IMPROVE- MENTS IN ELECTRIC LAMPS WITH INCANDESCENT CONDUCTORS AND
Year: 1882

page_text: LETTERS PATENT to William Elliott Debenham of Massingham House
Haverstock Hill in the County of Middlesex for an Invention of
CE
IMPROVE-
MENTS IN ELECTRIC LAMPS WITH INCANDESCENT CONDUCTORS AND IN THE
PROVISIONAL SPECIFICATION left by the said William Elliott Debenham
at the Office of the Commissioners of Patents on the 26th June 1882.
WILLIAM ELLIOTT DEBENHAM of Massingham House Haverstock Hill in the
County of Middlesex "IMPROVEMENTS IN ELECTRIC LAMPS WITH INCANDESCENT
CONDUCTORS AND IN THE MANUFACTURE OF THE SAME"
This Invention of improvements in electric lamps and in the manufacture of
the same relates to those lamps used with an incandescent conductor and its
objects relate first to providing against effects of different rates of expansion in the
platinum or other conducting wire and in the glass surrounding it, and secondly
to modifying the ill effects of the heating of the conducting wire and consequent
unequal heating of the neck of the glass globe.
Thirdly to the material and method of forming the carbon conductor or filament
especially at or round the point or line of metallic contact and to the making good
electrical connection between the carbon and the metallic conductors
Fourthly to the junction of the glass globe whereby it is connected electrically
with the permanent and fixed conductors from the generator.
In the first part of my Invention to obviate the unequal expansion of the
platinum and the glass enclosing it, I surround the platinum with glass of identi-
cally the same coefficient of expansion which I specially manufacture directly fro
that object or mix two or more glasses of different coefficients of expansion to form
when mixed together, a glass which shall have the exact coefficient of expansion
with the platinum or other metal employed.
In various kinds of glass the coefficient of expansion is greater in some and
less in others than for platinum, a careful selection of two kinds therefore mixed
together, or the exact mixture of the materials enployed will give with like

page_text: treatment uniform results and a glass of exactly the same coefficient as the metal
to be employed.
As to the second improvement the conducting wire in these incandescent lamps
becoming heated and passing through the glass surrounding it unequally heats
the glass that is from the part in contact with it and outwards I obviate this
source of danger by arranging that the metallic conductor just inside the glass
shall take the form of discs or half discs or extended surfaces of metal so that the
glass surrounding the place where the wires pass through shall be warmed in a
larger area and not exclusively at the places where the wires pass through This
reduces the heat of the conducting wire and makes the heating of the glass less
local
In order to still further graduate the heating of the glass round the wires I
prefer that the discs or surfaces of metal inside the lamp which serve to warm the
glass and as conductors of the current shall be in actual contact with the glass
immediately surrounding the wire or wires and gradually recede from the glass to
the point where the current enters or quits them from the heated incandescent
portion of the lamp so that the glass is heated round the wire by contact and a
little further off by radiation
In the third part of my Invention the carbon I employ is made from a thread
of sewing cotton or fibre or shred of suitable material which I imbue and cover
with a paste or coating substance of starch guin resin or other material capable of
being carbonised by heat or similar materials cither dissolved in water or spirit
or suitable solvents or made into a paste
The part of the material which is to form the carbon and is in contact with
the metallic conductor receives with the said conductor several coats of the paste
or coating substance.
When partly dried the whole is rolled with moderate
pressure After drying the whole is raised in temperature while covered in a
mixture of sand and charcoal, or with the atmosphere otherwise excluded,
sufficiently to carbonise the organic matter. If necessary a fresh coating of paste
or coating substance is used over the contacts and the whole reheated or carbonised
Gr I previously carbonise the thread or other substitute and the ncover the junction
with the paste or coating substance and then carbonise.
Fourthly--The stem of the lamp is adapted to its fitting by a double metal
bayonet joint the metallic conductors to the carbon being so arranged that the
forcing of the joint home brings them into firm pressed contact with parts of the
fitting that are of metal and in connection with the generator

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by.the said William Elliott Debenham in the Great Seul Patent Office on the
26th December 1882.
WILLIAM ELLIOTT DEBENHAM of Massingham House Haverstock Hill London
IMPROVEMENTS IN ELECTRIC LAMPS WITH INCANDESCENT CONDUCTORS AND IN THE
MANUFACTURE OF THE SAME
To obviate the evils caused by unequal expansion by heat of the glass of which
the globe of an incandescent lamp is made, and of the wires which pass through
this glass I specially prepare the glass or at least that for the portion of the globe
through which the wires pass, in the following manner. I select samples of two
makes of glass one of which has its coefficiency of expansion higher than that of
the conducting wire-platinum generally-and the other of which samples has, as is
generally the case, its coefficiency of expansion lower than that of the inetal. I
measure the coefficiency of expansion of these samples, and mix them in the
proportion indicated by such measurements; so that the mixture shall have its
coefficiency of expansion as nearly as possible identical with that of the wire which
is to pass through In order further to prevent the ill effect of heated conductors
passing through the glass, I make these conductors where they are just inside the
glass, in the form of discs or semi-discs with the straight edges nearly in contact,
or extended surfaces which lie in contact with the glass surrounding the places
where the wires pass through. The continuation of the conductors to the incan-
descent filament is from the gradually turned up margins of these discs or
semi-dises so that these latter form part of the conductors of heat and electricity.
By this means the conductors part with a great deal of their heat to the glass
surrounding the wires, and the glass being thus warmed round the insertion of the
wires, these wires and the glass at the place of insertion are as nearly as possible
of the same temperature
The carbon I employ is made from a thread of sewing cotton or thread or other
suitable organic material which I specially prepare by soaking in a solution of
gluten dissolved in alcohol, of that dilution well known as most favourable for its
solution This soaking is repeated if necessary until sufficient gluten is deposited.
I may also use an ordinary carbon but in either case I cover the joint of the
carbon or material to be carbonised and the metallic conductor, with carbonaceous
paste, flour paste conveniently, and fill the joint with the same When dry I
cover with more paste until the joint appears homogeneous, and then apply the
above mentioned gluten solution several times until I deem the carbonaceous
material compacted at the joint I then carbonise the joint by heat, and if any
imperfection appears, treat as before and recarbonise. A special advantago of an
alcoholic solution such as that of gluten, is that such solution penetrates more
closely than a merely aqueous one.
A solution of gelatine made highly alcoholic
may be substituted for that of gluten.
On the stem of the lamp I blow two projections or studs, which fit into grooves
in the socket, after the fashion of a bayonet joint. The conducting wires from the
inside are left projecting outwards for a short distance, and coine into contact
with metallic plates or surfaces in the socket, which are in connection with the
generator These plates are either springs or are backed up by a spring or springs,
or elastic packing, so that pressure is secured which at the same time makes good
contact and holds the lamp firmly in its place. This pressure should be strong
enough when the lamp is turned round, to lay the projecting wires flat, and give
greater contact surface This general arrangement may be varied by welding the

page_text: studs or projections on to the glass, or by having these studs on a ring fitted to
the lamp after it is blown, or each stud may be metallic and in connection with
one of the conductors from the lamp, or the spring or springs causing pressed
contact may act by pressing the studs downwards so as to bring the wires into
good connection with the plates at the bottom of the socket, or the wires may be
led out at the side of the stem, and bear against connections in the side of the
socket and the pressure may then be obtained by gradual tightening as the lamp
is turned in the bayonet joint or catch
The points which I claim as novel in the construction of the lamp are, First
The manufacture of an incandescent lamp with glass the equality of expansion of
which with that of the metal passing through it, has been secured by the method
described
Second. The extension in contact with the glass internally, of the metallic
conductor immediately round the insertion of the wires, so that the glass and wires
shall be where the insertion exists, as nearly as possible of equal temperature.
Third the use of alcoholic solution of gluten for compacting so far as may be
desirable the fibre which is to form the carbon
Fourth the making of a perfect contact between the metallic conductor and
the carbon by means of a carbonaceous paste consolidated by the infiltration of
alcoholic solution of gluten and afterwards carbonised
Fifth the manner of making simultaneous electrical connection and mechanical
fixture of the lamp in its socket substantially as described
In witness whereof I the said William Elliott Debenhain have hereunto
set my hand and seal this twenty sixth day of December in the year of
our Lord one thousand eight hundred and eighty two
Witness
R LUCAS.
WE. DEBENHAM (L.S.)