US2488141A - Film processor having means for retaining a film loop at constant length in a u-shaped conduit - Google Patents

Description

Nov, 15, 1949 v. E. PRATT ET AL 2,488,141

FILM PROCESSOR HAVING MEANS FOR RETAINING A FILM LOOP AT CONSTANT LENGTH IN A U-SHAPED CONDUIT 4 Sheets-Sheet 1 Filed March 7, 1945 INVENTOR. VERA/EUR E. PRATT GEORGE E GRAY N 1949 n v. E. PRATT ETAL.

FILM'PROCESSOR HAVING MEANS FOR RETAINING A FILM LOOP AT CONSTANT LENGTH IN A U'SHAPED CONDUIT Filed March 7, 1945 1 Sheets-Sheet 2 NQW m W vw W i w A INVENTOR.

Nov. 15, 1949 v #RATT ETAL 2,488,141

FILM PROCESSOR HAVING MEANS FOR RETAINING A FILM LOOP AT CONSTANT LENGTH IN A U-SHAPED CONDUIT 4 Sheets-Sheet 3 Filed March 7. 1945 INVENTOR. VERNEUR E. PR47'7' GEORGE E GRAY Nov. 15, 1949 v. E. PRATT EI'AL 2,488,141

FILM PROCESSOR HAVING MEANS FOR RETAINING A FILM LOOP AT CONSTANT LENGTH IN A U-SHAPED CONDUIT n INVENTOR. VERNEUR 5. PRATT N Q q 3 BY GEORGE E GRAY a ,2 I? E I 'fjmam w &

Patented Nov. 15, 1949 FILM PROCESSOR HAVING MEANS FOR RE- TAINING A FILM LOOP '1" OFFICE AT CONSTANT LENGTH IN A U-SHAPED CONDUIT Verneur E. Pratt and George F. Gray, Norwalk, Conn.

Application March 7, 1945, Serial No. 581,355

Claims. 1

This invention relates to improvements in film processors wherein the film to be processed is moved through a series of U-shaped conduits, each of which may contain a fluid employed in processing the film, the film being fed into one leg of each U by a cooperative driving and driven roller, and being removed from the other leg of the U by a second cooperative driving and driven roller; and is directed more particularly to maintaining a uniform loop of film within the U- shaped conduit and between the two pairs of cooperative rollers which deliver it to and remove it from the conduit.

This invention is a continuation in part of copending application Serial Number 573,438, filed January 18, 1945, now Patent No. 2,424,052, dated July 15, 1947.

In said co-pending application the cooperating driving and driven rollers are comprised of a driving roller, the diameter of which is substantially equal to the distance between two planes extending from the axes of the two legs of the U -shaped conduit, and the driven rollers are adjusted with respect to said driving roller a distance greater than the thickness of the film and less than the l thickness of a thick leader which is attached to the film for propelling it through the array of rollers and U-shaped conduits, thereby pulling the film through without permitting its emulsion surface to become scratched.

According to the present invention, in line with a plane extending from each leg of the U-shaped conduits is a cooperative pair constituting a drive and a driven roller. Thus, each U-shaped conduit employs a pair of driving and driven rollers in line with each of its straight legs. The driving rollers are of exactly the same diameter and are driven by a common driving means. The cooperative driven rollers are carried on individual pivoted supports and these supports are joined together by spring means urging them into contact with their cooperative driving rollers. By employing a unit spring means having one end attached to one pivoted support and its other end attached to its other pivoted support, the force alignment with each leg a pair of cooperative riving and driven rollers;

Figure 2 is a plan view showing the mechanism for driving the driving rollers and the relation of the driven rollers thereto;

Figure 3 is an elevation partly in section taken along the line 33 of Figure 2;

Figure 4 is a sectional elevation as seen along line ll of Figure 1;

Figure 5 is a sectional View of the U-shaped conduit as seen along the line 55 of Figure 4; I

Figure 6 is a perspective view of one of the free roller pivotal supports; and

Figure 7 is a diagrammatic sketch showing a complete processing system employing driving means according to the present invention. 7

Referring first to Figure 1, a supporting wall 2% carries a reel shaft 2! adapted to support a reel 22 containing exposed film. The film, designated by the numeral 2l5, passes over a free roller 24 and is fed between rollers to be presently described.

Behind the wall Zil, as may beseen in Figure 2, is a pair of spaced parallel supporting members 25 and 26. A cradle 21, the details, of construction of which will be described in connection with Figure 6, is pivotally carried between the supports 25 and 2E. Journalled in the cradle 21 is a shaft 28 which has keyed thereto a gear 29 which meshes with a gear at, which will be presently described. A cross pin 3| in the shaft 28 is engaged by a slot formed in the hub 32 of a roller 33. The roller 33 is secured to the shaft 28 by meansvof an end screw 35. A shaft 35 is journalled in suitable bearings in the supports 25 and 26, and has keyed thereto the gear 3B which was described above as meshing with the gear 29. The shaft 35 also has keyed thereto a worm gear 35. This shaft also carries suitable collars to eliminate any end play. A cross pin 3? in the shaft 35 is engaged by a slot formed in the hub 38 of a roller 39. The roller 39 is secured to the shaft by an end screw 40.

Spaced apart from the shaft 35 is a like shaft 4| which is also journalled in suitable bearings in the supports 25 and 25. The shaft 4! has keyed thereto a spur gear i2 identical with the spur gear 30. A worm gear 43 is also keyed to the shaft 4 land is in alignment with the worm gear 36, and common to those two worm gears is a worm shaft M which is driven by a suitable gear reduction. A cross pin 2-5 in the shaft 41 is engaged by a slot in the hub 26 of a roller 4?, and this roller is held onto the shaft by means of an end screw 48.

A cradle 59 is pivotally mounted between the supports 25 and 2t and a shaft journalled in the cradle carries a gear 5| which meshes with the gear 42. A cross pin 52 in the shaft 50 is engaged by a slot in the hub 53 of a roller 54 secured on the shaft by means of an end screw 55. The cradle has an upwardly projecting lug 56. Likewise the cradle 49 has an upwardly pro- J'ecting lug 51. Between the shafts 35 and 4| is mounted a distance rod 58 which is secured to the support plate 25 by means of a screw 59 and secured to the support plate 26 by means of a screw 69. A helical spring 6| has one end connected to the lug 56 and its other end connected to the lug 51. Since the spring 6| freely spans the space between the lugs 56 and 51, its urge upon the cradles is exactly the same, with the result that the cradle 21 is urged to the right, as seen in Figure 2, and the cradle 49 is urged to the left with equal force, and the tensional engagement of the roller 33 with the drive roller 39 is exactly the same as the tensional engagement of the roller 54 with the drive roller 41. It will be remembered that the shafts 35 and 4| are driven, respectively, through the worm gears 36 and 43 actuated by the worm shaft 44, so that the direction of rotation of the driving rollers, as may be seen in Figure 1 indicated by the arrows, is counter-clockwise.

Since the spur gears 29, 38 and 5|, 42 are in definite ratio to the diameters of the rollers 33, 39 and 54, 41, respectively, the regulation effected by the spring 6| falls within the backlash of the meshed gears. A cradle 62, identical with the cradle 21, is pivotally carried between the supports 25 and 26, and journalled in the cradle 62 is a shaft 63 which has keyed thereto a gear 64 which meshes with a gear 65. A cross pin 69 in the shaft 63 is engaged by a slot formed in the hub 61 of a roller 68 which is in turn secured to the shaft by an end screw 69. A shaft is journalled in suitable bearings in the supports 25 and 26, and has keyed thereto the gear 65 which meshes with the gear 64. A worm gear H is keyed to the shaft 19 and meshes with the worm 44. The shaft 19 also carries suitable collars to eliminate end play, and a cross pin 12 therein is engaged by a slot formed in the hub 13 of a roller 14. A screw in the end of the shaft 10 retains the roller 14 on the shaft.

Spaced apart from the shaft 19 is a like shaft 16 journalled in suitable bearings in the supports 25 and 26. This shaft has keyed thereto a spur gear 11 identical with the gear 65, and a Worm gear 18 identical with the Worm gear 1! and also meshing with the worm 44. The shaft 16 also carries suitable collars to eliminate end play and is provided with a cross pin 19 which engages a slot formed in the hub 80 of a roller BI secured to the shaft by means of an end Screw 82.

A cradle 83 like the cradle 49 is pivotally mounted between the supports 25 and 26, and a shaft 84 journalled in the cradle has keyed thereto a gear 85 which meshes with the gear 11. The shaft 84 has a cross pin 86 mounted therein and engaged by a slot formed in the hub 81 of a roller 88 which is retained on the shaft by means of an end screw 89. The cradle 62 has an upstanding lug 90 formed thereon and. the cradle 83 has an upstanding lug 9| formed thereon. A helical spring 92 is secured to the lugs 90 and 9| and freely spans the space therebetween.

Spaced shafts 93 and 94 are journalled in the supports 25, 26, and have keyed thereto, respectively, spur gears 95, 96 and worm gears 91, 98. These shafts also have cross pins 99, I99, respectively, engaged by slots formed in the hubs IN,

'4 of a roller I02; and I03 of a roller I04, said roller being retained on said shafts by means of end screws I05, I06. Both of these shafts are provided with collars to eliminate end play, and both the worm gears 91, 98 mesh with the worm 44.

A cradle I01 is pivotally carried in the supports 25 and 26 between the shaft 93 and the cradle 83, and a second cradle I 98 is pivotally mounted in the supports to the right of the shaft 94. The cradle I91 carries a shaft I99 to which a gear H0 is keyed. The shaft I99 also carries a cross pin I I I which is engaged by a slot formed in the hub II2 of a roller II 3 retained on the shaft by means of an end screw H4. The gear I I0 meshes with the gear 95.

The cradle I08 carries a shaft II5 to which a gear II6, meshing with the gear 96, is keyed. A cross pin H1 in the shaft II5 engages a slot formed in the hub I I8 of a roller I I9 retained on the shaft by means of an end screw I20. The cradle I01 has an upstanding lug I2I formed thereon and the cradle I08 has a like lug I22. A spring I23 has its ends secured to the lugs I2I and I22 and freely spans the space therebetween.

Several distance rods, like the distance rod 58 above described, are employed for properly spacing the supports 25 and 26.

The worm 44 projects from each side of a gear reduction unit I24, and a shaft I25 extending therefrom at a right angle to the worm 44 carries a shive I26 which may be belted to a pulley on a prime mover for furnishing power thereto.

The shaft 10 may extend rearwardly from the support 26 and may have keyed thereto a sprocket I 21 which may be connected to a take-up reel in a dryer for the processed film but, since the dryer forms no part of the present invention, it need not be described herein,

Referring now to Figure 6, the cradle, generally designated by the numeral 21, includes a side portion I28, and spaced apart therefrom, a second side portion I29 joined together by a lower web I30 and an upper web I31. The side portion I28 carries a bearing boss I32 and the portion I29 carries a like bearing boss I33 in alignment therewith and in which the shaft 28 is journalled. The shaft 26 has keyed thereto the gear 29 and also carries a collar or spacer sleeve I39 and a washer I40 to eliminate end play. The portion I28 carries a boss I34 on the lower end thereof, and this boss is tapped to accommodate the threads of a shouldered Screw I 35, means (not shown) being provided for locking the screw in the boss I34 after assembly. The portion I29, on its lower end, also carries a boss I36 which is tapped to accommodate the threads of a shouldered screw I31. When assembled, the straight shanks of the shouldered screws I35 and I31 are journalled in the supports 25 and 26. The lug 56 extends upwardly from the web I3I and is provided with a hole I38 to be engaged by the end of the spring 6 I.

Since the cradles 49, 62, 83, I01, I98 are identical with the cradle 21, they need not be described in detail.

The supports 25 and 26 are secured to the supporting Wall 20 in any suitable manner, for example, by means of screws I4I extending through the wall 20 and threadedly engaging the supporting member 25 with a spacer washer I42 therebetween.

Returning to Figure 1, a U-shaped conduit I56, the cross section of which may be seen in Figure 5, consists of parallel sides I69 and I6I joined by angular portions I92 and IE3 on one side forming an apex I64. Similar sides I65 and IE6 join the sides I60 and NH and meet at an apex I61. The film 2I5 normally clears the conduit I59 and the like points of contact with the conduit are on the extreme edges.

One leg of the conduit I59 has flares I68 and I69 formed thereon. These flares are oppositely disposed, I68 being adjacent to the roller 33 and I69 being adjacent to the roller 39. The other leg of the conduit is similarly flared at I10 and HI.

One leg of the conduit has aligned holes I12 and I13 formed therein and in alignment with these holes in the other leg are formed aligned holes I14 and I15. A hollow casing I16 extends laterally from the wall 20 and has an upstanding flange I11 which is secured to said wall by means of screws I18. The hollow casing I16 has clearance passages formed therein :to accommodate the legs of the conduit I59, and these legs and the casing are soldered or brazed together to form a fluid tight joint.

The purpose of the casing I19 is to receive the processing fluid (which is forced through the conduit by means of a pump to be presently described) as the fluid is ejected through the openings I12, I13, I14 and I into the exterior of casing I16.

The casing I16 has a hole I85 formed in the bottom wall thereof and this hole is fitted with a bushing I86 to which is attached a short pipe I81, which extends into the open end of a tank I88 secured to the Wall 20. Thus, fluid passing from the openings I12 to I15, inclusive, and into the casing I16 flows out through the hole I85 and via the pipe I81, and is delivered to the tank I88. At the bottom the U-shaped conduit I59 has aligned holes I89 and I90 formed therein. A hollow casing I! has a flange I92 which is secured to the wall 29 by means of screws I93. The conduit is positioned in the hollow casing I9I as shown and is soldered or brazed thereto to form a fluid tight joint.

A nipple I95 has one end in communication with the casing I9I and extends through the wall and is in fluid tight engagement with a fitting I43 formed of rubber or the like. A pipe I44 has one end connected to the fitting I43 and the other end is connected to the outlet I96 of a pump I91. The fitting I43 may be supported on the rear of the wall 29 by means of a bracket I45 secured thereto and carrying clamping means I46 embracing the fitting I43. The pipe I98 has its lower end in communication with the interior of the tank I88 and its upper end is connected to the inlet I99 of the pump I91. The pump is directly connected to an electric motor 209. When the motor is turned on, fluid is drawn from the tank I88 via the pipe I98 to the inlet of the pump and thence, via the outlet I96, via the pipe I44, the fitting I43 and the nipple I95, fluid is delivered to the hollow casing I9I. The fluid then passes via the aligned holes I89 and I99 into the U-shaped conduit I59 where it divides, and part of it passes up the left leg, as seen in Figure 1, then outwardly from the conduit via the holes I12 and I13 into the hollow casing I16. Part of re fluid also passes up the right leg and out via the holes I14 and I15 into the hollow casing I16. The fluid flows from the casing via the pipe I81 and returns to the tank I88.

The fluid entering the conduits via the holes I89 and I90 has substantial velocity, and therefore, it washes ofi any deposits on the surface of the film due to the processing fluid. This is'particularly important in cases where fixer-developers are used in our apparatus. The action of the fixer-developer results in a deposit on the surface of the emulsion, which deposit shields the emulsion from free action by the solution. However, the velocity of the fluid up both legs of the conduit washes oil" the coating or deposit, thereby leaving the surface of the emulsion open to the continued action of the fixer-developer.

The hollow casing I9I is provided with a suitable drain cock 29I by means of which the entire system may be drained into a container or trough 292 in the bottom of the'machine.

A second U-shaped conduit I59 is identical with the conduit I59 and has associated therewith a hollow casing I19 and a discharge pipe I81 discharging into a tank I88.

At the bottom of the U is a hollow casing I9I like the hollow casing I9I. A pump I91 similar to the pump I9! is provided for drawing liquid from the tank I88 and delivering it to the hollow casing I9I A third U-shaped conduit I59, is identical with the conduit I59 and has associated therewith a hollow casing -I1Ii and a discharge pipe I81 discharging into a tank I88 At the bottom of the U is a hollow casing I9I like the hollowing casing I9I. A pipe 203 has one end connected to the hollow casing I9I (see also Figure '7) and the other end of this pipeis connected to a solenoid valve 204 which is in turn connected through a mixing valve 205 for mixing hot and cold water together to deliver water at a predetermined temperature. A pipe 206 leads from the mixing valve to a'source of cold water under pressure and a pipe 201 is connected to the mixing valve 205 and leads to a source of hot water under pressure.

The mixing valve 205 is provided with a thermostatic control 298 which automatically controls the temperature of the water delivered by the pipe 203.

The valve 204 includes a solenoid 209 which is connected via a pair of wires 2 I 0 and a switch 2I I to a source of current 2I2.

The switch ZII, when turned on, supplies energy to both the motor 200 and the motor 200* and to the solenoid 209 on the valve 204. Thus, when the machine is turned on, the pump I91 driven by the motor 200 circulates fluid in'the U-shaped conduit I59, the pump I91, driven by the motor 200*, circulates fluid in the U-shaped conduit I59 and the solenoid valve 204 is opened and delivers warm water to the U-shaped conduit I59".

It has been described above that the processing fluid circulated through the U-shaped conduits I59 and I 59 returns to the pumps and is recirculated. However, the washing water which is delivered via the pipe 203 to the U-shaped conduit I59 overflows into the hollow casing I16", passes down the pipe I81 into the tank I88 and thence passes to the sewer or drain via a pipe 2I3, the upper end of which is connected to the bottom of the tank I88 From the above description it will be clearly understood that the reel 22' of exposed film 2I5 may be positioned on the stud 2I, and the end of the film may be passed over the roller 24 and inserted between the drive roller 39 and its companion roller 33. Since the roller 33 is urged toward the roller 39 by means of the spring BI, the film starts feeding down the left leg of the conduit I59 and as the'rollers continue o feed the film, it passes around the curved lower end of the conduit I59 and upwardly in the right leg of the conduit. As the film is leaving the upper end of the right leg, it enters between rollers 41 and 54 which also tensionally engage the film under the urge of the spring 6|. Since the spring 6| has a free span, the urge of the roller 3 against the film is exactly equal to the urge of the roller 33 against the film. Therefore, the pair of rollers 41, 54 will remove film from the U-shaped conduit I59 at exactly the same rate the film is delivered thereto by the pair of rollers 33, 39.

An arcuate channel I41 spans the space between the line of contact of the rollers 47, 54 and the line of contact between rollers 68, 14. As the end of the film 2I5 is moved upwardly by the rollers 31, 54, the arcuate channel I l! guides the end of the film and ensures its delivery between the rollers 68, M. The latter rollers feed the film downwardly into the conduit I59 and then the film passes around the bottom and up the right leg to be engaged by the rollers I04, I I9, and from these rollers the film may pass to a dryer which forms no part of the present invention.

Referring again to Figure 7, applicants provide a drain pan or trough 202 in the bottom of the machine. This drain pan or trough is provided for catching any fluids which spill or which are dumped from the system. Applicants also provide a dirigible nozzle 2l6 which is connected by means of a flexible hose 2|! to the pipe 203. The nozzle may have a plunger valve 2l8 with a handle 2H3 so that the operator may turn the spray nozzle off or on at will for washing down the interior of the machine or flushing out and draining the several tanks and conduits in the machine.

Another important use of the nozzle 216 is in connection with mixing the processing solutions. For example, the powdered, pulverized and/or liquid chemicals may be placed in the bottom of the proper tank I88, then the operator may, by means of the nozzle 2l6, fill the tank until the liquid level reaches the line indicated by the numeral 2 l9, and thereby add the proper amount of water for the charge of chemicals. The charge of chemicals may be proportioned so that one charge will completely process a roll of film, following which the operator may, by means of the drain cock 2B1, empty the tank of solution. This is preferably done with the pumps operating so that when the system is drained additional water may be added to the tanks, and this will be pumped through the pump and out by the drain cocks and thereby flush each section of the machine.

The drain pan has a sump 220 formed therein preferably adjacent to one end thereof. A pump 22! has its inlet connected to one end of a pipe 222, the other end of which extends into the sump. The outlet of the pump is connected to a pipe 223 which leads to the sewer. The pump 22l is directly connected to a motor 224, and this motor is connected via switch 225 to the source 2l2, so that any time it is desired to remove fluid from the drain pan 202, it is only necessary to turn the switch 225 and set the pump 22l into operation.

The pulley l 26 on the gear reduction 124 is connected via a belt 225 to a pulley 221 which is secured to the shaft of a driving motor 228. The driving motor 228 is connected via a pair of wires 229 to the wires 2H3 so that the switch 2 may,

8 in addition to controlling the solenoid 209 and the motors driving the pumps I91, l 91, also eifect the driving of the series of driving rollers driven by the worm shaft 44.

All of the rollers, both the drive rollers and the free rollers (as was the case in the above mentioned application of which the present application is a continuation in part) have rims formed of rubber or the like. Therefore, the film passing between cooperating drive and free rollers is positively driven, due to the frictional engagement by said rubber-like rims, and the chance of the film becoming scratched is minimized.

Although but one specific embodiment of this invention has 'been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention, as defined by the following claims.

What is claimed is:

1. In a device for processing film, a U-shaped conduit for containing processing fluid, said conduit having vertical legs with open ends, means supporting said conduit, a frame, a pair of cradles pivotally supported on said frame in spaced relation to each other and in definite relation to said open ends, a shaft journalled in each of said cradles and a free roller mounted on each of said shafts, a pair of drive rollers journalled in said frame between said cradles, both said free and said drive rollers having rubber-like rims, said drive rollers being adapted to be engaged by said free rollers on lines of contact above and in line with said open ends, a spring secured to and forming a free span between said cradles, said spring being adapted to exert equal urges of said free rollers against the cooperating drive rollers; a free loop of film extending between one pair of cooperating rollers, through said conduit and between the other pair of cooperating rollers; and means for driving said drive rollers at an identical rate of speed, whereby the length of said loop remains substantially constant.

2. In a device for processing film, a support, a plurality of U-shaped conduits carried on said support for containing fluids, said conduits having open ended vertical legs, a set of rollers for each conduit comprised of a pair of adjacent rollers of equal diameters driven at the same rate of speed, said rollers being positioned between a second pair of free rollers which are movable toward the driven rollers and adapted to urge the film into contact with said drive rollers along lines lying on planes extending through said legs, pivoted cradles supporting shafts carrying said free rollers, at least the cooperative faces of all said rollers being formed of rubber-like material, and a spring secured to and forming a free span between said cradles for causing said free rollers to urge the film as aforesaid, whereby film passing between one of said rollers and its cooperating free roller is fed into said conduit at exactly the same rate as film passing between the other of said drive rollers and its cooperating free roller is removed from said conduit, said film forming a free loop between said rollers and lying within said conduit.

3. In a device for processing film, a support, a U-shaped conduit on said support for containing processing fluid, said conduit having vertical legs with open ends, an array of rollers above said conduit comprised of a pair of adjacent rollers of equal diameters, said rollers being carried on shafts positioned between a second pair of mov-.

ably supported rollers which contact said first rollers along lines substantially in line with the open tops of said conduit, at least the peripheral faces of all said rollers being of rubber-like material, means for driving said first rollers at the same speed, spaced pivoted cradles supporting shafts carrying said second rollers, and a single spring secured to and freely spanning the space between said cradles, whereby a film inserted between one of said first rollers and its cooperating free roller is fed into one leg of said conduit at exactly the same rate said film, after passing down said leg and up the other leg, is removed from said conduit by the other of said first rollers and its cooperating free roller, said film forming a free loop between said rollers and lying within said conduit.

4. In a device for processing film, a support, a plurality of U-shaped conduits carried on said support for containing fluids, an array of rollers above the open ends of the legs of said conduits and comprised of a free roller and a drive roller for each leg of each conduit, two drive and two free rollers forming a set, said drive rollers of each set being positioned between said free rollers of each set and each of the latter being movabl positioned with respect to and adapted to cooperate with its corresponding drive roller, and spring means common to and urging both the free rollers of each set into contact with the drive rollers of the same set, whereby film passing through said array and looped through each of said conduits in the form of a free loop is delivered to one leg of each U and removed from the other leg thereof at the same rate.

5. In film processing apparatus, a frame forming a support, a cradle having a shaft journalled therein, means pivotally carrying said cradle on said support, a second cradle having a shaft journalled therein, means pivotally carrying said second cradle on said support in spaced relation to said first cradle, rollers secured to said shafts and termed free rollers, a pair of driven shafts journalled on said frame between said cradles in spaced relation to each other, said last shafts 10 being driven in unison, other rollers secured to said driven shafts and termed driven rollers, the peripheral faces of all said rollers being smooth and toothless and formed of rubber-like material, and a spring having one end secured to one of said cradles and having its other end secured to the other of said cradles for urging said free rollers toward said driven rollers, whereby a free loop of film formed between the two pairs of cooperating free and driven rollers is maintained constant by the delivery of film thereto solely by one of said pairs and by the equal removal of film therefrom solely by the other of said pairs. VERNEUR E. PRATT. GEORGE F. GRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 757,323 Lienekampf Apr. 12, 1904 1,570,809 Wescott Jan. 26, 1926 1,637,658 Rose Aug. 2, 1927 1,656,522 Josepho Jan. 17, 1928 1,809,830 Cobb June 16, 1931 1,831,562 I-Ieisler Nov. 10, 1931 1,847,663 Newman Mar. 1, 1932 1,890,490 Barkelew Dec. 13, 1932 1,991,249 Ingman et al Feb. 12, 1935 2,020,419 Knowlton Nov. 12, 1935 2,043,853 Howell June 9, 1936 2,048,182 De Ybarrondo July 21, 1936 2,085,188 Gerlach Jan. 29, 1937 2,186,927 Hughey Jan. 9, 1940 2,337,864 Beidler Dec. 28, 1943 2,373,107 Duffy Apr. 10, 1945 2,401,185 Pratt May 28, 1946 FOREIGN PATENTS Number Country Date 529,933 Germany July 23, 1931 594,938 Germany Mar. 24, 1934 844,158 France Apr. 11, 1939

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