Year: 1886

page_text: Date of Application, 7th May, 1886.
Complete Left, 28th Dec., 1886.
Complete Accepted, 4th Mar., 1887.
I, HERBERT JOHN HADDAN, of 67 Strand, in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention, to be as follows:-
The process of preparing the carbon threads is as follows :-
Wood, silk, cotton or other vegetable fibre is impregnated with a solution of mineral
gum consisting of a mixture of a silicate, senegal gum and caustic soda; subsequently
it is rolled and pressed between heated grooved rollers so that it has an angle iron
or shape, which combines the advantages of great resistance and of the production
of a multi-angular body of only a small cross section. As shown by experience, the
sharp edges of the carbon thread radiate a much stronger light, than the surfaces and
therefore the L shape is advantageous for greater lighting power. This operation being
finished the carbon thread is carbonized in the usual manner after one of the many
known methods.
After this operation the carbon thread is placed in a suitable receptacle, the cover of
which, consisting of insulating material is provided with metallic terminals each of
which has two fastening screws one above and one below the cover the lower for
holding the carbon threads and the upper the conducting wires from a battery or other
source of electricity.
After having fixed the carbon thread which is to be tested with regard to its
resistance, into the terminals (several threads may be fastened at the same time
according to the size of the receptacle) the receptacle is so far filled with melted
paraffine through a suitable opening or funnel in the cover that the carbon threads are

page_text: entirely submerged. The paraffine is then made to cool and solidify and then the
terminals are connected with the electric current into which is simultaneously inserted
a galvanometer or other electric resistance measuring apparatus in order to show the
resistance at any time.
The electric current thus flowing through the carbon thread heats the latter, the
paraffine round the same becomes liquid and the most contiguous parts become even
gaseous and owing to the heating by the electric current particles of carbon are
deposited on the carbon threads, whereby the resistance of the latter is successively
lessened. The parts of the paraffine more distant from the carbon threads remain solid
and form as mentioned above the surrounding for the part of the paraffine becoming
liquid which is as small in amount as is possible with the heat. Thus the current or
flow of the particle of the fluid produced by the increase of temperature is reduced to
a minimum.
After the carbon threads have been brought to the right resistance the electric
current is cut off and the carbon threads after the paraffine has been made perfectly
liquid by heating, can be taken out and subsequently freed from adhering particles of
paraffine by suitable means and are then ready to be introduced into the lamp.
Therefore it is to be considered that the regulation of the resistance of the carbon
thread takes place in a solid bath, which melts only for the minimum part during the
preparation, which operation has the advantage of preventing as far as possible the
admission of air, beside paraffine and napthaline, as in general all easily solidifying
hydrocarbons afford the advantage of most easily depositing their carbon.
It is already known, that this compensation of the differences of resistance is attained
in baths of carbonic gases or liquids; these baths however have the drawback, that by
the deposition of the particles of carbon on the carbon threads, a continuous flow is
produced in the baths owing to the raising of the temperature, so that simultaneously
as the baths always contain particles of oxygen, the whole oxygen contained in the
bath acts on the carbon threads and impairs the quality of the same.
Finally the advantage is to be shown, which is contained in the method of preparation
with a mineral gum. This mineral gum, the composition of which is described above
affords through the application of the senegal gum, a perfect filling out of the pores of
the carbon thread and consequently after carbonizing a great toughness and resisting
power, while the silicate and caustic soda perfectly surrounds the carbon thread which
is finally brought to a uniform and dense structure by the operation of warm rolling.
Therefore the carbon thread when finished will consist of three layers namely the
inner carbon layer, the surrounding silicate layer and the outer so called regulating
carbon layer deposited from the bath.

page_text: COMPLETE SPECIFICATION.
Improvements in the Preparation of Carbon Filaments for Electric
Lamps.
I, HERBERT JOHN HADDAN of 67, Strand in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention, a communication to me
from abroad by Carl Seel of Charlottenburg in the German Empire, Manufacturer
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 improvements in electric incandescent lamps and the
characteristic peculiarity of it is that the incandescent threads are formed of three
annular layers, of which the innermost is the real charcoal thread, which is saturated
with minerals salts and a gum and thus provided with a non conducting silicate or
coating of salt that melts during the carbonization.
This coating protects not only the charcoal thread from burning during the
carbonization and shuts off the air from it, but it also gives the charcoal thread a
smooth upper surface, on which the third layer which is necessary for the adjusting of
the thread in respect to resistance, is deposited in a finely divided and uniform
manner. This third layer is composed of carbon, which is precipitated in a certain
manner; a parafine bath is used for the purpose as will be seen hereinafter.
It has been customary hitherto not to give the charcoal threads the proper resistance
before inserting them in the lamps, but in the present invention the charcoal threads
are ready prepared before being connected and inserted into the lamps; they are
besides tested as to their resistance, and any differences formed in the current resistance
equalized. The new way of equalizing these differences in resistance forms the purpose
of the present improvements.
It is already known that the equalization of these differences in resistance is effected by
baths of carbonaceous gases or fluids. But in these baths there is one great drawback,
namely that, when in consequence of a rise of temperature, the particles of carbon are
deposited on the charcoal threads, and as there are always particles of oxygen in these
baths, the whole oxygeneous contents of them gradually operate on the charcoal threads
and deteriorate their quality. The solid bath which is used in this case and considered
new, removes the evil entirely, for when the charcoal threads are steeped in such a
solid bath for the purpose of preparing them, only those parts that are nearest to the
threads become liquid or vapourous, and from these parts of the bath alone, which are
limited as much as possible, does a depositing of carbonaceous particles on the charcoal
threads take place. All currents in the bath are thus prevented, for only those parts of the

page_text: bath that are nearest to the charcoal threads become fluid or vapourous, whereas the
more distant and unchanged parts of the bath form in a certain measure a closely
encircling vessel or basin. Parafine or naphtaline are used for solid baths and as they
are carburets of hydrogen, hardening at the usual temperature and free of oxygen, a
solid bath is divided during the operation into two zones, into a solid and into a liquid
or vapourous envelop that closely encircles the charcoal threads, the resistance of which
has to be equalized.
The method of preparing the threads is as follows:
Wood, silk, cotton or any other vegetable fibre is steeped into a solution of mineral
salts and a gum consisting of a mixture of a silicate gun senegal and caustic soda,
and then rolled firmly between warmed grooved rollers; it is rolled besides in the
shape of angle-iron and thus combines the advantage of great resistance with that
of being a many edged material of small diameter.
The sharp edges of a charcoal thread can shed as experience teaches a much brighter,
and whiter light than the surfaces do, and therefore the angle-iron shape is the most
advantageous for illuminating. When the operation is finished the thread is carbonized
in the usual way after any of the well known methods.
After this operation the charcoal thread is placed in a vessel a, a cross-section of
which is represented in figs. 1, 2. The cover of this vessel is made of an insulating
material and is provided, as may be seen in the drawing, with metal insertion pieces m
each two of which have two fastening screws ss for securing both the charcoal
threads and the conducting wires of an electric source.
After having inserted the charcoal thread k, which has to be tested as regards
resistance, in the insertion pieces (as drawing shows, several threads can be stretched
in at the same time according as the size of the vessel permits), the vessel is filled
through the hole o either with melted parafine or naphtaline so full that the charcoal
threads are completely immersed. The parafine is then allowed to cool and stiffen,
and the wires are connected with the electric current and a resistance-meter is
fixed in, so that the resistance can be read off at any time.
The electric current that passes through the charcoal thread in this way heats it and the
parts of the parafine close to it become liquid and those closest to it even vapourous, and
then in consequence of the heating particles of carbon are deposited on the thread and
owing to this, the resistance of the latter decreases gradually. The parts of the
parafine farthest removed from the charcoal threads remain solid and form as already
mentioned, an envelop for those parts of the parafine, that have become liquid, and
limit the liquefying of the material as much as possible. The current of the liquid,
caused by the rise of temperature is thus restricted to a minimum.
When the charcoal thread has been raised to the right degree of resistance the
electric current is cut off and the thread is ready for use. When the parafine has been
made perfectly liquid by heating it, the charcoal thread can be taken out. It is cleaned
by some suitable means from the parafine particles attached to it, for instance by means
of benzine, and is then ready to be inserted into the lamp.
It must therefore be observed that the actual regulating of the resistance of the coal
thread takes place in the bath only the smallest part of which melts. This operation
admits only the least amount of air being conducted and in addition to this parafine
and naphtaline as well as other carburets of hydrogen that solidify easily, offer the
advantage of discharging carbon most easily.
The advantage which arises from the method of preparing the thread with silicate,
caustic soda and a gum is still to be explained. The composition of this gum has
already been mentioned; owing to the employment of gum senegal it completely
fills up the pores of the thread and makes the latter exceedingly tough and gives it
greatest power of resistance. The silicate and the caustic soda on the other hand,
encompass the thread entirely and when the latter is subjected to the rolling process
they encircle it closely and uniformly on all sides.

page_text: After being carbonized and prepared the thread will therefore consist of three layers,
namely the inner carbon layer, the annular silicate layer, and the uppermost,
precipitated, so-called regulating layer, formed by the precipitation.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I declare that what I claim is :
1). In an electric incandescent lamp a carbon thread characterized by an inner
layer of carbon in the shape of angle-iron, a second layer of silicate and a third
regulating layer of carbon, obtained by electric precipitation in a parafine bath
substantially as described.
2). The employment of a solid bath consisting of parafine or naphtaline, or similar
hydro carbon substantially as described.