Improvements in Automatic Circuit Breakers.
Year: 1896

page_text: Date of Application, 8th Sept., 1896-Accepteri, 28th Nov., 1896
COMPLETE SPECIFICATION.
Improvements in Automatic Circuit Breakers.
We THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, Electrical Engineers,
of 38, Parliament Street, in the County of London, do hereby declare the nature of
this invention (which has been communicated to us from abroad by Edward M.
Hewlett, of Schenectady, County of Schenectady, State of New York, United States
of America) and the manner in which the same is to be performed to be particularly
described and ascertained in and by the following statement:-
The present invention relates to automatic circuit-breakers, which are operated by
an excess of current flowing in the circuit or by hand.
One object of the present invention is to reduce the size and the number of parts to
a minimum, thereby cheapening the cost of construction. The invention further
consists in the arrangement of parts in such a manner that one magnetic device serves
the double purpose of breaking the circuit at a predetermined overload, and at the
same time blowing out the are caused thereby.
A further object of the invention consists in using a single operating handle, which
is secured to the switch blade in such a manner that it automatically releases the
locking device which holds the circuit closed, when it is desired to open the circuit
by hand. The invention also relates to the peculiar construction and arrangement of
the magnetic blow-out and switch releasing mechanism.
In the present invention one energizing coil is used, instead of two as in other
existing constructions, and the magnetic circuit is so arranged that it has two air
gaps, one between the armature, pivoted to the core, which releases the switch locking
mechanism; the other between the opposite end of the magnet core and the top plate;
between the plate and the core are located the switch terminals, so that any are
formed by interrupting the circuit will be disrupted by means of the magnetic lines
of force passing between the top plate and the core. The parts are so arranged that
as the current flowing through the magnetic device increases, one air gap in the
magnetic circuit grows less and less until the switch is automatically released, and a
that instant the magnetic circuit is closed and remains so until the arc is ruptured
and the current ceases to flow, after which it is opened by means of a spring, and the
air-gap is re-established. This is an important part of the invention, for it serves to
decrease the reluctance of the magnetic circuit at the time when the lines of force
are most needed to interrupt the arc. As the current increases, due to the load,
the magnetic circuit is made shorter and shorter, and the blow-out magnet is conse-
quently able to take care of the arc caused by the interruption of the circuit due to a
heavy overload.
In the accompanying drawings we have shown an embodiment of our invention,
in which
Fig. 1 is a plan with the top removed;
Fig. 2 is a section on the line 2-2 of Fig. 1;
Fig. 3 is a section on the line 3-3 of Fig. 1, and
Fig. 4 is an end elevation with the end piece removed.
The box A is made of insulating material, but metal would do equally well; it is
divided into two parts, one containing the magnetic device, and the other the switch
blade and terminals. The magnetic device comprises a core C, to which is secured
the piece C3, the latter forming a support for the armature which actuates the
locking device when attracted toward the U-shaped piece C which forms a portion
of the magnetic circuit. On the opposite end of the core C is a plate C", shown

page_text: .
by dotted lines in Fig. 1. Between this plate and the switch terminals is a piece
of insulation H', and between the switch terminals and the top plate C3 forming a
part of the magnetic circuit, is a second piece of insulating material H. The
U-shaped piece C is secured to the top plate C3 by suitable nuts.
The switch is made in two parts B, B'; the latter is made of copper or other
conducting material heveled at the end where it strikes the side of the box, and
is pivoted to a stud I projecting upward from the casting K to which is secured
the connection from the energizing coil of the magnet. The switch blade is adapted
to make contact with the terminals J, J'; the former is made of laminated copper
and is adapted to carry the greater amount of current; the latter is a simple two-
blade contact engaging both sides of the blade by spring pressure; this is arranged
to break circuit after that of the contact J and therefore the arcing will be done at
this point.
The other portion of the switch comprising the handle-releasing
mechanism is also pivoted on the same stud with the switch blade. Mounted, on the
extension of the handle B is a pin F1 provided with a rounded end adapted to engage
with the cam surfaco F mounted on the arm of the locking device. A spring G
tends to hold the lock in the position shown, thus locking the switch blade against the
action of the spring M. Projecting upward from the blade B' is a stud I which
limits the movement of the handle B independent of the blade. The slot B2 in the
handle B permits a movement of the pin F in order to engage with the cam
surface F to force the projection E down and out of engagement with the blade B
and the parts further bear such relation to each other that when the handle B is
moved far enough to release the locking mechanismn, the circuit is opened with a snap.
for the spring M and lost motion at B2 between the parts of the handle do not permit
of the switch being opened slowly.
For the purpose of adjusting the magnetic pull necessary to open the circuit, a
spring N is secured to the armature and some stationary part of the box A, and
provided with an adjusting nut for the purpose of regulation.
As the current in the circuit increases, the armature ( is drawn toward the
U-shaped piece C, and as the current continues to increase, the air gap between
these parts becomes less and less until finally the opposite end of the armature
engages with the nut on the rod D, and the lug E is pulled out of engagement
with the switch blade, thus allowing it to fly open, due to the action of the spring M.
At this instant the armature would be very near or would make momentary contact
with the piece C, and consequently the magnetic reluctance of the circuit would be
greatly decreased, and a large nuinber of lines of force would flow upward through
the iron to the plate C and back again in the opposito direction to the plate C, which
is a part of the main core. The magnetic lines in passing from the plate (to
would be widely distributed over their surfaces, and any are formed between the
plates would be blown outward and away from the main handle. As it is desirable
to have a fixed distance between the arinature C and the piece C, a block O is
provided which may be readily replaced if worn, or if it is desired to vary the distance
between the armature and the remainder of the magnetic circuit.
Having now particularly described and ascertained the nature of this invention
(as communicated to us from abroad) and the manner in which the same is to be
performed, we declare that what we claim is :-
1. In an automatic circuit-breaker, the combination of a blow-out magnet, a core
for the magnet, a U-shaped piece extending parallel to the core and separated there-
from, a plate forming a support for the U-shaped piece, a second plate of magnetic
material secured to the core of tho magnet, and switch contacts between the plates.
2. In an automatic circuit-breaker, the combination of a blow-out magnet, a plate
forming the top of the core, a second plate of magnetic material parallel to the first
and separated therefrom by an air space, a switch blade and contacts between the
plates, and an armature pivoted to the core of the magnet and adapted to decrease, the
magnetic reluctance of the circuit of the blow-out magnet.
3. In an automatic circuit-breaker, the combination of parallel magnetic plates

page_text: separated from each other by an air space, a switch-blade and contacts, insulation.
between the plates and the switch-blade and contacts, a U-shaped pieco extending
parallel to the core of the blow-out magnet, an armature pivoted to the core and
adapted to decrease the magnetic reluctance of the circuit, and a block to limit the-
downward movement of the armature.
4. In an automatic circuit-breaker, the combination of plates separated by an air
space and forming a part of the magnetic circuit of the blow-out, à switch provided
with a handle having a limited movement independent of the switch-blade, a spring
for breaking the circuit, and a locking detent actuated by an access of current in the
circuit or by a slight movement of the switch handle.
5. In an automatic circuit-breaker, the combination of a blow-out magnet, a core
for the magnet provided with an enlarged top plate, a piece secured to the lower part
of the core and forming a support for an armature, a U-shaped piece extending-
upward from the bottom of the coil to a plate parallel to the enlarged top plate of the
magnet core, main and arcing contacts between the plates, and an armature for
opening the switch and decreasing the magnetic reluctance of the circuit.
6. In a circuit breaker, the combination of a contact for carrying a certain
amount of current, a second or arcing contact for carrying a less amount of
current, and lying in the same horizontal plane with the first contact, a single
operating handle, a mechanically and magnetically operated locking mechanism for
the switch, and a blow-out magnet common to both sets of contacts having a variable:
air gap in circuit.
Dated uns on
For the Applicants,
J. C. CHAPMAN,
70, Chancery Lane, W.C., Chartered Patent Agent..