Improvements in Electric Incandescent Lamps.
Year: 1895

page_text: Date of Application, 3rd Dec., 1895
Complete Specification Loft
5th Oct
1006 Anerated
Dent Al...
1000
PROVISIONAL SPECIFICATION.
Improvements in Electric Incandescent Lamps.
We, HENRY FRANCIS JOEL of 31 Wilson Street, Finsbury in the County of
London, Electrical Engineer, and FERDINAND FANTA, of 1 Arundel Street,
Strand, in the County of London, Consulting Engineer, do hereby declare the
nature of this invention to be as follows:-
This invention relates to that class of electric incandescent lamps in which a part
of the bulb is either plated or otherwise provided with a metallic coating for the
purpose of transforming such coated part of the glass-bulb into a reflector
whereby, when the shape of the glass-bulb is appropriately designed for reflection,
the greater efficiency of the lamp is obtained owing to the light being directed
on the particular object or for the purpose for which it it desired to utilise
same.
It is obvious that, in order to obtain the highest degree of useful effect in
respect of either concentration or of diffusion, as the case may be (according to the
form or shape given to the reflecting surface or mirror part of the bulb), it is
essential to provide means by which the main body of the luminous filament can be
made to correspond, as nearly as is possible in practice, with the theoretically
correct optical focus of the reflecting surface or mirror and to prevent, as far as
possible, any other part of the filament not in the true optical focus from acting on
the reflector so as to confuse the direct light and true reflection.
In electric incandescent lamps which have so far been described, designed and
manufactured with part-plated surfaces or with metallic coatings of part of the
surface of the bulb, whether of the ordinary pear-shaped, spherical or other forms
especially designed for specific purposes, neither of the above mentioned desiderata
have been taken into consideration with the result that the luminousity of the
filament is not utilised to its full extent, that a double image is produced on the
mirror and that moreover, owing to the direct light from and also the reflection of
the two uprights or in- and outlet branches of such filament by the mirror,
brighter rays are produced than those reflected from the main portion of the
filament from the mirror, generally, whereby reflected images, bright lines and
shades are shewn on the surfaces or objects on which the light is thrown.
The object of this invention is to obviate these inconveniences and for this
purpose we construct the incandescent filament according to the form or
geometrical conformation of the reflecting surface or mirror giving to such
filament in each individual case such form or shape as is most appropriate for the
specific shape or design of the reflecting surface and in such a manner, always, as
to take, as center of figure of such filament, the optically correct focus of the said
mirror. We are moreover careful to shape the filament in such a manner as to
present similar lengths of luminous parts to corresponding portions on the circum-
ference of the mirror and generally to make its focus coincide with the center of
figure of the body of the filament.
In order to avoid the reflection from the straight portions of the filament (in- and
out- branches) we either prevent the incandescence until we reach the bulk of the
filament or else so arrange same, in respect of the bulk of the filament, that they
are hidden from sight when looking at the mirror from the spectator's side, so that
the reflection from these branches is immersed or so to say covered by that of the
body or bulk of the glowing filament.

page_text: Thus, according to this invention, the filament, in an electric incandescent lamp
in which the reflecting surface or mirror is of a conical shape, would be helical the
spirals of such helix being kept or formed within the plane of a cone so that the
intersecting points of the different spires with the plane passing through the axis
of the mirror would, if joined together, form an inverted A, the in- and outlet
leads coming to the summit and from the center of the basis of the cone,
respectively.
In the case of a semi-spherical mirror, for instance, the helical spires would
be within the plane of a semi-sphere so that the intersections of same with a
plane passing through the axis of the mirror would all be located on a semi-
circle.
In some cases or instances it may be desirable to so wind or shape the filament
as to give it a more complicated form but as a rule the spires of the filament
should intersect the plane passing through the axis of the lamp in such a manner
that the points of intersection, if joined together, represent a line or diagram
symetrical of that of the intersecting line of the reflecting surface with the said
plane.
In some instances the filament may be helically wound or twisted, all the spires
being in a same plane at right angle with that passing through the axis of the
reflector and the body of the filament should be kept within the reflector, that is
inside the plane passing through the outer edge of the reflector so as to obtain the
utmost efficiency and so as to avoid the glare of the filament outside the reflector
and so as to prevent such filament being seen when the lamp is looked at from
the side.
In this manner, when the lamp is seen from the side or from the back (such as
is the case for the lighting of ceilings in picture galleries, libraries etc. etc.), the
filament cannot be seen at all whereas even if looked at from the open or wide side
or portion of the reflector such filament is hardly distinguishable owing to the
reflection of same in the mirror.
The shape of the reflecting portion of the lamp is of great importance and in
order to use the light to the best advantage we make this reflecting portion of a
true geometrical figure or combination of figures either conical, spherical or
otherwise, a convex shape for diffusing the light, concave for converging the light
and increasing its power in one direction, or parabolic for parallel rays, or
spherical or flattened or as may be required for special purposes and uses, and we
so arrange the shape of the clear portion of the glass of the lamp bulb that the
rays of light from the filament and the reflecting surface may pass through the
glass as nearly as possible at right angles to the plane of the surface of the glass,
that is directly through the glass at its point of least refraction or resistance to the
rays of light.
The reflecting portion of the lamp may be at the top, or at the bottom, or at the
side, or at an angle, or at any part of the glass bulb and may cover any portion of
the glass bulb as may be suitable for special purposes and the clear glass be
arranged to correspond thereto but in any case the in- and outlet branches should
be kept between the summit and the basis of the reflecting surface and the body of
the filament should also be kept within the plane passing through the outer edge or
wide part of the reflecting mirror.
The clear glass may also be afterwards frosted or obscured or coloured for
special purposes and a special feature of this invention is to so frost, obscure or
colour in the most appropriate manner, according to the uses to which the lamps
may be put, only the small portion of the clear glass which is occupied by or
immediately around the button and uneven part of the bulb which is the result of
the sealing or blowing of same, in contradistinction with the frosting or otherwise
obscuring of the whole or of the larger portion of the clear glass which has been
done heretofore.
Instead of silver-plating the reflecting portion of the bulb with bright silver as
has been done heretofore, whereby a dazzling glare is obtained we, according to

page_text: this invention, sometimes dull-silver, or gild, or whiten, or otherwise treat the
reflecting surface or we may apply an outside cover such as a metal reflector to fit
over the special shaped part of the glass bulb, such reflector may be tinfoil, or
copper, or any other material found suitable for reflecting purposes.
London, this Second day of December 1895 (One thousand eight hundred and
ninety-five).
We, HENRY FRANCIS JOEL of 31 Wilson Street, Finsbury in the County of
London Electrical Engineer, and FERDINAND FANTA of 1 Arundel Street, Strand,
in the County of London, Consulting Engineer, do hereby declare the nature of
this invention, and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
This invention relates to that class of incandescent electric lamps in which a
part of the bulb is either plated or otherwise provided with a metallic coating for
the purpose of transforming such coated part of the glass bulb into a reflector,
whereby, when the shape of the glass bulb is appropriately designed for reflection,
the greater efficiency of the lamp is obtained, owing to the light being directed
with the greatest uniformity and least loss of light on the particular object which
it is desired to illuminate.
It is obvious that in order to obtain the highest degree of useful effect in respect
of either concentration or of uniform diffusion, as the case may be, (according to
the form or shape given to the reflecting surface of the bulb) it is essential to
provide means by which the axis of the main body of the luminous filament can
be made to correspond gr pass through, as nearly as is possiable in practice, with
the theoretically correct optical focus of the reflecting surface or mirror and to
prevent, as far as possiable, any other part of the filament not in the true optical
focus, from confusing the main body of light and its uniform reflection, and this
object has been found in practice to be most nearly fulfilled when the body of the
filament lies substantially in a surface parallel to and equidistant from the said
reflector.
In electric incandescent lamps which have so far been described, designed, and
manufactured with part-plated surfaces, or with metallic coatings upon part of the
surface of the bulb, whether of the ordinary pear-shaped, spherical, or other forms,
especially designed for specific purposes, neither of the above mentioned considerata
have been taken into account with the result that the luminosity of the filament is
not utilised to its full extent that a double or multiple image is produced on the
illuminated surface; and, that, moreover, owing to the direct light from and also
to the brighter reflection of the two in- and out-let branches of such filiament by the
mirror, bright lines and shades are shown on the surfaces, or object on which
the light is thrown. This defect has been dealt with by the partial obscuring
of the glass opposite to the reflector but with the consequent considerable loss
of light.
The object of this invention is to obviate these inconveniences, without loss of
light, and for this purpose we construct the incandescent filament, so as substantially
to lie in a surface coaxial with and parallel to the form or geometric conformation
of the reflecting surface or mirror, giving to such filament in each individual case
such form or shape as is most appropriate for the specific shape or design of
reflecting surface.
We are moreover careful to shape the filament in such a manner as to lie

page_text: substantially in a surface co-axial with and equidistant from that of the reflecting
surface, and generally to make the focus of the mirror the geometrical centre of
the body of the filament.
In order to avoid the reflection of the straight portions of the filament (in and
out branches) we either prevent the incandesence until we reach the body of the
filament, or else so arrange same in respect of the body of the incandescent filament,
that it is hidden from sight when looking at the reflecting part or mirror from the
spectators side, so that the reflection from these branches is immersed in, or so to
say, covered by that of the body or bulk of the filament.
Thus according to this invention, in an electric incandescent lamp, in which the
reflecting surface or mirror is of a conical shape, the filament would be helical, the
spirals of such helix being kept or formed within the plane of the cone, so that
the intersecting points of the different spires with the vertical plane passing through
the axis of the mirror would, if joined together, form an inverted V, the in and
outlet leads coming to the summit, and from the centre of the base of the cone
respectively.
In the case of a semi-spherical mirror for instance, the helical spire would lie
substantially on the surface of a semisphere, so that the intersections of same,
with a plane, passing through the axis of the mirror, would all be located on a
semicircle.
In some cases or instances it may be desirable to so wind or shape the filament
as to give it a more complicated form, but as a rule, the spires of the filament
should intersect the plane passing through the axis of the lamp in such a manner,
that the points of intersection, if joined together, represent a line or diagram
co-axial with and equidistant from that of the intersecting line of the reflecting
surface with the said plane, and this object can also be attained in some
degree by making a ball shaped filament, in which the intersecting line of
the surface would form a sphere, and correspond if desired to the curve of the
reflector.
The shape of the reflector portion of the lamps is of great importance, and in
order to use the light to the best advantage, we make this reflecting portion of a
true, geometrical and optically correct shape, either conical, spherical, or a
combination of spherical and convex or concave curves, a convex shape for
diffusing the light concave for converging the light and increasing its power in
one direction, or parabolic for parallel rays, or spherical or elliptical, or as may be
required for special purposes and uses, and we so construct and form the clear
portion of the glass of the lamp bulb that the rays of light from the filament, and
the reflecting surface, may pass through the glass as nearly as possible at right
angles to the plane of the surface of the glass, that is, directly through the glass
at the shortest intervening space, and at its point of least refraction, and with
least loss of light.
The reflecting portion of the lamp may be at the top, or at the bottom, or at the
side, or at an angle, or at any part of the glass bulb, or may cover any portion of
the glass bulb, as may be suitable for special purposes; and the clear glass may
be arranged to correspond thereto; but in any case the in and outlet branches,
where incandescent, should be kept between the summit and the base of the
reflecting surface, and the body of the filament should also be kept within the
plane passing through the outer edges or wide part of the reflecting mirror, and
the mirror itself.
It is advantageons to so frost obscure or colour in the most appropriate manner,
according to the uses to which the lamps may be put, only a circular space covering
the centre of that part of the bulb opposite to the reflector which is uneven or
distorted by the process of scaling off the glass after exhausting the air, in contra-
distinction to the frosting, or otherwise obscuring of the whole, or of the larger
portions of the clear glass, which has been done heretofore.
Instead of silver plating, the reflecting portion of the bulb with bright silver, as
has been done heretofore, whereby a dazzling glare is obtained, we, according to

page_text: this invention, dull silver or frost-silver, or dull gild, or treat with tin or such metal,
or otherwise prepare the reflecting surface, and we find that with reflectors so
made, the objectionable reflection of the bright lines or bright spots, is obviated,
and a diffused and softened combined, direct, and reflected light, is obtained.
In the accompanying drawing similar letters denote corresponding parts in all
the figures, and the figures are drawn somewhat as diagrams in order to show the
filaments and the reflecting portions more clearly, the filaments and the globes
being in sectional elevation, whilst the caps through which the filament connections
pass are in elevation and in some instances a plan of the filament is shown.
Figure 1 represents a ball or spherically shaped incandescent electric lamp bulb,
in which the top part R is silvered or otherwise transformed into a reflecting
surface, whilst the opposite part C is of clear glass.
The filament F is so shaped that the several spirals or helices are all situated in
a semisphere, shown by the dotted outline, concentric to that of the reflector R,
and the main body of the filament is made, to hide the inlet and outlet branches ff'.
A plan of the filament used in the lamp shewn in Figure 1 is under the lamp at
the right side.
In all cases it is essential that the filament F should be so constructed that the
inlet and outlet supports, legs or connections, should be effectually covered when
looked at from a position directly facing the reflecting surface and for this purpose
the filament F as in Figure 1 and in other figures, made with an extended surface
at its end furthest from the connections.
Figure 2 represents an incandescent reflecting lamp of an elliptical shape and
this form of lamp gives a more extended range of reflected light than the purely
spherical lamp shewn in Figure 1 the filament in this case also follows the curve
of the lamp as shewn by the dotted lines.
Figure 3 shews an incandescent lamp of a conical form made as far as is
practically possible with flat reflecting surface, it being always necessary that the
form of the lamp should be capable of withstanding the pressure of the atmosphere
and for that purpose only it is necessary to round the angles of the bulbs. The
filament in this lamp is made to follow the cone of the reflector and a dotted line
joining the extremities or edges of the concentric helices would form a cone with
the base in the centre or on the plane passing through the edges of the reflecting
surface, and the apex nearest the cap of the lamp. In this lamp the area of
illumination is still more extended than in either Figure 1 or Figure 2, and as
shown by the dotted straight lines with arrows, the reflected light passes through
the clear glass C, at the least distance from the reflector, and almost at right angles
to the surface of the clear glass C and therefore at the point or surface where it
meets with the least resistance and least refraction, and it is another important
feature of this invention that in all the figures the reflecting portion and the clear
glass are especially designed and shaped to correspond one with the other in order
to obtain this very desirable object.
Figure 4 shows an incandescent lamp with a diverging or convex shaped reflector
and to some extent the opposite in shape to the cone or couvex shape shewn in
Fig. 3.
In this lamp the light is dispersed at a still wider angle, and such a lamp
is especially suitable for illuminating large areas.
Figure 5 represents a flat elliptical shaped lamp with the filament F of a
corrugated form placed concentrically to the reflecting surface and in a plane at
right angles to the axis of the lamp, such a lamp is especially suitable for stage
lighting or to act as a reflecting lamp placed against a wall etc.
Figure 6 shows a filament F applied to the same lamp as Figure 5 with a round
double loop and nearly flat filament, with the in and out supports taken right up
to the curve of the filament and made so as not to be incandescent.
Figures 9 and 11 show two alternative forms of a combined concave and convex
reflector. In these cases again the shape of the clear part or part opposite to the
reflecting part, specially shaped to allow the least resistance to the passage of
the light, and the least refraction to the rays of light as shown by the dotted lines

page_text: with arrow heads. The filaments shewn in the lamps, Figures 9 and 11. are
spiralled loop-shaped filaments. The filament in Figure 9 is a simple double loop,
shewn in plan under the lamp and is similar to an ordinary double loop filament,
but fixed horizontally, or at right angles to the axis of the reflector. A plan of the
spiral filament used in Figure 11, is also shewn under the lamp.
In some cases, of which Figure 7 (a front view) and Figure 8 (a side view) is an
example we prefer to give to the filament a ball or spherical shape, which provides
for the locating of the incandescent carbon, in what would be the surface of a
globe or ball, and this particular shape of filament is specially adaptable for lamps
of either ball shape or parabolic forms, and in such cases, the centre of the
imaginary ball shaped filament is made to correspond with the centre or focus of
the reflecting surface or mirror. Such a filament presents more extended surfaces
and lines of incandescent luminous carbon to the reflecting surface than an ordinary
loop shaped filament, and thus obtains a somewhat similar object to that attained
by the spiral concentric filament.
Figure 10 shows an incandescent lamp of a flattened or annular form, especially
designed for illuminating flat surfaces such as a billiard table or for pictures, with
a simple flat loop filament shewn in plan under the lamp figure.
Figure 12 is a lamp with a complex concave reflector specially designed for
dispersing the light at very divergent angles, and therefore suitable for such
purposes as street lighting, with the lower part partially frosted or obscured as
shewn by the shaded lines, the light immediately under the lamp is shaded, and
thus avoids the glare which a direct light would give, whilst at a short distance the
direct light from the filament can be seen, and also the reflected light from the
upper part of the lamp.
Figure 13 is a parabolic shaped reflecting lamp, with a compact spiral filament
placed in the optical focus, and with the clear glass part of the lamp also
specially shaped to oppose the least resistance to the part of the light, and to give
the least possible refraction. The direction of the rays of light are shown by the
dotted straight lines with arrow heads.
Figure 14 shows a cone shaped lamp with the spirals of the filament F.,
which if the edges were joined together would form, when incandescent, an
extended body of luminosity as shewn in the side view under the lamp; and. in
Figure 15 a lamp is shewn but with the reflecting surface on the lower part of the
lamp. This lamp, Figure 15, suspended by flexible wires, is especially suitable
for illuminating ceilings and so obtaining a very much softened and subdued lighting
effect.
The filament used in the lamps as aforementioned, can be made of any most
suitable material, and may be fastened in the usual manner. We, prefer, however,
in some cases, to have the in, and outlets of nonincandescent material, and in that
case, the beginning of the small spiral is secured by any of the well known means
to the inlet branch and the end of the outer or larger spiral is fastened to the
outlet branch, as shewn in Figures 1, 4, 5, 6, 9, 10, and 11. This facilitates, to a
great extent, the introduction of the carbon filament into the narrow neck of the
glass bulb, during the process of manufacture, and for sealing of same.
We are aware that filaments of different shapes have been manufactured
heretofore, and that double loops, cylindrical spirals, and U shaped carbons have
been utilised for incandescent, electric lamps, and we do not claim such forms
generally, but by our invention we provide for the shaping of such filaments in
combination with reflecting surfaces of specific geometrical forms, and we also
provide means of adapting in each case the shape of the filament to any such
particular geometrical form of reflecting surface, as may be most advantageous.
Having now particularly described and ascertained the nature of our inven-
tion. and in what manner the same is to be performed we declare that what
we claim is
1st. In an electric incandescent lamp, part of which is transformed into-and

page_text: utilized as a reflecting surface, constructing, forming or shaping the incandescent.
filament, in such a manner, that such filament other than the inlet and outlet leads
shall be placed so as to be substantially co-axial with and equidistant from the
reflecting surface.
2nd. In an electric incandescent lamp, the combination with a part of a globe
utilized as a reflecting surface, of an internal incandescent filament, so shaped and
located as to its inlet and outlet lead that the main body of the filament encloses.
and hides from sight the in and outlet branches of the same, where incandescent,
the whole being so arranged as not to interfere with the uniform reflection of the
body of the filament, substantially as described and illustrated.
3rd. In an electric incandescent lamp part of which is transformed into and
utilized as a symmetrical reflecting surface, the construction and formation of the
transparent parts of the glass bulbs relatively to the reflectors, so that the direct
light from the filament, and the reflected light passes through the glass as nearly
as possible at right angles to the surface of the glass, with the least refraction and
loss of light, substantially as described and shewn in Figures 2, 3, 4, 5, 9, 10, 11,
12, 13, 14, and 15.
4th. In incandescent electric lamps, the combination with an internal filament of
a dull reflecting metallic surface upon the glass, such as dull silvering, dull gilding,.
or treatment by lead, tin or other metal, so as to form or procure, a non-polished
reflecting surface upon the bulb to produce a uniform and diffused intensity of the
reflected rays, substantially as and for the purpose set forth.
Dated this 3rd day of October 1896.
FELL & JAMES,
1 Queen Victoria Street, London, E.C., Agents for the Applicants.