Improvements in Cut-outs and Switches for High Potential Electric Circuits.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION.
Improvements in Cut-outs and Switches for High Potential
Electric Circuits.
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, in the 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:-
The present invention has relation to the interruption of high-potential electric
circuits. This has been attended with great difficulty on account of the persistent
arcs which are formed where such circuits carry current of any considerable
amplitude. Ordinary circuit-breaking devices, which are operative and useful
at potentials such as are commonly employed, are readily spanned by the arcs on
high-potential circuits, and may be easily destroyed. If the devices usually em-
ployed are applied to high-potential circuits, the switches become of such great
size in order to get the necessary extent of motion and length of opening as to
become uncommercial and impracticable.
To obviate the difficulties attendant upon old constructions, we have devised
the present invention. While to some extent this utilizes principles which are
known in the art, it does so in a different way from any construction with which
we are familiar, and has distinctive features which enable it to perform its func-
tions with certainty. At the same time it is of moderate cost and is capable of
almost indefinite application to circuits of any potential. The construction
consists in general of a bridge the parts of which are enclosed within tubes of
insulation, and contacts are provided within tubes, they being stationary. When
the bridge is removed the arc springing from one contact to another heats the
air and expels the bridge with considerable force, so that the arc is ruptured.
There are details of construction which.also are of our invention, but its use
and operation will be pointed out after the description, in connection with which
they will be more readily understood.
The accompanying drawings show an embodiment of the invention. In these
Fig. 1 is a front elevation of the circuit-breaker: Fig. 2 is a side elevation,
partly in section, upon the line 2-2 of Fig. 1: Fig. 3 is an enlarged view, partly
in section, with parts omitted for clearness, of a section taken upon the line 3-3
of Fig. 2; Fig. 4 is a plan view of the device inverted, with parts in section,
taken from the line 4-4 of Fig. 2.
A is the usual base, of non-combustible insulating material, such as slate,
and B is the interposed septum of refractory insulating material. C, C are
the tubes of insulation. At the head of each of these tubes is a terminal C¹
provided with interior flexible contacts C3 between which ends of the rods D
and D¹ are inserted, as shown best in Fig. 2. A nut C2 closes the top of the
tube, making a practically air tight chamber. A bolt E' connects the ter-

page_text: minal C¹ to the lead G on the back of the board, insulators E, E being provided
where required.
Another view of the same parts is shown in Fig. 3, where the construction
of the bridge is more clearly indicated. It consists, as will be seen in this figure,
of the two rods (which of course are of good conducting material, such as copper),
D, D', connected by the metallic piston 12, which co-acts with the dash-pot M
(see Fig. 2) to check the motion of the bridge after the circuit is ruptured. The
dash-pot is preferably pneumatic, as this gives the increasing retardation which
is desirable in our construction. It is provided with a bottom M', which acts
as a valve, permitting the ready closure of the circuit. The bottom or plug M¹
has a hole m in which a stick or other non-conducting bar may be inserted to
close the circuit, this being readily effected by pressing up the plug M², carry-
ing with it the piston D2 and forcing the rods D, 'D' into engagement with the
upper terminals.
In Figs. 2 and 4 the tripping device is illustrated. This consists of the
magnetic frame H from which projects a yoke H¹. A core I¹ having a boss i
reciprocates within the series coil I, a screw K being provided by which, the
calibration is effected. A bell-crank lever L with a spring and a pawl 2 recipro-
eating between stops 13 engages with a pawl L', which is fast to the piston 1)².
A spring N coiled around a rod N¹ operates upon a pin n fixed in the rod. The
pawl L, which is rigid with the piston D3, abuts against the end of the rod N
so that when the latter is pushed up in resetting the circuit-breaker, the pin
engages with the collar of the spring N and forces it up. This spring may
be of only sufficient power to positively overcome the friction upon the bridge
of the terminals C³.
The operation of the device will be readily apparent, but may be briefly as
follows: when the current in the coil I exceeds the determined value for which
the device is set to act by adjusting the screw K, the plunger I is drawn up
forcibly and strikes the bell-crank L, withdrawing it from the pawl L¹ and
releasing the latter. The spring N then opens the circuit; as the arc springs
from the flexible contacts to the bridge, the air in the closed terminal C becomes
enormously heated and enlarged in volume, blowing open the circuit with con-
siderable force, which is taken up by the dash-pot M. Of course all these
actions, though here successively described, are practically instantaneous.
We have found the device compact and efficient in its operation, avoiding
almost entirely the difficulties incident to opening high potential circuits.
"
It is quite manifest that the same arrangement here described could be utilized
as a switch for manual operation if desired. In that case, instead of using a
current measuring device, the latch can be tripped by hand, and as the parts are
then left free to move, the resulting rupture of the circuit will be effected with
certainty. Furthermore, it is manifest that without invention and still within
the scope of the claims appended, changes may be made in the construction,
whether the switch be adapted to automatic operation or not; a thermal device
could be used in place of the current-measuring coil, in ways too well understood
to require description, and various other changes might easily be made.
Having now particularly described and ascertained the nature of our said "in-
vention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is :-
1-In a circuit-breaker for high potentials, the combination of closed chambers
containing terminals, tubes extending from the chambers, and a U-shaped
bridge enclosed in the tubes and making contact with their terminals in the
chambers, with a current-measuring device and a trip actuated thereby.
2 In a circuit-breaker for high potentials, the combination of the closed
terminals containing flexible contacts and disposed adjacent to one another upon
a suitable base, an insulating septum between the terminals, tubes of insulating
material extending from them, a pair of copper rods and a block connecting

page_text: them forming a U-shaped bridge, with a dash-pot registering with the block,
and a current-measuring coil and trip.
3 In an electric switch, the combination of a closed chamber containing
flexible contacts, a tube extending from the chamber and a rod of conducting
metal enclosed in the tube extending into the chamber and making a circuit
with the flexible contacts.
4-In an electric switch, the combination of the closed chambers with flexible
contacts contained therein, tubes of insulating material extending from the
terminals, and a U-shaped bridge composed of a pair of copper rods joined at
their outer ends extending within the tubes and completing the circuit at the
flexible contacts contained in the closed chambers.
5 The combination with a circuit-breaker, of a piston connected to the circuit-
opening contact, and an aerial dashi-pot connected to the piston; whereby the
opening of the circuit is not primarily retarded, but the shock of the switch move-
ment is taken up.
6-The combination with the U-shaped bridge, of the piston D2 and the dash-
pot M, having a movable bottom acting as a valve, by means of which the bridge
may be restored to position.
The combination with the bridge of the circuit-breaker, of the piston D³
and the dash-pot M, with, the movable bottom M¹ having a recess m, for the
purpose set forth.
8 The combination with the U-shaped bridge, of the guide-rod and spring,
the piston, and the pawl or detent rigid with the piston and abutting against
the guide-rod to reset the switch.
9 The combination of the U-shaped bridge enclosed within tubes of insulat-
ing material, with the guide-rod, spring and current-measuring coil and the trip,
the ends of the bridge completing the circuit within closed chambers containing
flexible contacts, the spring adapted to overcome the friction of the contacts
when the circuit-breaker is tripped and the bridge is expelled from the tubes
by the expansion of the air in the terminals.
8511
1
1000
THE BRITISH THOMSON-HOUSTON CO. LTD.,
J. J. MANHEIM,
A. R. MONKS,
}
Alfred CLEMENTS,
Directors.
Assistant Secretary.