IMPROVEMENTS IN APPARATUS FOR PRODUCING PARALLEL AND DIVERGENT PENCILS OF LIGHT SUITABLE FOR SIGNALLING, LIGHT HOUSES, THE ILLUMINATION OF DISTANT OBJECTS, AND SUCH LIKE PURPOSES
Year: 1879

page_text: LETTERS PATENT to George Pitt, of Sutton, in the County of Surrey, for the
Invention of "IMPROVEMENTS IN APPARATUS FOR PRODUCING PARALLEL AND
DIVERGENT PENCILS OF LIGHT SUITABLE FOR SIGNALLING, LIGHT HOUSES,
THE ILLUMINATION OF DISTANT OBJECTS, AND SUCH LIKE PURPOSES." A com-
munication from abroad by Messrs. Mangin and Louis Sautter Lemonnier &
Co., of Paris, in the Republic of France.
Sealed the 31st October 1879, and dated the 25th August 1879.
PROVISIONAL SPECIFICATION left by the said George Pitt at the Office
of the Commissioners of Patents on the 25th August 1879.
GEORGE PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN
APPARATUS FOR PRODUCING PARALLEL AND DIVERGENT PENCILS OF LIGHT
SUITABLE FOR SIGNALLING, LIGHT HOUSES, THE ILLUMINATION OF DISTANT OBJECTS,
AND SUCH LIKE PURPOSES." [A communication from abroad by Messrs. Mangin
and Louis Sautter Lemonnier & Co., of Paris, in the Republic of France.]
This Invention has for its object improvements in apparatus for producing parallel
and divergent pencils of light suitable for signalling, light houses, the illumination
of distant objects, and such like purposes.
It is well known that parabolic surfaces have the property of reflecting in a
direction parallel to the axis of the parabola rays coming from a luminous point at
the focus.
Spherical surfaces have the same property for a luminous point on their axis at
a certain distance short of their centre of curvature when the chord of the spherical
reflector in question is small relatively to the radius of the sphere.
The property ceases when the chord is large relatively to the radius. The
reflected rays are no longer parallel, they form a pencil not cylindrical but
conical, with a greater or less angle at the apex, this is what is called spherical
aberration.
It is sometimes wanted to obtain cylindrical pencils of light not by parabolic
reflecting surfaces (which are difficult to obtain in practice) but by employing
spherical surfaces.
The first part of this Invention has for its object the construction of reflectors
with spherical surfaces, in which the spherical aberration of reflection is counter-
acted by the spherical aberration of refraction.

page_text: For this purpose the reflector is constructed of glass having two spherical
surfaces, the one concave and the other convex, whose radii are unequal. The
convex surface is silvered and serves as the reflector, the concave surface having a
smaller radius than the convex. The light in traversing the glass to reach the
reflecting surface, and in returning after having been reflected by it is caused to
deviate by refraction, and this deviation is accompanied by spherical aberration of
the contrary sort to that caused by the reflection at the spherical convex surface.
These aberrations annul one another, so that the result is the same as if the
reflecting surface were parabolic.
Having obtained a cylindrical pencil of light it may be necessary to give to it a
certain degree of divergence, either in all planes (thus making it a conical pencil)
or in the horizontal plane only. This result is usually obtained by placing plano-
cylindrical lenses across the pencil perpendicular to its axis, which spread it more
or less according to the radius of their cylindrical surface.
According to this Invention a divergence, which may be varied at pleasure, is
produced. This is done by making the dispersing apparatus not of one or of several
plano-cylindrical lenses but of systems of pairs of lenses, of which the one is plano-
convex and the other plano-concave. They are made in such manner that when
they are in contact they form a glass with parallel faces, which does not alter the
divergence of the pencil traversing them, whilst when they are more or less
separated a variable degree of divergence is obtained.
Another arrangement consists in placing between the luminous source and the
reflector a system composed of two lenses, whose form is such that when they are
in contact they produce no deviation, but when they are more or less separated a
variable deviation is obtained.
Various apparatus for sending light in one or several determined directions have
been constructed for marine, war-like, and light-house purposes. The second part
of this Invention consists in applying to these apparatus the reflectors and dis-
persers, above described, in place of the optical apparatus used up to the present time,
and in making the modifications of detail in the mechanical arrangements which
this substitution requires.
The object of the application is to obtain a more intense luminous pencil with
a given source, and at the same time to render the apparatus more portable and
convenient to use.
In cases where electric lamps have been employed the lamp or electric regulator
has been so arranged that the carbons are perpendicular to the axis of the light
directing apparatus. It has been found however that it is better to place this axis
obliquely to the axis of the light directing apparatus, an improvement which
permits the light to be better utilized. Either automatic or hand governed electric
lamps may be employed; the hand lamp.is so constructed that by the use of a
handle (distinct from that for approaching or separating the carbons) it is possible
without altering the distance of the carbons and without extinguishing the lamp
to raise or lower them at will. The rigid stem which serves to carry the carbon
holders, the screw for varying the distance, and the carbons themselves are all
placed in the same plane, or again the screw may be placed inside the guide stem.
It is also preferred to place behind the luminous focus a screen, constructed so
as to shut off the superfluous rays, which experience has shown to be injurious to
the successful directing of the light.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Pitt in the Great Seal Patent Office on the 25th February
1880.
"
IMPROVEMENTS IN
GEORGE PITT, of Sutton, in the County of Surrey.
APPARATUS FOR PRODUCING PARALLEL AND DIVERGENT PENCILS OF LIGHT
SUITABLE FOR SIGNALLING, LIGHT HOUSES, THE ILLUMINATION OF DISTANT OBJECTS,
AND SUCH LIKE PURPOSES." A communication from abroad by Messrs. Maugin
and Louis Sautter Lemonnier & Co., of Paris, in the Republic of France.
This Invention has for its object: 1. Certain optical arrangements adapted to
produce either a more complete parallelism of the rays emanating from a luminous
source by the combined effect of reflection and of refraction, or to produce a
constant dispersion of the luminous beam so obtained, or a dispersion which is
variable at will.
2. The application of these arrangements to apparatus either for signalling, or for
illuminating objects at long distances, or to light houses. Also certain arrange-
ments relative either to the directing apparatus or to the lamps placed at their focus
intended to attain these objects, in combination with the optical arrangements
above mentioned.
It is known that parabolic surfaces possess the property of reflecting in a direction
parallel to the axis of the parabola rays coming from a luminous point placed in
the focus of the parabola.
Spherical surfaces possess the same property for a luminous point, placed upon
their optical axis at a certain distance within the centre of curvature, when the
cord of the portion of the sphere considered is small as compared to the radius of
curvature. It ceases to be so when the portion of the sphere is large relatively to
the radius of curvature. The rays reflected are then no longer parallel, they form
a beam which is no longer cylindrical but conical with the angle more or less open.
This is what is called spherical aberration.
It is desirable to obtain a cylindrical luminous beam when using, not parabolic
reflecting surfaces which are difficult to obtain in practice, but spherical surfaces.
The first part of the Invention has for its object the construction of reflectors
with spherical surfaces, in which the spherical aberration of reflection is annulled
by a spherical aberration of refraction. With this object the reflectors are con-
structed of glass and formed with two spherical surfaces, of which the one is
concave and the other convex, and of these surfaces the radii are unequal. The
convex surface is silvered and serves as a reflector, the concave surface has a radius
of curvature smaller than that of the convex surface. In passing through the glass
to reach the silvered surface, and to return after reflection by it, the light is affected
by refraction, producing deviations which are accompanied by a spherical abor-
ration of an opposite nature to that which it experiences from reflection at the
convex spherical surface and which annuls its effects, so that the result is the same
as if the reflecting surface were parabolic.
The Figure 1 represents a glass reflector with spherical surfaces constructed
according to the principles which have just been enunciated.
A, silvered surface; B, transparent surface; F, luminous focus; a, a, a, a, dirèc-
tion of the luminous rays.
A cylindrical luminous beam being given, it may be necessary to give to this beam.
a certain divergence either in all planes (thus transforming it into a conical beam)
or in an horizontal plane only. This result has already been obtained by placing
in the course of the beam and perpendicular to its axis plano-cylindrical lenses,
which spread it out more or less according to the radius of curvature of the cylin
drical surface.

page_text: .!
Now means have been found to produce a divergence which is variable at will.
These means consist in composing the dispersing system, not as heretofore of one
or more plano-cylindrical lenses, but of two systems of lenses, of which the one are
plano convex and the other plano concave, so that when in contact they have the
samé effect as a glass with parallel faces, and produce no change in the divergence
of the beam which traversés them, whilst by separating them more or less a variable
divergence is obtained.
Figure 2 represents the optical arrangement, and Figure 2 bis the special
mechanism of a variable divergence disperser. In Figure 2, A, A, plano-cylindrical
convex lenses; B, B, plano-cylindrical concave lenses.
Figure 2 bis represents mechanism for varying the distances of the lenses; A,
the controlling pinion; B, fixed pane; C, moving pane; D, screw, producing the
movement of the moving pane; E, guides. When the lenses are in contact they
act as a glass with parallel faces and do not produce any dispersion. The dispersion
increases as they are separated the one from the other. The same result can also
be, obtained by placing lenses of the same form as those just described between the
Inminous source and the reflector.
Apparatus is required for various purposes, and especially for marine and military
uses, by which light can be projected in one or more required directions.
The second part of the Invention consists in the application in these apparatus of
the reflectors and dispersers above described, which are substituted for the optical
appliances now in use, and various modifications in detail arrising out of this change
which are made in the mechanical arrangements.
The object of this application is to obtain from a given source a more intense
luminous beam, and at the same time to render the apparatus more portable and
more convenient in use.
The Figures 3 and 4 represent a back view and a vertical section of a projector,
of which the mechanical arrangement is similar in some respects to those of the
lenticular projectors at present in use, but which differs from them in the substi-
tution of an aplanatic mirror of the system already described for the lenticular
pannel by which the rays are rendered parallel.
A, mirror; B, wooden chocks, which fix the mirror into its cast iron case; C,
unsilvered part, which allows the carbons of the electric lamp to be seen through
the black glass D; D, black glass let into the back of the projector; E, glass for
observing the carbons; F, door glazed either with ordinary glass or with divergent
lenses to open out the beam; G, door giving access to the buttons by which the
carbon carriers are adjusted; H, H, handles for moving the projector; J, locking
handle controlling the horizontal movement; I, locking handle controlling the
-vertical movement; K, contact makers for the negative pole; L, extremity of the
positive conductor; M, passage for the conducting cable; N, the conducting cable;
O, P, bronze rings insulated upon a wooden support; Q, R, spring contacts;
S, T, V, conductors; X, circuit breaker; Y, end of the positive conductor; Z, end
of the negative conductor; U, opening used in erecting the parts.
-
The hand lamp designed for projecting light over long distances is represented
by the Figures 3, 4, 3 bis and 4 bis, and is hereinafter described.
The Figures 5 and 6 represent a projector, having the same optical arrangement
as the preceding, but differing from it in certain mechanical features claimed as
forming part of the Invention; these consist,
1. In replacing the fixed cast iron pedestal by a pedestal consisting of a trellis
work of wrought iron A in the form of a hyperboloid of revolution, and which in
consequence of its form can be set up to different heights and even completely
folded for transport. This pedestal is surmounted by a wrought iron cap B¹ and a
turning carriage C¹.
2. In the mode of oscillation and suspension of the cylinder D of the projector
about two axes E, E. This movement is controlled by the tangent screw F
engaging with the toothed segment G; the Figures 7 and 8 represent a portable.
projector of small dimensions specially intended for steam launches.
.

page_text: A, A, forked support capable of turning about a vertical axis; B, copper cylinder
containing the reflector, the lamp, and a support for a divergent lense; C, the
electric lamp, here shown is hereinafter described; D, D, are handles used in moving
and working the cylinder.
This portable projector, which can be removed and replaced by hand and which
is specially applicable to steam launches, forms a part of the Invention.
The Figures 9 and 10 represent another arrangement of a portable projector
for a steam launch. In place of ¡being supported upon a foot the projector is sus-
pended from a sort of iron bow placed in the front of the launch, and to which it
is preferred to give the form represented in the Drawings. When it is not in use
it is laid down in the fore part of the launch; when it is in use the bow is raised
and maintained upright by hook stays. A is a ball and socket joint, and in
addition the suspending stirrup can turn around the axis D and the cylinder of
the projector around the trunnions C, C; these combined arrangements give to the
projector great mobility, and allow of the light being kept upon the objects to be
illuminated in spite of the movements of the launch.
The mode of suspension of the cylinder of the projector which has just been
described, as well as the special mode of erection on board a steam launch form
parts of the Invention.
There may be advantage in placing the projector at a certain distance from
the person who has to work it, and in such cases the movements which it has to
receive is transmitted to it either by means of water, or air under pressure, or by
means of electricity, or by means of other known.arrangements.
In the cases in which heretofore use has been made of the electric arc the lamps
or electric regulators have been arranged with their carbons perpendicular to the
axis of the projector. It has been found preferable to place this axis.obliquely
in relation to the axis of the projector, which permits of a better utilization of
the light being obtained, and according to this Invention it is so placed as the
Drawings show.
The electric lamps employed in these prejectors are either automatic or hand.
The hand lamp which has been devised is represented at Figure 3.
A', the
positive carbon and carbon holder; B', the negative carbon and carbon holder; C¹, Cu,
slides, to which the positive and negative carbon carriers are attached; D',
steel
screw, having at d¹ and at d¹ two screw threads of different speeds and in opposite
directions which pass through screwed holes in the slides C, C", so that by turning
this screw in one direction or the other the separation or approach of the slides
C', C, and of the carbons which they carry is effected; E' threaded sheath, which
can turn on the axis of the screw D₁ whilst it is retained in the same place longi-
tudinally by the two collars c, c¹; F, bevilled pinion into which the sheath E' is
screwed. The pinion F¹ is capable of turning freely without displacement in space,
being held by its neck in the fixed collar fl; G', bevilled pinion in gear with the
pinion F, and turned by hand by means of the axis and handle H; I', iron rod,
serving to guide in their movements to and from each other the slides C¹, C", and
the carbon carriers; K', screen or reflector, serving to shew the light to the observer
placed behind the lamp; L, hand wheel for working the screw D₁, producing the
separation or the approach of the carbons; M³, box of the lamp, it forms a foot ;
N₁, binding screw forming the connection for the negative current; O', plate
forming the positive connection.
The hand lamp, which has been devised for the projectors of steam launches, is
represented at Figure 8.
A', the positive carbon and carbon holder; B¹, the negative carbon and carbon
holder D¹, steel screw, having two threads of different speeds and of opposite
directions to effect the approach and separation of the carbons; E¹, screw socket,
in which the screw D¹ can turn freely, but which as it screws more or less into
the fixed socket F¹ produces a displacement of the screw D' and the two carbon
holders, and consequently a displacement of the luminous point; G¹, tube of

page_text: square section, serving for guiding the carbon carriers; H', box forming the foot
of the lamp.
There is claimed,-
First. The construction of a reflector of silvered glass with sperical surfaces
having different curvatures, and in which the spherical aberration due to reflection
is compensated by the spherical aberration due to the refraction.
Second. The employment, substantially as described, of the said reflector in the
construction of apparatus for prejecting light.
.
Third. The construction of variable divergence dispersers combining convex
cylindrical lenses with concave cylindrical lenses.
Fourth. The construction of variable divergence dispersers, substantially as
described and represented in the annexed Drawings.
Fifth. The modifications described in the mounting of apparatus for projecting
light, whether such apparatus be placed under the hand of the operator or be
worked from a distance by means of water or air under pressure of electricity, or
by other known means of transmission, these modifications consisting principally
in the employment of a pedestal of iron trellis in the form of an hyperboloid of
revolution; and in the new way in which the cylinder of the projector is suspended
and made to oscillate.
Sixth. The construction of the portable projector called a launch projector; the
suspension of the said projector and of projectors of larger size from a point above,
which replaces the pedestal at present in use; also the special mode described for
mounting the projectors of launches.
Seventh. The construction, with a view to the better utilization of the electric
light in projectors, of lamps (either automatic or hand) with inclined carbons.
Eighth. The construction described of hand electric lamps.
In witness whereof, I, the said George Pitt, have hereunto set my hand
and seal, this Twenty fifth day of February, in the year of our Lord One
thousand eight hundred and eighty.