Improvements in Electric Fuses.
Year: 1898

page_text: Date of Application, 6th Oct., 1898-Accepted, 3rd Dec., 1898
COMPLETE SPECIFICATION.
Improvements in Electric Fuses.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street, in
the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by William Leroy
Emmet, residing at Schenectady, in the County of Schenectady, State of New York,
United States of America, Electrical Engineer) and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
:
The present invention relates to a method of and apparatus for extinguishing the
are formed by the blowing of a safety fuse. The object of the invention is to provide
a fusible cut-out in which the arc formed by the melting of the fuse will be quickly
and with certainty broken and blown out.
The nature of this invention will be more clearly apprehended by reference to the
following description, taken in connection with the accompanying drawings. The
scope of the invention will be particularly pointed out in the appended claims.
Fig. 1 is an end elevation of a cut-out made in accordance with the invention.
Fig. 2 is a side view of the same.
The cut-out proper is composed of a base plate 1 of insulating material, having
attached thereto side plates 2, 2, which serve as guards. Mounted on the base
plate at suitable distances apart are two castings having ears 3, 3. Pivoted to each
pair of ears is a bifurcated or U-shaped spring-actuated arm 4. The actuating
spring 5 is coiled about the pivot 6 between the bifurcations of the arm 4. One end
of the spring engages the arm and the other end the body of the supporting
casting 7. The springs are so arranged as to urge the upper ends of the arms away
from each other.
Suitable clamping devices 8 are arranged at the outer extremnity of the arms
between which a fuse 9 is secured, so as to hold the arms in a position perpendicular
to the base 7, as shown. The fuse is thus normally maintained in a state of tension.
Permanently mounted between the arms and overlapping an end of each of the
castings 7, is a block of insulating material 10. Superposed thereon
renewable blocks 11 and 12, of insulating material, each block having a hollow
formed therein, so that, when placed together as shown in the drawing, a chamber 13
is formed. An opening 14 in the upper block 11 communicates with the chamber
so formed.
are two
The arms and insulating blocks are so proportioned and arranged as to allow the
fuse 9 to pass freely between the blocks 11 and 12, and through the chamber 13.
That portion of the fuse passing through this chamber is made of smaller cross
section than the remaining parts, in order to insure the formation of the arc within
the chamber instead of between the insulating blocks.
In order to prevent any possibility of the arc formed in the chamber 13 from pass-
ing out of the opening 12 and then to either the spring actuated arms, it is found to
be advisable to provide barriers which in this case are plates, 22, of fibre, or other
insulating material, sliding in grooves in the side plates 2. The barriers, together
with the insulating blocks are all held in place by bolts provided with thumb-

page_text: screws 15. By removing the thumb-screws and pressing back the bolts, the barriers
may be slid out of the grooves and so withdrawn, in order to permit the insertion or
renewal of the fuse.
In order to make connections with the fuse, the castings 7 are provided with fins 16
which extend through the base plate and are adapted to engage spring clips 17 carried
by the connecting bolts 18.
The connecting bolts are passed through a bushing 19, which is fitted in an opening
in the switchboard 20. Insulators 21 fit over the reduced ends of each of the bush-
ings. The insulators and bushings are held firmly in place by the clamping nuts on
the connecting bolts.
When the fuse blows, the air within the central recess or chamber is very suddenly
heated, and the resulting pressure causes the vaporized metal and other gases to be
violently expelled through the opening in the chamber, thus blowing out the arc.
As soon as the fuse parts, the spring arms come into action and instantly withdraw
the ends of the fuse from the chamber and from contact with the insulating blocks.
By the simultaneous expulsion of the gases from the chamber, and the withdrawal
of the fuse ends, the continuance of the arc formed by the rupture of the fuse is
rendered practically impossible.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is :—
1-The method of extinguishing an arc, which consists in impulsively expelling
the gases generated by the heat of the arc from the vicinity of the terminals between
which the arc is formed, and simultaneously therewith causing a separation of the
terminals.
2-The method of extinguishing the are formed in the operation of a fusible cut-
out, which consists in normally confining the destructible portion of the fuse within
a chamber having a constricted opening, and instantly withdrawing the fuse
terminals when the fuse melts.
3-The combination of insulating material with a chamber therein having an
orifice, terminals for the ends of the fuse adapted to pass through said chamber, and
barriers for preventing the formation of an arc between the mouth of said orifice and
said terminals.
4-The combination of insulating material having a chamber formed therein with
opening in communication therewith for allowing the free passage of a fuse across
said chamber, and means for exerting tension on said fuse.
5. The combination of insulating material having a chamber formed therein,
spring-actuated arms, and means for securing a fuse to the free ends of said
arms.
6-In a fusible cut-out, the combination of a fuse, means for maintaining the fuse
under spring tension, and means for confining the destructible portion of the fuse
within a chamber having a constricted opening.
7-The combination of spring-actuated arms, a fuse secured to the arms and main-
tained under tension, and means for confining the fuse within a chamber formed in
a body of insulating material.
Dated this 1th d 1000
Doted this 4th day of October 1800.
THE BRITISH THOMSON-HOUSTON CO., LTD.
W. MARTINDALE,}
A. R.
ALFRED CLEMENTS,
Directors.
Assistant Secretary.