Photography – Fluid-treating apparatus – Having fluid-circulating means
Reexamination Certificate
1998-10-06
2001-01-23
Rutledge, D. (Department: 2851)
Photography
Fluid-treating apparatus
Having fluid-circulating means
C396S636000
Reexamination Certificate
active
06176628
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the processing, and particularly but not exclusively the washing or stabilizing, of photographic material, usually already exposed, in which the material passes through a plurality of stages, preferably in a counter-current mode.
BACKGROUND OF THE INVENTION
Photographic material as referred to herein is understood to be generally planar, may comprise film or paper, may produce a black-and-white or color image, and may be in a continuous web form or may comprise discrete sheets.
Silver halide photographic materials are well-known, and are processed to generate a silver or dye image via a development stage followed by a series of baths to stabilize and provide permanence to the image. Such baths convert and remove unwanted materials from the coated photographic layers which would either interfere with the quality of the final image or cause degradation of the image with time. In typical color systems the development stage is followed by a bleach stage to oxidize the developed silver to a form which can be dissolved by a fixing agent in the same or a separate bath. Such silver removal stages are then followed by a washing stage using water, or other wash solution, or a stabilization stage using a stabilizer solution. For convenience, this last-mentioned stage will hereinafter be referred to generically as “washing.” Such stages remove residual chemicals and may also include conversion reactions between stabilizer solution components and materials within the coated layers. These stages are required to provide the required degree of permanence to the final image.
In many cases, particularly in small-scale “minilab” or “microlab” equipment, the wash stage is performed in a multi-tank arrangement. Usually the replenishment of this stage, which keeps the concentration of substances removed from the photographic material at a constant and sufficiently low level, is carried out by adding fresh wash solution to the final tank of the sequence and arranging over-flow from the final tank to flow into the previous tank and so on, the overflow from the first tank of this stage being then discarded as effluent. This is referred to as a “counter-current” mode. This arrangement allows significantly lower amounts of solution to be used compared with one or two tanks especially when these are replenished separately.
In all of these arrangements, processing is carried out with the photographic material immersed in a tank of solution, even though many, though not all, photographic materials are sensitized with an emulsion only on one side thereof.
In a modern minilab a typical wash replenishment system might use around 200 cm
3
of replenisher per m
2
of sensitized material processed in a three or four-tank counter-current arrangement. The time the processed material spends in each tank is typically 20 to 25 seconds during which time an equilibrium is established between the concentration of substances in the coated material and the seasoned (steady-state) concentrations in the wash solution. The total time for this stage typically varies from 60 to over 100 seconds.
U.S. Pat. No. 5,365,300 discloses a process for the treatment of photographic material with a bath containing at least one processing material, in which, after the treatment bath, the photographic material is guided upwards through an ideally preferably vertical compartment which closely surrounds the material which is washed from above by water flowing under gravity in counter-current to the material. The wash water is arranged to carry chemicals off the material into the bath for re-cycling.
It is desirable to process photographic material more rapidly, and in particular to reduce overall wash times by several factors, for example to about 20 seconds as compared to 100 seconds, whilst reducing overall replenishment rates. Reduction of the path-length of the wash section of the process, for example, will shorten the time taken, for a given transportation speed of the material being processed. This latter parameter is usually constrained by the demands of the previous tanks. Unfortunately, simply reducing the number of counter-current tanks involved, while achieving the goal of shorter path-length, would require a significantly increased replenishment rate to achieve the same seasoned concentration (steady-state concentration) in the final tank from which the sensitized material emerges before being introduced to the drying stage.
It is also desirable to minimize the effluent from the processing. This is advantageous not only for the protection of the environment, but also to the operator, especially of mini- and micro-labs, in terms of having less solution for disposal.
SUMMARY OF THE INVENTION
It has been found that by guiding photographic material along inclined surfaces, the total processing time and quantity of processing solution, and thus effluent, can be co-optimized to minimum values.
In accordance with one aspect of the present invention, there is provided apparatus for processing photographic material, comprising a plurality of successive processing regions, each of which is defined by a surface inclined to the horizontal and disposed between a spaced-apart pair of guide means arranged to direct the material from one region to the next over the inclined surface, and means for supplying processing solution to at least one of the regions so that it flows along the associated surface beneath the moving photographic material, thereby to effect the processing.
Preferably, at least one of said guide means comprises a set of rollers through which the photographic material is arranged to pass.
Preferably, the photographic material is driven up the inclined surfaces, with the processing solution flowing down under gravity.
The angle of inclination of the surface to the horizontal is preferably between about 10° and 80°, more preferably between about 30° and 50°, and most preferably is between about 40° and 45°.
It has been found by mathematical modeling that reduction of the time in each processing region may be compensated by optimizing the number of regions, without requiring the achievement of an equilibrium state between the sensitized material and the seasoned (steady-state) condition of every region in the sequence. It is important, however, to achieve this equilibrium in the final region. Thus, advantageously, the length of the inclined surface in at least one of the processing regions is different from that in at least one other of the regions, whereby the residence time of the material is different in each of those regions. Preferably, the length of the inclined surface, and thus the residence time of the material, is longer in the final processing region in the direction of movement of the material than in any one of the preceding regions.
The material may pass substantially unidirectionally, that is to say with respect to the horizontal, through the successive regions, and the inclined surfaces of the regions may extend substantially end-to-end.
Each inclined surface may be substantially planar, and may be at the same angle of inclination. Alternatively, the surface in at least one, and preferably in each, region may be at least partially curved, for example to provide an immersion portion for the photographic material at the beginning of each region.
The processing regions may be all arranged to wash the photographic material, and the apparatus may comprise at least one further stage for performing at least one other processing step. The further stage may comprise a further processing region that extends substantially horizontally adjacent at least one end of said inclined surfaces, preferably in which the material is immersed.
In accordance with a further aspect of the present invention, there is provided a method of processing photographic material, which may be exposed, wherein the material is passed through at least two successive processing regions formed by inclined surfaces between respective spaced-apart guide means, wherein processing solution is supplied to at le
Adam Henry H.
Earle Anthony
Wells Leslie R.
Eastman Kodak Company
Pincelli Frank
Rutledge D.
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