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Description  |
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BACKGROUND OF THE INVENTION
This invention concerns the automatic replenishment of chemical
compositions consumed during photographic processes in which the
compositions are used to develop photographic film.
In a photographic process, the latent image in exposed photosensitive
emulsions is developed. In the course of the process, the compositions
which chemically convert the latent image into a developed picture are
consumed, and must be replaced. In black-and-white photography, the
developer is consumed in reducing silver halide to metallic silver to
create the image.
In color photography, the developer, such as CD-2 (a p-phenylenediamine
derivative developer sold by Kodak), hydroquinone and the like, reduces
the silver halide on the film to metallic silver, causing the color
couplers to react to produce the colored dyes. Additionally, a bleach
solution, such as sodium ferricyanide or the like, is used in oxidizing
the metallic silver image to silver halide for subsequent solubilization
in a fix solution, such as sodium or ammonium thiosulfate (Hypo) or the
like, is used to dissolve the silver halide from the film. Other chemical
solutions are also used in color photography processes, including stop (or
short stop) baths, which are generally acidic solutions (typically acetic
acid and the like, of a pH of 5.5 or less), are used instead of a rinse
after development, and have the purpose of abruptly stopping development,
hardner solutions (e.g. alkaline formalin), conditioner solutions, and the
like.
If the photographic developing process is to proceed without interruption,
it is necessary to make continuous measurements of the concentrations of
the chemicals in the solutions and replenish the solutions with the
depleted chemical in response thereto. Prior art photographic processing
systems, however, have generally been constrained to replenish on a batch
basis, or if continuous replenishment was performed it was done by making
continuous measurements of the concentration of each chemical being
consumed and replenishing the depleted chemicals on the basis of the
measurements associated therewith. One such continuously operating system
is disclosed in Schumacher U.S. Pat. No. 3,529,529 wherein the
replenishment apparatus draws a sample of developer solution, performs a
potentiometric titration to determine the concentration of halogen
therein, and adjusts the flow rate of the developer replenisher in
response thereto. This method is somewhat awkward and complicated in that
titration solution must be stored and transferred, and the titration
itself must be performed.
Other prior art systems as shown for instance in Hixon et al. U.S. Pat. No.
3,472,143 have replenished photographic chemicals in response to infrared
sensing signals proportional to the area of film being processed. Still
other systems as shown in Street et al. U.S. Pat. No. 3,554,109 have
measured image density variations to control simultaneous replenishment of
developer and fixer solutions. Other examples of prior art photographic
replenishment systems are shown in U.S. Pat. Nos. 3,334,566 and 3,680,463.
All of these prior art systems, however, are considered to be awkward,
inefficient, or impractical for commercial use in typical contemporary
photographic processing laboratories. Further, most of the prior art
systems applied to replenishment of single solutions used predominately in
black and white film processing. Virtually no such work has been performed
for color processing. Accordingly there has existed a need for an
improved, simple, economical automatic process for replenishing the
chemical compositions consumed during photographic processes.
Further, most processing laboratories are of a relatively small magnitude,
and cannot afford to place a process controller on every process solution
in the plant. A further need therefore exists for a method and means for
controlling replenishment of the developing process chemicals without
requiring individual process controllers of each solution.
SUMMARY OF THE INVENTION
The invention is generally directed to an improved method of and apparatus
for replenishing the chemical compositions consumed in a photographic
process, and specifically to an apparatus and method of replenishing all
of the solutions in the process by a simple analytical process involving
only a few of the compositions to be replenished.
The process of the invention is an improvement over the prior art processes
because it is a simple, relatively uncomplicated, and accurate measuring
process, and it eliminates the need for and expense of individual process
controllers for each composition used in the process. Thus, plural
solutions can be replenished on the basis of a sample taken from only one
of the solutions.
The improved replenishing apparatus and process will be discussed in the
context of, but is not limited to, a five step process which uses the
following solutions: color developer solution, stop bath solution,
hardener solution, rehalogenating bleach solution, and fix solution.
Alternatively, the improved replenishing process could be used in
conjunction with a three step photographic process, such as a process
using only a developer, bleach-fix, and stabilizer, wherein only the
developer is monitored. It is also applicable to any other photographic
process, as long as the replenishment is done in accordance with the
principles of the invention expressed herein.
The process of the invention has evolved in part because of the discovery
that the amount of imagery processed in the exemplified film developing
process is related to the halogen activity, i.e., the bromide level in the
bleach solution, when the bleach is a rehalogenating bleach. It was also
discovered that the amount of bulk processed in the film developing
process is related to the silver activity, i.e., the silver level, in the
fix solution. Further, it was discovered that the replenishment
requirement of all of the image dependent solutions could be related to
the bromide level in the bleach solution, while the replenishment
requirement of all of the bulk dependent solutions could be related to the
silver level in the fix solution. In the exemplary photographic developing
process, the developer and the bleach solutions are the image dependent
solutions, while the stop bath, hardner and fix solutions are the bulk
dependent solutions.
For the purpose of the disclosure herein, the terms image dependent,
imagery dependent and image related are intended to mean that the
chemicals are consumed, in the processing of the film, on the basis of the
amount of image or imagery present on the undeveloped film. Bulk
dependent, bulk related, and non-image or non-imagery dependent means that
the chemicals are consumed, in the processing of the film, on the basis of
how much film is being transported through the solution tanks over a given
period of time.
The term chemical activity is intended to mean the presence or absence of
active chemicals, including ions, in the classical physical chemistry
definition, in the solutions. For example, the bleach solution converts
the silver image in the film to silver halide; usually silver bromide. As
the film is processed, the bromide in the solution is consumed to form
silver bromide, with a consequential reduction in the level or
concentration of the bromide, while the bleach is reduced in oxidizing the
free silver to silver ion in situ. Thus, there are several active
chemicals in the bleach solution. By monitoring the bromide, for example,
the chemical activity of the solution may be determined. But, the chemical
activity of the solution might also have been analyzed on the basis of the
other bleach chemicals.
By the process of the invention samples of the bleach and fix solutions are
extracted and electro-chemically analyzed to determine the chemical
activity therein, which are related to the amount of imagery and bulk
being processed. But other solutions could be monitored. For example, the
developer could be monitored to determine replenishment for the bleach as
well as the developer. The rates of replenishment of all of the
compositions are then adjusted based on these values. Thus, by only
replenishing the image dependent solutions on the basis of imagery, a
savings is realized over mere bulk replenishment which results in new
chemicals being added whether needed or not. A further savings is realized
because of the elimination of the need for process controllers for every
solution and/or for every solution ingredient, since the replenishment of
all of the solutions can be done with a minimum of controllers. In the
exemplary process, only two process controllers are needed.
Also, provisions may be made for the regeneration of the bleach solution
and the recycling of the fix solution, as additional measures resulting in
further economic gain. The performance of these steps can be economically
controlled and monitored in a manner similar to the replenishment process
of the invention.
It is therefore an object of the invention to provide an improved method of
replenishing the chemical compositions consumed in a photographic process
by a simple analytical process on only some of all the compositions to be
replenished.
Other objects and advantages of the invention will be apparent from the
following description, the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows, diagrammatically, a schematic illustration of a typical film
developing process, including the measuring of certain compositions used
in the process to determine if the process compositions should be
replenished and/or treated in any other manner, in accordance with the
teachings of the invention, and
FIGS. 2a-f are charts showing the variations in the concentration of, and
additions to, the process solution over a common period of time, and
depending upon whether film or leader material is being processed.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 generally illustrates a color film developing process employing an
automatic chemical replenishment system in accordance with the invention.
In the developing process, film 10 is passed through tanks containing the
developing chemicals, which results in developing of the latent image in
the exposed film, including a developer tank 11, a stop bath 12, a hardner
solution tank 13, a bleach solution tank 14, and a fix solution tank 15.
As film 10 continuously passes through tanks 11-15 and is developed, the
chemical solutions in the tanks are consumed and must be replenished.
Replenishment tanks 21-25, and appropriate pipes, 26-30, are provided for
the purpose of replenishing the chemicals consumed in the developer, stop
bath, hardner, bleach, and fix solutions, respectively.
It is the control of the feeding of the replenishing solutions to the
processing tanks 11-15 that is the subject matter of this invention. In
the past, the valves which controlled the flow of the replenishing
chemicals were either individually hand-set or individually controlled by
an individual process controller monitoring each respective solution. The
process of the invention is based, in part, upon the discovery that the
need for replenishment of all the solutions (in the exemplary photographic
process) can be sensed and controlled by monitoring two of the solutions.
By monitoring the bromide level of the bleach, the replenishment of both
the bleach and developer can be controlled, as both are image dependent
solutions. By monitoring the silver level of the fix solution, the
replenishment of the stop bath, hardner, and fix can be controlled, since
all those solutions are bulk dependent solutions.
In order to monitor the bromine and silver concentration in bleach tank 14
and fix tank 15, respectively, portions of the solutions in the tanks are
continuously circulated through closed loop systems 31 and 32. Each of the
loops 31 and 32 comprises piping 33 and 34, respectively, pumps 35 and 36
respectively, and process controllers 37 and 38, respectively. The process
controllers continuously sample and analyze the solutions, as they are
circulated by pumps 35 and 36, to determine the chemical activity, such as
the bromide and silver levels in the respective solutions.
An example of a process controller which preferably is employed to monitor
the bromine and silver concentrations of the type disclosed in Kelch et
al. U.S. Pat. No. 3,770,608, which annalyzes a sample of the solution
being monitored by comparing the sample with a standard process solution
by linear nullpoint potentiometry. For this purpose the controller employs
a pair of sensing probes, each of which is equipped with a solid state
specific ion sensing membrane. For measurement of silver ion activity the
controller employs silver sulfide membranes having a metallic silver
backing, and for measurement of bromide ion activity the controller
employs silver-backed silver bromide membranes, all as described in U.S.
Pat. No. 3,770,608 and a related pending patent application Ser. No.
378,025 filed July 10, 1973.
When process controller 37 determines that the bromine level of the bleach
solution within loop 31 is below the standard or reference level, the
controller generates a control signal which causes a bleach replenisher to
flow from tank 24 to tank 14. Simultaneously therewith a developer
replenishing solution is caused to flow from tank 21 to tank 11.
As shown in the figure, when an analysis of a sample of the bleach
circulating through loop 31 indicates a low bromine level, and thus a need
for replenishment of the image dependent solutions, a signal leaves
process controller 37 via line 41 and is transmitted by lines 42 and 43 to
control valves 44 and 45 causing the valves to open and feed replenishing
solution to the respective developing tanks. The exact flow rates of the
replenishment solutions will vary according to the kinds and types of
chemicals involved, since all bleaches and/or developers are not consumed
at the same rates, and so need not be replenished at the same rates. The
same will be true with the stop bath, hardner and fix solutions. Thus, the
solutions are all replenished at relative rates. This relationship can be
preset into the valves, so that although they receive the same signal,
they will operate at different flow rates.
Once the chemical activity has returned to normal or standard level, the
signal will cease, and valves 44 and 45 will close. Pumps 46 and 47 are
provided to pump the replenishing chemicals from replenishing tanks 21 and
24 to developing tanks 11 and 14 respectively. Pumps 46 and 47 could also
be controlled by controller 37, such that, when valves 44 and 45 are
opened, pumps 46 and 47 are turned on, and, when valves 44 and 45 are
closed, pumps 46 and 47 are turned off. Alternatively, replenishment
solution could be continuously fed to the developing tanks, with pumps 46
and 47 running continuously, while the opening of valves 44 and 45 would
be adjusted according to the level of chemical activity in bleach tank 14
as measured by controller 37 in loop 31. Thus, there would always be some
amount of feed, but provision could be made to shut down the pumps if the
rate became zero. The control valves need not be of any particular design
and thus could be solenoid activated, pneumatic, or the like.
The fix solution in loop 32 would be monitored in the same manner as is the
bleach solution is monitored in loop 31. A signal 50 from process
controller 38 would follow lines 51-53 to valves 54-56, to actuate and
control the opening and closing of the valves in lines 27, 28, and 30 from
the non-image dependent replenishment solution tanks 22, 23, and 25, in
the same manner as valves 44 and 45 are controlled. Pumps 57-59 are
provided to pump the replenishing chemicals, and may be controlled
similarly to pumps 46 and 47.
It may be necessary, in some instances, to provide an interlock between the
image dependent controller and the bulk dependent controller which, under
certain conditions, will turn the control of the bulk dependent solutions
over to the image dependent controller. The reason for this is that, when
a large amount of leader is being processed, there is carry out of the
bulk dependent chemicals, especially the fix chemicals, by the physical
movement of the leader through the bath. Although these chemicals are
normally replenished by the bulk control response when the image material
begins passing through the processing equipment, when a large amount of
leader is processed, more chemicals are removed than the bulk replenisher
normally will add. This is because the bulk dependent process controller
usually responds to an increase in chemical activity in the bulk dependent
sample, e.g., the silver activity in a sample of the fix solution.
As leader passes through the fix tank, silver is carried out, along with
the fix chemicals. Instead of the silver activity increasing and the lost
fix chemicals being replenished, the silver activity level continues to
decrease. The bulk dependent process controller remains unresponsive until
film again begins to pass through the process. Meanwhile the level of fix
chemicals has become so low that the proper level can just about never be
reached. Thus, the concentration of the solution will never catch up. An
example of a large amount of leader being processed is a television
station news department where the equipment will be allowed to run with
only leader material passing through so that the equipment will be ready
when an important or recent news story is received which needs immediate
processing.
In order to prevent the bulk dependent solution concentrations from getting
too low, the bulk and image dependent controllers are interlocked. An
arbitrary minimum which represents a relatively large amount of leader
material is being processed is assigned for the chemical activity of the
bulk dependent sample. Below that point the replenishment of the bulk
dependent chemicals is under the control of the image dependent
controller, while above that point the control is performed in a normal
manner by the bulk dependent controller. When a minimum silver activity
level, for example, is reached, the control of the bulk dependent
solutions is done by the image dependent controller. While chemicals from
the image dependent solutions are also carried out by the leader material,
the image dependent controller is usually designed to respond to a
decrease in the chemical activity, as contrasted to the bulk dependent
controller which responds to an increase. Thus, the carry out of chemicals
causes a decrease which the image dependent controller will respond to,
and all of the solutions will be replenished at least to the extent of
carry out.
In addition to the replenishment of the bleach solution it may be desirable
to regenerate the bleach by an oxidation apparatus 60 which may be
electrolytic cell or the like located within the bleach recycling loop 31.
An example of such a bleach regeneration apparatus is disclosed in Jensen
et al. U.S. Pat. application Ser. No. 420,699, filed Nov. 30, 1973, which
disclosure is incorporated herein by reference. Since the need for bleach
regeneration is related to the need for replenishment of bleach solution,
the operation of bleach regenerator 60 may be controlled by process
controller 37, so that when the bleach is replenished it is regenerated as
well, thus reducing the amount necessary for replenishment.
In a manner similar to the regeneration of the bleach by bleach regenerator
60, a cell 62 may be provided in loop 32 to recover silver from the fix
solution, thereby allowing continued recycling of cell 62, which may be an
electrolytic cell or the like, is controlled by a signal on line 63 from
controller 38 so that it operates only when it is needed, i.e., when the
bulk dependent chemicals need replenishment, because of the high level of
chemical activity, e.g., a large amount, or above a certain relative
amount, of silver.
An example of a process being controlled in accordance with the teachings
of the invention is set forth as follows:
EXAMPLE
Film material, comprising leader material and 16 mm and 35 mm color film,
was developed by running it through a developing apparatus similar to that
diagrammatically illustrated in FIG. 1. The film material (FIG. 2-a
indicates the kind) was run at a relatively constant 90 feet per minute
for almost nine hours, and the replenishment flow rates, based on peak
film demand, which in this case was the 35 mm film, were as follows:
SOLUTION REPLENISHMENT FLOW RATE
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Color Developer 0.220 1/min.
(CD-2; a p-phenylene
diamine derivative
developer sold by Kodak)
Ferricyanide Bleach
0.035 1/min.
Stop Bath 0.020 1/min.
Hardner 0.010 1/min.
Fixer 0.145 1/min.
______________________________________
FIGS. 2 a-f are charts of some of the various solution activities, and
additions to those solutions in response to the activities, as a function
of time. The chemical activity in the image dependent sample which was
monitored was the bromide level in the bleach solution (FIG. 2-c), and the
controlling levels of activity were concentrations of bromide of between
17.0 and 17.2 grams per liter. The chemical activity of the bulk dependent
solution which was monitored was the silver activity in the color fixing
bath (FIG. 2-e), and the controlling level of silver activity were between
about 1.0 and 1.3.
When the bromide level in the bleach decreased below 17.0 g/l., the
controller (FIG. 2-b) caused the bleach and developer chemicals to be
replenished, and the replenishment continued until the bromide level
reached approximately 17.2 g/l, at which time the controller caused the
replenishment flow to be shut off. The chemical activity in the developer
solution (FIG. 2-d) could have been the basis for the operation of the
image dependent process controller, since its activity was almost exactly
the same as the bleach.
The control of the bulk dependent solutions was performed in a manner
similar to the image dependent control, but on the basis of the chemical
activity of a bulk dependent sample. FIG. 2-e shows the variations in the
silver activity in the color fixing bath, with the process controller
causing solution additions when the silver activity reached approximately
1.3, while ceasing addition when the level reached 1.0. FIG. 2-f shows
that the control of the silver electrolysis cell, to allow the fix
solution to be recycled, is the same as the solution additions, since the
electrolysis causes a decrease in the silver activity.
The problem of running a relatively large amount of leader is illustrated
in FIG. 2-e, where the number 70 designates an arbitrary minimum (0.8)
which represents a relatively large amount of leader being processed. When
the minimum point was crossed, the bulk dependent additions were
controlled by the image dependent controller until at point 72, the
minimum concentration was again achieved and the bulk dependent controller
resumed normal control.
While the method herein described, and the form of apparatus for carrying
this method into effect, constitute preferred embodiments of this
invention, it is to be understood that the invention is not limited to
this precise method and form of apparatus, and that changes may be made in
either without departing from the scope of the invention.
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