Improvements in Circuit Breakers.
Year: 1898

page_text: Improvements in 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 Edward M. Hewlett, 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 par-
ticularly described and ascertained in and by the following statement :-
This invention relates to circuit breakers for power stations, or any other relation
to which it is desirable to open a circuit carrying a heavy electric current; it has for
its object especially to provide a reliable and cheap apparatus of the "carbon
contact" type, so called, having a certain delicacy of action not hitherto obtained.
The device is also so arranged that the handle moves down to set the contacts, instead
of moving up, as in many of the devices of this class with which we are familiar.
This arrangement enables me to set the circuit breaker high up on the switch-
board, so that when the circuit is opened the are is above all the apparatus and
is not likely to do injury.
The handle is so arranged that it closes the contacts by a toggle device, between
the handle and a swinging arm carrying the contacts, the range of motion of which
diminishes as the contacts are more nearly closed, so that, while the movement of
the bridging contact is through air, the handle moves comparatively slowly, and the
contact noves rapidly; but after contact is made between the bridge and the
terminals, the movement of the handle is greater and that of the contact less,
so that an increased leverage is obtained, rendering it comparatively easy to close
the contacts.
There is also provided in the circuit breaker a sensitive tripping device working
upon the "overset" principle. The two parts of the trip form a toggle the centre of
which is on one side of the line joining the centres of motion; but when the circuit
breaker is tripped the joint in the toggle is thrown to the other side of the centre
and the toggle opens readily. These two parts are free to move between limits.
In some forms of circuit breaker known to us, the handle by which the apparatus is
managed is separable. In a particular class of apparatus, the handle is a long one
designed to furnish the necessary leverage to close the circuit breaker with certainty.
In addition to the complication of this apparatus, it is objectionable because it may
well happen that the circuit will again open just as the handle is removed, in
which case it is very apt to cause an accident either to the apparatus or to the
operator.
The drawings show an embodiment of the invention.
tion, Fig. 2 is a side elevation partly broken away, and
apparatus inverted.
Fig. 1 is a front eleva-
Fig. 3 is a plan of the
A is a base of any suitable noncombustible insulating material, such as slate, which
is commonly employed for this purpose. B, B' are the circuit terminals, provided with
the flexible extensions or brushes b, b¹. Between these the bridging contact F closes
Above the terminals B, B' are carbon terminals C, C¹. Attached to the
the circuit.

page_text: bridge Fare other terminals D, D¹. The bridge F is inflexible, while D, D¹ are
spring terminals, and they, with the carbon contacts C, C¹ form a shunt to the main
circuit. This arrangement is common in circuit breaking apparatus. The parts are
of course, so adjusted that the terminals D, D₁ break from the carbon contacts after
the bridge is withdrawn from the main circuit, thus diminishing the arc and
rendering it harmless; it being formed between the terminal D and the contact C,
for instance one of which is of copper and the other carbon, the circuit through
which has considerably higher resistance than the main circuit. Between the fixed
contacts or terminals is a shield E of insulating material, which prevents the arc from
jumping from one contact to the other. The bridge is carried upon an arm F¹;
this latter is pivoted at f¹, and is connected with the handle H by the link H². The
handle H has an arm H¹, and the pivot H³ of the handle with the arm H¹ and the
link H2 pivoted to it and to the arın F¹ at f, form a toggle maintained in the illus-
trated position by the latch I¹ and the pawl h.
A spring G attached to the handie H at h¹, and to the arm carrying the bridging
contact at puts the toggle in operation.
The armature I is under the influence of a series coil L through which the current
passes from the stud L¹ to L2 then by the conducting bar L³ to the terminal B. The
latch I is pivotted to the armature I, and, as before explained, forms a toggle to the
pawl h.
It will be seen that the engagement of the pawl is slightly to the right of
the centre joining its pivot and that of the latch. Pins h2, h3 limit the play of the
pawl. A wearing plate i is fixed to the latch I¹ and the adjusting screw 2¹ fixed to
the armature deterinines the amount of lost motion allowed to the latter, some slight
amount being always given so that the armature may give a slight hammer blow, to
readily disengage the latch. As already explained, the latch and the pawl are free to
move between the stops formed by a toe i2 and the adjusting screw for the latch,
and for the pawl by the pins h² h³.
A bar O is pivoted at o at the base of the series coil; through this bar passes a rod
attached to the spring M and having a nut M on its lower end by which the tension
of the spring is adjusted to determine the load at which the circuit will open. The
tripping handle N of the circuit breaker is secured by a pin o to this bar.
Of course
the working parts of the apparatus have a suitable frame P carrying the different
bearings.
The operation of the device is as follows: When current in the coil increases to a
predetermined amount depending upon the tension given to the bearing M which
tends to hold up the armature I the latter is attracted throwing over the latch I¹.
The pivoting of the pawl h renders this action sensitive, inasmuch as there is
practically no static or sliding friction to be overcome. The spring G then throws
down the toggle, turning the handle on the pivot H³ to a horizontal position, and
drawing the bridging contact F to the dotted line position thus opening the circuit.
When the station attendant desires to close the circuit, he draws down the handle to
its illustrated position, when the pawl h again engages the latch and holds up the
armature I.
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 breaker having fixed terminals, a bridging contact carried upon a
swinging arm, a pivoted handle, a spring attached to the arm and to the handle, and
a toggle between the arm and handle acting, when the handle is depressed, to swing
the bridge into contact with the fixed terminals.
2. A circuit breaker having fixed terminals, a bridging contact, a toggle for closing
the contacts, a spring for opening them and a detent for the toggle; the detent
comprising a latch and a loose pawl, one pivoted to the armature of a series coil, the
other to one of the toggle levers.

page_text: 3. In a circuit breaker, the combination with a series coil, an armature, circuit
controlling contacts and mechanism for opening and closing them, of a detent for the
mechanism comprising a latch pivoted to the armature, and a pawl pivoted to the
circuit-controlling mechanism, both free to move between stops.
4. In a circuit-breaker, the combination of a swinging arm carrying the main
circuit contacts, a handle, and a toggle between the handle and the arın.
5. In a circuit-breaker, the combination with the main circuit terminals and a
bridging contact carried upon a swinging arm, of fixed carbon contacts and spring
contacts upon the swinging arm forming with the carbons a shunt to the main circuit
a swinging handle, and a toggle between the arm and the handle..
6. In a circuit-breaker, the combination with the main circuit terminals and a
bridging contact carried upon a swinging arm, of fixed carbon contacts and spring
contacts upon a swinging arm forming with the carbons a shunt to the main circuit,
a swinging handle, a toggle between the arm and the handle, and a detent for the
toggle controlled by the armature of a series coil.
7. In a circuit-breaker, the combination of an armature and coil, a rod attached at
one end to the armature and at the other to a pivoted bar, and a spring attached at
one end to the bar by an adjusting device, and at the other to a fixed part of the
frame.
THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED.
A. R. MONKS,
Managing Director.
ALFRED CLEMENTS,
Assistant Secretary.