Year: 1888

page_text: Date of Application, 22nd May, 1888
Specification Accepted, 14th Sept., 1888
ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E. 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:
The reflectors used up to the present time on land and sea to throw a beam of light
in a given direction: (the light being produced by an electric are light or incandescent
lamp or any other generator of light, but principally electric are lights which are used
the most) have the disadvantage that of the luminous sphere emitted only that cone
is utilized which has its apex in the focus and its base around the rim of the reflector ;
it is therefore evident that only one fifth of the light emitted by the focus is utilized
while the other four fifths are lost in the walls and fittings of the reflector by absorption
or useless reflection.
The object of the present invention is to utilize nearly the whole of the four fiftlis
which are lost in every reflector thus permitting a great reduction in the force
employed for the production of the light.
In the accompanying drawings:
Fig. 1 is a diagram of the system and the respective arrangements of the reflectors.
Fig. 2 represents the back of the reflector.
Fig. 3 is a vertical section showing the interior of the reflector.
Fig. 4 represents the same reflector with an arrangement to light the whole of the
horizon.
In Fig. 1a b c d is a parabolic reflector the focus of which is in fandegh lis a
hemispheric reflector the centre of which is also in f. These reflectors are so arranged
that the diameter el of the hemispheric reflector, the focus f and the line a d of the
parabolic reflector are in the same. plane.
All the rays of light included within the angles fa and c f d will because of the

page_text: parabolic form of the reflector be reflected parallel and the beam of light will be
represented by a hollow cylinder the outer lines of which are a a' and d d¹ and the
inner lines and e c¹ and this bean shall be called in the following specification the
"outer beam."
By examining the hemispheric reflector it will be seen that it gives a perfect
reflection and that all the rays of light within the angles e f g and fh will
be reflected on the surface of the parabolic reflector within the angles e fd and bf a
respectively thus serving to intensify the above described outer beam.
By further examining Fig. 1 it will be seen that up till now the whole luminous
sphere emitted from the focus is utilised with the exception of the cones which have
their apex in fand are within the angles bfe and gf. It is also evident that the
cone of light represented by 'fwould be reflected in a beam representing
a full cylinder filling the hollow of the "outer beam "if it was not for the
interposition of the hemispheric reflector, the same would take place with the cone of
light fg h.
of
For the purpose of also utilising this quantity of light and seeing that the cone of
light gis perfectly useless for the production of the "outer beam" the part
the hemispheric reflector is cut out. Thus the cone of light f g h passes unreflected
through this opening and if now the party of the parabolic reflector is replaced
by a spheric part be struck from the centre f the rays reflected from this would
mingle with and intensify the cone fg h. This would form a diverging beam but by
inserting for instance a biconvex lens- having its focus in this diverging beam
would be transformed into a cylindrical one which shall be called the "inner beam"
and fills the dark hollow of the "outer beam."
From the foregoing it is evident that theoretically not a single ray is lost, with
the exception of the small quantity intercepted by the carbons producing the
light, but this is reduced to a minimum by the peculiar arrangement of the carbons in
this app.atus.
In the reflectors used up to the present time the carbons and carbon holders are
mounted vertically forming a certain angle with the vertical line, for the reason it
appears that the maximum intensity of light emitted by the arc is always in a cone
the sides of which form an angle of about 40° to 50° with the horizontal line. In
this apparatus the carbons are mounted horizontally in the centre line m n and thus
the cone of maximum intensity will fall on the efficacious part of the reflector. The
positive carbon is mounted opposite the parabolic reflector.
This arrangements of the carbon holders in itself suffices to increase the efficiency
of the reflector but in combination with the two reflectors described above it is still
further increased especially as the shadow thrown by the carbons falls in the least
efficient part of the sphere of light i.e., the "inner beam." This arrangement of the
carbons further facilitates the crossing of the rays through the focus, mentioned above
and the carbon holders and fittings are arranged in the cylinder representing the
"inner beam." Thus the quantity of light intercepted by the carbons is reduced to a
minimum and is half of that intercepted by vertical carbons.
The carbon holders and mechanism for operating them are represented in
Figs. 2 and 3. To intercept the least possible light the support and mechanism
for operating the negative carbon N is placed at the back of the reflector A which is
formed with a central opening just large enough to let the carbon and the carbon
holder pass. This carbon holder is as represented in the drawings attached to a
mechanism permitting the adjustment of the negative carbon and consequently the
adjustment of the arc.
The movement of the positive carbon P is simultaneous with that of the negative
carbon and is effected by the mechanism represented in the drawings.
The positive carbon passes through an opening formed in the above mentioned
lens of the hemispheric reflector. This lens may also be omitted as the diverging
rays would serve to lighten up the shadow thrown by the carbons in the "inner
beam.".
The mechanism is constructed in such a manner that the rate of advance of

page_text: the positive carbon is twice that of the negative because of the positive carbon
being consumed twice as quick as the negative and thus the are always remains
adjusted in the focus; a point which very often has been neglected up to the present.
If it is desired to produce a diverging beam so as to extend the lighted space it
is only necessary to remove the are from the focus of the parabolic reflector in the
direction of its axis, and for this purpose the mechanism for moving the negative.
carbon holder is provided with a second hollow screw V which is traversed longitu-
dinally by the screw B and by which the position of the negative carbon can be
altered independently of the simultaneous movement with the positive carbon.
The arrangement of the electric contacts and of the insulators need not be described
as it is of the usual form.
To prevent the reflectors from being distorted by the heat produced by the
are strengthened at the back with radial ribs.
arc, they
The hemispheric reflector is held in position by the frame D which also carries the
positive carbon holder and is as thin as possible to intercept as little light as possible.
The position of this hemispheric reflector is slightly adjustable so as to permit the
proper adjustment of the focus.
The whole apparatus is journalled in a stand F the axis through the journals T going
through the centre of gravity of the apparatus which can be turned completely round
this axis.
The above described arrangements are not the only ones which render this apparatus
new in all its parts and useful in many instances such as for war-ships and fortifications
in time of war or for vessels of any description wanting to enter a port during the
night. As it is often necessary to light the greatest part of the horizon simultaneously
a supplementary reflector may be used with the above described apparatus, which will
light simultaneously the whole horizon if desired.
Supposing the parabolic reflector is turned in its stand until its axis stands vertical
as represented in Fig. 4 the beam of light will be reflected towards the zenith, but if
this beam is intercepted by a conical reflector R the sides of which form an angle
of 45° with the horizontal line this cylindrical beam of light will be converted into a
disc of light, lighting up the whole horizon.
The immense advantages and various applications of this arrangement are easily
understood especially as regards war-ships and the merchant navy; a war-ship provided
with several reflectors throwing parallel beams may be surprised by a torpedo boat
while another side is being searched with the reflectors, while with the disc of light
thrown by the supplementary reflector the whole horizon is lighted and all enemies
can be watched simultaneously.
The mechanical arrangement is very simple, a hollow cone R of the above mentioned
angle, provided with the necessary strengthening ribs to prevent distortion, is placed
with its apex towards the interior of the reflector, the axis of both in the same line.
The base of the cone has the same diameter as the reflector A. Three thin equidistant
rods C are attached to the base of the cone and to the other end of these rods is
fastened a ring H formed with several notches which engage like a bayonet joint with
corresponding catches on the outer rim of the reflector. It will easily be understood
now how easy it will be to adjust or remove the conical reflector for transforming the
cylindrical beam into a disc of light or vice versa.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is :-
1. In apparatus for reflecting light the employment of two reflectors as described
above for intensifying the reflected light and utilising the whole of the sphere of light
or at least only losing the least efficacious parts of the sphere; these reflectors can be,
one parabolical and the other spherical or of any other curves giving the same result,
and the parabolic reflector may have a parabolic apex or the least efficacious part may
be replaced as described above by a spherical part and a lens may be used to convert

page_text: the rays of the "inner beam" into parallel rays or the lens may be omitted and the
diverging rays utilised the reflectors being of any desired diameter.
2. The manufacture and application of these reflectors which may be of glass or
crystal suitably "silvered" or which may be of metal, polished, silvered or nickeled
or covered with another metal which would reflect the light, and the reflectors may or
may not be provided with strengthening parts, to prevent their distortion, and which
may be or may not be formed in one piece with the reflector.
3. The use of one or more.lenses which completely cover the opening of the spheric
reflector for the purpose of utilising the "inner beam of light.
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4. The above described mechanism so constructed as to intercept the least possible
quantity of light and to render the adjustment of the carbons more easy.
5. The employment of this light reflector on sea or land for military service or
other, public or private, also for submarine craft, balloons, light-houses and
the like..
6. The employment with these reflectors or those of any other system, of a supple
mentary reflector which serves to convert the beam of light ordinarily produced by
the reflectors into a radial, flat or conical beam which projects the light in every
direction this supplementary reflector may be conical or of any other form permitting
to disperse the rays in the most convenient forms and directions which may be either
all round the apparatus or on a smaller or larger part of the horizon, and this reflector
may be of any suitable material, metallic or not, and manufactured in any manner,
also the system of mounting and adjusting it on the reflectors may be of any
suitable kind.
The exclusive right of using these supplementary reflectors is reserved, not only in
war-time but also at the entrance to harbours in straits, canals and the like during the
night.