Washing method and apparatus

#This is a U.S. original patent application which claims priority on Great Britain patent application No. 0220261.2 filed Aug. 31, 2002.

#This invention relates to the washing of sheets of material which contain substances requiring washing for their removal. The invention relates in particular to the washing or stabilization stage of the photographic processing of color film and paper. The invention will be described with reference to a system for washing photographic paper.

#There is a need in the photographic industry to remove substances from processed material to ensure image stability. In deep-tank replenished processing systems material passes from one tank to the next. For example, with respect to processing of color paper, the material passes through a first tank for development, a second tank for bleach/fix and then into a series of wash or stabilizer tanks. The wash tanks are usually inter-connected so that clean washing solution is added to the last of the tank series and the over-flow from the last tank is transferred to the previous tank and so on. In this way the flow of solution is in a direction which is counter to the direction of transport of the paper. This so-called counter-current flow technique enables efficient washing since when the material has the highest content of substances to be removed, the wash solution also has the highest concentration of removed substances and clean solution is only used in the last step when the processed material contains little removable contaminants.

#The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

#FIG. 1 is a schematic view of an embodiment of the invention;

#FIG. 2 is a graph showing density of the washed paper against distance along the planar surface;

#FIG. 1 is a schematic view of an embodiment of the invention.

#Referring to FIG. 1 there is provided a substantially planar inclined surface 2. An inlet 4 for the introduction of fresh wash solution is located at the upper end of the inclined surface 2. An outlet 6 for the dirty wash solution is located at the lower end of the surface 2. In the embodiment illustrated the surface is covered with a material such as fabric. This fabric cover 8 provides resistance to flow in the plane of the fabric by soaking up the wash solution within the fibers. The fabric cover is a preferred feature and is not essential to the present invention. A flexible member 12 is provided above the material to be washed, hereinafter referred to as paper 10, such that it lies on the back thereof. The member 12 is fixed across its width at the lower end of the surface 2. This end of the member may be curved to facilitate the feeding of paper between the member and the surface 2. The member may also be fixed at the upper end of the surface but this is not essential. The flexible member 12 is of sufficient weight to rest on the paper and make the paper conform to the surface of the inclined plane but not to prevent transportation of the paper up the planar surface. The whole width of the paper is held against the planar surface by the weight of the member 12. The member could, for example, be made of a PVC based material or of silicone rubber material

#Rollers or other transportation means, not shown, convey the paper to be washed up the inclined surface. The paper may be in sheet form or be a continuous web of coated material. It is preferable for the surface of the flexible member 12 in contact with the paper to be textured. Such a surface reduces resistance to movement of the paper. It is also preferable that the textured surface is such that the highest points of the surface are in a continuous plane, i.e. the surface consists of a plurality of indentations below a planar surface rather than protrusions above a planar surface.