IMPROVEMENTS IN THE MANUFAC- TURE OF CERTAIN PARTS OF INCANDESCENT ELECTRIC LAMPS
Year: 1884

page_text: We CHARLES HORACE BENTON and HUBERT HENRY GRUBBE both of Norland
Works Latimer Road, Notting Hill in the County of Middlesex Engineers do
hereby declare the nature of our invention for IMPROVEMENTS IN THE MANUFAC-
TURE OF CERTAIN PARTS OF INCANDESCENT ELECTRIC LAMPS to be as follows:-
Our invention relates first to the manufacture of the carbon filaments or
conductors of incandescent electric lamps; secondly to the. formation of the joint
between the carbon filament and the platinum supports and thirdly to the
formation of the joint between the leading-in conductors and the glass neck of the
lamp flask or bulb.
The improvements consist :-
First In immersing such portion of the length of the fibres as is required for
the filaments in an acid solution so that the outer texture is destroyed and rendered
soft, in then washing the fibres and afterwards drawing them through one or more
dies to reduce them uniformly to the required diameter or thickness the fibres being
subsequently submitted to the usual process of baking or carbonizing and then
receiving a deposit of carbon in the manner well known.
Secondly. In forming a sound electrical joint between the carbon filament and'
each of its platinum supports by means of a strip of very thin foil of platinum or
other suitable metal which is formed into a cylinder or tube so as to receive the
end of the filament and the platinum support.
Thirdly. In forming a tight joint between the glass neck of the bulb or flask and
the leading-in conductors by employing as the leading-in conductor a strip of foil
of platinum or other suitable metal bent into an approximately tubular form or
other form capable of receiving an internal piece or support of glass.
In carrying out the first part of the improvements we employ by preference the
fibre known as Mexican fibre,, but many other vegetable fibres will answer the
purpose as will be well understood. We immerse such portion of the length of the
fibre as is required for the filament in an acid solution, by preference a solution of
sulphuric acid, formed of 2 parts of acid to about one part of water. The effect of
this immersion the duration of which will vary according to the strength of the
solution and to the thickness of the fibre is to destroy a portion of the outer texture
of the fibre and render it soft. We then wash the fibre in water. We next take hold

page_text: of it by those portions of its length which have not been treated in the acid solution
and which are therefore still hard and draw it through a die to uniformly reduce the
portion upon which the acid has acted to the required diameter. If necessary two
or more dies of different gauges may be employed the fibre being passed through
them successively, the smallest die corresponding to the diameter required in the
filament. The filaments thus prepared are then baked or carbonized and subse-
quently have a deposit of carbon formed upon them in the manner well known.
In carrying out the second improvement we take a strip of very thin platinum
foil, say about .0005″ thick, %16" long and 1/8" broad. We heat it in a Bunsen flame
or otherwise in order to render it soft and non elastic, and we then fold one third
of it more or less upon the middle portion so that its length is reduced to 3/8", one
half of this length being double the thickness of the other half. We next bend the
foil around the platinum wire and by pressing together that part of the foil which
overlaps the side of the wire we cause it to fit firmly around it. We then cut off the
superfluous foil and we slide the cylinder thus formed to the end of the wire until
one half projects beyond the end, the portion which is of double thickness remaining
around the wire. We then heat the cylinder of foil and the wire by means of a
Bunsen flame or a blow pipe to cause the foil to shrink tightly upon the wire and
thereby make a perfectly sound electrical contact. But in order to ensure that the
cylinder of foil shall always remain in its position we melt each end of a glass rod
which holds the two platinum wires in position, partly on to the cylinder of foil
and partly on to the platinum wire. Into the projecting portion of the platinum
cylinder we insert a small rod of hard metal of the same diameter as the filament
whose end is to be afterwards inserted. We pinch flat so much of the foil as is in
excess beyond that required to surround the rod tightly; the cylinder of foil is
thus reduced to the diameter of the metal rod. The excess foil is then cut off and
the rod withdrawn. We then run the ends of the filament into the projecting
portions of the cylinders and in order that the platinum support may remain
comparatively cool when the filament is incandescent it will be well to deposit
carbon from a hydro-carbon compound upon a certain length of the filament ext
the foil whereby its resistance is reduced and its radiating surface increased. It is
in order to prevent cooling during the process of depositing carbon as just stated
that we make that portion of the cylinder of foil into which the filament is inserted
of only half the thickness of the remaining portion.
In carrying out the third improvement we take for each of the leading-in
conductors a strip of platinum foil and bend it into a form which will receive an
internal support of glass, the form which we prefer is approximately tubular or of
C section. Into this bent foil or tube we insert or melt a correspondingly shaped
piece of glass to act as an internal support to same and to assist in making the joint
while the ueck is being closed by the ordinary glass blowing process. The outer
ends of the strips of foil should be left unbent or flat so as to be the more easily
connected to the line wires. By forming, the leading-in conductors of foil as above
described a more perfectly tight joint with the glass neck is obtained than when
wires are employed.
.15
Sometimes we make the platinum foil which forms the leading-in Conductor 'as
above described sufficiently long to form the holder for the carbon filament its inner
end being reduced to the necessary diameter in the manner. already explained. In
this modification the separate platinum wires' or 'supports are dispensed with.
•

page_text: We CHARLES HORACE BENTON and HUBERT HENRY GRUBBE, both of Norland
Works, Latimer Road, Notting Hill, in the County of Middlesex, Engineers do
hereby declare the nature of our invention for "IMPROVEMENTS IN THE MANU-
FACTURE OF CERTAIN PARTS OF INCANDESCENT ELECTRIC LAMPS" and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
Our invention relates first to the manufacture of the carbon filaments or con-
ductors of incandescent electric lamps, secondly to the formation of the joint
between the carbon filament and the platinum supports and thirdly to the formation
of the joint between the leading-in conductors and the glass neck of the lamp-flask
or bulb. The improvements consist:-
:-
First, In immersing such portion of the length of the fibres as is required for
the filaments in an acid solution so that the outer texture is destroyed and
rendered soft, in then washing the fibres and afterwards drawing them through
one or more dies to reduce them uniformly to the required diameter or thickness
the fibres being subsequently submitted to the usual process of baking or car-
bonizing, and then receiving a deposit of carbon in the manner well known.
Secondly. In forming a sound electrical joint between the carbon filament and
each of its platinum supports by means of a strip of very thin foil of platinum or
other suitable metal which is formed into a cylinder or tube so as to receive the
end of the filament and the platinum support.
Thirdly. In forming a tight joint between the glass-neck of the bulb or flask
and the leading-in conductor by employing as the leading-in conductor a strip of
foil of platinum or other suitable metal bent into an approximately tubular form
or other form capable of receiving an internal piece or support of glass.
In carrying out the first of the improvements we employ by preference the fibre
known as Mexican fibre but many other vegetable fibres will answer the purpose
as will be well understood. We immerse such portion of the length of the fibre
as is required for the filament in an acid solution, by preference a solution of
sulphuric acid, formed of two parts of acid to about one part of water. The effect
of this immersion, the duration of which will vary according to the strength of
the solution and to the thickness of the fibre, is to destroy a portion of the outer
texture of the fibre and render it soft. We then wash the fibre in water. We
next take hold of it by those portions of its length which have not been treated
in the acid solution and which are therefore still hard and draw it through a die
to uniformly reduce the portion upon which the acid has acted to the required
diameter. If necessary two or more dies of different gauges may be employed
the fibre being passed through them successively, the smallest die corresponding
to the diameter required in the filament. The filaments thus prepared are then
baked or carbonized and subsequently have a deposit of carbon formed upon them
in the manner well known.
In the accompanying drawings Figure 1 is an elevation, partly in section, of
an incandescent electric lamp embodying the second and third improvements;
Figure 2 is an elevation shewing the platinum supports with the carbon filament
connected thereto by means of the joint of platinum foil and shewing also a glass
rod which holds the two platinum supports in position. Figures 3 to 9 are detail
views illustrating the mode of making the said joint between the filament and the
platinum supports. Figure 10 is a section on a larger scale on line 1-1 of

page_text: Figure 1. Figure 11 is a view illustrating a modified form of the invention in
which a strip of platinum foil is employed of sufficient length to form both the
leading-in conductor and the tubular holder for the end of the carbon filament.
In these figures a is the lamp flask or bulb which may be of any desired shape-
bis the neck of same. c is the carbon filament. d, d are the platinum supports.
e is a glass rod for holding said supports in position. f, f¹, f, fi are the platinum
foils which form the joints between the ends of the filament c and the sup-
ports d, d-y, g are the platinum foils which form the leading in conductors. h, h
are rods or pieces of glass which act as supports to the foils g, g and assist in
making the joint in the neck.
Referring first to the joint between each end of the carbon filament and the
corresponding support d, we take a strip of very thin platinum foil-see Figure 3-
say about .0005" thick, " long and "broad. We heat it in a Bunsen flame or
otherwise in order to render it soft and non-elastic, and we then fold one-third of
it, more or less, upon the middle portion-see Figures 4 and 5-so that its length
is reduced to ", one-half f of this length being double the thickness of the other
half f. We next bend the foil around the platinum wire-see Figure 6, and by
pressing together that part of the foil which overlaps the side of the wire we cause
it.to fit firmly around it. We then cut off the superfluous foil, that is to say, the
part marked f in Figure 6, and we slide the cylinder thus formed to the end of
the wire until one-balf f¹ projects beyond the end see Figure 7-the portion f
which is of double thickness, remaining around the wire. We then heat the
cylinder of foil and the wire by means of a Bunsen flame or a blow-pipe to cause
the foil to shrink tightly upon the wire and thereby make a perfectly sound
electrical contact. But in order to ensure that the cylinder of foil shall always
remain in its position we melt each end of a glass rod e (Figure 2) which holds
the two platinum wires in position, partly on to the cylinder of foil and partly on
to the platinum wire. Into the projecting portion f¹ of the platinum cylinder we
insert a small rod of hard metal of the same diameter as the filament whose end is
to be afterwards inserted. We pinch flat so much of the foil-see f³, Figure 8-as
is in excess beyond that required to surround the rod tightly; the cylinder of foil
is thus reduced to the diameter of the metal rod. The excess foil f' is then cut
off-see Figure 9, and the rod withdrawn. We then run the ends of the filament c
into the projecting portions f¹ of the cylinders and in order that the platinum
support may remain comparatively cool when the filament is incandescent it will
be well to deposit carbon from a hydro-carbon compound upon a certain length of
the filament next the foil whereby its resistance is reduced and its radiating surface
increased. It is in order to prevent cooling during the process of depositing carbon
as just stated that we make that portion of the cylinder of foil into which the
filament is inserted of only half the thickness of the remaining portion.
Referring now to the joint between the glass neck b and the leading-in
conductors g, g-we take, for each of these conductors a strip of platinum foil and
bend it into a form which will receive an internal support of glass, the form which
we prefer is that shewn in the drawings, Figures 1 and 10 being approximately
tubular or of C section. Into this bent foil or tube g we insert or mielt a corre-
spondingly shaped piece of glass h to act as an internal support to same and to
assist in making the joint while the neck is being closed by the ordinary glass-
blowing process. The outer ends of the strips of foil g, g should be left unbent or
flat, as seen in Figure 1, so as to be the more easily connected to the line wires.
By forming the leading-in conductors of foil, as above described, a more perfectly
tight joint with the glass neck is obtained than when wires are employed.
Sometimes, as represented in Figure 11, we make the platinum foil g which
forms the leading-in conductor, as above described, sufficiently long to form the
holder for the carbon filament its inner end f¹ being reduced to the necessary
diameter in the manner already explained. In this modification the separate
platinum wires or supports d, d-Figures 1 to 9-are dispensed with.

page_text: Having now particularly described and ascertained the nature of our said
Invention, and in what manner the same is to be performed, we declare that what
we claim is:
1. The manufacture of carbon filaments for incandescent electric lamps by sub-
mitting vegetable fibres to the following processes in succession, that is to say,
immersion in an acid solution, washing, drawing through a die or dies, baking or
carbonizing and depositing thereon of carbon substantially as set forth.
2. The formation of a sound electrical joint between the ends of the carl on
filament of an incandescent electric lamp and the platinum' supports of such filament
by means of strips of very thin metallic foil manipulated into such form as to
receive the ends of the filament and the platinum supports substantially as set
forth and shown.
3. The formation of tight joints between the glass neck of the flask or bulb of
an incandescent electric lamp and the leading-in conductors by employing as said
conductors strips of metallic foil bent into a form which will receive an internal
piece or support then inserting or melting a piece of glass into each conductor and
finally closing the neck by the glass-blowing process, substantially as set forth and
shown.