Improvements in Electric Safety Fuses.
Year: 1890

page_text: Date of Application, 24th Nov., 1890
Complete Specification Left, 28th July, 1891-Accepted, 29th Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in Electric Safety Fuses.
I, WILLIAM MORRIS MORDEY, of Victoria Works, Lambeth in the County of
Surrey, Electrician, do hereby declare the nature of this invention to be as follows :-
My invention has for its object improved means of constructing safety fuses
especially suitable for high tension electric circuits.
Hitherto it has been found necessary or advisable to make high tension safety
fuses of a considerable length, in order to prevent the formation of destructive and
dangerous arcs occurring when the fuses are caused to melt by the passage of
currents greater than they are intended to carry when used under normal conditions.
Various plans have been proposed and used to further guard against the formation
of, such arcs. For example, the fuse (which has usually consisted of one or more
wires) has been made to pass through holes, slits, or apertures in diaphragms, or
other dividing partitions or screens, placed between the terminals or ends of the fuses.
In spite of these and other precautions the difficulty of preventing the formation of
dangerous or objectionable arcs has been considerable. The fuses made to meet this
difficulty have hitherto been large, costly, and wasteful of energy.
By my invention I am enabled to make fuses, even for very high tension, of a
small size and which are inexpensive, absorb very little energy, and will break the
circuit without any objectionable arc or risk of short circuit, even under the most
trying conditions.
In constructing fuses according to my invention the fusible conductor, which
consists of a thin wire, or it may be two or more such wires, or a strip of thin foil
or sheet metal-the metal used being preferably copper in all cases is supported
in a glass tube or other suitable vessel or box. This tube or vessel is then partly
or wholly filled with finely divided or pulverized non-conducting or badly con-
ducting material preferably incombustible or non-inflammable such as dry chalk,
marble, bath brick, sand, mica, emery, asbestos, or the like, this material being
made to cover and surround the fuse wire or strip. A small space is or may be left
uncovered by this material at some portion of the tube or vessel to enable the
position and condition of the fuse conductor to be observed. Contact is made in
any convenient manner with the ends of the fuse. Thus when a glass tube is used
the ends are closed by small caps of brass or are surrounded by rings or collars of
Connection
brass or other metal, to which the ends of the fuse wire are soldered.
is then conveniently made with these caps or rings by spring clips, or holders,
permanently attached to a case or base in or on which the fuse is supported.
Another way in which safety fuses may be constructed according to my invention
is to support the fuse wire in a groove, trench, or recess in a receptacle made of
porcelain or other suitable material, and to fill up the groove or recess with the
finely-divided or pulverized material, securing the whole by a cover or lid of suitable
material such as porcelain, or glass. A small portion of the fuse conductor is
preferably left uncovered and visible to enable its position and condition to be
observed.
The above described methods of carrying out my invention are those which I
prefer, but I do not limit myself to them. Other methods may be used. Thus
instead of surrounding the fuse by the non-conducting material in a finely divided
form, as above described, in a glass tube or other receptacle, I may make up the
said material, by compression or otherwise, into a mass, as for instance in the form
of a block or cylinder surrounding the conductor, or having one or more small holes
through which the conductor may be passed, and in which it may be secured.
The action of this improved fuse is as follows: The passage of an excessive

page_text: current causes the conductor to be volatilized, the metal being deposited in a finely
divided condition amongst the particles of the surrounding non-conducting material.
So complete is the dissipation of the metal that it is frequently difficult to find any
trace of it after the conductor has been fused.
The non-conducting material between the terminals reduces the amount of air in
the vessel, prevents the formation of a conducting chain of metallic particles, and
forms a highly resisting medium. Thus the occurrence of an arc is prevented. For
large currents I prefer to use a small fuse constructed as above described, or other-
wise according to my invention, and to shunt it by an ordinary fuse or by an
electromagnetic or other cut-out. This ordinary fuse or cut-out is arranged to
carry practically the whole current. In the event of an excessive current, the
ordinary fuse melts or the cut-out acts, but does so with a scarcely perceptible
spark the final rupture of the circuit then occurs in the small special fuse.
Dated this 24th day of November 1890.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electric Safety Fuses.
1. WILLIAM MORRIS MORDEY, of Victoria Works, Lambeth, in the County of
Surrey, Electrician, do hereby 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:―
My invention has for its object improved means of constructing safety fuses
especially suitable for high tension electric circuits.
Hitherto it has been found necessary or advisable to make high tension safety
fuses of a considerable length, in order to prevent the formation of destructive and
dangerous arcs occurring when the fuses are caused to melt by the passage of
currents greater than they are intended to carry when used under normal conditions.
Various plans have been proposed and used to further guard against the formation
of such arcs. For example, the fuse (which has usually consisted of one or more
wires) has been made to pass through holes, slits, or apertures in diaphragms, or
other dividing partitions or screens, placed between the terminals or ends of the
fuses. In spite of these and other precautions the difficulty of preventing the
formation of dangerous or objectionable ares has been considerable. The fuses
made to meet this difficulty have hitherto been large, costly, and wasteful of energy.
By my invention I am enabled to make fuses, even for very high tension, of a
small size and which are inexpensive, absorb very little energy, and will break the
circuit without any objectionable arc or risk of short circuit, even under the most
trying conditions.
In constructing fuses according to my invention, the fusible conductor, which
consists of a thin wire, or it may be two or more such wires, or a strip of thin
foil or sheet metal-the metal used being preferably copper in all cases is sup-
ported in a glass tube or other suitable vessel or box. This tube or vessel is then
partly or wholly filled with finely divided or pulverised non-conducting or badly
conducting material preferably incombustible or non-inflammable such as dry
chalk, marble, bath brick, sand, mica, emery, asbestos, or the like, this material
being made to cover and surround the fuse wire or strip. A small space is or
may be left uncovered by this material at some portion of the tube or vessel to
enable the position and condition of the fuse conductor to be observed. Contact
is made in any convenient manner with the ends of the fuse. Thus when a glass
tube is used, the ends are closed by small caps of brass, or are surrounded by
rings or collars of brass or other metal, to which the ends of the fuse wire are
soldered. Connection is then conveniently made with these caps or rings by

page_text: spring clips, or holders, permanently attached to a case or base in or on which the
fuse is supported. Another way in which safety fuses may be constructed according
to my invention is to support the fuse wire in a groove, trench, or recess in a
receptacle made of porcelain or other suitable material, and to fill up the groove
or recess with the finely divided or pulverised material, securing the whole by a
cover or lid of suitable material such as porcelain, or glass. A small portion
of the fuse conductor is preferably left uncovered and visible to enable its position
and condition to be observed.
The above described methods of carrying out my invention are those which I
prefer, but I do not limit myself to them. Other methods may be used. Thus
instead of surrounding the fuse by the non-conducting material in a finely divided
form, as above described, in a glass tube or other receptacle, I may make up the
said material, by compression or otherwise, into a mass, as for instance in the form
of a block or cylinder surrounding the conductor, or having one or more small holes
through which the conductor may be passed, and in which it may be secured.
The action of this improved fuse is as follows:-The passage of an excessive
current causes the conductor to be volatilized, the metal being deposited in a finely
divided condition amongst the particles of the surrounding non-conducting material.
So complete is the dissipation of the metal that it is frequently difficult to find any
trace of it after the conductor has been fused. The non-conducting material
between the terminals, reduces the amount of air in the vessel, prevents the
formation of a conducting chain of metallic particles, and forms a highly resisting
medium. Thus the occurrence of an arc is prevented. For large currents I prefer
to use a small fuse constructed as above described, or otherwise according to my
invention, and to shunt it by an ordinary fuse or by an electro-magnetic or other
cut-out. This ordinary fuse or cut-out is arranged to carry practically the whole
current. In the event of an excessive current, the ordinary fuse melts or the cut-
out acts, but does so with a scarcely perceptible spark; the final rupture of the
circuit then occurs in the small special fuse.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what 1
claim is :-
1. In a safety fuse for electric circuits, surrounding the fusible conductor by a
non-conducting or badly conducting substance substantially in the manner and for
the purpose herein before described.
2. The use in combination with and as a shunt to a fuse of the kind referred to
in the preceding claim, of an ordinary fuse, or an electro-magnetic or other cut-out,
substantially as hereinbefore described.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.