The invention relates to an apparatus for developing photographs inter alia colour photographs and photographic strips with the aid of a developing drum that can be heated "au bain-marie" and be driven rotatably about its longitu- dinal axis, to which and from which the fluids required for the development can be fed and evacuated respectively.

Such an apparatus is commercially available. In this known apparatus the developing drum can be closed by means of a cover. For introducing and evacuating the fluids required for development the drum has, each time, to be lifted out of the heating bath, after which the introduction and/or evacuation of fluids can be manually carried out.

The very serious disadvantage thereof is that the temperature of the developing process is insufficiently controlled. It should be noted that the temperature fluctu¬ ations in a developing process of colour photographs must not exceed an order of magnitude of 0.3° C. Obviously the known developing apparatus cannot satisfy this requirement so that the inadequate control of the process may result in great differences of colour reproduction. Usually the developing drum is cleaned by flushing with tap water so that it is drastically cooled. A limitation of the known device resides in that in consequence of the large number of processes involved in the development, particularly of colour photographs the probability of faults, for example, inaccurate dosing or false time setting is inadmissibly high. In practice it is found that this limitation gives rise to deviations from the desired dosings and times and hence to colour differences. Summarizing it is noted that the prior art is not sufficiently capable of controlling the temperature during all process steps of development and the setting of the required time intervals in a manner such that even utmost

care cannot sufficiently guarantee that photographs of constant colour quality can be produced.

The invention has for its object to obviate the mentioned drawbacks and limitations of the prior art and provides to this end apparatus of the kind set forth in the preamble, in which not only the developing drum but also all stock containers for the fluids required for development are placed in the fluid bath heating the developing drum and held therein during development. Preferably the developing drum comprises three coaxial compartments separated by transverse partitions, the first serving to receive the photograph or photographic strip to be developed, for which purpose it is closed at its free and remote from the transverse partition by a liquid- tight cover, the second containing means for supplying the fluids required for development in a liquid-tight and light-tight manner and the second and third compartments comprising means for the introduction and evacuation of the fluids used in a light-tight manner. A given embodiment it characterized in that the second compartment has a spiral-shaped wall of more than 360 extending around the rotary axis, the inner space of which communicates with one or more feeding ducts for the or all fluids required for development and the outer space is closed at its end by a partition and is in open commucation through an orifice in the transverse partition with the first compartment and in that the third compartment also has a spiral-shaped wall extending around the rotary axis, the outer end of which is in open communication channel extending across the second compartment along the peripheral wall thereof with the first compartment and the inner space is in open communication with a central outlet orifice

The first compartment preferably comprises a shell plate extending along the whole length thereof, the commu- nication channel being connected below said shell plate with the third compartment.

In a preferred embodiment the stock containers can be subjected to gas pressure and selecting and dosing means

are provided for successively feeding at will and in the desired amounts the fluids required for development to the second compartment.

Very simple is the embodiment in which the stock containers communicate with a common source of pressurized gas, for example air or nitrogen, and each of them communicated through an adjustable choke with the atmos¬ phere. By setting the respective chokes the amount of fluid supplied per unit time can be fixed at will. In this way expensive pump means can be dispensed with.

In order to ensure most accurate dosing it is pre¬ ferred to keep the fluid level in the stock containers always at least substantially constant, that is to say, independent of the filling degree of the stock containers, so that at a given pressure the level gauge is invariably constant. In this regard it is preferred to use floating stock containers.

A very reliable automatic operation is ensured by using a central control-unit for controlling the rotation of the developing drum and the synchronous energization of the selection and dosing means.

The invention will now be described more fully with reference to the drawing of a few arbitrarily chosen embodiments. The drawing shows in

Fig. 1 a perspective view, partly broken away, of an embodiment of the apparatus in accordance with the invention Fig. 2 a cross-sectional view of the device of Fig. 1, Fig. 3 a plan view of part of the device of Fig. 1, Fig. 4 a perspective, fragmentary view of a developing drum embodying the invention, some components being shown for the sake of clarity at relative, radial distances.

Fig. 5 a perspective, fragmentary view of the developing drum shown in Fig. 4, Fig. 6 a perspective view of part of the developing drum of Fig. 5, viewed away from the plane VI-VI,

Fig. 7 a perspective, fragmentary view of a preferred embodiment of the developing drum in accordance with the

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inventio ,

Fig. 8 a sectional view corresponding to Fig. 2 of a further embodiment of the device in accordance with the invention, Fig. 9 a stock container having a closing cap provided with the various ducts and

Fig. 10 a perspective view of a heat exchanger connect¬ ed between the developer container and the injection piece. Fig. 1 shows a developing device 1 in a first embodi- ment of the invention. This device comprises a trough 2 having a plurality of separated spaces to be described more fully hereinafter. A first space 3 serves to accomo- date at least partly a developing drum 4. The second space may comprise four stock containers 6, 7, 8, 9. A third space 10 serves as a buffer and preheating space and a fourth space 111 accommodates mechanic control- and actu¬ ating means to be described hereinafter. The first space 3 is not separated from the second space 5, though between them there is a rim for limiting the freedom of movement of the stock containers 6 to 9. In this way it is achieved that the water contained in the first space 3 rinses in addition the stock containers 6 to 9 so that it is ensured that during operation the developing drum 4 has the same temperature as the fluids required for development in the stock containers 6 to 9.

With the third space 10 communicated a cold water supply duct. A valve 15 regulated by a float 14 provides a substantially constant level of water 16 in the space 10. The space 10 comprises furthermore a heating element 17 with a thermostat.

Through a narrow orifice 18 having a non-return valve 128 formed by a thin, flexible skin fastened by its upper edge to the associated wall, the third space 10 communicates with the first space 3 and the second space 5. Owing to the buffer effect of the space 10 in conjunction with the narrow passage of the orifice 18 the resultant is such that the heating element 17 can sufficiently rapidly heat the water 16 without giving rise to temperature fluctuations

in the area of the developing drum 4.

There is furthermore provided an outlet 19 communi¬ cating on the one hand with the spaces 3 and 5 via an overflow 20 acting at a slightly higher level than the orifice 18 and on the other hand through an outlet duct 21 with outlet means 22 to be described more fully herein¬ after for conducting fluids used for development away from the drum 4.

In order to ensure a most homogeneous temperature the second space 5 ^' is provided with a stirrer 24 driven ro¬ tatably by a motor 23.

For rotatably driving the developing drum 4 a motor 25 drives through a rope 26 and a wheel 27 two ropes 28, 29 passing around a reversing roller 30. This reversing roller 30 is coupled with a frame 31, which is provided on the other side with carrying rollers 32, 33 for rotatably supporting the drum 4. The carrying roller 33 is furthermore provided with a flange 34 which serves as a stop member for limiting the freedom of axial movement of the drum 4.

In order to facilitate the introduction and removal of photographs into and out of the drum 4 respectively the frame 31 is tiltable by means of an eccentric cam shaft 36 tiltable about a tilting shaft 35 for co-operation with the frame 31 through blocks 37. The tilting shaft ^" 35 is coupled with a control-lever 38.

Before going over to the further Figures it is noted that herein the same reference numerals are used.

Fig. 2 shows more clearly than Fig. 1 how the develop- ing drum 4 is driven by the ropes 28, 29. The reversing roller 30 serves in addition as a carrying roller. There is furthermore provided a carrying roller 29 having a flange 40 which correspond with the carrying roller 33 and the flange 34 respectively, the arrangement being such that the drum 4 has only slight freedom of axial movement. It should be noted that in this embodiment the upper run of the rope 29 is in direct contact with the drum 4 in order to avoid slip of the rope with respect to the wheel.

Fig. 1 clearly shows the presence of a bent-over rim 41 at the top side of the upright walls of the trough 2. An elongate hole 42 allows the control-lever 38 to pass through the rim 41. The shaft 43 of the stirrer 24 passes through a hole 144 in the rim 41.

Fig. 3 shows, in a plan view important structural details of the first embodiment of the device in accordance with the invention so far described.

The fourth space 111 comprises a diaphragm pump 44 having an air inlet valve 45 and an air outlet valve 46, between which valves 45 and 46 a pump space 47 is bounded by the wall 48 of the diaphragm pump 44 and a diaphragm 49, which can be causes to vibrate by alternating-current energization by a solenoid 50. Through a flexible hose 51 the air outlet valve 46 communicates with a hollow piston rod 52 provided with a toothed rack 53 co-operating with a step motor 54 in a manner such that the active end 55 of the piston rod 52 can be placed in a plurality of selectable positions. These various positions correspond to the points of connection of pressure ducts 56, 57, 58, 59 on a cylinder 60 communicating with the stock containers 6, 7, 8 and 9 respectively. Through an opening 61 between two sealing rings 62, 63 at the active end 55 one of the stock containers 6 to 9 can be selectably subjected to the air pressure. Pressure equalisation in front of and behind the piston with the ambience takes place through orifices 142, 143. The stock containers 6 to 9 are connected with fluid ducts 64, 65, 66 and 67 respectively, which open out via a conically tapering sheath 144 in an inlet and outlet hood 68 adjoining the drum 4 in the state of operation.

The sheath 114 terminates by its broad end between the drum 4 and the hood 68 for conducting away fluid dripping from the ducts 64, 65, 66, 67.

From Fig. 3 it will be apparent that the developing drum 4 comprises three compartments i.e. a first compartment 69 for receiving a photograph or plain film to be developed, a second or inlet compartment 70 and a third or outlet compartment 71.

As will be seen in Fig. 3, the outlet 19 can be directly connected with a waste water outlet, for example, one or more tanks for used chemicals.

The selection of the various tanks intended each for one of the fluids can be carried out by a control coupled with that of the .step motor 54. The outlet 19 is adjoined by an outlet 129 of the first space 3. The outlet 129 comprises an outlet valve 72 that can be closed. The valve 15 with the float 14 added to the cold water supply duct 13 are shown only schematically in Fig. 3. The float 14 is adjusted to a water level lying between that of the orifice 18 and the overflow 20.

Before discussing the details of the developing drum 4 with reference to Fig. 4 it is noted, partially referring back to Fig. 1, that the stock containers 7, 8, 9 are provided with filling caps 73, 74, 75 for filling these stock containers with the required chemical fluids. The stock container 6, however, is not provided with a filling cap, but it is connected with a water supply duct 76. This water supply duct 76 communicated through a non¬ return valve 77 with the buffer and preheating space 10 so that preheated water can be fed to the stock container 6. The water contained in the stock container 6 is used first for presoaking during development as flushing water and subsequently for cleaning the developing drum 4.

Referring to Fig. 1 the stock containers 6, 7, 8, 9 are provided with flexible ducts 78, 79, 80 and 81, the other ends of which are connected with adjustable chokes 72, 83, 84 and 85. These chokes 82 to 85 are connected in common with a gas exhaust duct 86, which may have an outdoor outlet in order to prevent the operator of the device from respiring noxious gases.

By setting the chokes 82, 83, 84, 85 with the aid of the manually adjustable setting knobs 87, 88, 89, 90 the flow resistance from the interior of the stock containers to the atmosphere can be adjusted. By means of the gas pressure furnished by the diaphragm pump 44 an accurately determined flow rate can once be set for each separate

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stock container. It will be obvious that with regard to an optimum process control such an accurate, constant adjustment is of paramount importance.

With respect to the disposition of the ducts 78 to 81 and of the chokes 82 to 85 it is noted that for the sake of clarity of the.drawing they are shown on the front side in Fig. 1. In practice they are located on the other side of the stock containers 6 to 9 in order to facilitate filling of the stock containers 7, 8 and 9. Fig. 4 shows in further detail the structure of the developing drum 4. The three coaxial compartment 69, 70, 71 are separated by transverse partitions 91 and 92. The compartment 69 can be closed at its free end remote from the transverse partition 91 by a liquid-tight cover 93, which can provide a complete seal on a sealing ring 95 by means of a bayonet joint 94.

The second compartment 70 comprises a spiral-shaped wall 96 of about one and a half spiral turns or 540 around the rotary axis, the inner space 97 of said wall communicating in operation with the fluid ducts 64, 65, 66, 67 the exterior space 98 being closed at its end by a partition 99 and being in open communication through an orifice 100 in the transverse partition 91 with the first compartment 69. ^" The third compartment 71 also has a spiral-shaped wall 101 extending around the rotary axis, the outer end 102 of which is in open communication through a communication channel 103 extending along the circumferential edge of the second compartment 70 with the first compartment 69, whereas the interior space 104 is in open communication with a central outlet orifice 105. This central outlet orifice 105 opens out in the fluid inlet and outlet cap 68, which is connected in the manner shown in Fig. 1 with the outlet duct 21. Inside the third compartment 71, on the side remote from the active side of the wall 101, there is a space 130 not used for the developing process.

A weight 131 fastened to the drum jacket is arranged therein. By this weight 131 the drum equilibrium disturbed

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by the various elements disposed asymmetrically and eccentrically with respect to the drum wall is restored.

The first compartment 69 comprises a shell plate 106 covering the whole length thereof. The communication channel 103 adjoins below said shell plate 106.

Between the inner wall of the first compartment 69 and the shell plate 106 is located a helical rim 107, which adjoins the communication channel 103 for conducting away the fluid from the first compartment 69. The operation of the device so far described will now be briefly explained. By energizing the pump 44 and by moving the active end 55 of the hollow piston rod 52 by energizing the step motor 54 pressurized gas is intro¬ duced into the corresponding stock containers 6, 7, 8 or 9 so that the fluid is moved from the container concerned into the inner space 97 of the spiral-shaped wall 96. After the injection of the fluid into the second compartment 70 the fluid remains therein during the ro¬ tation 108. By the subsequent rotation 112 the fluid leaves the second compartment 70 and enters the first compartment 69, where it comes into contact with the photograph to be developed. Obviously the contact with the first processing fluid starts the development of the photograph. At the subsequent rotation 108 the fluid leaves the first compartment 69 and enters the third compartment 71, where it is conducted away through the spiral-shaped wall 101 via the outlet orifice 95. At the same time the next fluid is injected into the second compartment, after which the cycle described is repeated for the subsequent process step.

It should be noted that in this preferred embodiment rapid filling and evacuation occur only during the trans¬ ient rotation 108.

Owing to gravity the various, spiral-shaped walls operate so to say like pumps.

Figs. 5 and 6 show, though probably needless, a few structural details of the developing drum 4.

Fig. 8 shows a further embodiment 119 of a developing

device in accordance with the invention. The difference from the developing device 1 shown in Fig. 2 resides in that as is shown in Fig. 8 the drive takes place on the top side of the drum 4 whereas this is done on the under- side of the drum in Fig. 2. A motor 120 drives along rollers 121 a rope 122, which is further passed on a guide roller 123 and a reversing roller 124. The elements 120 to 124 are all arranged on a frame 125, which is pivotable about a hinge 126 fastened to the trough 2 between a working position indicated by solid lines and a rest position indicated by broken lines, in which the drum 4 can be removed from the device 119. In the device shown in Fig. 2 there is some risk of slip when the drum 4 is driven by the ropes 28 and 29. By performing the drive under pressure from the top slip is substantially excluded. The frame 125 can be locked in the working position by means not shown as indicated by solid lines.

Only Fig. 8 shows that in all embodiments shown the first space 3 is provided with a heating element 127 for controlling the temperature of the water 12 by means of a thermostat. In all embodiments the agitator 24 serves for obtaining optimally homogeneous temperatures.

The drawin does not show a central control-unit for controlling the rotation of the developing drum and for synchronously energizing the diaphragm pump 44 and the step motor 54.

Fig. 9 shows a stock container 132 having a closing cap 133. Through the top wall thereof are passed in sealing relationship a pressure duct 134 and a fluid duct 135. The duct 134 terminates on the side of the container 132. The duct 135 terminates near the bottom thereof. With the pressure duct 134 communicates a further pressure duct 136, which corresponds with the ducts 56, 57, 58, 59. The duct 135 corresponds with the ducts 64, 65, 66, 67. At the transition between the ducts 136 and 134 is provided a needle valve 137. By turning the knob 138 the passage between a seat 139 and a conical needle 140 can be varied. Thus a desired pressure drop can be obtained through the

opening 141. The needle 140 is axially displaceable and is urged by a very light compression spring 145 towards the seat 139 with regard to the desired pressure formation. It should be noted that the valve 137 corresponds to the chokes 82, 83, 84, 85. It will be obvious that the opening 141 may communicate with an outlet duct, for example, the duct 86.

In the embodiment shown the closing cap has a screw joint 142 in common with the container 132. In order to prevent rotation a bayonet joint may be preferred.

By using a closing cap with the associated ducts the stock container can be more readily replaced, which en¬ hances the flexibility of the device.

The trough 2 is preferably constructed or arranged in heat insulating fashion.

With respect to the disposition of the stock con¬ tainers 6, 7, 8, 9 it should be noted that by means of a slot-and-pin coupling they may be guarded against lateral dispalcement, horizontal rotation and tilting. The cap 68 may be bevelled at the top end towards the drum 4 for allowing the tilting movement of the drum 4. Fig. 10 shows a heat exchanger 146 comprising parallel thinwalled, long duct parts 147, which communicate through distribution drums 148, 149 with the stock container 9 containing the developer and the injection piece 67 respectively. The heat exchanger 146 is located in the space 3 below the drum 4. This configuration implies an extreme accuracy of the temperature of the developer intro¬ duced into the drum 4. For the other fluids such accuracy is not necessary.

It will be obvious that the embodiments described and illustrated are only examples for illustrating the prin¬ ciples of the invention. Many modifications of components and of their relationship may be carried out without exceeding the scope of the invention.

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