Improvements in Incandescent Electric Lamps and Cut-out Devices therefor.
Year: 1887

page_text: Date of Application, 13th Dec., 1887
Complete Specification Left, 5th Sept., 1888
Complete Specification Accepted, 26th Oct., 1888
RESERVE
PROVISIONAL SPECIFICATION.
Improvements in Incandescent Electric Lamps and Cut-out Devices
therefor.
1, THOMAS ALVA EDISON of Llewellyn Park, in the County of Essex, and State of
New Jersey, in the United States of America, Inventor, do hereby declare the nature
of this invention to be as follows:-
This invention relates to incandescent electric lamps designed to be used in series
with one another and to employ currents of high tension. When lamps are used in
this way;
if the filament of a lamp breaks, an arc is usually formed by the high
tension current across the broken filament which arc will, if it is not checked or
broken continue down the wires leading into the lamp, through the glass and down to
the socket and so destroy not only the lamp and its socket, but the continuity of the
series circuit, and extinguish all the other lamps in series.
In consequence of this formation of the arc it is impossible to use with such
lamps any of the ordinary forms of cut-outs such as are designed to act to
close a circuit around the lamp when circuit within the lamp is broken.
The object of this invention then is to provide a simple and effective form of
cut-out for incandescent electric lamps, which will be operated by the arc itself so
as to short circuit or cut-out the lamp and maintain the circuit of the lamps in
series with it.
The lamp consists, as usual, of a glass vacuum chamber and a carbon filament
placed therein. The chamber or globe has a base of insulating material such as
plaster, provided with a screw threaded contact band, and a bottom contact ring or
disc of annular form. These make contact respectively with the screw threaded band
and bottom contact plate of the socket in which the lamp is placed, to which band
and plate the wires of the external or series circuit are connected. The leading
in wires extending to the filament and sealed in the glass at the end of the
inner stem of the lamp are connected respectively to the contacts on the lamp
base.

page_text: The base is made hollow below the lamp and carries within it a metal plate, a
chamber being left within the base below said plate.
A fine wire is sealed in the glass of the stem between the leading in wires and
extends up into the lamp between the sides of the filament. At its outer or lower
end it terminates in a small metal rod which passes loosely through the metal plate
within the base and extends close to, but not into contact with, the bottom plate
of the socket.
Surrounding this rod and attached to it at its lower end is a spiral spring
which bears against the plate, through which the rod passes and which is connected
by a short wire passing through the base to one of the leading in wires.
The parts are so arranged that when the lamp is in operation the spiral spring is
compressed the rod being held up by the fine wire--and is in readiness to force the rod
down when it is released.
Upon the breaking of the filament, when the are forms across it, the fine wire
which extends within the lamp, being connected by the short wire above mentioned
with one side of the circuit, receives so much of the heavy current as to fuse it,
whereupon the metal rod is released, and the spiral spring at once forces said rod down
against the bottom plate of the socket whereby circuit is closed between the wires of
the external or series circuit through the screw threaded bands of the socket and
base, the said short wire, the spiral spring and the bottom plate of the socket,
whereby the broken lamp is cut out and the circuit of the series completed
around it.
1011 1
1001
THOMAS ALVA EDISON.
By Harris & Mills,
23, Southampton Buildings
Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in Incandescent Electric Lamps and Cut-out Devices
therefor.
I, THOMAS ALVA EDISON of Llewellyn Park in the County of Essex and State of
New Jersey in the United States of America Inventor do hereby declare the nature
of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
This invention relates to incandescent electric lamps designed to be used in series
with one another and to employ currents of high tension. When lamps are used in
this way, if the filament of a lamp breaks, an arc is usually formed by the high
tension, current across the broken filament, which are will, if it is not checked or
broken, continue down the wires leading into the lamp, through the glass and down to
the socket and so destroy, not only the lamp and its socket, but the continuity of the
series circuit, and extinguish all the other lamps in series.
In consequence of this formation of the arc it is impossible to use with such lamps
any of the ordinary forms of cut outs such as are designed to act to close a circuit
around the lamp, when circuit within the lamp is broken.
The object of this invention then is to provide a simple and effective form of
cut out for incandescent electric lamps, which will be operated by the arc itself,
so as to short circuit or cut out the lamp and maintain the circuit of the lamps
in series with it.
The invention is illustrated in the accompanying drawing.
Figure 1 is a view in elevation of a lamp provided with a cut out, embodying the
invention, with its base in section; and
Figure 2 is a similar view on a larger scale of the lower portion of said lamp.
A is the glass inclosing globe, B the stem or inside part and C the carbon filament
of an incandescent electric lamp. D is the base of insulating material provided with
a screw threaded contact ring a, and a bottom contact disc or ring. These make
contact respectively with the screw threaded band and bottom plate of the
socket E, to which the external circuit wires e. e. extend. The leading in wires f.f¹
extending to the filament C and sealed in the glass at g are connected respectively
to the contacts a and b.
The base D is hollow below the lamp and carries within it a metal plate h, a chamber
being left within the base below said plate.
A fine wire is sealed in the end of the stem and extends up into the lamp between
the sides of the filament. It terminates at its lower end in a small metal rod k, which
passes loosely through the plate h and extends close to, but not in contact with, the
plate d of the socket.
Surrounding the rod k, and attached to it at its lower end, is a spiral spring /
which bears against the plate, and which is connected by a short wire m to the
leading in wire f.

page_text: When the rod k is in the position shown, the spring is compressed and in readiness
to force the rod down when it is released. This is the position of the parts when the
lamp is in operation.
Upon the breaking of the filament, when the arc forms across it, the fine wire i
being connected with one side of the circuit through wire m, receives so much of
the heavy current as to fuse it, whereupon the rod k is released and the spring
at once forces it down against the plate d, whereby circuit is closed between the
wires e. e. of the external circuit, through rings or bands a and C, wire m,
spring and plate d, and the broken lamp is cut out and the circuit of the series
completed.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
The incandescent electric lamp provided with a spring cut out held out of action
by a fine wire situated between the leading in wires, whereby, when said wire is
fused, the cut out is released and the lamp is cut out of circuit substantially as herein-
before described.
THOMAS ALVA EDISON.
By Harris & Mills,
23, Southampton Buildings,
Agents.