GB2094671A - Fluid treatment apparatus - Google Patents

Description

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GB 2 094 671 A

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SPECIFICATION

Fluid treatment apparatus

5 The present invention relates to fluid treatment apparatus.

The invention has been designed primarily to treat • photographic elements such as prints, films etc, but is equally applicable to other fluid treatment proces-10 ses, such as electroplating, electroless plating,

dieing etc.

In the treatment of film material, one of the major problems is the oxidization of the chemicals, particularly developers. The problem is usually overcome 15 either by keeping the surface to volume ratio as small as possible or by discarding the chemicals after each use. The former method which is used in continuous film processors has the disadvantage that the apparatus is complex requiring pumping or 20 stirring arrangements to be employed to circulate the large volumes of chemicals and to provide the bulky storage vessels, usually with a capacity of approximately 100 litres. The initial cost of the chemicals is very high because the tanks have to be 25 deep in order to minimize the surface to volume ratio. The loss from the surface of the containers results in high energy costs in order to maintain the precise temperature necessary. If the chemicals are discarded as is used in batch processes, this is 30 extremely expensive in chemicals.

It is now proposed, according to the present invention, to provide a fluid treatment apparatus comprising a plurality of open topped tanks for liquid, juxtaposed in side-by-side relation, at least 35 one suspension device, a carrier mounted on the suspension device for carrying an article to be treated, means for raising and lowering the suspension device and for transporting it laterally, whereby the carrier can be sequentially immersed in liquid in 40 each tank, and means to reciprocate the suspension device vertically within each tank.

Such a construction can be extremely simple and relatively inexpensive. The vertical reciprocation of the suspension device, together with its carrier, 45 enables one to do without any circulation or stirring device, and without the requirement for nitrogen bursts to be used, which have previously been used before to give the necessary agitation. The vertical reciprocation can be such as to give the necessary 50 amount of agitation, yet still not be sufficiently violent to cause any streaking.

The suspension device may comprise a hanger which projects beyond each end of the associated tank and the means for raising and lowering the 55 suspension device and for transporting it laterally may comprise two rails extending outwardly of the ends of the wall of the tanks, and means to move the rails upwardly, laterally and then downwardly, so that the rails engage the projecting portions of the 60 hanger and raise the hanger upwardly to remove the suspension device from the tank, transported laterally and then lower it into the next tank. Such a structure can be very simple and can be constructed for example, as two sprocket chains on each side of 65 the tank, the sprocket chains carrying a fitting which moves with one of the links of each chain and causes the circulating motion of the rails. This motion can be stopped when the hanger has been deposited on the side of the tank.

The means to reciprocate the suspension device vertically may comprise two bars which extend laterally along the ends of each of the tanks, the bars engaging the projecting ends of the hangers, means being provided to reciprocate the bars vertically.

This may be achieved, for example, by four flexible elements which pass over pulleys, one flexible element being secured to each end of each bar and a common drive mechanism being provided to pull the flexible elements simultaneously.

In order to improve the agitation within each tank, means are advantageously provided to rotate the carrier within the tank. These may, for example, comprise a pawl within each tank and a ratchet on each carrier, whereby, as the suspension device is reciprocated vertically, the ratchet engages the pawl and is rotated thereby. It is important that the rotation should be not too great so that the carrier is in effect simply indexed around and a further pawl may be provided to prevent any reverse rotation of the ratchet.

In orderto reduce the amount of evaporation, loss of heat, and tendency for any oxidation, at least one door or lid may be provided to overlie the liquid in the tank, means being provided to open the door as the carriers are lowered into the tank and to close the door firstly as the carriers are lowered further into the tank and secondly, as the carriers are raised out of the liquid.

According to another aspect of the present invention, there is provided fluid treatment apparatus comprising a plurality of open topped tanks for liquid juxtaposed in side-by-side relation, at least one suspension device, a carrier mounted on the suspension device for carrying an article to be treated, means for raising and lowering the suspension device and fortransporting it laterally, whereby the carrier can be sequentially immersed in the liquid in each tank and at least one door overlying the liquid in each tank and means to open the doors as the carriers are lowered into the tanks and to close the doors firstly as the carriers are lowered further into the tanks and secondly, as the carriers are raised out of the liquid.

Two doors may be associated with each tank, each door floating ontheliquidin the tank. The suspension devices may be provided adjacent each end,

with a cam engageable with the doors to tilt the doors by pressing them downwardly at a location spaced from the lateral centre of the door. A further cam may be provided at the centre of each suspension device.

Advantageously each tank includes on each end, a central inwardly projecting rib to prevent each door from moving from its own half of the tank.

Each door may comprise, adjacent each each edge spaced apart elements which project from each face to prevent the doors from sticking to the sides of the tank. This is particularly important as the doors become vertical and are usually pressed by the suspension device against the side of the tank. The

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doors could readily adhere by capillary action to the tank and the provision of these projecting elements prevents this from happening.

A drier section may be located adjacent the most 5 downstream tank, means being provided for raising and lowering the suspension device and transporting it laterally to deposit the suspension device in the drier section to a conveyor therein. The ratchets which are provided on the carriers can engage 10 abutments whereby the carriers are rotated as they move through the drier section.

In orderthatthe present invention may more readily be understood, the following description is given, merely by way of example, reference being 15 made to the accompanying drawing in which:-

Figure 1 is a schematic side elevation of one embodiment of apparatus according to the invention;

Figure 2 is an end view of certain parts of the 20 apparatus of Figure 1, shown purely schematically;

Figure 3 is a perspective view of one of the tanks showing a suspension device therein;

Figure 4 is an exploded enlarged view of a portion of the tank illustrated in Figure 3 with certain parts 25 added which were omitted from Figure 3 for clarity;

Figure 5 shows nine views of the carrier being lowered into the tank and the various positions which the doors adopt; and

Figure 6 is a schematic perspective view illustrat-30 ing the formation of the doors.

Referring first to Figure 1 of the drawings, there is illustrated therein a support plate 10 with eight identical tanks mounted thereon in side-by-side juxtaposed relationship, these being being indicated 35 by the reference numerals 11 to 18 respectively. The exterior configuration and size of the tanks is identical but some of the tanks have somewhat different internal fittings as will be explained later.

Mounted on the support plate 10 adjacent each 40 end thereof are pairs of sprockets including a tower sprocket 19 and an upper sprocket 20 at the lefthand end and a lower sprocket 21 and an upper sprocket 22 at the righthand end. Arranged around sprockets 19 and 20 is a preferably plastics material sprocket 45 chain 23 which is caused to move in the direction indicated by the arrow 24. Rotation of the sprocket 19, and thus of the sprocket chain 23 is effected by a further chain 25 driven by a common motor 26. The motor 26 also serves to drive, via a chain 27, the 50 lower sprocket 21 of the righthand pair of sprockets, thus driving the sprocket chain 28 in the direction indicated by the arrow 29, whereby the upper sprocket 22 rotates simultaneously. Further sprockets (which cannot be seen in this drawing) are 55 provided behind the tanks and these are caused to rotate simultaneously, because the lower sprockets 19 and 21 each have a common axle which passes to the back of the apparatus and forms the axle for the lower rear sprockets. The upper sprocket 20 and 22 60 are provided with stub axles only, so that a clearance is left between the two top sprockets both on the lefthand side and on the righthand side, for the reason which will be apparent later.

The chain 23 is provided, at the junction of one of 65 its pairs of links, with a pivotal fitting 30 formed of stainless steel, while the chain 28 is provided with a similar fitting 31. Again, further fittings are provided at the back which correspond. Pivotally mounted on the fittings 30 and 31 is a lifting rail 32, the rail 32 lying on the axially outer side of the chains 23 and 28. A similar rail, of course, is provided behind the two rear sets of chains at the back of the tanks. The arrangement of the rear rail can be seen from Figure 2, which is an end elevation as viewed from the right showing the drive mechanism and the common shaft 21A driving the two bottom sprockets. It will be appreciated, therefore, that as the motor 26 is rotated in a clockwise sense as viewed in Figure 1, the rails 32 are caused to rise, move to the right and then lower, move to the left and then rise again.

If one now refers to Figure 3, one will see the formation of one of the tanks. Byway of illustration this tank has been indicated by reference numeral 11. The tank includes end walls 40 and 41 connected by two relatively long side walls 42 and 43. It will be seen that the end walls are each provided with a steep-sided V-slot44. Two centreing arms are mounted in each tank, these each consisting of a vertical arm 45 pivotally connected at 46 to the adjacent end wall 40,41, so as to hang down from the pivot, the two arms 45 being connected by the centreing bar 47. For ease of illustration only one bar 47 has been shown and it is identical to the other bar which has only been shown very schematically.

Figure 3 shows a suspension device engaged in the two slots 44. The suspension device comprises a hanger 50 having two downwardly extending projections 51 formed thereon, these projections being spaced apart by a distance greater than the front to back length of the tank. Two apertures 52 spaced apart from one another, are provided in the hanger 50 and through these apertures pass two pillars 53 which are interconnected above the hanger by a strap 54.

At their lower ends the pillars 53 each carry an end flange or cam 55 of a diameter slightly less than the width of the tanks as will be explained later. Each cam 55 is provided with an oblique slot 56, the inner end of which terminates at the centre of the cam 55; the two cams 55 are interconnected by two crossbars 57.

Pivotally mounted on the inner wall of the tank, at one end thereof, is a pawl 60 having a pivot axis 61 and a pin 62 at the lower end. The pin 62 is engageable with a ratchet 63 (see Figure 4) mounted on the axis 64 of a photographic material carrier (otherwise not shown). The carrier may be of any suitable type, for example a spiral or a cylindrical member into which the film or other photographic material can be attached. The carrier will take a different form depending upon the material being treated. A further pawl 65 is pivotally mounted on the outer surface of the adjacent cam 55 and has a pawl pin 66 engageable with the teeth of the ratchet 63 to prevent the ratchet from rotating backwards.

Referring again to Figure 1 of the drawings, a further motor-gearbox 70 is mounted below the plate 10 at the centre thereof and has an output shaft 71 extending vertically downwardly. The shaft 71 has lower and upper eccentric arms 72 and 73

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carrying vertically extending pins 74 and 75 respectively. Engaged over the pins 74 and 75 is a ring member 76,77, which is retained in place by a suitable retainer (not shown).

5 At each end of the plate 10 there are provided four pulleys, only two of which can be seen at each end in the drawing, these including, at each end, two pulleys 80 mounted for rotation about a vertical axis and two pulleys 81 mounted for rotation about a 10 horizontal axis. Further pulleys 82 are mounted at the front and back at each end of the apparatus at a location above the top of the tanks. Two cords 83 are connected to the ring member 77, each pass first over the vertical axis pulley 80 and then over the 15 horizontal axis pulley 81, and upwardly over the upper pulley 82. Adjacent the top, the cords 83 pass through a hole in a mounting plate 84 before passing over the pulley 82 and then down to be secured to the mounting plate 84 again. Adjustment of the 20 position of the mounting plate can be achieved by passing the cord downwardly through a further aperture in the plate providing some securing such as a collar provided with a grub screw.

The plates 84 carry a bar 85 which extends along 25 the front of the tank. A similar bar extends along the back of the tanks and the mounting plate 84 at the lefthand end of the tanks are secured together by a crossbar 86 which extends along the lefthand end of the tank 11.

30 Two further cords 87 are secured to the ring member 76 and are caused to pass along an identical path to be secured to a further mounting plate 84 at the righthand end of the tank, this also having a crossbar 86 associated therewith. The mounting 35 plate 86 is, it will be understood, secured to the other end of the bar 85.

As the motor 70 is rotated, the eccentric arms 72 carry out an orbiting motion and the two cords 83 and the two cords 87 are pulled simultaneously by 40 identical amounts. This will cause the rail 85 at the front and the rail 85 (not shown) at the back, to be reciprocated vertically simultaneously.

If reference is now made to Figure 6, it will be seen that there are provided, in each tank, two doors 90 45 which are identical to one another. The doors are of a generally rectangular cross-section and together take up substantially the whole surface area of the associated tank. The doors are themselves formed of airfilled PVC and carry on each surface three closed 50 cell rigid foam material floatation pads 91,92,93 which are slightly spaced apart from one another.

Spaced outwardly projecting spacer skids 94 are provided to extend above and below the upper and lower surfaces respectively of the doors adjacent 55 each edge thereof. A recess is formed adjacent the skids 94 to accommodate the pillars 53 on the carrier. Two doors are provided in each tank for chemicals and these doors float on the surface of the liquid and substantially coverthis surface, thereby 60 reducing to a minimum the oxidation of the chemical, evaporation of the chemical and the loss of heat.

The carrier for film material may include the shaft 64 previously described and the ratchet 63 mounted on the end thereof. A series of angular spaced plates 65 may extend generally radially from the shaft 64 and have radially outwardly extending projections formed thereon, these projections being arranged along a helix so that a length of film can be wrapped loosely around the plates and the successive convolutions are spaced apart by the projections. Preferably the lateral surfaces of the projections are chamfered so that, once a film has been wrapped around, and held loosely at its ends, it will relax slightly thereby preventing the film from being unduly tensioned at any point.

In operation of the above described apparatus, the carrier, such as the carrier described above, is assembled onto the suspension device, by slipping the shaft 64 down the inclined slots 56, the shaft then being centred at the centre of the discs 55. Distance pieces are provided on the shaft 64 to engage on the axially outer faces of the discs 55. The suspension device is then offered up to a pair of feed rails (not shown) mounted to the left of the apparatus illustrated in Figure 1.

In order to carry out one particular photographic process, the tank 11 is filled with developer, and tanks 12 and 13 with bleach. Tank 14 is filled with water while tank 15 and 16 each have fixer. Tank 17 is again a wash tank and thus is filled with water, while tank 18 contains stabilizer.

The motors 26 and 70 are started, and the first suspension device is moved off its feed rails onto the rail 32. The rail 32 will at this time be moving upwardly and it will therefore take the suspension device over the top of the sprocket 20 whereby the carrier mounted on the lower end of the suspension device will clearthe lefthand wall of the tank 11. As the suspension device moves around the righthand side of the sprocket 20, the suspension device will begin to be lowered into the tank 11. As the suspension moves down, the two cams 55 will abut the centreing bars 47 which will pivot slightly away from one another, but will nonetheless centre the suspension device accurately in the lateral centre of the tank 11. As the suspension device continues to be lowered, the hanger 50 will pass into the two slots 44 in the sides of the tank and the cam 55 will abut the pieces of the door between the floatation members 91,92 and 92,93 causing the door to tilt. The actual movement of the doors is illustrated more clearly in Figure 5. In Figure 5(1) the effect of the centreing device is illustrated. In Figure 5(2) and 5(3) it will be seen how lowering of the suspension devices will cause the doors, which are floating on the top of the liquid in the tank 11, to pivot so that they assume a progressively more vertical position. As the door gets to the position illustrated in Figure 5(4) the doors flop over onto the upper surface of the cams 55 and eventually, when the cams have got fully into the liquid in the tank, the doors close as illustrated in Figure 5(5). At a certain position of the sprocket chain 23 and of the sprocket chain 28, the rails 32 gets to a location below the bars 85, so that the ends of the hangers 50 are lowered onto the bars 85. In fact the sprockets will continue to rotate for a certain time until they take up the position approximately as shown in Figure 1 whereupon the motor 26 will stop for a predetermined period.

The effect of the motor 70, as explained previously

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is to cause the bars 85 to be reciprocated vertically. This reciprocation is also carried out on the suspension device so that the carrier is vertically reciprocated as indicated schematically in Figure 5(5). Now 5 as the vertical reciprocation takes place, the ratchet 63 will, on each downward movement of the reciprocation engage on the pin 62 of the pawl 60. This will cause the ratchet to be rotated and the film carrier to be rotated with it. The rotation will be through a 10 certain number of degrees, usually approximately 60°. Reverse rotation of the ratchet is prevented by the second pawl 65 and the next time the carrier will be caused to rotate is at the next downward movement of the suspension device. Thus, it will be 15 appreciated, a double agitation effect takes place. Firstly there is a vertical reciprocation in the tank and secondly, there is the indexed rotary motion, this causes a certain amount of turbulence in the liquid thus giving a thorough mixed processing of the film. 20 Of course, the degree of agitation is not violent and thus the emulsion on the film or other photographic material will not be disturbed, but there will be no tendency for streaking, because of the gentle double agitating effect.

25 The motor 26 is operated again, after a suitable interval, so that the rails 32 are once again raised and the suspension device is thus lifted out of the tank 11. The way in which the doors open to allow this to happen is illustrated at Figure 5(7) and after the 30 suspension device has risen further, the doors begin to close again (Figure 5(8)) until the door is fully closed as seen in Figure 5(9). The motor 26 then stops for a very short time, for example 10 seconds and the chemical is allowed to drip from the 35 suspension device and carrier. The operation is then carried out as previously so that the carrier is moved into the tank 12 and thence into the tank 13. There are two tanks provided here to give a double length of immersion time in the bleach for the particular 40 chemistry of this film. In certain cases it is advantageous for air to be passed into the tanks 12 and 13. Continued operation will move the suspension device into tank 14 through which water is passed continuously to wash the film. The suspension 45 device is carried on further into the succeeding tanks in exactly the same manner.

If reference is again made to Figure 3 of the drawings it will be noted that vertically extending ribs 59 is provided on the inner surface of the tank at 50 each end immediately below the notch 44. The purpose of this is to prevent the doors from riding over one another as they flop over for the position illustrated in Figure 5(4) to the position of Figure 5(5) or from the position of Figure 5(8) to the position in 55 Figure 5(9).

Afterthe suspension devices have left the last tank 18, they are moved into a discharge section which is only illustrated very schematically and may include a drier tunnel. A further sprocket chain 110 is passed 60 around the various wheels so as to have an upper run 111, the chain being driven via yet another sprocket chain 112 by the same motor 26.

Adjacent the upper run 111 is a horizontally reciprocable member 113 having several pivotally 65 mounted wires 114thereon, these wires extending horizontally to adjacent the upper run 111. Now as the suspension device is lowered having passed over sprocket 22, it is deposited on the upper run 111 and initially clears the wires 114. The horizontal reciprocation of member 113 is caused via a linkage, (not shown) from motor 70. The wires 114 are arranged to engage the ratchet 63 on the carrier. The gearing is such that the sprocket chain 110 will move the suspension device along the upper run 111 at the same effective speed as a suspension device is moved laterally through the apparatus. Therefore, the suspension device which has previously been deposited on the upper run 111 will be a sufficient distance from the sprocket chain 28 to enable the next carrier to be deposited on the upper run without hindrance from its predecessor. Because the wires 114 engage the ratchet 63, there will be a limited rotation of the carrier, thus preventing the film material having drips of liquid depositing in any particular place. The indexed rotation thereby provided can reduce the necessary drying time significantly and thus reduce the necessary length of the tunnel. Preferably, a fan heater is provided to project hot air into the tunnel to expedite the drying. The fan heater would be provided with a filter to prevent dust blowing into the tunnel.

Any form of discharge rail can be provided at the righthand end of the upper run 111.

It will be appreciated that several suspension devices can be applied sequentially so that there is one moving into each tank in turn to increase the throughput of the apparatus.

Other forms of carrier may be supplied for photographic material. For example, the carrier may take the form of a hollow cylinder having, for example, holes therein, the hollow cylinder being provided with an end cap having a flange on the outer surface of the cylinder, and this can be used to hold a large format film which will be mounted with the emulsion side inwards.

Anotherform of carrier includes a generally rectangular frame mounted on the shaft 64 and this frame having suitable clips to support a regular film.

A further concept is for the carrier to be in the form of a simple bottom rail with upstanding spigots thereon, the spigots being used to mount a conventional stainless steel or plastic film spiral.

Other forms of carriers could be used for other processing. For example, a perforated cage or barrel could be provided for electroplating small articles. Alternatively a suitable clamping arrangement could be provided for supporting larger articles.

Claims (1)

1. Fluid treatment apparatus comprising a plurality of open-topped tanks for liquid, juxtaposed in side-by-side relation, at least one suspension device, a carrier mounted on the suspension device for carrying an article to be treated, means for raising and lowering the suspension device and for transporting it laterally, whereby the carrier can be sequentially immersed in liquid in each tank, and means to reciprocate the suspension device vertically within each tank.

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2. Apparatus according to claim 1, wherein the suspension device comprises a hanger projecting beyond each end of the associated tank and wherein the means for raising and lowering the suspension

5 device and for transporting it laterally comprise two rails extending outwardly of the ends of all of the tanks, and means to move the rails upwardly, laterally and then downwardly so that the rails engage the projecting portions of the hanger and 10 raise the hanger upwardly to remove the suspension device from the tank, transport it laterally, and lower it into the next tank.

3. Apparatus according to claim 2, wherein the means to reciprocate the suspension device vertical-

15 ly comprise two bars extending laterally along the ends of each of the tanks, the bars engaging the projecting ends of the hangers and means being provided to reciprocate the bars vertically.

4. Apparatus according to claim 3, wherein the 20 means to reciprocate the bars vertically comprise four flexible elements which pass over pulleys, one flexible element being secured to each end of each bar and a common drive mechanism to pull the flexible elements simultaneously. 25 5. Apparatus according to any preceding claim, wherein means are provided to rotate the carrier within the tank.

6. Apparatus according to claim 5, wherein said means comprise a pawl within each tank, and a

30 ratchet on each carrier, whereby as the suspension device is reciprocated vertically, the ratchet engages the pawl and is rotated thereby.

7. Apparatus according to claim 6, and including a further pawl adapted to prevent reverse rotation of

35 the ratchet.

5. Apparatus according to any preceding claim, further comprising at least one door overlying the liquid in the tank and means to open the door as the carriers are lowered into the tank and to close the

40 doors firstly as the carriers are lowered further into the tank and secondly, as the carriers are raised out of the liquid.

9. Fluid treatment apparatus comprising a plurality of open-topped tanks for liquid juxtaposed in

45 side-by-side relation, at least one suspension device, a carrier mounted on the suspension device for carrying an article to be treated, means for raising and lowering the suspension device and for transporting it laterally, whereby the carrier can be 50 sequentially immersed in the liquid in each tank and at least one door overlying the liquid in each tank and means to open the doors as the carriers are lowered into the tanks and to close the doors firstly, as the carriers are lowered further into the tank and 55 secondly, as the carriers are raised out of the liquid.

10. Apparatus according to claim 8 or 9, wherein there are two doors associated with each tank, each door floating on the liquid.

11. Apparatus according to claim 10, wherein the 60 suspension devices are provided adjacent each end with a cam engageable with the doors to tilt the doors by pressing them downwardly at a location spaced from the lateral centre of the door.

12. Apparatus according to claim 11, and further 65 comprising a further cam at the centre of each suspension device.

13. Apparatus according to any one of claims 10,11 or 12, wherein each tank includes, on each end, a central inwardly projecting rib to prevent each

70 door from moving from its own half of the tank.

14. Apparatus according to any one of claims 8 to 13, wherein each door comprises, adjacent each edge, spaced apart elements which project from each face to prevent the doors sticking to the sides of

75 the tank.

15. Apparatus according to any preceding claim and further comprising a drier section located adjacent the most downstream tank and wherein means for raising and lowering the suspension device and

80 for transporting it laterally, deposit the suspension device in the drier section onto a conveyortherein.

16. Apparatus according to claim 15, wherein the carriers are provided with a ratchet, and wherein the drier section includes abutments to engage the

85 ratchets whereby the carriers are rotated as they move through the drier section.

17. Apparatus according to any preceding claim, wherein the carrier comprises a shaft, a series of angularly spaced plates extending generally radially

90 from the shaft and having radially outwardly extending projections formed thereon, these projections being arranged along a helix, so that a length of film can be wrapped loosely around the plates and the successive convolutions are spaced apart by the

95 projections.

18. Apparatus according to claim 17, wherein the lateral wall surfaces of the projections ere chamfered.

19. Fluid treatment apparatus substantially as 100 hereinbefore described with reference to and as illustrated in the accompanying drawings.

New claims filed on 26/3/82 Superseded claims 1-19 105 New or amended claims:-

1. Fluid treatment apparatus comprising a plurality of open-topped tanks for liquid, juxtaposed in side-by-side relation, at least one suspension device,

110 a carrier mounted on the suspension device for carrying an article to be treated, means for raising and lowering the suspension device and for transporting it laterally, whereby the carrier can be sequentially immersed in liquid in each tank, means 115 to reciprocate the suspension device vertically within each tank, and means to rotate the carrier within each tank.

2. Apparatus according to claim 1, wherein the suspension device comprises a hanger projecting

120 beyond each end of the associated tank and wherein the means for raising and lowering the suspension device and for transporting it laterally comprise two rails extending outwardly of the ends of ail of the tanks, and means to move the rails upwardly, 125 laterally and then downwardly so that the rails engage the projecting portions of the hanger and raise the hanger upwardly to remove the suspension device from the tank, transport it laterally, and lower it into the next tank.

130 3. Apparatus according to claim 2, wherein the

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means to reciprocate the suspension device vertically comprise two bars extending laterally along the ends of each of the tanks, the bars engaging the projecting ends of the hangers and means being 5 provided to reciprocate the bars vertically.

4. Apparatus according to claim 3, wherein the means to reciprocate the bars vertically comprise fourfiexible elements which pass over pulleys, one flexible element being secured to each end of each

10 bar and a common drive mechanism to pull the flexible elements simultaneously.

5. Apparatus according to any preceding claim, wherein said means to rotate the carrier within each tank comprise a pawl within each tank, and a ratchet

15 on each carrier, whereby as the suspension device is reciprocated vertically, the ratchet engages the pawl and is rotated thereby.

6. Apparatus according to claim 5, and including a further pawl adapted to prevent reverse rotation of

20 the ratchet.

7. Apparatus according to any preceding claim, further comprising at least one door overlying the liquid in the tank and means to open the door as the carriers are lowered into the tank and to close the

25 doors firstly as the carriers are lowered further into the tank and secondly, as the carriers are raised out of the liquid.

8. Apparatus according to claim 7, wherein there are two doors associated with each tank, each door

30 floating on the liquid.

9. Apparatus according to claim 8, wherein the suspension devices are provided adjacent each end with a cam engageable with the doors to tilt the doors by pressing them downwardly at a location

35 spaced from the lateral centre of the door.

10. Apparatus according to claim 9, and further comprising a further cam at the centre of each suspension device.

11. Apparatus according to any one of claims 8,9

40 or 10, wherein each tank includes, on each end, a central inwardly projecting rib to prevent each door from moving from its own half of the tank.

12. Apparatus according to any one of claims 7 to 11, wherein each door comprises, adjacent each

45 edge, spaced apart elements which project from each face to prevent the doors sticking to the sides of the tank.

13. Apparatus according to any preceding claim and further comprising a drier section located adja-

50 cent the most downstream tank and wherein means for raising and lowering the suspension device and fortransporting it laterally, deposit the suspension device in the drier section onto a conveyor therein.

14. Apparatus according to claim 13, wherein the

55 carriers are provided with a ratchet, and wherein the drier section includes abutments to engage the ratchets whereby the carriers are rotated as they move through the drier section.

15. Apparatus according to any preceding claim,

60 wherein the carrier comprises a shaft, a series of angularly spaced plates extending generally radially from the shaft and having radially outwardly extending projections formed thereon, these projections being arranged along a helix, so that a length of film

65 can be wrapped loosely around the plates and the successive convolutions are spaced apart by the projections.

16. Apparatus according to claim 15,whereinthe lateral wall surfaces of the projections are cham-

70 fered.

17. Fluid treatment apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1982.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.