LIQUID CHEMICAL MIXING METHOD AND APPARATUS

Abstract: Mixing chemicals in liquid form by circulating one or more chemicals through a circuit which contains a porous filter (16), and introducing one or more further chemicals into the circuit immediately upstream of the porous filter (16).

Description: -l- LIOUID CHEMICAL MIXING METHOD AND APPARATUS The present invention relates to the mixing of chemicals in liquid form. Photographic processing solutions, for example, are generally made up or replenished by the addition of concentrated solutions of chemicals to water or existing depleted solutions. It is essential to ensure that the mixing takes place rapidly and evenly as the chemicals may be subject to oxidation or otherwise deteriorate. Further, it is essential that the added chemicals should be dispersed evenly throughout the mixture. Hitherto it has been conventional for the liquid concentrate developer or replenisher to be added to the processing solution bath in the amount required and thereafter the whole bath is stirred using a paddle mixer or the like. Not only is such method time-consuming but -also the dispersion of the active ingredients of the added developer or replenisher is initially extremely disparate. it is an object of the present invention to provide a method of and an apparatus for mixing chemicals in liquid form wherein the aforesaid disadvantages are minimised or obviated. According to the present invention there is provided a method of mixing chemicals in liquid form comprising the steps of circulating one or more chemicals through a circuit comprising one or more porous filters and introducing one or more further chemicals into the circuit immediately upstream of the or each filter. One of said chemicals being circulated through the circuit may be water or a photographic processing solution held in a container.. One of said further chemicals may be a developer concentrate or replenisher concentrate. The further chemical or chemicals is/are added to the flow of the chemical or chemicals in the circuit at a rate corresponding to the desired ratio of said chemicals in the mix. According to the present invention there is also provided an apparatus for mixing chemicals in liquid form comprising a container for holding one or more chemicals, means for circulating said one or more chemicals from the container through a circuit, one or more porous filters in the circuit, and means for introducing one or more further chemicals into the circuit immediately upstream of the or each filter. The container is conveniently a photographic processing bath which may be provided with a reservoir for the processing solution. The path of circulation may be to and from the bath and may include the • reservoir. According to the present invention there is further provided a photographic processor comprising an apparatus as aforesaid for mixing chemicals wherein said container comprises a photographic processing bath. A convenient filter is a 20ι_m porous filter. The present invention will be described further, by way of example, with reference to the accompanying drawing in which the single figure is a diagrammatic representation of an apparatus for mixing chemicals in- accordance with the present invention. As represented in the drawing, a photographic processor includes a development bath 10 for containing a photographic developer 11 comprising a mixture of at least first and second chemicals in liquid, i.e. solution form. A developer circulation path 12 includes a pump 13 enabling the developer 11 to be circulated to minimise the effects of oxidation, depletion and/or stagnation. A reservoir 14 holds the bulk of the developer 11. Included in the path 12 is a filter housing 15 including a porous 20 μm filter 16. The housing 15 has an inlet 17 upstream of the filter 16 whereinto a second chemical in liquid form may be injected by a pump or the like shown diagrammatically at 18 from a supply 19. Initially the bath 10 may be filled with water (the first liquid chemical) and the pump started to circulate the water in the direction indicated by the arrow A. As the water passes through the filter housing 15, a second chemical in liquid form, a concentrated solution of developer, is injected into the flow by the pump 18 preferably at a rate corresponding to the desired dilution. The two chemicals mix upon passing through the filter 16 so that the developer is dispersed at the desired concentration into the flow. Circulation is continued at least until all the concentrated solution has been injected into the flow. The pump 18 can also have the effect of causing further mixing of chemicals. If the bath 10 initially contained depleted developer solution, the same procedure is followed except that developer replenisher concentrated solution is added from the supply 19. In some instances, a reservoir 14 is not included and the path of circulation is via the connection 20 (shown dotted) instead of through a reservoir. I Laboratory tests have been carried out by injecting 100 ml samples of a solution containing 360 ml/1 benzyl alcohol and 241 ml/1 diethylene glycol into a stream of water circulated, from a tank holding initially 13.1 litres, through a 20 μm porous filter. The filter used was a diamond wound honeycomb string filter of the kind available from Commercial Filters Corporation, of Lebanon, Indiana, United States of America. One minute after each injection, a small sample of the bulk solution was taken for analysis — with the following results: concentrate diethylene glycol (ml/1) benzyl alcohol (ml/1 ml injected calculated analysed calculated analyse 100 1.84 1.80 2.75 2.70 200 ■ 1.83 1.80 2.73 2.70 300 1.81 1.75 2.71 2.80 400 1.80 1.75 2.69 2.65. 500 1.79 1.80 2.67 2.70 These results demonstrate excellent correlation between the calculated and actual concentrations for both diethylene glycol which is readily dissolved in water, and benzyl alcohol, which is normally difficult to disperse and dissolve. A suitable alternative filter is the "Cuno Micro lean II Filter Cartridge" available from A.M.S., 62 Les Attagues, France under the code number G78.F9. The present invention is not confined to the precise details of the foregoing example and variations may be made thereto. For example the invention is applicable to the mixing of three or more chemicals each in liquid form either simultaneously or sequentially by having two or more inlets to the filter housing 15 or by having a plurality of filters and their housings arranged along the path of circulation.' The present invention is applicable to the mixing of chemical solutions and/or dispersions other than those of a photographic nature. The porosity of the filter is chosen such as readily to pass the chemicals so that the resistance to flow is not too great and any particles (in the case of dispersions) will pass therethrough.

Claims: CLAIMS 1. A method of mixing chemicals in liquid form comprising the steps of circulating one or more chemicals through a circuit comprising one or more porous filters and introducing one or more further chemicals into the circuit immediately upstream of the or each filter. 2. A method according to claim 1 wherein the number of further chemicals introduced is two or more. 3. A method according to claim 2 wherein at least two of said further chemicals are introduced simultaneously immediately upstream of the same filter. 4. A method according to claim 2 wherein at least two of said further chemicals are introduced sequentially immediately upstream of different respective filters. 5. A method according to claim 1 wherein said chemicals are further mixed by a pump by which said one or more further chemicals are introduced into the circuit. 6. A method according to any one of the preceding claims wherein the chemicals are mixed together to form or replenish a photographic processing solution. 7. An apparatus for mixing chemicals in liquid form comprising a container (10) for holding one or more chemicals, means for circulating said one or more chemicals from the container (10) through a circuit, one or more porous filters (16) in the circuit, and means (18) for introducing one or more further chemicals into the circuit immediately upstream of the or each filter (16). 8. An apparatus according to claim 7 wherein one or more of said filters (16) is a 20ι±m filter. 9. An apparatus according to claim 7 or 8 comprising a filter (16) mounted in a housing (15) having two or more inlets (17) upstream of the filter (16) for receiving two or more chemicals simultaneously. 10. An apparatus according to claim 7 or 8 comprising two or more filters at different locations in the circuit. 11. An apparatus according to claim 7 wherein said means (18) for introducing said one or more further chemicals into the circuit comprises a pump. 12. An apparatus according to claim 7 wherein said container (10) comprises a photographic processing bath. 13. An apparatus according to claim 12 further comprising a reservoir (14) for processing solution. 14. A photographic processor comprising an apparatus according to claim 7 wherein said container (10) comprises a photographic processing bath.

Inventors: GREEN ANDREW, GREEN, ANDREW
Applicants: EASTMAN KODAK CO, KODAK LTD, EASTMAN KODAK COMPANY, KODAK LIMITED
Application year: 1986
Main classification: B01F5
IPC codes: B01F5, G03C5, G03D3