US3521544A - Top drive for photographic processing machines - Google Patents

Description

July 21, 1970 P. J. GOOD 3,521,544

To? DRIVE FOR PHOTOGRAPHIC PROCESSING MACHINES Filed OCI. 25, 1967 3 Sheets-Sheet 1 gg: NT i n x9 va. mmm

N1 i Mm a? "lV a July 21, 1970 3,521,544

TOP DRIVE FOR PHOTOGRAPHIC PROCESSING MACHINES Filed Oct. 25. 19.67

P. J. Goop 3 Sheets-Sheet 2 FIG. .3A

21, P. J, GOOD TOP DRIVE FOR PHOTOGRAPHIC PROCESSING MACHINES Filed Oct. 25, 1967 5 Sheets-Sheet 5 las la? '4' V las /3/ l /oa I 65 [05a ,5l /l/a /la United States Patent O 3,521,544 TOP DRIVE FOR PHOTOGRAPHIC PROCESSING MACHINES Paul J. Good, Springwater, N.Y., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn.,

a corporation of Delaware Filed Oct. 25, 1967, Ser. No. 677,948 Int. Cl. B65h 17/20, 17/22; G03d 3/12 U.S. Cl. 95--94 8 Claims ABSTRACT OF THE DISCLOSURE A photographic processing machine designed for advancing continuous strips of lm, such as motion-picture film, through various processing baths in a path of travel which goes repeatedly upwardly and downwardly in a liquid bath, around idle guide rollers near the bottom of the bath, and over drive rollers near the top of the bath. Each set of drive rollers is loosely mounted on a driven shaft, each roller having an internal annular flange having frustoconical or tapered sides, engaged between flexible drive disks fixed to and rotating with the drive shaft, so arranged that when the downward pull on the drive roller is increased, due to an increase in the tension on the lilm passing over the roller, the roller is pulled downwardly relative to the shaft on which it is loosely mounted, thus causing the flexible drive disks to be forced slightly apart and to engage in driving relation with a portion of the annular flange closer to the periphery of the drive roller, thereby causing slower rotation of the drive roller. On the other hand, when there is less tension on the film passing over the drive roller, there is less downward pull on the drive roller and the drive disks make driving contact with a portion of the annular flange closer to the center of the drive roller, so that the drive roller is driven at a faster rate. In this way, the speed of the drive roller is varied in accordance with the degree of tension on the film passing over the roller, so that the film is kept taut but without excessive tension which might break the lm.

BACKGROUND OF THE INVENTION In photographic processing machines for moving long strips of sensitized photographic material through liquid baths, it is found that the strip of sensitized material tends to increase some-what in length, as it becomes wetter during passage through the machine, and then shrinks or decreases in length after it issues from the last liquid bath and becomes drier, possibly passing through a special drying chamber. The sensitized strip being treated may be and usually is a iilm strip, such as a long piece of motion picture film, or several shorter pieces of still picture film stapled or otherwise fastened to each other to make one long strip. But at times the processing apparatus may be used for processing long strips of paper, rather than film, and when paper is being processed, the expansion and contraction due to wetting and drying is even more noticeable.

This lengthwise expansion and contraction poses a serious problem, in keeping the strip (whether it be film or paper) sufficiently tight on the driven rollers so that the rollers will drive `the film which passes over them, and yet not so tight as to run the risk of breakage of the strip. Moreover, if there is excessive looseness, the lower ends of the downward loops of the strip, approximately at the bottom of the liquid bath, may be so loose that they run off ofthe bottom guide rollers or pulleys, and become tangled with other adjacent loops.

In the prior art, various arrangements have been proposed, but there has been no truly satisfactory solution.

For the sake of economy of floor space, there is usually a considerable number of pulleys mounted side by side on the same shaft, the strip to be processed going first over one pulley on the top shaft, then over one pulley on a bottom shaft near the bottom of the bath, then up and over a second pulley on the top shaft, along side of the first pulley, then downwardly and over a second pulley on the bottom shaft, then upwardly again and over a third pulley beside the second one on the top shaft, then down to a third pulley on the bottom shaft, and so on. There may frequently be as many as 16 or 18 pulleys mounted side by side on the same shaft, or even a greater number in some cases. There may be an appreciable change in length in the strip from the time it passes over the first pulley on a given shaft to the time it passes over the last pulley on the same shaft, and therefore, if the length expands, the last pulley on the shaft should he driven at a slightly faster rate than the first pulley on the same shaft. In the prior art, there has been no satisfactory way of varying the speed of driving different pulleys on the same shaft. The speed of rotation of the drive shaft itself can, of course, be varied by conventional variable speed drive means, but this would not solve the problem of having different pulleys on the same shaft rotate at different speeds in order to accommodate expansion (or contraction) of the length of the strip of material being process, between the time it passes over the first drive pulley on the shaft and the time it passes over the last drive pulley on the same shaft. With the present invention, however, different drive pulleys on the same shaft may be driven at different speeds, depending upon the tension of the particular loop of the strip which passes over the particular pulley, in such fashion that when there is no tension on the loop and thus no force tending to displace the drive pulley relative to the shaft, the pulley rotates at the same rotational speed as the shaft, but when there is substantial tension on the loop passing over the pulley, this displaces the pulley to an eccentric position relative to the shaft, thereby slowing the rate of rotation of the pulley. In other words, the greater the tension on the loop of strip material passing over a particular pulley, the slower the pulley is driven, and the less the teusion of the loop, the faster the pulley is driven, the maximum speed of rotation of the pulley being equal to the speed of rotation of the shaft. Thus, in actual operation, the long strip of material being processed, in passing over several pulleys on the same shaft and several sets of pulleys on different shafts, is kept at an approximately uniform degree of tension (once a state of equilibrium has been reached) through the entire length of the strip from its first entrance into the machine to its last exit therefrom, in spite of the fact that the length of the strip may expand or contract during passage through the machine.

BRIEF DESCRIPTION OF THE DRAWINGS' In the accompanying drawings, which constitute a material part of the disclosure and are incorporated herein by reference, and which show au illustrative embodiment of the invention:

FIG. l is a plan of a processing machine in accordance with a preferred embodiment of the invention;

FIG. 2 is side elevation thereof, with parts broken away to illustrate some of the interior construction;

FIG. 3 is a vertical section taken transversely through the machine, with parts omitted and parts broken away;

FIG. 4 is a schematic View similar to a fragment of the upper part of FIG. 3, on a larger scale, illustrating the action of increased tension on a drive roller pulling the roller down to an eccentric position relative to the drive shaft, causing slower driving of the roller; and

FIG. 5 is a view similar to a portion of FIG. 3, illustrating an alternative form of driving connections for the Patented July 21, 1970 roller drive shaft when the drive shaft is below the liquid level in the processing bath, rather than above it as in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 show a typical photographic processing machine of the kind in which the present invention is particularly useful. Except for the top drive rollers which will be described in more detail below, the main features of the processing machine are conventional and well known in the art, and are here shown only schematically. The machine may comprise, for example, a casing 11 containing conventional driving motors and control equipment. Mounted on the side of the casing 11 is the supply reel 12 from which the film strip 13 is drawn, the film passing over a guide roller 14 and up to idle guide rollers 15 and 17, then around a vertically movable slack take-up roller 19, and upwardly to another idle guide roller 21, then around metering rolls 23, and onward into the liquid bath processing tanks resting on a framework 25. There may be any desired number of processing baths, each in a separate tank, depending upon the particular process employed. In the particular machine here illustrated as an example, there are ten liquid bath tanks indicated by the numerals 31 to 40, inclusive, and after emerging from the last bath tank 40, the film enters a drying chamber 41, then passes over a guide roller 43 to a takeeup reel 45 where the processed and dried film is wound up.

As above stated, these features of the machine are conventional, and may be varied within the skill of the art, Without affecting the present invention, which deals particularly with the drive of the top rollers around which the film strip extends at or near the top of each processing tank or drying chamber, the drive of these top rollers being so designed as to keep the film taut to the desired degree at all times, notwithstanding longitudinal expansion of the strip as a result of immersion in the processing baths or longitudinal contraction of the strip as a result of passage through the drying chamber or chambers.

For each processing tank and each drying chamber, there are one or more sets or groups of driven top rollers and idle bottom rollers, around which the film strip extends. Each set of top rollers and associated bottom rollers is mounted on a frame which is conveniently called a rack, the racks being so designed that they may be easily inserted in or lifted out of the tanks for repair or inspection or cleaning. Each tank or drying chamber may contain a single rack or several racks, depending upon the length of time that the film is to remain in the particular bath or chamber. For example, as shown in FIGS. l and 2, the bath tanks 31 and 34 each have two racks therein, while the other tanks and the drying chamber 41 each have a single rack. In some processes, where a longer time of travel through a particular bath is needed, it may be necessary to have three or more racks. This is easily done, since the racks according to the present invention are all identical with each other, and any desired number of racks may be placed in any particular bath tank which is large enough to receive the desired number of racks.

Referring now to FIG. 3, there is shown in transverse vertical section one of the processing tanks, for example, the tank 31, together with a rack in this tank. The rack comprises rigid members of suitable metal such as stainless steel, in the form of angle bars or other suitable structural shapes, there being upright members 51 and 53 constituting the sides of the rack, connected by a bottom crosspiece 55 and a top crosspiece 57. Near the top, a lateral arm 59 extends leftwardly from the lefthand upright member 51, and a lateral arm 61 extends rightwardly from the right-hand upright member 53. When the rack is in normal position in the tank, these arms 59 and 61 rest on main machine frame members 63 and 65,

respectively, which run longitudinally along the length of the machine just outside of the tanks.

Extending across the rack from one side bar 51 to the other side bar 53, near the bottom of the rack, is the shaft 71 on which is mounted a plurality of idle rollers or pulleys 73, each preferably on ball bearings schematically shown at 75. The idle rollers are held against axial movement along the shaft 71 by any suitable means such as spacers between the rollers, and collars 77 fastened to the shaft 71 at the outer sides of the first and last rollers.

Each roller is of conventional cross sectional shape, adapted to the particular film strip or paper strip to be processed by the machine. As illustrated in FIG. 3, the cross sectional shape preferably is somewhat dished in the center, with outwardly projecting marginal flanges to hold the film strip against axial displacement from the roller. Optionally, there may also be a series of guides 79, between adjacent rollers and at the outsides of the first and last rollers, the guides being mounted on the cross shaft 80 supported from the side bars of the rack. In many cases, these guides are not needed at all, but in some instances the operator may prefer to use such guides as an additional precaution against tangling of adjacent loops of the film strip, if the strip is so loose (when first starting the machine, before equilibrium running conditions are established) that there is danger of the loops riding over the side flanges of the pulleys.

Near the top of each rack are the top drive rollers or pulleys, mounted on the shaft 81 which is powder driven and which is mounted in suitable journals or bearings on the side bars 51 and 53 of the rack. Referring to the upper part of FIG. 3 and more especially to FIG. 4, showing some of the same parts on a larger scale, the shaft 81 is provided with bushings 83 firmly fixed to the shaft `81 to turn therewith. These bushings, conveniently made of plastic material such as polyethylene, have reduced neck portions 83a and enlarged portions 83b, as seen in FIG. 4. The reduced neck portions have longitudinal grooves so as to make a tight nonrotary connection with the roller driving disks 85 tightly forced onto the neck portoins 83a to turn therewith.

These driving disks 85 are of resilient elastic material, conveniently of neoprene. There are two such disks for each drive roller, spaced axially from each other and receiving between them an internal annular flange (or two annular flanges spaced axially from each other) within the roller driven by the pair of disks 85. The rollers are all identical, and a description of one Will serve for all. Each roller comprises a circumferentially extending body portion or rim 87 on which the film strip 13 rides, and outwardly extending marginal flanges 89 serving to retain the film against axial displacement from the roller, and an inwardly extending annular flange or flanges 91. In the case of a roller which is relatively short in an axial direction, such as a roller intended for 8millimeter film or l-millimeter film, the flange 91 may be a single flange located centrally of the axial length of the roller. In the case of rollers which are longer in an axial direction, such as rollers intended for 35-millimeter film or even wider film, it is more convenient to use two internal flanges 91 separated from each other by a hollowed out space 93, for the sake of lightness.

In any event, whether it be a single flange or two separate flanges axially spaced from each other, the flange or flanges 91 have a large central opening 95, larger than the diameter of the bushing portion `83a which passes through the roller or pulley, so that the roller is not necessarily centered on the bushing 83a and shaft 81, but may assume an eccentric position relative thereto. For a slight distance outwardly from the central opening 95, the outer side walls of the flange or flanges 91 are plane, extending perpendicular to the axis, as illustrated in 91a, and then they slope obliquely or frustoconically outwardly and away from the central plane of the roller, as seen at 91b.

The outer diameter of the fiexible driving disks 8,5 is approximately equal to the diameter of the Jiunction circle between the plane part 91a and the sloping or frustoconical part 9111 of the roller. The axial spacing between the two fiexible drive disks 85 of each roller is approximately equal to but just a trifle less than the axial spacing between the two plane surfaces 91a of the roller. Thus the plane surfaces 91a of a roller are embraced .snuglybetween the inner faces of the two resilient driving disks 85 of that particular roller. As the shaft 81 turns, turning the bushings 83 and drive disks 85 with it, the snug frctional contact between the drive disks and the surfaces 91a of the roller will rotate the roller 87 at the same speed as that of the shaft 81, so long as the roller remains concentric with the shaft and the driving disks 85 engage only with the flat or plane portions 91a of the roller. This relationship of parts is shown in the left-hand roller illustrated in FIG. 4.

Now suppose, however, that the tension of the film strip 13 is such that the roller is pulled downwardly to an eccentric position with respect to the shaft 81, this being the position of the right-hand roller in FIG. 4. This 'will cause the top edges of the resilient driving disks 85 to ride up the inclined or sloping faces 91b of the roller, and thus the lperipheries of the driving disks will embrace and frictionally drive the roller 87 at a point closer to the rim thereof, and farther from the axial center of the roller. Meanwhile, the lower edges of the driving disks will possibly still be engaged with the flat portions 91a of the roller, as seen in FIG. 4, but the frictional engagement of the upper edges of the driving disks with the roller will be greater than the frictional engagement of the lower edges of the disks, because the upper edges of the disks have been forced apart (against their natural resilient or spring action) by the inclined or frusto-conical shape of the surfaces 9111, and therefore will grip the roller more tightly. Hence the driving of the roller will occur between the upper edges of the driving disks and the inclined parts of the roller, and this will remain true as the shaft and driving disks and roller continue to turn, the roller constantly slipping downwardly into the space between the driving disks, as rotation continues, so long as the downward pull exerted by the film strip 13 remains the same. In some cases, the roller may be pulled so far down (somewhat farther than illustrated in the right-hand part of FIG. 4) that the bottom edges of the driving disks will completely leave the fiat surfaces 91a, the upper edges of the driving disks being somewhat farther up the inclined portions 91b than shown in FIG. 4. But the action is the same as just described. The greatest frictional force between the driving disks and the roller will be the force exerted by the top edges of the driving disks, since it is at this point that the driving disks are forced farthest apart by the wedge-like action of the roller. In any event, whenever the roller is moved down to an eccentric position relative to the shaft 81, be it by a large amount or a small amount, the action will be somewhat like that of a pinion driving an internal ring gear, the gear turning slower than the pinion.

Thus it is seen that the rate of driving each of the top drive rollers 87 over which the film passes, is inversely proportional to the extent to which the drive roller is eccentric with respect to the shaft 81, and the degree or extent of eccentricity, in turn, is dependent upon the downward pull exerted by the strip 13 of film or paper, as the strip comes upwardly to the roller, passes around the roller, and thence goes downwardly from the roller. In other words, the greater the tension on the strip 13, the more the roller will be pulled down to an eccentric position, and the slower it will be driven by the rotation of the shaft 81 and the driving disks 85. Thus, within limits, the rotation of the rollers cari be slowed down relative to the rotation of the shaft 81, and each roller is independent of other rollers on the same shaft (or on other 6 shafts) in this respect. At no time can a roller be driven faster than the rotation of the shaft 81, this being its maximum speed, but it can be driven slower, as the tension on the strip 13 increases.

In practice, the speed of rotation of the metering rolls which determine the incoming speed of the strip, expressed as peripheral travel per unit of time, is made somewhat less than the peripheral speed that the first set of top drive rollers would have if they were concentric with the drive shaft. Accordingly, the first group of top drive rollers 87, on the first shaft 81, will immediately tend to advance the strip faster than it is being fed into the mechanism by the metering rollers, with the result that the strip will immediately be put under longitudinal tension, which will draw the first group of rollers downwardly to an eccentric position relative to the shaft 81, sufficiently to slow down the peripheral speed of the rollers to match the incoming linear speed of the strip of film or paper. During successive passes down and up through the first liquid bath, the strip becomes wet and expands linearly or longitudinally, with the result that less tension exists in the strip as it goes over successive rollers, so that successive rollers are not pulled down to an eccentric position quite as much as the first rollers, and successive rollers (Whether on the same shaft, or on successive shafts of successive racks) are driven at slightly higher speeds, to adjust the speed of advancement of the strip to the fact that as the length of the strip expands, a somewhat greater length of strip must be fed forwardly than the length originally entering the processing apparatus. This action continues, with successive rollers on each rack driving the strip slightly faster than the preceding roller on the same rack, and with rollers on successive racks driving the strip slightly faster than the rollers of the previous rack, until the strip emerges from the last liquid bath in the tank 40, and enters the drying chamber 41. Then, during the drying operation, the length of the strip tends to contract slightly, which increases the longitudinal tension on the strip, pulling the rollers on the rack or racks in the drying chamber 41 slightly down farther to a more eccentric position, thus slowing down the rotation of the rollers and slowing the advancement of the strip as it contracts in length during the drying operation. Thus the adjustment of the driving speed is automatic, depending upon the tension on the strip of film or paper, and the speed accommodates itself to the increasing and decreasing length of the strip during wetting and drying thereof. The result is a smooth drive, without excessive looseness which causes snarling of the strip in some of the prior art processing apparatus, and without building up excessive tension in the strip which causes breakage of the strip in some of the prior apparatus.

It will be noted from FIG. 3 that there is one more drive roller on the top drive shaft 81 than the number of idle rollers 73 on the bottom idle shaft 71. This is always the case, as one cari see by following the travel of the strip in FIG. 3. When a strip enters at the first top roller of any given rack, it extends downwardly to the first bottom idle roller, then up to the second driven roller, then down to the second idle roller, then up to the third driven roller, and so on. Since the strip leaves the rack at the final top roller, it is seen that there must always be one more top roller than bottom roller.

In the particular rack illustrated in FIG. 3, there are seven top rollers and six bottom rollers. There could be more or less. In a -rack of convenient size for easy handling, the indicated number of seven top rollers and six bottom rollers is convenient when the rollers are of a size for 35-millimeter film. If each roller is narrower (that is, shorter in an axial direction) as for example for use with l-millimeter film or S-millimeter film, then there would be more rollers on a rack of the same size.

Referring now to FIG. 1, it is seen that, in a typical machine, the strip of film or paper enters the first rack in the first bath tank 31 at the right-hand side, progresses across to the last top roller at the left-hand side of the machine, thence goes to the iirst left-hand roller at the top of the second rack in the same bath tank 31, and progresses across, up and down, to the last roller at the right-hand side of the second rack, then goes to the rst roller at the right-hand side of the third rack (in the second bath tank 32) and progresses across to the lefthand roller of this rack, and so on, in the same fashion.

The drive shafts 81 of the various racks may be driven in any convenient manner. It is advantageous, however, to drive them in such a way that the racks can be lifted out of the tanks or replaced in the tanks, without disconnecting or connecting drive mechanism. This is preferably accomplished, according to the invention, by extending the drive shaft 81 laterally to one side of the machine, as shown at the right-hand side of FIG. 3, where it is provided with a sprocket 101 which may be fixed rigidly to the shaft 81 if desired, but which preferably is connected to the shaft through a slip clutch 103 so that the shaft need not turn even though the sprocket continues to turn, if there is any unusual resistance to turning. Just beneath the sprocket 101 is a trough 105 extending longitudinally and welded or otherwise secured to a depending ange of the frame member 65, this trough extending all the way along the machine past all of the racks. A sprocket chain 107, driven by a suitable motor, lies in the trough 105 and moves along the trough in meshing engagement with the lower edge of the sprocket 101, the chain 107 preferably resting on an antifriction pad 109. The return reach of the chain, shown at 111, rests in a second trough 113 below the trough 105.

With this arrangement, the mere act of lifting a rack out of the tank serves to lift the sprocket 101 from engagement with the chain 107, so that it is not necessary to disconnect any parts. Similarly, the mere act of inserting a rack downwardly into a processing tank or drying chamber serves, without more, to engage the sprocket 101 with the drive chain 107.

The drive arrangement illustrated and described in connection with FIG. 3, where the shaft 81 is extended laterally past the top edge of the tank and past the adjacent side frame member 65, is satisfactory where it is permissible to have the top drive rollers at an elevation above the top of the liquid in the tank. In many types of processing this is permissible, as there is no objection to having the strip of lm or paper come up out of the liquid at each upward pass, and stay out of the liquid for a few seconds While it goes around the roller and then down into the liquid again. But in some types of photographic processing, it is desirable to keep the lm under the liquid at all times in any given tank, although obviously it must come up out of the liquid when it moves from one tank to the next tank. Where the lm is to be kept below the liquid level during its passage through one tank, then the drive shown in FIG. 3 cannot be used. Instead, the alternate drive shown in FIG. may be employed. Here, the shaft 81 does not extend beyond the edge of the tank, but stops at its bearing 121 on the side frame member 53. A bevel gear 123 pinned to the shaft 81 meshes with a bevel gear 125 pinned to the lower end of a short vertical shaft 127 rotatable in bearings 129 on the upper part of the side frame member 53. The shaft 127 extends upwardly to an elevation above the top of the processing tank, and its upper end is provided with a bevel gear 131 pinned to the shaft and meshing with another bevel gear 133 on a shaft 135 extending horizontally outwardly in bearings on a lateral extension 137 on the rack frame. This shaft 135 carries a sprocket 141 corresponding to the sprocket 101 in the embodiment earlier described, the lower edge of the sprocket engaging the upper reach 107a of the drive chain, the lower reach of which is shown at 111a, corresponding to the upper and lower reaches 107 and 111 of the drive chain previously described, and correspondingly riding in troughs or channels g and 113zz xed to the frame member 65.

With this arrangement, the drive train goes over the edge of the liquid tank and allows the shaft 81 to be within the tank submerged below the liquid level thereof. All of the passes of the strip 13 around the top and bottom rollers of any one rack may remain below the liquid level at all times, and if there is more than one rack in the same tank, the passage of the strip from the last top roller of one rack to the rst top roller of the next rack can also be below the liquid level. However, when the strip is to pass from one tank to the next tank, it is brought up from the last drive roller of the rack to an idle roller 151 rotatable (like the bottom idle rollers) on the fixed shaft 153 mounted on the rack frame at an elevation approximately equal to the top edge of the liquid tank and above the level of the liquid therein. The strip 13 passes over this idle roller 151 to a similar idle roller on the lirst rack in the next tank, and then down into the next tank.

It has already been mentioned in connection with FIG. 3 that guides 79 on a shaft 80 may be used in connection with the bottom idle rollers as an extra precaution if desired. Such guides may also be used, if desired, in connection with some or all of the top drive rollers, and such guides are shown in FIG. 5 at 157, being mounted on a stationary shaft 159, and still other strip guides 161 mounted on a shaft 163 may be used if desired. However, the use of these guides is optional, and in most cases the guides are not needed and will not be used.

The roller drive arrangement, whereby the speed of rotation of the roller varies in accordance with the tension of the strip passing over the roller, has been described in connection with a photographic processing machine because the drive was designed especially for photographic processing machines and finds its greatest usefulness in connection with such machines. However, its usefulness is not confined to photographic processing machines, since the drive is useful wherever the advancement of a strip, web, or strand of any material is to be varied in accordance with the longitudinal tension on the strip, web, or strand, either because of longitudinal expansion or contraction of the strip, web, or strand, or for any other reason. For example, the drive is useful in coating machines where the material being coated may have a tendency to expand longitudinally when a wet coating is applied, and then to contract longitudinally as the coating dries; also in textile machines where webs or individual strands of textile material are subjected to treatment which may cause longitudinal expansion or contraction.

It is to be understood that the disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

1. A photographic processing machine comprising a tank for containing a processing liquid, a lower shaft extending approximately horizontally in said tank near the bottom thereof, at least one bottom roller mounted on said lower shaft, an upper shaft extending approximately horizontally in said tank near the top thereof, a plurality of top rollers mounted on said upper shaft and so placed that a strip of photographic material to be processed may run over a first top roller, thence downwardly to and around a bottom roller, thence upwardly to and around a second top roller on the same shaft as the lirst top roller, each of said top rollers having a central axial opening therethrough sufficiently larger than the shaft on which it is mounted so that each top roller may move radially from a position concentric with the shaft on which it is mounted to a position eccentric with respect thereto, mechanism for rotating said upper shaft,

and resilient drive means operatively connecting each top roller to said upper shaft to tend to turn such top roller with said upper shaft, said resilient drive means tending to maintain each top roller in a position concentric with said upper shaft, increasing tension on said strip of photographic material running on a top roller sewing to displace such roller to an eccentric position reative to said upper shaft, said drive means driving each top roller from the upper shaft on which it is mounted, at the same speed as the rotation of said upper shaft so long as the top roller is concentric with its shaft and at a slower speed varying inversely to the degree of eccentricity of the top roller when said top roller is displaced to an eccentric position relative to its shaft.

2. A construction as defined in claim 1, wherein said resilient drive means comprises an annular wall portion on each top roller, inclined relative to a plane perpendicular to the axis of the roller and substantially concentric with the periphery of the roller, and a drive member secured to said upper shaft to turn therewith, said drive member resiliently engaging said inclined Wall portion with axial pressure thereon to tend to hold said roller in concentric position With respect to said upper shaft, said annular wall portion and said drive member being so positioned relative to each other that displacement of said roller to an eccentric position with respect to said upper shaft will displace an edge of said dri-ve member in an axial direction and cause said edge to bear against said wall portion at a point farther from the center of said roller than when said roller is concentric with said upper shaft, so as to drive said top roller at a slower rate than the rate of rotation of said upper shaft.

3. A construction as defined in claim 2, wherein said drive member is a resilient annular disk concentric with said upper shaft.

4. A construction as dened in claim 3, wherein said resilient annular disk consists essentially of a plastic elastomer.

5. A construction as dened in claim 1, wherein said resilient drive means for each of said top rollers cornprises a pair of resilient annular disks mounted on said upper shaft to turn therewith and axially spaced from each other, each top roller having an inwardly extending annular portion with sloping sides wedgingly engaged between the annular disks of said pair and forcing companion edges thereof apart when increasing tension on said strip of photographic material causes a top roller to be displaced to an increasingly eccentric extent relative to said upper shaft.

6. Strip driving mechanism for advancing a strip of flexible material, said mechanism comprising:

(a) a shaft rotatable at a constant speed,

(b) a series of rollers mounted on said shaft,

(c) guide means for guiding a long strip of flexible material in a path of tra-vel having successive spans extending to and around and from successive rollers of said series while maintaining said strip under longitudinal tension, and

(d) means responsive to the longitudinal tension in the spans of material extending to and around and from each individual roller for driving that roller from the shaft on which it is mounted at a variable speed decreasing as the longitudinal tension on said spans increases,

(e) said roller driving means comprising an internal annular flange on a roller, portions of opposite side surfaces of said ange being inclined toward each other when viewed in diametrical axial cross section, and a pair of resilient annular disks mounted on said shaft to rotate therewith and axially spaced from each other in position to embrace said internal flange between them and to make driving contact with said inclined surfaces of said flange when said roller is moved to an eccentric position relative to said shaft. 7. The combination with a shaft, of a roller loosely surrounding said shaft, said roller having a central axial opening through which said shaft extends and suiiiciently larger than said shaft so that said roller may have a substantial range of radial movement with respect to said shaft, said roller also having two annular lateral surfaces, portions of which are inclined in radial cross section in a direction such that the axial spacing between said portions of said surfaces changes progressively in a radial direction, and a pair of drive disks axially spaced from each other and mounted on said shaft to turn therewith, said disks having peripheral portions engaging said lateral surfaces of said roller in driving relation thereto and being adapted to be displaced in an axial direction by said inclined portions when said roller is moved radially with respect to said shaft, said disks being so proportioned and arranged relative to said roller that when said roller is concentric relative to said shaft, said disks will tend to drive said roller at the same speed as said shaft, and when said roller is shifted to an eccentric position relative to said shaft, said disks will tend to drive said roller at a slower speed than said shaft.

8. A construction as defined in claim 7, wherein said drive disks are of flexible resilient material, and wherein said annular lateral surfaces of said roller extend into the space between and are embraced by said disks, movement of said roller from a concentric position to an eccentric position tending to wedge portions of said drive disks farther apart from each other.

References Cited UNITED STATES PATENTS 1,177,697 4/1916 Gaumont 95-94 1,846,075 2/1932 Aller et al. 95-94 2,120,735 6/ 1938 Debrie 226-191 2,895,375 7/ 1959 Wittel 226-194 XR 3,043,206 7/ 1962 Fulton 95-94 3,369,765 2/1968 Jensen 226-191 XR 3,380,678 4/1968 Feasey et al 226-191 XR NORTON ANSHER, Primary Examiner R. P. GREINER, Assistant Examiner U.S. Cl. X.R.

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