Improvements in Photographic Enlarging Apparatus.
Year: 1895

page_text: Date of Application, 7th Oct., 1895
Complete Specification Left, 9th June, 1996-Accepted, 11th July, 1896
[Communicated from abroad by LEON GAUMONT, of No. 57 Ruo St. Roch, Paris,
France, Manufacturer of Photographic Apparatus]
Improvements in Photographic Enlarging Apparatus.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane,
in the County of London Consulting Engineer and Chartered Patent Agent, do
hereby declare the nature of this invention to be as follows
Ordinary photographic enlarging apparatus is composed of three moveable frames
carried by a common base, which frames are connected together by a flexible structure
or by a slide, the one of the outer frames carrying the cliché to be enlarged, and the
other the sensitive surfaco that is to receive the enlarged image, while the middle
framo carries the objective wluch effects the enlargement The enlargement obtained
is the greater in size, the greater is the proportion between the distance of the
objective from the sensitive surface and the distance of the proof to be enlarged
from the objective But it is not sufficient for obtaining the increased size to shift
the frame carrying the objective, because then the focus will not be correct for
producing a distinct enlarged mago, it is necessary also to shift suitably, by trials,
the frames which carry the proof to be enlarged and the sensitive surface, in order to
obtain a sharply defined enlarged image. There are therefore two variable conditions,
namely modifications of the relation of the distances and adjustment of the position
of the images
According to my present invention, I construct an enlarging apparatus in which
the two outer frames are fixod, heing connected together by a casing which cannot be
expanded or contacted, the objective, situated between them being alone moveable.
By this means however only one condition is satisfied, namely the alteration of the
proportion between the distances. The enlarged image will not be well defined unless
a second condition is fulfilled, and for this purpose, instead of adjusting the frames
carrying the images, I modify the focus of the objective by providing a supplemental
convergent lons.
The apparatus is constructed for this purpose as follows: A box or casing of
pyramidal or tapering form carries at its smaller ond the photographic proof to be
enlarged, and at its larger end the frame containing the sensitivo surface which is to
receive the enlarged image Frames of various dimensions are provided at either
end for receiving proofs or chches of various sizes.
Between the two ends the box contains the objective, which is mounted in a frame
that can be slid either forwards or backward by a rack and pinion motion, actuated
by an external button Tho axis of the pinion carries a second pinion, gearing with
a toothed wheel on the axis of which is a dise having divisions on its periphery, so
that on turning the button the sliding frame can be adjusted to a position indicated by
a division of the disc coming opposite & hxed pointer
The objective is composed of two converging lenses with diaphragins, in the
ordinary manner. In addition, there are provided a series of supplemental lenses of
different focus, arranged in a row on a sliding frame sliding through the objective
between the other two lenses, so that according to the position to which the objective
is adjusted relatively to the proof and sensitive surface, a corresponding supplemental
lens is brought between the other lenses for modifying the focus of the objective.

page_text: The arrangement employed by preference for moving the slide with the supplemental
lenses automatically consists in attaching to each end of the slide a small chain,
passing round guide rollers, the chain at the one end of the slide being led backwards
and having its end attached to a rear part of the casing of the apparatus, while the
chain at the other end is led forward, and has its ond attached to a forward point of
the casing. Thus on shifting the objective forwards or backwards, the slido will, on
account of the above described attachments, be automatically shifted transversely so
as to bring the proper supplemental lens between the other two lenses. For insuring
the accuracy of position of the supplemental lens, the slide is formed with notches
into which takes a spring tooth on the frame of the objective. The supplemental
lenses may also be arranged round the periphery of a rotatable disc instead of on a
slide; or the supplemental lenses might be separate from each other, and be placed in
position by hand, as may be required, but the other arrangements are preferred
⚫ Dated this 7th day of October 1895.
ABEL & IMRAY,
Agents for the Applicant.
Improvements in Photographic Enlarging Apparatus.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane, in
the County of London, Consulting Engineer and Chartered Patent Agent, 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
Ordinary photographie enlarging apparatus is composed of three moveable frames
carried by a common base, which frames are connected together by a flexible structure
or by a slide, the one of the outer frames carrying the cliché to be enlarged, and the
other the sensitive surface that is to receive the enlarged image, while the middle
frame carries the objective which effects the enlargement The enlargement obtained
18 the greater in size, the greater is the proportion between the distance of the
objective from the sensitive surface and the distance of the proof to be enlarged
from the objective. But it is not sufficient for obtaining the increased size to shift
the frame carrying the objective, because then the focus will not be correct for
producing a distinct enlarged image, it is necessary also to shift suitably, by trials,
the frames which carry the proof to be enlarged and the sensitive surface, in order
to obtain a sharply dofinod enlarged image. There are therefore two variablo
conditions, namoly modifications of the relation of the distances and adjustment of
the position of the images.
According to my present invention, I construct an enlarging apparatus in which the
two outer frames are fixed, being connected together by a casing which cannot
be expanded or contracted, the objective, situated between them being alone
moveable. By this means howover only one condition is satisfied, namely the
alteration of the proportion between the distances. The enlarged image will not
be well defined unless a second condition is fulfilled, and for this purpose, instead
of adjusting the frames carrying the images, I modify the focus of the objective
by providing a supplemental convergent lens.
The apparatus is constructed for this purpose as I will describe with reference
to the accompanying drawing in which Fig. 1 shews a longitudinal section of the
same, Fig. 2 a sectional plan, Fig. 3 an end view, Fig. 4 å part plan showing the
indicator gear,
and Fig. 5 a section on line m n Fig. 1.
The apparatus consists of a box A of truncated pyramidal form which receives
at its smaller end B the photographic proof to be enlarged, and at its larger end C
the frame containing the sensitive plate or sheet on which the enlarged image is

page_text: to be produced. There are several intermediato frames of various sizes adjusted
one within the other at B, for receiving proofs or clichés of various sizes.
At C there may also be provided various sized frames.
The objective O arranged between the two bases B, C, is mounted in a frame D
which can be moved in one direction or the other by turning the button E the
axis of which carries a pinion F gearing with a toothed rack G fixod on the
frame D. The axis of the button E farthermore carries a small pinion a Fig. 4
gearing with the wheel of a disc c provided with divisions, which in being
brought opposite the index d will indicate the position given to the frame D of
the objective by the turning of the button.
The objective O is composed of two convergent lenses with diaphragms as usual,
presenting no special feature But it is completed by an additional series of
Tenses for suitably modifying the focal lengths of the objective in order that the
image may be perfectly cloar when the objectivo has been shifted for modifying
the degree of enlargement by varying the ratio of the distances
All these additional lenses are arranged on a single. plate which is shifted at
the same time that the objective is moved forward or backward, so as to bring
the particular additional lens into line which is suited for the position given to the
objective relatively to the two ends B and C.
This plate H, which moves between the two lonsos of the objective, carries at
suitable distances apart the additional lenses of varying focus. The arrangement
which I prefer to employ for automatically shifting the plate H for bringing the
correct additional lens in line with the objective when the frame D of the latter
18 moved forward or backward is as follows. The ends of the plate II aro oach
connected to a small chain o passing over a roller g and having its end & attached
to a fixed part of the apparatus. Thus on shifting the frame D, the plate with
the longes will be caused by the chains to move transversely to an extent proportional
to the motion of D, the lenses being at such distances apart that on shifting Da
certam distance the corresponding lens is brought exactly in the axial line of the
objective, thereby modifying the focal lengths of the objective to suit the altered
distances of the surfaces B and C relatively thereto. To insure such correct positions,
the plate II is formed with V shaped notches into which enters a tooth carried by
a spring
Instead of carrying the said additional lenses on a transversely sliding plate H,
they may be arranged round the periphery of a rotatable disop as shewn at Fig. 6.
Each additional lens might also be mounted in a separate frame, and be introduced
singly into the objective, as shewn at Fig. 7, but this arrangement is open to the
objection of having a number of separate lonses that might get mislaid, or be mistaken
one for the other
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
In combination with variable photographic onlarging apparatus having the objective
adjustable between two fixed end frames, tho uso of additional lenses for modifying
the focal lengths of the objective, which additional lenses are preferably all carried by
a plate that is automatically shifted transversely when the objectivo is shifted
longitudinally but which may also be carried on the periphery of a rotatable disc, or
be mounted in separate frames, substantially described.
Dated this 9th day of June 1896.
•
ABEL & IMRAY,
Agents for the Applicant.