Improvements in Pneumatic Photographic Printing Apparatus.
Year: 1897

page_text: Date of Application, 5th June, 1897-Accepted, 12th Mar., 1898
COMPLETE SPECIFICATION.
Improvements in Pneumatic Photographic Printing Apparatus.
ARTHUR SCHWARZ, of 7, Featherstone Buildings, in the County of London,
England, Engineer, 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:-
The pneumatic photographic printing devices hitherto used, present the dis-
advantages that air is apt to remain between the pressure layer and the sensitized
paper, whereby a perfectly uniform adjustment and pressure of the paper to the
negatives is prevented, so that the copies are liable to be somewhat unclear in
some places.
Moreover these pneumatic devices are hardly practical for the wholesale manu-
facture, as the adjustment of the pressure blanket, the exhaustion of air and the
removal of the blanket take too much time.
In the device embodied in the present application, I have endeavoured to
remove these disadvantages by the use of a special pressure blanket and of a
continuously operating copying apparatus.
In the hitherto known pneumatic copying apparatus a glass plate is arranged
in the frame, and upon this plate are placed negatives against which the sensitized
paper is to be firmly and uniformly pressed. This is effected by means of a
layer permeable to the air and resting upon an air-tight plate. This air-tight
plate with the layer resting thereon is pressed in a mechanical way against the
paper, whereby air-tight closure is obtained by means of the air-tight rims of
the plate. The air contained in the air-tight space under the plate is then exhausted
and the atmospheric air will now press the plate against the sensitized paper,
and the paper against the negatives. The layer permeable to the air has for its
purpose to maintain communication with the suction pipes over the entire area
of the surface covered by such layer.
But this purpose is not attained with sufficient reliability by the permeable
layer, especially not when the operation i.e. the exhaustion of air is quickly
effected.
I have illustrated my improved pneumatic copying apparatus in the annexed
drawings, making a part of the specification, and wherein :-
Fig. 1 shows a vertical section of my rapidly and continuously operating
copying apparatus, consequently allowing of a rapid exhaustion of the air:
Fig. 2 shows a plan view of my improved pressure blanket;
Fig. 3 shows a section of this blanket;
Fig. 4 shows a double apparatus on the same principle; and
Figs. 5 and 6 show details of construction.
The glass plate a is as usually arranged in the frame A, and the negatives are
attached in any suitable manner to this plate. The frame A is fastened to the
table B and is provided at its lateral walls with slots through which the sensitized
paper c emanating from a reel C is fed under the negatives b. The pressure
blanket d is supported upon a movable pressure plate D, which when raised,
presses the blanket d with its elastic rims against the paper, which is then
pressed against the rims a¹ of the glass plate a.

page_text: This operation is performed by a continuously acting engine, rotating the
shaft e and consequently the cam E mounted thereon. As long as the pin f of
the slide F, connected to the pressure plate D), rests upon the circular part of
the cam E, the pressure plate with the blanket d resting thereon is kept lowered,
and the sensitized paper c cau be advanced as required. (Fig. 1.)
As soon as the cam E rotating in the direction of the arrow, has turned far enough
to release the pin f from its circular part, the springs g raise the pressure plate D,
and press it against the sensitized paper c so that the rims d', a', surround an
air-tight space.
The shaft e imparts also motion to a second cam H, upon the circular part of
which slides the end of a spring actuated lever h which forms the key for the plug
of the cock i, arranged in the pipe k connecting the copying apparatus and the
exhaust chamber I. Conveniently arranged rubber tubes K run from the pipe k
through the pressure plate D to corresponding openings in the blanket d (Fig. 1).
These openings are of course located within the rims d' as shown in Fig. 2.
At the moment the pressure plate D is raised by the springs g and the blanket d
is closed air-tight at its rims, the cam H has rotated so far as to release the arm
of the lever h sliding upon its circular part so that the cock i will be opened in
consequence of the action of the spring h' upon said lever h.
In this manner, the exhaust chamber I, the vacuum in which is maintained as
much as possible by a continuously acting engine, is connected by means of pipe k
and rubber tubes K with the space closed by the blanket, and the air in this space
is consequently rapidly exhausted.
The consequence is that the blanket d is pressed by the atmospheric air against
the sensitized paper c and this paper against the negatives b attached to the glass
plate a. It is absolutely necessary that the air between the blanket and the sensi-
tized paper must be enabled to flow off very rapidly, as otherwise air bubbles
will be formed under the paper, preventing the perfect uniform pressure of the
paper upon the negatives.
To attain this rapid and complete exhaustion of the air, fine ribs or projecting
ridges L are provided upon the side of the blanket pressing against the sensitized
paper (Fig. 2) in such manner that when the blanket is pressed by the atmospheric
air, small channels (Fig. 3) are formed, which channels form a permanent
connection of the remotest parts of the surface of the blanket with the exhaust
pipe and tubes k, K.
This arrangement is distinctly shown in Figs. 2 and 3.
Before the air is exhausted the blankets presents a plane surface (Fig. 1), but as
soon as the air is exhausted the ridges L will in the first place be pressed against
the paper c, and thereupon the parts of the blanket between these ridges are
pushed inwardly. (Fig. 3.) But the blanket will not exactly adjust against
these ridges on all sides and the necessary channels are formed through which the
air will rapidly flow off from all parts toward the suction pipe.
The arrangement of the ridges L as shown in Fig. 2 is of course not essential,
same may be arranged in any suitable way, the only requirement being that by
means of these ridges, channels communicating with the suction pipe will be
formed when the blanket is pressed by the atmospheric air.
As soon as the blanket has so pressed the sensitized paper against the negatives,
and when electric light is being used for the exposure, the lamps m arranged in
the cap M are lighted automatically. The lighting of the lamps is advantageously
obtained through the medium of one of the cams E, H, and in the present instance
by the cam H.
For instance, sliding contacts O, connecting with the source of electricity, and
through wires o with the lamps m, may be so arranged, that slightly after the
formation of the vacuum over the blanket d, the circuit is closed and the lamps
are lighted.
When the necessary time for exposure has passed, the cam H will have rotated

page_text: so far, that the lever h is again raised, the cock i in the air pipe closed, and the
current in the lamps cut off.
In the meantime the cam E will likewise have rotated so far that its tappet a
strikes the pin f (Fig. 4) raised with the slide F connected to the plate D, and
pushes this pin and slide so far down that it reaches again the circular part of the
cam. (Fig. 1). The plate D is then pushed downward and the springs g are
thereby compressed.
The blanket d is only at one end firmly fastened to the pressure plate D, the other
parts only resting freely upon same. Consequently when the plate D is lowered,
the blanket is not immediately separated over its entire surface from the closing
rims a', the contact is only interrupted at one end for which little force is required.
As soon as the contact of the rims a¹, are interrupted at one spot, no matter
how small, the air will flow into the space and the blanket d will then drop upon
the pressure plate D. The sensitized paper is now advanced for a length, equal
to the distance of the rims a¹ a¹, and the rotary cams repeat the operation as above
described.
In the apparatus as described only paper sensitized on one side can be used.
If it is desired to use paper sensitized on both sides, .e. to make copies on both
sides, it will be sufficient to double the apparatus as shown in Fig. 4.
Upon the table B two frames A and A¹ are arranged in such manner; that in
the frame A the glass plate is placed uppermost, while in frames A¹ it
occupies the lower position. Consequently the blanket d' and pressure plate D¹ of
frame A¹ are arranged over the glass plate.
The mechanism for operating the pressure plates D D¹, the air pipe cock i, &c.,
is entirely the same as in Fig. 1, the only difference being that slide F is not
directly connected to the plate D, but by means of a double armed lever and the
strap Q. The slide F is jointed to the arm p of the lever, so that when the slide F
is moved downward by the cam E, the plate D is moved downward. The arm p¹
of the lever P is bifurcated as shown in Fig. 6, so that the straps Q1, jointed to
this arm, pass at the side of the frame A¹ and connect with the projecting edges
of the pressure plate D¹. Now, if the arm 2 is lowered by the slide F, and
consequently the plate D is lowered, the arm p₁ is raised and the plate D¹ also
raised. The sensitized paper c, fed through both frames, in the manner described
in connection with Fig. 1, can thus be freely advanced.
Instead of the one-way cock i used in the apparatus shown in Fig. 1, the con-
struction as shown in Fig. 4 implies the use of a three-way cock ¹, connecting
not only with the suction pipe k, but also with a branch pipe k¹, passing over the
frame A¹ and connecting with the blanket by means of the rubber tubes K¹.
When the lever h is released by the cam H, the cock is in the position shown
in Fig. 5, .e. the exhaust chamber I (Fig. 1) connects with both frames A and A',
the air is exhausted from both devices and consequently the sensitized paper
is pressed in both frames firmly against the negatives.
When during the further rotation of the cam H the cock ¹ is closed again, the
exhaust chamber pipe is shut off, and the pressure plates D D' can be moved in
the manner before described.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, I declare that what I
claim is:
1. A pressure blanket for pneumatic photographic copying devices, consisting of
a flexible plate provided with ribs or ridges, substantially as and for the purpose
described and set forth.
2. In a pneumatic copving apparatus, a glass plate provided with air tight
rims arranged at the edges of the plate, substantially as and for the purpose
described.
3. In a pneumatic copying apparatus, the combination of a flexible blanket

page_text: with a movable pressure plate and an automatically opening cock in the air suction
pipe, substantially as and for the purpose described and set forth.
4. In a pneumatic copying apparatus, the combination of a frame with a vertically
reciprocating pressure plate D, so that the air is exhausted from the frame when
the pressure plate is in its upper position, substantially as and for the purpose
described and set forth.
5. In a continuous pneumatic copying apparatus, the arrangement of sliding
electrical contacts, so that the lamps are lighted when the blanket is pressed
against the paper, substantially as and for the purpose described.
6. A continuous pneumatic copying apparatus, comprising two adjacent frames
so that the paper is exposed in one frame from above and the other frame from
below, and the blankets in both frames are simultaneously pressed against the
sensitized paper, substantially as and for the purpose described.
Dated the ith day of June 1897
ARTHUR SCHWARZ.