Improvements in Electric Circuit Changers.
Year: 1899

page_text: Date of Application, 11th Nov., 1899-Accepted, 16th Dec., 1899
COMPLETE SPECIFICATION.
Improvements in Electric Circuit Changers.
We, THE BRITISH 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 Eustace
Oxley, of Lynn, County of Essex, State of Massachusetts, 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:-
Our invention relates to switches or circuit-changers for electric circuits, our
purpose being to provide a device for opening and closing a circuit without
moving either switch-terminal, the current being interrupted by the inter-
position of a non-conducting wall between two terminals connected by a conduct-
ing liquid. It is also an object of our invention to permit the circuit to be
opened or closed by the exertion of a merely nominal power, whereby automatic
circuit-breakers and similar devices can be operated automatically by means of
great simplicity, which can be manufactured at very low cost. It is a further
object to provide a device simple and cheap in construction, which will accom-
plish these results, and which can be operated by controlling devices of small
power.
11011-
The invention comprises a current controller, in which the terminals are or
may be connected by a liquid conductor, and means for interposing a
conducting diaphragm between them; it comprises also a device of this kind
having fixed circuit terminals and a movable diaphragm of insulating material:
it also comprises other more specific features which will be hereinafter described
and claimed.
In the drawings, which show a simple organization embodying our invention,
Fig. 1 is a side elevation of a device embodying our improvements; Fig. 2
is a vertical section on a plane parallel to that on which Fig. 1 is projected.
The reference numeral 1 in said drawings indicates our preferred form of
containing vessel, formed of conducting material, such as iron, aluminium, or
other suitable material, although we may use a vessel formed of non-conducting
substance but provided with a conducting lining. This containing vessel holds,
when in use, a body of conducting liquid 2: we prefer to use mercury, but
conducting liquids of other character such as electrolytes might be employed.
Dipping into the mercury and immersed to a suitable depth therein is a
circuit-terminal, or contact 3, preferably of semi-circular form, though any
other shape is consistent with the purposes of this invention. The contact 3
is rigidly secured in place and remains permanently in the mercury.
Upon suitable supports or bearings a shaft 5 is mounted, upon which is rigidly
fixed a semi-circular shell or hood 6. having approximately the form of the
contact 3, but of such increased dimensions that it can coulain or enclose the
latter. Suid shell is formed of or covered with any suitable insulating or
non-conducting substance, such for example as hard rubber, glass, porcelain,
wood covered with paraffin or varnished, metal having an insulating coating, etc.
It is so arranged upon the shaft 5 that as the latter is turned in one direction
said hood will enter the mercury and pass around and enclose the contact 3,
its edge, when movement is arrested, rising above the surface of the mercury.
A small portion of the latter will also be enclosed by the shell or hood, but the
interposition of a non-conducting wall between the main body of mercury and
A reverse movement
the switch terminal 3 completely cuts off the current,

page_text: establishes the circuit by simply withdrawing the wall interposed between the
two conducting bodies, riz., the mercury and the terminal lying therein.
We have shown in this instance a single pole switch only, but it is evident tha
the application of our invention to a multipole switch involves merely a duplica
tion of the parts already described.
Thus we provide a switch which can be operated quickly, and requires, practi
cally speaking, only a nominal power for its operation. By counterbalancing
the shell or hood 6 upon the shaft 5, a slight force upon the shaft will turn the
hood. As the latter can be made of thin material, it is light, causes no sensible
rise and fall of the mercury by displacement, and produces no flash, or agitation
of the same upon entering or leaving said mercury. As the shaft is the only
part on which any action is exerted, the switch contact and the mercury and
hood may be placed in a hermetically sealed housing, thus excluding dust, dirt
and moisture, and entirely preventing loss of mercury by volatilization.
This switch is ordinarily adapted for use as a circuit-breaker, since it can
be operated by a small and comparatively weak electro-magnet, or other auto-
matic means. It can be used upon any circuit and with any current, and its
simplicity and small size enables it to be produced at an extremely low cost.
We have shown in the drawing a simple structure to effect magnetic control.
7, representing an armature playing between and controlled by electro-
magnets 8, 8; to provide a considerable range of armature movement, the
magnets may have tapering or paraboloidal pole-pieces as shown, the armature
being bored to permit its passage over the pole pieces, thus permitting a amall
hir-gap and a long throw; the free end of the armature may carry a rack sector
engaging a pinion on shaft 5, as shown.
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-A circuit-changer comprising circuit terminals, one of which is a liquid
conductor, and means for interposing an insulating medium between them.
2- circuit-changer comprising two circuit terminals, one of which is a
conducting liquid, and a movable non-conducting wall to separate the terminals
or permit their contact.
3A circuit-changer comprising two terminals, one of which is a conducting
liquid enclosing the other, and a movable hood having insulating walls to
enclose the metallic terminal and open the circuits.
4-A circuit changer comprising a conducting liquid such as mercury, a
contact or terminal lying therein, and a non-conducting shell or hood arranged
to enter said liquid and pass around and enclose the contact, its edge rising suitably
above the surface to rupture the circuit.
A circuit changer comprising a body of conducting liquid such as mercury,
a switch contact or terminal lying permanently therein, a non-conducting shell
or hood mounted on a shaft and adapted to turn therewith and enter said liquid,
surround the contact lying therein and rise suitably above the surface, whereby
said circuit is opened, and means for operating said shaft.
Dated this 31st day of October 1800
THE BRITISH THOMSON-HOUSTON CO. LTD.,
W. MARTINDALE,
A. R. MONKS,
Directors.
ALFRED CLEMENTS,
Assistant Secretary.