GB2051617A

GB2051617A - Development of films in an automatic film processor

Info

Publication number: GB2051617A
Application number: GB8019607A
Authority: GB
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1979-06-27
Filing date: 1980-06-16
Publication date: 1981-01-21
Also published as: DE3024000A1; DE3024000C2; DK273180A; GB2051617B; FR2459998B1; NL8003361A; JPS565544A; JPS57972B2; FR2459998A1

Abstract

In a film processor developing tank 6 the level of developer is gradually increased by a metering pump 5 to compensate for a drop in activity of the developer. An overflow 1 is provided to a supplementary tank 4. A solenoid valve 3 between the overflow 1 and the supplementary tank 4 is closed when a film is being developed and the pump lifts developer from the supplementary tank 4 to the main tank 6. <IMAGE>

Description

SPECIFICATION Development of films in an automatic film processor The present invention is concerned with a method and apparatus for the development of the photographic films in a film processor.

In the development of photographic films the factors which may affect the density of the films are: (1) activity of the developer, (2) temperature of the developer, (3) time of development, (4) degree of agitation of the developer. Conventionally such conditions are maintained as constant as possible. However, (a) it is very difficult to keep the activity of the developer constant because the activity changes momentarily along with the exhaustion of the developer due to the development of the exposed films.Even if a large amount of the developer is used and the developer is agitated as often as possible to diminish the change of the activity, it is almost impossible to keep the activity of the developer constant, to attain uniform development of photographic films, since the activity changes momentarily at all parts of the films, e.g. at the leading end or at the trailing end of the films.

In addition, (b) it seems to be advisable to decrease gradually the passing speed of the films through the developer according to the degree of exhaustion of the developer, but the suitable control of the speed of the films is very difficult. Moreover, (c) it is almost impossible to control temperature that is, to vary the temperature of the liquid in contact with the film appropriately according to the change of the activity of the liquid during development.

Therefore, the method of the addition of replenisher in order to recover the activity which has so far been applied to the film processor may be done by correcting only the average activity of the circulating developer, but with only such a correction of the activity af the developer it has been impossible to correct the difference of the concentration of the developer from the leading end to the trailing end of the film to be treated, as described above. Especially in the development of a film of a large size the difference of the contract of the film at the leading part and at the trailing part of the film could not be avoided to occur.

According to one aspect of the invention there is provided a method for the development of an exposed photographic film in an automatic film processor wherein the immersion time of the film in developer is gradually increased from the leading end towards the trailing end of the film by gradually varying the developer liquid level during feeding of the film into the developer in the automatic film developing processor which can develop by passing and carrying the film through a developing tank containing developer.

According to another aspect of the invention there is provided a film developing apparatus in which the film is developed by carrying the exposed photographic film through developer, the apparatus including a developing tank, an overflow tube arranged so as to maintain the liquid surface at a level lower than the upper edge of the developing tank, a pump which circulates the overflow liquid from the overflow tube back to the developing tank, a solenoid valve and a supplementary tank arranged between the overflow tube and the pump, and a control device which detects the feeding of the film into the developing tank and closes the solenoid valve, whereby the liquid surface level in the developing tank is gradually increased during the development of the film.

To help understanding of the invention a specific embodiment thereof is now described by way of example and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a developing tank used in this embodiment and Figure 2 shows a sectional view of the developing tank and a fixing tank.

As shown in Fig. 1 the developing tank 6 of the film processor has a supplementary tank 4 attached to it. Overflow tubes 1 and 2, with a lower overflow level 7 and with a higher overflow level 8 respectively, are included in the developing tank 6. A solenoid valve 3 is arranged between the lower overflow tube 1 and the supplementary tank 4 to circulate the developer with a metering pump 5. Inside of the developing tank, and indeed inside the adjacent fixing tank 14, as shown in Fig. 2, a film carrying device is arranged which consists of a combination of rollers 9, 10.

As shown in Fig. 2, an exposed film 1 2 is carried into the developing tank by a roller 1 3 and a film guide 11 from a feeding tray and then transported into the adjacent fixing tank 14 by the rollers 9, 10.

Under the normal condition, the solenoid valve 3 is open, so that the liquid surface in the developing tank is kept at the level determined by the lower overflow tube 1. When an exposed film to be treated is carried into the developing tank under such condition, and the solenoid valve 3 is closed according to a signal, for example, of a microswitch (not shown) arranged in the feeding part, the overflow of the developer stops because the flow way from the lower level overflow tube 1 to the supplementary tank 4 is closed while the metering pump 5 continues circulating the developer in the supplementary tank 4 into the developing tank 6, so that the liquid surface in the developing tank 6, increases gradually.Therefore the distance which the film to be treated passes through the developer increases gradually from the leading end towards the trailing end thereof and correspondingly the time of development gradually increases. Thus, the decrease of the thorough activity of the developer during the development of an exposed film is corrected by increasing the time of development.

Further a stable development can be attained by selecting appropriately the carrying speed of the film and the discharge rate of the metering pump, even in the treatment of a long film.

The higher overflow tube 2 is arranged to prevent an accidental overflow of the developer from the upper edge of the developing tank 6 when the film to be treated is so long as to require a very long time for feeding.

Because the elevation of the liquid stops when the liquid surface reaches the level of the higher overflow tube 2 further correction cannot be expected, but if the capacity of the developing tank is determined so as to attain a sufficient elevation of the liquid surface according to the longest film among those to be treated, there will be no trouble in practical use.

As soon as the trailing end of the film has passed the microswitch for detection of feeding, the signal from the switch stops and the solenoid valve 3 opens, so that the liquid surface is lowered to the upper edge level of the overflow tube 1 and returns to the normal level. Because during this process it usually takes some time for the trailing end of the film to reach the surface of the developer after passing the microswitch, it is desirable to apply a delay relay to maintain the elevation of the liquid surface.

The return of the liquid surface is required to be completed before the leading end of the film reaches the liquid surface at the feeding side, or after the whole length of the film has completely passed through the liquid and the trailing end of the film has separated from the liquid surface. The reason is that the decrease of the liquid surface while only a part of the film is carried out from the developer causes certainly an insufficient development of the part immersed in the liquid, which makes this arrangement meaningless.

The application of the procedure of the apparatus is not limited to the example described above, but, for example, the following procedure may also be employed. That is, the surface of the developer is kept increasing gradually from the upper edge of the lower overflow tube 1 toward the upper edge of the higher overflow tube 2 and the feeding of the film starts earlier by the time required for feeding of the film to be treated determined on the basis of its length than the time when the liquid surface reaches the upper level of the higher overflow tube 2. Namely, the elevation has already begun before the start of feeding of the film and the trailing end of the film is immersed into the developer just when the liquid surface reaches the upper limit; the effect is the same as that in the example described above.

As described above in detail this embodiment of an automatic film processor according to the invention enables reasonable correction of the decrease of the thorough activity of the developer at the trailing end of the film due to the exhaustion of the developer, with an easy procedure. This invention is practically very useful.

Claims

1. A method for the development of an exposed photographic film in an automatic film processor wherein the immersion time of the film in developer is gradually increased from the leading end towards the trailing end of the film by gradually varying the developer liquid level during feeding of the film into the developer in the automatic film developing processor which can develop by passing and carrying the film through a developing tank containing developer.

2. A method for the development of a film as claimed in claim 1 wherein the surface of the developer is allowed to return to a standard level after film feeding into the developer is completed and yet before the leading end of the next film reaches the liquid surface at the feeding side.

3. A method for the development of a film as claimed in claim 1 wherein the surface of the developer is allowed to return to the standard level after the whole length of the film has completely passed through the developer.

4. A film developing apparatus in which the film is developed by carrying the exposed photographic film through developer, the apparatus including a developing tank, an overflow tube arranged so as to maintain the liquid surface at a level lower than the upper edge of the developing tank, a pump which circulates the overflow liquid from the overflow tube back to the developing tank, a solenoid valve and a supplemetary tank arranged between the overflow tube and the pump, and a control device which detects the feeding of the film into the developing tank and closes the solenoid valve, whereby the liquid surface level in the developing tank is gradually increased during the development of the film.

5. A film developing apparatus as claimed in claim 4, wherein the pump is a metering pump.

6. A film developing apparatus as claimed in claim 4 or claim 5 wherein detection of the feeding of the film into the developing tank is performed by a contact switch attached to the feeding part.

7. A method for the development of an exposed photographic film substantially as hereinbefore described with reference to the accompanying drawing.

8. A film developing apparatus substan tially as hereinbefore described with reference to the accompanying drawing.