EP0478650B1 - Process for operating a dishwasher and device for implementing the process - Google Patents

Abstract

PCT No. PCT/EP90/00944 Sec. 371 Date Feb. 18, 1992 Sec. 102(e) Date Feb. 18, 1992 PCT Filed Jun. 15, 1990 PCT Pub. No. WO91/00044 PCT Pub. Date Jan. 10, 1991.A dishwashing machine includes a washing tank for receiving wash water, and a detergent from a detergent dispensing system. A separate dosing system includes a tank for storing bleach, and a pump for supplying bleach from the bleach tank to the washing tank in measured quantities at predetermined times to maintain a desired active oxygen content therein over a complete cycle of operation.

Description

The invention relates to a method for operating a dishwasher having a wash tank, in which a detergent supported or supplemented by a bleaching agent is metered into the wash tank. It further relates to a device for supplying the washing tank of a dishwasher with chemical substances, consisting of a detergent metering system for supplying cleaning agent and a separate metering system comprising a pump and a storage container for supplying another agent.

The wash tank of a commercial dishwasher, which is also referred to as a metering tank - machines of this type are particularly important in the present context - is supplied with fresh water during the rinsing phase via the rinse aid. The appropriate amount of detergent is regulated - if necessary, via conductivity. In practice, alkaline cleaners of the type mentioned contain active chlorine as the bleaching component, usually in the form of chlorine bleach in liquid cleaners or in the form of di- and trichloroisocyanurates in powder cleaners.

The use of active chlorine as a bleaching agent in dishwashers is ecologically questionable, so the aim is to use environmentally friendly bleaching agents. This has caused considerable difficulties. As economically justifiable As an alternative to active chlorine, only active oxygen is currently available. However, this active ingredient cannot be formulated with the generally strongly alkaline liquid cleaners.

It is possible to incorporate solid active oxygen carriers into powdered alkaline cleaners. Such detergent formulations, however, quickly lose their bleaching effect after being washed into the washing tank of the dishwasher, because the active oxygen content in the washing liquor drops rapidly, frequently at about 40 to 60% per hour, during a machine downtime. When a new rinsing cycle is reinserted, there is not enough active oxygen available in the washing tank, so that the cleaning performance at the beginning of the rinsing cycle can be unsatisfactory.

From EP A-0195619 a method is known in which rinsing cycles with an agent containing active oxygen are carried out after one or more washing cycles in a dishwasher with a spray device.

Furthermore, from US-A 4373863 a device for supplying the snack tank of a dishwasher with chemical substances is known, consisting of a: detergent dosing system for feeding detergent and a separate dosing system comprising a pump and a storage container for feeding another agent .

The invention has for its object to enable the use of active oxygen as a bleaching agent in cooperation with an alkaline liquid cleaner in terms of process technology and also when using a bleaching agent containing Powder cleaner to exclude a drop in the active oxygen content in the wash tank which is disruptively large during a dosing break. The solution according to the invention for the process of the type mentioned at the outset is that when active oxygen is used as bleaching agent, the active oxygen content in the wash tank is maintained during maintenance doses of the detergent by maintenance dosing of the bleaching agent. Maintenance dosing should preferably take place in individual dosing strokes.

The invention accordingly relates primarily to a maintenance dosage of the bleach during the downtimes of the dishwasher between two successive washing phases. This maintenance dosage ensures that as the active oxygen breaks down, new bleaching agent containing active oxygen gets into the wash tank. The washing tank of the dishwasher is therefore always ready for a new washing phase, so it can immediately supply detergent sufficiently mixed with bleach at the beginning of the washing phase.

For this purpose, it can be provided according to a further invention that when using a bleaching agent for immediate rinsing, detergent containing itself in sufficient quantity, in particular powdery form, during the standstill phases or dosing pauses of the detergent, the bleaching agent is replenished to the extent of the active oxygen breakdown.

In addition to this maintenance dosage, a parallel dosage of bleach should preferably be provided when using a bleach-free cleaner, in particular a liquid cleaner. Since means that according to another invention when using a bleach-free detergent during the rinsing phase, bleaching agent is dosed into the wash tank to the extent of the detergent consumption and during the standstill phases or during detergent dosing breaks to the extent of the active oxygen breakdown. The parallel dosing mentioned thus enables the use of active oxygen carriers, such as. B. hydrogen peroxide (H₂O₂) and / or peracetic acid solution, which cannot be formulated with the usual, bleach-free alkaline cleaners.

According to the above, depending on the conductivity control or the like, the dosing or rinsing of liquid or powdered detergent takes place during the rinsing phases only during certain dosing times. If the corresponding intermediate times or detergent dosing breaks become so long that an amount of active oxygen which has an adverse effect on the cleaning performance of the next rinsing phase has decayed, it is within the scope of the invention, also in intermediate or regular breaks of the parallel dosing occurring during the rinsing phases, to the extent of Active oxygen decay according to bleach, also as a maintenance dose.

For the method described, it can furthermore be advantageous if the bleaching agent delivery rate of the maintenance dosage is optimized on the basis of an active oxygen determination. After knowing the rate of decay of the active oxygen, it may suffice if bleaching agent is replenished at certain intervals; in this context, it is preferred if, after the decomposition of about 20% of the active oxygen present, the dosing or maintenance dosing is started.

In a device for supplying the washing tank of a dishwasher with chemical substances, consisting of a detergent metering system for supplying cleaning agent and a separate metering system comprising a pump and a storage container for supplying another agent, the solution according to the invention of the above-mentioned object consists in this that the further dosing system is a bleach dosing system which has an operating state for maintenance dosing which is activated during the cleaning agent dosing breaks.

The detergent dosing system can be designed in a conventional manner, e.g. B. as a metering pump in a liquid cleaner or as fresh water or liquor in a powder cleaner. In addition, according to the invention there is essentially only the bleach dosing system which is separate or separate from the detergent dosing system. This allows parallel dosing at the same time as the dosing of the bleach-free cleaner and enables maintenance dosing during the downtimes of the dishwasher or during the detergent dosing breaks, so that a drawdown of the active oxygen is compensated for during this time.

Such additional or maintenance dosing is required if the cleaning supply to the dishwasher is carried out, as usual, via a regulation that does not take the bleach content into account. In contrast to active oxygen, the cleaner concentration or amount remains constant during the standstill phases. At the start of the rinse, only detergent corresponding to the fresh water supply quantities would be brought into the rinsing room without the bleaching agent being added. There would then be a deficit Active oxygen and thus an unsatisfactory washing result, at least for bleachable soiling. According to the invention, these problems are overcome by adding a bleach dosing system.

According to the above, two configurations are particularly suitable: Either the bleach dosing system only has one operating state for maintenance dosing, if there is a detergent containing bleach anyway, or the bleach dosing system additionally has an operating state that promotes parallel dosing to the detergent dosing system when the cleaner is switched on -Dosing system if a bleach-free cleaner is used. According to this embodiment, both bleach-containing and bleach-free detergents can be used, bleaching agents having to be dosed only once during the entire operating time of the dishwasher and in the other case only during the standstill phases between two rinsing phases or only during the detergent dosing. The parallel and maintenance doses differ essentially only in the bleaching agent dose, that is to say in the amount of active oxygen conveyed into the wash tank per unit of time.

According to another invention, a frequency-controlled squeeze pump can be used for parallel or maintenance dosing of the bleach dosing system. Such a pump can be operated with the decay of active oxygen corresponding number of pump strokes per unit of time. Relatively few pump strokes are then sufficient for maintenance dosing, while a much larger number of pump strokes are required for parallel dosing when using a bleach-free cleaner. In practice, it is preferred if the associated frequency control of the Pump has a first control range for maintenance dosing and optionally a second control range for the dishwashing phase of the dishwasher when the detergent dosing system is switched on and has a significantly increased delivery rate compared to the dose of the first control range.

Fig. 1

ein Blockschaltbild einer Parallel- und Unterhaltsdosiereinrichtung für Bleichmittel;

Fig. 2

ein Funktionsdiagramm für eine Parallel- und Unterhaltsdosierung von Bleichmittel bei einer gewerblichen Geschirrspülmaschine;

Fig. 3

ein Blockschaltbild für die Unterhaltsdosierung bei einer mit aktivsauerstoffhaltigen Pulverreiniger versorgten Geschirrspülmaschine; und

Fig. 4

ein Funktionsdiagramm der Reiniger- und Wirkstoffversorgung entsprechend Fig. 3.

Further details of the invention are explained on the basis of the schematic illustration in the accompanying drawing. Show it:

Fig. 1

a block diagram of a parallel and maintenance dosing device for bleach;

Fig. 2

a functional diagram for a parallel and maintenance dosing of bleach in a commercial dishwasher;

Fig. 3

a block diagram for maintenance dosing in a dishwasher supplied with active oxygen-containing powder cleaner; and

Fig. 4

3 shows a functional diagram of the detergent and active ingredient supply according to FIG. 3.

Fig. 1 shows the liquid cleaner and bleach supply part to be assigned to a commercial dishwasher. A conventional liquid detergent metering pump 1 delivers liquid detergent 2 from a liquid detergent tank, for example regulated via a conductivity measurement, through a line 3 to a (not shown) washing tank of a dishwasher. In parallel to the liquid cleaner metering pump 1, a peristaltic pump 4 is provided, which also delivers bleach 5 from a tank containing active oxygen through a line 6 to the aforementioned wash tank. This additional parallel and maintenance dosing system for liquid compounded active ingredients can be controlled with internal and external electronics so that a function diagram according to FIG. 2 is obtained.

Fig. 2 shows in three lines 7, 8 and 9 different on and off states (1/0) depending on the time t. In the 7th The top line designated symbolizes the operating state of the dishwasher. The rinsing phases or switch-on states are denoted by 10, the standstill phases or switch-off states are denoted by 11. In the second line, designated 8, the normal detergent dosage, that is the operating state of the liquid detergent dosage pump 1, is shown. Depending on the conductivity of the cleaner located in the washing tank of the dishwasher, the metering pump 1 is started twice in the exemplary embodiment during a machine switch-on state 10. The corresponding two detergent dosing times are designated 12 and 13. An intermediate pause is indicated by 14 and the main pause corresponding to the switch-off state 11 of the dishwasher is identified by 15. In the third line, designated 9, the additional dosage of active substance, that is to say the operating state of the peristaltic pump 4, is indicated.

As can be seen from FIG. 2, a parallel metering 16 with a rapid sequence of individual pump strokes of the peristaltic pump 4 is provided during the metering times 12, 13 of the metering pump 1. In contrast, the work of the peristaltic pump 4 is very slowed down during breaks 14, 15 of the dishwasher; In the corresponding maintenance metering 17, significantly fewer pump strokes are provided per unit of time than during parallel metering 16 in the rinsing phases 10. As can be seen, cleaning liquid is not replenished during the idle phases 11 of the dishwasher. Such metering is not necessary since the amount of cleaning solution will not be reduced. Only the decay of the active oxygen during the standstill phase 11 is slowed down by the subsequent metering or maintenance metering 17 in these periods balanced. It may also be favorable to provide individual pump strokes of a maintenance dosage 18 during longer pauses 14 in the washing phases 10 of the dishwasher in order to compensate for the decay of active oxygen which also occurs continuously during this time.

If the dishwasher cleaner already contains active oxygen, as is particularly possible with powder cleaners, the parallel metering according to the invention generally does not need to be provided, rather the maintenance metering is sufficient. 3, the normal metering of active oxygen-containing powder cleaner 19 takes place in a funnel 20 via fresh water or liquor flushing 21 and a line 22 to the washing tank of the dishwasher (arrow direction).

In addition, a bleach metering system with a peristaltic pump 4 is provided according to FIG. 3, similar to FIG. 1, which can also convey bleach 5 from a bleach tank via a line 6 to the washing tank of the dishwasher. In contrast to the case of FIG. 1, the peristaltic pump 4 according to FIG. 3 only works during the standstill phases 11 of the dishwasher, because with the normal detergent dosing during the rinsing phases 10 the bleaching agent is already dosed together with the detergent. Only in an intermediate pause 14 of two control doses 12 and 13 according to FIG. 4, it may be favorable, similar to the case in FIG. 2, one or more dosing strokes as switched as maintenance dosing 18 in the standstill phase 11 of the dishwasher will provide.

For operating maintenance and, if necessary, parallel dosing a modification of a frequency-controlled peristaltic pump can preferably be used. Two control ranges of the frequency control are intended, firstly in an area I for the parallel metering 16 with a delivery rate range of 8 to 290 ml / min and secondly in an area II for the maintenance metering 17, 18 with a delivery rate range of 1.5 to 3.5 ml / min. These two control ranges should be selectable externally so that readjustment is possible according to the washing result.

Reference list

1

= Liquid detergent dosing pump

2nd

= Liquid cleaner

3rd

= Liquid cleaner line

4th

= Peristaltic pump

5

= Bleach

6

= Bleach line

7

= top line (Fig. 2)

8th

= second line

9

= third line

10th

= Rinsing phase

11

= Standstill phase

12th

= Detergent dosing time (1)

13

= Detergent dosing time (1)

14

= Break (1)

15

= Main break (1)

16

= Parallel dosing

17th

= Maintenance dosage

18th

= Maintenance dosage

19th

= Powder cleaner

20th

= Funnel

21

= Fleet flushing

22

= Line

Claims (11)

1. Method of operating a dishwashing machine comprising a washing tank, in which a detergent assisted or complemented in effect by a bleach is metered into the washing tank, characterised in that, where active oxygen is used as the bleach component, the active oxygen content in the washing tank is maintained during pauses (14, 16) in the dosing of the detergent (2, 19) by a maintenance dosing (17, 18) of the bleach (5).
2. Method according to claim 1, characterised in that the maintenance dosing (17, 18) takes place in individual dosing strokes.
3. method according to claim 1 or 2, characterised in that, where a detergent, particularly a powder-form detergent, basically containing bleach in sufficient quantity for immediate rinsing is used, bleach (5) continues to be metered into the washing tank. during the stoppage phases (11) or pauses (14) in the dosing of detergent (2, 19) in proportion to the decrease in the active oxygen content.
4. Method according to claim 1 or 2, characterised in that, where a bleach-free detergent, particularly a liquid detergent, is used, the bleach (5) is introduced into the washing tank during the rinse phases (5) in proportion to the detergent consumption and during the stoppage phases (11) or pauses (14) in the dosing of detergent in proportion to the decrease in the active oxygen content.
5. Method according to one of claims 1 to 45, characterised in that the bleach feed capacity of the maintenance dosing (17, 18) is optimised by determination of the active oxygen content.
6. Method according to one of claims 1 to 5, characterised in that hydrogen superoxide or peracetic acid solution is used as the active oxygen carrier.
7. Method according to one of claims 1 to 6, characterised in that the follow-up or maintenance dosing (17, 18) of the bleach (5) is commenced each time after reduction of around 20% in the original active oxygen content.
8. Apparatus for supplying the washing tank of a dishwashing machine with chemical substances, consisting of a detergent dosing system for supplying detergent (2, 19) and a further dosing system, which is separate therefrom and comprises a pump (4) and a storage container, for supplying a further substance, characterised in that the further dosing system is a bleach dosing system which has an operational mode for maintenance dosing (17, 18), which is activated during the pauses (14, 15) in the dosing detergent.
9. Apparatus according to claim 8, characterised in that the bleach dosing system additionally has an operational mode which conveys in parallel with the detergent dosing system, for a parallel dosing (16) when the detergent dosing system is switched on.
10. Apparatus according to claim 8 or 9, characterised in that a frequency-controlled peristaltic pump (4) is provided for conveying the bleach (5).
11. Apparatus according to claim 10, characterised in that the associated frequency control system of the pump (4) has a first regulating range for the maintenance dosing (17, 18) and optionally a second regulating range for the rinse phase (10) of the dishwashing machine, when the detergent dosing system is on, with a considerably increased feed capacity in relation to the dose of the first regulating range.

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