Optimized dosing procedure for a washing machine

Abstract

The present invention relates to a method of controlling a dispenser for dosing a product in a washing machine leading to an optimized dosing result, a dispenser controller programmed with an algorithm to execute the method of the present invention as well as to the use of said dispenser for controlling dosing of a product in a washing machine.

Claims

1. A method of controlling a dispenser for dosing a detergent in a washing machine comprising: (a) providing a washing machine comprising measuring means for measuring at least one parameter (c*) corresponding to the concentration of a detergent in a solution present in at least part of said washing machine, a dispenser to dispense said detergent, said dispenser being equipped with a reversibly closable output device having a minimum opening time (t.sub.min) the dispenser has to be opened, and a dispenser controller coupled to said measuring means and said dispenser, including at least one processor and at least one non-volatile memory for recording, calculating, controlling and/or storing process parameters; (b) measuring, after an initial mixing and/or waiting time, at least one said parameter (c*) to determine the current concentration of the detergent in the machine (c*.sub.cur); (c) calculating the difference (c*) between the setpoint (c*.sub.set) and the current concentration in the machine (c*.sub.cur); (d) calculating and storing a current feed rate per minimum opening time (dc*/t.sub.min) based on an average feed rate per minimum opening time determined from a plurality of a number (n) of prior dispensing events; (e) initiating dispensing of said detergent to said machine by opening said reversibly closable output devise for a dosing time (t.sub.dos) resulting from the ratio (c*/(dc*/t.sub.min)) of the difference between the set point and the current concentration (c*) to the current feed rate per minimum opening time (dc*/t.sub.min); and wherein dispensing is initiated if (c*.sub.cur) is more than x.sub.1 below the setpoint (c*.sub.set); and wherein dispensing is initiated if (c*.sub.cur) is in the range of from (100%x.sub.1) of the setpoint (c*.sub.set) to below 100% of the setpoint (c*.sub.set) and the sum (c*.sub.cur+c*) of the current concentration (c*.sub.cur) and the difference between the setpoint and the current concentration (c*) does not exceed (100%+x.sub.2) of the setpoint (c*.sub.set); and wherein x.sub.1 is 0<x.sub.125% and x.sub.2 is 0<x.sub.240%; and wherein the minimum opening time (t.sub.min) is from about 0.25 seconds (s) to about 1 second.

2. The method according to claim 1, wherein x.sub.1 is 0<x.sub.120%, and x.sub.2 is 0<x.sub.230%.

3. The method according to claim 1, wherein said washing machine comprises a, a single tank dishwashing machine, and/or an institutional single tank dishwashing machine.

4. The method according to claim 1, wherein the at least one parameter (c*) corresponding to the concentration of the detergent is the conductivity of the washing liquor.

5. The method according to claim 1, wherein the at least one parameter (c*) corresponding to the concentration of the detergent is measured in the wash tank of said machine.

6. The method according to claim 1, wherein said reversibly closable output device comprises at least one valve.

7. The method according to claim 6, wherein at least one valve is a solenoid valve.

8. The method according to claim 1, wherein the number (n) of the at least two of the last number (n) of dispensing events used for calculating the moving average is from 3 to 10.

9. The method according to claim 1, wherein the detergent comprises a liquid dishwashing detergent, and/or a solid dishwashing detergent in the form of a bar, a brick or a block.

10. The method according to claim 1, wherein the method further comprises a step (f) wherein no detergent is dispensed for an additional mixing and/or waiting time, and optionally followed by a further dispensing cycle comprising at least steps (a) to (e).

11. The method according to claim 1, wherein one complete washing event including all method steps lasts from about 25 seconds to about 2 hours (h).

12. The method according to claim 1, wherein the mixing and/or waiting time in step (b) independently lasts from about 1 second to 5 minutes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of an exemplary single tank dishwashing machine with a spray arm (1) comprising a plurality of nozzles, through which washing liquor can be sprayed onto the dishes (2). The used washing liquor draining from the dishes runs over a run-off plate (4) into a wash tank (5). The machine furthermore comprises a dispenser (3), from which the detergent product is dispensed into the dishwasher over the run-off plate (4) into the wash tank (5). At the bottom of the wash tank a sensor (6) is installed for measuring a parameter c*, corresponding to the concentration of the detergent product in the washing liquor, for example a conductivity sensor. A circulating pump (7) circulates the washing liquor from the wash tank (5) to the spray arm (1).

(2) FIG. 2 is a flow chart illustrating the principle dosing algorithm the dispenser controller is programmed with in order to carry out the method of the present invention.

(3) FIG. 3 shows a comparison of different dosing principles. Three different procedures were used to dispense detergent in a dishwasher. The final detergent concentration reached by each procedure is given relative to the setpoint. Each measurement was repeated two times, as shown by the black and white bars, respectively.

EXAMPLES

Example 1: Comparison of Different Dosing Principles

(4) A commercially available dispenser controller having a non-volatile random access memory (NVRAM) with a high number of read/write cycles suitable to be coupled to a conductivity sensor such as for example the commercially available dispenser controllers Ecodos or Ecoplus dispenser (Ecolab USA Inc.) were programmed and configured to carry out the following different methods of dosing a detergent (Solid Super Ultra, available from Ecolab USA Inc.) into a single tank dishwasher (Meiko DV40N): 1: Continuously suspending detergent until a detergent concentration equaling 80% of the concentration at the setpoint is detected by the conductivity sensor, afterwards dosing in a variable pulse/pause mode with a pulse period of 20 s. The setpoint was 3.8 mS/cm; 2: Continuously suspending detergent until a detergent concentration equaling 90% of the concentration at the setpoint is detected by the conductivity sensor, afterwards dosing in a variable pulse/pause mode with a pulse period of 10 s. The setpoint was 3.8 mS/cm; 3: The method of the present invention, using an upper limit of 110% c*set and a lower limit of 90% c*set(x1=X2=10%). The setpoint was 4 mS/cm.

(5) The results of these dosing procedures is depicted in FIG. 3. It can be seen that in particular during the first dispensing/measuring step, a large concentration overshoot is obtained using the methods known from the state of the art (items 1 and 2 on the left and in the middle of FIG. 3, respectively), while using the method of the present invention a concentration very close to the setpoint is already obtained in the first dispensing event and large overshooting is avoided even in the second dispensing event.