Improvements relating to Switch Fuses for Electric Circuits.
Year: 1896

page_text: Date of Application, 26th Aug., 1899-4ccepted, 24th Dec., 1896
COMPLETE SPECIFICATION.
Improvements relating to Switch Fuses for Electric Circuits.
We, CHARLES JAMES HALL, Electrical Engineer, and HENRY JAMES
FULLER, Mechanical Draughtsman, both of Messrs. John Fowler and Company
(Limited), of Leathly Road, Hunslet, Leeds, in the County of York, do hereby
declare the unature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
This invention has for its object to provide a switch fuse or automatic cut out for
electric currents which combines the following desiderata.-
1. Complete protection against accidental contact ;
Facility of inspection without the need of interrupting the electric circuit.
3. Easy removal of the fusible conductor for the purpose of exchange or
renewal.
4. Low cost of manufacture, especially in the case of large fuses.
In the accompanying drawings,
Fig. 1 is a sectional elevation of a switch fuse embodying our invention and
showing two different ways of fixing the terminal to the base.
Fig. 2 is a transverse section along line X-X of Fig. 1.
Fige. 3 and 4 are a sectional elevation and an end view of a switch fuse suitable
for low and medium pressures of electricity.
Fig. 5 is a longitudinal section of one extremity or half of a switch fuse suitable
for very long breaks or fusible conductors of great length.
Fig. 6 is a similar view, but showing a different form of fitting.
Figs. 7 and 8 show one end of a switch fuse in which the fusible conductor and
fuse holder have à different form.
Throughout the various figures, A (A¹, A') represents the handle, mado of
porcelain, cbouite, or other suitable insulating material; B (B, B2) indicates the
base, which may be of porcelain, slate, wood, or similar material; C (C', C')
the movable contact pieces or contact plugs which are cemented into the handle A
D (D', D) the fixed contact pieces or contact jaws secured to the base B and
adapted to receive the plugs C; in the right hand portion of Fig. 1 the contact
jaw is cemented directly to the base, while the left hand portion of the same
figure, as well as Figs. 5 and 6 show the jaw D cemented in a porcelain or ebonite
holder E (E', E') which in turn is bolted or cemented to the base B. F represents
cement; G (G) a tube surrounding the fusible conductor and made of glass, mica,
or other transparent insulating material; G a fuse support which in the form of a
switch fuse represented by Fig. 7 is used instead of the tube G aud which may be
made of transparent or opaque insulating material. The fuse wire J in
Figs. 1 and 2, passes through the tube G, through the plugs C, and is finally
clamped at each end under a screw and washer H. K' is a protecting guard made
of fibre, mica, ebonite, or other insulating material and intended to be used for
current pressures of about 200 volts and upwards.
In Figs. 5 and 6, the switch fuse has two handles or holders A, made of
nsulating material and joined together by means of a connection L', which is inade
of metal or other suitable material and niay have a guard M' of insulating material
o prevent the possibility of arcing taking place on to the connector. Fig. 5 also

page_text: shows. an elastic metal tube N' for fitting the fnse tube G into the plug the
fuse tube being in this case provided with a metal cap O' to which is soldered
or otherwise attached the fuse wire, so that the mere insertion of the fuse tube
(containing the fuse wire) into the spring tube N' will make sufficient contact,
without the need of clamping screws.
The contact jaw D' is completely surrounded with a porcelain cup E' fixed to
the base plato B, and the said jaw is connected with the calle P' in Fig. 5 by a
metallic cone Q', fitted into the jaw D so as to provide a cable connection at the
front of the switch instead of at the back. The cup E' is so shapel as to cover
the joint between the jaw D' and the cable P, a very desirable thing, where front
cable connections are used..
In Fig. 6 the bridge piece L' connecting the two handles A', A' is provided with
an insulating handle R, by means of which the bridge piece, together with the
fuse tube and plugs C, may be easily lifted out of the jaws D', D. In the switch
fuse represented by Fig. 7 and Fig. 8, the fuse wire Jis supported by a porcelain
plate Ghaving longitudinal ribs g and perforations g' through which the said wire
is threaded in and out, and as the supporting plate G is not situated above the
insulating porcelain cup E, as in the previous examples, the said porcelain cup has
a longitudinal slot for holding the extremity of the plate G and admitting the fuse
wire J to the contact plug C. The latter is composed of two halves or pieces,
one of which is cemented with its upper end into the handle A, while the second
half is secured to the first by screws S. The fuse wire J' is clamped between the
two halves of C and guided around pins or pegs e fixed on the plug C', as shown
by Fig. 8.
In the switch fuses represented by Figs. 1, 2, 5 and 6, the extremity of each
handle A forms a pair of wings extending downward right and left of the fuse tube
and allowing the said tube to be drawn out longitudinally and, in these figures, as
well as in Figs. 7 and 8, the metallic contact pieces are well protected, partly by
the insulating cups E, E', E' E', and partly by the handle A, A, A'.
As will be seen on reference to these figures, the metallic portions are compact
and simple of outline, in order that the handle and guard which receive and protect
the metal fittings may also have a compact and simple shape, and may therefore be
easily and cheaply made of porcelain, ebonite, or similar material, while affording
ample protection. No part of the handle or other portions to which the fittings
are secured, comes in the path of the fuse, consequently the fuse can be surrounded
by an insulating tube. The latter cau pass through the fittings from end to end of
the switch fuse and is only held in position by a screw or spring clip; hence in case
of breakage, the fuse tube can be easily removed and replaced. The said screw or
spring clips are situated within the wings or extensions of the porcelain holders or
handles and thereby are protected from accidental contáct.
In small switch fuses, the insulating portion such as the handle A in Figs. 1
and 2 can be conveniently made of one piece and will then be amply strong for all
reasonable requirements; but in larger sizes, the length of a single porcelain holder
or handle would greatly increase the cost and the liability to fracture. We have
therefore adopted a metallic connecting bar L, Fig. 5 and 6, the ends of which are
provided with insulating bandles or holders A'carrying the movable contact blocks
or plugs C. In this manner the porcelain or other insulating parts are reduced to
a small size, and can be made approximately circular or cylindrical, for convenience
of manufacture.
The base plate B of the switch fuse may be made of wood, slate, marble, o
other cheap insulating material, while the parts which immediately receive the
stationary contact blocks or jaws D are made of porcelain or similar high clas
insulating material and are secured to the base plate. In this way the porcelain o
other expensive insulating material is reduced to small dimensions and simpl
shape, and the cost of manufacture is reduced.
For comparatively low pressure work, where little protection is required, the cos
of manufacture may be further reduced by simplifying the shape of the handle, n

page_text: in Figs. 3 and 4, and omitting porcelain, ebonite, or other expensive insulating
material in the construction of the base.
The straight handle A, Figs. 3 and 4, is provided at its ends with oircular
recesses within which the metallic fittings Care secured by means of suitable
cement. The addition of a guard K' of mica, vulcanized fibre or other suitable
insulating material to prevent contact immediately under the hand, would render
this form of switch fuse applicable even in high pressure circuita.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what.
we claim is :-
1. A switch fuse for electric currents, having a pair of movable metallic contact
pieces attached to an insulating handle or a pair of insulating holders and
electrically connected with each other by a detachable fusible conductor placed
parallel or out of line with the handle, substantially as described and for the
purpose specified.
2. A switch fuse for electric curreuts, comprising in its construction a pair of
movable metallic plugs or other contact pieces attached to an insulating bundle or a.
pair of holders and electrically connected with each other by a detachable fuse-wire
placed parallel or out of line with the handle, a detachable transparent insulating
tube enclosing the fuse wire between the said contact pieces, a pair of contact
jaws or stationary metallic contact pieces mounted on a base plate and adapted to
make contact with the movable contact pieces, and a pair of insulating cups or
guards surrounding the said contact pieces and mounted on the said base-plate,.
substantially as described, and for the purpose specified.
3. The various forms of switch fuses or electric safety fuses, substantially as
described with reference to Figs. 1 to 8.
Dated this 24th day of August 1896.
FAIRFAX & WETTER,
433, Strand, London, Agents.