Improvements in Thermostatic Electric Circuit Breakers.
Year: 1899

page_text: Date of Application, 30th June, 1899-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION.
Improvements in Thermostatic Electric Circuit Breakers.
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 Caryl D. Haskins,
residing at Newton, in the County of Middlesex, 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:.
-
The present invention relates to thermostats, and is particularly adapted to
the construction of thermally-actuated circuit-breakers. One of its principle
advantages is that it affords a convenient way of constructing circuit-breakers
of small capacity, which may be used in place of fuses without the expense atten-
dant upon the ordinary coil of electro-magnetic structures. The particular form
of thermostat employed consists of a tube of conducting metal hermetically sealed
and enclosing a few drops of a liquid, such as chloroform, ether, or some other
hightly volatile substance. By preference the tube is flattened and is bent into
a or other curved shape. Upon attaining a critical temperature the liquid vola-
tilizes and straightens out the tube with considerable energy. This action we aim
to take advantage of to close or open a circuit or to effect the movement of any
desired part of a mechanism.
The accompanying drawings show the invention as applied to a circuit-breaker,
though other applications of it will readily occur to those skilled in that art.
In them, Fig. 1 shows a front elevation, and Fig. 2 a side elevation, of an electric
circuit-breaker to which the invention is applied; Fig. 3 shows a means for
adjusting the device, and its combination with a magnetic circuit-breaker.
Referring by letter A is the base of the apparatus, constructed on the usual
non-combustible insulation. B, B are the terminals, C is a bridge of flexible con-
ducting metal connecting them. D, D are spring contacts bearing upon carbon,
blocks E, E, making contact and breaking it after the bridge C, for purposes well
understood in the art, the two sets of contacts being arranged in multiple. A
lever F connected to the link G and handle H serves to close the circuit.
link G and the handle form a toggle which is held in its extended position by a
The
lever Land link M forming another toggle, a spring N serving to cramp the
second toggle slightly out of line.
trip formed by the second toggle is forced down in any way.
A spring I forces open the circuit when the
A rod H¹ may be
ased to open the circuit by hand when desired, by pulling open the lever L.
Studs 0, 0¹ are connected to the circuit-breaker terminals so that they are in
eries in the path of the current. The thermostat of this invention is illustrated
t P. In the construction of the circuit breaker two of these are preferably em-
loyed, connected by a bar of conducting metal Q, the letter being enclosed in the
ube R of insulating material which bears upon the lever L so as to trip the
ircuit-breaker when the thermostats expand under the influence of the current
which they are adjusted. The path of current is from the left-hand stud O to
hich it passes from the lower terminal B, through the first of the thermostats,
D77

page_text: across the bar, through the second thermostat and to the second stud O¹, which
is connected by a link (shown in dotted lines in Fig. 1 and arranged upon the back
of the switch base), to the first of the contacts spanned by the bridge C.
By adjusting the amount of metal in the tubes 1 their current-carrying capacity
may be also adjusted so that when it is exceeded the heat generated will be
sufficient to volatilize the liquid contained in the thermostatic device and open
que circuit-breaker.
A convenient way of effecting this adjustment is shown in Fig. 3. Here the
thermostat P, hung from the stud 0, completes the circuit over the branch
wires c,
d from the mains a, b leading from the generator D E; lamps T compose
the load. A tilting lever S, balanced by a spring S¹, carries a contact S2 which is
in circuit with the coil X of a circuit-breaker C B on the lead o.
A slider ?' moves
over the thermostat and is connected to the mains by a flexible conductor so that
different lengths of the tube may be included in the circuit. With this arrange-
ment, when the tube straightens out it closes the contact $2 completing a circuit
through the coil X and operating the magnetic circuit-breaker C B. Of course if
desired the arrangement might be like that shown in Figs. 1 and 2, and the
slider could be employed to short-circuit a greater or less length of the tube or
tubes as might be desired. This it has not been deemed necessary to illustrate
specifically, as it will be clear to the engineer from the arrangement shown in
Fig. 3. It is manifest that if the slider be so moved as to bring the whole tube
in circuit, the resistance will be increased and the heat generated raised, while if
the tube should be entirely cut out, the current flow would have no effect upon it.
Thus the device may be calibrated within any desired limits.
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 combination with a circuit-breaker, of a trip and a thermostat acting
upon the trip and included in a path for the current, the thermostat consisting of
a tube of conducting metal enclosing a liquid.
2. The combination with a circuit-breaker, of a thermostat for operating the
trip, comprising a curved flattened tube of conducting metal, included in a path for
the current and enclosing a volatile liquid.
3. The combination with a thermostat in an electric circuit, of means for includ-
ing a greater or less length of the device in the path of the current.
4. The combination with a thermostat and an electric circuit, of a slider, and a
flexible conductor by which a greater or less length of the device may be included
in the circuit.
5. The combination with a thermostat and means operated by the thermostat for
opening an electric circuit, of an adjusting device by which a greater or less
length of the thermostat may be included in the circuit so as to determine the
current value at which the circuit will be opened.
6. The combination with a thermal device for opening an electric circuit, of
means for varying the point at which the current flow will actuate the device.
Dated this 20th day of June 1899
THE BRITISH THOMSON-HOUSTON CO., LTD.
W. MARTINDALE,
A. R. MONKS,
ALFRED CLEMENTS,
}
Assistant
Directors,