Improvements in and relating to Electric Incandescence Lamps.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in and relating to Electric Incandescence Lamps.
We, FOREST WILLIAM DUNLAP and JOHN ROBERT QUAIN, both of 3 Tokenhouse
Buildings, in the City and County of London, Electrical Engineers, do hereby
declare the nature of this invention to be as follows:-
Our invention relates to improvements in incandescence lamps used in electric
lighting, and has for object to reflect light from such lamps in a downward
direction while at the same time refracting a certain amount of light in a hori-
zontal and an upward direction.
By the use of our invention we are enabled in the case of pendant lamps to
reflect the light in any desired direction without causing any shadow to be thrown
in an opposite direction.
Our invention consists in the application to the whole of these lamps or any
portions thereof, of a glass coil or coils, comprising any number of threads, the
section of such threads being round, square, triangular or of any other desired
shape.
These glass threads may be arranged around the lamps either directly or
indirectly in any desired manner and direction, or they may, if preferred, be
secured within the bulb prior to its being sealed up.
The threads or coils may be attached to or formed upon only a portion of the
bulb and where we attach the threads to a part only of the bulb we may form
the coil or coils upon a suitable mould and afterwards secure the coil or coils to the
lamp in any convenient manner.
The glass threads may be frosted or tinted, as well as shaped, in any desired
manner.
COMPLETE SPECIFICATION.
Improvements in and relating to Electric Incandescence Lamps.
We, FOREST WILLIAM DUNLAP and JOHN ROBERT QUAIN, both of 3 Tokenhouse
Buildings, in the City and County of London, Electrical Engineers, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
Our Invention relates to an improved light refracting and reflecting envelope

page_text: for incandescent lamps whereby the light rays may be concentrated in the down-
ward or any other direction in which increased illumination may be required.
The Invention is illustrated in the accompanying drawings and will be described
with reference thereto, and it consists in enveloping the bulb A. of an ordinary
incandescent lamp or a portion thereof in a light refracting jacket B B' constructed
of one or more closely wound spiral coils of glass rod of small circular or prismatic
cross section so as to possess throughout its length the property of a bi-convex lens
or of a prism whereby the desired concentrating and magnifying effect is produced.
The glass rod is heated in the blowpipe flame and is closely wound upon a
mandrel of corresponding shape to the lamp bulb, the coils being in close
juxtaposition without however adhering to each other so as to leave sufficient
freedom to enable the coil to be sprung over the bulb of the lamp in order that it
shall retain itself thereon by the inherent elasticity of the glass. As, however,
this elasticity is very limited it is necessary to make the complete envelope in
two parts BB the one applied to the bulb from above and the other from below
and meeting preferably at a point b just above the largest diameter of the bulb
so that the lower part B may be sprung over the largest part of the bulb and will
be self-retaining thereon. The upper part B has a central aperture large enough
to pass over the neck of the bulb and may be held in position by a flange c formed
on the metal collar C which is cemented on to the neck of the bulb in the ordinary
way after the light refracting envelope has been applied.
In order to ensure a permanent attachment of the spiral coil to the bulb and
prevent displacement when the lamp is handled for the purpose of being inserted
in or removed from its holder or otherwise, the adjacent coils of the envelope B B
are firmly united to each other (after the envelope has been applied upon the bulb)
by transparent cement such as ordinarily used for uniting broken glass or
porcelain. Similarly the upper convolution of the lower part B would be cemented
to the lower convolution, of the upper part B1 and the convolutions of both parts
may be cemented to the bulb A where they touch it.
The glass rod of which the above described envelope is made may be of colour-
less or coloured glass, and may be clear or frosted and the two parts of the envelope
may be alike or different in these respects according to the requirements of the
caso.
Where it is not required to apply the envelope to the entire lamp the upper or
the lower half may be employed as may be required. Furthermore when it is
desired to project the light mainly in one particular direction, as in illuminating
shop fronts for the display of goods, the spirally wound coil of glass may be applied
to the side of the lamp bulb, as shewn in Figure 2, in which case the coils would
lie in vertical instead of horizontal planes, the concave side of the spiral coil
fitting closely to the bulb and being firmly attached thereto by transparent cement.
Having now particularly described and ascertained the nature of the said In-
vention and in what manner the same is to be performed, we declare that what
we claim is:-
The combination with an incandescent electric lamp, of a light refracting
envelope formed of a closely wound spiral of glass rod of circular or other section,
applied upon the bulb of the lamp substantially as specified.
Dated this 15th day of February 1897
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.