IMPROVEMENTS IN ELECTRIC LAMPS OPERATING BY INCANDESCENCE
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Frank Wright at the Office of the
Commissioners of Patents on the 8th August 1881.
FRANK WRIGHT, of Burlington Buildings, Regent Street, in the County of
Middlesex, "IMPROVEMENTS IN ELECTRIC LAMPS OPERATING BY INCANDESCENCE."
My Invention relates to the preparation of fibres or filaments suitable for forming
the incandescent bridge of an electric lamp, and to the construction of stoppers for
such lamps with appliances for exhaustion of the lamp and conduction to the fibre
or filament. The fibre which I preparo is selected of suitable size among those which
are employed to make bass brooms. I bind a number of these fibres side by side
over a block of carbon formed to the horseshoe shape which the fibre has to assume
in the lamp, and I secure them thereon by an external carbon mould put on in
halves. I place the mould with the fibres in a weak solution of sulphuric acid and
boil for about two hours. I then remove the fibres from the mould and place them
in a crucible in layers of powdered graphite, or between blocks of graphite covered
on the top by powdered graphite; I heat the crucible and its contents to a white
heat, and maintain them at that heat for about half an hour. When the fibres
have cooled I remove them from the crucible, and I attach each to a pair of
conducting clips fixed in a plug which can slide in the tubular neck of the vessel.
This vessel I partly charge with oil, and the space above the oil I keep supplied
with ordinary coal gas or hydro-carbon vapour. I push down the plug so as to
immerse the fibre in the oil and then withdraw it, so that the fibre is in the gas or
vapour space, in which position I pass through it an electric current sufficient to
render it highly incandescent. I repeat this process until I find the conductibility
of the fibre increased to the degree desired, as indicated by a galvanometor in the
circuit of the fibre. This part of the operation may be arrested automatically by
introducing in the circuit the coil of an electro-magnet, which when the desired
degree of conductibility is attained, attracts its armature in opposition to an
adjusted spring and so brakes contact for the circuit of the fibre. The fibre thus
prepared is introduced into a glass globe, and has its ends attached to the conducting
terminals in any known manner. Those terminals are, according to my Invention,
arranged in the stopper of the glass globe in the following manner:-The one
Price 2.11

page_text: terminal for earth is directly connected to the stopper itself, which is screwed into
a socket of a bracket or chandelier. The other terminal is a wire which passes
through a central hole of the stopper lined with insulating material, and along the
wire is filed a flat or slit to form a small passage for air. Outside the stopper is
the head of a screw which screws into the central terminal, this head having a
packing washer of insulating materal. This screw being a little unscrewed, the
lamp is connected to a pipe leading to the pump employed for exhaustion, and
when the lamp has been sufficiently exhausted the screw of the terminal is screwed
tight home by turning a spindle passing through a stuffing box in the exhaust
pipe, the air passage through the stopper being thus entirely closed, whereupon the
lamp can be removed for use. In exhausting the globes it is of advantage in
the first place to exhaust to a considerable extent by an ordinary air pump,
and thereafter to exhaust more completely by means of a pump sealed with
mercury.