IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS
Year: 1881

page_text: LETTERS PATENT to Edward Griffith Brewer, of 33, Chancery Lane, in the
County of Middlesex, for an Invention of "IMPROVEMENTS IN AND CONNECTED
WITH ELECTRIC LAMPS." A communication from abroad by Thomas Alva
Edison, of Menlo Park, in the State of New Jersey, United States of
America.
PROVISIONAL SPECIFICATION left by the said Edward Griffith Brewer
.
at the Office of the Commissioners of Patents on the 8th February 1881.
EDWARD GRIFFITH BREWER, of 33, Chancery Lane, in the County of Middlesex.
"IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS." A communication
from abroad by Thomas Alva Edison, of Menlo Park, in the State of Now Jersey,
United States of America.
As is well known the lamp devised by said "Edison' and used in his system
consists of a strip or filament of incandescing material of high resistance bent into
a loop (now commonly known as the "horse shoe" carbon), hermetically sealed
within a glass enclosing globe. It is well known that carbon expands by heating,
especially with the very high heat necessary to incandescence. This proved in the
past a serious difficulty to the successful use of carbons in lamps, as the carbons
then known were inflexible, and consequently after short use either the carbons
were fractured, or else the connections between the carbons and the conductors
thereto were destroyed by the expansion. The so called "Edison" carbons, how-
ever, in addition to possessing all the other qualities needed, possess the quality of
flexibility as well as of high resistance. By the use of such a carbon the object
of one portion of this Invention can be effected, which is to make a lamp in which
the light giving portion is in a straight line in order to give a straight line of light
instead of a circular or elliptical one.
To do this the glass neck in which the carbon is held is extended upward in a
vertical arm, so that the lower end of the carbon is held as usual, and the upper
end supported by a suitable arrangement at the top of this arm, along which one
of the conducting wires passes to the upper end of the carbon.
As the conductors which lead to the carbon are metallic and therefore com-
paratively good conductors of heat, they may in use be heated to a considerable

page_text: degree where they are sealed into the glass, when owing to difference in the rate
of expansion of the wire and glass there may be danger sometimes of their
separation at the point of union, which would result in the destruction of the
vacuum and consequently of the lamp. In the so called "Edison" lamp as
ordinarily made there is a minimum of danger on this score, owing to the fact that
by the proper adjustment of the resistance of the carbon an exceedingly small
conductor is used. In some cases it is desirable to still further reduce this danger,
and also to provide lamps in which larger conductors either for. a greater number
of carbons in multiple are or of lower resistance may be used, with a minimum of
danger from the source referred to. This may be accomplished by interposing a
larger interval between the clamps of the carbon and the point at which the wires
are sealed in the glass enclosing globe, so that the length of the wire between the
two points is such that heat enough to be dangerous will not be conducted through
the wire to the point of sealing. As the carbons are flexible, and the conductors
even of the largest size are so small as also to be flexible, it is desirable that the
conductors should be supported very near to the clamps, in order to give to the
carbons and their supports the necessary stability.
The object of another portion of this Invention is to furnish a lamp in which
these desired results shall be accomplished, and it consists in placing a support for
the conductors at a distance above the point where they are sealed into the glass,
the conductors being sealed to this support so that they will be held in an erect
position. To this end a tube or rod of glass has fashioned upon it two discs, one
at the upper end into both of which the conductors are sealed, the upper one being
nearest to and supporting the clamps of the carbon, and the lower one being scaled
into the prolonged neck of the enclosing globe.
This part of the Invention it is evident may be carried into effect in other
ways.
In some locations may be desired a simple lamp capable of being suspended or
swung divested of all parts not necessary in order that it may be cheaply made.
To this end another portion of this Invention consists in a lamp composed of an
incandescing conductor, a hermetically sealed glass sphere, and protruding con-
ductors, by which it may be readily attached to other conductors and be suspended
therefrom.
The object of another part of this Invention is to furnish a device by means of
which the light of a single lamp of an electric lighting system may be increased or
diminished without affecting any others of the series, and to this end it consists in
the interposition in the circuit of the lamp of a resistance the force of which may
be varied at the will of the operator by simply turning a key. This resistance
consists of a piece of stiff heavy carbon of a suitable shape, and having at various
An arm which forms
points of its surface a number of metal contact pieces.
part of the circuit is arranged so that it may be turned in such a way as to
touch one or another of the contact pieces, thus placing more or less of the
carbon in the circuit and increasing or decreasing the resistance.
In these incandescent electric lamps difficulty is sometimes experienced from the
fibre bending and falling over. The object of this portion of the Invention is
to obviate this difficulty by constructing a device which will hold the carbon in
an upright position, and the Invention consists in employing a supporter made
of glass or other insulating material having a support at its upper end by which
the carbon loop is held erect; this supporter extends upward from the glass
neck in which the wires are scaled.
"
In the so called "Edison lamp the glass stem through which the wires
pass has a round bulb at the top in which the wires are sealed, and a round
enlargement below this bulb which supports the exterior globe of the lamp. The
interior of this globe being a vacuum while the interior of the inside stem is filled
with air, a considerable pressure is exerted on the inner surface of the upper
bulb.
And this pressure is exerted on the weakest part, a concave surface.

page_text: Therefore in the present Invention this bulb is made with a depression in its
top so that the atmospheric pressure is exerted on a convex surface which is less
likely to be injured thereby.
In some cases instead of a hollow spherical enlargement of the stem as a support
for the globe it may be desirable to use a solid projection extending from the
side of the stem as a support for the globe, and to which the globe is sealed.
This part of the Invention then consists, 1st, in constructing the upper bulb
with a concavity or depression in its top; and, 2nd, in a support for the globe
formed of a projection extending laterally from the stem and forming a part
thereof.
The object of another portion of this Invention is to furnish a different means
for retaining a vacuum in the enclosing globe of the lamp. A socket of wood
or other insulating material has a glass piece set into it which is somewhat in
the form of the letter W the central arch thereof extending up within the
enclosing globe, and having the conducting wires passing through and sealed
within it.
The enclosing globe sets into this glass piece, both being ground so as to fit
tightly together.
The remaining space is partly filled with mercury, and a package of rubber is
used to keep the mercury in place.
Hitherto in manufacturing lamps known as Edison it has been the custom to
blow a bulb upon the end of the supporting tube, the conducting wires passing
through and being sealed into the bulb.
In such construction the wires were in sealed contact with the glass for a length
equal only to or a little more than the thickness of the glass of the bulb. It seems
desirable sometimes to provide for a larger sealing, the accomplishment of which
forms another portion of this Invention. This is done by heating the end of the
tube which is to form the inner or supporting end in the finished lamp with the
conducting wires laid therein, so as to be equally heated until a welding heat is
reached, when the end is welded together for a suitable distance by pressure
applied by squeezers, clamps, or other suitable devices, the wires being sealed
hermetically between the portions of the glass so brought together.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edward Griffith Brewer, in the Great Seal Patent Office on
the 8th August 1881.
"
EDWARD GRIFFITH BREWER, of 33, Chancery Lane, in the County of Middlesex.
IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS." A communication
from abroad by Thomas Alva Edison, of Menlo Park, in the State of New Jersey,
United States of America.
As is well known, the lamp devised by said Edison and used in his system
consists of a strip or filament of incandescing material of high resistance bent into
a loop, now commonly known as the "horse-shoe carbon," hermetically sealed
within a glass enclosing globe. It is well known that carbon expands by heating,
especially with the very high heat necessary to incandesence. This proved in
the past a serious difficulty to the successful use of carbons in lamps, as the carbons
then known were inflexible, and consequently after short use either the carbons
were fractured or else the connections between the carbons and the conductors
thereto were destroyed by the expansion.
The carbons of said Edison's Invention however in addition to possesing all
the other qualities needed, possess the quality of flexibility, the carbons made by
the processes before made known by said Edison being exceedingly flexible as well
as of high resistance. By the use of such a carbon the object of one portion of
this Invention is effected, which is to make a lamp in which the light giving
portion is in a straight line in order to give a straight line of light instead of a
circular or elliptical one.
To do this the glass neck in which the carbon is held is extended upward in a
vertical arm, so that the lower end of the carbon is held as usual, and the upper
end supported by a suitable arrangement at the top of this arm along which one
of the conducting wires passes to the upper end of the carbon.
This is illustrated in Figure 1 of the accompanying Drawings, in which A is
the enclosing globe of glass, preferably cylindrical in shape with a dome-shaped
top, the lower end being drawn into a neck N. A glass support B is made with
its lower end fashioned into a supporting neck b₁, the upper part into a bulb b
These parts are united at the line x, x.
Upon the bulb b is secured a glass arm D, rising to a little greater height
above b than the length designed to be given to the carbon to be used, the arm D
then turning at about a right angle as shown at d.
A conductor 2 is secured to the arm D either by being fused therein through
its length, or at intervals a, a, a, or by being bound thereto, or in any other
convenient manner. The conductor 2 has at its inner end a clamp c¹, in which is
secured one end of the straight flexible carbon filament C, whose lower end is in
clamp c upon the inner end of conductor 1. Conductors 1 and 2 pass through and
are sealed into b.
In the manufacture of the lamp, the supporting arm, the conductors, and the
carbon are first placed in position upon b. B and A being then united and A.
exhausted in the manner more fully described in Letters Patent, No. 578, of
February 10th 1880.
This construction furnishes a lamp in which the incandescent material is in a
line, giving a straight line of light, the arm D supporting the upper end at a
proper height.
The carbon being flexible bows slightly upon expansion under the influence of
heat, avoiding the danger of fracture of the carbon, or the destruction of its union
with the conductors, which has beset former attempts in this line.

page_text: As the conductors which lead to the carbon are metallic, and therefore com-
paratively good conductors of heat, they may in use be heated to a considerable
degree where they are sealed into the glass, when owing to difference in the
rate of expansion of the wire and glass there may be danger sometimes of their
separation at the point of union, which would result in the destruction of the
vacuum and consequently of the lamp.
In the lamps ordinarily made by said Edison there is a minimum of danger on
this score owing to the fact that by the proper adjustment of the resistance of the
carbon an exceedingly small conductor is used.
In some cases it is desirable to still further reduce this danger, and also to
provide lamps in which larger conductors, either for a greater number of carbons in
multiple arc or of lower resistance, may be used with a minimum of danger from
the source referred to.
This may be accomplished by interposing a larger interval between the clamps
of the carbons, and at the point at which the wires are sealed in the glass enclosing
globe, so that the length of the wire between the two points is such that heat
enough to be dangerous will not be conducted through the wire to the point of
sealing.
As the carbons are flexible and the conductors, even of the largest size, are so
small as also to be flexible, it is desirable that the conductors should be supported
very near to the clamps in order to give to the carbons and their supports the
necessary stability. The object of another portion of this Invention is to furnish a
lamp in which these desired results may be accomplished, and it consists in placing
a support for the conductors at a distance above the point where they are sealed
into the glass, the conductors being sealed to this support, so that they will be held
in an erect position. To this end a tube or rod of glass has fastened upon it two
discs, one at the upper end, into both of which the conductors are sealed, the upper
one being near to and supporting the clamps of the carbon, and the lower one being
sealed into the prolonged neck of the enclosing globe. This part of the Invention
is.illustrated in Figures 2 and 3 of the Drawings. A is the glass enclosing globe,
with its lower end fashioned into a neck A¹ left open when first made; B is the
incandescing conductor of flexible high resistance carbon attached to clamps b, b, on
the terminals of conductors 1, 2.
In Figure 2 C1, C2, are two glass discs connected by a glass rod or connection c.
The conductors 1, 2, pass through and are sealed into the discs C1, C2. So scaled
the discs, conductors, and carbon are passed up into the globe, and the open end of
the neck A¹ is then hermetically sealed to the disc C', and the globe is exhausted
in the usual manner. By this means the points of sealing which guard the vacuum
are removed to a distance from the source of heat, while the carbons and the
conductors are suitably supported.
In
In Figure 3 the conductors 1, 2, are fastened to a glass rod C, either along the
entire length of the rod or at intervals. The rod with the attached conductors and
carbon is then passed into the open neck A¹, which is sealed around the rod at a
distance from its upper end, the same results following as in the other case.
some locations may be desired a simple lamp capable of being suspended or swung,
divested of all parts not necessary in order that it may be cheaply made. To this
end another portion of this Invention consists in a lamp composed of an incan-
descing conductor, a hermetically scaled glass sphere, and protruding conductors,
by which it may be readily attached to other conductors, and be suspended there-
from. In the Drawings Figures 4 and 5 represent such a lamp.
A is the glass enclosing globe made round, but with an aperture left at the
point a B is the carbon attached to clamps b, b, on the terminals of the con-
ductors 1, 2.
c, Figure 4, is a glass disc, in which are sealed the conductors 1, 2; it may or
may not be provided with a handle of glass c¹. The wires 1, 2, being sealed in the
disc and the carbon properly attached the disc. is passed into the globe through the
aperture, the edges of which are then hermetically sealed upon the disc.

page_text: In Figure 5 the conductors 1, 2, with the attached carbon are fastened tempo-
rarily upon or to a handle or support C, and then passed into the globe, the handle
or support C keeping the conductors in their proper relative position. The
aperture at a is then hermetically sealed by fusion at its edges, and the support or
handle C removed.
The object of another portion of this Invention is to furnish a device by means
of which the light of a single lamp of an electric lighting system may be increased
or diminished without affecting any others of the series, and to this end it consists
in the interposition in the circuit of the lamp of a resistance the force of which.
may be varied at the will of the operator by simply turning a key. This resistance
consists of a piece of stiff heavy carbon of a suitable shape, and having at various
points of its surface a number of metal contact pieces. An arm, which forms part
of the circuit, is arranged so that it may be turned in such a way as to touch one
or another of the contact pieces, thus placing more or less of the carbon in the
circuit, and increasing or decreasing the resistance. This is illustrated in Figures 6
and 7, the former being a view of a lamp in which this Invention is used, and the
latter a detail view of the resistance.
1, 2, are the wires of an electric circuit passing up through the base of the lamp
to the carbon C, A, being the globe in which the carbon is contained; B is the
hollow base which supports the lamp, and contains the resistance E, E' (Fig. 7.)
This resistance is of the shape shown, and is made of stiff heavy carbon.
Attached to it at various points are metallic contacts a, a, a², &c.
The wire 1, through which the current passes to the light, extends to the metal
arm F in the center of the resistance. The current thus normally passes through
the wire 1, the metal arm F, the contact piece a, and around through the carbon C
to the wire 2. But if it is desired to decrease the force of the light, the arm F
may be turned back until it reaches the contact a', thus requiring the current to
pass through the portion G of the carbon, and interposing so much additional
resistance in the circuit. If a still further diminution of the light is desired, the
arm may be turned back to the contact a², and the resistance thus doubled, and so
on until the whole of the carbon E, E', is included in the circuit 1, 2.
For convenience of manipulation the key D projects out, and terminates
in a thumb screw, so that the arm may be easily turned. E, E', being made,
as stated, of a stiff heavy carbon, furnishes a considerable resistance to the
passage of the current, and as each succeeding section is placed in the circuit
the force of the current is decreased, and the brilliancy of the light corre-
spondingly diminished; and as the key is again turned back, the resistance
decreases and the light increases. In these incandescent electric lamps difficulty is
sometimes experienced from the fiber bending and falling over. The object of this
portion of the Invention is to obviate this difficulty by constructing a device which
will hold the carbon in an upright position, and the Invention consists in employing
a supporter made of glass or other insulating material having a support at its
upper end by which the carbon is held erect. This supporter extends upward from
the glass neck in which the wires are sealed.
Figures 8, 9, 10, and 11, are views of different forms of this device, and Figure 12
is a view of the carbon which may be used. 1, 2, are the wires passing through
the glass neck N, and terminating in the clamps b, b. In each of these clamps is
inserted one end of the carbon A, A, which is bent into a loop.
The glass N is continued upward in the form of a long stem B (as in Figures 9
and 10), which has attached to its end a suitable device for holding the carbon
erect. In the form shown in Figure 9, a projection extends out laterally from near
the top of the stem B, and carries the clamps d made of platinum or other metal
not easily affected by the current, in which is inserted the loop of the carbon A, A,
at the point a.
With such construction it is preferable to construct the carbon with an enlarged
part, as shown at a, Figure 12, in order to give a larger bearing surface for the
clamp d

page_text: In Figure 10 the stem B is shorter and is not bent, and the projection extends
directly upward from its top. The clamp at the end of this projection holds the
Y shaped piece c, preferably of platinum, between the prongs of which the carbon
loop passes, and is thus kept from falling over sidewise. In the form shown in
Figure 11 a loop of glass c, c, extends upward, being placed at right angles with
the carbon loop. The projections n, n, extending upward from the glass loop are
arranged one on each side of the carbon, and so keep it from bending or falling.
In Figure 8 the carbon is differently formed, extending up from the clamps in
straight lines meeting at d. The stem of glass B extends up between the carbons
a short distance, and then branches off into a loop e, e, which passes around above
the point of junction of the carbons; and directly above this point a glass sten
projects downward having on its end the clamp & which holds the ends of the
carbon.
In the lamp described in prior Patents granted to said Edison, the glass stein
through which the wires pass has a round bulb at the top in which the wires are
sealed, and a round enlargement below this bulb which supports the exterior globe
of the lamp. The interior of this globe being a vacuum, while the interior of the
inside stem is filled with air, a considerable pressure is exerted on the inner surface
of the upper bulb, and this pressure is exerted on the weakest part, a concave
surface; therefore it is preferable to make this bulb with a depression in its top,
so that the atmospheric pressure is exerted on a convex surface, which is less likely
to be injured thereby. In some cases instead of a hollow spherical enlargement of
the stem as a support for the globe, it may be desirable to use a solid projection
extending from the sides of the stem as a support for the globe, and to which the
globe is sealed. This part of the Invention then consists, 1st, in constructing the
upper bulb with a concavity or depression in its top; and, 2nd, in a support for
the globe formed of a projection extending laterally from the stem, and forming
a part thereof. These devices are shown in the Drawings, Figure 13 being a
sectional view of the entire lamp, and Figure 14 a sectional view of the interior
glass stem. The dotted lines in Figure 14 show the construction of the bulbs as
heretofore made. A is the exterior globe, and C the interior glass stem through
which the wires 1, 2, of the circuit pass, being sealed in the glass where they pass
through it, and terminating in the clamps c which hold the carbon B. At d a bulb
is blown on the stem, depressed or hollowed out at e.
At D, D, an enlargement is also blown on the glass; but while the glass is soft
it is flattened down and forms the projection shown. This is of the same width
as the lower portion of the globe which it supports, and to which it is hermetically
sealed.
Under some circumstances and for some purposes this form possesses considerable
advantages over the form before described by me, inasmuch as the bulb & is less
liable to breakage, and a better support is afforded to the globe by the pro-
jection D, D.
The object of another portion of this Invention is to furnish a different means
for retaining a vacuum in the enclosing globe of the lamp. A socket of wood or
other insulating material has a glass piece set into it which is somewhat in the
form of the letter W, the central arch thereof extending up within the enclosing
globe, and having the conducting wires passing through and sealed within it. The
enclosing globe sets into this glass piece, both being ground so as to fit tightly
together.
The remaining space is partly filled with mercury, and a packing of rubber is
used to keep the mercury in place.
Figure 15 of the Drawings is a sectional view of a lamp constructed in this way.
W is an insulating base usually of wood; A is the glass socket fitting therein. It
is when seen in section somewhat of the form of the letter W, the central limb
being extended upwardly and forming a support for the wires leading to the clamps,
the wires being suitably sealed therein, this central portion extending up within the
body of the globe B.. The socket A is ground at a and the globe B correspondingly

page_text: ground at b, so that they fit tightly together. A space C is thus left; which is filled
in with mercury forming a liquid seal. Above the mercury is placed a rubber
ring D, which fits tightly and prevents the mercury from escaping. 1, 2, are the
wires of the circuit by which electricity is supplied to the lamp. These wires
terminate in the platinum clamps c which hold the carbon. A portion of the
circuit is formed by the screw d, which may be drawn back to break the circuit
and extinguish the lamp, or vice versa.
After the globe B is blown a stem remains at x, by means of which the air is
exhausted, and the globe is then scaled and the stem broken off leaving the globe
perfectly air-tight. Hitherto in manufacturing lamps as disclosed in prior Patents
granted to said Edison it has been the custom to blow a bulb upon the end of the
supporting tube, the conducting wires passing through and being sealed into the
bulb. In such construction the wires were in sealed contact with the glass for a
length equal to or a little more than the thickness of the glass of the bulb.
It seems desirable sometimes to provide for a larger sealing, the accomplishment of
which forms another portion of this Invention. This is done by heating the end of
the tube which is to form the inner or supporting end in the finished lamp with the
conducting wires laid therein so as to be equally heated until a welding heat is
reached, when the end is welded together for a suitable distance by pressure applied
by squeezers, clamps, or other suitable devices, the wires being sealed hermetically
between the portions of the glass so brought together.
This is illustrated in Figure 16, which is a view of an entire lamp, and in
Figure 17, which represents the inside stem. A is the enclosing globe, and B the
central support through which the conducting wires 1, 2, pass, they being sealed
therein. This support is hollow, and in those lamps previously made has a bulb
blown at its upper extremity, but in this case this extremity is formed into the solid
flat piece of glass a. Before the central tube is placed within the globe the con-
ducting wires are laid therein, after which its end is heated in a blow pipe flame
until the glass becomes soft, when it is pressed down by squeezers or clamps so that
it is flattened around the wires for a suitable distance. This form of construction is
of easy and economical application, secures the wires firmly in place, and affords a
seal so large that danger of breaking at the points of sealing in is greatly
lessened.
What is claimed is,-
First. An electric lamp formed of a straight flexible high resistance filament
enclosed in a hermetically sealed glass globe, substantially as set forth.
Second. The combination with the carbon supporting bulb of a glass arm rising
above the bulb and supporting one end of a straight carbon and the conductor
leading thereto, substantially as set forth.
Third. The combination with the glass enclosing globe and incandescing con-
ductor of an electric lamp of a support hermetically sealed to the globe and
supporting the carbons at a distance above the point of sealing, substantially as
set forth.
Fourth. The combination with the conductors of an incandescent electric lamp of
a glass support, to which the conductors are scaled at two or more points, one near
the clamps and one where the conductors enter the enclosing globe, so that the
latter point is removed a little distance from the former, substantially as set
forth.
Fifth. The electric lamp consisting of an hermetically sealed sphere, an
incandescing conductor, and protruding conductors, substantially as set forth.
Sixth. The combination with the incandescing conductor of an electric lamp and
the key for controlling the circuit thereof of an adjustable resistance cut in or out of
circuit in any desired proportion by the key, substantially as set forth.
Seventh. A carbon resistance made substantially as described and provided with
a series of metallic contacts in combination with a key having an arm for completing
circuit at any desired contact, substantially as set forth.
Eighth. The combination with the incandescing loop of an electric lamp of a

page_text: support arranged to maintain the loop in the normal position, substantially as set
forth.
Ninth. The supporting neck in which the wires leading to the loop are secured
provided with an arm for maintaining the loop in its normal position, substantially
as set forth.
Tenth. In an incandescing electric lamp the supporting neck formed with a con-
cavity at the point where the leading wires pass through and are sealed therein,
substantially as set forth.
Eleventh. The supporting neck formed with a solid glass projection to and upon
which the enclosing globe is supported and sealed, substantially as set forth.
Twelfth. The central tube, conductor, or support for the incandescing conductor
formed with a chamber at its base and fitted to receive tightly therein the neck of
the enclosing globe, substantially as set forth.
Thirteenth. In an incandescing lamp the combination of the chambered central
tube or support and the enclosing globe ground or adapted to fit tightly, substan-
tially as described.
Fourteenth. The combination in an incandescing lamp of the chambered central
tube or support adapted to hold a liquid seal, the enclosing globe having a neck
fitted to the chamber and a packing for securing the liquid scal, substantially as set
forth.
In witness whereof, I, the said Edward Griffith Brewer, have hereunto set
my hand and seal, this Eighth day of August, in the year of our Lord
E. G. BREWER. (L.S.)