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 the use of said dispenser for controlling dosing of a product in a washing machine.

Claims

1. A washing machine comprising: a dispenser equipped with a reversibly closable output device having a minimum opening time (t.sub.min) the dispenser has to be opened; a controller adapted to be coupled to the dispenser and a measuring means for measuring at least one parameter c*, wherein c* corresponds to the concentration of a detergent in the dispenser; including at least one processor; and including at least one non-volatile memory programmed with an algorithm to execute a method, the method comprising: (a) 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); (b) calculating the difference (c*) between the setpoint (c*.sub.set) and the current concentration in the machine (c*.sub.cur); (c) 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; and (d) 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), 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 x.sub.1 is 0<x.sub.125% and x.sub.2 is 0<x.sub.240%.

2. The washing machine of claim 1, wherein the non-volatile memory is a non-volatile random access memory having a high number of read/write cycles.

3. The washing machine of claim 1, wherein the measuring means comprises at least one sensor.

4. The washing machine of claim 3, wherein the at least one sensor is a conductivity sensor.

5. The washing machine of claim 1, further comprising a spray arm, a plurality of nozzles, a wash tank, a run-off plate, and a circulating pump.

6. The washing machine of claim 4, wherein the parameter (c*) is measured in the wash tank of the machine.

7. The washing machine of claim 1, wherein the minimum opening time (t.sub.min) is from about 0.25 seconds (s) to about 1 second.

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 washtank (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 an illustrative diagram of a dispenser controller (10) which includes a flow chart illustrating the principle dosing algorithm 14 the dispenser controller 10 is programmed with in order to carry out the method of the present invention. The dispenser controller includes a central processing unit (CPU) (11), a random access memory (RAM) (12), a read only memory (ROM) (13) for storing the algorithm (14) executed by the CPU (11) and a non-volatile memory (e.g. a non-volatile random access memory, NVRAM) (15) for storing parameters that control the dispenser's operation.

(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 (x.sub.1=x.sub.2=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.