IMPROVEMENTS IN ELECTRIC LAMPS, IN THE MANUFACTURE OF PARTS THEREOF, AND IN APPARATUS FOR EXHAUSTING THEM, THE EXHAUSTING APPARATUS BEING ALSO APPLICABLE TO PURPOSES." OTHER PROAL SP
Year: 1880

page_text: LETTERS PATENT to St. George Lane Fox, of Telegraph Street, in the City of
London, for an Invention of "IMPROVEMENTS IN ELECTRIC LAMPS, IN THE
MANUFACTURE OF PARTS THEREOF, AND IN APPARATUS FOR EXHAUSTING
THEM, THE EXHAUSTING APPARATUS BEING ALSO APPLICABLE TO
PURPOSES."
OTHER
PROVISIONAL SPECIFICATION left by the said St. George Lane Fox at the
Office of the Commissioners of Patents on the 28th August 1880.
"IMPROVE-
ST. GEORGE LANE Fox, of Telegraph Street, in the City of London.
MENTS IN ELECTRIC LAMPS, IN THE MANUFACTURE OF PARTS THEREOF, AND IN
APPARATUS FOR EXHAUSTING THEM, THE EXHAUSTING APPARATUS BEING ALSO
APPLICABLE TO OTHER PURPOSES."
"
My Invention consists of improvements in the construction of electric lamps, in
the manufacture of an improved burner or "luminous bridge
for such lamps,
and in apparatus for exhausting the lamps, which apparatus although specially
designed for the above purpose may also be employed for exhausting other articles.
My improved lamps and luminous bridge or buruer may be used in conjunction
with the system of distribution and regulation of the electric current, as explained
in the Specifications of several former Letters Patent granted to me and dated
respectively 9th October 1878 (3988), 12 October 1878 (No. 4043), and 14th
November 1878 (No. 4626), or otherwise.
In my improved lamp the light results as before from the incandescence of a
continuous conductor, composed of some highly refractory material having a great
electrical resistance, and the extent of the luminous surface is dependent as before
on the intensity and quantity of light required. Between the ends of the luminous
bridge is a small block of porcelain, steatite, or other suitable material, which
keeps them apart, and a pair of metallic clips through which the current passes
press against the outer surface of the said ends, and so form the electrical contact.
The clips may be made with advantage of steel wire passed through and connected
to a block of porcelain, steatite, or other suitable material. Borax fused by means
of a blow pipe makes a good cement for this purpose. The upper ends of the clip
wires have soldered to them short pieces of platinum wire, which enter the lower
ends of and are fused into glass tubes. These glass tubes are filled with mercury,

page_text: and form the electrical communication between the luminous bridge and the
outside of the globe of the lamp. The said glass tubes and another tube which
connects the globe with the apparatus by which the lamp is exhausted pass through
and fit tightly in holes in an india rubber stopper, which closes the neck of the
globe, and the neck is made slightly tapered to prevent the stopper being forced in
by the pressure of the atinosphere. The upper surface of the stopper is covered by
a layer of mercury to make the joint perfectly air tight. Above the mercury some
marine glue may be melted to prevent its being spilt.
I make the luminous bridge or burner of vulcanized fibre, which has been baked
at a white heat. In order to prepare this bridge or burner I cut from a sheet of
the vulcanized fibre (from 20th to 100th of an inch thick, according to the required
resistance of the lamp), a piece or strip approximately of paddle shape, that is to
say, narrow in the middle, and comparatively wide at the ends. The thickness,
width, and length of the strip of vulcanized fibre depend, as already mentioned,
upon the resistance required; any resistance can be easily obtained between
A conductor made from a strip
10 and 200 ohms. (British Association units).
1/2″ thick, 1/10" wide, and 1% long (in the narrow part), will have a resistance of
about 30 ohms. Having cut the strips of the form above described, I bend each so
that while the broad ends are brought parallel to each other and nearly together,
the narrow portion is in the form of a loop or bow. I then arrange several of them
together, so that the broad parts are pressed by means of a spring between plates
of steel or porcelain, the plates separating the two broad parts of each strip being
the same thickness as the small block of porcelain which keeps them apart in the
lamp, as herein before described. The set of strips thus held by means of the spring
I then place in a crucible filled or packed with powdered charcoal or plumbago.
I raise the crucible to a bright red heat, taking care however not to so heat the
spring that it will loose its elasticity; for this purpose the main portion or body of
the spring is kept out of the crucible.
When baked as above described, the strips or luminous bridges are carbonized by
heating them at a white heat in benzole vapor or other suitable carbon compound.
This can be conveniently effected as follows:-The bridge having been mounted in
clips similar to those used in the lamp, as before described, in a vessel containing
only rarefied benzole vapour or carbon compound, an electric current is then passed
through it so as to raise it to a white heat; the heated surface will rapidly assume
a light grayish appearance, while the resistance of the bridge will be rapidly
diminished. This process is continued for about half a minute, or until the bridge
has been reduced to the required resistance. The broad parts are carbonized by
passing a more powerful current through them, and during this operation which is
also conducted in a vessel filled with benzole vapour or carbon compound, the
narrow part or bridge proper is immersed in some conducting medium, such as
mercury. The broad parts must be very well carbonized, so that their resistance
may be made very small. Instead of heating the bridges by the passage of an
electric current, they may be suspended in a porcelain vessel filled with the benzole
vapor or carbon compound, the porcelain vessel being then raised to a white heat
in a furnace.
The vulcanized fibre used for making the bridge should be as free as possible
from mineral substances containing oxygen. In order to remove all traces of
mineral matter, the bridge when finished should be boiled in nitrohydrochloric
acid, and then in hydrofluoric acid.
The lamp constructed as before explained, and having a luminous bridge made as
described mounted therein must then be exhausted. The apparatus 1 employ for
this purpose is arranged as follows:-A vertical glass tube 30 inches high or inore
terminates at its upper end in a bulb, at the upper part of which is a ground neck,
which at certain times receives the ground lower end of a glass rod. This neck
opens into another bulb above through the neck of which the glass rod also passes;
the part of the rod which passes through this neck is covered with india rubber or
other suitable material, so that the rod while capable of being forced up and down

page_text: so as to open and close the neck of the lower bulb shall all the while preserve a
tight joint in the neck of the upper bulb. Above the upper bulb is a cup. To the
lower end of the glass tube I connect one end of a strong flexible tube of greater
length, to the other end of which an open vessel is fitted. It will be of advantago
to interpose an air trap between the said glass tube and the flexible tube. To the
said glass tube just below the lower bulb is connected another vertical tube
30 inches long or more above the level of the cup, the upper end of which is
connected by a bend to a tube hermetically joined to the tube, which communicates
with the interior of the globe of the lamp, passing through the india rubber
stopper, as herein before described. These tubes with their bend constitute the
exhausting tube.
The action of the apparatus is as follows:- _The open vessel having been filled or
partly filled with mercury when in a lowered position, is raised to such a height
that while it becomes nearly empty, the mercury rises in the two bulbs filling the
same up to the cup before described. The neck of the upper bulb is then closed by
the rod, the neck of the lower one being left open. The open vessel is then lowered
until it is about 36 inches below the point where the exhausting tube communicates
with the first described vertical glass tube. The consequent fall of the mercury in
the bulbs produces a vacuum, which will be filled by the air in the lamp forcing its
way through the exhausting tube. The open vessel is then again raised, the neck
of the upper bulb being opened to allow the air to escape. The two bulbs again
become full of mercury, the neck of the upper is again closed, the opened vessel
again lowered, and so on, until the lamp is almost exhausted. The pumping action
is then somewhat modified thus:-The open vessel is raised and lowered several
times while the rod is out, so as to make the mercury rise and fall in the bulbs,
which should now be slightly warmed in order to evaporate any moisture which
may be present on their sides. The mercury must not be allowed to fall below the
point of communication with the exhausting tube while the rod is out, otherwise
the mercury will be forced up the said tube into the lamp. Having got rid in. this
manner of all traces of aqueous or other vapor, the rod is again inserted (while the
open vessel is raised) into the neck of the upper bulb, leaving the neck of the lower
bulb open; the open vessel is then again raised and lowered several times, so that
the mercury rises and falls in the bulbs, and in this way all traces of air from the
surface of the tubes or bulbs will collect in the upper bulb. The open vessel is
then placed at such a height that the mercury fills the lower bulb, and is just above
its neck. The rod is then forced down so as to close this neck, and the open vessel
is lowered until the mercury is below the point of communication with the
exhausting tube, again raised, and so on. The upper bulb above the neck of the
lower has for object to render the vacuum in the lower more perfect.
By using sulphuric acid with the mercury so as to wet the surface of the glass
bulb, and the ground joint at the neck of the lower bulb, the upper bulb may be
dispensed with altogether, but the acid must be very pure.
The lamp having been thoroughly exhausted, a current is passed through it so as
to render the burner or luminous bridge incandescent, the pumping action being
continued as rapidly as possible. The incandescence and pumping are continued
until nothing more comes off, when the exhausting tube is melted near the top of
the lamp, and the lamp thereby sealed from the atmosphere. A small bulb may be
introduced in the exhausting tube just below the bend to prevent mercury running
over the bend.
Although I have described mercury as the liquid used in the exhausting
apparatus, other suitable liquids may be employed, such for example, as sulphuric
acid, but in that case it would be desirable to have means of exhausting what
I have described as the open vessel, to avoid the necessity of having the flexible
tube made very long. In any case, instead of this tube being made flexible, it may
be worked up and down like a piston or telescopically.
When sulpburic acid is used the apparatus may with advantage be modified as
follows: A glass or porcelain vessel has a narrow neck opening into a cup; a

page_text: ground stopper fits into the neck, thus forming a valve which opens outwards.
Instead of the long vertical tube leading to the vessel to be exhausted, which when
sulphuric acid is used would have to be about 20 feet high, I fit a valve in the tube
leading up from the bottom of the glass or porcelain vessel to the vessel to be
exhausted; this valve closes when the liquid reaches it, and opens again when the
liquids falls. Instead of the movable open vessel I employ a closed vessel some-
what below the glass or porcelain vessel, and provided with means by a piston or
otherwise, whereby its internal pressure can be raised or lowered to an extent
somewhat in excess of the atmospheric pressure; the liquid in the glass or porcelain
vessel can thus be forced up and down. The liquid should be as cold as possible.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said St. George Lane Fox in the Great Seal Patent Office on the 28th
February 1881.
ST. GEORGE LANE FOX, of Telegraph Street, in the City of London. " IMPROVE-
;MENTS IN ELECTRIC LAMPS, IN THE MANUFACTURE OF PARTS THEREOF, AND IN
APPARATUS FOR EXHAUSTING THEM, THE EXHAUSTING APPARATUS BEING ALSO
APPLICABLE TO OTHER PURPOSES."
My Invention consists of improvements in the construction of electric lamps, in
the manufacture of an improved burner or "luminous bridge" for such lamps, and
in apparatus for exhausting the lamps, which apparatus although specially designed
for the above purpose, may also be employed for exhausting other articles. My
improved lamps and luminous bridge or burner may be used in conjunction with
the system of distribution and regulation of the electric current, as explained in
the Specifications of several former Letters Patent granted to me, and dated
respectively 9th October 1878 (No. 3988), 12th October 1878 (No. 4043), and
14th November 1878 (No. 4626), or otherwise.
In my improved lamp the light results as before from the incandescence of a
continuous conductor composed of some highly refractory material having a great
electrical resistance, and the extent of the luminous surface is dependant as before
on the intensity and quantity of light required.
Figure 1 is an elevation partly in section of my improved lamp; Figure 2 is a
view of some of the parts at right angles to Figure 1. A is the lamp globe or
flask; a, the luminous bridge, made by preference as hereinafter described; b is a
small block of porcelain, steatite, or other suitable material, between the ends of
the bridge a to keep them apart; e is a pair of metallic clips through which the
current passes, and which press against the outer surface of the said ends, and so
form the electrical contact. The clips c may be made with advantage of steel wire
passed through and cemented to a block d of porcelain, steatite, or other suitable
material. Borax fused by means of a blow pipe makes a good cement for this
purpose. The upper ends of the clip wires c have soldered to them short pieces of
platinum wire e, e, which enter the lower ends of and are fused into glass tubes f, f.
These glass tubes are filled with mercury, the chief object of which is to prevent
leakage into the lamp, but it also forms the electrical communication between the
luminous bridge and the outside of the globe A. The tubes f, f, and another tube h
which connects the globe with the apparatus by which the lamp is exhausted, pass
through and fit tightly in holes in an india rubber stopper g which closes the neck
of the globe, and the neck is made slightly tapered to prevent the stopper being
forced in by the pressure of the atmosphere. The upper surface of the stopper is
covered by a layer of mercury i to make the joint perfectly air tight. To prevent
the mercury being spilt, some marine glue or other suitable material may be placed
above it as shown at j.
I make my improved luminous bridge or burner of vulcanized fibre which has
been baked at a white heat. In order to prepare this bridge or burner, I cut from
a sheet of vulcanized fibre (from 1/2th to 100th of an inch thick, according to the
required resistance of the lamp) a piece or strip, narrow in the middle and com-
paratively wide at the ends, as seen in Figure 3. The thickness, width, and length
of the strip of the vulcanized fibre, depend as already mentioned upon the resistance
required; any resistance can be easily obtained between 10 and 200 ohms. (British
Association units). A conductor made from a strip 1/2" thick, 1/16" wide, and 13%, long
(in the narrow part), will have a resistance of about 30 ohms. Having cut the
strips of the form above described, I bend each as shown in Figures 4 and 5, so
that while the broad ends are brought parallel to each other and nearly together,
the narrow portion is in the form of a loop or bow; I then arrange several of them

page_text: together as represented in Figures 6 and 7, so that the broad parts are pressed by
means of a spring k between plates 1, 7, of steel or porcelain, the plates separating
the two broad parts of each strip, a being the same thickness as the small block of
porcelain b, which keeps them apart in the lamp, Figures 1 and 2. The set of
strips thus held by means of the spring k I then place in a crucible (see Figure 8),
filled or packed with powdered charcoal or plumbago. I raise the crucible to a
bright red or white beat, taking care however not to so heat the spring k that it
will loose its elasticity; for this purpose the main portion or body of the spring is
kept out of the crucible.
When baked as above described, the strips or luminous bridges a, a, are carbonized
by heating them at a white heat in benzole vapor or other suitable carbon compound
This can be conveniently effected as follows:-The bridge a having been mounted
in clips similar to the clips c, Figures 1 and 2, in a vessel containing only rarefied
benzole vapor or carbon compound, an electric current is then passed through it so
as to raise it to a white heat; the heated surface will rapidly assume a light
grayish appearance, while the resistance of the bridge will be rapidly diminished.
This process is continued for about half a minute, or until the bridge has been
reduced to the required resistance. The broad parts are carbonized by passing a
more powerful current through them, and during this operation, which is also
conducted in a vessel filled with benzole vapor or carbon compound, the narrow
part or bridge proper is immersed in some conducting medium, such as mercury
(see Figure 9). The broad parts must be very well carbonized, so that their
resistance may be very small. Instead of heating the bridges by the passage of an
electric current, they may be suspended in a porcelain vessel filled with the benzole
vapor or carbon compound, the porcelain vessel being then raised to a white beat
in a furnace.
The vulcanized fibre used for making the bridge should be as free as possible
from mineral substances containing oxygen. In order to remove all traces of
mineral matter the bridge when finished should be boiled in nitro hydrochloric acid
and then in hydrofluoric acid.
The modo and means hereinbefore described of mauufacturing luminous bridges
or burners from vulcanized fibre may also be applied to the manufacture of burners
from other suitable materials containing a substance of a highly refractory nature,
such for example as paper.
The lamp constructed as before explained, and having a luminous bridge made
as described mounted therein, must then be exhausted. One form of apparatus
I employ for this purpose is represented in Figure 10, and is arranged as follows:-
A vertical glass tube B, 30 inches high or more, terminates at its upper end in a
bulb C, at the upper part of which is a ground neck D, which at certain times
receives the ground lower end of a glass rod E. This neck opens into another
bulb Fabove, through the neck G of which the glass rod E also passes; the part
of the rod which passes through this neck G is covered with india rubber or other
suitable material, so that the rod while capable of being forced up and down so as
to open and close the neck D of the lower bulb, shall all the while preserve a tight
joint in the neck of the upper bulb. Above the upper bulb is a cup H. To the
lower end of the glass tube I connect one end of a strong flexible tube I of greater
length, to the other end of which an open vessel K. is fitted. It will be of advantage
to interpose an air trap L, L, between the glass tube B and the flexible tube I, as
shewn, but this air trap is not essential. To the glass tube B just below the
bulb C is connected another vertical tube M about 40 inches long above the level
of the cup, the upper end of which tube is connected by a bend N to a tube O
hermetically joined to the tube h, which communicates with the interior of the
globe A of the lamp, passing through the india rubber stopper as herein before
described. These tubes with their bend constitute the exhausting tube.
The action of the apparatus is as follows:-The open vessel K having been filled
or partly filled with mercury when in a lowered position, is raised to such a height
that while it becomes nearly empty, the. mercury rises in the two bulbs C and F

page_text: filling the same up to the cup H. The neck G of the upper bulb F is then closed
by the rod E, the neck D of the lower one being left open. The open vessel K is
then lowered about 36 inches in order that the mercury may fall well below the
point where the tube M communicates with the tube B. The consequent fall of
the mercury in the bulbs produces a vacuum, which will be filled by the air in the
lamp forcing its way through the exhausting tube h, O, N, M. The open vessel is
then again raised, the neck G of the 'upper bulb being opened to allow the air to
escape. The two bulbs C and F again become full of mercury, the neck G of the
upper is again closed, the open vessel again lowered, and the operations are
continued until the lamp is almost exhausted. The pumping action is then
somewhat modified thus: The open vessel K is raised and lowered several times,
while the rod E is out so as to make the mercury rise and fall in the bulbs,
which should now be slightly warmed in order to evaporate any moisture which
may be present on their sides. The mercury must not be allowed to fall below
the point of communication with the exhausting tube M while the rod is out,
otherwise the mercury will be forced up the said tube into the lamp. Having
got rid in this manner of all traces of aqueous or other vapor, the rod E is
again inserted (while the opened vessel is raised) into the neck G of the upper
bulb, leaving the neck D of the lower bulb open; the open vessel is then again
raised and lowered several times, so that the mercury alternately rises and falls
in the bulbs, and in this way all traces of air from the surface of the tubes or
bulbs will collect in the upper bulb F. The open vessel K is then placed at such
a height that the mercury fills the lower bulb and is just above its neck D. The
rod E is then forced down so as to close this neck D, and the open vessel K is
lowered until the mercury is below the point of communication with the exhausting
tube M, again raised and so on. The upper bulb F above the neck of the lower
has for object to render the vacuum in the lower more perfect.
By using sulphuric acid with the mercury so as to wet the surface of the glass
bulb C and the ground joint at the neck D the upper bulb may be dispensed with
altogether, but the acid must be very pure, and the cup should be closed in at the
top, leaving however a sufficient opening for the rod to be freely moved up and
down.
The lamp A having been thoroughly exhausted, a current is passed through it so
as to render the burner or luminous bridge a incandescent, the pumping action
being continued as rapidly as possible. The incandescence and pumping aro
continued until nothing more comes off, or for about 2 or 3 days, when the tube /
is melted near the top of the lamp and the lamp thereby sealed from the
atmosphere. A small bulb may be introduced in the exhausting tube just below
the bend to prevent mercury running over the bend, but this is not necessary when
the tube M is 40 inches long or more.
In some cases I dispense with the long tubes M and O, and connect the tube B
with the tube of the lamp by means of a pipe P (shown in dotted lines) in which
is a valve Q opening downwards. When the mercury in the pipe P falls there is
a free air passage between the lamp and the bulb C through the valve Q, but
when the mercury again rises as high as the valve Q the valve closes.
Although I have described mercury as the liquid used in the exhausting
apparatus, other suitable liquids may be employed, such, for example, as sulphuric
acid, but in that case it would be desirable to have means of exhausting the
vessel K to avoid the necessity of having the flexible tube I made very long. In
any case, instead of this tube being made flexible it may be worked up and down
like a piston or telescopically.
When sulphuric acid is used the apparatus may with advantage be constructed
as represented in Figure 11. A is a glass or porcelain vessel, the size of which
will depend upon the number of lamps intended to be exhausted simultaneously;
in practice I find that its volume may advantageously be about equal to that of
all the lamps together. The vessel A has a small neck at D, opening into a small
bulb C, and closed by a ground glass rod K, which rod fits loosely into the neck

page_text: of the cup C; T is a pipe communicating between the bottom of the vessel A and
the lower part of a vessel B below, which vessel is slightly larger than A. The
pipe T fits tightly into the neck of B; E is a tube connecting the upper part of the
vessel B with a pump, which may be worked by steam power or otherwise; U is
an air drier interposed in the pipe E; P is a tube communicating between the 5
pipe T and the lamps L to be exhausted. In this tube is a valve V (shewn on a
larger scale in Figures 12 and 13) which prevents the acid rising above this valve,
but which opens downwards, so that when the acid is below the point where P
joins T, there is a free air passage between the lamps L and the vessel A. The
action of the apparatus is as follows:-The vessel B being full of acid and the 1
neck D of the vessel A being open, air is forced by the pump into B through the
tube E, the acid is thus caused to rise through T into the vessel A; part of the
acid passes up the pipe P to the valve V, which then closes, and the air escapes
by its only outlet, viz., the neck D. When the acid has reached to about the
middle of the bulb C the neck D is closed by the rod K. The vessel B is then
exhausted by the pump, the acid in A and in the pipe P consequently falls through T
into B until it is below the connection of P and T. The valve V being then open
some of the air from the lamps is exhausted into A; the acid in B is then forced
up again; the rod K is again removed to allow the air to escape as before.
When the acid has reached the middle of C the neck D is closed, B again exhausted,
and so on, and these operations are continued as long as is found necessary; G is
a valve weighted so as to open outwards as the pressure due to the column of acid
when it reaches about the middle of the cup C. The acid should be pure and kept
as cool as possible.
Although the apparatus represented in Figures 10 and 11 respectively have been
specially designed for the purpose of exhausting electric lamps, they may also be
employed for exhausting other articles, as will be readily understood.
Having now described the nature of my said Invention, and in what manner
the same is to be performed, I declare that I claim,—
First. The combination of parts forming improved electric lamps, substantially
as hereinbefore described and represented in Figures 1 and 2.
Second. The manufacture of burners or luminous bridges for electric lamps from
vulcanized fibre, substantially in the manner herein before described.
Third. The manufacture of burners or luminous bridges for electric lamps by
bending into the form of burners appropriately shaped strips of a suitable material
containing a substance of a highly refractory nature, submitting them when so
bent and by means of an appliance, such as that hereinbefore described, to a white
heat and then carbonizing them, by raising them by means of an electric current,
or otherwise, to a white heat in benzol vapor or other suitable carbon compound,
all substantially as herein set forth with reference to Figures 3 to 9.
Fourth. The improved exhausting apparatus, arranged and acting substantially
as hereinbefore described and represented in Figuro 10.
Fifth. The improved exhausting apparatus, arranged and acting substantially as
herein before described and represented in Figure 11.
In witness whereof, I, the said St. George Lane Fox, have hereunto set my
hand and seal, this Twenty fifth day of February, One thousand eight
hundred and eighty one.
ST. G. LANE EOX. (L.S.)