GB2328923A

GB2328923A - Liquid handling apparatus

Info

Publication number: GB2328923A
Application number: GB9718475A
Authority: GB
Inventors: Leslie James Horace Pummell
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1997-09-02
Filing date: 1997-09-02
Publication date: 1999-03-10
Also published as: GB9718475D0

Abstract

Apparatus for handling a liquid comprises a processing vessel 2 having an outer rigid container, eg of mild steel and an inner flexible liner, eg of polythene. The apparatus may be used in the precipitation of a gelatin emulsion in the preparation of photosensitive material. An initial solution is supplied to the vessel and recirculated several times in a system including a heat exchanger 14, additive stages 16,18, a test station 20 and a pump 22. The vessel 2 may be open, with an outlet conduit 4 and inlet conduit 24, or the liner may be secured to the inlet conduit to close the vessel (Figs 2 and 3). The inlet conduit may be apertured along its discharge end and may be provided with a baffle plate; a stirrer 10 may be provided.

Description

LIQUID HANDLING APPARATUS Field of the Invention This invention relates to apparatus for handling, for example preparing or processing, liquids, and is of particular, though not exclusive, application in the field of processing photographic liquids, for example in the preparation of emulsions, or dispersions.

Background of the Invention The invention will be described with reference to the preparation of photographic liquids, for convenience, but it is to be understood that it is applicable to other liquids, for example those used in the preparation of food, where cross-contamination between the liquid and its container can be a problem.

Photographic liquids, such as emulsions, are prepared in large open vessels, usually referred to as kettles, and are transferred from one kettle to another during preparation before final deposition onto a substrate for making photosensitive film or paper. Each kettle may contain 1000 litres, or more, of the liquid, which may be kept at an elevated temperature. The kettles are usually formed from high-grade stainless steel, which is expensive, so as to minimise any reaction with the chemicals therein.

'Bag-in-box' arrangements are known in which a flexible bag is located within a rigid outer container. Such an arrangement forms a substantially sealed unit with a single connector providing communication for a photographic solution between the inner bag and the outside of the box. These arrangements are used in the processing of exposed photographic materials.

US Patent No. 3,589,862 discloses storage apparatus for a closed-type water purification system, in which an expandable sterilised bag is disposed in a water tank and connected to an inlet and an outlet thereof so that purified water entering the tank is confined solely within the bag. The top of the tank is closed so that air trapped therein limits the level to which water in the bag can rise, and also so as to provide excess pressure subsequently to allow the water to be discharged. The bag is impermeable to air, which is thus prevented from dissolving into the water.

Problem to be Solved by the Invention Even when employing stainless steel kettles, however, corrosion can occur due to contact with the chemicals, such as chloride photographic emulsions, and this can lead to iron debris which can contaminate the liquid and cause occasional fogging of the final photosensitive material. Furthermore, some liquids, such as gelatin containing silver halide emulsions, are prone to adhering to the kettle, which requires frequent cleaning. If cleaning is not carried out frequently or fastidiously enough, remaining emulsion can give rise to the formation of bacteria, with subsequent contamination of the next batch of liquid to be made. It is also common for the kettles to need polishing in order to minimise the existence of crevices in which emulsion can be retained. This is time-consuming.

It has been proposed to apply a coating of a ceramic material, or of polytetrafluoroethylene to a steel kettle to overcome these problems, but such a coating and its application are expensive.

Furthermore, after a certain amount of use a coating can peel off, especially if it is not properly applied initially or if it subsequently becomes scratched.

This can again give rise to unwanted debris in the photographic liquid, and/or the accumulation of material on the kettle wall.

It is one object of the present invention to provide apparatus for and a method of handling a liquid in which contamination is avoided, or at least mitigated, during the preparation of the liquid, whilst, preferably, also allowing for recirculation of the liquid during its preparation.

Summary of the Invention In accordance with one aspect of the present invention, there is provided apparatus for handling liquids, comprising: (a) a vessel for containing the liquid, the vessel comprising a rigid outer support body formed of a first material and a flexible inner member formed of a second material; inlet means for allowing the liquid to enter the inner member; and outlet means for allowing the liquid to exit the inner member; wherein the inner member forms a closed chamber within the support body and is secured to the inlet means such that the inner member is expandable on introduction of the liquid thereinto; and (b) recirculation means for the liquid, wherein liquid flowing from the outlet means of the vessel is subsequently supplied to the inlet means thereof.

The inner member, whilst being separate from, and not permanently attached or bonded to, the outer body, thus physically prevents contact between the liquid and the outer body. The material of the inner member is selected so as to be chemically inert with respect to the liquid to be contained therein, and advantageously will be a polymeric material, for example, polyethylene or polypropylene. Whilst the material of the outer body may be stainless steel, a cheaper alternative, such as mild steel, or aluminium, is preferred, since it will not be contacted by the liquid and will thus not be subject to chemical attack thereby.

The inner member is preferably in the form of a liner, and may be secured to the outer body.

The vessel may be provided with a cover to prevent ingress of contamination.

In accordance with another aspect of the present invention, there is provided apparatus for handling a liquid, comprising: a vessel for containing the liquid, the vessel comprising a rigid outer support body formed of a first material and a flexible inner member formed of a second material; inlet means for allowing the liquid to enter the inner member; and outlet means for allowing the liquid to exit the inner member; wherein the inner member forms a closed chamber within the support body and is secured to the inlet means such that the inner member is expandable, from a collapsed configuration, on introduction of the liquid thereinto.

The inner member may also be secured to the outlet means. In such apparatus, the inner member, or liner, can thus form a closed, and preferably sealed, container.

The outlet means and the inlet means may be located one within the other, preferably concentrically, and advantageously with the outlet means at least partially located within the inlet means.

The inner member may be a laminate, with different layers performing different functions, such as chemical inertness and good tear strength.

The recirculation means preferably includes a pump, and may comprise at least one processing and/or test station for the liquid. The processing station may comprise a heat-exchanger, and means for the addition of further components to the liquid, for example silver nitrate or a salts solution.

The inlet means preferably comprises a conduit, preferably having apertures along its length, so that as the inner member fills with liquid, there is always at least one aperture above the level of the liquid.

The apparatus preferably comprises baffle means arranged substantially to prevent the inner member blocking the outlet means as the liquid is removed therethrough.

The invention also provides a method of handling a liquid employing the apparatus of the invention.

In accordance with a further aspect of the invention, there is provided a method of making a photographic emulsion in a processing vessel comprising a rigid outer support body formed of a first material and a flexible inner member formed of a second material, wherein (a) an initial solution is supplied to the inner member of the processing vessel, (b) the initial solution is conducted from the vessel to a recirculation system, (c) further components for the formation of the emulsion are added to the initial solution during recirculation, (d) the emulsion is returned to the inner member of the vessel, and (f) the resulting precipitated emulsion is passed through the recirculation system at least one more time.

The inner flexible member may be of any colour, but for'photographic purposes it may be advantageous for it to be impervious to light, coloured black for example, so that preparation of the liquid may be carried out other than in a completely dark environment.

Advantageous Effect of the Invention The outer body of the apparatus is required only to provide mechanical support for the inner member, allowing it to be manufactured from a cheaper material, whilst the inner member can be chosen for its chemical resistance without regard for its mechanical strength.

The inner member of the apparatus of the invention can thus be provided as a liner, which may be arranged to be easily removable from the outer body for cleaning, or which may be provided for single use only, subsequently being discarded.

When the inner member provides a closed container, this results in a controlled environment for the liquid being handled. This reduces the risk of contamination of the liquid being processed, and can exclude light therefrom, which is particularly advantageous when the liquid is a photographic emulsion. Furthermore, evaporation is also reduced.

Brief Description of the Drawings Liquid processing apparatus, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic elevation of a first embodiment, showing an open-topped vessel and a recirculation system; Figure 2 is a schematic elevation of a second embodiment showing a modified processing vessel; and Figure 3 is a schematic elevation of part of another modified processing vessel.

Detailed Description of the Invention Referring to Figure 1, a generally-cylindrical, open-topped, mild steel photographic processing vessel, or kettle, 2 has an outlet conduit 4 in its otherwise closed base 6. A flexible polyethylene liner 8 sits within the kettle 2, is secured thereto and is sealed around the conduit 4.

The kettle 2 is part of an apparatus for producing a photographic emulsion, and as shown is exemplifying the preparation of a gelatin emulsion 9 as it is precipitated. To this end, the initial dilute gelatin formulation is poured into the open top of the kettle 2. The solution in the kettle 2 is agitated by a stirrer 10 so that any additives are well mixed in. The contents of the kettle 2 will be kept at an elevated temperature by heaters (not shown). The initial gelatin solution passes through the outlet conduit 4 to a valve 12, from where, at least initially, the liquid flows through a recirculation system comprising further processing stages. The solution passes from the valve 12 through a heat-exchanger 14 to ensure it is maintained at the correct temperature, then through an additive stage 16 at which silver nitrate is added, and then through a second additive stage 18 at which a solution of salts is added. Nuclei of silver halide are precipitated and are swept along in the recirculating stream. The re-circulation system also contains. a test station 20, at which the pH (acidity level) and VAg (for controlling the salts excess level) of the liquid are measured. It will be appreciated that a feedback loop (not shown) will be provided to ensure that the temperature, acidity and salt levels of the emulsion are maintained at the required levels. A pump 22 in the re-circulation system pumps the emulsion solution back into the kettle 2 through inlet pipe 24. Recirculation, with additives and measurements as required, is continued until the nuclei have grown to a size such that the emulsion has reached the condition in which it can be applied to a base to make the photosensitive material, film or paper. The emulsion can then be removed by pouring from the open top of the kettle 2, or by exiting through a drain outlet 26 of the valve 12.

Figure 2 shows a photographic vessel in a modified form from that of the kettle 2 of Figure 1.

Referring to Figure 2, the kettle comprises a mild steel outer container 30 and has a flexible inner polyethylene liner 32 located therein. The apparatus has an inlet pipe 34 for the emulsion 35 that extends downwards into the kettle 30 to terminate towards the base thereof, and an adjacent outlet pipe 36 that passes into a multi-way valve 38. The liner 32 is secured at its upper region to the inlet pipe 34 as it enters the kettle 30, and it is secured to the outlet pipe 36 at its lower region. In this way, the liner 32 forms a closed, sealed container within the steel kettle 30, and when empty will generally be collapsed around the inlet pipe 34.

The kettle 30 forms part of a re-circulation system as referred to with reference to Figure 1.

Gelatin emulsion may be introduced at any suitable point in the system, for example at one inlet of the valve 38. The emulsion 35 enters the kettle down the pipe 34, and this is perforated along its length to allow entry into the liner 32 at a plurality of levels. The liner 32 unwraps itself from around the pipe 34 into contact with the sides of the steel vessel 30, until it contains the required quantity of emulsion for precipitation. It is arranged for at least one perforation of the inlet pipe 34 to be above the maximum liquid level in the liner 32 in order to minimise back-pressure.

It may be arranged for the lower perforations of the pipe 34 to be successively closed off as the level of the liquid in the vessel 30 rises, in order that the recirculating emulsion passes through the vessel in so-called "plug flow", that is to say in such a manner that each element of the liquid is recirculated the same number of times.

In a further modification of the apparatus shown in Figure 3, the inlet and outlet pipes for the emulsion lie one within the other. Thus, the emulsion flows into a flexible liner 50 through a perforated outer pipe 52 as discussed with reference to Figure 2.

The emulsion leaves the liner 50, under the action of a pump of a re-circulation system (not shown), through an inner bore 54 that passes back up the outer pipe 52. The bottom end of the pipe 52 has a baffle arrangement 56 to prevent the liner 50 being sucked against and closing the entrance to the outlet pipe 54, the arrangement 56 consisting of a circular plate 58 transversely terminating a perforated extension 60 of the outer pipe 52.

After precipitation of the emulsion is complete, the recirculation system is purged, and the kettle is either pumped empty, with the emulsion being transferred to a wash station, or is itself transported to the wash station. If the same emulsion kind is to be made again, the same liner may be reused. However, if a different emulsion is to be precipitated, the old liner can be discarded and a new inserted in its place into the outer kettle.

It is to be understood that, wherever appropriate, features described above with reference to one embodiment of the apparatus may be combined with features described with reference to another embodiment. Furthermore, it is to be understood that the present invention is applicable to the handling of liquids other than photographic ones.

Claims

CLAIMS :

1. Apparatus for handling liquids, comprising: (a) a vessel for containing the liquid, the vessel comprising a rigid outer support body formed of a first material and a flexible inner member formed of a second material; inlet means for allowing the liquid to enter the inner member; and outlet means for allowing the liquid to exit the inner member; wherein the inner member forms a closed chamber within the support body and is secured to the inlet means such that the inner member is expandable on introduction of the liquid thereinto; and (b) recirculation means for the liquid, wherein liquid flowing from the outlet means of the vessel is subsequently supplied to the inlet means thereof.

2. Apparatus according to claim 1, wherein the recirculation means comprises at least one processing and/or test station for the liquid.

3. Apparatus according to claim 1 or claim 2, wherein the inner member is secured to the outlet means.

4. Apparatus according to any one of the preceding claims, wherein the outlet means and the inlet means are located one with in the other, preferably concentrically.

5. Apparatus according to claim 4, wherein the outlet means is at least partially located within the inlet means.

6. Apparatus according to any one of the preceding claims, wherein the inlet means comprises a conduit, preferably having apertures along its length.

7. Apparatus according to any one of the preceding claims, comprising baffle means arranged substantially to prevent the inner member blocking the outlet means of the vessel.

8. Apparatus for handling liquids, comprising: an open vessel for containing the liquid received through inlet means, the vessel comprising a rigid outer support body formed of a first material, and an inner member formed of a second material for receiving the liquid; and outlet means for allowing the liquid to exit the inner member through the outer body.

9. Apparatus according to any one of the preceding claims, wherein the inner member is secured to the outer body.

10. Apparatus according to any one of the preceding claims, arranged for processing photographic liquids, preferably emulsions.

11. Liquid handling apparatus, substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of making a photographic emulsion in a processing vessel comprising a rigid outer support body formed of a first material and a flexible inner member formed of a second material, wherein (a) an initial solution is supplied to the inner member of the processing vessel, (b) the initial solution is conducted from the vessel to a recirculation system, (c) further components for the formation of the emulsion are added to the initial solution during recirculation, (d) the emulsion is returned to the inner member of the vessel, and (f) the resulting precipitated emulsion is passed through the recirculation system at least one more time.