Year: 1887

page_text: Date of Application, 26th Mar., 1887
Complete Left, 25th Jan., 1888
Complete Accepted, 24th Feb., 1888
I, ALBANY FEATHERSTONHAUGH, of the Junior United Service Club, Charles
Street, London, a lieutenant colonel in the Corps of Royal Engineers, do hereby
declare the nature of this invention to be as follows:-
My invention has for its object to obtain in certain cases at the same cost more
light than can be obtained by the incandescent lamps now in use or again to obtain
in certain cases at less cost an equal amount of light to that obtained by the use of
the present lamps. The saving in cost to which I refer occurs in several ways, viz. :
by the use of a weaker current or of a smaller electromotive force or of both.
Also, if a weaker current suffices, the cost of the conductor will be very much
lessened.
My Invention consists in placing inside the glass globe of an incandescent electric
lamp two or more filaments of any kind, or two or more wires of metal, as the case
may be, close to each other so that the heat from each reinforces that from the other
or others and there is less loss of heat by radiation.
For these reasons more light is produced by each filament or wire by a given
strength of current in each.
In order to get the filaments or wires close to each other and to keep them so I
may twist them round each other or 1 may plait them like the strands of a cord.
I make the system of filaments or wires of any shape that may be desirable and
I arrange them in the glass globe with such modifications in the shape and size of
the latter as may enable me fully to carry out my improvements..
Dated this Twenty fifth day of March 1887.

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Incandescent Lamps.
I, ALBANY FEATHERSTONHAUGH, of the Junior United Service Club, Charles
Street, London, lieutenant colonel in the Corps of Royal Engineers 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 consists in placing inside the glass globe of an incandescent electric
lamp two or more filaments of any kind or two or more wires of metal, as the case
may be, close to each other, so that the heat from each reinforces that from the
others and there is less loss of heat by radiation. For these reasons more light is
produced by each filament or wire by a given strength of current in each.
In order to carry out my invention I take two or more filaments before carboni-
zation and arrange them close together by twisting them round each other in their
whole length or in any part of it or again by pleating them together like the strands of
cord, or in any other simple way. The compound filament so formed is carbonized
in the usual manner and the subsequent steps of placing it in a glass globe and
exhausting the latter so as to form a durable glow lamp are the same as are now used
for an ordinary lamp. The connections to the leads or wires from the source of
electricity are analogous to those now in use. Wires are treated in the same way
and by the term wires I mean metallic wires whether coated or incorporated with
other substances or not. Metallic wires cannot of course be carbonized but in other
respects they should be dealt with as described above.
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:
In all electric incandescent lamps where multiple filaments or wires are used,
arranging these filaments or wires so that they are close together whereby a saving
of heat is effected and there is an increased amount of light produced to what would
otherwise be the case.
Tad thin 94th day of January 1888