Improvements in Lenses for Telescopes, Photographic Cameras, and Magic Lanterns.
Year: 1892

page_text: Date of Application, 21st Oct., 1892-Accepted, 3rd Dec., 1892
COMPLETE SPECIFICATION.
Improvements in Lenses for Telescopes, Photographic Cameras, and
Magic Lanterns.
!.
I, MAURICE JAMES GUNN of 1. Priory Villas Brownhill Road Catford,
London S.E. Dealer in Works of Art, 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 an improved construction of lenses for telescopes,
photographic cameras and magic lanterns, and has for its object to provide a lens...
which will be less expensive-than the ordinary solid lens, the invention being more
particularly applicable to lenses of large size.
In carrying out my invention, I construct a hollow case as hereinafter described,
in the form of a lens but hollow, and made mainly of glass or other transparent
material, (hereinafter referred to as glass).
Within this case or hollow lens, is placed water or other clear liquid, the whole
forming a complete lens. The lens is formed by two plates of the transparent,
substance, one or both of which is or are curved in the desired.manner, and the two
are connected together by a metal or other tubular case.
According to one arrangement there is an annular projecting part around the
interior for each glass against which the edge of the glass. rests,. being fixed by
cement. This annular part may be formed by turning in a lathe or by forming
channel in the case atithe required parts.
:
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Instead of fixing with cement a cap may be employed, screwed on to or into the,
tube, and fitting closely around the edge of the glass, and pressing it against
the annular projection. With this arrangement, the lens can be readily taken to
pieces, and fresh glasses put in...
:
Indiarubber or other soft material must be placed between the ledge and the
glass in order to render it less liable to get broken. A simpler form in which
the parts are not detachable, consists in making the ends of the. tube slightly
thinner, forming a ledge. against which the glass would rest, the ends being then
turned over on the glass, fixing it in. place. In order that the liquid may be
admitted, a hole is formed in the case or in some cases in the glass itself, closed by.
a cap or other suitable means, or when the opening is in the glass, by sealing it
after the liquid has been inserted. The tubular case into which the glasses are
fitted may be made in two parts, one screwing over the other, or sliding over it, the
two fitting tightly together, in order that the thickness of the lens may be regulated
to any desired amount. The lens is preferably filled with liquid at a rather high
temperature, higher than it is likely to reach when in use, so that on cooling a
slight space is left, with vacuum, to allow for any expansion that may occur.
:)
This will not interfere in any way with its use, as the sides of a lens are never!
used and the tube or aperture used for filling may be made sufficiently large to
serve for the empty space. A lens may also be formed with a cell wholly of glass,
the two parts being formed with rims or cylindrical sides, which are placed
together and joined by a band of glass or suitable material, liquid being inserted as
before.
In order to form the glasses for the lens, I may blow a hollow sphere in a mould
or box of the required form, manipulating the mould in the manner well known to.
glass-blowers, in order to get an even surface and thickness. I afterwards with a
cutting instrument, cut the sphere into parts of the required diameter, the size of
the sphere regulating the curvature of the lens so that a regular and known
curvature is always obtained.

page_text: According to another arrangement the glasses are moulded or pressed into shape.
When used in photographic cameras the usual stops are employed in front of, or
between, the lenses to reduce the light and give the required clearness of
image.
In order that the invention may be more clearly understood, reference is had to
the accompanying sheet of drawings, in which
Figs. 1 to 5 are sections, illustrating various slightly modified methods of forming
the lens, the tubular case being employed in each modification,
Fig. 6 illustrates, the moulding or pressing method of forming the glasses,
Fig. 7 a modified form of lens suitable for the glasses made by the moulding or
pressing process,
Fig. 8 the method of making the glasses by blowing the hollow sphere, and
Fig. 9 a lens of larger size with tap for filling or emptying.
Referring to Figs. 1 and 2, A is a cylinder or tube, having a second cylinder A',
screwed as shown in Fig. 1, or fitting tightly without screw, as shown in Fig. 2,
over the first, in such a manner that it can screw or slide over it. to the position
required. They are each provided with the annular rims or shoulders a, against
which the glasses B rest, being fixed by cement. These shoulders
be curved
may
to suit the curvature of the glass, or may be flat, as shown in Fig. 1, with
packing a', of indiarubber or other material, for the glass to abut against.
According to Fig. 4, the annular shoulder a is formed by means of a channel in the
cylinder.
+
Ais the aperture in the case, through which the liquid is inserted, closed by
means of a screw cap. In Figs. 3 and 4 a cap Cis-employed to hold the glass in
position on the annular seat, being screwed on the outside in Fig. 3 and in the
interior in Fig. 4. Fig. 5 illustrates a simpler method of fastening the end c of
the tube being made thinner and turned over on the glass, holding it against the
shoulder a². According to Fig. 7, the two glasses A are joined together by the.
band D, the glasses consisting of a cylindrical part B' as well as the curved face.
bis the globe or hollow sphere shown in Fig. 8, blown in the mould E, from which
the glasses B may be cut in the manner above described..
The large lens shown in Fig. 9, is held in a similar case to that already described,
with shoulder a and screwed cap C, and is provided with the tap F at the bottom,
with opening at top, by means of which it can be filled and emptied. Two glasses
only are shown, but it is obvious that an intermediate glass or glasses may be
inserted, if desired dividing the lens into two or more compartments.
These lenses are intended only for application to telescopes, cameras and magic
lanterns, and not to such purposes as condensers for microscopes & the like.
I am aware that liquid leuses are not broadly new, and my invention only relates
to special constructions of such lenses.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be pèrformed, I declare that what I
-claim is :-
(1)-A-lens for use in cameras, telescopes and magic lanterns, formed by two
glasses, one, or both of which are oneyed, connected together by a tubular case,
having annular shoulders to which the glasses are fixed, in such a manner that a
hollow case is formed. which is filled with clear and transparent liquid, substantially
as described and for the purposes specified.
(2) A lens formed of glasses B, fitted into a tubular case A, having annular
shoulders a, against which the glasses are held by means of the screwed caps C, the
interior being filled with clear liquid, substantially as and for the purposes
specified.
(3) A lens formed of glasses B, fitted into a tubular case A having shoulders a³
and turned over ends c, and supplied with liquid, substantially as described and
shown in Fig. 5.
(4) In a lens of the kind described, a tubular case, formed of cylindrical

page_text: portions A and A', one of which can be screwed over the other and adjusted
substantially as described and illustrated in Fig. 1.
(5) In a lens of the kind described, a tubular case formed of parts A. and A³,
one of which slides over the other and can be adjusted. in position, substantially as
described and shown in Fig. 2.
(6) A lens formed of two glasses B, with cylindrical extensions B', connected
together by the band D and filled with liquid, substantially as described and shown
in Fig.
Dated this 21st day of October 1892.
GEO. H. RAYNER,
37, Chancery Lane, London, W.C., Agent for the Applicant.