IMPROVEMENTS IN THE MANUFACTURE OF ELECTRIC BRIDGES FOR INCANDESCENT LAMPS, AND IN THE MEANS EMPLOYED THEREIN
Year: 1881

page_text: LETTERS PATENT to St. George Lane Fox, of Queen Anne's Gate, in the City
of Westminster, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF ELECTRIC BRIDGES FOR INCANDESCENT LAMPS, AND IN THE MEANS
EMPLOYED THEREIN."
PROVISIONAL SPECIFICATION left by the said St. George Lane Fox at the
Office of the Commissioners of Patents on the 8th October 1881.
ST. GEORGE LANE Fox, of Queen Anne's Gate, in the City of Westminster.
"IMPROVEMENTS IN THE MANUFACTURE OF ELECTRIC BRIDGES FOR INCANDESCENT
LAMPS, AND IN THE MEANS EMPLOYED THEREIN."
My Invention has reference to the process of manufacturing electric bridges for
incandescent lamps by immersing baked threads or other suitable fibres in an
atmosphere of coal gas or other carbon compound, and sending an electric current
through them so as to raise them to a white heat and cause the carbon of the
hydro carbon atmosphere to become deposited upon the surface of the bridges,
thereby reducing them to a definite or specified resistance as described in tho
Specification of former Letters Patent granted to me dated 28th August 1880,
No. 3494.
Now my present Invention consists of a method or means of carrying out this
process on a manufacturing scale.
For this purpose I take a number, say 6, more or less, of "Woulfes " bottles or
other suitable vessels which 1 charge with coal gas or other hydro carbon vapor.
Through the stopper or device which closes the mouth of each of these bottles
I pass two wires or rods, terminating at their lower ends in clips, in which the
bridge or filament to be reduced or adjusted is placed. One wire of each of the
bottles is permanently connected to one arm of a double switch by means of a wire
coinion to all the bottles. The other wires of the bottles are connected by
separate and distinct wires with corresponding contact pieces, these contact pieces
being equal in number to the bottles. A single switch connects any one of these
contact pieces as required with the second arm of the double switch. The double

page_text: switch is capable of being connected either with the main wires from a dynamo-
electric machine or other electric generator by means of one pair of stops or
contacts, or with a resistance measuring apparatus of any suitable construction by
means of another pair of stops or contacts.
The action is as follows:-A bridge or filament having been mounted in the
clips of each of the bottles, and the bottles having been charged with coal gas,
I couple up one of the bottles, say bottle No. 1, by means of the single switch with
the double switch, and I turn this double switch so as to connect it with the
dynamo-electric machine. An electric current therefore passes through the bridge
or filament of bottle No. 1 and raises it to incandescence, and therefore carbon
from the gas becomes deposited upon its surface and gradually lowers its
resistance. The double switch during this operation is from time to time turned
on to the measuring apparatus so as to test the resistance of the bridge; and when
it has been reduced almost to the degree finally required, the current is turned on
to bottle No. 2 and so on. In order to allow of instantaneously breaking the
circuit, should there appear to be too much current passing through the bridge,
I insert a spring contact key or other like circuit breaking device in one of the
main wires from the dynamo-electric machine.
Even when a number of bridges have been reduced to the same resistance, an
inconvenience is experienced arising from the fact that after they have been
mounted in the holders of the lamps, the resistance is unequal because of some of
them being pushed further than others into the holders or from other causes. To
overcome this inconvenience after mounting the bridges in the holders, and before
hermetically sealing them in the lamps, I again adjust their resistance to the degree
required. And when I adopt this method the resistance to which the bridges are
reduced in the first adjustment, as herein before explained, should be somewhat
greater than the resistance required in the lamps.

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
8th April 1882.
ST. GEORGE LANE Fox, of Queen Anne's Gate, in the City of Westminster.
"IMPROVEMENTS IN THE MANUFACTURE OF ELECTRIC BRIDGES FOR INCANDESCENT
LAMPS, AND IN THE MEANS EMPLOYED THEREIN."
My Invention has reference to the process of manufacturing electric bridges for
incandescent lamps by immersing baked threads or other suitable fibres in an
atmosphere of coal gas or other carbon compound, and sending an electric current
through them so as to raise them to a white heat and cause the carbon of the
hydro carbon atmosphere to become deposited upon the surface of the bridges,
thereby reducing them to a definite or specified resistance as described in the
Specification of former Letters Patent granted to me, dated 28th August 1880,
No. 3494.
Now my present Invention consists of a method or means of carrying out this
process on a inanufacturing scale.
For this purpose I take a number, say 6, more or less, of " Woulfos" bottles or
other suitable, vessels as represented at W' to W in the diagram shown at Figure 1
of the annexed Drawings. I charge these bottles with coal gas or other hydro carbou
vapor. Through the stopper or device A which closes the mouth of cach of these
bottles, seo Figures 2 and 3, 1 pass two wires or rods B, B', terminating at their
lower ends in clips C, C, in which the bridgo or filament D to be reduced or
adjusted is placed. One wire of each of the bottles is permanently connected to
one arm of a double switch F by means of a wire E, common to all the bottles.
The other wires of the bottles are connected by separate and distinct wires
G' to Go with corresponding contact pieces H to H, these contact pieces being
equal in number to the bottles. A single switch I connects any one of theso
contact pieces as required with the second arm of the double switch F. The
double switch is capable of being connected either with the main wires K, K³, from
a dynamo electric machine, secondary battery, or other source of electricity by
means of one pair of stops or contacts L, L', or with a resistance measuring
apparatus Al of any suitable construction by means of another pair of stops or
contacts L, L³.
The action is as follows:-A bridge or filament D having been mounted in the
clips C, C', of each of the bottles, and the bottles having been charged with coal
gas, I connect up one of the bottles, say bottle W, by means of the single switch I
with the double switch F, and I turn this double switch so as to connect it with
the dynamo electric machine or other source of electricity by means of the stops
or contacts L, L'. An electric current therefore passes through the bridge or
filament D of bottle Wand raises it to incandescence, and therefore carbon from
the gas becomes deposited upon its surfaco and gradually lowers its resistance.
The double switch F during this operation is from time to time turned on to the
measuring apparatus M through the stops or contacts L³, L³, so as to test the
resistance of the bridge, and when it has been reduced almost to the degree finally
required the current is turned on to bottle W and so on.
Sometimes instead of employing a measuring apparatus as before described to
test the resistance of the bridge I measure the resistance of the bridge under
treatment by placing in the circuit of the bridge an instrument as indicated at M,
Figure 4, such for instance as a galvanometer which will shew when a definite
resistance is reached; this method will be found practicable in cases where the
electro motive force is constant and reliable as with secondary batteries, because
the current developed through the bridge will exactly dotermine its resistance.
The double switch F will be unnecessary when such an instrument is used, and the

page_text: contact L may be permanently connected to all the bottles by means of the wire E
common to all, and the contact L' may be connected to the single switch I and
through it to any one bottle at pleasure. The other contacts L, L, are of course
not required. The resistance of the bridge when "hot" can be conveniently
taken when this latter arrangement is employed if a current of suitable strength
be used.
In both the first case and in that last described I employ a spring key or contact
breaker P or other similar device in the circuit K, K¹, to allow of instantly
breaking the circuit when desirable.
Even when a number of bridges have been reduced to the samo resistance, an
inconvenience is experienced arising from the fact that after they have been
mounted in the holders of the lamps, the resistance is unequal because of some
of them being pushed further than others into the holders or from other causes.
To overcome this inconvenience, after mounting the bridges in the holders and
before hermetically scaling them in the lamps, I again adjust their resistance to
the degree required; and when I adopt this method the resistance to which the
bridges are reduced in the first adjustment as hereinbefore explained should be
somewhat greater than the resistance required in the lamps.
In order that the bottles W' &c. may become filled with gas the gas inlet pipo N
(Figure 2) should be carried to nearly the bottom of the bottle. The outlet
pipe O should terminate near a permanent gas jet so as to ensure that all gas
escaping therefrom shall be burnt. If the inlet pipe N were to terminate at the
upper part of the bottle the latter would not be entirely filled with gas and an
explosive mixture of gas and air would be formed therein.
Having now described the nature of my said Invention and in what manner tho
same is to be performed, I declare that I claim,-
First. The employment for the purpose of reducing filaments or bridges for
incandescent electric lamps to a definite or specified resistance, of a series of bottles
or vessels charged with hydro carbon gas or vapor in which the filaments or bridges
are immersed, the said vessels having connections so arranged that the filament or
bridge in any of such vessels can be connected at will with a dynamo-electric machine
or other source of electricity and a measuring apparatus being employed to test
or show the resistance of the filament or bridge, substantially as hereinbefore
described.
Second. In the manufacture of electric bridges in the manner referred to in the
first claim, I claim reducing the bridges in the first place to a resistanco which is
somewhat greater than that required in the lamps and then after they have been
mounted in their holders and before hermetically sealing them in the lamps
reducing or adjusting their resistance to the exact degree required, substantially as
herein before described.
Third. I claim the means or apparatus substantially as hereinbefore described
and shown in the annexed Drawings for manufacturing electric bridges for
incandescent lamps.
In witness whereof, I, the said St. George Lanc Fox, have hereunto set my
hand and seal, this Fifth day of April, One thousand eight hundred and