EP0287761A2

EP0287761A2 - Apparatus and method for neutralizing oxidizing agents in a laundry machine

Info

Publication number: EP0287761A2
Application number: EP88102045A
Authority: EP
Inventors: Daniel F. Brady; Peter W. Rauen
Original assignee: Ecolab Inc
Current assignee: Ecolab Inc
Priority date: 1987-04-24
Filing date: 1988-02-12
Publication date: 1988-10-26
Anticipated expiration: 2008-02-12
Also published as: EP0287761A3; EP0287761B1; DE3874391T2; NZ223338A; DE3874391D1; AU1136688A; JPS63283700A; AU597474B2

Abstract

A method and apparatus for automatically neutralizing excess oxidizing agents in a laundry solution on a real-time basis are disclosed. The amount of oxidizing agent present at any instant of time in a laundry solution is measured and compared against a predetermined acceptable level therefor. A neutralizing agent suitable for reducing the oxidizing agent is automatically added to the laundry solution on a demand basis, until the oxidizing agent has been neutralized within the predetermined acceptable level, and without excessive addition of neutralizing agent to the bath or to the textile being processed thereby.

Description

Field of the Invention

The present invention relates generally to the neutralization of oxidizing agents in a laundry solution, and more particularly to apparatus and a method for automatically monitoring and precisely controlling the concentration of oxidizing and reducing agents in the final rinse step of a laundry cycle.

Background of the Invention

The use of oxidizing agents such as destainers and bleaches for treating laundry during a wash formula or cycle is commonplace today in both residential and commercial laundering operations. The most commonly used strong bleaching agents are sodium hypochlorite (chlorine bleach) and potassium permanganate. Chlorine bleach is more popular than the other major type of bleach, hydrogen peroxide, because it costs significantly less, is more effective at removal of certain types of stains, and is a better sanitizer.
A disadvantage of using destainers such as chlorine bleach is that fabric damage can result if the bleach is overused or if the bleach is not thoroughly rinsed from the fabric. Chlorine bleach is an example of an oxidizing agent that works by releasing "free" oxygen which, in turn, reduces stains. If residual chlorine is allowed to remain in the fabric as a result of the laundering cycle, the oxygen-producing agent of the bleach will continue to attack the fabric's fibers which are converted into oxidized cellulose known as oxycellulose. As a result, the fabric may develop holes or tears in weakened areas. Because the tensile strength of the fabric decreases, the fabric's wear life is shortened and the fabric tears more easily. The damage caused is irreversible. Further, even a relatively small amount of residual chlorine, for example 1 to 2 parts per million, is sufficient to cause fabric damage.
For the sake of simplification, the remainder of the discussion will address only chlorine bleach oxidizing agents; however, it will be understood that the general problems and principles discussed with regard to chlorine bleach oxidizing agents apply equally well to other types of destainers and oxidizing agents and to their respective neutralizing or reducing agents, when discussed.
The problem of chlorine removal or neutralization in a laundry cycle is less pronounced in conventional tubtype or batch washing machines wherein the entire laundry tub is filled and drained typically after each portion of a wash formula. The opportunity for completely rinsing chlorine destainer additives from the laundry in such "conventional" machines is fairly good. Further, such "conventional" washing machines typically employ separate wash and bleaching cycles which enable the bleach to be added to relatively low pH solutions, thereby enhancing relatively thorough rinsing of the chlorine from the fabric during the rinse cycles. However, to the extent that the chlorine additives are not entirely removed from or neutralized in such conventional washing systems, the principles of this invention apply thereto.
For a more detailed description of the principles involved regarding oxidation agents and their respective reducing/neutralizing agents, including a discussion of the meaning of "bleach", "active chlorine" and "available chlorine" see White, George, Handbook of Chlorination, 1972, pp. 189-190, which is herein incorporated by reference.
The problem of chlorine removal from the laundry and/or neutralization thereof is significantly more pronounced in commercial washing applications in which normal bleaching levels are typically significantly increased from the traditional level of 1 quart of 1% bleach per 100 pounds of wash, in order to achieve effective stain removal. The problem is further amplified in commercial applications wherein continuous batch washers or tunnel washers are used. Tunnel washers are becoming increasingly popular in industrial laundry applications, particularly for such applications as the processing of hospital, hotel and other linen supply works, where large quantities of laundry must be cleaned daily. In general, tunnel washers include a series of individual modules or compartments each of which corresponds to a different step in the wash formula or cycle. The textiles to be washed are automatically transported through a continuous loading, washing, rinsing, conditioning and extracting process as they progress from the input to the output of the tunnel washer. The tunnel washing technique significantly reduces labor, since once the laundry is sorted into batches which are successively loaded into the input hopper of the tunnel washer, they are not handled again until they have been conditioned or dried. Utility costs associated with tunnel washers are lower than conventional-type washing systems and processing time is significantly reduced since there is no delay time for water filling of the machine or waiting time for drying or extracting operations.
Tunnel washers are basically constructed in either double drum (modular) configuration or single drum (monoshell) configuration. The modular washers have adjacent but separately defined individual compartments each of which performs a different function. The laundry batches progressively move through the compartments which form an inner cylinder of the machine, and are successively transferred from module to module upon completion of the process step therein by raising the laundry batches above the center line of the washer and sliding them through a central connection between the modules. The single drum tunnel washers typically use an Archimedes' screw principle which uses a screw member that extends longitudinally through the drum for defining the various steps of the wash formula and for moving the batches of laundry forward through the drum. Typically each turn or segment of the spiral screw defines a laundry compartment, and the transfer action is achieved when the cylinder or screw rotates through one complete revolution, to move the textiles forward into the next compartment. Tunnel washing apparatus is well known in the art, and a complete description of such apparatus will not be defined herein. The foregoing merely serves as a brief introduction of the advantages to be achieved by the use of tunnel washers in commercial laundering applications, and as a prelude to the problems created by such washing systems in the neutralization of excess oxidizing agents in laundry processed thereby.
Typically a tunnel washer apparatus requires approximately three times the amount of bleach for effectively treating a batch of laundry, than does a washer of "conventional" tub design. One reason for the excessive bleach requirement is that the bleach to be effective, is typically added during the wash cycle in a tunnel washer, in which the presence of detergents and alkalines significantly raise the pH levels of the solutions in the washing chambers. Even if the bleach is added during a rinse cycle in a tunnel washing system, a significant amount of bleach is required because of the relatively low temperatures involved at that stage and the relatively high flow rate of water in the rinse zone. Accordingly, since it is fairly impractical to thoroughly remove excess chlorine from the laundry fabric in commercial washing apparatus such as the tunnel washers, the industry has typically resorted to adding neutralizing agents, typically at the final "rinse" stage of the laundry cycle for neutralizing the excess chlorine. When chlorine bleaches are used, the neutralizing agent is typically referred to as an antichlor product. A common antichlor is sodium thiosulfate.
It has been common in the commercial laundering industry to inject the neutralizing agent into the final rinsing module or compartment of a tunnel washer which is typically the next to the last processing step in the wash formula. The final cycle step is typically used to recondition the laundry to add such conditioning chemicals as softeners, sours and the like, that had been previously stripped from the laundry, back into the textiles. Typically, the antichlor or neutralizing agent that is added to the final rinse step for neutralizing excess chlorine in the fabric has been added on a "timed-feed" basis. That is, a fixed, predetermined amount of antichlor has typically been added to each batch of laundry at the final rinse cycle, regardless of the actual amount of residual chlorine in the laundry requiring neutralization. The amount of antichlor added to the rinse has on occasion been varied from cycle to cycle depending upon the type of fabric within the rinse compartment, which may, for example, have a history of retaining more or less chlorine. However, in general, the "timed-feed" technique for adding antichlor neutralizer into the rinse container is a highly speculative technique based on the best guess of the operator or manufacturer of the washing apparatus as to how much neutralizer should be added.
In fact, the actual amount of oxidizing agent that requires neutralization in the rinse compartment of a washer is highly variable. The residual chlorine level in the rinse solution depends upon a plethora of variables such as on the amount of chlorine added during the wash cycle, on the type of fabric, on the amount of soil present, on the temperature, on the pH level, on the detergent and alkaline level, on how long the laundry has been subjected to the destainer solution, on the amount of iron in the water, and on the type of destainer/oxidizing agent solution that had been used. Obviously, the presently practiced method of injecting a fixed amount of neutralizing/antichlor agent on a timedfeed basis into the rinse solution, to neutralize the oxidizing agents therein results in a poor solution to the problem. Injection of too little neutralizing agent results in extensive irreversible damage to the fabric due to excess residual chlorine in the fabric, as discussed above. On the other hand, injection of too much antichlor into the solution, solves the destructive residual chlorine problems, but is wasteful of the relatively expensive antichlor product, and creates undesirable residual buildup of salts in the textile fabric which causes greying of the textile when ironed, decreases the textile's wear life and results in a harsh feel to the fabric unless further treated with a softener. With the use of timed-feed techniques it is not uncommon to find residual salts left in the textile fabric that could be higher than 20-30 parts per million.
The present invention addresses these problems associated with present-day techniques for neutralizing excessive oxidation agent retention in laundered textiles, by providing an automated method and apparatus for accurately neutralizing only that amount of oxidizing agent actually present in the laundry solution during any given laundry cycle and which prevents the overinjection of neutralizing or reducing agents into the laundry cycle that can lead to fabric damage.

Summary of the Invention

The present invention provides an automated method and apparatus for neutralizing excess oxidizing agents such as destainer chemical additives in a laundering solution such as at the final rinse stage of a wash formula. The oxidation reduction potential of the solution to be neutralized is constantly monitored in a closed loop system. The monitored oxidation reduction potential signal is compared with a signal representing the desired neutralization level of the solution and enables injection of neutralizing agents to the solution in response to the compared signals, until the measured oxidation reduction potential signal indicates oxidation agent neutrality within the solution. In a preferred application of the invention, the neutralization agent injection is performed on a periodic pulsed basis with an interpulse duty cycle sufficiently long to enable the last-injected measure of neutralizing agents to thoroughly disperse and react in the solution, before injection of additional neutralizer agent is permitted. Injection of neutralizer reduction agents into the solution is accurately controlled such that once neutralization of the oxidizing agents present in the solution is achieved, injection of additional neutralizing reduction agents is prevented, so as to maintain the concentration of both reduction and oxidation agents in the solution preferably to within approximately 1 part per million.
Accordingly, the invention effectively regulates the oxidation and reduction agents so as to practically eliminate 100% of their residual remains in the fabric following a treatment cycle. The present invention also reduces the cost of neutralization treatments by eliminating overinjection of expensive reducing agents to the bath and extends the fabric-wear life by reducing retained oxidation agents and salts therein.
According to one aspect of the invention, there is provided a method of neutralizing oxidation agents in a laundry bath, comprising:

(a) determining the amount of an oxidizing agent to be neutralized that is present in a laundry bath at any particular instant of time, and providing a sensed signal in response thereto;
(b) injecting a measured amount of a neutralizing agent of a type capable of reducing the oxidizing agent, into the bath in response to the sensed signal;
(c) terminating the injection of neutralizing agent into the bath when the sensed signal indicates that the amount of the oxidizing agent to be neutralized which remains in the bath is less than about 5 parts per million.

According to a further development of the invention, the neutralization process more preferably terminates the neutralizer injection procedure when the amount of oxidizing agent to be neutralized which remains in the bath is less than 2 parts per million and even more preferably when it is less than 1 part per million, or most preferably only after the neutralizing agent totally neutralizes the oxidizing agent in the bath. According to a further aspect of the invention, the above injection process further controls injection of the neutralizing agent into the bath so as to prevent undesirable overinjection of the neutralizing agent above a level of 20 parts per million level of unreacted neutralizing agent and more preferably still so, as to prevent overinjection of the neutralizing agent above a 1 part per million level of unreacted neutralizing agent.
According to a preferred method of injection of the neutralizing agent into the bath, such injection is performed on an intermittent periodic pulsed basis, by a pump which is selectively and periodically energized in response to the real-time measured amount of oxidizing agent present in the bath at any particular instant of time.
According to another aspect of the invention, there is provided a method of automatically neutralizing an oxidizing agent in a laundry bath which comprises the steps of:

(a) quantitatively sensing the presence of an oxidizing agent to be neutralized in the laundry bath and providing a sensed signal in response thereto which is indicative of the amount of the oxidizing agent in the bath;
(b) selecting a maximum acceptable threshold level for the oxidizing agent in the bath and producing a threshold signal indicative thereof;
(c) comparing the sensed and the threshold signals and producing a comparison signal in response thereto;
(d) injecting a neutralizing agent of a type suitable for reducing the oxidizing agent, into the bath, in response to the comparison signal; and
(e) terminating the addition of neutralizing agent to the bath when the unneutralized oxidizing agent remaining in the bath is less than the maximum acceptable threshold level.

According to yet another aspect of the invention, there is provided a method of laundering a textile including the steps of:

(a) placing the textile in the laundering bath;
(b) subjecting the textile to destainer including an oxidizing agent;
(c) rinsing substantially all of the oxidizing agent from the textile except for a minute residual amount thereof;
(d) subjecting the textile to a neutralizing agent of a type suitable for reacting with the residual oxidizing agent;
(e) causing the residual amount of the oxidizing agent to react with the neutralizing agent until the amount of residual unneutralized oxidizing agent in the textile is less than about 5 parts per million and more preferably less than about 1 part per million; and
(f) preventing overexposure of the textile to the neutralizing agent such that retention of the neutralizing agent by the textile is less than about 5 parts per million and more preferably less than about 1 part per million.

According to yet another aspect of the invention, there is provided a textile laundered according to the above-described laundering method.
According to yet another aspect of the invention, there is provided apparatus for performing the abovedescribed methods of neutralizing oxidizing agents in a laundry bath. One such apparatus for automatically neutralizing oxidizing agents in a laundry bath comprises:

(a) means for determining the amount of an oxidizing agent to be neutralized that is present in the laundry bath at a particular instant of time and for providing a sensed signal in response thereto;
(b) means operatively connected to receive the sensed signal for injecting a measured amount of neutralizing agent of a type capable of reducing the oxidizing agent, into the bath in response to the sensed signal; and
(c) means operatively connected to receive the sensed signal for terminating injection of the neutralizing agent into the bath when the sensed signal indicates that the amount of the oxidizing agent to be neutralized which remains in the bath is less than about 2 parts per million, and more preferably less than about 5 parts per million and most preferably when less than about 1 part per million.

According to a further aspect of the invention, there is provided such apparatus as above-described, which also includes means for terminating the injection of neutralizing agents into the bath before excess unreduced neutralizing agent being introduced into the bath exceeds 20 parts per million, and still more preferably before such excess unreduced neutralizing agent in the bath exceeds 5 parts per million and most preferably before they exceed 1 part per million.
According to another aspect of the invention, there is provided apparatus for automatically neutralizing oxidizing agents in a laundry bath, comprising:

(a) means for quantitatively sensing the presence of an oxidizing agent to be neutralized in the bath and for providing a sensed signal in response thereto which indicates the amount of the oxidizing agent in the bath;
(b) means for establishing a maximum acceptable threshold level for the oxidizing agent in the bath and for producing a threshold signal indicative thereof;
(c) comparator means operatively connected to receive the sensed and the threshold signals, for comparing them and for producing a comparison signal in response thereto;
(d) means operatively connected to receive the comparison signal and also to a source of neutralizing agent of a type suitable for reducing the oxidizing agent, for injecting the neutralizing agent into the bath in response to the comparison signal; and
(e) control means operatively connected to the injection means for terminating the addition of neutralizing agent to the bath when the unneutralized oxidizing agent remaining in the bath is less than the maximum acceptable threshold level established therefor.

It will be understood that while the present invention as described with respect to a particular type of washing apparatus (i.e. a tunnel washer), that the invention is not limited to use with any particular type of laundry machine. While the practical economics of constructing such apparatus that practice this invention primarily would dictate that the invention be used in commercial laundering applications such as with tunnel washers and large batch tub-type laundering applications, the principles of the invention apply to all laundering applications wherein it is desired to minimize the amount of oxidizing agents in the laundered textile and also to minimize the amount of residual neutralizing agent introduced into the textile during the neutralization process. Further, while the present invention will be described with respect to particular types of circuits and individual components therein, the invention is not limited to the use of such circuits or disclosed components thereof. Such circuits and components have been described to merely illustrate one possible embodiment of a control network that can be used to implement the principles of this invention.
These and various other advantages and features which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and objectives obtained by its use, reference should be had to the Drawing which forms a further part hereof and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

Detailed Description of the Drawing

Referring to the Drawing, wherein like numerals represent like parts throughout the several views:

Fig. 1 is a diagrammatic illustration of a continuous batch tunnel washing system, illustrating the Automatic Neutralizer Control Circuit of this invention in relation thereto;
Fig. 2 is a block diagram illustration of the functional blocks of the Automatic Neutralizer Control Circuit disclosed in Fig. 1;
Fig. 3 is a schematic diagram of the Amplifier and Signal Conditioning functional block of the diagram disclosed in Fig. 2; and
Fig. 4 is a schematic diagram of the Comparator, Set Point Adjustment and the Adjustable Pulse Control functional blocks of the Automatic Neutralizer Control Circuit disclosed in Fig. 2.

Detailed Description of the Preferred Embodiment

While the present invention can be used to neutralize the contents of a container of any type of laundry machine, its preferred use is with commercial laundry machines, and particularly with those typically referred to as batch washer systems and to continuous batch washer systems referred to as "tunnel washers". The preferred embodiment of the invention will be described with respect to its application with a tunnel washer system. A diagrammatic illustration of a typical continuous batch tunnel washer system is schematically illustrated in Fig. 1. Such tunnel washers are well known in the art, and the details of construction thereof will not be set forth herein. Rather, a brief functional description of a tunnel washing system should suffice to illustrate how the present invention can be used to advantage therewith in commercial laundry applications. Typical of such a washer system would be the double-shell tunnel washer as, for example, manufactured by Pellerin Milner Corporation of Kenner, Louisiana, under its Model CBW label.
Referring to Fig. 1, the tunnel washer, generally illustrated at 10, contains ten separate laundry processing modules or containers, generally indicated at 11-20. Each of the modules is associated with a portion of the complete laundering cycle. While ten such modules and laundry functions are illustrated in Fig. 1, it will be .understood that the number of steps in the laundering cycle and modules employed therefor can widely vary, depending upon the particular laundering requirements of the equipment. In the embodiment illustrated, the various modules and laundering functions are indicated as: Flush (11), Break (12), Break (13), Suds (14), Flush (15), Bleach (16), Rinse (17), Rinse (18), Rinse (19) and Conditioning (20). In the preferred embodiment, each of the modules 11-20 is uniquely associated with performing its associated "function" on a batch of laundry contained in that module. Each of the modules 11-20 is operatively connected with one another, generally in longitudinal alignment such that a batch of laundry can progressively move through the tunnel washer 10 during a complete laundering cycle, from the first module 11 to the final module 20. Each module is sized to contain a "batch" of laundry, generally illustrated at "L" in Fig. 1. The batches of laundry are introduced into the input hopper 10A of the washer 10, and are withdrawn from the exit end 10B of the washer, where the laundry is typically conveyed to extraction and drying apparatus (not illustrated). Means (not illustrated) typically in the form of a large auger which longitudinally extends from the input end 10A to the output end 10B of the washer 10 simultaneously successively moves the batches of laundry from module to adjacent module during the laundering cycle. The length of time that a batch of laundry remains in any particular module varies depending upon the design of the tunnel washer, and is typically from three to ten minutes depending on the chemical additive formulas, and the type and amount of laundry being processed. The various laundry processing steps performed within the modules 11-20 of the tunnel washer are typically under microprocessor or computer control (not illustrated) which provide for the proper addition and extraction of water and additives including such things as detergent, bleach, softeners and the like as the batches of laundry automatically progress through the tunnel washer. The primary control network also controls the reuse of solutions, where appropriate, between adjacent modules and the reuse of recovered water from, for example, extraction or drying processes. The primary control network is also responsible for properly timing the movement of batches of laundry "L" between modules at the completion of steps of the cycle and can typically be programmed to distinguish between incompatible batches of laundry that have been successively loaded into adjacent modules of the washer so that cross-contamination between such incompatible batches of laundry is avoided (as for example, when "white" clothes follow "colored" clothes). The primary control network also is responsible for determining the type and quantity of chemicals that will be added to each module for the particular batch of laundry being processed thereby, for determining whether the modules will be filled rapidly or slowly, and for determining the mode of drainage of the respective modules.
Referring to Fig. 1, the various means for filling the respective module containers of the washer 10 are schematically illustrated near the upper portions of the respective modules by arrows with the following designations: "CA" meaning Chemical Augmentation; "FF" meaning Fast Fill; and "SF" meaning Slow Fill. Draining of the module containers is schematically illustrated by arrows exiting from the lower portions thereof with the following designations: "FD" meaning Fast Drain; "SD" meaning Slow Drain; and "TD" meaning Transfer Drain. Each of the modules which has a Transfer Drain outlet includes a transfer conduit which flows back into the immediately preceding adjacent module, providing an inlet thereto, designated in Fig. 1 as "TI" meaning Transfer Inlet. Each of the "TI/TD" conduit arrangements has associated therewith a pair of valves (generally designated at "V" in Fig. 1) operatively controlled by the laundry machine primary control network (not illustrated) for directing solution counterflow between adjacent modules, as dictated by the laundering requirements. The tunnel washer 10 of the embodiment illustrated also includes a pump "P" for pumping water from a "Reuse Water Tank" 22 through, a filter 23 to a fill inlet (generally designated at "F") leading into the input hopper 10A of the washer 10. Water recovered from various operations such as extraction and drying stages may provide a source of input water for the tank 22. A batch of laundry "L" is indicated in Fig. 1 as resting on a conveyor 24 adjacent the inlet hopper 10A, awaiting introduction to the tunnel washer 10. The conveyor 24 is also under control of the primary control network of the washer 10.
It will be understood by those skilled in the art that the tunnel washer described above is merely illustrative of one configuration of many possible variations of such continuous batch washing systems currently found in the art and of others that fall within the broad description of such systems.
The present invention provides an automated method and apparatus for removing excess oxidizing agents such as destainer chemical additives from the laundry solution at the final rinse stage or process of the laundering cycle, to thereby, remove excess oxidizing agents from the laundry being processed at that stage. The present invention not only automatically removes the excess oxidizing agents from the laundry but also safeguards against the addition of excess neutralizer chemicals, which can also have a detrimental effect on the laundry as well as inflating the cost of the neutralizing process. While the principles of this invention could be applied to any of the processing steps in a washing cycle, they are most practically applied
at the "Final Rinse" stage in a laundering cycle, just prior to the "reconditioning" of the laundry by the addition of such additives as starch, sours, etc. In the preferred embodiment illustrated in Fig. 1, the neutralizer additives supplied to the Rinse module 19 are provided through an inlet port designated as "NA" (meaning Neutralizer Additive). The neutralizer additive is provided from an appropriate Neutralizer Supply Source 26, and is transmitted to the "NA" input port by means of a pump 27. The pump may be of any configuration well known in the art which is suitable when energized to deliver a known quantity of pumped liquid to its outlet port per given period of pumping time. In the preferred embodiment, the pump is a peristaltic type, as for example manufactured by the assignee hereof, Ecolab Inc., under its DRYMASTER™ Model P pump designation. The pump is controlled by an Automatic Neutralizer Control Circuit, hereinafter described in more detail and generally illustrated at 30, which receives input signals by means of a signal flow path 32 from a pair of sensor probes, positioned within the Rinse module 19 and generally illustrated at 34 in Fig. 1. The control signal from the Automatic Neutralizer Control Circuit 30 to the pump 27 is provided by means of a signal flow path generally designated at 36.
For convenience, the present invention will be described with regard to its applicability in neutralizing the oxidizing agent "chlorine", wherein the chlorine is neutralized by an appropriate "antichlor" additive. It will be understood by those skilled in the art that the invention is not limited to the use of chlorine and antichlor, or to the use of any other particular components which may be described with regard to the Automatic Neutralizer Control Circuit 30 or to the particular sensor probes 34 used herein. Those skilled in the art will readily perceive other components and circuits that could equally well be employed within the spirit and broad scope of this invention.
Referring to Fig. 2, the Automatic Neutralizer Control Circuit 30 is illustrated in functional block diagram form. As used herein, the terminology "signal flow path" will be used to refer to that "course" traversed by signals between functional blocks of a circuit. Such signal flow paths can in reality comprise one or a plurality of actual conductors, connectors and the like. For the sake of continuity in notation, where a plurality of conductors are illustrated in a schematic diagram as forming a signal flow path, the conductors will bear the same reference numeral as the signal flow path, wherein individual conductors thereof will be further designated by subdivisional characters. Further, throughout the ensuing description of electrical components and networks, it will be understood that while not specifically illustrated in the figures, each of the electrical components is properly connected to appropriate supply and ground and bias sources in order to properly operatively energize the respective circuits.
Referring to Fig. 2, the Automatic Neutralizer Control Circuit 30 is illustrated as it would typically functionally appear when connected to neutralize oxidation agents in solution 15 in a container such as a solution carrying laundry container 19ʹ as it might appear during the "Rinse" portion of a laundry cycle. The sensor probe member 34 is operatively disposed within or in relation to the container 19ʹ so as to sense the electrical characteristics of the oxidation agents within the solution 15 to be neutralized. In the preferred embodiment, the sensor probe member 34-comprises a pair of probes 34A and 34B as illustrated in Fig. 2. The probe 34A is, in the preferred embodiment, a platinum electrode suitable for measuring the "oxidation reduction potential" of the solution 15, and the probe 34B comprises a reference electrode. The oxidation reduction potential electrode 34A (hereinafter simplified as the "O.R.P. Electrode" determines the level of oxidizing agents present in the solution 15. In the preferred embodiment, chlorine is the oxidizing agent. The structure and use of such electrodes is well known in the art, and will not be detailed herein. It will be understood that while a platinum O.R.P. Electrode is disclosed with respect to the preferred embodiment, other appropriate probe materials of inert metals as well as other types of sensors for determining the level of oxidizing agents present in the solution 15 could equally well be employed.
The signal output from electrodes 34A and 34B are respectively transmitted by means of signal flow paths 32A and 32B respectively to an Amplifier and Signal Conditioning functional block 37. The reference electrode 34B is connected to and forms the reference potential bus, hereinafter referred to throughout the drawing as 100. The signal output from the Amplifier and Signal Conditioning functional block 37 is applied by means of a signal flow path 38 to one signal input 40a of a Comparator network 40. The output signal from the Amplifier and Signal Conditioning functional block 37 can also be applied to an appropriate Display, generally illustrated at 39. A second input signal is applied to a second input terminal 40b of the comparator 40 from a functional block generally designated as a Set Point Adjustment block 42 by means of a signal flow path 41. The output signal from the Comparator 40 is applied by means of a signal flow path 43 to an Adjustable Pulse Control functional block 44. The signal output from the Adjustable Pulse Control block 44 is carried by means of the signal flow path 36 to energize the Pump 27. The Pump 27 is operative to pump neutralizing agent (in the preferred embodiment "antichlor") from a source of such neutralizing agent 26 which is carried by means of the supply lines 28 and 29 to the Neutralizer Additive (NA) inlet port to the container 19ʹ.
The Amplifier and Signal Conditioning functional block 37 is operative to receive the sensed signal provided by the O.R.P. Electrode 34A and to provide a clean representation thereof to the Comparator network 40. The Amplifier and Signal Conditioning functional block 37 is illustrated in more detail in Fig. 3. Referring thereto, the Reference Electrode 34B is illustrated as being operatively connected to the reference bus 100. The sensed signal output from the O.R.P. Electrode 34A is carried by means of the signal flow path 32A to the noninverting input terminal of an operational amplifier 37.1. The amplifier 37.1 is appropriately connected to positive and negative supply potentials indicated by (+V) and (-V) respectively. While not indicated in the Drawing, it will be understood that the positive and negative supply potentials (+V) and (-V) respectively represent regulated voltage supply buses appropriately connected to an appropriate supply power source. In the preferred embodiment, the supply potentials (+V) and (-V) are (+12 volts) and (-12 volts) respectively.
The inverting input terminal of amplifier 37.1 is connected by means of a resistor 37.2 to the wiper arm of a variable resistor 37.3. The respective ends of variable resistor 37.3 are connected between the positive and negative supply voltages (+V) and (-V) respectively. A feedback resistor 37.4 is connected between the signal output of amplifier 37.1 and its inverting input terminal.
The output terminal of amplifier 37.1 is directly connected to the noninverting input terminal of a second operational amplifier 37.6. The amplifier 37.6 is properly operatively connected to the positive and negative supplies (+V) and (-V) respectively, and has its noninverting input terminal connected by means of a resistor 37.5 to the reference bus 100. A variable resistor 37.7 is connected in series with a fixed resistor 37.8 in the feedback loop between the signal output terminal and the inverting input terminal of amplifier 37.6. A feedback capacitor 37.9 is also connected in the feedback loop of amplifier 37.6, in parallel with resistors 37.7 and 37.8. The output of amplifier 37.6 provides the signal output for the Amplifier and Signal Conditioning functional block 37, and is directly connected to the signal flow path 38.
In the preferred embodiment, the amplifiers 37.1 and 37.6 are type TL 084 operational amplifiers. As with all components described herein with respect to the description of the preferred embodiment of the invention, it will be understood that the invention is not to be construed as limited in any manner by the particular type of circuit components herein described. Rather, such circuit components are merely typical of particular circuit components that have been found to function satisfactorily in the circuit configurations illustrated.
The amplifiers 37.1 and 37.6 function as unity gain amplifiers to condition and stabilize the sensed signal (which can be in the low millivolt range) received from the O.R.P. Electrode 34A. The variable resistor 37.3 "zeros out" imbalances in the sensor electrodes 34. Amplifier 37.6 provides a damping influence to the sensed signal with capacitor 37.9 acting to eliminate signal discrepancies which may appear in the sensed signal as a result of turbulence, bubbles or the like in the solution 15. It should also be noted that the signal flow paths leading from the sensor electrodes 34 to the Amplifier and Signal Conditioning circuits 37 are shielded to eliminate extraneous noise and interference signals.
Referring to Fig. 4, the signal output from the Amplifier and Signal Conditioning circuit 37 is applied by means of the signal flow path 38 to the Comparator network 40. The signal flow path 38 is connected by means of a resistor 40.1 to the inverting input terminal of an operational amplifier 40.2. The noninverting input terminal of amplifier 40.2 is connected to the reference bus 100. A resistor 40.3 and a capacitor 40.4 are connected in parallel in the feedback loop between the signal output and inverting input terminals of amplifier 40.2. The signal output and inverting input terminals of 40.2 also form input terminals 40b1 and 40b2 for connection to receive signals from the signal flow path 41 (see Fig. 2), which will be described in more detail hereinafter. In the preferred embodiment, amplifier 40.2 is a type TL 082 operational amplifier.
The output signal from amplifier 40.2 is directly applied to the inverting input terminal of an operational amplifier 40.5. In the preferred embodiment, amplifier 40.5 is a type LM 311 open collector output comparator amplifier. The positive bias terminal of amplifier 40.5 is connected to the reference bus 100, and its negative bias terminal is connected to the negative bias supply (-V). The emitter of the output transistor of amplifier 40.5 is also connected to the negative bias supply (-V). A resistor 40.6 is connected between the signal output and the noninverting input terminals of amplifier 40.5.
The noninverting input terminal of amplifier 40.5 is also connected to the inverting input terminal of a second open collector output comparator amplifier 40.7 and provides a third input terminal 40b3 for receiving signals from the signal flow path 41 from the Set Point Adjustment functional block 42. In the preferred embodiment, amplifier 40.7 is also a type LM 311 operational amplifier, which has its positive bias terminal connected to the reference bus 100 and its negative bias terminal and the emitter of its output transistor connected to the negative bias supply (-V). The signal output of amplifier 40.5 is connected by means of a resistor 40.8 to the noninverting input terminal of amplifier 40.7. The noninverting input terminal of amplifier 40.7 is also connected by means of a resistor 40.9 to the reference bus 100, and is connected by means of a capacitor 40.10 to the negative bias supply potential (-V). The signal output from amplifier 40.7 is directly applied to the signal flow path 43 for providing an input reset signal to the Adjustable Pulse Control network 44, as hereinafter described in more detail.
The Set Point Adjustment functional block 42 (see Figs. 2 and 4) comprises a plurality of resistors and capacitors that can be adjusted (as hereinafter described) to vary the various signals applied to amplifiers 40.2, 40.5 and 40.7 of the Comparator network 40. Referring to Fig. 4, a plurality of resistors 42.1-42.8 are switchably connected in parallel by means of the conductors 41A and 41B with resistor 40.3 and capacitor 40.4 in the feedback loop of amplifier 40.2, to selectively vary the gain of amplifier 40.2. Each of the resistors 42.1-42.8 is respectively connected in series with a switch 42.11-42.18 which can be selectively opened or closed to connect the desired resistor(s) in parallel in the feedback loop of amplifier 40.2. The switches 42.11-42.18 are, in the preferred embodiment, comprise thumb-wheel switches operatively connected to provide a binary coded two digit decimal number, wherein resistors 42.1-42.4 and their accompanying switches 42.11-42.14 are associated with the "one's digit" of the number, and wherein resistors 42.5-42.8 and their associated switches 42.15-42.18 are associated with the "ten's digit" of the number. The binary coded decimal output designations of the various resistor/switch pairs are indicated to the right of the respective switches in Fig. 5. In the preferred embodiment, the resistor values for resistors 42.1-42.8 are as follows: R42.1 = 1 Megohm; R42.2 = 510 k ohm; R42.3 = 240 k ohm; R42.4 = 120 k ohm; R42.5 = 62 k ohm; R42.6 = 30 k ohm; R42.7 = 15 k ohm; and R42.8 = 6.8 k ohm.
The second portion of the Set Point Adjustment network 42 comprises a resistor/capacitor network that provides in the preferred embodiment, a fixed bias potential to the noninverting input terminal of amplifier 40.5 by means of the conductor 41C through the input terminal 40b3. A capacitor 42.20 is connected in parallel with a resistor 42.21 between the negative bias supply potential (-V) and the conductor 41C. A pair of resistors 42.22 and 42.23 are also connected in parallel between the reference bus 100 and the conductor 41C. In the preferred embodiment, as described in more detail hereinafter, the pair of parallel circuits just described provides a constant 5 volt reference signal to the noninverting input terminal of amplifier 40.5.
The signal output of Comparator 40, is carried by means of the signal flow path 43 to a "reset" input terminal of a Timer circuit 44.1 of the Adjustable Pulse Control network 44. In the preferred embodiment, the Timer 44.1 is a type 555 timer having its V_cc input terminal connected to the reference bus 100 and its reference or (GND) terminal connected to the negative bias supply potential (-V). The timer also has a "threshold" terminal designated as (THD), a "trigger" terminal designated as (TRIG) and a "discharge" terminal designated as (DISCHG). The threshold (THD) and trigger (TRIG) input terminals are commonly connected and are connected by means of a capacitor 44.2. to the negative bias potential (-V). The (THD) and (TRIG) terminals are also connected by means of a variable resistor 44.3 and a fixed resistor 44.4 to the reference bus 100. The movable wiper of variable resistor 44.3 is connected to the discharge (DISCHG) terminal of Timer 44.1, and is also connected by means of a diode 44.5 to the (THD) and (TRIG) terminals.
The signal output of Timer 44.1 is connected by means of a resistor 44.6 to the base of an npn transistor 44.7. The emitter of transistor 44.7 is directly connected to the negative bias potential (-V) and its collector is connected to the cathode of a light emitting diode 44.8. The anode of diode 44.8 is connected to the stationary contact of a switch 44.9. The movable wiper of switch 44.9 moves between a pair of contacts designated at (x1) and (x2) in Fig. 4. Contact (xl) of switch 44.9 is connected by means of a resistor 44.10 to an unregulated power supply source, generally designated at "PS" in Fig. 4, and it is also directly connected to a first input terminal of a triac driver network 44.11. The second contact (x2) of switch 44.9 is connected to a second input terminal of the driver network 44.11. In the preferred embodiment, driver network 44.11 is a type MOC 3030 optically coupled triac driver network. When the movable wiper of switch 44.9 is positioned in engagement with contact (x1), the switch disables the optical coupler driver 44.11. When positioned with movable wiper in engagement with contact (x2), the optical coupler is enabled for operation, upon further conduction of transistor 44.7, as hereinafter described. Driver 44.11 has a first output terminal connected by means of a resistor 44.12 to a first power terminal of a triac 44.13, and closes an enabling supply path for Pump 27 by means of a conductor 36A of signal flow path 36. The second output terminal of the triac Driver 44.11 is connected to the gate terminal of triac 44.13 and is also connected by means of a resistor 44.14 to the second power terminal of triac 44.13, and to a second conductor 36B of the signal flow path 36 leading to the Pump 27. A capacitor 44.15 is connected in series with a resistor 44.16 across the power terminals of triac 44.13 and between the conductors 36A and 36B providing filtering of the triac generated signals.
The circuitry described above enables accurate, automatic neutralization of oxidizing agents in a laundry bath, with practically zero residual neutralizing agent carryover remaining in the bath after the neutralization process. As described above, the Amplifier and Signal Conditioning Network 37 provides a clean sensed signal from the input probes 34 which accurately reflects the measured oxidation reduction potential levels of the solution 15 and which accounts for perturbations within the solution caused by turbulence, bubbles or the like.
For any given pH level of the measured solution 15, there exists a known correlation between the measured oxidation reduction potential value and the actual amount of oxidizing agent (i.e. chlorine in the preferred embodiment) in the solution, which can be directly translated into parts per million (i.e. "ppm") units of the amount of oxidizing agent in the bath. For example, at a given pH level of 10 for the bath 15, a 0.1 millivolt change in the measured oxidation reduction potential level at the probes 34 may represent a change in the level of oxidizing agents in the bath by 1 ppm. Using this correlation factor, a change in the measured oxidation reduction potential level at the probes 34 of 0.5 millivolts would represent a change in the level of oxidizing agents in the bath of 5 ppm. The measured oxidation reduction potential as it correlates to parts per million of the oxidizing agents in the bath varies as a function of the pH level of the bath. For example, in contrast to the above example wherein a pH level of 10 was assumed for the bath 15, if the pH level of the bath 15 were to change to a different level such as to a pH of 9, there would be a corresponding change in the measured oxidation reduction potential level at the probes 34 as well as in the correlation factor of such measured oxidation reduction potential to the actual level of oxidizing agents appearing in the bath. For example, at a bath pH of 9, a 1.0 millivolt change in the measured oxidation reduction potential level at the probes 34 might now represent a change in the level of oxidizing agents in the bath by 1 ppm (in contrast to the 0.1 millivolt per 1 ppm example that existed for a pH level of 10). A typical pH value for a laundry solution in a tunnel washer final rinse stage is between 9 and 11. A typical level of excess chlorine appearing in such bath before neutralization may be on the order of 10 to 50 parts per million.
The measured oxidation reduction potential values as correlated to the amount of oxidizing agents (in ppm) in a bath for any given pH value can be empirically determined. For the embodiment illustrated in the Drawing, the values of the components in the Comparator 40 network and in the Set Point Adjustment 42 network have been selected for use with a tunnel washer apparatus wherein the pH of the solution in the final Rinse module in which the solution is being neutralized, is relatively constant from batch to batch, at a pH level of approximately 9. Therefore, once the Set Point Adjustment selections (as hereinafter described) are made for a desired percentage of neutralization in a given system, such settings do not require change from day to day or from batch to batch as the laundry machine performs successive laundering cycles. However, for a system wherein the pH level of the solution which is being neutralized constantly varies from one laundry cycle to the next, it would be desirable to include a pH monitoring feature for continuously monitoring the pH of the solution 15 being neutralized and for providing a real-time correlation adjustment to the Set Point Adjustment 42 network as well as to the Comparator 40 network circuits which reflect the correlation changes required by the changing pH values. Such real-time correlation function could be readily performed by hardwired circuits or by microprocessor-controlled networks. For ease of description herein, the following discussion will assume a constant pH value for the solution 15 being neutralized.
Given the oxidation reduction potential value for the laundry bath at a "neutral" contition, the gain of amplifier 40.2 can be selected by means of the thumbwheel switches 42.11-42.18 and their associated resistors 42.1-42.8 to provide the desired output operating level from amplifier 40.2 that will be compared against the reference signal applied to comparator amplifiers 40.5 and 40.7. The gain of amplififier 40.2 will be set such that its output voltage at the "neutral" oxidation reduction potential measurement of the bath, identically equals the reference voltage level applied to conductor 41C. In a preferred application of the control network to neutralization of oxidizing agents within the final Rinse module of a tunnel washer (as illustrated in the Drawing), it has been determined that at an operating pH level of 9 (which is typical for solution within the Rinse module), a measured oxidation reduction potential of approximately 400 mv equals the desired zero parts per million of chlorine in the bath 15. Therefore, referring to Fig. 4, the output signal from amplifier 40.2 should equal the value of the reference signal applied by means of the conductor 41C to the comparator amplifiers 40.5 and 40.7, at such zero ppm level. In the preferred embodiment, a constant reference voltage level (appearing on conductor 41C) of 5 volts has been selected as an optimum operating level for the comparator amplifiers 40.5 and 40.7. Therefore, at an actual measured oxidation reduction potential level of 400 mv by the probes 34, the signal output of amplifier 40.2 should also be 5 volts, by proper selection of the nominal gain of the amplifier 40.2 with the resistor/switching network. Any deviation from the measured "neutral" oxidation reduction potential value of 400 mv measured at the probes 34 represents an undesirable excess of chlorine in the solution, or conversely an excess of antichlor in the solution.
The amplification level of the measured deviations from the neutral 400 mv level are multiplied by the gain selection entered into the Set Point Adjustment 42 network by means of the resistors 42.1-42.8 and their associated switches 42.11-42.18. For simplicity in setting of the gain of amplifier 40.2, the resistor 42.1-42.8 values have been selected such that their binary coded decimal representations set by switches 42.11-42.18 indicate a multiple of the "neutral" millivolt value of the oxidation reduction potential measurement of the solution. For example a switch selection reading of "01" would correspond to a "neutral" reading of 10 mv, a reading of "13" to a "neutral" reading of 130 mv, etc.; wherein the output voltage from amplifier 40.2 at the respective "neutral" gain settings would be 5 volts, to match the selected reference voltage level of the preferred embodiment circuit configuraiton.
For the tunnel washing application described herein, it is known that a typical chlorine content within the solution 15 which is to be neutralized at the final Rinse station can typically vary from 10 to 50 parts per million. It is desirable to reduce such residual chlorine content to as near zero ppm as possible, without introducing excessive or residual antichlor to the solution which can be as undesirable as the chlorine itself. The Automatic Neutralizer Control Circuit 30 operates in closed loop manner to add antichlor to the rinse solution 15 in measured increments by operating the Pump 27 on a pulsed basis, in response to the actual measured oxidation reduction potential value by the probes 34. The determination as to whether antichlor injection to the solution 15 is necessary, is made by the Comparator network 40.
Referring to Fig. 4, the comparator amplifier 40.5 continuously monitors the measured oxidation reduction potential signal provided by amplifier 40.2 against the fixed reference level on conductor 41C established by the reference potential circuit of the Set Point Adjustment network 42. If the measured oxidation reduction potential signal exceeds the fixed reference signal at the input to amplifier 40.5, an output signal is provided by comparator amplifier 40.5 to the noninverting input of comparator amplifier 40.7. Since the noninverting input of amplifier 40.7 is connected to the RC network established by resistor 40.9 and capacitor 40.10, comparator amplifier 40.7 acts as a "delay" comparator which ensures that the signal received from amplifier 40.2 must exceed the fixed reference level on conductor 41C for at least a continuous predetermined period of time before the comparator network 40 will provide a reset signal to Timer 44.1. In the preferred embodiment, the "delay" function has been set for a turn-on delay of 2 seconds and a turn-off delay of 0.1 seconds. The turn-on delay is established by the charging time constant of capacitor 40.10. The turn-off delay is provided by discharge of capacitor 40.10 through resistor 40.8 and the open collector output terminal of amplifier 40.5 to the negative bias supply bus (-V). Therefore, whenever the probes 34 measure a differential oxidation reduction potential value differing from the "neutral" value for a continuous time period of 2 seconds, the comparator network 40 provides a logical "high" reset signal to the "reset" input terminal of Timer network 44.1.
Timer 44.1 is operative to establish a pulsed duty cycle for activating the Pump 27 so as to inject a predetermined amount of antichlor into the solution bath 15 on each energized cycle of the Pump. In the preferred embodiment, the Timer 44.1 takes approximately 20 seconds to charge following receipt of a reset signal from the comparator 40, and approximately 1 second to discharge before it can be reset again by the comparator 40. The capacitor 44.2 of Timer 44.1 is charged by the circuit path established from the reference 100, through resistor 44.4, the left portion of resistor 44.3 (as viewed in Fig. 4), and the diode 44.5. Once capacitor 44.2 is charged, the signal output of Timer 44.1 switches to a logical "high", and its (DISCHG) terminal switches to a logical "low" enabling capacitor 44.2 to discharge through the right portion of resistor 44.3 and the (DISCHG) terminal. When the timer is triggered by the charged capacitor 44.2, the "high" output signal from the output of Timer 44.1 drives transistor 44.7 into conduction, triggering triac driver 44.11 which enables triac 44.14 for the duration of the enabling pulse from Timer 44.1. Following discharge of capacitor 44.2 and resumption of the output of Timer 44.1 to a logical "low" the pump is disabled for the remainder of the time during which triac 44.13 is enabled. When enabled Pump 27 operates to inject a measured amount of antichlor additive to the solution bath 15. In the preferred embodiment, an injection of antichlor to the solution bath 15 during one pulsed interval of pump operation operates to reduce the measured oxidation reduction potential by approximately 2-3 millivolts. For a bath having a Ph of 9, wherein the "neutral" oxidation reduction potential value of the bath is approximately 400 mv, a change in 1.0 mv has been found to correlate to approximately a 1 ppm change in the presence of unreduced oxidizing agents in the bath.
The above periodic injection process is continually repeated until the oxidation reduction potential difference measured by the probes 34 from the desired "neutral" level is insufficient to provide an adequate signal to activate comparators 40.5 and 40.7. Under such conditions, the Timer 44.1 will be disabled, as well as the output drive circuitry for energizing the Pump 27. Experiments using the above described Automatic Neutralizer Control Circuit 30 have demonstrated ability of the network to repeatably neutralize excessive chlorine in the rinse solution to a level of less than 1 ppm with less than 1 ppm of residual antichlor remaining in the bath 15 after the neutralization process. This can be contrasted with prior art "timed feed" methods of neutralization which would typically consider a residual amount of antichlor in the bath of from 8 to 15 ppm to be very acceptable. It can be appreciated, therefore, that the present invention provides an accurate method of controlling both the levels of residual neutralization and oxidation agents remaing in a bath following a neutralization process during execution of the normal laundry wash formula
While a particular embodiment of the invention has been described with respect to its application with a continuous tunnel washing system for neutralizing the oxidation agents in the final rinse portion thereof, it will be understood by those skilled in the art that the invention is not limited to such application or to the particular circuits disclosed and described herein. It will be appreciated by those skilled in the art that other circuit configurations that embody the principles of this invention and other applications therefor other than as described herein can be configured within the spirit and intent of this invention. The circuit configurations described herein were provided only as an example of one embodiment that incorporates and practices the principles of the present invention. Other modifications and alterations not only of the circuit configurations but also of the components therein and the application of the overall control circuit to the controlled reduction of oxidation agents in solution are well within the knowledge of those skilled in the art and are to be included within the broad scope of the appended claims.

Claims

1. A method of neutralizing oxidation agents in a laundry bath, comprising:

(a) determining the amount of an oxidizing agent to be neutralized that is present in a laundry bath at any particular instant of time, and providing a sensed signal in response thereto;

(b) injecting a measured amount of a neutralizing agent of a type capable of reducing said oxidizing agent into the bath in response to said sensed signal;

(c) terminating said injection of said neutralizer agent into the bath when said sensed signal indicates that the amount of said oxidizing agent to be neutralized remaining in the bath is less than 5 parts per million.

2. The method as recited in Claim 1 further including terminating said injection of said neutralizer agent into the bath when said sensed signal indicates that the amount of said oxidizing agent to be neutralized remaining in the bath is less than 2 parts per million.

3. The method as recited in Claim 1 further including the step of terminating said injection of said neutralizer agent into the bath when said sensed signal indicates that there remains no said oxidizing agent to be neutralized in the bath.

4. The method as recited in Claim 1, wherein the step of terminating said injection further includes terminating said injection of said neutralizer agent into the bath before excess unreduced said neutralizing agent in the bath exceeds 10 parts per million.

5. The method as recited in Claim 4, wherein said injection step is terminated before excess unreduced said neutralizing agent in the bath exceeds 5 parts per million.

6. The method as recited in Claim 5, wherein said injection of said neutralizer agent into the bath is terminated when said sensed signal indicates that the amount of said oxidizing agent to be neutralized remaining in the bath is less than 1 part per million and before excess unreduced said neutralizing agent in the bath exceeds 2 parts per million.

7. The method as recited in Claim 1, wherein the step of determining the amount of said oxidizing agent to be neutralized comprises the step of measuring the oxidation reduction potential in said bath and subtracting therefrom a predetermined oxidation reduction potential value of a like bath containing none of said oxidizing agent.

8. The method as recited in Claim 7 including the step of averaging the instantaneously measured oxidation reduction potential signal over a period of time and providing said sensed signal in response to said averaged signal.

9. The method as recited in Claim 1, wherein said injection step comprises energizing an injection pump that is operatively connected to deliver said neutralizing agent to said bath, on an intermittent, periodic basis.

10. The method as recited in Claim 9, wherein the duty cycle of said periodic injection is less than about 20%.

11. The method as recited in Claim 1, wherein said bath solution has a relatively constant pH.

12. The method as recited in Claim 7, wherein each of said injections reduces the measured oxidation reduction potential of said bath by about 1 to 5 parts per million.

13. The method as recited in Claim 1, wherein said oxidizing agent comprises active chlorine and wherein said neutralizer agent comprises an antichlor agent.

14. A method of automatically neutralizing an oxidation agent in a laundry bath, comprising the steps of:

(a) quantitatively sensing the presence of an oxidizing agent to be neutralized, in said bath and providing a sensed signal in response thereto indicative of the amount of said oxidizing agent in said bath;

(b) selecting a maximum acceptable threshold level for said oxidizing agent in said bath and producing a threshold signal indicative thereof;

(c) comparing said sensed and said threshold signals and producing a comparison signal in response thereto;

(d) injecting a neutralizing agent of a type suitable for reducing said oxidizing agent into said bath in response to said comparison signal; and

(e) terminating said adding of the neutralizing agent to said bath when the unneutralized said oxidizing agent remaining in said bath is less than said maximum acceptable threshold level.

15. An apparatus for automatically neutralizing oxidation agents in a laundry bath comprising:

(a) means for determining the amount of an oxidizing agent to be neutralized that is present in a laundry bath at an particular instant of time, and for providing a sensed signal in response thereto;

(b) means operatively connected to receive said sensed signal for injecting a measured amount of a neutralizing agent of a type capable of reducing said oxidizing agent, into the bath in response to said sensed signal; and

(c) means operatively connected to receive said sensed signal for terminating said injection of said neutralizing agent into the bath when said sensed signal indicates that the amount of said oxidizing agent to be neutralized remaining in the bath is less than about 5 parts per million.

16. The apparatus as recited in Claim 31, further including means operatively connected to receive said sensed signal, for terminating said injection of said neutralizing agent into the bath before excess unreduced said neutralizing agent in the bath exceeds 10 parts per million.

17. The apparatus as recited in Claim 32, wherein said means for terminating the injection of said neutralizing agent into the bath is operable to terminate said injection when said sensed signal indicates that the amount of said oxidizing agent to be neutralized remaining in the bath is less than about 1 part per million and before excess unreduced said neutralizing agent in the bath exceeds about 5 parts per million.

18. A laundry machine of a type suitable for laundering a textile, comprising:

(a) a rinse compartment suitable for containing a bath solution for rinsing said textile; and

(b) automatic neutralizing apparatus as set forth in Claim 31, operatively connected with said rinse compartment.