Improvements in Apparatus for the Projection of Electrio or other Light.
Year: 1891

page_text: Date of Application, 9th Dec., 1891-Accepted, 12th Mar 1892
COMPLETE SPECIFICATION.
Improvements in Apparatus for the Projection of Electrio or other
Light.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by Messrs. Sautter. Harlé and Company, of 26 Avenue
Suffren, Paris, in the Republic of France,) 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 use of projectors for the defence of ships has shown the advantages there
would be in adapting these apparatus, in a more rational manner, to the different
uses which they are called upon to fulfil.
For distant objects search projectors are used, giving to the beam the maximum
of concentration and placed at a certain distance above the sea.
For the near defence of ships, principally at anchor or hove to, when torpedo
attacks are to be feared. a class of projectors has been designed called port-hole..
projectors, which furnish a beam spread out horizontally. In this way ships may
be surrounded with a continuous luniinous zone.
The horizontal divergence of the beam is obtained in these apparatus by means
of an optical spreader formed of a series of lenses placed in front of the light,
reflector.
After its passage through these lenses, the conical beam, of small"
angular divergence, about 2 degrees, spreads out into a horizontal band extending
over say 12 to 15 degrees.
In order to surround the vessel with a continuous zone, without leaving a dead
angle between adjacent beams it is necessary either to increase the number of
projectors, or give to the lenticular spreader such large dimensions as involve great
difficulties of construction and considerable loss of light.
This invention. aims. at obtaining the continuous zone by means of a novel
arrangement of projector, having great horizontal divergence, whilst preserving to
the beam a luminous intensity independent of the divergence, whence the name
adopted for this novel apparatus the divergent aplanetic projector.
The apparatus is shown in the annexed drawing in which-
Figure 1 is a vertical section of the apparatus on the line Y Y of Figure 2.
Figure 2 is a horizontal section on the line X X of Figure 1.
Figure 3 is a vertical section on the line Z Z of Figure 2.
it is
M is a mirror of glass cut to a special form and silvered upon its back face;
held in a metallic mounting m, forming a curved frame fixed by wood or metal
strips cc, upon the two foundation plates of the apparatus.
T is a cylindrical sheet iron drum, held between the angle pieces t₁t. Upon
these angle pieces are rivetted the upper and lower foundation plates t" and ".
At the front of the apparatus the drum is cut away and replaced by a hinged
door formed of a metal frame P in which a glass P* is fixed. A button p with a
latch keeps this door shut whilst in use.
In the upper foundation plate t" an opening, t" is formed for the outlet of the
heated air. It is covered with a metallic cover t". The lower foundation
plate " is also formed with an opening t" and a cover t".
On the side of the projector a shutter R is placed sliding in a groove R' in such
a manner as to allow of the hand being placed inside the apparatus.
A spyglass for observing the carbons is placed in the axis of the projector, it
passes through the drum T and receives the rays from the luminous crater. These
rays pass through the mirror in the axis of the apparatus where a small unsilvered
surface is. left.

page_text: A second spy glass ' gives at right angles the image of the crater; it is placed
on the vertical axis in the lower foundation plate. A screen moved by a
button el protects it from the fall of particles of ignited carbon. A totally
reflecting prism e" sends the image to the operator.
The horizontal carbon electric lamp L, is mounted upon a slide 1.
V is a head which controls the threaded rods V' V". This gives to and fro
movement to the slide in such a way as to bring the luminous source into the focal
plane.
These rods, whose threads are opposite in direction and of different pitch, by
their movement cause the carbon holders V, V" and consequently the carbon
pencils VV to advance.
B B are buttons regulating the position of the carbons.
Automatic action of the lamp is obtained by means of mechanism placed in the
case L and not shown in the figure.
The head V encloses a second head, not shown in the figure, which gives to the
lamp a movement of rotation around its vertical axis and thus brings the luminous
crater to the focus F.
The whole projector is supported by a six branched fork S bolted to the piece t¹.
It carries at its centre a pin i which engages in a socket fixed on a bearer S'.
This latter is attached to a slide formed of a cross bar S" and two axes S" on
which rollers SIV turn and they run on a guide way Sv.
The projector can thus oscillate freely in all directions.
Path of the luminous rays. The outline of the mirror in vertical section
Figure 1, is calculated to prevent spherical aberration of the rays emanating from
the point F.
..
To obtain this property it is sufficient to take as limit of the profile, two circles
whose radii are in a given relation, as originally shown by Colonel Mangin.
If this profile he rotated about a vertical axis passing through F, the surface of
revolution thus formed will have at all points, the property of producing a reflected
pencil passing through the vertical axis at F and whose rays will be parallel to the
horizontal plane.
There is thus obtained a luminous band the height of which is a minimum and
the breadth depends only on the horizontal aperture of the mirror. The intensity
at each point of the illuminated band, is dependent on the focal distance and the
power of the source, but it is independent of the angular opening of the mirror.
The mirror shown in the drawings possesses a divergence of 120° in a horizontal
plane and gives a maximum concentration in the vertical plane, aberration being
rigorously suppressed.
One may however obtain any divergence desired by limiting the mirror to the
horizontal opening.
The rays no longer having to traverse the lenticular spreader, the important loss
of light caused by the thickness of the glass is avoided. The circular shape of the
glass door P allows the rays to traverse it normally.
The electric lamp L has its carbons horizontal, the axis of the carbons is inclined
at about 30° to the horizontal axis of the projector. This arrangement is necessary
on account of the path of the rays, which being emitted at the point F, are all
directed after reflection on the mirror, to intersect on the vertical axis of the focus.
If then the lamp were placed vertically or in an inclined position, it would eclipse
all or a great proportion of the rays.
The arrangement of the lamp is that of a mixed lamp able to work either
automatically or by hand; but the projector may be illuminated by any other kind
of electric lamp or by a luminous source of any kind.
Working of the apparatus. As soon as the lamp is got to work the exact
position of the crater is regulated by means of the two spy glasses land l', the
heads V V and the buttons B' B'. The luminous source is thus brought exactly
to the height suitable to the point F.
The projector being placed in the lower part of the ship to constantly illumine

page_text: the surface of the sea, it is desirable to suspend it in such a manner as to counteract
the influence of the rolling and pitching movement.
The free suspension S S' is well suited for this purpose and always brings the
beam back into the plane of the horizon. The eyes W W nevertheless allow the
apparatus to be if necessary immovably fixed.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The combination with a projector of electric or other light, of a divergent
aplanetic reflector of glass or other material, producing a luminous beam without
spherical aberration and which may have any desired horizontal divergence, the
luminous intensity being independent of this divergence.
2. The apparatus described and shown applicable to the luminous defence of
ships, to the lighting of coasts, channels and fortresses, and to guide lights, all
aubstantially as described and shown by the annexed drawing.
Dated this 9th day of December 1891.
CARPMAEL & Co.,
Agents for the Applicant.