EP0094840A2

EP0094840A2 - Photographic developing tank

Info

Publication number: EP0094840A2
Application number: EP83302812A
Authority: EP
Inventors: Sidney Richard Dunn
Original assignee: PHOTAX (LONDON) PLC
Current assignee: PHOTAX (LONDON) PLC
Priority date: 1982-05-19
Filing date: 1983-05-18
Publication date: 1983-11-23
Also published as: EP0094840A3

Abstract

A device for use in a photographic developing tank comprises an elongate hollow column arranged to carry a spool or a number of spools arranged in a stack. Each spool is displaceable along the length of the column and, to retain it at a predetermined longitudinal position on the column, resilient means are provided on either the column or the spool and are integral therewith.

Description

This invention relates to developing tanks for the processing of strips of photographic film and to a device for use in such tanks.
Developing tanks consist essentially of a light-proof enclosure for receiving one or more spools, each supporting a strip of film, and having provision by which processing liquids can be introduced into, and withdrawn from, the enclosure while retaining the enclosure light-proof.
A spool for receiving a strip of photographic film comprises a centre tube holding apart a pair of discs each having a spiral groove on the surface thereof which faces the other disc. The strip of photographic film is threaded on to the spool so that the lateral edges of the strip are retained in the grooves in the pair of discs.
Figure 1 of the accompanying drawings is a diagrammatic sectional side elevation of a known developing tank.
Such a tank comprises a generally cylindrical container 1 closed at its lower end and having a threaded flange 2 around its upper end. A lid 3, having a threaded inner rim, screws tightly on to the container. At the centre of the lid, there is an opening 4, surrounded by an upstanding wall 5, leading to a funnel-shaped portion 6. A hollow central column 7, having a flange at its lower end, is positioned in the container and the lower end of the funnel-shaped portion 6 extends into the upper end of the hollow column. Liquids introduced into the opening 4 flow down the column 7 and out of the lower end into the container. A spool 8 is fitted on the column. The column with one or more spools fitted on it is introduced into the container and, after the lid has been fitted, a strip of photographic film supported on the spool is contained within a light-tight enclosure and liquids required to process the film are introduced into, and removed from, the tank through the opening 4.
Although the spool is movable along the central column, it is necessary to be able to locate it firmly in position on the column, since it is usual to shake and invert the tank during processing in order to thoroughly mix the chemicals.
It is known to provide a resilient C-shaped member which clips around the column after the spool has been placed on it and ,which is forced along the column into engagement with the end of the spool. This clip then prevents the spool from moving along the column. It has been found that, with such a clip, it is easily lost as it is completely separate from the column and the spool and, furthermore, that, after a period of time, the springiness of the clip can become reduced so much so that it does not prevent the spool from moving along the column.
It is also known for the centre tube of a spool to be adjustable in length to vary the separation of the discs so that the spool can accommodate strips of different widths and it is also known for several spools to be accommodated in a stack in a developing tank.
It is an object of the present invention to provide a device for use in a photographic tank whereby the movement of a spool or spools along a central column is restricted.
According to the present invention, a device for use in a photographic tank comprises an elongate hollow column; a spool for carrying a strip of photographic film, said spool fitting on the column and being displaceable along the length thereof; and resilient means integral with either the spool or the column for retaining the spool at a predetermined longitudinal position on the column.
Since the retaining means is formed integral with the spool or the column, it cannot become lost, thus overcoming one of the disadvantages of the known arrangement.
In one embodiment of the invention, a plurality of protrusions are provided on the centre tube of the spool and extend inwardly thereof, and the protrusions interact with a selected one of a plurality of annular grooves formed at positions spaced apart longitudinally of the column.
In an alternative embodiment, the protrusions are provided on the column and extend outwardly thereof.
In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 2 is a side elevation of a column of a developing tank with a spool mounted thereon according to the present invention;
Figure 3 is a sectional plan view of part of a spool;
Figure 4 is a detail of che spool shown in Figure 3;
Figure 5 is a detail of the spool shown in Figure 2; and
Figure 6 is a side view of an alternative form of column.

Referring to Figure.2, a central hollow column 11 of a developing tank has a flange 13 at its lower end and a plurality of circumferential grooves 15 positioned at regions spaced apart longitudinally of the column. A spool 17, for receiving a length of photographic film, comprises two circular discs 19, 21, each having a spiral groove 23 formed on its surface which faces the other disc. The two discs are mounted on a tube 25 which is formed centrally of the spool.
It is necessary for the spool to be removable from the column 11 but, at the same time, in use, the developing tank may be shaken or even inverted and it is not desirable that the spool should slide along the length of the column 11. To this end, the tube 25 is provided with a plurality of protrusions 27 which interact with one of the grooves 15 to locate the spool relative to the column.
As shown in Figures 3 and 4, the protrusions are formed integral with the tube 25 and, to form each protrusion, two generally rectangular portions 28 are cut out of the wall of the tube to leave a central portion 29 which is resilient with respect to the wall of the tube. The central portion has an outwardly extending part 31 which is convex from its upper to its lower end.
Figure 5 shows how the part 31 can be allowed to protrude into one of the grooves 15 in the column 11.
As the spool is fitted over the upper end of the column 11, the protrusions are forced outwardly and engage with the outer surface of the column. As the spool is moved down the column, the protrusions are urged into each of the grooves 15 in turn. Finally, when the spool engages against the flange 13, the protrusions engage with the lower one of the grooves 15, as shown in Figure 2. If the spool is of a type for receiving wider film, then the protrusions will interact with the next higher groove in the column. If two spools are placed one above the other on the column, then each spool interacts with a separate one of the grooves in the column.
In an alternative embodiment of the invention, the protrusions are formed on the column. Referring to Figure 6, the column 41 has protrusions 43 formed at a number of regions longitudinally positioned along.its length. The protrusions are of the same form as those shown in Figures 3, 4 and 5. The centre tube of the spool to be fitted to the column may have grooves formed in the wall which defines its bore, in which case, when the spool is positioned on the column, the protrusions at one region on the column project into one of the grooves in the wall of the centre tube. This arrangement is thus the reverse of that shown in Figures 1 to 5.
Alternatively, the protrusions on the column may serve to locate the spool on the column without the need to provide grooves in the centre tube of the spool. As the spool is pushed down the column from the upper end towards the flange 45 at its lower end, the protrusions are pushed inwardly to allow the spool to move past them. When the spool has moved past the protrusions, their resilience urges them outwardly again. When the spool is very close to the flange, one set of protrusions bears against the upper end of the spool so as to positively locate the spool between the flange and the group of protrusions. If protrusions 43A bear against the upper end of the spool, the protrusions 43B serve as friction springs engaging against the bore of the centre tube of the spool to ensure that the spool is a tight fit on the column.
Although the protrusions prevent the spool from moving along the column when the developing tank is in use, the spool can be removed from the column by applying sufficient force to the spool to push the protrusions inwardly to enable to spool to be moved along the column.

Claims

1. A device for use in a photographic tank comprising an elongate hollow column (11, 41); a spool (17) for carrying a strip of photographic film, said spool fitting on the column, and being displaceable along the length thereof; characterised in the provision of resilient means (27, 43) integral with either the spool or the column for retaining the spool at a predetermined longitudinal position on the column.

2. A device as claimed in claim 1, wherein the spool includes a central tube (25) and characterised in that the resilient means comprises a resilient protrusion (27) integral with the tube (25) and projecting inwardly of the bore of the tube, and the column (11) has an annular groove (15) therein into which the protrusion (27) enters to retain the spool on the column.

3. A device as claimed in claim 2, characterised in that a plurality of resilient protrusions (27) are . integral with the tube (25) and project inwardly of the bore of the tube, all said protrusions (27) being psitioned at the same distance from one end of the tube.

4. A device as claimed in claim 2 or 3, characterised in that the or each protrusion (27, 31) is convex from its upper to its lower end.

5. A device as claimed in claim 1, characterised in that the resilient means comprises a resilient protrusion (43) integral with the column (41) and projecting outwardly thereof.

6. A device as claimed in claim 5, characterised in that a plurality of resilient protrusions (43) are integral with the column (41) and project outwardly thereof, all said protrusions being positioned at different axial regions on the column.

7. A device as claimed in claim 5 or 6, characterised in that the or each protrusion (43) is convex from its upper end to its lower end.

8. A device as claimed in claim 1, characterised in that the column (41) has a flange (45) at one end which prevents the spool from passing over said end of the column, and the resilient means comprises a resilient protrusion (43) integral with the column (41) at a position spaced from said flange (45) and projecting outwardly from the column.

9. A photographic tank characterised in that it includes a device as claimed in any preceding claim.