IMPROVEMENT IN HELIOGRAPHIC COPYING APPARATUS
Year: 1884

page_text: I, HERBERT JOHN HADDAN, of 67, Strand, in the City of Westminster, Civil
Engineer, do hereby declare the nature of said Invention for "IMPROVEMENT IN
HELIOGRAPHIC COPYING APPARATUS," a communication to me from abroad by
Hugo Sack, Engineer, of Plagwitz-Leipzig, in the Kingdom of Saxony, to be as
follows:-
This invention has for its object to obtain a close adhesion or fit between the
sensitive paper and the original with a moderate pressure.
For this purpose I employ a partial vacuum in the following manner.
On the glass plate of the copying-frame is first placed the transparent drawing
or photographic negative to be copied, upon the latter the sensitive paper, on this
paper a sheet of woven fabric or other suitable inaterial permeable for air, and on
the said sheet a sheet or lid of indiarubber or other hermetically closing material
into the centre of which leads a tube.
If the edges of the lid close tightly upon the glass plate, and air is sucked from
the space situated between the glass plate and the lid, by means of the tube, and
any suitable exhausting apparatus for instance a sort of bellows provided with a
suction valve, the sensitive paper is firmly pressed against the original, without
exerting undue pressure upon the glass plate.
The glass plate may therefore be very thin and may be replaced by a transparent
membrane.
After the air has been sufficiently rarified, the tube is closed and the apparatus
exposed to the light.
In order to obtain an air tight fit at the beginning of the exhaustion an air
cushion may be placed all around the circumference of the lid; this annular air
cushion is exposed to the pressure of a frame, and may either be fixed to the lid or
to the frame.
Dated this 20th
גי
comhan 1004

page_text: Improvement in Heliographic Copying Apparatus.
I, HERBERT JOHN HADDAN, of 67 Strand, in the City of Westminster, Civil
Engineer, do hereby declare the nature of said invention for IMPROVEMENT IN
HELIOGRAPHIC COPYING APPARATUS, a communication to me from abroad by Hugo
Sack, Engineer, of Plagwitz-Leipzig in the kingdom of Saxony, and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
For obtaining distinct copies by the heliographic process it is necessary to press
the sensitive paper very tightly against the original to be multiplied, or against
the photographic negative, for which purpose special copying frames are usually
employed.
A uniform adhesion has hitherto been obtained in an imperfect manner by
producing a mechanical pressure, which tends to bend the glass plate and therefore
requires a glass plate of considerable thickness and a bulky construction of the
apparatus.
By the improved method on the contrary the glass plate is relieved of pressure by
the production of a partial vacuum between the paper and the glass plate.
In the accompanying drawings Figs. 1. and 2 are sectional diagrams of the
improved copying frame. a indicates the glass-plate, b the sheet of drawing to
be copied, c the sensitive paper, d a layer of a material permeable for air, such as a
woven fabric, e an air-tight elastic cover, for instance one made of india-rubber.
In this cover terminates a tube f. When the rims of the cover e are in uniform
contact with the glass plate and a vacuum is produced between e and a by suction
through the tube f, the sensitive paper is tightly pressed against the original
without bending the glass-plate. Therefore the latter may be very thin and may
even be replaced by a translucent membrane. The layer, permeable for air, has the
purpose to produce at all spots of the surface, covered by the same, a communication
with f. The air being exhausted, the tube f is closed by a cock, and the apparatus
is exposed to the light.
For entirely separating the air in the apparatus from the outer atinosphere,
before beginning the exhaustion, a packing ring g, extending along the whole
circumference of the cover e, is arranged, which ring may consist of a solid strip of
indiarubber, as shown by Fig. 1, or of a rubber tube, closed in itself and filled with
air or liquid, as shown by Fig. 2.
This elastic packing ring is uniformly exposed to the pressure of a frame or lid,
so that the rims of e come at once in contact with the glass-plate, even if the latter
be uneven.
The principal advantages over the appliances hitherto used are the following:
For the translucent plate ordinary window glass, free of bubbles, may be used.
As the indiarubber cover adapts itself closely to any unevenness, the plate need not
be polished. Therefore it costs much less than heretofore and can be more easily
procured.
The paper surfaces are pressed against each other with great energy. Already
by sucking with the mouth, a reduction of pressure of ½ atmosphere can be produced,

page_text: On a surface of 1 square meter the reduction of pressure would therefore amount
to 2000 Kilos, which may be considerably increased by the use of an air pump, and
which suffices, to lay even the most uneven and creasy drawings everywhere against
the sensitive paper in a perfect manner. Consequently dull or clouded spots, which
often occur on heliographs produced by the apparatus hitherto used, are entirely
avoided.
For causing also pinches to be perfectly pressed out and smoothed, a paste-board
is put between the woven fabric d and the sensitive paper c, or stiffened felt is
used as a material for the permeable layer, or a woven metallic tissue, containing
cotton threads. This hard intermediate layer is sufficiently elastic to follow every
unevenness of the glass plate, but cannot adapt itself closely to the projecting folds,
so that all the pressure, produced near the same, is employed for smoothing
the folds.
Figs. 3-5 illustrate an embodiment of the aforementioned principle, in which
figures corresponding parts are indicated by the same letters as before.
The permeable layer is pasted together with the indiarubber cover, which is
fastened under the aforementioned pressure frame or lid. The latter fits into the
opening of the main frame, which is formed like an ordinary window-frame. The
papers being laid io, and the lid with the india-rubber cover etc, being put on, the
lid is slightly pressed against the surface of the glass by means of a few bolt-
levers k, the enclosed air is exhausted by a few suctions, and the suction pipe is
stopped by a cock, after which the action of the light may commence.
If an air pump is to be employed instead of sucking with the mouth, such pump
may be applied to the apparatus as a handle, as shewn by Figs. 2 and 5.
Having now particularly. described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare, that what
I claim, is
In photographic or heliographic copying apparatus :
1. The combination of a main frame, with a lid, a glass plate or membrane a,
permeable sheet d, hermetically closing elastic cover e, and means for producing a
vacuum between the cover c and the glass plate.
2. Producing a vacuum in the apparatus betweeen the sheet a permeable to air,
and the hermetically closing elastic cover e, for the purpose of obtaining a perfectly
uniform contact of the sheets b and c, with each other, or between the sensitive
paper and the photographic negative.
3. An elastic packing ring g, adapted to hermetically enclose the volume of air,
contained in the apparatus.
4. The use of a membrane, instead of a glass-plate.
The whole substantially as described.