Improvements in Electric Glow Lamps,
Year: 1898

page_text: Date of Application, 10th June, 1898
Complete Specification Left, 10th Mar., 1899-Accepted. 15th Apr., 1899
Improvements in Electric Glow Lamps,
We, THE SPIRAL GLOBE, LIMITED, of 5, Fenchurch Street, in the City of
London, and BERTRAM CHARLES EDWARD PARKER, of 5, Fenchurch Street, afore-
said, Electrical Engineer, do hereby declare the nature of this invention to be as
follows:
This invention relates to the manufacture of incandescent electic lamps pro-
vided with a light-refracting medium in the form of a spiral coil of glass rod
whereby the light emitted from the sides of the filament is refracted towards the
end of the lamp.
Heretofore such light-refracting coils have been applied externally of the bulb
but according to the present invention the coil is enclosed within the bulb so that
whilst the coil is equally efficient for the intended purpose it will be protected
from dust and fiom injury in handling the lamp.
With this object the bulb is first blown in the form of a cylinder closed at
one end wherein the coil previously wound of the intended form of the bulb
is placed, after which the cylinder 18 contracted about the coil by the ordinary
operations of glass working (aided, if necessary, by the external air pressure due
to the air being partially exhausted from within) until the bulb is brought to
the intended form, after which the operations of introducing the filament and
completing the manufacture of the lamp are proceeded with in the ordinary way.
Dated this 10th day of June 1898
A. M. & WM. CLARK,
Chartered Patent Agents,
53, Chancery Lane, London
Improvements in Electric Glow Lamps.
We, THE SPIRAL GLOBE LIMITED, of 5, Fenchurch Street, in the City of
London, and BERTRAM CHARLES EDWARD PARKER, of 5, Fenchurch Street, afore-
said, Electrical Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
This invention relates to the manufacture of incandescent electric lamps pro-
vided with a light-refracting medium in the form of a spiral coil of glass rod
whereby the light emitted from the aides of the filament is refracted towards the
end of the lamp.
Heretofore such light-refracting coils have been applied externally of the bulb

page_text: but according to the present invention the coil is enclosed within the bulb so that
whilst the coil is equally efficient for the intended purpose it will be protected
from dust and fiom injury in handling the lamp
With this object a bulb may be first blown of elongated or approximately cylin-
drical torm as shown in Figure 1 of the accompanying drawings forming part
of this specification, the bulb so blown being about 1% times longer than an
ordinary bulb The bulb is then cut cucumferentially at about the line a-b so
as to form a cylinder closed at one end wherein is placed the spirally wound coil d
of glass rod which has been previously wound of the intended form of the lamp
bulb by coiling the plastic glass rod upon a mandiel or otherwise. After the
coil has been placed in the open bulb or cylinder c as shown in half sectional
elevation in Figure 2 the bulb is contracted about the coil by the ordinary
operations of glass working until a bulb of the intended shape is produced us
represented by dotted lines at e with the coil d contained within and closely
embraced by the bulb so as to be retained in position therein
The contraction of the cylinder to form the lamp bulb may be effected by
ordinary manipulation or the open end of the cylinder might first be closed and
the cylinder connected with a tube by which the air may be partially exhausted
from within in order that the external air pressure may assist to produce the
contraction of the bulb about the coil.
Instead of contracting the bulb about the coil as above described, the bulb
may be blown of the ordinary form and afterwards be cut into two parts at its
greatest diameter f-g (Figure 3) and the previously formed spiral coil having
been placed within them, the two parts may be reunited by an over-lapping
equatorial band of thin glass h applied in the plastic state so as to cover the joint
between the juxtaposed edges of the two parts and become welded to said parts
as shown in half-sectional elevation in Figure 3.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1 In an electric glow lamp the combination with the bulb of an internal light-
refracting spiral coil of glass contained within the bulb and embraced by the
walls thereof substantially as and for the purpose specified.
2 The manufacture of an electric glow lamp having an internal, spiral corl
of glass, by blowing a bulb of elongated form, then cutting it open, placing the
previously formed spiral coil of glass therein and contracting the bulb about
the coil until it is brought to its desired form, substantially as described.
A. M. & WM. CLARK,
Chartered Patent Agents,
53, Chancery Lane, London.
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