Improvements in Electric Incandescent Lamps.
Year: 1892

page_text: Date of Application, 12th Jan., 1892
Complete Specification Left, 11th Nov., 1892-Accepted, 17th Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in Electric Incandescent Lamps.
GODFREY BAMBERG Chemist 17, Weston Road Southend-on-Sea do hereby
declare the nature of this invention to be as follows:-
My invention relates to an improved manufacture of the filaments for use in
electric incandescent lamps in such manner that they can be rendered incandescent
by the electric current without the necessity of their being enclosed in a vacuum,
& shall not be consumed when highly heated in air, together with method of
connecting improved filament with the electrodes.
The incandescent lamps as known consist of a filament of carbon which is
rendered incandescent in vacuo by the passage of the electric current, but were the
current sent thro' in air the filament would be immediately consumed.
According to my present invention I prevent this combustion in air, by coating
that part of the filament of carbon which is to be rendered incandescent with such
suitable incombustible & coherent material or materials mentioned further on, which
shall not be liable to fuse at the temperature of the incandescent carbon or other
suitable filament. On passing the current thro' carbon part of the filament, it will
be rendered incandescent and will impart heat to the coherent coating which will
be then also incandescent & give out light in the same manner as the usual carbon
filament, but as the coating is incombustible the filament is not consumed.
A containing vessel of glass not completely closed can when deemed desirable, be
placed round the light.
The ends of the filament of carbon which are not required to be incandescent
are made much larger and thicker (so as to be efficiently connected with the hollow
metallic terminals) either by coating the uncovered ends with deposited carbon, or
affixing suitable carbonaceous materials. The incombustible coating may extend
over the upper part of the enlarged carbon filament while the lower part can be
fixed & in contact with hollow metallic terminals widest at the top, and after
fixing, the space to be filled in on top with suitable non-conducting material to a
little above the commencement of the incombustible coating of the filament.
The lower ends of the terminals can be fixed in as plugs into a connection plate
ог "shoe " from which the current can be turned on or off.
The incombustible coating can be made from mixtures of the oxides of the metals
of the earths and alkalinė earths & gypsum with silica and silicates in such suitable
proportions that will secure as far as possible a coating that will expand and contract
equally with the internal carbon filament. The coating could also be made with
amorphous silicon which has been raised to a white heat in the absence of oxygen
& of other materials, but these last are far more expensive than the first named.
Dated this 12th day of January 1892.
GODFREY BAMBERG.
COMPLETE SPECIFICATION.
Improvements in Electric Incandescent Lamps.
I GODFREY BAMBERG Chemist 17 Western Road Southend Essex 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:-
My invention relates to an improved manufacture of the filaments used in electric
incandescent lamps in such manner that they can be rendered incandescent by the

page_text: electric current without the necessity of their being in a vacuum, and which
filaments when so manufactured shall not be consumed in the presence of air;
together with the method of.connecting the improve, filament with the electrodes.
The incandescent lamps as known and in general, use consist of a filament of
carbon which is contained in an hermetically closed vessel of glass from which the
air has been completely exhausted, and connection with the carbon filament is made
with the electrodes by platinum wires running through the glass.
On the current passing through after leaving the platinum, it, meets with resistance
in the carbon filament which then becomes incandescent, but were any, air or oxygen
present the filament of carbon would be instantly consumed.
It has been proposed to coat the carbon filament with glass or silicic acid or similar
vitreous material but this would be a physical impossibility in the case of such
a fine carbon filament, and even if any practical method could be found for coating
a fine filament of carbon with intensely heated glass without immediately consuming
the filament, it could not be used for incandescence without a vacuum, because the
glass being fusible, it would flow away from the carbon, and therefore the carbon
would be left exposed and be consumed.
Unsuccessful attempts have been made to cover the filament with lime or similar
infusible & incombustible material, but no method has hitherto been found of
making such coating sufficiently adherent and coherent, during and after
incandescence so as permanently to protect the interior filament.
My present invention consists of a novel method of coating that part of 'the
filament of carbon or other suitable material, which is to be rendered incandescent
with such suitable incombustible and coherent material or materials, which shall not
be liable to be fused at the temperature of the incandescent filament, and the coating,
so applied, will be permanently adherent and coherent, during and after.incandescence,
and will therefore completely protect the internal filament from combustion.
On passing the current through the filament it will be rendered incandescent and
will impart the heat and incandescence to the adherent coating which will' therefore
give out light in the same manner as the usual carbon filament, but as the coating
only is in contact with the air and is incombustible and practically infusible it
effectually protects the filament from combustion.
A containing vessel of glass may be placed round the filament 'when 'deemed
desirable but this must not be completely closed, since there must be egress for the
air when expanded.
Those parts of the filament which are not required to be incandescent viz. the
terminals, I make much larger & thicker than hitherto usual, and the coating only
extends over part of the thickened terminals. The uncoated part of the terminals
1, either fix in as plugs into a connexion plate or "shoe "from which the current
can be switched on or off, or I coat or affix metal to the terminals, which can then
be connected direct with the electrodes, and the connections not having to pass
through glass, I am enabled to avoid the necessity of using platinum.
One very good way of carrying out my invention is as follows:-
The carbons or suitable 'filaments which I use may be of slightly increased
diameter and after heating them moderately, I-dip them into a concentrated solution
of an 'alkaline silicate without entirely immersing the terminals, and then I allow
them to dry when there will be a thin film of the silicate over that part of the
filament which is to be rendered incandescent. Finely powdered caustic lime
with or without (but by preference with) the addition of small quantities of other
oxides of the metals of the earths and alkaline earths such as alumina, magnesia
&c. is placed.compactly so as to be in close contact with that part of the filament
which has been prepared as above and.completely covering it from air, leaving part
of the terminals exposed. The current can then be switched on through the terminals.
The filament then becomes white hot, the film of silicate fuses and incorporates
with itself so much of the surrounding infusible materials as to render the whole of
the adhering material practically infusible at the usual temperature of the filament
It is necessary that the current be turned on as gradually as possible, and also
17t

page_text: switched off as slowly as possible so as to allow sufficient time for the entire filament
to be thoroughly cool before withdrawing it from the powdered material. This
process may repeated when required to obtain any desired thickness of coating. It
is better to obtain a coating made up of successive thin coats as this greatly tends
to its durability. In order to secure a coating of good coherence it is necessary to
slightly vary the proportions of the powder according to the nature of the filament
used but the main portion of the powder consists of caustic lime or magnesia.
Triconia would be better but the cost of this material is against its use. The
coating can also be made from amorphous silicium or silicon (the metalloid of which
silicic acid is the oxide) which has been raised previously to a white heat in the
absence of air; which amorphous silicium then acquires the property of not burning
in air or even in oxygen at a white heat. It may be used with or without the
addition of the aforesaid materials but is more expensive.
As it also becomes a conductor of electricity it might be used for the entire
filament were it not so difficult to make it into a fine filament of sufficient strength.
The thickening of the carbon filament to form the terminals referred to above
can be effected either by depositing carbon or affixing suitable carbonaceous
materials. The extremities of the terminals not being coated, they are connected
direct with the electrodes which may be of copper, platinum only being required
in the vacuum lamp, since the connecting electrodes have to pass in that case
through glass, and platinum is the only metal that expands at about the same ratio
as glass.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
(1.) Directly connecting with electrodes by thickening the terminals of the
filament.
(2.) The method of affixing, to a filament for use in an incandescent lamp not
hermetically closed, a coating protecting from combustion, by first applying a film
of an alkaline silicate nearly to the extremities of the terminals and then enclosing
the so prepared part of the filament in a compacted powder formed from the oxides
of the metals of the earths and alkaline earths, or of prepared amorphous silicium
(or together with the oxides) producing slight partial fusion by passing the current
through either in one or in successive operations substantially as described herein
and for the purpose set forth.
Dated this 11th day of November 1892.
GODFREY BAMBERG.