Improvements in Electric Circuit Breakers.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 20th Oct., 1900
COMPLETE SPECIFICATION.
Improvements in Electric Circuit Breakers.
We, THE BRITISHI THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of our
said invention (which has been communicated to us from abroad by Harold W.
Buck, residing at Schenectady, 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:-
This invention relates to circuit-breakers or circuit changers and particularly
that type which is used for the opening of circuits carrying high-tension currents.
Various methods have heretofore been employed for subduing or extinguishing
the arc formed between the electrodes or points of contact when they are opened.
One plan which has been afforded considerable practical satisfaction is to submerge
the points of contact within a body of oil, which being a non-conductor and mobile
or fluid in character, smothers the are by enclosing it on itself after its molecules
have been separated by the first effort of the arc to form. This invention relates
more particularly to this latter type of arc-extinguishing device.
We have discovered that after a period of use the oil bath in which the
circuit breaker contacts are submerged deteriorates and become a semi-conductor,
and no longer performs efficiently its function as an extinguisher or preventive of
the arc when the circuit-breaker is operated.
This is, we believe due to decomposition of the oil by the heat or electric
influence of the arc, or both, and the carbonization or decomposition thereof,
permitting the formation of a conducting or semi-conducting carbon residue
which deposits as a sediment on the walls of the containing vessel or remains
suspended within the body of oil. In the effort to overcome this difficulty, we have
ascertained that glycerine does not deteriorate under the influence of the arc in a
manner similar to the other hydrocarbons, as herein before pointed out, but
remains stable and unaltered in condition, with a uniform effectiveness of action.
It is possible that the glycerine instead of being carbonized, is simply volatilized
to a small extent under the influence of the arc; but whether this be true or not,
the body of glycerine in which the are is drawn does not become foul or con-
taminated. We therefore employ glycerine as a vehicle in which to submerge
the electrodes or points of contacts of the circuit-interrupting device. Glycerine
is hygroscopic in character, and in order to prevent the absorption of moisture
and consequent deterioration of its insulating properties, we enclose it in a
waterproof or moisture proof case or receptacle.
This end may be attained in a variety of ways, for example either by making
the enclosure perfectly air tight, or, as we prefer, by employing an open vessel and
covering the body of glycerine with a bed or layer of moisture-repellant material,
such as paraffin, heavy mineral lubricating, olive, rape, sperm or cotton-seed oil..
The oil has no tendancy to mix with the glycerine, and, being of less specific
gravity, floats on its surface, and by its moisture repellant qualities effectually
prevents the glycerine from absorbing moisture from the air.

page_text: Our invention therefor comprises a circuit-interrupter or circuit-changer, in
which the points of contact are submerged within, or separated by, a body of
glycerine. It comprises, further, an organization of the kind just recited, in
which the glycerine is enclosed within a moisture-proof receptacle. It embodies
also other specific features which will be hereinafter definitely indicated in the
claims appended to this specification.
Our invention may be carried out in connection with a variety of apparatus,
such as simple circuit-breakers, switches, fuses, or other types of apparatus, in
which an opening is made between two terminals of an electric circuit while
current is flowing therein.
In the accompanying drawing there is shown, by way of example merely, a
switch embodying our improvements. No claim is made to the structure which
is shown. As will be seen, it comprises a metallic tank 1 supported upon a switch-
board 2, of slate or other fire-proof material, such as is commonly employed in
the construction of switchboards. The tank may be provided with an insulating
lining, as shown, and with pairs of circuit terminals 3, 4, connecting with the
leads 5, 6, extending to a suitable part of the switchboard. The terminals are
mounted upon a support of wood or other insulating material, bolted to a stirrup-
shaped bracket 7 the upper end of which is secured to the switch-board and which
in turn supports the tank as indicated in, dotted lines at 13. A metallic yoke 8
is secured by insulating material 9 to a metal casting or frame which is capable of
rocking on a pivot or axis 10 supported in the two vertical arms of the stirrup 7.
The yoke 8 is provided with two prongs or blades, one of which lies behind the
other in the drawing, which come between the yielding points or terminals of a
double contact 3 or 4. This is a familiar type of double-pole switch, which will
be readily understood by those familiar with the art without specific illustration
or further description.
The switch lever is controlled by a link 11 passing through the switch-board
and connected to an operating lever on the front face thereof, which it has not
been deemed necessary to illustrate. The upper face of the casting on which the
voke 8 is mounted is separated or undulated to co-operate with a retaining pawl 12,
a curved nose or lug on which enters the depressions and serves to maintain the
switch in any position at which it may be set without liability to accidental
derangement.
The glycerine is shown by the heavy broken lines, and the covering layer of oil,
above mentioned, by the light broken lines.
The distinctive feature of this invention is the separation of the points of
contact by a body of glycerine to the end that, however long an arc may follow
the movable member of the circuit interrupter, if there be one, or however far
apart may be the points of contact over which the arc springs,--as in the case
of a fuse,a body of the arc extinguishing fluid will be present over the entire,
or substantially entire, path of the arc. Our invention will therefore easily be
distinguished from devices of a character which are intended to operate with low
tension currents, where a layer of oil, or, as has been sometimes proposed, a layer
of glycerine, is used to shut off the air from a mercury contact and prevent its
oxidation fouling under the influence of a spark. In this organization the entire
field of rupture between the circuit terminals is within the arc extinguishing
liquid.
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-Means for subduing or extinguishing an arc between circuit terminals,
comprising a body of glycerine surrounding said terminals, and wholly submerg-
ing them.
2-A circuit breaker having its movable member which
ODORA
the

page_text: mounted relatively to a body of glycerine so that the contact point describes its
entire path within said body of glycerine.
3-The combination with the terminals, of an electric circuit and means for
opening the same, of a body of glycerine extending between the said terminals,
whereby the arc drawn on rupture of the circuit will have its entire path through
the glycerine.
4 A circuit interrupter having its terminals submerged in glycerine and
enclosed in a moisture proof receptacle.
5-A circuit breaker having its contacts wholly submerged in a body of glycerine
and a moisture repellant bed or layer of oil over the glycerine, as specified.
Dated this 25th day of October 1899.
THE BRITISH THOMSON-HOUSTON CO. LTD.
J. J. MANHEIM,
A. R. MONKS,
}
ALFRED CLEMENTS,
Directors,
Assistant Secretary.