.
According to my invention I prefer to form the fuse a, of a thin copper-wire or
wires supported on a ridge of porcelain, g, or other refractory non-conductor. The
porcelain ridge g is part of a container c of refractory material generally divided
into two chambers by the porcelain ridge g. The fuse a has its ends attached to
springs which are immersed in a heavy insulating oil d of non-inflammable
character to a level as shown. The fuse a itself is thus in air and very short.
The current is led into the fuse by means of contacts ; or permanent connections i,
to terminals e. From these the current flows through the springs b-through the
fuse wire a back by the second spring band out by the terminal e' to the contact j.
In cases where the current is a heavy one I may instead of allowing the whole of
the current to pass along the springs, use in addition a flexible conductor f, made
up of a number of copper strands.
When the current becomes too strong the fuse wire a melts and the springs b
and on each side of the insulating bridge g spring back. into the oil and become
entirely immersed so putting out the are which follows on the breaking of a high
tension fuse.
The pull which the springs 6 exert on the wire a tend to break it before its
actual fusion and there is thus a less tendency for arcing to take place after the
fuse has blown.

page_text: According to another method Figures 6 and 7 I connect the fuse wire a on to
two rigid supports h which are immersed in the oil d, the fuse projecting from the
oil as usual for only a short part of its length. When the current becomes too
great the fuse is melted and burnt away a little below the oil dit temporarily
displaces the oil which then rushes back and seals over the ends of the supports
thus preventing any are from being maintained.
In any of the above mentioned arrangements the fuses can be entirely covered
with oil provided they are kept near the surface of the oil, otherwise the oil will
be badly carbonised and blown away when the fuse burns.
I prefer to make safety fuses according to any of the following methods.
Figures 1, 2 and 3, show a type of fuse specially fitted for high tension
switchboards. In these the contacts ; and j₁ are of large surface and make
connection into split contacts when the fuse container c is moved forward. These
contacts are fixed in the container c by means of type metal t and a washer o and
lock nut p.
The spring his generally made of tempered steel where the current
to be carried is a large one, and the flexible conductor f of fine copper strands
which carry the current. This flexible conductor is sweated to the terminal e and
also to a small gun metal fitting m carried at the end of the spring b. When it is
desired to put in the fuse a; the springs are raised and a fuse, made of a number
of fine copper wires, is slipped over the circular ends of the gun metal fitting m.
This fuse then rests across the porcelain ridge g. If an excess of current passes
the fuse acts in the manner before described.
A slight arc may take place at the instant of burning and in order to protect
this from doing any damage a lid 1, of refractory material is placed over the top
of the container c, Figures 4 and 5, show a similar arrangement to the above but
instead of being fitted for quick withdrawal it is fitted with terminals i for purposes
where a more permanent connection is required.
Figures 6 and 7 show a form of fuse for dealing with currents of such a
magnitude that the action of the spring is not necessary to efficiently break
the arc.
Figures 8, 9 and 10 show a somewhat similar fuse fitted with projecting split
contacts suitable for making connection where the switch and fuse are combined
in one apparatus.
Figures 11 and 12 show a form of fuse having one spring only for use where it
may be necessary to economise space.
Figures 13, 14 and 15 show a form of fuse similar to that shown in Figures 8, 9
and 10 but fitted with contacts which allow the current to be brought in and leave
at an angle. This design is specially suitable for transformers. In the event of
the burning of a fuse the whole container can be withdrawn and a fresh one
inserted.
Where the terminals are made with spring contacts so that the fuse blocks are
removeable I provide short circuiting plugs which can be inserted before removing
the fuse blocks for changing a fuse..
This may be effected in the following manner Fig. 16 shows a sectional elevation
of a switch-board showing fuse c and Figs. 17 & 18 section through A. B shows
removeable plug a and oil fuse c of type previously described, making contact
through its contacts j and j' with two spring contacts n' and n² forming part of the
switch-board. The current entering the switch-board at the gun-metal contacts g
from thence flowing through contacts m³ on to the fuse contact j' through the oil
fuse pot cout.of contact j on the switch-board contact n³ and thence on to gun
metal fitting m¹ being held by insulating cement e into porcelain insulators p
supported by slate slab s.
If it is desired at any time to remove the fuse for examination it can be
withdrawn without breaking the circuit if the plug a Fig. 19 is inserted between
5 the two gun metal contacts Fig. 18 shown by f' and f² making contact with the
gun-metal block 9 and m¹ the fuse can then be withdrawn thus leaving the circuit
in its original state.

page_text: In order that the plug a Fig. 19 may make good contact and at the same time be
used with safety the handle is made of ebonite, the copper strips f1 and f³ are
held in position and connected by means of bolts z and 2 and in order to secure
flexible connection the copper contacts f1 and 2 are forced apart by means of the
spring which is embedded in a hole in the ebonite where the action is
counteracted by a second springs under the head of the bolt z¹ thus always
allowing the copper strip and f³ to take up a perfectly flexible position, and
when thrust in between the gunmetal piece 9 and m¹ they make efficient connection.
Clearance is provided between the feet of the fuse to enable this plug to be
inserted readily.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed 1 declare that what I
claim is :-
1. In electric safety fuses or cut-outs, the combination of a fuse wire and
terminals, connecting same to the circuit to be protected, which terminals are held
in insulating receptacles which receptacles are filled with insulating oil so that
the said terminals are covered, the fuse wire only being exposed to the air.
2. In electric safety fuses the use of a fuse wire stretched through air over an
insulating and fire proof partition, the ends of which are attached to terminals
below the surface of a liquid insulator on each side of the partition.
3. In electric safety fuses the combination of a trough or receptacle containing
a liquid insulator, a terminal for the circuit going into same and the fuse wire held
by a spring carried in the said terminal and immersed in the insulating oil, the
other end of the fuse wire being connected to a second terminal in air.
4. In electric safety fuses the combination of a pair of terminals for connection
to the circuit to be protected, said terminals being fixed in receptacles containing
a liquid insulator in a fire-proof and insulating vessel, the fuse wire being carried
by springs attached to terminals and stretched across an insulating fire-proof
partition between the two terminals.
5. In electric safety fuses in which the fuse is held upon springs, the lower parts
of which are immersed in a liquid insulator and which immerse themselves in the
insulating liquid upon the burning of the fuses.
6. In electric safety fuses in which the fuse wire is supported in air or near the
surface of an insulating liquid, and into which the terminal supports completely
immerse themselves on burning of the fuse wire.
7. In electric safety fuses containing an insulating liquid, the use of spring or
plug contacts for inserting the fuse in the circuit to be protected.
8. In electric safety fuses which are set up in an insulating block arranged for
rapid withdrawal or insertion, the use of shortcircuiting plugs in the fixed parts
for cutting out the fuse circuit during the manipulation of same.
9. Electric safety fuses substantially as described and illustrated in the
Specification and drawings hereto annexed.
Dated this Fifth day of March 1895.