Improvements in Photographio or Heliographic Copying Apparatus.
Year: 1895

page_text: Date of Application, 13th May, 1895-Accepted, 15th June, 1895
COMPLETE SPECIFICATION.
Improvements in Photographio or Heliographic Copying Apparatus.
I, HUGO SACK, Engineer, of 55 Sternstrasse, Dusseldorf, in the German
Empire, do hereby declare the nature of this invention and in what manner the
same 18 to be performed, to be particularly described and ascertained in and by
the following statement.—
The pneumatic copying apparatus described in the Patent Specification No. 15757
of 1884 contains an an-tight sheet or plate of india-rubber the edges of which are
applied tightly to a glass-plate, and after the diawing to be copied, together with
the sensitive paper, has been laid between the rubber plate and the glass-plate, the
air enclosed between the same is pumped out, or otherwise rarefied, so that the
drawing will be pressed upon the sensitized paper with a pressure vauable according
to the degree of exhaustion, up to 10,000 kilos. per square metre. The glass plate
is relieved of pressure, because the air pressure acts on both sides of the same.
To prevent the intrusion of air, the edges of the rubber sheet must be strongly
pressed against the glass plate, for which purpose the glass plate is mounted in a
frame which should support the edge of the glass plate at all points.
Ilitherto the pressure ou the edges of the rubber sheet has been produced by
means of a second frame corresponding in size to the rubber sheet and hinged like
a lid to the main frame holding the glass plate. To this lid or pressure frame the
ubber sheet has been fastened, so as to rise with the latter when the apparatus is
being opened, and to drop or fold down when the latter is being closed. In order
to act on this pressure frame, I had employed numerous short levers or screw-
fasteners secured to the circumference of the main frame and capable of being
turned back.
The glass plate was embedded ma access of the main-frame, and the pressure
frame was adapted to enter said reccss. In opening the apparatus, it was necessary
to turn back all of the said levers, before the pressure frame could be lifted out.
To open the locking or closing device only partially, was not practicable, and for
observing the effect of the light on the sensitized paper it was therefore necessary,
to release numerous locking levers or fasteners and to lift out the pressure frame,
which owing to the weight of the latter was very troublesome in the case of large
copying apparatus It was difficult to ensure, that the edges of the ground glass
plate were supported all round, even in the case of new copying apparatus; in
consequence of which a layer of putty was interposed in some cases. Solt elastic
packings, such as india-rubber and felt, have also been tied, but without the
desired success.
The improvements represented by the accompanying drawings have for their
object to avoid these and other drawbacks.
Fig. 1. is a vertical section of a copying fiame embodying my invention.
Fig. 2. shows a modification
A represents the main-frame, B the glass plate.
The closing device does not consist of a pressure frame or cover constituting one
piece, but of separate pressure bats on ledges, C, applied to the sides of the main
frame and capable of being turned down, as indicated in Figs. 1. and 2. by dotted
lines. Said bars or ledges are held in their locking position by screw-clamps D,
Fig. 1., or by means of a wire-sping E, or equivalent tension device neting on
extensions F. of the hinge levers, so as to press the edges of the rubber sheet G
strongly upon the glass plate.

page_text: In the open position of the copying apparatus, the pressure bais, together with
the rubber plate and hinge levers, are turned back, so as to leave the surface of
the glass plate perfectly fiee. The rubber plate G is preferably fixed to one of the
pressure bars C, and rolled up, when the apparatus is not in use
It will be seen, that the improved apparatus possesses the following distinctive
features and advantages
-
1. The indiarubber sheet or cover is not kept tight by means of a frame, but by
separate pressure bais o ledges, of which one or more may be placed on each side
of the frame. For observing the effect of the light, only a few fasteners need be
released, and only two pressure bais o ledges (which form one corner) need be
turned back.
2. There is no danger of breaking the glass plate by accidentally allowing the
locking device to drop, because the locking devices are connected with the pressure
bats and are so arranged, that, even when used negligently, they cannot drop on
the glass plate with sufficient force to break the same.
3. As the pressure bars and the locking devices are connected and move together,
little manipulation and attention is required for opening and closing the frame,
and for the same reason, the locking devices are not easily damaged.
4 The glass plate is not laid in a access of the frame, but upon the flat face of
the same, so as to be open and accessible on all sides, and any warping of the
main-frame or unequal support of the glass plate would soon be noticed, for the
same reason, the face of the main frame may be easily planed and readjusted.
5. As the pressure bais or ledges are not igidly connected, but independent of
each other, it is easy to close the frame tightly on all sides and to notice any
defect or inequality of the surface.
Having now particularly described my invention, and in what manner the same
may be performed, I declaic that I claim :
1 A heliographic or photographic copying apparatus comprising 10 its
construction a mam-frame having a flat supporting sun face for the glass plate,
pressure bars or ledges adapted to press the edges of the indiarubber plate or other
air-tight cover upon the glass plate, one or more of the said bars or ledges being
arranged on each side of the fiame and hinged to the same independently of the
others, and screw-clamps or equivalent locking devices adapted to press the sand
bars or ledges against the plate, the whole being arranged and adapted to operate
substantially as described.
2. A pneumatic photographic copying apparatus, having a flat-faced main
frame A, independent pressure-bars C, C, hinged to the main frame, an air-tight
cover G fixed to one of the said bais oi ledges, and locking devices, substantially
as described and shown by the drawings.
Dated this 10th day of May 1895.
FAIRFAX & WETTER,
433, Strand, London, Agents.