Paper-processing control apparatus

A web-handling system for use in the processing of photographic print paper during the developing process includes a plurality of rollers mounted in a developing tank, at least some of the rollers being movable to vary the length of the paper path through the tank. The paper path length is continuously monitored and the input and output speed of drive rollers that move the paper into and out of the tank is controlled so that the path length is of the proper value to maintain the paper within the tank for a predetermiend time regardless of the rate of input of paper to the tank. The movable rollers are mounted on a carriage that is supported by the paper web when the handling system is in dynamic operation. A monitoring sensor is positioned near the input to the tank to monitor the transverse position of the paper web with respect to the paper path defined by the rollers and a roller adjustment device is controlled by the sensor to adjust the web position to maintain alignment of the web with the paper path.

BACKGROUND OF THE INVENTION 
This invention relates to the handling and control of a continuous web of 
photographic paper as it is moved through the processing steps required to 
develop exposed portions of the photographic paper to produce photographic 
prints. More particularly, the invention relates to an apparatus for 
controlling the amount of time that the paper spends in various baths 
associated with the developing process, regardless of the speed at which 
paper is fed to the developing baths from a photographic printer that runs 
at its own nonconstant rate. 
In the photoprocessing industry photographic prints are produced on a 
continuous web of photosensitive paper that is exposed to the 
image-forming light in a printer. In most commerical photoprocessing 
laboratories the exposed paper is collected on a reel in a lighttight 
canister and carried from the printer to the developing baths that fix the 
image on the paper. It would be desirable to be able to run the paper from 
the photoprinter directly into the chemical baths without removal and 
manual handling of the film in order to speed the efficiency of the 
developing process by eliminating as many operator interventions as 
possible. One of the inherent problems in such a direct feed from the 
printer to the developing baths is the output of the paper from the 
printer is not usually a constant rate. The rate of output from the 
printer is affected by the type of operation occurring in the printer for 
any given batch of photos. At times the printer may be printing double 
prints of orders, while at other times the printer may be skipping over 
frames in the negative and printing only selected frames for reprints. The 
printer may be printing single prints from each frame. All of these 
different operations take different times to accomplish so that the speed 
of the printer is a variable with no advance predictability. 
On the other hand, the developing process has very strict time constraints 
on it. For example, it is necessary to immerse the photographic paper in 
the various developing and fixing baths for precise amounts of time. In 
currently used developing systems the path through the baths is a fixed 
length. Therefore, the speed of travel of the web through the developing 
bath is a constant so that the paper travels the fixed length in a 
constant time. If the output of the printer were to be fed directly into 
the developing baths, a discrepancy would exist between the variable 
output rates of the printer and the necessity of constant rate within the 
developing bath. For this reason, current thinking on the subject proposes 
the use of large storage bins or buffers that would accept the output from 
the printer and build up a large enough stock of such exposed photographic 
paper that the paper could then be fed into the developing baths at a 
constant rate, while continuing to accept paper from the printer at an 
uneven rate, with the intermediate storage bin buffering the effect of the 
uneven printer output rate. One problem with this concept is that the 
large volume of photographic paper being processed each day in the lab 
requires a very large buffer or storage space, which is prohibitive due to 
the space constraints present in most laboratories or because of the 
inefficiency of having to lease additional space in order to handle the 
storage buffer. Also, it is undesirable to have large quantities of 
exposed but unprocessed paper contained in a relatively complex large 
buffer device that is subject to breakdowns. 
SUMMARY OF THE INVENTION 
In order to provide for the direct input of photographic paper from a 
photoprinter to a tank containing developing chemicals, an apparatus is 
disclosed that provides a variable-length paper path through the 
developing tank in order to maintain the time of immersion of the paper at 
a constant value. A sensor keeps track of the length of the paper path 
through the developer and provides a feedback to the output speed control 
to maintain synchronism between the input and output speeds of paper to 
and from the tank. The paper path through the tank is defined by a series 
of rollers. At least some of the rollers are free to move vertically to 
vary the length of the path that the paper travels through the solution in 
the tank so that, regardless of input rate, the paper is submerged in the 
developing baths for a predetermined time. 
In a preferred embodiment of the invention the paper web is monitored as it 
is fed into the developing tanks to detect any transverse movement of the 
web with respect to the feed rollers. Such movement could cause the web to 
accidentally ride off the edge of one of the rollers and become jammed in 
the mechanism, thereby destroying the web. In the illustrated embodiment, 
an infeed path adjustment roller is positioned at the input to the 
developing tank and is adjustable in response to a position signal from 
the monitoring device that indicates that the paper web has shifted its 
transverse position on the roller. An adjustment system varies the angle 
of the path adjustment roller to force the paper web back into proper 
alignment with the remaining rollers in the system. 
In some applications it may be desirable to include a short mechanical 
buffer in the paper path between the output of the printer and input to 
the tank. The short buffer would smooth out short-term fluctuations in 
printer output rate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a single tank that could be used in, for example, the 
developing process for photographic prints. In a typical situation a 
plurality of these tanks would be mounted in series and filled with 
various developers, fixers, and washes. The photographic paper is run 
through each of the tanks in succession and undergoes the appropriate 
chemical processing in order to produce at the end a fixed photographic 
print. Therefore, while only one tank is shown in FIG. 1, it will be 
understood that the input to the tank 10 could either be from a previous 
tank or from a photographic printer, while the output from tank 10 could 
be directed either to a print-handling mechanism or to a subsequent tank 
containing another solution used in the developing process. 
Typically, the photographic paper will be in the form of a continuous web 
12, which has several prints photographically exposed on it. The tank 10 
contains a solution through which the photographic paper must pass in the 
developing process. The level of the solution in the tank is indicated by 
the line 14. The photographic processing is dependent upon submersion of 
the photographic paper in the solution within tank 10 for some 
predetermined time, depending on the particular solution and processing 
taking place. As discussed earlier, since the infeed to the tank 10 could 
come directly from the output of a photographic printer that outputs 
material at variable rates, the input of photographic paper to the tank 10 
will not be a constant. In order to maintain a constant immersion time of 
the photographic paper 12 in the tank 10, when the input speed of the web 
is not constant, the length of the path that the web 12 travels through 
the tank 10 is varied so that the total immersion time remains the same. 
That is, if the input speed increases then the path length must also 
increase and, alternatively, if the input speed decreases the path length 
must decrease in order to maintain the paper 12 in the tank 10 for a 
predetermined constant time. 
The web 12 is received in the nip formed by a roller pair comprised of a 
drive roller 16, which is preferably driven by a stepper motor (not 
shown), and a pressure roller 18 that is rotatably mounted at a first end 
of a spring arm 20. The spring arm 20 is biased in a downward direction to 
keep the pressure roller 18 forced against the drive roller 16 to maintain 
a grip on the paper web 12. 
As the drive roller 16 moves the paper web 12 into the tank 10, the paper 
web passes over and under a series of rollers that define the paper path 
through the tank. As viewed in FIG. 1, the system of paper handling is 
shown in its dynamic state with the paper web 12 passing over a roller 22 
rotatably mounted to an upper portion of the tank at the input side. The 
web 12 passes under a roller 24 that is rotatably mounted on a carriage 
assembly 25 that can move vertically within the tank. Two other rollers 26 
and 28 are rotatably mounted on the carriage 25 and the paper web 12 
passes beneath the rollers 26 and 28 after it has alternately passed over 
rollers 30 and 32, which are rotatably mounted at the upper portion of the 
tank 10. After the paper web 12 passes beneath the roller 28 it then 
travels upwardly in the tank 10 and passes over another stationarily 
mounted roller 34. The web then exits the tank and is grabbed by the nip 
of a pair of drive rollers 36 and 38. The exit drive roller 36 is driven 
by a stepper motor (not shown) and an exit pressure roller 38 is mounted 
on one end of a swing arm 39 that is biased downwardly to keep the exit 
pressure roller 38 biased against the exit drive roller 36 to maintain the 
paper web 12 in contact with the exit drive roller 36. The exit drive 
roller pulls the web 12 out of the tank 10. A pair of conventional 
squeegee blades 37 and 41 are positioned on opposite sides of the web 12 
to remove any excess moisture from the web. A pair of rollers 40 and 42 
are paired up to form a nip downstream from the exit drive rollers 26. The 
function of rollers 40 and 42 is primarily to aid the squeegee blades to 
squeeze the paper web sufficiently to remove a portion of the liquid that 
clings to the web due to its immersion in the developing liquid within 
tank 10. After passing through the squeeze rollers 40 and 42 the paper web 
12 moves on to a next tank 44 shown in phantom in FIG. 1. The tank 44 
would contain another paper-handling system similar to the one described. 
Alternatively, if the tank 10 were the final tank utilized in processing 
the paper, the processing would then be complete at the exit of the web 
from tank 10 and the paper web would be passed into a dryer. Once dry, the 
web can be coiled into a reel, which is then mounted in a print-cutting 
device that does not form a part of this invention, for severance of the 
prints into individual photographs. 
The carriage 25 contains rollers 24, 26, and 28 and is initially suspended 
in the tank 10 by a basket 27 that underlies the carriage 25. The basket 
27 is, in turn, suspended from a cable 46. Cable 46 is rigged through a 
series of pulleys, such as 47 and 48, and connected to a motor 49 so that 
the cable 46 can be retracted and the basket 27 can be raised and lowered 
within the tank 10. The basket 27 carries the carriage 25 with it. The 
cable 46 is used primarily to lift the basket 27 and the carriage 25 out 
of the solution, either when a new paper web must be threaded through the 
rollers on the carriage or if there is some maintenance work to be 
performed on the tank, the rollers, or the carriage, itself. The basket 27 
also catches any items that may fall into the tank and allows them to be 
retrieved. Under typical operating conditions, the cable 46 is released so 
that the basket 27 is free to drop to the bottom of the tank 10. The 
carriage 25 is then supported only by the paper web 12 itself, which 
passes underneath the rollers 24, 26, and 28 and the tension of the paper 
web 12 then supports those rollers and, in turn, the carriage 25. 
In order to maintain the proper paper path length required to provide the 
desired immersion time for the web 12, it is necessary to monitor the 
vertical position of the carriage 25. In the illustrated embodiment, the 
carriage 25 position is monitored by an encoder 50 that is mounted at the 
upper portion of the tank 10 above the stationary rollers 22, 34. A 
spindle 52 is attached to the encoder 50 and a cable 54 runs over the 
spindle 52 and is attached at one end to the carriage 25 and at a second 
end to a tension-biasing means, for example, the weight 56. As the 
carriage 25 is raised and lowered within the tank the cable 54 will move 
over spindle 52. This movement will, in turn, rotate the encoder 50. By 
keeping track of the output of the encoder 50 it is possible to maintain a 
continuous observation of the vertical position of the carriage 25. The 
position of the carriage can be used to determine the paper path length. 
Instead of the weight 56, other tensioning means, for example, a spring 
system, could be used to keep the tension on the cable 54. Also, other 
position-sensing means could also be used to track the movement of the 
carriage 25, for example, acoustic sensors. 
Turning now to FIG. 2, a more detailed view is given of the upper portion 
of the tank 10 with the paper-handling apparatus made in accordance with 
the principles of the present invention shown thereon. In FIG. 2 the 
carriage 25 is shown in its uppermost position so that all of the rollers, 
both those mounted on the tank and those mounted on the carriage, are in 
position to accept a newly fed paper web from the left. The web 12 passes 
between aligned upper and lower guide members 58 and 60, respectively, 
that form a channel within which the web can travel directly across the 
upper portion of the tank 10 to the exit rollers 36 and 38 at the exit 
side of the tank. Comparing FIG. 1 and FIG. 2, it can be seen that, once 
the web has been fed across the tank from the input feed rollers 16, 18 to 
the output rollers 36, 38, the carriage 25 is released and gravity causes 
the carriage 25 to drop vertically within the tank 10 to a position and at 
a rate determined by the tension on the web 12. The rollers 24, 26, and 28 
rest on top of the web 12 and carry the web downwardly with them as the 
carriage 25 drops. The rollers 30 and 32 move downwardly to position the 
web 12 below the surface 14 of the solution in the tank 10. As discussed 
earlier, the cable 54, which is attached to the carriage 25, is pulled 
over the pulley 52 as the carriage drops, thereby turning the encoder 50 
and providing a signal from the encoder, which can be monitored to provide 
information on the vertical position of the carriage 25 and, thereby, the 
length of the paper path through the solution. 
FIG. 4 shows in block form a control system used to accomplish the desired 
paper control. The time that the paper must be immersed in the developing 
solution is a fixed quantity. Therefore, that time of immersion must be 
achieved by considering two remaining variables, namely, paper speed and 
path length. The paper speed is determined by the output rate of the 
printer, which leaves only path length for control by the operator. The 
path length is directly related to the vertical depth of the carriage 25. 
Therefore, once the desired path length is determined from paper input 
speed and desired time of immersion, that path length is converted to a 
desired depth of the carriage 25 in the tank. The depth of the carriage 25 
is maintained by controlling the output speed of the paper. Once the 
appropriate depth is achieved, the output speed of the paper is matched to 
the input speed to maintain the desired depth. 
The control function is maintained by a central processor unit (CPU) 73 
that receives information related to the depth of the carriage 25. Based 
on that information, the CPU commands a motor controller 100 to adjust the 
output speed of a motor M.sub.1 that drives the output roller 36. The CPU 
also commands a second motor controller 102 that operates a motor M.sub.0 
that drives the input roller 16. The carriage depth information is 
provided by the encoder 50 as described above. The encoder provides an 
input to a quadrature decoder 104, which, in turn, supplies the 
information to the CPU 73. The CPU can then use the carriage depth 
information to drive the motor controllers 100 and 102 to control the 
speed of input and output motors M.sub.0 and M.sub.1. A tension means is 
shown in FIG. 4 and is represented by a spring 56'; however, the weight 56 
shown in FIG. 1 is also a suitable tension means. 
As an alternative to the encoder 50, the depth of the carriage 25 can be 
sensed using an ultrasound detection means. Such an alternative is shown 
in FIG. 4 as an ultrasound controller/processor 106 that receives 
information from a transducer 108 mounted at the bottom of the tank 10. A 
target reflector 110 is attached to the bottom of the carriage 25 to 
reflect the sound waves from the transducer 108. The controller/processor 
provides data to the CPU 73, which then utilizes the data to determine the 
depth of the carriage 25 and adjusts the motor controller M.sub.1 to bring 
the carriage to the desired depth. 
As the paper web 12 passes over and under the various rollers that define 
the paper path, there can be a tendency for the paper to shift 
transversely to the path. With any such shift the potential exists for 
damage to the paper web 12 from misalignment of the web on the rollers. In 
order to maintain the web in alignment with the rollers the web's lateral 
position is monitored by an optical sensor mounted ahead of the feed 
rollers 16 and 18 in terms of web travel. The optical sensor 60 can be any 
one of many conventional types but must operate in a light spectrum to 
which the photosensitive paper is not reactive, e.g., infrared. The 
purpose of the sensor is to sense when the web 12 moves a predetermined 
amount to the right or left of the optimum paper path over the rollers. 
The sensor 60 develops a signal that is provided to a feedback circuit 62 
that, in turn, provides a signal to a motor 64 that is mechanically 
connected to a roller 66 over which the paper web passes. The motor 64 
physically tilts the roller 66 in a plane orthogonal to the direction of 
paper travel as necessary to realign the paper web 12 with the optimum 
path. When the paper web has been repositioned, the signal from the sensor 
60 indicates the proper alignment and the motor 64 is deactivated. The 
motor 64 is illustrated as being physically connected by an arm 68 to one 
end of the roller 66. The motor 64 moves the arm 68 up and down and tilts 
the roller 66 in an appropriate direction to compensate for the transverse 
misalignment of the paper web 12 on the rollers. 
FIG. 5 illustrates in greater detail the circuit used to correct for 
transverse motion of the paper web with respect to the rollers. The sensor 
60 shown in FIG. 2 is comprised of two arrays of light-emitting diodes 
(LEDs) 75 and 76. The LEDs 75 and 76 are arranged so that, when the paper 
web 12 is in its desired location centered on the rollers, the LEDs 75 and 
76 are not blocked by the web 12 and are spaced to the outside of the 
respective edges of the web 12. In this configuration light from both the 
LEDs can reach a respective photodiode 77 or 78 positioned on the backside 
of the web 12. The photodiodes 77 and 78 are connected anode to cathode to 
one another and to an operational amplifier 79. The photodiodes are 
operated in a current mode to permit linear response and a resistor 80 is 
used to convert the signal from op-amp 79 to a voltage. The output of the 
op-amp 79 is input to an analog-to-digital converter 81, which, in turn, 
provides its output to the CPU 73. The CPU processes the information from 
the A/D converter 81 and uses it to produce a control signal that is fed 
to the motor controller 62. 
Initially, with the web 12 absent from or centered on the rollers, an 
operator using the central processor 73 sends a signal by way of 
digital-to-analog converters 82 and 83 to the drivers 84 and 85 that power 
LEDs 75 and 76 to vary the output of the LEDs until a null signal is 
present at the output of the A/D converter 81. Then, as the web 12 runs 
through the system, if there is a shift left or right of the web 12, the 
lightpath from one of the LEDs 75 or 76 to its associated photodiode, 77 
or 78, will be partially or totally blocked. The change in the light 
received from the LED will cause a change in the output of that 
photosensor. The imbalance in the outputs of the photodiodes will show up 
as a positive or negative output from the A/D converter 81. The sign of 
the signal will depend on whether the left or right photodiode is blocked. 
The output from the A/D converter will cause the motor controller 62 to 
energize the motor 64 to tilt the roller 66 in order to move the paper web 
12 sufficiently to center it on the rollers, as indicated by a balanced 
output from the photodiodes 77 and 78, which is indicated by a null output 
from the A/D converter 81. As mentioned above, the direction of tilt of 
the roller is determined by the sign of the output from the A/D converter 
81. 
Since the output of the photosensors is initially set to a balanced or null 
condition by adjusting the drivers of the LEDs 75 and 76, the system can 
compensate for aging of components or changes in ambient environment 
through simple adjustments to the outputs of the D/A converters 82 and 83. 
Another mechanism for maintaining the proper alignment of the paper web 
over the rollers as it passes through the solution is provided by rails 70 
and 72 mounted vertically on the back of the tank. The rails are engaged 
by concave wheels 74 mounted in pairs on the carriage 25. As can be seen 
in the plan view of FIG. 3, the wheels 74 maintain the carriage both in 
fore/aft and side-to-side alignment, since the concave nature of the 
wheels 74 wraps around the round rail 70 or 72 attached to the rear wall 
of the tank 10. The carriage 25 is therefore held stable within the 
solution, minimizing any misalignment of the web 12 with the paper path 
rollers that might be due to transverse or fore/aft carriage motion. Also, 
there are an upper and lower set of wheels 74 that engage the rails 70 and 
72 to prevent tipping of the carriage as a further stabilization of the 
carriage and minimize any misalignment of the web 12 with the paper path 
rollers due to carriage tilt or motion. 
It should be clear to one of ordinary skill in the art that a system for 
adjusting the length of the paper path through a solution within a 
developing tank to maintain a constant immersion time of the paper within 
the solution has been described and illustrated. The apparatus is capable 
of maintaining a constant immersion time for the paper, despite changes in 
the input rate of paper to the solution. The system can be used in 
successive developing tanks, thereby eliminating the need to monitor the 
output from the solution in order to meter the input of the paper to the 
next processing step. By varying the length of the paper path in 
accordance with the rate of input of the paper, the time in solution is 
maintained a constant. A means is also provided for monitoring and 
correcting the alignment of the paper web with the rollers that define the 
paper path to avoid slippage of the paper from the rollers and consequent 
damage to the paper. 
It will be understood by those of ordinary skill in the art and others that 
changes can be made to the above-described and illustrated invention while 
remaining within the scope of the invention. For example, while an 
encoder-based system has been described and illustrated for maintaining 
information as to the vertical position of the web within the tank, it 
would also be possible to use other types of sensors, such as ultrasonic 
sensors, to monitor such position. Also, the exact number and arrangement 
of rollers described and illustrated to define the paper path are not 
critical and other numbers of rollers and arrangements can be used to 
define the paper path through the solution. Since changes can be made to 
the illustrated embodiment, while remaining within the scope of the 
invention, the invention should be defined solely by reference to the 
appended claims.