Improvements in Safety Fuse Apparatus for Electrical Installations.
Year: 1898

page_text: Date of Application, 1st Sept., 1893-Accepted, 26th Nov, 1898
COMPLETE SPECIFICATION.
Improvements in Safety Fuse Apparatus for Electrical Installations.
We, SIEMENS BROTHERS & Co LIMITED, of 12, Queen Anne's Gate, West-
munster, S W., in the. County of London, Electrical Engineers, do hereby declare
the nature of this invention (as communicated to me fiom abroad by Siemens &
Halske Aktien-Gesellschaft, Markgrafen Strasse, 94, Berlin, SW, Germany,
Electrical Engineers), and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement.-
The safety fuse apparatus with shutters described in the Specification to Patent
No. 24,020 of 1895 was subject to the disadvantage that the changing of the
fusible stup or wire was attended with too much difficulty, as one or both the
shutters required to be raised at the same time that the new strip or wire was
inserted into the terminal clamps. The latter when arranged as shewn at Figs. 5
and 6 of the said specification were also subject to the disadvantage that two
screw nuts and in some cases also two supporting discs had to be loosened on
removed in effecting the change
The arrangement shewn at Figs 1 to 3 of the said specification are not subject
to this inconvenience but the forcing of the contact ends of the strip into the
clamping springs of the terminals requires a considerable pressure, in order to
obtain a reliable contact for strong currents
It is also found inexpedient to place the springs that actuate the shutters at
the sides of the place where the burning of the strip, and consequently the arc,
occurs, as they may readily become deteriorated by the heat, and also facilitate
a lateral passage and maintenance of the arc
The present improved construction has for its object to do away with the above
described disadvantages, and to protect the terminal clamps as also the shutter
springs as much as possible against the access of the metallic vapours, as also to
protect surrounding objects from the heat of the burning fuse by enclosing the
apparatus entirely with a protective casing
The safety fuse apparatus consists mainly of two parts, namely the lower part
or fuse
proper which is inserted in the circuit, and which 18 shewn in aide view
at Fig 5 of the accompanying diawing, and in end view at Fig 6, and the pro-
tective casing which is shewn partly in elevation and partly in section at Fig 3
and in cross section at Fig 4
Figs 1 and 2 shew a sectional side view and a cross section of both parts com-
bined, and Fig. 7 shews a plan of the same partly in section Figs. 8 to 10 shew
the new terminal clamp in three positions.
On the base G is fixed a porcelain pediment P in which is fitted a block of
cement or other suitable fireproof material C, so that on the one hand a high
degree of insulation and on the other hand a great resistance to a short circuiting
of the electric arc 18 afforded
The porcelain pediment P also carries the terminal clamps K¹ and K³ with
the contact screws A¹ and A³ for the connection of the circuit leads, which are
passed through the porcelain sockets D¹ D* screwed to the base.

page_text: The four vertical sides of the cement block C are made of a height such as the
protective casing will allow of, for the purpose of protecting as much as possible
the surrounding objects from the electric arc formed on the burning of the safety
fuse
The ends of the block C which are parallel to the shutters S1 88, presently to
be described, are suitably recessed for the introduction of the fuse strip, the
block is also provided at the bottom with recesses R R into which the shutters
drop after the burning of the fuse The shutters are mounted loose in the block C,
which acts as guide thereto; they are merely placed upon the fuse strip M after
this has been placed in position, so that at first they are not subjected to down-
ward pressure. If now the fuse strips be made weakest at the part between the
shutters, as described in the said former patent, the burning through will take
place at this point, that is to say, in a space that is only open at the top, being
enclosed on all sides by cement walls If the electric ale is not at once extin-
guished after being formed, the fuse strip will be entirely destroyed and the
shutters in dropping will also close the small openings in the block C required
for the passage of the fuse strip The requisite foice for effecting the reliable
descent of the shutters is produced by two springs F and F fixed in the protec-
tive casing II, and pressing with their fiee ends upon the tops of the shutters
when the casing is placed in position
In order that these springs may be protected as much as possible from the
electric arc they are arranged in the enclosed space formed behind the wood
blocks T 1 by a double top to the casing the ends of the springs being made to
Dase on each side of the blocks T¹ T to the shutters, which may be attached to
the springs if desired
By this means the springs are effectually protected against the aro
The double top Z Z extends from the ends of the casing up to the cement
block C, a suitable opening being formed for the passage of the ends of the
springs and the upper ends of the raised shutters
Through this opening the gases produced on the burning of the fuse can enter
the said enclosed space above the double top, the outer top of the casing being
perforated to allow of the ready escape of the gases if necessary By the above
described construction all metal parts will be protected against the electric arc,
with the excepton of a small portion of the springs F1 F2, and can therefore not
be burnt
The insertion of the shutters is very easily effected, and the renewal of the fuse
strip or wire is facilitated by the mode in which it is connected to the terminal
clamps As shewn at Figs 8 to 10, the oval end 0% of the strip M only requires
to be loosely laid on to the spring clamps K' K and then turned one quarter
round by means of the lever 1, in order to enter the notches of the spings and
thus make a firm contact therewith, without requiring the use of any screws
The mode of fixing the casing H enclosing the eutue safety device is also of a
secure and at the same time easily detachable nature
On the base G are fixed upwaidly projecting blade springs E E that fit into
grooves on the outside of the casing H, and the ends of the casing are
formed with slots H¹, Fig 4, adapted to fit over the porcelain sockets DI D³
When the casing has been slid down over the sockets D1 D2 and between
springs E, the holes el of the latter spring on to the teeth on the ends of a
plate J fixed to H, thus securely fixing the casing At the same time the
springs F F are put in tension by being pressed upward by the shutters S¹ S
as the casing 18 slid down
For removing the casing, the upper ends of the springs E are pressed ontwards
so as to become disengaged from the teeth 1, whereupon the upward pressure
of the springs FF will at once push up the casing sufficiently to prevent the
teeth from re-engaging with E, so that the casing can then easily be lifted off the
apparatus.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
1. In safety fuse apparatus such as herein referred to, arranging the shutters
as also the fuse strip or wue within an enclosed space formed in a block of fire-
proof material, for the purpose of isolating the electric are formed on burning
from the terminal clamps and other surrounding objects, substantially as
described.
2. In safety fuse apparatus such as referred to in the first claim, arranging
the springs that act upon the shutters within a space formed by a double top to
the enclosing casing of the apparatus, substantially as and for the purpose
described.
3. Safety fuse apparatus for electrical installations combined and operating
as herein described with reference to the drawing.
Dated this 1st day of September 1898
ABEL & IMRAY,
Agents for the Applicants.