IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS
Year: 1883

page_text: LETTERS PATENT to Tom Ernest Gatehouse, of Camberwell, in the County
of Surrey, and Henry Alabaster of South Croydon, in the County of Surrey,
both Electricians for an Invention of IMPROVEMENTS IN INCANDESCENT
ELECTRIC LAMPS
PROVISIONAL SPECIFICATION left by the said Tom Ernest Gatehouse and
Henry Alabaster at the Office of the Commissioners of Patents on the
11th January 1883.
TOM ERNEST GATEHOUSE, of Camberwell, in the County of Surrey, and HENRY
ALABASTER, of South Croydon, in the County of Surrey, both Electricians
IMPROVEMENTS IN INCANDESCENT ELECTRIC LAMPS."
"
Our invention relates to electric lamps depending for their light upon the
incandescence of a carbon filament, and is designed to simplify the attachment
of the said filaments in the surrounding vacuum globes.
The carbon filaments are usually fixed to the leading-in wires-which are
generally platinum-by an attachment effecting electrical contact by mechanical
pressure, aided by cement, and they are a source of weakness, trouble, and
detriment to the successful working of such a lamp, by reason of imperfect
attachment
Our invention consists in the construction of the carbon filaments for use in
incandescent electric lamps, with metallic terminal leads without mechanical joint
carried out conveniently in the following manner.
Wo take a prepared carbon filament, of any desired length, and, preferably, with
ends slightly thicker than the body of the material; and on the ends, as high up
as may be necessary, we cause copper to be electrolytically deposited to any desired
thickness.
On this coating of pure copper we may cause to be deposited, electrolytically or
by other means, a layer of other metal by preference platinum
Or we may pick out part of the carbon filament from the copper sheath produced

page_text: as described, and into the hole so formed we may introduce and fix by soldering
or otherwise a platinum wire to form the leading-in wires, hereafter to be fused
into the glass.
The filament, thus prepared has its metallic ends sealed, in any convenient
method, into the neck of a globe, so that the ends project through the said neck.
The vacuum may then be formed by well known methods.
We thus produce an incandescent electric lamp, with a continuous conductor,
without joint, from terminal to terminal outside the globe, and the difficulties
which have hitherto existed in making a satisfactory joint, between the filament
and the metallic terminal leads of such lamps, are hereby overcome.
If that form of filament with compound sheath of copper and platinum be used,
that part of the carbon filament, which is external to the globe, may be picked
out of its metallic sheathing, and the cavity may be filled with a material that
will close the hollow sheath hermetically. Or the ends of the compound sheath
may be sealed electrolytically. Or leading wires may be fastened, by soldering or
otherwise, into the hollow sheathing, care being taken that the external joint be
secure and air-tight
If the leading-in platinum wires be attached to the copper sheath as before
described inside the globe, the ends may be turned up into a hook outside the
globe as is usual.
The ends of the carbon filament, which are sheathed with both metals as
aforesaid, may, prior to that operation have their pores closed with any suitable
kind of material or "filler" to still further guard against any possible percolation
of air, when the compound sheath is fused in the glass
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Tom Ernest Gatehouse and Henry Alabaster in the Great Seal
Patent Office on the 11th July 1883.
TOM ERNEST GATEHOUSE, of Camberwell, in the County of Surrey, and
HENRY ALABASTER, of South Croydon, in the County of Surrey, both Electricians,
"IMPROVEMENTS IN [INCANDESCENT] ELECTRIC LAMPS
"
Our invention relates to electric lamps depending for their light upon the
incandescence of a carbon filament, and is designed to simplify the attachment of
the said filaments in the surrounding vacuum globe.
The carbon filaments are usually fixed to the leading-in wires-which are
generally platinum-by an attachment effecting indifferent electrical contact by
mechanical pressure, aided by cement, (hereinafter termed "a mechanical joint ").
and they are generally a source of weakness, trouble, and a detriment to the
successful working of such a lamp, by reason of imperfect attachment.
Our invention consists in the construction of the carbon filaments for use in
incandescent electric lamps with metallic terminal leads, without. Inechapical

page_text: Joint from outside terminal to other outside terminal, and s Carried
follows.
In order that our invention may be the more. clearly understood we now
proceed to describe the same with reference to the drawings hereunto annexed
and to the letters and figures marked thereon.
Like letters refer to similar parts in the different figures.
Figure 1 is the carbon filament.
Figure 2 is the filament with its ends metallically sheathed. "
Figure 3 is the filament fixed in position in a vacuum globe.
Figure 4 is a plan of the same.
Figuros 5 and 6, 7 and 8, are alternative methods of sheathing the ends of the
filaments.
We take a prepared carbon filament A of any desired length (Figure 1) and
preferably with ends p slightly thicker than the body of the material; and on the
ends, as high up as may be necessary, we cause copper B to be electrolytically.
deposited to any desired thickness as in Figure 2. On this coating of pure copper
we may cause to be deposited electrolytically, or by other means, a layer of other
metal or material, preferably platinum, to admit of the sheathed ends being
conveniently fused or blown into the glass of the vacuum globe.
Figures 3 and 4 show, in elevation and plan, the filament A, with its terminals B
so sheathed, fused or blown into the neck of the usual vacuum globe C, in which
the vacuum is formed by well known methods.
That part of the carbon filament D, which is external to the globe, may be
picked out of its compound metallic sheathing, and the cavity may be filled with
à suitable cement or material that will close the hollow sheath hermetically. Or
the ends of the compound sheath may be sealed electrolytically. The circuit wires
or leads may be then attached in any convenient manner to the ends of the metallic
sheaths.
To still further guard against any possible percolation of air into the globe when
the sheathed ends of the filament are fused or otherwise secured in the glass, the
ends of the carbon filament may have their pores closed with any suitable kind of
material or "filler" before being sheathed with metal.
Alternatively the ends of wires E, Figure 3, may be fastened, by soldering or
otherwise, into the ends of the hollow sheathing from which the carbon filament
has been picked out, care being taken that the external joint be secure and air-
tight. The wires so fixed may terminate in the usual loop or hook.
Alternatively for an inside joint the wires E, Figure 6, so soldered or fixed into
the hollow ends of the metallic sheathing B, (which in this case need be of copper
only) may be composed of platinum or iron, and be fused or otherwise secured in
the glass of the globe C.
We find in practice that to cover the copper sheathed filament with platinum
or other material suitable for fusing or blowing into the glass, it is convenient to
take a tube F, Figure 5, say of drawn platinum where it is desired to use platinum,
into which the copper-sheathed filament can be inserted as an easy fit. The
external end of the platinum or other tube may be then closed hermetically by
soldering or by the electrolytical deposition of copper around it.
The platinum tubes are then blown into the glass C of the globe in the usual
manner, and loops E, Figure 5, may be soldered or secured into the ends of the
projecting copper sheaths.
In place of the above described tubes of platinum, we may use any other suitable
material, such as iron or tubes of glass. In this latter case one end of the glass
tube may be prepared by an electrolytical deposition of copper, so that the copper
sheathed end of the filament and the wire may be hermetically secured therein by
solder. Or alternatively the coppered terminals may be secured in the glass tube
by an air-tight cement or plaster. Or the glass tube G, Figure 7, may have a
short thin platinum tube H fixed in it by the glass being melted on it by the blow
pipe. The end of the copper covered filament A and conveniently another wire K,

page_text: of platinum or copper, are inserted into the tube so as to be in contact. Solder is
then run in, so as to solder the coppered filament to the wire K, and also that wire
to the platinum collar or tube. The joint is thus metallically closed, and hermeti-
cally sealed, and glass tubes may be blown in the neck L (Figure 8) of the vacuum
globe in the usual manner.
In the form of joint shown at Figure 8, the coppered filament A may be brought
right through the glass tube, so as to dispense with the wire K, and may be bent
into a loop, or have attached to it in any convenient way the usual leading-in
wires.
This joint may if desired be entirely within the globe, and in such case the
wire K must be used, and be preferably of platinum, so that it can be conveniently
blown into the glass neck of the globe.
Having now described and ascertained the nature of our said invention and the
method of carrying the same into effect be it known that what we consider novel
and desire to protect by Letters Patent is :-
=
First. In incandescent electric lamps, the construction of continuous conducting
filaments without mechanical joint, from one outside terminal to the other outside
terminal, substantially as described.
Second. The method of preparation of filaments for incandescent electric lamps,
by covering their terminals with a metallic sheath of platinum or other suitable
metal upon copper by electrolytical doposition, or the outer sheath as a tube,
substantially as described.
Third. The alternative method of preparation of filaments for incandescent
electric lamps with an external tube of glass over an under copper sheath upon
the terminals, substantially as described.
Fourth. The method of preparation of filaments for incandescent electric lamps
with an external glass tube with platinum collar soldered upon the coppered
filament and leading in wire, substantially as described.
In witness whereof I, the said Tom Ernest Gatehouse, on behalf of myself
and the said Henry Alabaster, have hereunto set my hand and seal this Eleventh
day of July in the year of our Lord One thousand eight hundred and eighty-
three
Witnes
JOHN. C. FELL
TUM ERNEST GATEHOUSE (L.S.)
Fell & Wilding
23 Rood Lane, London. E.C.
Patent Agents.