1. Field of the Invention
The invention relates to an apparatus for developing photographic material.
2. State of the Art
During the processing of customer orders in photographic developing or processing laboratories, exposed film is developed by wet chemical methods. The exposed film is typically in the form of a negative. The developed negatives are then copied or printed by being projected onto photographic print material. This material is often photographic paper. The exposed photographic paper is also developed by wet chemical methods. If the photo paper is in the form of a long strip, as is the case in high-capacity labs, it is partitioned into individual pictures. These partitioned pictures of the customer order are put together and packaged for return to the customer.
The apparatuses that contain the baths for the wet chemical development are known as film or paper processors. The volume of such wet chemical baths in the processors depends substantially on what throughput (number of developed pictures per unit of time) the particular user, usually the processing lab, seeks to achieve. For the sake of simplicity, only paper processors will be discussed hereinafter. For high throughput, the distance through the paper processor must be correspondingly long so that many pictures can be located in the paper processor simultaneously. By having continuous transport on one hand and a relatively high transport speed on the other, the passage time for the paper through the paper processor will match the length of time necessary for the development (which, of course, is predetermined). The result is a relatively large-volume baths and therefore, large-volume paper processors.
In order to avoid the large-volume baths, paper processors with small-volume baths have been proposed, for instance in U.S. Pat. Nos. 5,179,404, 5,270,762, 5,309,191 and 5,311,235. It is also important for the developing fluid in the baths to be "fresh" to ensure that the developed paper prints all have the same quality standard. As a consequence, the small-volume baths have to be changed or replenished periodically. Rapid motion of the wet chemical baths has proven to be beneficial. This motion results in fresh developing fluid repeatedly coming into contact with the paper to be developed. The complete replacement or replenishment of the baths must be performed more often in a small-volume bath than in larger-volume baths.
Small-volume baths and comparatively small-volume processors, as a rule, have a very narrow conduit. This conduit extends from the inlet through the interior of the processor to the outlet. The photo paper to be developed is transported along this conduit. During this transport, the photo paper comes into contact with the developing fluid and results in the paper being developed. The small volume of the conduit and the demand for constant circulation of the developing fluid leads to high pressure in the conduit.
In order to withstand this high pressure, the processors must be highly stable from a mechanical aspect while ensuring reliable operation. Paper jams should be eliminated; that is, reliable transport of the paper along the conduit must be assured. Moreover, the processors must be simple to manufacture and should be capable of being produced in an economical manner.