IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by the said Joseph Wilson Swan at the
Office of the Commissioners of Patents on the 2nd January 1880.
JOSEPH WILSON SWAN, of Newcastle-on-Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN ELECTRIC LAMPS."
It is well known that in that class of electric lamps in which light is produced
by the incandesence of a carbon conductor contained in a closely sealed globe of
glass more or less exhausted of air two difficulties have hitherto impaired their
utility.
1st. The carbon conductor in process of use gradually' wasted and ultimately'
broke.
2nd. The interior surface of the globe containing the incandescent carbon became
coated with a carbonaceous deposit, which obscured the light.
I have discovered the means of avoiding both these faults (which are dependent
the one upon the other) as follows, that is to say :-
I have found that if the globe or vessel of glass containing the carbon to be
rendered incandescent be exhausted of air to a high degree of exhaustion by means
of a "Sprengel pump," whilst the carbon contained within it is raised (by the
passage of a current of electricity through it) to the same or a higher degree of
incandescence as that ultimately required to be produced in using the lamp, and if
the lamp be hermetically sealed whilst exhausted of air under the conditions
specified the lamp so prepared is durable, both the faults above mentioned being
eliminated, the incandescent carbon enduring without waste, and the interior
surface of the glass globe keeping free from carbonaceous deposit.
'

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Joseph Wilson Swan in the Great Seal Patent Office on the 2nd July
1880.
JOSEPH WILSON SWAN, of Newcastle on Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN ELECTRIC LAMPS."
It is well known that in that class of electric lamp in which light is produced
by the incandescence of a carbon conductor contained in a closely sealed globe of
glass more or less exhausted of air two difficulties have hitherto impaired their
utility.
1st. The carbon conductor in process of use gradually wasted and ultimately
broke.
2nd. The interior surface of the globe containing the incandescent carbon becamo
wasted with a carbonaceous deposit and obscured the light.
I have discovered the means of avoiding both these faults (which are dependent
the one upon the other) as follows, that is to say:-
I have found that if the globe or vessel of glass containing the carbon to be
rendered incandescent be exhausted of air to a high degree of exhaustion by means
of a "Sprengel pump," whilst the carbon contained within it is raised (by the
passage of a current of electricity through it) to the same or a higher degree of
incandescence as that ultimately required to be produced in using the lamp, and if
the lamp be hermetically sealed whilst exhausted of air under the conditions
specified the lamp so prepared is durable, both the faults above mentioned being
eliminated, the incandescent carbon enduring without waste, and the interior
surface of the glass globe keeping free from carbonaceous deposit.
In carrying out my said Invention I take a rod, filament or lamina, of carbon of
a length and thickness proportioned to the current to be employed in heating it;
for example, it may be two inches in length and one fiftieth to one hundredth of
an inch in sectional area. This rod, filament or lamina, I clip at its extremities by
means of a pair of platina clips, to which are attached platina wires, which serve
for conducting the current through the lamp. These conducting wires pass through
the glass which encloses the clips and the carbon, and are sealed into it by fusion
of the glass around them. I attach the globe or bulb thus arranged to the exhaust
tube of a Sprengel air pump. This I do in the manner well understood and
practised in the procuring of high vacua, the attachment being made by means of a
small branch tube fixed on to some part of the globe or bulb by the blow pipe.
This attachment being made I work the pump until not more than the one
thousandth part of an atmosphere remains in the globe or bulb. I then pass a
current of electricity through the carbon, so as to render it incandescent, and
during the incandescence of the carbon I continue the exhaustion further until the
residue of air is so small as practically not to affect the durability of the carbon
when kept in a state of incandescence. By exhausting the air under these.con-
ditions a much nearer approach to an absolute vacuum is attained than otherwise
would be possible.
Having thus stated the nature of my said Invention, and described the manner
in which it may be carried into effect, I claim, the production of an incandescent
carbon electric lamp from which the air has been exhausted while the carbon is in a
state of incandescence, and which is hermetically sealed during exhaustion.
In witness whereof, I, the said Joseph Wilson Swan, have hereunto set my
hand and seal, the First day of July, in the year of our Lord One thousand
eight hundred and eighty.

page_text: LETTERS PATENT to Joseph Wilson Swan, of Newcastle on Tyne, in the
County of Newcastle, Chemist, for an Invention of "IMPROVEMENTS IN
ELECTRIC LAMPS.”
j
PROVISIONAL SPECIFICATION left by the said Joseph Wilson Swan at the
Office of the Commissioners of Patents on the 2nd January 1880.
JOSEPH WILSON SWAN, of Newcastle-on-Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN ELECTRIC LAMPS."
It is well known that in that class of electric lamps in which light is produced
by the incandesence of a carbon conductor contained in a closely sealed globe of
glass more or less exhausted of air two difficulties have hitherto impaired their
utility.
1st. The carbon conductor in process of use gradually wasted and ultimately
broke.
2nd. The interior surface of the globe containing the incandescent carbon became
coated with a carbonaceous deposit, which obscured the light.
I have discovered the means of avoiding both these faults (which are dependent
the one upon the other) as follows, that is to say :—
I have found that if the globe or vessel of glass containing the carbon to be
rendered incandescent be exhausted of air to a high degree of exhaustion by means
of a "Sprengel pump," whilst the carbon contained within it is raised (by the
passage of a current of electricity through it) to the same or a higher degree of
incandescence as that ultimately required to be produced in using the lamp, and if
the lamp be hermetically sealed whilst exhausted of air under the conditions
specified the lamp so prepared is durable, both the faults above mentioned being
eliminated, the incandescent carbon enduring without waste, and the interior
surface of the glass globe keeping free from carbonaceous deposit.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Joseph Wilson Swan in the Great Seal Patent Office on the 2nd July
1880.
JOSEPH WILSON SWAN, of Newcastle on Tyne, in the County of Newcastle,
Chemist. "IMPROVEMENTS IN ELECTRIC LAMPS."
It is well known that in that class of electric lamp in which light is produced
by the incandescence of a carbon conductor contained in a closely sealed globe of
glass more or less exhausted of air two difficulties have hitherto impaired their
utility.
1st. The carbon conductor in process of use gradually wasted and ultimately
broke.
2nd. The interior surface of the globe containing the incandescent carbon became
wasted with a carbonaceous deposit and obscured the light.
I have discovered the means of avoiding both these faults (which are dependent
the one upon the other) as follows, that is to say:-:
21
I have found that if the globe or vessel of glass containing the carbon to be
rendered incandescent be exhausted of air to a high degree of exhaustion by means
of a Sprengel pump," whilst the carbon contained within it is raised (by the
passage of a current of electricity through it) to the same or a higher degree of
incandescence as that ultimately required to be produced in using the lamp, and if
the lamp be hermetically sealed whilst exhausted of air under the conditions
specified the lamp so prepared is durable, both the faults above mentioned being
eliminated, the incandescent carbon enduring without waste, and the interior
surface of the glass globe keeping free from carbonaceous deposit.
In carrying out my said Invention I take a rod, filament or lamina, of carbon of
a length and thickness proportioned to the current to be employed in heating it;
for example, it may be two inches in length and one fiftieth to one hundredth of
an inch in sectional area. This rod, filament or lamina, I clip at its extremities by
means of a pair of platina clips, to which are attached platina wires, which serve
for conducting the current through the lamp. These conducting wires pass through
the glass which encloses the clips and the carbon, and are sealed into it by fusion
of the glass around them. I attach the globe or bulb thus arranged to the exhaust
tube of a Sprengel air pump.
This I do in the manner well understood and
practised in the procuring of high vacua, the attachment being made by means of a
small branch tube fixed on to some part of the globe or bulb by the blow pipe.
This attachment being made I work the pump until not more than the one
thousandth part of an atmosphere remains in the globe or bulb. I then pass a
current of electricity through the carbon, so as to render it incandescent, and
during the incandescence of the carbon I continue the exhaustion further until the
residue of air is so small as practically not to affect the durability of the carbon
when kept in a state of incandescence. By exhausting the air under these con-
ditions a much nearer approach to an absolute vacuum is attained than otherwise
would be possible.
:
.
Having thus stated the nature of my said Invention, and described the manner
in which it may be carried into effect, I claim, the production of an incandescent 4
carbon electric lamp from which the air has been exhausted while the carbon is in a
state of incandescence, and which is hermetically sealed during exhaustion.
In witness whereof, I; the said Joseph Wilson Swan, have hereunto set my
hand and seal, the First day of July, in the year of our Lord One thousand
eight hundred and eighty……
!
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