IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS
Year: 1882

page_text: LETTERS PATENT to Tom Ernest Gatehouse of Camberwell in the County of
Surrey, Electrician for an invention of IMPROVEMENTS IN INCANDESCENT
ELECTRIC LAMPS
PROVISIONAL SPECIFICATION left by the said Tom Ernest Gatehouse at
the Office of the Commissioners of Patents on the 23rd March 1882
TOM ERNEST GATEHOUSE of Camberwell in the County of Surrey Electrician,
"IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS."
My Invention relates to electric lamps deriving their luminosity from the
incandescing of a conductor in vacuo, and is designed to effect the objects claimed
by me in my Specification filed in pursuance of my Letters Patent numbered 3240,
and dated 25 July 1881, Claim I, in a similar but more simple manner, that is to
say, the preservation of the incandescent conductor by means of the opposite
physical properties of carbon and inetals.
Whereas in my said Specification, in my compound conductor, platinum wire is
used as an incandescent light giving material in conjunction with carbon, in parallel
or alternative circuits, having their sections and lengths, and therefore their normal
resistances, properly proportioned; I now propose to use an alternative method to
obtain a like result.
My present device consists of an incandescing conductor, formed in continuous
circuit, of two materials of opposito electrical resistances with regard to temperature,
conveniently platinum and carbon. In this case the resistance of the platinum
increases with a rise of temperature, whilst that of the carbon decreases. The
sectional areas and lengths of the separate constituents are so proportioned
(according to their respective properties) as to form a continuous conductor of more
or less constant resistance, and, in which, at times, both the constituents of the
conductor would become luminous, irrespective of the leading wires fused in the
globe.
The arrangement conveniently adopted is to attach short lengths of platinum on
both leading wires, bridged by a carbon loop, the whole being enclosed in an
exhausted globe.
I may insert my device in a series or system of my, or other, electric lamps, to
serve as a regulator.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Tom Ernest; Gatehouse in the Great Seal Patent Office on the
20th September 1882
TOM ERNEST GATEHOUSE of Camberwell in the County of Surrey Electrician
'IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS"
In the Specification to Letters Patent granted to me on the 25th July 1881
No 3240 I described an incandescent electric lamp in which two materials such as
platinum and carbon whose electrical resistances vary in opposite directions with
changes of temperature, (the resistance of the platinum increases whilst that of
carbon decreases with elevation of temperature) were employed to form two parallel
or alternative circuits. My present invention consists in arranging two such
materials to form a continuous conductor, the sectional area and length of each
being so proportioned to that of the other, that the conductor as a whole has an
electrical resistance better suited to the conditions of the lamp than when a
single material is used as a conductor, either or both of the constituents of the
conductor being rendered luminous by the passage of the electric current. A con-
convenient arrangement of lamp according to iny invention is to attach to the
conducting wires which are hermetically sealed through the glass of a vacuous
globe or bulb, short lengths of platinum wire connected by a bridge or loop of
carbon filament, so that the current has to pass through both the platinum and
the carbon. The relative lengths and areas of tha platinum and carbon parts of
the conductor may be somewhat varied, but I find that to obtain a good effect each
part of the conductor should have such dimensions that the resistance of the
platinum, at ordinary temperatures should be to that of the carbon in about the
proportion of 3 or 5 to 100.
A compound conductor such as I have described, may be introduced in the
main conductor or conductors for a series of electric lamps so as to operate as a
regulator.
Having thus described the nature of my invention and in what manner the
same is to be performed I hereby declare that I make no general claim to the use
for incandescent lamps of two separate alternative or parallel circuits consisting of
materials whose electrical resistances vary in opposite directions under changes of
temperature, but I claim :-
The use in an incandescent electric lamp of a compound conductor consisting
partly of one material such as platinum whose electric resistance increases with
elevation of temperature and partly of another material such as carbon whose
resistance decreases with elevation of temperature, substantially as and for the
purposes herein set forth
In witness whereof I the said Tom Ernest Gatehouse have hereunto set my
hand and seal this twenty third day of August in the year of our Lord One
thousand eight hundred and eighty-two.
TOM ERNEST GATEHOUSE (LS.)