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Description  |
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BACKGROUND
This invention relates generally to the use of photosensitive imaging
systems and, more particularly, to the high speed development of
photosensitive film sheets bearing latent images.
Equipment for achieving an acceptable density level while processing
photosensitive film sheets rapidly is known and available. In an early
stage of its development, one of the limiting factors on the speed of
processing was the time required to dry a film sheet that had been
immersed in the processing liquids, for example, in developing and fixing
tanks. Meanwhile, rapid access in the development of film sheets has been
achieved by preheating the developing liquids and applying them to an
element from nozzles or so-called dribble bars. Although these and
analogous modes of application have yielded acceptable density levels in
reduced access periods, the final product oftentimes exhibits both
longitudinal and transverse nonuniformities and overall patterns of
irregular development.
DISCLOSURE OF INVENTION
Worthwhile improvements in uniformity of development have been achieved in
an apparatus that includes rolls for transporting an exposed film sheet
through at least one section where a processing liquid is applied. A
distribution bar delivers the liquid to a trough located above the path of
transport and the trough has one edge lower than the other. A foraminous
sheet extends lengthwise of the trough beneath the bar. Liquid passes
through the foraminous sheet as it enters and as it flows from the trough.
A ramp projects downwardly from the trough and terminates in close
proximity to the path of transport.
DESCRIPTION OF DRAWINGS
In the accompanying drawings,
FIG. 1 is a schematic of a processor incorporating the improvements of the
present invention;
FIG. 2 is a sectional illustration of the liquid applicators in the first
section of the processor shown in FIG. 1;
FIGS. 3 and 4 are top and front views, respectively, of the troughs shown
in FIG. 2;
FIG. 5 is a schematic showing the flow of liquid from the first applicator
in FIG. 2;
FIGS. 6 and 7 are top and end views, respectively, of the pan shown beneath
the path of transport in FIGS. 1 and 2, FIG. 7 having been taken on line
VII--VII in FIG. 6;
FIG. 8 is a sectional illustration on line VIII--VIII in FIG. 6;
FIG. 9 is a fragmentary front view of the pan; and,
FIGS. 10 and 11 are views similar to FIGS. 6 and 7 showing an alternate
embodiment of the invention using a perforated sheet as a film support
element.
DESCRIPTION OF APPARATUS
Imaging systems that can be processed with the apparatus disclosed herein
are in the form of a photosensitive film sheet which, upon exposure to
actinic radiation, undergoes a chemical or physical change in exposed
areas. The film sheets may be silver halide photographic materials or
supports coated with photohardenable or photopolymerizable layers. The
supports may be paper, plastic or even metal sheets that have been
rendered photosensitive by incorporating or coating thereon a substance
sensitive to actinic radiation.
The processing apparatus shown in FIG. 1 has coupled developing, fixing,
washing and drying sections 10, 12, 14, 16. A photosensitive film sheet
such as a sheet of exposed silver halide film is advanced through the
apparatus, in a horizontal path 18, by driven nip roll pairs. Sections 10,
12, 14 have entry rolls 19,20 and exit rolls 21,22. Drying section 16 has
exit rolls 21,22.
In section 10, there are two applicators 24,26 above and a pan 28 below
path 18. Applicators 24,26 receive a developing solution from perforated
dribble bars 30,31 that are connected to the output of a pump 32. Pan 28
receives solution through a conduit 34 that is connected to a pump 35.
Overflows from applicators 24,26 and pan 28 are collected by a tank 36.
The solution is replenished through a conduct 40 and maintained at the
desired temperature by a device 42.
There are two applicators 26f in section 12. The applicators receive a
fixer solution from dribble bars 46,47 that are fed by a pump 48. Pump 48
takes suction on a tank 49. Tank 49 can be replenished with fixer
concentrate through a conduit 50 and its contents can be maintained at the
desired temperature by a device 51. A pan 28f receives solution from tank
49 through a pump 52 and a conduit 53. Dribble bars 30,31,46,47 have
perforations p (FIG. 2) and have been fabricated from tube stock of
chlorinated polyvinyl chloride.
In section 14, a film sheet advancing from fixer section 12 is flushed with
wash water from dribble bars 54 and its back side is washed with water in
a pan 28w. Bars 54 and a conduit 55 connected to pan 28w are supplied by a
pump 56 and/or with tap water. Where pump 56 is used, the water can be
maintained at the desired temperature by a device 57. The washed film
sheet then passes through dryer 16.
Referring now to FIG. 2, it will be seen that rolls 19-22 carry elastomeric
sleeves 58. Applicators 24,26 each have a screen 60 fitted into the mouth
and extending from edge-to-edge of an elongated trough 62. Each screen 60
extends lengthwise of trough 62 and has its longitudinal edges folded
inwardly to present tabs that engage inner surfaces of front and back
walls 63,64. One tab is fastened to the back wall 64. The lip along the
top of wall 63 is below the upper edge of wall 64. An integral extension
of front wall 63 forms a ramp 66 that projects downwardly into close
proximity with path 18. Ramp 66 is bent on itself to present a rounded lip
and a terminal flap 67. Ramp 66 is bent on itself to present a rounded lip
and a terminal flap 67. Ramps 66 on applicator 24 and the first applicator
26f in section 12 also project into close proximity with the adjacent
idler rolls 19.
Additionally, applicator 24 is provided with a screen 68 that has one
longitudinal edge fastened to back wall 64 and the opposed edge wedged in
the gap between flap 67 and ramp 66. Intermediate its edges, screen 68 has
a planar portion 69 that is parallel to and disposed closely adjacent path
18. Foraminous sheets 60,68 have been cut and formed from 60 mesh
stainless steel screening.
As shown in FIGS. 3 and 4, ramp 66 is shorter than front wall 63 of trough
62 and screen 60 is shorter than the ramp. The bottom wall of the trough
has drain holes 70 located beyond the ends of screen 60. In these
respects, screen 60 extends beyond the edges of path 18, i.e., is longer
than the width of a film sheet to be processed.
As shown in FIG. 5, a film sheet F can be inserted into the nip between
rolls 19,20 and then advanced over pan 28. Beforehand, pumps 32,35 (FIG.
1) and device 42 will have been activated. Developing solution is pumped
to bar 30 and pan 28 to the point where trough 62 and the pan overflow.
Some of the solution from bar 30 flows down screen 60 to ramp 66 but
mostly the solution passes through the screen and overflows into a layer
72 on ramp 66. Layer 72 falls as a curtain from the gap between idler roll
19 and the bottom of ramp 66 until film sheet F reaches that point. Then,
as shown at 74, a pool forms on the film sheet. The liquid in the pool 74
flows over the edges of film sheet F to pan 28 or directly to the bottom
of tank 36. Screen portion 69 tends to level pool 74 by spreading it away
from the center toward the edges of the film sheet. This spreading action
coupled with the motion of film sheet F agitates the solution and further
enhances the development of images. In these respects, it should be noted
that the distance between film sheet F and screen portion 69 is only about
half the distance between roll 19 and the lip at the bottom of ramp 66.
Referring to FIGS. 1, 2 and 6-9, it will be seen that pan 28 extends from a
point near roll 20 in section 10 to a point near roll 22. The pan has a
bottom wall 76, angularly disposed end walls 78 and side walls 80. Bottom
wall 76 has drain holes 77. The end walls have projecting portions 81 that
are bent back to present lips. Conduit 34 is connected to one of the side
walls 80 and discharges to a distribution housing 82 having a top wall and
side walls. Liquid flows from housing 82 through perforations 83, fills
pan 28 and overflows the lips at the ends of the pan.
Projections 81 of walls 78 have spaced notches 84 through which a thread 86
of wire or other material such as nylon is laced with the lengths between
walls 78 disposed at an acute angle with respect to walls 80. The ends of
thread 86 are fastened or anchored in outermost notches. Extending from
lip-to-lip of the pan, the thread lengths provide a support for a film
sheet being transported along path 18.
In an alternate and preferred embodiment illustrated in FIGS. 10 and 11, a
perforated metal sheet 87 is used instead of the thread 86 to provide
support for a transported film sheet. The preferred material for the sheet
87 is type 316 stainless steel twenty gauge sheeting having perforations
of one-eighth inch diameter staggered at three-sixteenth inch centers,
resulting in forty percent open area. It has been found that using the
metal sheet 87 as a support rather than the thread support tends to
produce a cleaner back side on the processed film. The sheet 87 extends
lip-to-lip of the pan to provide a support for a film sheet being
transported along the path 18. In FIG. 11, the end walls 78 of the pan 28
extend at substantially a ninety degree angle to the bottom wall 76
thereof. It should be noted in the embodiment shown in FIGS. 10 and 11
that drain holes 77 are still provided in the bottom 76 of the pan, but
the drain holes are omitted from FIG. 10 for clarity of illustration. The
sheet 87 has flaps 87f which closely fit to the walls 78 of the pan. The
top of the housing 82 lies close to (or may abut, if desired) the
undersurface of the sheet 87. The sheet 87 may be attached to the pan by
any suitable means, as by spot welding.
The apparatus is readied for operation by activating pumps 32,35,48,52 as
well as the supply of water to section 14, energizing elements 42,51,57,
activating dryer 16 and energizing the drive for rolls 20,22. The liquids
are maintained at a constant temperature which, depending on the type of
photosensitive film sheet being processed, is in the range of
50-125.degree. F. Thus, in some processes, the devices 42,51, 57 are
heaters and, in others, it will be necessary to cool the liquids below
room temperature. When the apparatus is ready, a film sheet can then be
inserted into the nip between the first pair of rolls 19,20 and advanced
along path 18. Developing solution flows from applicators 24,26 to the
image-bearing surface of the film sheet. The solution is spread and
agitated by the screen portion 69 on applicator 24. The back side of the
film sheet is wet by solution splashed thereto from pan 28. In section 14,
both sides of the film sheet are washed. When the apparatus is
inactivated, liquids remaining in the troughs and pans flow out through
the drain holes 70,77.
The apparatus is particularly useful in the processing of wide films having
an emulsion of a silver halide coated on one side. A typical example is a
film used in aerial photography and provided with an antihalation layer on
its back side. With the apparatus disclosed herein, such films can be
processed effectively, with a high degree of transverse and longitudinal
uniformity, in total access periods of about thirty seconds. An added
advantage is that the developed films also exhibit increased maximum
density and a higher gradient.
It has been noted above that the ramps 66 terminate in close proximity to
path 18 and that the ends of the ramps on two of the applicators are
closely adjacent idler rolls 19. In tests with the wide films mentioned
above, having thicknesses of 4-7 mils, the distance between rolls 19 and
the first ramps 66 in sections 10,12 was 20 mils and the flows of liquids
were such as to fill the gaps without creating pools on the ramps. The
lips of all ramps and the planar portion 69 of screen 68 were spaced at 15
mils from path 18. All liquids were heated to a temperature of about
110.degree. F. Momentary lingering of spent or stale developer along the
center of the film sheet was avoided by the spreading and agitating
activity of the screen 68 on applicator 24. Thus, the developer first in
contact with the film sheet is renewed continuously and this renewal
minimizes density irregularities due to aging or exhaustion of the
processing liquid.
Uniformity of development longitudinally of the film is enhanced by the
manner in which the screens 60 and layers 72 break up flow patterns such
as those from the spaced perforations p in the dribble bars. Irregular
development patterns transversely of the films are avoided both by
uniformity in the layers 72 flowing from the applicators and by activity
of the screen portion 69 below the applicator 24.
As the developer in pool 74 (FIG. 5) flows over the edges of the film
sheet, it has a tendency to wet the back side irregularly adjacent its
edges. If allowed to dry and oxidize, the back side would become spotted
and stained as a consequence of such wetting. With the apparatus disclosed
herein, the back of the film sheet is wet sufficiently that it does not
have an opportunity to dry before reaching fixer section 12 where any
developing solution on the back side is neutralized by the fixing solution
in pan 28f. Antihalation dyes are also removed by the fixer solution. In
section 14, residual salts formed from the processing liquids are washed
away. The angularity of the spaced reaches of support thread 86 (FIGS. 6
and 9) and their wiping action across the back side avoid the possibility
of visible striations on any developed film which had an antihalation
layer or the like on its back side.
Although two applicators have been shown in each of sections 10,12, there
are photosensitive film sheets and processes with which but a single
application of developer and/or fixer is required. While the apparatus has
been described in connection with the processing of conventional silver
halide films, it is also useful in the applications of tanning solutions
or other processing liquids to imagebearing, photosensitive film sheets.
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