CA2172723C - Method of dosing detergent product - Google Patents

Method of dosing detergent product

Info

Publication number
CA2172723C
CA2172723C CA002172723A CA2172723A CA2172723C CA 2172723 C CA2172723 C CA 2172723C CA 002172723 A CA002172723 A CA 002172723A CA 2172723 A CA2172723 A CA 2172723A CA 2172723 C CA2172723 C CA 2172723C
Authority
CA
Canada
Prior art keywords
detergent
conductivity
washing solution
measured
detergent product
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
CA002172723A
Other languages
French (fr)
Other versions
CA2172723A1 (en
Inventor
Wilhelmus Klaas Der Kinderen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Diversey Inc
Original Assignee
Unilever PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Unilever PLC filed Critical Unilever PLC
Publication of CA2172723A1 publication Critical patent/CA2172723A1/en
Application granted granted Critical
Publication of CA2172723C publication Critical patent/CA2172723C/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F34/00Details of control systems for washing machines, washer-dryers or laundry dryers
    • D06F34/14Arrangements for detecting or measuring specific parameters
    • D06F34/22Condition of the washing liquid, e.g. turbidity
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F2103/00Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
    • D06F2103/20Washing liquid condition, e.g. turbidity
    • D06F2103/22Content of detergent or additives
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F2105/00Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
    • D06F2105/42Detergent or additive supply
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F2105/00Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
    • D06F2105/58Indications or alarms to the control system or to the user
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06FLAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F2105/00Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
    • D06F2105/58Indications or alarms to the control system or to the user
    • D06F2105/60Audible signals

Landscapes

  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Washing And Drying Of Tableware (AREA)
  • Control Of Washing Machine And Dryer (AREA)
  • Detergent Compositions (AREA)

Abstract

A method is provided of dosing detergent product into a washing solution present in an industrial washing machine, comprising measuring, from a washing solution containing water and detergent material, a property which is proportional to the detergent concentration of said washing solution, and adding detergent product to the washing solution if the value of the measured property corresponds to a detergent concentration below a preset threshold value, whereby the measured property is the electroconductivity of the washing solution, said property being measured using a measuring cell including one or more electrodes (3, 4) characterised by the steps of: (a) dosing, during filling of the washing machine with clean water, a sufficient amount of detergent product so as to attain present threshold value, followed by mixing of said dosed tetergent product with the water; (b) measuring the conductivity of the thus obtained wash liquor, after a mixing time of less than 2 minutes; and (c) storing said measured conductivity and the detergent concentration value corresponding thereto, as the preset threshold values, in the memory (3) of a controller (1), which is attached to the measuring cell and controls the dosing of detergent product as a function of the conductivity measured.

Description

WO95/12704 PCT~P94103493 ~) ~A21 72723 METHOD OF DOSING DETERGENT PRODUCT

FIELD OF THE INVENTION

The present invention relates to a method of dosing deter-gent product into a washing solution present in an in-dustrial washing machine, in particular an institutional mechanical ware washing machine.

BACKGROUND OF THE INVENTION

lo In prior art washing systems, the detergent concentration of the washing solution is usually observed by measuring the electroconductivity of the washing solution between at least two electric electrodes immersed in the washing solution.
15 In this respect, electroconductivity can be simply defined as the ability of a solution to pass an electrical current.
In a conventional conductivity sensor contact to the solution is made by two or more electrodes, and a small alternating current is passed between them. This current is 20 related to the solution conductivity.

The conductivity measurement is generally carried out by means of the above-described electrodes and a conductivity amplifier which activates a detergent dosing pump whenever 25 the electroconductivity of the washing solution (and, as a consequence, the detergent concentration) drops below a predetermined threshold value, until the theshold level has been regained. Since the conductivity amplifier may operate up to a high accuracy, it can be ensured under all cir-30 cumstances that the detergent concentration and washingeffect are sufficient, i.e. that the detergent con-' centration remains constantly above a predeterminede level.

WO95/12704 PCT~P94/03493 ( 2 ~A21 7~723 However, it has been observed that the detergent con-centration in prior art washing systems usually exceeds considerably the threshold level yielding complete clean-ness. This over-dosage of detergent product may amount to 5 tens of percents, thus causing considerable extrG operating costs.

In GB-A-2,217,050, this problem related to the usually applied overdosage of detergent material, has been recog-10 nised. Consequently, this document discloses a method forreducing this overdosage, wherein the detergent product is periodically added in small dosages and allowed to mix with and dissolve in the washing solution for a pre-d~termined period of time after each dosage, thus ensuring that no 15 undissolved detergent material affecting the mea-uring result is left in the washing solution at the st~rt of the next dosing period, and that the conductivity then measured very accurately corresponds to the actual detergent con-centration of the washing solution.
It is known that systems for controlling the detergent concentration in a washing solution, in which a pair of electrodes immersed in the washing solution are used, pos-sess shortcomings. For example, the electrodes present in 25 the measuring cell are subject to scumming. That is, the electrodes may be coated by a film when they are used to monitor a hard water solution, and, as a result, an accep-table conductivity level may be indicated when in fact the conductivity, and therefore the detergent concentration of 30 the washing solution, is unacceptably high. Furthermore, food soil in the washing solution is likely to cause con-tamination of the electrodes which may have a detrimental effect on the accuracy of the conductivity measurlement.
Finally, the electrodes have been found to be senlsitive to 35 scale build-up resulting in erroneous measurements and, as WO95/12704 PCT~P94J03493 .
a consequence, increasing product consumption and operating costs.

Since the mentioned conditions leading to erroneous 5 measurements (i.e. scumming, cont~min~tion and scale build-up) occur at the interface between washing solution and electrode, so-called inductive measuring systems comprising electrodeless conductivity measuring sensors have been developed. The type of sensor applied in these inductive 10 systems usually comprises two toroidally wound coils, and when these sensors are immersed in the washing solution to be monitored, said solution provides an electrical coupling between the coils.
US-A-4,733,798 discloses an apparatus for controlling the 15 concentration of a washing solution, wherein the conduc-tivity of said solution is measured using an inductive measuring system comprising an electrodeless sensor.

However, the commercially available inductive measuring 20 systems suitable for monitoring the electroconductivity and thus the detergent concentration of the washing soluton, are up till now extremely expensive. Furthermore, con-tamination of the coils with food soil can prevent the prolonged establishment of a homogeneous distribution of 25 the detergent product in the washing solution, particularly near the coils. Other drawbacks of inductive measuring systems are the following:
(i) in view of the inductive measuring technique, a certain minimum distance between the coils and the internal wall of 30 the container for holding the washing solution to be monitored, is required. So, this measuring technique is not applicable in containers or pipes of reduced size;
(ii) because the signal produced in the coils is weak, the length of the cables between coils and conductivity 35 amplifier needs to be restricted.

C 7352 ( V) ~ r C1~21 72723 It is, therefore, an object of the present invention to provide a method for controlling the detergent con-centration of a washing solution, whereby a cheap and simple measuring system is applied and which does not have 5 the above drawbacks. It is also an object of the invention to provide a method for controlling the detergent con-centration of a washing solution, whereby the detergent consumption is minimised and a constant cleaning perfor-mance is achieved.

It has now surprisingly been found that these and other objects can be accomplished by carrying out the method of the present invention, whereby the conductivity of the 15 washing solution to be monitored is measured with a measuring cell containing electrodes.

DEFINITION OF THE INVENTION
The present invention provides a method of dosing detergent 20 product into a washing solution present in an indust~ial ,Q ~ c~ trY
washing machine, comprising measuring,L~cm~a washing solution containing water and detergent material, ~ ~ o~CL-CGr~ L~tj~
~y uhia~ i~ proportional to the detergent concentration of said washing solution, and adding detergent produ~t to th~
~ t~v.4 25 washing solution if the value of the measured ~op~t~
~*~ h~ Q~ wh~-~corresponds t~ o dctcrgc..t ~o.~cc..~l~Lio~. Lcl~ a preset ~ c ~ S~c,~ ~;~L i~ SC~ _ threshold~value~ ~h _rcby thc ~ca~urcd propcrty i~ th~3 ~lcatroconductivity of L~ washing solution, ~aid propcrt~
bcing ,..c~urcd ¦using a measuring cell including 1 or more¦
30 ¦electrodes,¦characterised by the steps of:
(a) dosing, during ~ l ~g of the washing machine with clean water, a ~ufficicnt amount Qf detergent product so as to attain said preset thresh~old~value, followed by mixing of said dosed detergent product with the water;

~ AMENDED SHEET

C 7352(V) - . . ...
CA~l 72723 (b) measuring the conductivity of the thus obtained wash liquor, after a mixing time of less than 2 minutes; and (c) storing said measured conductivity ~nd thc dctcrgcntJ
~onccntratio~. v~lu~ eo lc~ g Lhe~e~ as the prc3ct 5 threshold~varue~, in the memory of a controller, which is attached to the measuring cçll and contr~l~s the dosing of In.~QS~I~
detergent product as a function of the~conductivity, c ~ G u r ~ d,~
~~,~

As a result of the method according to the present inven-tion, the problems related to the use of electrodes are largely overcome. This is achieved by measuring the conduc-tivity of the wash solution in the b~g~nning of a washing 15 cycle for obtaining a preset threshold~va~ue Lf.~ the deter-gent concentration of the solution.
As a consequence of the early measurement of the conduc-tivity, contamination, scale buildup and scumming of the electrodes which has accumulated during the previous 20 washing cycles, cannot negatively influence the detergent concentration control of the washing solution. This ac-cumulation of fouling of the electrodes may stretch out over a period of months depending on the frequency of service intervals of the installation concerned.
As a result of the method of the invention, a constant detergent concentration throughout the operating life of the electrodes and at a minimised detergent consumption could be attained. Further advantages of the method of the 30 invention are guaranteed constant cleaning performance using a relatively cheap system including measurement cells containing one or more electrodes, and improved reliability resulting in a reduced number of service calls. Further-more, the applied system is usually fully automatised.

AMENDED SHEET

WO9S/l2704 PCT~P94/03493 6 ~A2~-12723 In order to reduce hardware and installation costs, a measuring cell containing only one electrode is preferably applied. In that case, the other "counter" electrode is constituted by the internal wall of the container holding 5 the washing solution to be monitored.

It is desirable that the mixing time before the conduc-tivity is measured, is as short as possible.
When the method of the invention is applied for monitoring 10 the detergent concentration in washing solutions in multi-tank ware washing machines, this mixing time is generally less than 2 minutes, preferably less than 1 minute.
Alternatively, when the method of the invention s applied for monitoring the detergent concentration in wa~hing 15 solutions in single tank ware washing machines, this mixing time is generally less than 1 minute, preferably less than 30 seconds, a mixing time of from 5 to 15 second~ being pre-ferred.

20 For obtaining optimal detergent consumption, the steps according to the present invention are preferably repeated every time the washing machine is filled with clean water.
For dosing the correct amount of detergent product when filling the washing machine with clean water, it is 25 desirable to calculate this amount by determining the internal water volume of the washing machine to be applied.
The method of the invention turned out to be particularly suitable for controlling the detergent concentration of washing solutions present in institutional ware washing 30 machines.

In the method of the invention, an alarm function can be included, indicating that the electrodes applied have been contaminated to such extent and that, consequent y, their C 7~52(V) ' " . :

7 ~A2 1 72723 sensitivity has deteriorated so much, that suitable operation of these electrodes is not possible anymore.
This alarm function is usually adjustable such that it gives a visual or audible signal when the sensitivity of 5 the electrodes has reduced to a level in the range of 50-70 % of the sensitivity value at the start of their operating life. The specific adjustment of the alarm function depends on the accuracy of the concentration control required: when a higher accuracy is required the alarm will be adjusted to 10 a higher percentage of the initial sensitivity. In other words: in that case, less fouling of the electrodes will be tolerated.

The invention will now be further explained by way of the 15 following preferred embodiment and with reference to the accompanying drawing in which figure 1 schematically il-lustrates a system for carrying out the method of the invention.

20 This figure shows a block diagram of this system, including a conductivity amplifier/controller (1) which is connected to measuring electrodes (3) and (4), one of which may be the internal wall of a container holding a washing solution to be monitored by said system.. These electrodes are 25 immersed in the washing solution at a suitable location.
This location is not critical; however, a measuring point positioned close to the detergent feeding point detects the effect of fed detergent product more rapidly. The conduc-tivity amplifier/controller (1) measures the electroconduc-30 tivity of the washing solution between the measuringelectrodes (3) and (4) and generates at its output an ac-tivating signal (AKT) whe~ the measured conductivity drops below a preset threshold~value. This preset value is measured during the beginning of the wash cycle, and subse-35 quently stored in the memory (3).

AM~NûtD S~I~E~

735~ (V) I ,, r 8 C~l2 1 72723 The-output of the conductivity amplifier/controller (1) is connected to a control input of a control unit (2) for a detergent dosing pump. This control unit (2) switches on the dosing pump only if the signal AKT is generated.
The invention is illustrated by way of the following non-limiting Examples.

Examples 1, 2, 3, ComParative Examples A, B, C
10 A detergent product having the following composition was tested in an industrial mechanical dishwashing machine containing a measuring cell including a pair of conduc-tivity electrodes:

15 Component Parts bv weiqht Sodium hydroxide (50%) 35.5 Bayhibit AM (1) 3.0 Norasol LMW 4S N (2) 3.0 Demineralised water 58.8 wherein :
(1) Bayhibit AM : Phosphono-1,2,4-butane-tricarboxylic acid (50~), ex Bayer (2) Norasol LMW 45 N : Sodium salt of polyacrylic acid, ex Norsohaas.

First, three mechanical dishwashing cycles were carried out with a clean conductivity probe at various dosing leve~ls, to obtain an indicated detergent product level of respec-30 tively 1.5 g/l, 2.0 g/l, and 3.5 g/l. Subsequently, at eachof these dosing levels two mechanical dishwashing cycles were carried out with a scaled cotnductivity probe: one ~ c~ lV~;
cycle whereby a pre-set threshold~value according to the method of the present invention Was used, and a ~e~ond 35 comparative cycle whereby said p~e-set threshold~va~ue was A,~1~1YDEd SHEE~

WO 9S/12704 PCT~P94103493 .

not used. In other words: during the mechanical dishwashing cycles according to the invention the scaling effect of the probe was compensated, whereas said compensation was not carried out during the comparative cycles. During all 5 dishwashing cycles, the actual detergent level in the wash liquor was measured.
The following actual product concentrations in the mechanical dishwashing liquors (in g/l) were found:

10 ExamPle 1 A
Indicated detergent CleanScaled probe product level probeCompensated Uncompensted 1.5 g/l 1.5 1.5 2.2 15 ExamPle 2 B
Indicated detergent CleanScaled probe product level probeCompensated Uncompensted 2.0 g/l 2.0 2.0 2.8 20 ExamPle 3 C
Indicated detergent CleanScaled probe product level probeCompensated Uncompensted 3.5 g/l 3.S 3.5 4.3 It can be noted that at all dosing levels tested more detergent product was actually applied than indicated, when uncompensated scaled conductivity probes were used. On the other hand, the actual detergent product concentration in 30 the wash liquor was found to be equal to the indicated product level when compensated scaled probes were applied.

Claims (7)

1. A method of dosing detergent product into a washing solution present in an industrial washing machine, comprising measuring, using a measuring cell including one or more electrodes, the conductivity of a washing solution containing water and detergent material, said conductivity being proportional to the detergent concentration of said washing solution, and adding detergent product to the washing solution if the value of the measured conductivity falls below a threshold conductivity value which corresponds to a preset threshold concentration value of said detergent material in said washing solution, characterised by the steps of:
(a) dosing, during filling of the washing machine with clean water, a pre-calculated amount of detergent product so as to attain said preset threshold concentration value, followed by mixing of said dosed detergent product with the water;
(b) measuring the conductivity of the thus obtained wash liquor, after a mixing time of less than 2 minute; and (c) storing said measured conductivity as the said threshold conductivity value, in the memory of a controller, which is attached to the measuring cell and controls the dosing of detergent product as a function of the measured conductivity.
2. The method according to claim 1, wherein the measuring cell contains 2 electrodes.
3. The method according to claim 1 or 2, wherein the conductivity of the wash liquor is measured after a mixing time of less than 1 minute.
4. The method according to any of the preceding claims, wherein the steps mentioned in claim 1 are repeated whenever the washing machine is filled with clean water.
5. The method according to any of the preceding claims, wherein the amount of detergent product to be dosed for obtaining the preset threshhold concentration value is calculated by determining the internal water volume of the washing machine.
6. The method according to any of the preceding claims, whereby said method is carried out in an industrial ware washing machine.
7. The method according to any of the preceding claims, wherein an alarm element is applied which indicates when the sensitivity of the electrodes has reduced to a level in the range of 50-70% of the sensitivity at the start of their oparting life.
CA002172723A 1993-11-02 1994-10-24 Method of dosing detergent product Expired - Lifetime CA2172723C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP93203065 1993-11-02
EP93203065.3 1993-11-02

Publications (2)

Publication Number Publication Date
CA2172723A1 CA2172723A1 (en) 1995-05-11
CA2172723C true CA2172723C (en) 1997-11-25

Family

ID=8214155

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002172723A Expired - Lifetime CA2172723C (en) 1993-11-02 1994-10-24 Method of dosing detergent product

Country Status (9)

Country Link
EP (1) EP0726978B1 (en)
AU (1) AU679281B2 (en)
BR (1) BR9407967A (en)
CA (1) CA2172723C (en)
DE (1) DE69413246T2 (en)
ES (1) ES2123161T3 (en)
FI (1) FI108866B (en)
WO (1) WO1995012704A1 (en)
ZA (1) ZA948468B (en)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19938010A1 (en) * 1999-08-11 2001-02-15 Bsh Bosch Siemens Hausgeraete Process for controlling, regulating and documenting a cleaning process
US6958693B2 (en) 2002-05-24 2005-10-25 Procter & Gamble Company Sensor device and methods for using same
EP1639176B1 (en) * 2003-05-28 2013-07-10 LG Electronics Inc. A control method of a washing machine
ES2619421T3 (en) * 2003-05-28 2017-06-26 Lg Electronics, Inc. Washing machine control method
US7571734B2 (en) 2005-01-20 2009-08-11 General Electric Company Fluid dispensing system for a washing device
US7581437B2 (en) 2006-04-07 2009-09-01 Masco Corporation Level sensor for granules in water
US7802335B2 (en) 2007-10-12 2010-09-28 General Electric Company Bulk dispense user adjustable controls
US8056374B2 (en) 2007-10-12 2011-11-15 General Electric Company Multiple compartments wash additives auto-dispenser in washer or dryer pedestal
US8056747B2 (en) 2007-10-12 2011-11-15 General Electric Company Removable tank for laundry bulk dispenser system
US8388695B2 (en) 2008-07-01 2013-03-05 Whirlpool Corporation Apparatus and method for controlling laundering cycle by sensing wash aid concentration
US8266748B2 (en) 2008-07-01 2012-09-18 Whirlpool Corporation Apparatus and method for controlling bulk dispensing of wash aid by sensing wash aid concentration
EP2791410B1 (en) * 2011-12-14 2018-07-11 Ecolab USA Inc. Optimized dosing procedure for a washing machine

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Publication number Priority date Publication date Assignee Title
US3645669A (en) * 1969-02-28 1972-02-29 Gerhard Rausch Method and arrangement for testing the liquid in washing machines
FI773869A (en) * 1977-12-20 1979-06-21 Asko Upo Oy FOERFARANDE OCH ANORDNING FOER STYRNING AV SKOELJNINGEN I EN TVAETTMASKIN
US4733798A (en) * 1986-02-05 1988-03-29 Ecolab Inc. Method and apparatus for controlling the concentration of a chemical solution
FI80729C (en) * 1988-04-07 1990-07-10 Vesa Hakulinen FOERFARANDE OCH ANORDNING FOER DOSERING AV TVAETTMEDEL.
KR920018284A (en) * 1991-03-29 1992-10-21 가나이 쓰도무 washer

Also Published As

Publication number Publication date
FI108866B (en) 2002-04-15
FI961837A (en) 1996-04-30
CA2172723A1 (en) 1995-05-11
ZA948468B (en) 1996-04-29
EP0726978B1 (en) 1998-09-09
AU679281B2 (en) 1997-06-26
DE69413246D1 (en) 1998-10-15
BR9407967A (en) 1996-12-03
AU8059994A (en) 1995-05-23
ES2123161T3 (en) 1999-01-01
DE69413246T2 (en) 1999-02-18
FI961837A0 (en) 1996-04-30
EP0726978A1 (en) 1996-08-21
WO1995012704A1 (en) 1995-05-11

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