A processor of photosensitive material includes an automatic control system for providing anti-oxidation replenishment and preventing anti-oxidation overreplenishment, as a function of a stored anti-oxidation replenishment rate and anti-oxidation replenishment provided by exhaustion replenishment. A fixed time interval is initiated after which the anti-oxidation replenishment required due to expired time is compared to the amount of anti-oxidation replenishment provided by the exhaustion replenishment in that time interval. An amount of needed anti-oxidation replenishment is added to the developer tank, as a function of the difference by which the required anti-oxidation replenishment exceeds the anti-oxidation provided by exhaustion replenishment. If the accumulated amount of replenishment exceeds the anti-oxidation replenishment needed, no replenishment is provided and the excess value is carried over to a subsequent time interval so that the accumulated overreplenishment errors which occurred in prior art fixed time/variable quantity replenishment systems are eliminated.

CROSS REFERENCE TO PATENTS AND COPENDING APPLICATIONS 
Reference is hereby made to my patents entitled AUTOMATIC REPLENISHER 
CONTROL SYSTEM, U.S. Pat. No. 4,293,211, issued Oct. 6, 1981; AUTOMATIC 
ANTI-OXIDATION REPLENISHER CONTROL, U.S. Pat. No. 4,295,792, issued Oct. 
20, 1981; and the following copending applications: AUTOMATIC 
FIXED-QUANTITY/FIXED-TIME ANTI-OXIDATION RELPLENISHER CONTROL SYSTEM Ser. 
No. 321,619 filed Nov. 16, 1981; AUTOMATIC FIXED-QUANTITY/VARIABLE-TIME 
ANTI-OXIDATION REPLENISHER CONTROL SYSTEM Ser. No. 323,073 filed Nov. 19, 
1981; and AUTOMATIC VARIABLE-QUANTITY/VARIABLE-TIME ANTI-OXIDATION 
REPLENISHER CONTROL SYSTEM Ser. No. 321,394 filed Nov. 16, 1981. All of 
these applications are assigned to the assignee of the present 
application. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an automatic anti-oxidation replenisher 
control system for use in processors of photosensitive material. 
2. Description of the Prior Art 
Automatic photographic film and paper processors transport sheets or webs 
of photographic film or paper through a sequence of processor tanks in 
which the photosensitive material is developed, fixed, and washed, and 
then transport the material through a dryer. It is well known that 
photographic processors require replenishment of the processing fluids to 
compensate for changes in the chemical activity of the fluids. 
First, it has been recognized that replenishment is necessary to replace 
constituents used as photosensitive film or paper is developed in the 
processor. This replenishment is "use related" or "exhaustion" chemical 
replenishment. Both developer and fix solutions require exhaustion 
replenishment. 
Second, chemical activity of the developer solution due to aerial oxidation 
occurs with the passage of time regardless of whether film or paper is 
being processed. Replenishment systems provide additional replenishment of 
an "anti-oxidation" (A-O) replenishment solution which counteracts this 
deterioration. 
Replenishment systems were originally manually operated. The operator would 
visually inspect the processed film or paper and manually operate a 
replenishment system as he deemed necessary. The accuracy of the manual 
replenishment systems was obviously dependent upon the skill and 
experience of the operator. 
Various automatic replenishment systems have been developed for providing 
use-related replenishment. Examples of these automatic replenishment 
systems include U.S. Pat. Nos. 3,472,143 by Hixon et al; 3,529,529 by 
Schumacher; 3,554,109 by Street et al; 3,559,555 by Street; 3,561,344 by 
Frutiger et al; 3,696,728 by Hope; 3,752,052 by Hope et al; 3,787,686 by 
Fidelman; 3,927,417 by Kinoshita et al; 3,990,088 by Takita; 4,057,818 by 
Gaskell et al; 4,104,670 by Charnley et al; 4,119,952 by Takahashi et al; 
4,128,325 by Melander et al; and 4,134,663 by Laar et al. 
Examples of prior art replenisher controls for providing both exhaustion 
and anti-oxidation replenishment are shown in U.S. Pat. Nos. Re. 30,123 by 
Crowell et al and 4,174,169 by Melander et al. In particular, these 
patents show systems which are usable to control anti-oxidation 
replenishment when a type of anti-oxidation replenishment known as 
"blender chemistry" is used. Blender chemistry is based upon a "minimum 
daily requirement" of anti-oxidation replenishment. This minimum daily 
requirement is dependent upon the amount of aerial oxidation which occurs 
in the developer tank, which in turn is dependent upon the open surface 
area of the tank, the operating temperature of the developer solution, and 
a number of other factors. With blender chemistry, some anti-oxidation 
replenishment is provided each time that exhaustion replenishment occurs. 
The more exhaustion replenishment provided, the less separate 
anti-oxidation replenishment is required. 
Crowell discloses a variable quantity, fixed time anti-oxidation 
replenishment control in which a variable amount of anti-oxidation 
replenishment needed due to aging is determined at fixed time intervals 
based upon the replenishment provided by use or exhaustion replenishment 
during the time interval. At fixed time intervals, a needed amount of 
anti-oxidation replenishment is added, which varies from zero up to a 
predetermined maximum amount. The more exhaustion replenishment provided 
during the time interval, the less anti-oxidation replenishment is 
required. The apparatus in Crowell does not consider, however, the 
situation where more anti-oxidation replenishment than is needed is 
provided by the exhaustion replenishment. Thus overage can lead to an 
accumulated error in the Crowell system. Overreplenishment of 
anti-oxidation fluid will produce incorrect processing results, just as 
will underreplenishment. There is no recognition in Crowell that this 
error accumulation can occur, or of any way to resolve it. In addition, 
the system of Crowell et al is limited by its use of analog electronics 
and electromechanical cams, which make the system difficult to calibrate 
and limit the number of control options available to the user. 
Melander et al discloses a fixed quantity, variable time anti-oxidation 
system based on a counter which is set to a predetermined value and then 
counted down over time to measure oxidation of processor fluid. When the 
counter reaches zero, a fixed amount of anti-oxidation replenisher is 
added. The counter is counted up to reflect anti-oxidation replenishment 
provided as a result of exhaustion. 
SUMMARY OF THE INVENTION 
The automatic control system of the present invention is an improved fixed 
time, variable quantity automatic anti-oxidation replenishment control 
system which eliminates the accumulated overreplenishment errors which 
occurred in prior art fixed time, variable quantity systems. A time 
interval is initiated and measured by a clock means. The amount of 
anti-oxidation replenishment provided as a result of the exhaustion 
replenishment is used to provide a first replenishment signal. A stored 
anti-oxidation replenishment rate and the measured time are used to 
provide a second replenishment signal indicative of how much 
anti-oxidation replenishment is needed. The two signals are compared at 
the end of the interval. If the second signal is greater than the first 
signal, an amount of anti-oxidation replenishment is supplied to the 
developer tank as a function of the difference between the two signals. 
If, on the other hand, the first signal exceeds the second signal, no 
anti-oxidation replenishment is provided and the excess is carried over to 
the comparison made at the end of the subsequent interval so that 
accumulated overreplenishment errors are avoided. 
In one embodiment, the generation and comparison of signals in the 
subsequent interval is inhibited if the difference by which the first 
signal exceeds the second signal is greater than the maximum 
anti-oxidation replenishment needed in the subsequent interval.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the system shown in FIG. 1, a photographic processor includes developer 
tank 10, fix tank 12, wash tank 14, and dryer 16. Film transport drive 18 
transports a strip or web of photosensitive material (either film or 
paper) through tanks 10, 12, 14 and dryer 16. Microcomputer 20 controls 
operation of film transport 18 and of the automatic replenishment of 
fluids to tanks 10, 12 and 14. 
The automatic replenishment system for preventing overreplenishment of 
anti-oxidation fluid includes developer replenisher 22 and anti-oxidation 
replenisher 24 for providing exhaustion and anti-oxidation replenishment, 
respectively, to developer tank 10. Microcomputer 20 controls operation of 
developer replenisher 22 and receives a feedback signal indicating 
operation of developer replenisher 22. Although in a typical processor fix 
and wash replenishment also are provided, these functions are not a part 
of the present invention, and therefore are not shown or discussed herein. 
Anti-oxidation replenisher 24 includes anti-oxidation (A-O) replenisher 
reservoir 26, pump 28, pump relay 30, and flow meter or switch 32. 
Anti-oxidation replenishment is supplied from A-O replenisher reservoir 26 
to developer tank 10 by pump 28 by means of relay 30, which is controlled 
by microcomputer 20. Flow meter or switch 32 monitors flow of A-O 
replenishment to developer tank 10 and provides a feedback signal to 
microcomputer 20. 
Microcomputer 20 utilizes A-O counter 34 as a timer to control 
anti-oxidation replenishment. When anti-oxidation replenishment is 
required, microcomputer 20 loads a numerical value (AOXTIME) into A-O 
counter 34, which then begins counting. Microcomputer 20 energizes relay 
30, which activates pump 28. When A-O counter 34 reaches a predetermined 
value (such as zero), it provides an interrupt signal to microcomputer 20, 
which deenergizes relay 30. The numerical value (AOXTIME), therefore, 
determines the total amount of anti-oxidation replenisher pumped into tank 
10. 
AOX timer 36 is a free running resettable timer which initiates and records 
a fixed time interval. As described later, this time interval is used by 
microcomputer 20 in the control of anti-oxidation replenishment. 
Microcomputer 20 receives signals from film width sensors 38 and density 
scanner 40. Film width sensors 38 are positioned at the input throat of 
the processor, and provide signals indicating the width of the strip of 
photosensitive material as it is fed into the processor. Since 
microcomputer 20 also controls film transport 18, and receives feedback 
signals from film transport 18, the width signals from film width sensors 
38 and the feedback signals from film transport 18 provide an indication 
of the area of photosensitive material being processed. 
Density scanner 40 senses density of the processed photosensitive material. 
The signals from density scanner 40 provide an indication of the 
integrated density of the processed photosensitive material. The 
integrated density, together with the area of material processed, provides 
an indication of the amount of processor fluids used or exhausted in 
processing that material. 
Microcomputer 20 also receives signals from control panel 42, which 
includes function switches 44, keyboard 46, and display 48. Function 
switches 44 select certain functions and operating modes of the processor. 
Keyboard 46 permits the operator to enter numerical information, and other 
control signals used by microcomputer 20 in controlling operation of the 
processor, includng the replenishment function. Display 48 displays 
messages or numerical values in response to control signals from 
microcomputer 20. 
Microcomputer 20 preferably stores set values for each of a plurality of 
photosensitive materials that may be processed in the processor. Each 
group of set values includes a pump rate for pump 28 (AOXPMPRTE), and the 
desired replenishment rate of anti-oxidation replenishment (AOXRT). 
When operation is commenced, the operator selects (through control panel 
42) one of the groups of set values which corresponds to the particular 
photosensitive material being processed. As the leading edge of each strip 
of photosensitive material is fed into the processor, film width sensors 
38 sense the presence of the strip, and provide a signal indicative of the 
width of the strip being fed into the processor. Width sensors 38 continue 
to provide the signal indicative of the width of the strip until the 
trailing edge of the strip passes sensors 38. The length of time between 
the leading and trailing edges of the material passing sensors 38, and the 
transport speed of the material (which is controlled by microcomputer 20 
through film transport 18) provide an indication of the length of the 
strip. The width and length information for each strip is stored until the 
strip has been transported through the processor and reaches density 
scanner 40. The area of the strip and the integrated density of the strip 
(which is provided by the signals from density scanner 40), provide an 
indication of the amount of developer which has been exhausted in 
processing that particular strip. 
As discussed previously, the present invention relates to the type of an 
anti-oxidation replenishment known as "blender chemistry". Blender 
chemistry is based upon a "minimum daily requirement" of anti-oxidation 
replenishment. This minimum daily requirement is dependent upon the amount 
of aerial oxidation which occurs in developer tank 10, which in turn is 
dependent upon the open surface area of tank 10, the operating temperature 
of the developer solution, and a number of other factors. With blender 
chemistry, some anti-oxidation replenishment is provided each time that 
exhaustion replenishment occurs. The more exhaustion replenishment 
provided, the less separate anti-oxidation replenishment is required. 
An anti-oxidation replenishment control system of the present invention, as 
shown in FIG. 1, uses pump 28 to transfer the needed amount of 
anti-oxidation replenisher from anti-oxidation replenisher reservoir 26 to 
developer tank 10. Anti-oxidation counter 34 is used to measure the amount 
of time that pump 28 will run, so that the correct amount is transferred 
to developer tank 10. When microcomputer 20 activates relay 30 to start 
pump 28, A-O counter 34 begins timing. When the proper amount of 
anti-oxidation is transmitted, pump 28 is stopped. Flow meter or switch 32 
provides to microcomputer 20 a feedback signal for use in determining that 
replenisher has been provided to developer tank 10. 
The supplying of anti-oxidation replenisher to the processor using the 
system of the present invention is generally as follows. AOX timer 36 
initiates a fixed time interval. During this time interval, exhaustion 
replenishment is provided by exhaustion replenisher 22. This is done, as 
discussed above, as a function of the use of the developer fluid in tank 
10. The use is indicated by the signals from film width sensors 38, 
density scanner 40, and film transport 18. Microcomputer 20 then 
determines and stores the accumulated amount of anti-oxidation 
replenishment supplied as a result of that exhaustion replenishment 
(AOXDEV) during the current time interval. At the end of the interval, AOX 
timer 36 provides a clock interrupt signal to microcomputer 20. 
Microcomputer 20 uses a stored anti-oxidation replenishment rate (AOXRT) 
and the time expired in the interval (AOXTM), as measured by AOX timer 36, 
to determine a second signal (AOXRT.times.AOXTM) which indicates the 
amount of anti-oxidation replenishment required in the current time 
interval. Microcomputer 20 then compares the first signal (AOXDEV) 
indicating the accumulated amount of anti-oxidation replenishment supplied 
in the interval as a result of the exhaustion replenishment with the 
second signal (AOXRT.times.AOXTM) indicating anti-oxidation replenishment 
required at the current time in the interval. If the first signal is 
greater than the second signal, no anti-oxidation replenishment is 
required and the microcomputer 20 goes on with its normal operating steps. 
If the second signal is greater than the first, the microcomputer 20 
activates anti-oxidation replenisher 24 to provide the needed amount of 
anti-oxidation replenisher (AOXREPL) to developer tank 10. 
The Table illustrates how microcomputer 20 determines and controls 
anti-oxidation replenishment in accordance with the embodiment of the 
present invention. AOXREPL is the needed quantity of anti-oxidation 
replenishment fluid. 
AOXNEG keeps track of excess anti-oxidation replenishment so that the 
system will not be overreplenished in the subsequent time period. 
Table 
1. AOX timer 36 times out (e.g. 22.5 minutes) 
1.a If ((AOXRATE/64)+AOXNEG) is less than zero, 
(a) update AOXNEG=(AOXRATE/64)'AOXNEG 
(b) reset AOX timer and exit 
2 AOXREPL=(AOXRATE/64)-AOXDEV+AOXNEG 
(a) if AOXREPL is less than zero, 
(b) then AOXNEG=AOXREPL 
(c) reset AOXDEV 
(d) reset AOX timer and exit 
(e) else reset AOXDEV 
3 reset AOXNEG to zero 
4 AOXTIME=(AOXREPL/AOXPMPRTE)+AOXMINRUN 
5 If AOXTIME less than 7.5 seconds then 
(a) calculate AOXMINRUN=AOXMINRUN+AOXTIME 
(b) reset AOX timer and exit 
6 Output AOXTIME to A-O counter 34 
7 Trigger pulse sent to counter 34 and 
(a) Replenish flag (AOX) set 
8 Counter 34 begins decrementing and 
(a) Anti-ox replenishment pump 28 runs 
(b) When counter 34 times out, go to 11 
9 If flow switch 32 does not activate and/or Anti-ox replenishment pump 
relay 30 does not energize then ERROR 
10 If pump enable is turned off while counter 34 is running then 
(a) Wait 5 seconds 
(b) If change then resume 8 Else 
(1) Read value remaining in counter 34 to AOXREM 
(2) Clear counter 34 
(3) Replenish flag (AOX) reset 
(4) Reset AOX timer and exit 
11 Counter 34 times out and 
(a) Interrupt request generated 
12 If interrupt request not acknowledged then wait; 
Else 
13 If flow switch 32 remains activated and/or pump relay 30 remains 
energized then ERROR; 
Else 
14 Reset replenish (AOX) flag and AOX not complete flag and clear AOXMINRUN 
FIG. 2 contains a graphic representation of how anti-oxidation 
replenishment is added according to the steps shown in the Table. The 
horizontal axis indicates expired time. Curve 80 shows the need for 
anti-oxidation replenishment due to oxidation over time. Curve 80 has a 
constant slope. This is determined, in the process illustrated by the 
Table, by dividing the rate of oxidation (AOXRATE) by the number of fixed 
intervals in a day. Dashed curve 82 represents anti-oxidation 
replenishment provided as a result of exhaustion replenishment (AOXDEV). 
At any point along the time line, the vertical distance between the two 
lines represents the anti-oxidation status of the system. If the curve 82 
is below curve 80, the system is underreplenished. If curve 82 is above 
curve 80, the system is overreplenished. 
In the example shown in FIG. 2, a first fixed time interval is initialized 
at time T.sub.0. The fixed time intervals end at times T.sub.1, T.sub.4, 
T.sub.7, and T.sub.10. During the first time interval from T.sub.0 to 
T.sub.1, no exhaustion replenishment occurs. The need for anti-oxidation 
replenishment increases at a steady rate throughout the period. At time 
T.sub.1, the need for anti-oxidation replenishment represented by curve 80 
is compared with the AOXDEV, represented by curve 82. Brace 100 represents 
this value. The amount of needed anti-oxidation replenishment (AOXREPL) is 
then added at time T.sub.1. 
During the second time interval from time T.sub.1 to time T.sub.4, 
exhaustion replenishment occurs at times T.sub.2 and T.sub.3. Therefore, 
at the end of the second interval at time T.sub.4, the difference between 
the two curves is much smaller than at the end of the first interval. The 
needed amount of anti-oxidation replenishment (AOXREPL) that is added at 
time T.sub.4 is correspondingly smaller. 
A third interval extends from time T.sub.4 to time T.sub.7. During this 
interval, exhaustion replenishment occurs at times T.sub.5 and T.sub.6. At 
time T.sub.5, the exhaustion replenishment curve 82 intersects the curve 
80 and extends above it. For the period from time T.sub.5 to time T.sub.6, 
the system is slightly overreplenished as to anti-oxidation. At time 
T.sub.6, the curves intersect. When exhaustion replenishment occurs at 
time T.sub.6, the system is again overreplenished. When the interval ends 
at time T.sub.7, the system is still overreplenished. Therefore, no 
anti-oxidation replenishment is provided and the parameters are not 
reinitialized. Computation continues through the next period, which 
extends from T.sub.7 to T.sub.10. At time T.sub.8, the curves again 
intersect and the system is slightly underreplenished when exhaustion 
replenishment occurs again at time T.sub.9. At time T.sub.10 at the end of 
the fourth interval, the system is underreplenished. At this point, 
anti-oxidation replenishment (AOXREPL) occurs. The parameters are 
reinitialized and the intervals start anew. 
A variable quantity system is best used in a system where precision in 
replenishment is required. A variable quantity system provides exact 
measurement. A control system constructed according to the present 
invention eliminates the problem of accumulated anti-oxidation 
overreplenishment errors to which the prior systems were subject. By 
considering in a subsequent interval the excess anti-oxidation 
replenishment provided by exhaustion replenishment in a previous interval, 
the accumulated overreplenishment errors are prevented. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.