Improvements in Incandescent Electric Lamps.
Year: 1898

page_text: Date of Application, 1st Mar., 1898-Accepted, 9th July. 1898
Improvements in Incandescent Electric Lamps.
A communication by JoHN THOMAS LISTER, Electrician, and WILLIAM SELAH
CHAMBERLAIN, Gentleman, both of Cleveland, Ohio, United States of America.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester,
both in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, and 322, High Holborn, in the County of Middlesex, Civil Engineer,
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 consists in improvement in incandescent lamps, and the objects
of the invention are to provide a single lamp bulb with two filaments and with
means for connecting either filament separately with the lamp circuit through the
circuit contacts, whereby when one filament has burned out the other can be
placed in the circuit and the life of the lamp thereby prolonged.
. This invention consists in the arrangement with a bulb sealed at the base
extremity, of two filaments placed side by side and two pairs of terminals thereby
extending through the sealed extremity and spring circuit contacts upon the base
of socket, so arranged as to make contact with only one pair of terminals at a
time, the change of contacts from one pair of terminals to the other being made
by rotating the bulb.
This invention has further reference to the manner of sealing the bulb, and
arrangement of socket and base therewith.
This invention further consists in the combination of parts and construction
of the various details as hereinafter described, shown in the accompanying draw-
ings, and specifically pointed out in the claims.
In the accompanying drawings Figure 1 is an elevation of the lamp showing a
socket and switch attached, and the arrangements of the terminals and spring
contacts: this portion being in vertical section: Figure 2 is a bottom view of the
bulb showing the position of the contacts springs graphically in dotted lines:
Figure 3 is a modification of the upper part of the bulb and base: Figs. 4 and 5
are views of bottom of bulb and base detached: Figs. 6, 7 and 8 are modifications
of base.
In these views 1 is the bulb provided with the bulb-like extremity 2 separated
from the main portion by the annular recess 3. 4 is the cylindrical casing of the
base, which is provided with the semi-circular spring 5, the extremities 6 of which
7 is the base proper,
enter the recess 3 and secure the base tightly to the bulb.
upon which is placed the spring contacts 8 and 9. Both contact springs are
arranged upon a circular plan, one 8 being shorter than the other.
10 and 11 are filaments, which extend through the double annular stem 12 and
are provided with the metal terminals 13 and 14.
The filaments are arranged side by side and the metal terminals are placed

page_text: individually in a porcelain disc 16. By this arrangement the filaments can be
made exactly of the same size and length since they are of exactly the same candle
power.
The space within the stem is filled with plaster of Paris or other non-conducting
material 15, and the thin disc 16 of porcelain or other hard non-conductor further
protects the stem, outside of which appear the metal terminals 13 and 14.
This bulb is sealed at the stem extremity instead of at the large end as formerly
and the central tube is inserted and sealed at the extremity, making the insertion
of the filaments extremely easy.
The stem is then filled with plaster of Paris or other cement and the disc 16
covers and protects the seal.
It will be readily seen in Figure 2, that while the longer contact spring covers
two terminals at a time, as 13 and 14 at the bottom of the figure, the shorter one
will only make contact with one terminal as 13, therefore only the terminals 13
would be in the circuit and only the filament 10 will glow.
However by turning the bulb half way around, the base would remain stationary
and the terminals would change their relative position, one of the terminals 13
being out of contact with the spring contacts and the terminals 14 would then take
the place of the terminals 13, in the figure.
In either position one terminal will always be out of contact with the spring
contacts and therefore one filament will always be out of the circuit.
7 is
In the modification, Figure 3, the extremity 2 of the bulb is shown somewhat
elongated and has the annular rebated portion or recess 3. 4 is the cylindrical
casing of the base, which is provided with the semi-circular spring 5, the extremi-
ties 6 of which enter the recess 3 and secure the base tightly to the bulb.
the base proper, upon which are secured the spring contacts 8 and 9. In this
instance the contacts are made longer, the base 7 being set higher up in the
casing 4. Both contact springs are arranged upon a circular plan, one 8 being
shorter than the other. The filaments extend through the double annular stem 12
to tho metal terminals placed individually in the porcelain disc 16.
The space
within the stem is filled with a suitable non-conducting material. The stem has
a flattened surface upon which the disc 16 bears, and the latter is provided with a
peripheral flange that clamps the extremity of the bulb. The base proper is con-
tiguous the extremity of the casing, and the conducting wires lead direct to the
contacts, the switch being omitted. The bulb operates in a similar way as that
just described with reference to Figure 2.
My correspondents believe themselves to be the first to provide a bulb sealed at
the base end and provided with a multiple number of filaments of equal candle
power, arranged as shown side by side, and to provide a suitable arrangement of
terminals and contacts for that manner of arranging the filaments.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is:-
1. In an incandescent lamp, the combination with a bulb provided with two
filaments and two pairs of terminals, the said filaments being placed side by side,
of a base and circularly shaped spring contacts therein, one of said contacts being
shorter than the other, whereby the shorter contact will engage only one terminal
at a time, and means for rotatably securing the bulb to the base, substantially as
described.
2. In an incandescent lamp, provided with two filaments arranged side by side,
the combination therewith and with the individual terminals of the filaments
exposed upon an insulating disc, of a base provided with a switch mechanism,
and circularly shaped spring contacts for the lamp circuit mounted, upon said base,
one of said contacts being shorter than the other, and means for rotatably
supporting the bulb upon the base, substantially as described.
3. In an incandescent lamp, the combination with a bulb, base and switching

page_text: device, of two filaments of equal candle power having their terminals extending
through the bulb, and individually exposed upon a porcelain or other insulating
disc, and two circuit contacts in the base, adapted to make contact with the fila-
ments one pair at a time, when the bull is rotated upon the base, and means for
securing the bulb rotatably in the socket consisting of a wire spring upon the
socket and an annular recess in the bulb, substantially as set forth.
4. In an incandescent lamp, a bulb sealed at the base extremity and provided
with two filaments of equal candle power arranged side by side, the said filaments
being provided with terminals exposed upon the exterior of an insulating surface
and individually metal coated, in combination with two spring contacts, one being
shorter than the other to include only one terminal at a time, a metallic ring over
the stem of the lamp provided with an annular depression and a wire spring
enclosing one half of the base, the two extremities of which project inwards and
into the annular depression, whereby the bulb is secured rotatably to the base,
substantially as described.
5. In an incandescent lamp, a bulb stem provided with an annular recess and
central tube at the extremity of which the lamp is sealed, in combination with an
insulating filling for the annular recess in the stem, and a projecting disc, and a
multiple number of filaments arranged side by side and of equal candle power,
the extremities which extend through said disc and filling, and end in metal
terminals, substantially as described.
Dated this 21st day of February 1898.