Improvements in Electric Lighting and in the Means therefor.
Year: 1891

page_text: Date of Application, 12th Sept., 1891
Complete Specification Left. 26th May, 1892-Accepted, 2nd July, 1892
PROVISIONAL SPECIFICATION.
Improvements in Electric Lighting and in the Means therefor.
A communication from abroad by PAUL SEE, of 15, Rue d'Amiens, Lille, France,
Engineer.
I, JOHN CLAYTON MEWBURN of 55 and 56 Chancery Lane in the County
of Middlesex, Fellow of the Chartered Institute of Patent Agents, do hereby
declare the nature of this invention to be as follows:-
In electric lighting by means of arc lamps, I obtain excellent results by placing
the luminous point in an inverted reflector, thus lighting the ceiling or roof which
in its turn reflects the light to all parts of the place to be lighted.
To obtain a good result it is necessary that the lamp should fulfil the following
conditions:-
1st. The luminous point should be perfectly steady, and in order to ensure this I
make the carbons of a suitable diameter in relation to each other, or I can arrange
the mechanism of the lamp so as to obtain the said steadiness by giving one of the
carbons a greater speed than the other.
2nd. I arrange the mechanism of the lamp under the arc so as not to have any
shadow above.
3rd. I place the hollow positive carbon below the negative pointed carbon so
that the luminous rays may be more easily thrown without break towards the
ceiling.
4th. The reflector should be made according to such a curve that the reflected
rays may be thrown to as great a distance as possible from the axis of the lamp.
In this manner the diminution in the intensity of the light by distance is com-
pensated for by the increase in the number of rays reflected.
Thus the part of the ceiling directly above the lamp receives the shortest
distance rays, but the reflector reflects but very few rays upon this part, whilst the
parts of the ceiling which are furthest from the lamp receive a greater number of
luminous rays, whereby the lighting of a large surface of the ceiling is in a manner
regulated.
5th. When the ceiling or roof is at too great a height from the ground, lighting
by means of the reflected rays of electric arc lamps is no longer advantageous in
consequence of the loss of intensity of light by reason of the square of the
distance.
.
There are also places where the ceiling or roof is not horizontal, such as in
buildings which have an arched or curved ceiling or roof. In such cases I arrange
at a short distance above the lamps a horizontal reflector which considerably
increases the amount of light, having in view the fact that light travels the shortest
distance from the centre to the object to be lighted. As this screen-like reflector
may be in the way in the daytime I construct it in such a way as to fold up. The
lamp can be counterpoised and the reflector jointed at the middle so that when the
lamp is pushed up the half reflectors assume an approximately vertical position.
This folding up of the reflector has the advantage of preventing dust lodging upon
the reflecting surface.
I can also arrange the screen reflector to fold into a bellows or zig-zag form
when not in use; the white reflecting surfaces are thus prevented from becoming
dulled by dust and other impurities.
The arrangement above described prevents sparks from the carbons falling to
the ground.
In order to prevent the sparks being projected above the reflector I fit a glass

page_text: collar or ring above the luminous centre, and to prevent this collar or ring breaking
from the action of the heat I slit it at one side so that it can dilate.
Dated this 12th day of September 1891.
J. C. MEWBURN.
COMPLETE SPECIFICATION.
Improvements in Electric Lighting and in the Means therefor.
A communication from abroad by PAUL SEE, of 15, Rue d'Amiens, Lille, France,
Engineer.
I, JOHN CLAYTON MEWBURN of 55 and 56 Chancery Lane, in the County of
Middlesex, Chartered Patent Agent, do hereby declare the nature of this inven
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
This invention has reference to electric lighting by means of are lamps and its
chief object is to spread the light more uniformly over the room or space to be
lighted.
The invention consists in the combination with the carbons or pencils between
which the voltaic arc is produced of an inverted reflector of curvilinear form
placed around the arc so as to reflect the rays against the ceiling or against a
reflecting screen above from which the rays are again reflected downwards and
outwards over a large radius; also in the combination with the said carbons and
the said inverted reflector of a reflecting screen situated above the arc for the
purpose of reflecting the rays downwards and outwards, the said reflecting screen
being in some cases made capable of folding when not in use; also in the combina-
tion with the said carbons and the said inverted reflector of a collar, ring or globe
of glass or other suitable material such as mica above or around the voltaic arc or
point of combustion in order to prevent the projection of sparks over the top of the
inverted reflector.
In the accompanying drawings,
Figure 1 represents in elevation partly sectional the preferred form of apparatus
for carrying out my invention, the reflecting screen being in position for use.
Figure 2 is the same as Figure 1 except that the reflecting screen is folded up as
when not required for use.
Figure 3 is a similar view to Figure 1 but showing a different construction of
fold-up reflecting screen.
Figure 4 is a similar view but showing a reflecting screen that does not fold.
Figure 5 is a similar view but without a reflecting screen, the ceiling-serving as
the reflector.
Referring first to Figures 1 and 2, a is the positive and the negative carbon
or pencil. As it is important that the luminous point or arc should always be in
the same position the two carbons should in order to attain this result either be
given suitable diameters or sectional thicknesses relatively to each other so as to
burn at the same speed as is well understood or the mechanism of the lamp-should
be arranged in any of the well known manners so as to feed one carbon more
quickly than the other. The positive hollow carbon is preferably placed below
the pointed negative carbon as shown so that the luminous rays shall be thrown
towards the reflecting screen above (or towards the 'ceiling) without being
obstructed. c is the box containing the lamp mechanism of ordinary 'construction
and situated below the are so as not to throw a shadow above. dis an inverted
curvilinear reflector placed around the arc. Its curve should be such that some of
the rays which it reflects 'will be thrown to a great distance from the lamp as
indicated by the lines . In this way the diminution in the 'intensity of the light
by distance is compensated for by the increase in the number of: rays reflected.
Thus the part of the reflecting screen (or of the ceiling) directly above the lamp
receives the shortest rays but the reflector d reflects very few rays upon this part

page_text: whilst the parts of the reflecting screen (or of the ceiling) which are furthest from
the lamp receive a greater number of luminous rays; the lighting of a large surface
of the reflecting screen (or ceiling) is thus in a manner regulated. e is the
reflecting screen placed horizontally at a suitable distance above the lamp. This
screen is only essential when the ceiling is so high that lighting by means of rays
reflected from the ceiling is not advantageous in consequence of the loss of intensity
in the light by reason of the square of the distance, or when (as in Figure 4) the
ceiling is not flat or horizontal."
As the screen e Figure I may be in the way in the day time it is preferably
constructed so as to fold up. With this object I make it in two parts hinged at f
and I connect to each part a cord g g these cords passing over a roller hand being
attached at their other ends to a counterpoise i. When it is required to fold up
the screen the counterpoise i is lowered and the screen then takes up the position
seen in Figure 2. The lamp itself has a counterpoise k. is a glass or mica globe
around the voltaic arc or point of combustion to prevent the projection of sparks
over the top of the reflector d; instead of the globe l, a collar or ring, being
practically the upper half or portion of the globe, may be employed, the lower
part of the reflector itself arrests all sparks falling direct toward the ground.
Figure 3 represents the same arrangement as Figures 1 and 2 except that the
reflecting screen e is made in several parts jointed together so as to be capable of
folding up into a zig-zag or bellows form as indicated in dotted lines. Figure 4.
shows a non-folding reflecting screen and Figure 5 the application of my invention
in cases where the ceiling serves as a reflector. m represents the ceiling.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me and in what manner the same is to be performed, I
declare that what I claim is :-
1. In electric lighting by means of arc lamps, the combination with the carbons
or pencils between which the arc is produced of an inverted reflector of curvilinear
form placed around the arc, substantially as and for the purpose set forth.
2. In electric lighting by means of arc lamps, the combination with the carbons
or pencils between which the arc is produced and with an inverted reflector of
curvilinear form placed around the arc as described, of a reflecting screen
situated above the arc, substantially as and for the purpose set forth.
3. In electric lighting by means of arc lamps, the combination with the carbons
or pencils between which the arc is produced and with an inverted reflector of
curvilinear form placed around the arc as described, of a reflecting screen
situated above the arc, the said screen being arranged to fold up when not
required for use, substantially as set forth.
4. In electric lighting by means of arc lamps, the combination with the carbons
or pencils between which the arc is produced and with an inverted reflector of
curvilinear form placed around the arc as described and adapted to arrest all
sparks falling direct towards the ground, of a glass or mica globe, collar or ring
around or above the said arc to prevent the projection of sparks over the top of
the said reflector, substantially as set forth.
5. The means herein before described and represented in the accompanying
drawings for electric lighting by arc lamps.
Dated this 17th day of Ma 1900
J. C. MEWBURN.