GB2068782A - Developing apparatus for photographic sheet or strip material - Google Patents

Abstract

A pump, for supplying liquid at a controlled temperature to a bowl containing a developing drum and liquid storage flasks, is driven by a motor (19) mounted on a tank cover (17) and has a shaft (29) extending downwardly through a generally cylindrical beaker (23). In the lower end of the beaker (23) an impeller (22) draws in, through apertures (25), liquid heated by a heater (39) in a storage tank (10) and raises it up the beaker (23) with the liquid swirling around to leave through an outlet passage (24) to flow into the bowl. A temperature sensor is provided in the beaker (23) adjacent the outlet passage (24). <IMAGE>

Description

SPECIFICATION Developing apparatus for photographic sheet or strip material The invention relates to developing apparatus for photographic sheet or strip material, with a circulatable liquid bath to effect temperature control of working vessels, such as a rotating developing drum, liquid storage flasks and measuring vessels.

Such apparatus may comprise a circulating pump with an impeller provided with radial scoops, the impeller being located in a pump housing into which the bath liquid is drawn axially and being driven by an electric motor.

The bath liquid is drawn into the pump housing from a supply tank provided with controllable heating means and having a cover thereover and an outlet for the bath liquid from the pump housing leads into a temperature-control bowl accommodating the working vessels, the temperature of which is to be controlled.

Developing apparatus of this kind has been previously proposed, in which the electrically driven circulating pump is linked to the storage tank and/or the temperature-control bowl by tubular connections. However, such pumps are expensive since they require an encapsulated pump housing and the electric motor drive must be suitably sealed off from it. With such pumps it is also difficult to measure the temperature of the fluid supplied to the temperature-control bowl correctly, and considerable measuring errors result from heat losses.

However, a constant and accurate temperature is of the utmost importance if colour films are to be developed true to the original colour.

According to the invention there is provided developing apparatus for photographic sheet or strip material with a circulating liquid bath to effect temperature control of working vessels, such as a rotating developing drum, liquid storage flasks and measuring vessels, comprising a circulating pump with an impeller provided with radial scoops, the impeller being driven by an electric motor and being located in a pump housing into which the bath liquid is drawn axially from a supply tank, the supply tank being provided with controllable heating means and having a tank cover thereover and an outlet for the bath liquid from the pump housing leading to a temperature-control bowl accommodating the working vessels, wherein the outlet comprises a generally cylindrical jacket extending the pump housing in an axial direction, a shaft mounting the impeller extends axially through the cylindrical jacket to a motor located above the tank cover, and the cylindrical jacket and the pump housing together form a mixing beaker for the bath liquid, which is raised therein in an axial direction to flow out through a transversely directed overflow aperture at the upper end of the mixing beaker.

Axial juxtaposition of the mixing beaker and the centrifugal pump, driven by a vertical shaft, forms an agitating mechanism, in which the pump impeller is the agitator. The pump housing, which contains the liquid accelerated by rotation and discharges it into the tangential outlet pipe, is here not closed at its upper end but rather is extended upwardly by the cylindrical jacket. The impeller acts on liquid entering the pump housing, formed by the lower end of the beaker, accelerates it and sets it in rotation. The rotating fluid causes a paraboloid of revolution to form in the mixing beaker, and the fluid is drawn off at the upper end of the beaker. The impeller need only comprise a disc with radial scoops thereon.

Advantageously the impeller is open towards the bottom and directly draws the incoming liquid into rotation and accelerates it. At the resultant paraboloid the transversely directed overflow aperture is provided at the upper end of the mixing beaker, to allow the liquid to be discharged. The liquid entering in an axial direction from below is simultaneously rotated and raised.

As it emerges into the transversely directed overflow aperture, the liquid flows into an overflow passage which can have a considerable cross-section and thus presents far less resistance to flow than the narrow tubular pipes previously used. The distance along which the liquid is transported can also be much shorter and the liquid can run into the temperature-control bowl with a free fall. No pumping output is required to overcome resistances to flow along the transporting path.

Thus only a small pumping force is required exclusively to lift the liquid.

The raising of the liquid is accompanied by strength turbulence, resulting in complete equalisation of temperature. This equalisation is important since it is absolutely exxential that a heating coil in the supply tank should not cause formation of liquid stratifications at different temperatures in the tank. For this reason the heating coil is advantageously arranged in the tank round about the suction aperture of the pump housing. The fluid sucked up by the impeller can thus be drawn immediately out of the region of the heating coil, thereby creating favourable flow conditions for uniform warming of the bath liquid.

The rotation of the liquid in the beaker is also advantageously used for temperature measurement. For this purpose a temperature sensor is disposed across the flow in the beaker. The sensor preferably extends into the rotating liquid from above, in the edge region of the beaker. The flow of bath liquid breaks against it, thereby creating a turbulent flow around it; this flow provides optimum temperature equalisation at the sensor and thus minimises measuring errors resulting from migration of heat in the material of the sensor and its fastening means. The sensor can have the ascending, rotating liquid washing around it over a considerable length. Preferably the temperature sensor is immersed in the immediate vicinity of the outflow aperture so that the temperature read is exactly that which will prevail in the temperature-control bowl.In addition, since the sensor is fitted in the marginal region of the overflow aperture, it acts as a flow breaker and ensures that the liquid flows off in a surge. Other components may be provided in the beaker to affect the flow, for example a coil extending in the desired direction of flow.

For a low-cost solution to the problem of sealing off the pump shaft from the motor chamber and from the outside, the drive motor is preferably disposed on a fixture on the tank cover. The shaft of the impeller bridges the resultant free space. No liquid at all reaches the place to be sealed off, in the tank cover. The region where the impeller shaft is taken through the tank cover may be constructed as a perfectly normal bearing bush or passage. Thus the motor can be located in a region above the tank cover, which is itself provided as a space for fitting other electrical components and their connections to a control panel, and which is already being used for a purpose.

The upper part of the mixing beaker is preferably formed by the side walls of a recess in the moulded tank cover. At its lower end, which also forms the pump housing, the mixing beaker preferably has its bottom wall formed by an insert which contains apertures to allow the liquid to enter the beaker in an axial direction. Thus a divided construction of the beaker is preferable with the tank cover, which has a large area, and the insert being manufactured in separate operations and with simpler tools and assembled into an operating unit. Of the overflow passage adjoining the overflow aperture at the beaker, at least the lower wall of the passage can advantageously be moulded integral with the beaker. The other walls of the passage may be formed by a recess in the moulded tank cover.For reliable operation of the circulating pump particularly with a view to smooth discharge of the liquid, as far as possible without spraying-it is favourable to have one side wall of the overflow passage, with the rotating flow, extending at a tangent from the cylindrical jacket of the mixing beaker. The other, opposed side wall of the overflow passage need then only be so disposed as to give the requisite width of passage.

The pumping action is furthermore favourably affected by having a rounded transitional region between the bottom wall and the side wall of the beaker. Thus the liquid components centrifuged radially by the impeller are gradually deflected into an upward flow in the beaker. The cylindrical jacket may be extended in a conical shape towards the overflow aperture, so that is has a favourable affect on the upward-rotating flow. The bottom of the mixing beaker preferably includes an appropriate bearing bush, held by webs, to provide a good guide for the long shaft of the impeller. A screen may be provided in the bottom wall of the beaker in the region of the apertures therein.

To facilitate the assembly of the cylindrical jacket and the tank cover-particularly for threading the impeller shaft into the bearing bush at the bottom of the beaker-the impeller shaft can contain a recess in its end to receive an appropriate mounting pin. As a means of holding the beaker-like insert with the integral overflow passage member so that they operate reliably, a set of connecting elements, e.g. detent halves, may be provided on the cylindrical jacket, with their complementary halves located on the tank cover.

The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 shows developing apparatus according to the invention with a developing drum placed in a temperature-control bowl and supply flasks and measuring vessels; Figure 2 is a section taken on line Il-Il of Fig. 1; Figure 3 is a partial section through the interior of a control housing and a circulating pump of the apparatus according to the invention; Figure 4 is a view taken in the direction of arrow IV of Fig. 3, but with a mixing beaker removed; Figure 5 is a view of the mixing beaker taken in the direction of arrow IV of Fig. 3; Figure 6 is a section taken on line VI-VI in Fig. 3, showing a temperature sensor and its fixing means; and Figure 7 is a view taken in the direction of arrow VII of Fig. 3, of an orifice of an overflow passage.

Referring to the drawings and firstly to Fig.

1, developing apparatus has a portable tank 10 with a cover 11 with a recessed portion forming a temperature-control bowl for a developing drum 12, and having various apertures therein to receive liquid storage flasks 1 3 and measuring vessels 14. A control panel 1 5 can be seen at the lefthand side of Fig. 1; this is part of a raised housing 1 6 accommodating a drive motor for rotating the developing drum 1 2 and also a pump for circulating bath liquid for keeping the drum 12, the flasks 1 3 and the vessels 14 warm. The raised housing 1 6 has a separate tank cover 17, which also forms a framework for mounting various components. It will be seen from Fig. 2 that the fluid level in the temperaturecontrol bowl is higher than that in the tank 10. The fluid being circulated by the pump runs freely from the bowl over an overflow edge 18 into the tank 10.

Of the components located below the raised housing 1 6 the circulating pump arrangement is illustrated in Fig. 3. It comprises an electric drive motor 19, an elongate shaft 21 mounting an impeller 22, and a cylindrical beaker 23 with an overflow passage 24 and inlet apertures 25.

The motor 1 9 is mounted on a fixture on the tank cover 17. A shaft 26 of the motor carries a socket-type coupling member 27 with a spray-arresting flange 28 moulded onto it. Adjoining the coupling member 27 is a length of shaft tubing 29, the lower end of which receives an upper stub shaft 30 of the impeller 22. A lower stub shaft 31 of the impeller is guided in a bearing bush 32 of the beaker 23. The impeller 22 comprises a disc 33 with radial scoops 34 moulded onto it.

The impeller is open at the bottom towards the inlet apertures 25. The lower part of the cylindrical beaker 23, surrounding the impeller, corresponds to an open-topped pump housing 35 and has a rounded portion 36 in the transitional part leading to the inlet apertures 25. As can be seen particularly from Fig. 5, the bearing bush 32 is kept centered in the inlet apertures 25 by four webs 37.

The free stub shaft 31 of the impeller, which is held in the bearing bush 32, has an axial recess 38 in its end, to receive a mounting pin in order to facilitate insertion of the free end of the shaft 31 in the bearing bush 32.

The cylindrical beaker 23 adjoining the pump housing 35 has its upper end 40 inserted in a corresponding recess-see Fig.

4 in particular-in the-cover 1 7 of the tank.

The top edge 40 of the beaker insert abuts a narrow marginal shoulder 42 at the contour of the recess (see Fig. 4). This recess in the tank cover 1 7 is dimensioned so that the cylindrical beaker 23 extends into a cylindrical part of the recess with the side walls 41. One side wall 44 of the overflow passage 24 extends at a tangent from the cylindrical side walls 41 (see Figs. 3, 4 and 7). With this recess in the tank cover, the top wall 43 of the passage 24 is formed with various roof-like inclines.

The lower wall of the passage is integral with the mixing beaker 23 (see Figs. 3 and 5). This lower wall 45 is in the same plane as the top edge 40 of the beaker, and ends in an overflow web 46. The wall 45 has an inclined portion 47 extending into the cylindrical beaker. The wall 45 is supported by lateral webs 48, extending as far as the cylindrical jacket of the beaker 23. A closing web 49 of the wall is flush with the externai contour of the tank cover 1 7. Locking means are provided to hold the beaker 23 in a stable manner in the recess in the cover 1 7. They include detent halves 50, moulded in the side walls 41 of the cylindrical part of the recess, and corresponding detent halves 51 provided at the top edge 40 of the beaker.During its insertion the beaker 23 is deformed slightly at its upper edge 40 and is held securely when it springs back (see Fig. 6).

The fixture 20 of the recess in the tank cover 17, on which the electric motor 1 9 is fixed, comprises two parallel bearing webs 60, through which screws for fixing the motor engage (see particularly Fig. 3). Between the two webs 60 there are means 61 for guiding through the shaft, in the form of a cylindrical bush. In the gap between the bearing webs 60, the bush 61 is adjoined by an inclined roof wall 62 at each side, as can be seen particularly from Fig. 6. One of the inclined roof walls 62 contains an aperture, through which a temperature sensor is inserted, with a rubber seal 64. The temperature sensor 63 extends into the beaker 23 over its top edge 40. As can be seen particularly from Fig. 4, the aperture for the temperature sensor 63 is opposite the tangentially adjoining side wall 44 of the overflow passage 24. The sensor 63 preferably lies in an axial plane which includes the axis of the shaft 29.

With the fitting location found here for the temperature sensor 63, the sensor breaks the swirl of the bath liquid in the mixing beaker 23, generated by the impeller 22. It is always well surrounded with liquid flowing at high speed. The sensor breaks the flow before the overflow passage 24 and ensure that a surge of the bath liquid runs off in that direction.

Fig. 3 shows a heating coil 39 which surrounds the inlet apertures 25 of the pump housing, at the bottom of the tank. The coil 39 may comprise a closed tube system with an electric heater spiral drawn into it. The impeller 22 of the pump sucks up liquid directly from the region of the heating coil.

Temperature equalisation takes place within the mixing beaker 23 through strong turbulence of the liquid.

Claims (14)

1. Developing apparatus for photographic sheet or strip material with a circulatable liquid bath to effect temperature control of working vessels, such as a rotating developing drum, liquid storage flasks and measuring vessels, comprising a circulating pump with an impeller provided with radial scoops, the impeller being driven by an electric motor and being located in a pump housing into which the bath liquid is drawn axially from a supply tank, the supply tank being provided with controllable heating means and having a tank cover thereover and an outlet for the bath liquid from the pump housing leading to a temperature-control bowl accommodating the working vessels, wherein the outlet comprises a generally cylindrical jacket extending the pump housing in an axial direction, a shaft mounting the impeller extends axially through the cylindrical jacket to a motor located above the tank cover, and the cylindrical jacket and the pump housing together form a mixing beaker for the bath liquid, which is raised therein in an axial direction to flow out through a transversely directed overflow aperture at the upper end of the mixing beaker.

2. Developing apparatus according to claim 1, in which the cross-section of the cylindrical jacket generally corresponds to the cross-section of the pump housing.

3. Developing apparatus according to claim 1 or claim 2, in which the cylindrical jacket widens conically adjacent the overflow aperture.

4. Developing apparatus according to any one of claims 1 to 3, in which at its upper end the mixing beaker is formed by side walls of a recess in the tank cover, and at its lower end, which is formed by the pump housing, has an apertured bottom wall which provides for axial intake of liquid.

5. Developing apparatus according to claim 4, in which the bottom wall of the mixing beaker includes a bearing bush which supports the lower end of the shaft mounting the impeller.

6. Developing apparatus according to claim 4 or claim 5, in which the beaker has a rounded portion in a transitional region between its bottom wall and its side wall.

7. Developing apparatus according to any one of claims 4 to 6, in which the bottom wall of the beaker is provided with a screen in the region of the apertures therein.

8. Developing apparatus according to any one of claims 1 to 7, in which the overflow aperture of the beaker comprises an overflow passage disposed opposite the pump shaft and laterally offset with one lateral boundary of the passage extending at a tangent to the cylindrical jacket.

9. Developing apparatus according to claim 8, in which at least parts of the overflow passage are integral with the cylindrical jacket which is formed of a plastics material.

10. Developing apparatus according to claim 9, in which the lower wall of the overflow passage is integral with the insert cylindrical jacket and the remaining walls of the overflow passage are formed by a recess in the tank cover.

11. Developing apparatus according to any one of claims 1 to 10, in which components which affect the flow of bath liquid are disposed in the mixing beaker.

1 2. Developing apparatus according to claim 11, in which said components include a temperature sensor disposed transversely to the flow.

1 3. Developing apparatus according to claim 12, in which the temperature sensor, acting as a flow resistor, extends through an aperture in the tank cover and lies substantially in an axial plane which includes the axis of the impeller shaft.

14. Developing apparatus according to claim 11, in which the components comprise guiding surfaces, such as a coil, extending in the desired direction of flow.

1 5. Developing apparatus according to claim 10, in which the cylindrical jacket and the overflow passage component moulded integral therewith carry halves of connecting detent means, the complementary connecting halves being carried by the tank cover.

1 6. Developing apparatus according to claims 1 and 5, in which the lower end of the impeller shaft has a recess in its end to receive a mounting pin.

1 7. Developing apparatus for photographic sheet or strip material substantially as hereinbefore described and illustrated with reference to the accompanying drawings.