Note: Descriptions are shown in the official language in which they were submitted.
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The presen-t invention relates to an exposure device for plates
carrying photosensitive coatings. The exposure device comprises frame elements
which can be separated from each other and moved into contact with each other
and are vertically mounted on a base. Between the -frame elements, the plate
which is to be exposed and at least one master are arranged and pressed to-
gether during the exposure process while, at the same time, a vacuum is
pulled. The exposure device further comprises at least one exposure lamp
arrangement.
German li-tility Model No. 1,940,812 discloses vacuum printing devices,
for example, vacuum printing frames, for exposing photosensitive plates~ films
or the like, which are used in the production of relief printing forms. A
vacuum printing device of that kind has a mounting plate provided with two
separate aperture systems in the upper surface thereof. One of these systems
is connected with a vacuum source and the other with an air-inlet controlling
valve. During exposure, the photosensitive plate and a master lying on top
are held in contact with the aperture systems by means of a vacuum cover film
and are thus hermetically sealed against the surrounding atmosphere. The
photopolymerizable plate and a transparent master lying on top, for example~
a photographic negative, a positive or a matrix, are mounted on the flat
vacuum printing frame, comprising a supporting frame and the mounting plate
fastened in the frame. The mounting plate is supported either in a horizon-
tal or in a vertical position. The light source used for exposure emits
light having a high ultraviolet fraction, such as, for example, an arc lamp.
The vacuum printing device is designed such that air can only enter into one
of the two aperture systems through the air-inlet controlling valve and escapes
through the other system towards the vacuum source. As a result, a gentle
stream of air is produced between the surface of the unexposed plate and the
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matte surface of the master held in contact therewlth, so that the photo-
sensitive plate is supplied with the oxygen required for reducing the sensitiv-
ity of its upper layer.
In the above-described device, simultaneous exposure of both sides
of the photosensitive plate is impossible and is not intended, since the plate
carries a photosensitive coating on one side only and there is, only one light
source for exposure.
In German Auslegeschrift No. 1,154,351 a copying device is described,
which includes an evacuatable housing made of a flexible material and
accommodating an original which is to be copied and a photosensitive element
in superposed arrangement. The housing is open at one end and is tightly
sealed by a transparent plate resting on a gasket which runs around its upper
edge. A screen and a transparent air bag of an elastic air-tight material are
arranged above the photosensitive element. When the copying device is evacuat-
ed, the air bag is extended by the air contained therein and is forced against
the underside of the transparent plate and against the screen, thus exerting
pressure upon the screen and the photosensitive element. The air which is
present between the original and the photosensitive element is pressed outwards,
so that creases do not form when the photosensitive element contacts the
original. As soon as the evacuation process is completed, exposure is carried
out by means of a commercial light source. Just as in the case of the afore-
described prior-art device, this copying device only allows exposure of one
side of the photosensitive element.
For the production of photoresist images according to United States
Patent No. 3,547,730, a support plate is coated with a photoresist material
on both sides thereof and is then introduced into an exposure device, which
comprises two rectangular frames arranged opposite to each other, transparent
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pressure plates -to which image-bearing transparencies are attached
and radiation sources, for example, arcs. One of the frames is
equipped wi-th pins which engage in holes in the opposite frame,
in order to obtain an exact adjustment of the transparencies and
the coated support plate. At the four corners of the Erames,
four springs are provided, which surround pull rods and keep the
frames at a dis-tance from each other. Solenoids actuate the pu]l
rods against spring pressure, thus causing the frames to contact
each other -tightly for the exposure process. During exposure, the
transparencies are forced against the photosensitive resist material
by mechanical pressure exerted by -the pressure plates, which are
pressed together by means of the solenoids. Evacuation of the
exposure device is not provided for and, consequently, it may be
possible that air pockets, which impair the image quality, are
formed between the individual transparency and the photoresist
layer.
The present invention provides an exposure device which
renders possible a perfect exposure of the two photosensitively
coated sides of a vertically arranged plate, while preventing
air pockets from forming between the two sides of the plate and
the masters pressed against them and which allows uncomplicated
changing of masters.
According to the invention, there is provided an exposure
device for plates carrying photosensi-tive coa-tings, comprising
frame elements which can be separated from each other and moved
into contact with each other and are vertically mounted on a base
and between which a plate which is to be exposed and at leas-t one
master are arranged and pressed together during the exposure
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process while, at the same time, a vacuum is applied, and further
comprising at least one exposure lamp arrangement, wherein one
of the frame elements is designed as a stationary mounting support
and the other frame element comprises a mounting support which is
movable in relation to the stationary mounting support, wherein
exposure lamp arrangements are disposed on either side of and
at a distance from the pushed-together mounting supports, which
are connected with a vacuum pump, wherein a motor and pairs of
sprockets and gear wheels which are, in each case, mounted on a
common shaf-t, are arranged on a lower crossbar of the stationary
mounting support on the side facing an adjacent one of the
exposure lamp arrangemen-ts and wherein the motor drives the gear
wheels by means oE an endless driving chain which is guided over
the sprockets.
Each mounting support comprises a planar glass plate in
a frame and each frame has suction means which are spaced around
its circumference and are connected with the vacuum pump.
The movable mounting support is appropriately displaced
on guide means and two compressed-air cylinders are connected
with the frame of the movable mounting support and with stationary
side walls, between which the movable mounting support can be
moved forward and backward.
The invention offers the advantages that handling o:E the
masters is facili-tated, imperfections on the exposed plate
surfaces are almost entirely precluded, the masters and the plate
which is to be exposed on both sides are adjusted to an exact
position and the masters can quickly be exchanged.
Below, -the invention is explained in de-tail with
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reference -to an embodiment of the exposure clevice shown in -the
accompanying clrawings.
Figure 1 is a diagrammatic -total view in section of the
exposure device according to the invention,
Figure 2 is a diagrammatic sectional view oE mounting
supports of the exposure device acco:rding -to Figure 1, which are
separated from each other,
Figure 3 is a sectional view of the mounting supports
according to Figure 2, which are brought -together, so as to form
a gap between them,
Figure 4 is a perspective view showing the back of the
movable mounting support which has been moved forward in the
direction of the stationary mounting support, and
Figure 5 is a perspective view showing the back of the
stationary mounting support.
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The diagrammatic sectiona] view of Figure 1 shows an exposure device
1 which includes a base 29, a left-halld and a right-hancl exposure lamp arrange-
ment 5 and 5', a movable mounting support 2 and a stationary mounting sup-
port 11. The exposure lamp arrangements 5 and 5' are stationarily arranged
at the ends of the base plate of the base 29. Each exposure lamp arrangement
is e~uipped with a shutter 28 and 28l and a lamp emitting light in a spectral
region which is adapted to the photosensitive coating on a plate 12 which
is to be exposed.
The movable mounting support 2 is carried by side walls 15 and 15'
and on the inside of each side wall two guides for rails 3 are attached, as
can be seen from the perspective view of Figure 4, so that the mounting sup-
port 2 can be moved forward and backward. For displacing the mounting
support 2, two compressed-air cylinders 4 and 4' are provided, which are
connected with the stationary side walls 15 and 15l and also with the frame
24 of the mounting support 2. When the compressed-air cylinders 4 and ~' are
actuated, tl1e movable mounting support 2 is pushed forward in the direction
of the stationary mounting support 11 or pulled back again, in a direction
away from the stationary mounting support.
Each of the mounting supports 2 and ll has a planar glass plate 23
and 23l in a frame 24 and 24' and is connected with a vacuum pump 22. Around
the circumference of each frame 24 and 24' suction devices 7, 7l, 7l- ... are
arranged, which are linked up with the vacuum pump 22 via common vacuum lines
31 and 31' (Figures 1 and 4).
For reasons of clarity, the vacuum lines are not shown in Figure 5.
The guides for rails 3 on the inside of each side wall 15 and 15'
are arranged above and below the respective compressed-air cylinder ~ and 4'.
Figure l depicts the position in which the two mounting supports 2
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and 11, have been pushed together and a plate which is to be exposed on both
sides, for example, a printing plate or a circuit board 12, is in contact
with masters 9 and 9'.
For adjusting and positioning the masters 9 and 9', the stationary
mounting support 11 is equipped with positioning pins 6, 6', 6" .... which
are passed through the frame 24' of the stationary mounting support 11 and
are connected with compressed-air cylinders 14, 14', 14" .. The positioning
pins 6, 6', 6" , ... are disposed close to the lower edge of the upper cross-
bar of the frame 24' of the mounting support 11 and the compressed-air
cylinders 14, 14', 14" , ... are arranged on a level with the positioning pins,
at the back of the stationary mounting support 11~ i.e. on the side facing
the exposure lamp arrangement 5'. The positioning pins 6, 6', 6" , ... are
engaged by springs 19, 19', 19" , ..., for example, compression springs,
which push the positioning pins back when the compressed-air cylinders 14, 14',
14'', ... are in the pressureless sta-te, so that the pointed ends of the
positioning pins do not extend beyond the glass plate 23' of the stationary
mounting support 11. Instead of compression springs, it is also possible to
use tension springs which retract the positioning pins. The movable mounting
support 2 is provided with adjusting pins 10 and 10' which engage in corres-
ponding adjusting holes 18 and 18' in the stationary mounting support 11, and
adjust the two mounting supports with respect to each other before they are
moved into contact with each other by the compressed-air cylinders 4 and 4'.
As can be seen from Figure 5, a motor 16 and pairs of sprockets 30,
30', 30" , ... and gear wheels 20, 20', 20" , ... which are, in each case,
mounted on a common shaft, are arranged on the lower crossbar of the station-
ary mounting support 11 on the side facing the exposure lamp arrangement 5'.
The motor 16 drives an endless driving chain 17 which is guided over the
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sprockets 30, 30', 30" , ... The gear wheels 20, 20', 20" , ... mate with
further gear wheels 21, 21', 21" , ... mowlted on shafts which pass through the
frame 24' of -the mounting support 11. At the front of the mounting support 11,
these shafts carry drive rollers 8, 8', 8" , ... which serve to transport the
plate 12 which is to be exposed into the loading gap d formed between the two
mounting supports in the loading position of the exposure device 1, as shown in
Figure 3.
A retractable sensor 13 is arranged on the frame 24' of the stationary
mounting support 11 on the side facing the plate 12. Upon actuation by the
plate 12, the sensor disconnects a coupling, which is not shown, between the
motor 16 and the sprockets 30, 30', 30" , ... or the driving chain 17, respec-
tively, in order to stop the drive rollers 8, 8', 8" , ... and thus arrest and
position the plate 12 between the mounting supports 2 and 11.
Two swivelling positioning elements 25 and 25', having the shape of
latches, are pivotally mounted on the movable mounting support 2. The end
faces 26 and 26' of the positioning elements 25 and 25' act as stops and are
contacted by stop faces 27 and 27' on the frame 24 of *he movable mounting
support 2~ when the exposure device 1 is in the loading position (Figure 3),
in which a plate 12 is inserted into the loading gap d. In the loading posi-
tion, the positioning elements 25 and 25' extend horizontally, whereas they
are swivelled upward in the inserting position for the masters. In order to
position the two mounting supports for the supply of plates, it is also possible
to use pressure cylinders, the piston rods of which act as stops.
In the text which follows, the opera*ion of the exposure device 1 is
explained in detail.
Figure 2 is a diagrammatic view showing the two mountlng supports
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2 and ll in the inserting position for the masters 9 and 9'. The movable
mounting support 2 is displaced to -the extreme left-hand position by the two
compressed-air cylinders ~ and ~'. The two masters 9 and 9', which are
separated from each other by paper inserts, are simultaneously pushed onto
the positioning pins 6, 6', 6" , ... of the stationary mounting support 11
and, for this purpose, the masters 9 and 9' are provided with suitable register
perforations for the positioning pins. In this position, the positioning
elements 25 and 25' are swivelled upward. Immediately before the two mounting
supports 2 and 11 are pressed together, they are adjusted with respect to each
other by the adjusting pins 10 and 10', which are attached to the movable
mounting support 2 and engage in the corresponding holes 18 and 18' of the
stationary mounting support 11.
Then the compressed-air cylinders 4 and 4' are actuated in order to
move the mounting support 2 in the direction of the stationary mounting support
11 and the two supports are pressed together. As a result, the air which is
entrapped between -the frames 24 and 24' escapes and the masters lie flat on
the glass plates 23 and 23'. By means of the suction devices 7, 7', 7'',
the masters 9 and 9' are then sucked to the glass plates 23 and 23' of the
mounting supports. The positioning elements 25 and 25' are swivelled to a
horizontal position. The mounting support 2 is then retracted from the station-
ary mounting support 11 by means of the compressed-air cylinders 4 and 4',
- to such an extent that the so-called loading gap d, which has a width of about
6 to 8 mm, is formed. In this position of the two mounting supports 2 and 11,
which is diagrammaticlly shown in Figure 3, the paper inserts are removed.
The plate 12 which is to be exposed is then conveyed sideways,
into the gap d, by the drive rollers 8, 8', 8" , ... The sensor 13, for
example, a light barrier operating by reflection or a stop switch, disconnects
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the motor coupling, as mentioned above, thus stopping the drive rollers 8, 8',
8~, ... and terminating the transport of the plate 12. The plate 12 which
has register perforations in its upper part is accommodated and adjusted by
the positioning pins 6, 6', 6" , ... which are extended by the action of the
compressed-air cylinders 14, 14', 14" , ...
The exposure device 1 is now in its exposing position, as shown
in Figure 1, with the masters 9 and 9' being in contact with the two sides
of the plate 12 which is to be exposed. The plate is exposed by briefly
opening the shutters 28 and 28' of the exposure lamp arrangements 5 and 5'.
After exposure, the mounting support 2 returns to the loading position and the
positioning pins 6, 6', 6" , ... as well as the sensor 13 are retracted into
the frame 24' of the mounting support 11. The plate 12 which is now exposed
on both sides is discharged from the exposure device 1 by the drive rollers
8, 8', 8" , ... and the device is then ready for exposure of a fresh plate 12.
If the next plate 12 is to be exposed in contact with the same masters 9 and
9', the latter remain adjusted in their positions by the vacuum applied to the
devices 7, 7', 7" , ..., during the following loading operation.
