WO2005068060A1

WO2005068060A1 - Method and apparatus for producing a detergent stock solution for use in industrial washing machines

Info

Publication number: WO2005068060A1
Application number: PCT/EP2004/000005
Authority: WO
Inventors: Alexander GÜTHER; Thomas Fassbender
Original assignee: Ecolab Inc.
Priority date: 2004-01-02
Filing date: 2004-01-02
Publication date: 2005-07-28
Also published as: DK1703964T3; DE602004014534D1; ATE398486T1; ES2308134T3; EP1703964A1; EP1703964B1

Abstract

The invention discloses a method for producing a detergent stock solution (10) for use in industrial washing machines using a detergent paste product (2) from a paste stock container (1) effectively dissolved or dispersed in water for storage in a preparation tank (9) for detergent stock solution. A corresponding apparatus is described as well.

Description

Method and apparatus for producing a detergent stock solution for use in industrial washing machines

The present invention is related to a method for producing a detergent stock so- lution for use in industrial washing machines as well as an apparatus for producing such detergent stock solution.

The method and apparatus that forms the starting point of the invention is disclosed in EP 0 917 906 Bl . This prior art discloses a method for dissolving a predetermined quantity of finely divided solid detergent product by stirring it with a given quantity of water. In fact, the term "water" within the meaning of this prior art and within the meaning of the present invention means water or any other liquid on a water basis with other components dissolved or dispersed in water.

In the prior art method a finely divided solid detergent product is delivered into a preparation tank. The preparation tank is provided with a stirring means at the bottom or near to its bottom. A weighing device is used to measure the weight of the preparation tank with its contents. The necessary quantity of water is deli- vered into the preparation tank via a conduit opening without bearing down on the weighing device.

In this method the detergent product is delivered into the preparation tank by means of a conveyer as soon as the weight measured by the weighing device is lower than a first threshold. The delivering of the finely divided solid detergent product is continued until a second weight threshold of the preparation tank weighing means is reached. Then delivery of the finely divided solid detergent product into the preparation tank is stopped. Then water is introduced into the preparation tank via the conduit until a third weight threshold is reached. Then the delivery of water into the preparation tank is stopped. Then the stirring means is started and the water-detergent-mixture in the preparation tank is stirred until a complete dissolution of the finely divided solid detergent product within the water is reached. Thereafter a pump is started to pump the now complete detergent stock solution into either a storage tank or directly into the industrial washing machine. Apart from above mentioned prior art related to a method for dissolving finely divided solid detergent product into water which forms the starting point of the invention, there is a method where a detergent paste product is directly introduced into the washing process of a industrial washing machine. The use of a detergent paste product in comparison to a powdery detergent product has the advantage that the weight and volume of the powder is at least twice the weight and volume of the paste as calculated from the final amount of detergent stock solution available. For a predetermined detergent stock solution of predetermined detergent concentration, 500 kg of powdery detergent product is the equivalent to 270 kg of detergent paste product. It is obvious that a paste product is advantageous from this point of view.

In the prior art method for producing a detergent paste stock solution from a detergent paste product, the paste product is directly introduced into the washing machine by means of a rotary pump. It has to be understood that such kind of detergent paste product normally is a thixotropic product, i. e. a product with a viscosity decreasing when the product is mechanically stirred or the like. With such a rotary pump, the detergent paste product with normally high viscosity is mechanically moved so that its viscosity is reduced, enabling direct introduction of this product into the washing process in the washing machine. This kind of method requires complicated armatures and expensive equipment. It is not possible to produce a detergent stock solution. Because of its structural disadvantages, normally the method for producing a detergent stock solution based on the use of powdery detergent product is used for industrial applications.

Now, in view of the above, the object of the present invention is to provide a method for producing a detergent stock solution for use in industrial washing machines that is designed to use a detergent paste product instead of a powdery detergent product.

The above mentioned object is met by a method for producing a detergent stock solution comprising the features of claim 1. A corresponding apparatus realizing such method is described by the features of claim 25.

Preferred embodiments of either the method or the apparatus are the subject matter of the dependent method-claims or dependent apparatus-claims. In the method according to the invention the following steps are performed: a) pumping a predetermined amount or a predetermined mass flow or volume flow of a detergent paste product from a paste stock container to a mixing chamber, b) simultaneously with step a) introducing a controlled volume flow or mass flow of water from a water supply, preferably a water tap, to the mixing chamber, c) mixing the detergent paste product with the water in the mixing chamber in a first mixing step, d) pumping the detergent mixture from the mixing chamber to a preparation tank by means of a mixture pump means, e) collecting the detergent mixture coming from the mixture pump means in the preparation tank.

The term "pumping" in step a) covers not only pumping as such, but also conveying of the detergent paste product e. g. by an extrusion screw or the like. The essential aspect is that the detergent product is moved by a means that is adapted to the particular viscosity of this product in order to transport the detergent pro- duct into the mixing chamber.

In the mixing chamber, the delivered detergent paste product is mixed in a first mixing step with water from a water supply which is normally a water tap. The mixing chamber forms a first and essential part of a succession of mixing sta- tions. The second station is the mixture pump means. It depends on the specifics of this mixture pump means how intensive the mixing effect is. It will be very intensive if a rotary pump means like the one mentioned in the prior art above is used.

Here, as explained above, the term "water" covers also water with certain ingredients or supplements.

When leaving the mixture pump means, the detergent paste product is finely dissolved or dispersed in the water and now reaches the preparation tank where it is collected for further processing either towards the washing machine or towards a storage tank. Preferably the preparation tank is the third station for mixing by means of a stirring system in the tank.

By this sequence of steps in the claimed method it is possible to introduce a de- tergent paste product into a water supply to achieve a detergent stock solution which is collected in the preparation tank. So, it is possible for the first time to use a detergent paste product for supplying a paste stock solution. This has only been previously done with a powdery detergent product.

As far as the apparatus for producing a detergent stock solution for use in industrial washing machines is concerned, this apparatus shows the features of claim

25.

Main item of this apparatus are the mixing chamber, the mixture pump means and the preparation tank.

Now, the invention, preferred features and embodiments of the invention as well as preferred mechanical and constructional details of the invention are explained hereafter with reference to the accompanying drawings. In the drawings:

Fig. 1 shows in a schematic diagram the principle of the invention with certain preferred features,

Fig. 2 the mixing chamber of a preferred apparatus according to the in- vention,

Fig. 3 the principle of the introduction of the detergent paste product in the mixing chamber and the mixing with the stream of water from a water tap.

First of all, hereafter, the method for producing a detergent stock solution for use in industrial washing machines according to the invention shall be explained. Thereafter the corresponding apparatus will be explained following the drawings. Subject of the present invention is a method for producing a detergent stock solution for use in industrial washing machines. A first step is pumping a prede- termined amount or a predetermined mass flow or volume flow of a detergent paste product from a paste stock container to a mixing chamber. Simultaneously with this step a controlled volume flow or mass flow of water from a water supply, preferably a water tap, is introduced to the mixing chamber. Mixing of the detergent paste product with the water in the mixing chamber is done in a first mixing step. The detergent mixture is then pumped from the mixing chamber to a preparation tank by means of a mixture pump means. The detergent mixture coming from the mixture pump means is collected in the preparation tank.

As explained above, "pumping" means, in general, conveying the detergent paste product to the mixing chamber in a suitable way adapted to the specific characteristics of the paste product. In the end, the detergent paste product shall be finely dissolved or dispersed within the water in the preparation tank forming the final detergent stock solution that can be used then in the industrial washing ma- chine.

It has been found that it is much easier, sometimes even necessary, to dissolve the detergent paste product in warm water with a temperature higher than 25°C, preferably warm water at a temperature between 30°C and 40°C, at least in the first step, preferably in all water-related steps of the method. Tests have shown that a water temperature of e.g. 60°C is too high, at least for the specific detergent paste product used in the tests, because a grey film occurs on the surface of the detergent stock solution in the preparation tank. Further, negative effects for the measurement system might occur with hot water as explained later.

In order to achieve a particularly perfect dissolution or dispersion of the detergent paste product in the water, it is preferred that the stream of detergent paste product is introduced into the mixing chamber as thin strands or a succession of small droplets of paste product. This result can be achieved preferably in that the stream of detergent paste product is introduced into the mixing chamber through a sieve.

However, all other alternatives may be used, e.g. extruder-like equipment. Any- way, there is a first step with mechanical dispersion of the detergent paste product as a first step in the mixing process. Further, it is preferred that the detergent paste product is introduced into the mixing chamber passing through a valve means, wherein, preferably, the sieve is combined with the valve means. This valve means allows for a complete shut- off.

Further, it is preferred that the stream of detergent paste product is directed downwardly when introduced into the mixing chamber. Neither suction nor mixing is done against the gravitational forces. This is particularly helpful with detergent products like a paste product.

The high speed of water introduced into the mixing chamber and the resulting impact should be used to further dissolve or disperse the detergent paste product. So, it is preferred that the water is introduced into the mixing chamber as a stream directed towards the stream of detergent paste product. In a particularly preferred embodiment, it is proposed that the water be introduced into the mixing chamber in a way that the stream of detergent paste product is directed towards a sidewall of the mixing chamber. The reason is that a stream of detergent paste product, in the preferred embodiment the number of thin strands of detergent paste product, is/are directed towards the side wall of the mixing chamber by means of the impact of the stream of water. It is better to prevent the detergent paste product from reaching the bottom of the mixing chamber, because then the detergent paste product tends to accumulate at the bottom and to form a kind of residual paste cake that impairs the effectiveness of the mixing process.

This particular method can be further improved in that the water is introduced into the mixing chamber so that it initiates a swirling movement of water and detergent paste product within the mixing chamber.

Mixing of the detergent paste product with water in the mixing chamber is particularly improved if the mixing chamber gets a funnel-shaped contour. A funnel-shaped contour improves the swirling movement of the water stream along the sidewall as well as the mixing effect. It is possible to have a closed system. However, it has been realized that the quality of the paste stock solution is better if the detergent paste product is mixed with the water within the mixing chamber open to the ambient atmosphere.

The intensity of the resulting mixing effect depends on the specifics of the mixture pump means that are used in this method. If a rotary pump means like the one mentioned in the prior art above is used, this mixing effect will be very intensive indeed.

In an industrial washing process it is necessary to adapt the timing of the production of a detergent stock solution to the washing process itself. Sometimes the timing is crucial for the washing process. Therefore it is helpful if the mixing process can be accelerated. In this regard, a preferred embodiment of the invention provides that in the mixing chamber the detergent paste product is mixed with the water at an elevated detergent concentration and further water is added in the following method steps to reach the final detergent concentration. Preferably, the final concentration is between about 5 % and about 15 %, in particular about 10 %, and the elevated concentration is about 3 % to about 8 % higher than the final detergent concentration. In a very preferred embodiment it is provided that the further water is introduced directly into the preparation tank.

Normally the further water is provided from the same water tap but passes an additional and separate water meter. It is a kind of by-pass of the mixing chamber to speed up the mixing process.

An example of an embodiment comprises a pump means for the detergent paste product with an average pumping rate of 4000 g/min. From the water tap a volume flow of water of 20 1/min is provided by means of a flow- volume controller. This means a maximum theoretical concentration (mass concentration) of 16,66 %. However, this is the theoretical upper limit of possible concentrations. In fact, during continuous use the pumping rate of the pumping means decreases and in the end a realistic approach will be about 15 %. If a final concentration of the paste stock solution of 10 % is intended, then this final concentration is reached only with additional water fed into the preparation tank in above mentioned by- pass system. Of course, even in the preparation tank it is necessary to do some additional mixing or at least to prevent sedimentation of the detergent paste product from the detergent stock solution. So, it is preferred that the detergent stock solution in the preparation tank be continuously or discontinuously stirred, preferably with a stirring means at or near to the bottom of the preparation tank. In a particularly preferred embodiment it is provided that the detergent mixture is pumped into the preparation tank at or near to the bottom of the preparation tank. The fresh detergent mixture from the mixing pump means enters the preparation tank exactly where the stirring means acts so that the optimum mixing effect is achieved.

Of course, in order to determine and define the concentration of the detergent stock solution in the preparation tank some measures must be taken to calculate the specific factors. In the present and preferred embodiments it is provided that the volume of the detergent stock solution in the preparation tank is measured and/or controlled.

In order not to empty the preparation tank and in order to find a reference value for a filled preparation tank, it is preferable that the level of the detergent stock solution in the preparation tank be kept between a maximum and a minimum level. Refilling of detergent mixture is started when the minimum level is reached and is stopped when the maximum level is reached. The level of detergent stock solution in the preparation tank stays between those values. After transfer from the preparation tank to a storage tank, the minimum level indi- cation stops pumping from the preparation tank and starts the pumping of detergent paste product from the paste stock container to the mixing chamber as well as the introduction of water from the water tap. As soon as the maximum level is reached, the supply of detergent stock solution to the preparation tank is stopped. This is preferably the level for the elevated concentration which will be reduced thereafter in a final by-pass-water step.

It is necessary in calculating the concentration of the detergent stock solution that some measures must be taken. It is preferred in the present method that the mass of the detergent stock solution in the preparation tank be measured, preferably by means of a weighing means. This can be done by the means used in the prior art for the preparation tank in the method using the finally divided solid product. Now, the concentration is calculated from the mass of detergent paste product in the detergent stock solution in the preparation tank. This is done in the preferred embodiment of the invention in that the mass of detergent paste product in the detergent stock solution in the preparation tank is calculated from the difference between the mass of the detergent stock solution in the preparation tank as measured and the mass of water introduced as measured in all steps of the method, preferably as measured by a water meter in step b) or water meters for different steps.

In fact, this is a difference measurement. The calculation of the electronic control system is based on the intended concentration, the necessary supply of detergent paste product from the paste stock container, the measured supply of water from the water tap, measured by means of a water meter, and finally the measurement of the weight of the preparation tank with the detergent stock solution in it by means of weight cells or the like. As the weight cells are susceptible to high temperature, water of less than 60°C should be used.

This method can occur in two steps. First of all, there is a calculation of the dif- ference from the mixture received from the mixing pump means in the preparation tank compared to the water supplied from the water tap and measured by the water meter. The final product in the preparation tank then still has the elevated concentration of detergent product. In order to reduce this concentration from the elevated level to the intended level, water is additionally supplied to the prepara- tion tank directly from the by-pass supply over a second water meter. By measuring the weight of the preparation tank with the detergent stock solution, it is possible to precisely reach the intended final concentration of e.g. 10 % of detergent stock solution. This specific version with a water by-pass directly into the preparation tank reduces the time necessary to complete a supply of detergent stock solution. This last step may be performed without an additional weighing step, i.e. just calculating the final amount and concentration from the by-pass- water as measured by a water meter.

The preferred embodiment of the present method allows for an addition even of at least one washing aid to the detergent stock solution in the preparation tank. At present, washing aids are always prepared in liquid form and are directly measured into the washing machine. This requires extended supply lines, valve systems and control equipment. Now, with the present embodiment it is possible to introduce a washing aid that is stable together with the detergent directly into the preparation tank and to feed then the supplemented detergent stock solution either to a storage tank or directly to the washing machine. The washing aid, such as a softening aid or perfume carrier, may have the form of a liquid or may be present in finely divided solid form. Of course, more than one washing aid may be introduced into the preparation tank provided that is stable together with the detergent.

Now, with reference to the Fig. 1 to 3, a preferred embodiment of an apparatus for producing a detergent stock solution for use in industrial washing machines shall be explained. This explanation will be brief, because most of the aspects of the present invention have been explained before in relation to the method for producing a detergent stock solution.

The drawings show a preferred embodiment which discloses the best mode to practice the invention. The principle of the apparatus and method can be obtained from Fig. 1.

Fig. 1 shows an apparatus for producing a detergent stock solution for use in industrial washing machines, comprising a paste stock container 1 containing a supply of detergent paste product 2, a mixing chamber 3 and a paste pumping means 4 for pumping the detergent paste product 2 from the paste stock con- tainer 1 to the mixing chamber 3. In practice, here are two paste pumps 4a, 4b which are arranged in parallel in order to provide a redundancy. The paste stock container 1 may further contain a stirring means. Due to the thixotropic characteristics of such detergent paste product 2 in the paste stock container 1 the viscosity decreases when a slow stirring movement is introduced into the stock of paste product.

From the paste pumping means 4 a conduit 5 for the detergent paste product 2 leads to the mixing chamber 3.

Further, a water supply 6 is provided, preferably in the form of a water tap, the water supply 6 being connected to a water supply outlet 7 at the mixing chamber 3, a preparation tank 9 for collecting a supply of detergent stock solution 10, a mixture pump means 11 for pumping the detergent mixture from the mixing chamber 3 to the preparation tank 9, a control means 12 controlling operation of all pump means 4; 11 and auxiliary items like valve means 13, 14, 15 for preparation and storage of the detergent stock solution 10.

The control means 12 may be a programmable digital control means. The connections from the control means 12 to the different sensors and control drives etc. are not shown in order to improve legibility of Fig. 1.

It has been explained above that it is helpful to use slightly warm water with the detergent paste product 2, so in the preferred embodiment it is provided that the water supply 6 is a warm water supply for water with a temperature higher than 25°C, preferably warm water at a temperature between 30°C and 40°C.

Further, a fairly important feature of the method is to introduce the stream of detergent paste product 2 into the mixing chamber 3 as thin strands or a succession of small droplets of the paste product. To this end the apparatus provides a dividing means 16, preferably a sieve or a screen of metal or plastics at an outlet of the conduit 5 for the detergent paste product at the mixing chamber 3.

Likewise, as well as the paste pumping means 4 includes all kinds of conveying means for a paste product, those dividing means 16 can have any appropriate form, size and material suitable to achieve the division of the stream 17 of deter- gent paste product into those thin strands or succession of small droplets. The result is an improved mixing of the paste product with the water in the mixing chamber 3.

Above explanation already mentioned a valve means 13. This is a valve means at the outlet of the conduit 5 for paste product. However, in the present embodiment it is realized that the dividing means 16 is positioned downstream of the valve means 13. Valve means 13 will normally be a shut off valve controlled by control means 12. Fig. 1 to 3 shows that the dividing means 16 is intentionally positioned at the top of the mixing chamber 3. This means that the stream 17 of detergent paste pro- duct 2 is directed downwardly when introduced into the mixing chamber 3. This has the advantages explained already in connection with the method-steps.

Further, mixing efficiency in the mixing chamber 3 is further improved in that the water supply outlet 7 is positioned at the mixing chamber 3 at a place and with an orientation that the water is introduced into the mixing chamber 3 as a stream directed towards the stream 17 of detergent paste product. Fig. 3 shows that here the water is introduced into the mixing chamber 3 in a way that the stream 17 of detergent paste product is directed towards a side wall 18 of the mixing chamber 3. The stream 17 of detergent paste product 2 is deflected towards the side wall 18 of the mixing chamber 3 with the result explained above in connection with the method.

Finally, a further improvement of the mixing efficiency is realized in that the water supply outlet 7 is positioned at the mixing chamber 3 at a place and with an orientation that the water is introduced into the mixing chamber 3 so that it initiates a swirling movement of water and detergent paste product 2 within the mixing chamber 3. Fig. 2 explains a specific design of the mixing chamber 3. Here the mixing chamber 3 has a funnel-shaped contour.

Mixing of paste product and water is particularly effective if it is done under ambient atmosphere conditions. So the preferred embodiment shows a mixing chamber 3 that is open to the ambient atmosphere.

In the prior art that has been explained in the introductory part of the description a rotary pump with high mixing efficiency is used as a mixing means. If such rotary pump is used as the mixture pump means 11 this will perform a very effective further mixing step. There are other types of pump means 11 existing that have a still sufficient mixing capability.

Fig. 3 shows that here the valve means 15 is provided downstream of the mixture pump means 11.

In connection with the corresponding method-steps it has been explained before that a by-pass water supply directly into the preparation tank 9 increases the effectiveness and speed of the mixing process. To this end the present embodiment shows that a second water supply 19, preferably in the form of a water tap, is provided at the preparation tank 9. Of course, here is a valve means 19' provided as well.

In order to measure the supply of water for the detergent stock solution 10 in the present embodiment is provided that the water meter 21 is provided at the water supply 6 as well as a water meter 22 at the second water supply 19 for the bypass water fed directly into the preparation tank 9.

Fig. 1 shows a further improved embodiment in that a stirring means 23 is provided at or near to the bottom of the preparation tank 9. This is particularly effective, because the exit of a conduit 24 from the mixture pump means 11 is positioned in the preparation tank 9 at or near to the bottom of the preparation tank 9. So the introduction of the mixture from the mixture pump means 11 is exactly where the stirring means 23 is operating. This improves the efficiency of the further mixing step in the preparation tank 9.

Above it has been explained that the control means 12 shall be able to control and calculate the concentration of the detergent stock solution 10 that ends in the preparation tank 9. In the present embodiment it may be provided that the volume of the detergent stock solution 10 in the preparation tank 9 is measured and/or controlled by means of a level gauge 25. A level gauge 25 can be a mechanical system. However, nowadays electronic measuring systems for a liquid level in a tank are widely used. A preferred embodiment can employ a radar-related measurement from top to bottom, other systems employ capacitive level sensors, ultrasonic sensing, or laser measurements. However, it is possible to use the level gauge 25 as a backup means for control failure only. Then the level in the preparation tank 9 is normally only calculated from the output signals of the weighing cells 27.

As the preparation tank 9 is filled with detergent mixture coming from the mixture pump means 11 and introduced into the preparation tank 9 through the conduit 24, simultaneously additional by-pass water is fed into the preparation tank 9 directly by feed conduit 19", the level gauge 25 must measure the filling level, at least a maximum level and a minimum level. When the maximum level is reached, the control means 12 stops further supply of detergent paste product 2 and water. However, the level gauge 25 should be able to measure a level lower than the maximum level, because it may be necessary that the control means 12 stops the paste pumping means 4 somewhat earlier than the by-pass water supply 19.

A minimum level must be measured by the level gauge 25, in order to stop further pumping from the preparation tank 9 so that always a minimum level of stock solution 10 remains in the preparation tank 9. In an exemplary embodiment the level can be kept between a maximum of 500 1 and a minimum of 100 1.

In order to measure the content of the preparation tank 9 it is provided that the preparation tank 9 is equipped with a weighing means 26 so that the mass of the detergent stock solution 10 in the preparation tank 9 is measured. In the present embodiment the weighing means 26 comprises three weight cells 27 equally dis- tributed below the bottom of the preparation tank 9. Weight cells of this kind are employed in the weighing means of the prior art EP 0 917 906 Bl as well.

In the preferred embodiment provided by the present invention the control means 12 calculates the concentration of detergent paste product 2 in the detergent stock solution 10 in the preparation tank 9 in an indirect way. In fact, the control means 12 is provided to calculate the mass of detergent paste product 2 in the detergent stock solution 10 in the preparation tank 9 from the difference between the mass of the detergent stock solution 10 in the preparation tank 9 as measured and the mass of water introduced as measured from the water supply 6 or the water supplies 6, 19.

Finally, as schematically indicated in Fig. 1, there is a further improvement of the apparatus in that an additional feed conduit 28 or the like is provided at the preparation tank 9 for the introduction at least one washing aid that is stable to- gether with the detergent. Here, the additional feed conduit 28 is for one liquid washing aid that is stable when stored with the detergent stock solution 10. The advantages of such early introduction of washing aids into the stock solution has been discussed above.

Finally, as explained above, there is the possibility to store the detergent stock solution 10 in the preparation tank 9 itself until it is used in the washing process. This system, however, is improved in the present embodiment in that it is provided that the detergent stock solution 10, after reaching the maximum level in the preparation tank 9, is pumped to a further storage tank not shown in Fig. 1. However, Fig. 1 shows further conduit means 29, pump means 30a, 30b and valve means 3 la, 3 lb providing the connection from the preparation tank 9 to the storage tank. The dual line system with two pump means 30a, 30b allows pumping from the preparation tank 9 to the storage tank from two different levels of the preparation tank 9.

Claims

Claims:

1. Method for producing a detergent stock solution for use in industrial washing machines with the steps of a) pumping a predetermined amount or a predetermined mass flow or volume flow of a detergent paste product from a paste stock container to a mixing chamber, b) simultaneously with step a) introducing a controlled volume flow or mass flow of water from a water supply, preferably a water tap, to the mixing chamber, c) mixing the detergent paste product with the water in the mixing chamber in a first mixing step, d) pumping the detergent mixture from the mixing chamber to a preparation tank by means of a mixture pump means, e) collecting the detergent mixture coming from the mixture pump means in the preparation tank.

2. Method according to claim, characterized in that warm water with a temperature higher than 25°C, preferably warm water at a temperature between 30°C and 40°C, is used at least in step b), preferably in all water-related steps of the method.

3. Method according to claim 1 or 2, characterized in that the stream of detergent paste product is introduced into the mixing chamber as thin strands or a succession of small droplets of paste product.

4. Method according to claim 3, characterized in that the stream of detergent paste product is introduced into the mixing chamber through a sieve.

5. Method according to any one of the preceding claims, characterized in that the detergent paste product is introduced into the mixing chamber passing through a valve means, wherein, preferably, the sieve is combined with the valve means.

6. Method according to any one of the preceding claims, characterized in that the stream of detergent paste product is directed downwardly when introduced into the mixing chamber.

7. Method according to any one of the preceding claims, characterized in that the water is introduced into the mixing chamber as a stream directed towards the stream of detergent paste product.

8. Method according to claim 7, characterized in that the water is introduced into the mixing chamber in a way that the stream of detergent paste product is directed towards a side wall of the mixing chamber.

9. Method according to any one of the preceding claims, characterized in that the water is introduced into the mixing chamber so that it initiates a swir- ling movement of water and detergent paste product within the mixing chamber.

10. Method according to any one of the preceding claims, characterized in that the mixing chamber presents a funnel-shaped contour to the stream of water and detergent paste product.

11. Method according to any one of the preceding claims, characterized in that the detergent paste product is mixed with the water within the mixing chamber open to the ambient atmosphere.

12. Method according to any one of the preceding claims, characterized in that the detergent paste product is further intensively mixed with the water in a second mixing step performed by the mixture pump means.

13. Method according to any one of the preceding claims, characterized in that in the mixing chamber the detergent paste product is mixed with the water at an elevated detergent concentration and further water is added in the following method steps to reach the final detergent concentration, wherein, preferably, the final concentration is between about 5 % and about 15 %, in particular about 10 %, and the elevated concentration is about 3 % to about 8 % higher than the final detergent concentration.

14. Method according to claim 13, characterized in that the further water is introduced into the preparation tank.

15. Method according to any one of the preceding claims, characterized in that the detergent stock solution in the preparation tank is continuously or dis- continuously stirred, preferably with a stirring means at or near to the bottom of the preparation tank.

16. Method according to any one of the preceding claims, characterized in that the detergent mixture is pumped into the preparation tank at or near to the bottom of the preparation tank.

17. Method according to any one of the preceding claims, characterized in that the volume of the detergent stock solution in the preparation tank is measured and/or controlled.

18. Method according to claim 17, characterized in that the level of the detergent stock solution in the preparation tank is kept between a maximum and a minimum level, wherein, preferably, refilling of detergent mixture is started when the minimum level is reached, and is stopped when the maximum level is reached.

19. Method according to any one of the preceding claims, characterized in that the mass of the detergent stock solution in the preparation tank is measured, preferably by means of a weighing means.

20. Method according to any one of the preceding claims, characterized in that the concentration is calculated from the mass of detergent paste product in the detergent stock solution in the preparation tank.

21. Method according to claims 19 and 20, characterized in that the mass of detergent paste product in the detergent stock solution in the preparation tank is calculated from the difference between the mass of the detergent stock solution in the preparation tank as measured and the mass of water introduced as measured in all steps of the method, preferably as measured by a water meter in step b) or water meters in step b) and a further step or further steps.

22. Method according to any one of the preceding claims, characterized in that at least one washing aid that is stable together with the detergent is introduced into the preparation tank.

23. Method according to claim 22, characterized in that the washing aid or washing aids are introduced into the preparation tank in liquid or finely di- vided solid form.

24. Method according to any one of the preceding claims, characterized in that the detergent stock solution, after reaching the maximum level in the preparation tank and sufficient stirring and/or mixing, is pumped to a storage tank.

25. Apparatus for producing a detergent stock solution for use in industrial washing machines, comprising a paste stock container (1) containing a supply of detergent paste product (2), a mixing chamber (3), a paste pumping means (4) for pumping the detergent paste product (2) from the paste stock container (1) to the mixing chamber (3), a water supply (6), preferably in the form of a water tap, the water supply (6) being connected to a water supply outlet (7) at the mixing chamber (3), a preparation tank (9) for collecting a supply of detergent stock solution (10), a mixture pump means (11) for pumping the detergent mixture from the mixing chamber (3) to the preparation tank (9), a control means (12) controlling operation of all pump means (4; 11) and auxiliary items like valve means (13, 14, 15) for preparation and storage of the detergent stock solution (10), preferably operated to provide the method steps of claim 1.

26. Apparatus according to claim 25, characterized in that the water supply (6) is a warm water supply for water with a temperature higher than 25°C, preferably warm water at a temperature between 30°C and 40°C.

27. Apparatus according to any one of the preceding apparatus-claims, characterized in that a dividing means (16), preferably a sieve or a screen of metal or plastics is provided at an outlet of a conduit (5) for the detergent paste product at the mixing chamber (3).

28. Apparatus according to any one of the preceding apparatus-claims, characterized in that a valve means (13) is provided at an outlet of a conduit (5) for the detergent paste product at the mixing chamber (3).

29. Apparatus according to claims 27 and 28, characterized in that the dividing means (16) is positioned downstream of the valve means (13).

30. Apparatus according to claim 27 or 29, characterized in that the dividing means (16) is positioned at the top of the mixing chamber (3) so that the stream (17) of detergent paste product is directed downwardly when introduced into the mixing chamber (3).

31. Apparatus according to claim 30, characterized in that the water supply outlet (7) is positioned at the mixing chamber (3) at a place and with an ori- entation that the water is introduced into the mixing chamber (3) as a stream directed towards the stream (17) of detergent paste product.

32. Apparatus according to claim 31, characterized in that the water is introduced into the mixing chamber (3) in a way that the stream (17) of deter- gent paste product is directed towards a side wall (18) of the mixing chamber (3).

33. Apparatus according to any one of the preceding apparatus-claims, characterized in that the water supply outlet (7) is positioned at the mixing cham- ber (3) at a place and with an orientation that the water is introduced into the mixing chamber (3) so that it initiates a swirling movement of water and detergent paste product within the mixing chamber (3).

34. Apparatus according to any one of the preceding apparatus-claims, charac- terized in that the mixing chamber (3) has a funnel-shaped contour.

35. Apparatus according to any one of the preceding apparatus-claims, characterized in that mixing chamber (3) is open to the ambient atmosphere.

36. Apparatus according to any one of the preceding apparatus-claims, characterized in that the mixture pump means (1 1) is a rotary pump with high mixing efficiency for the detergent paste product (2) in water.

37. Apparatus according to any one of the preceding apparatus-claims, charac- terized in that a valve means (15) is provided downstream of the mixture pump means (11).

38. Apparatus according to any one of the preceding apparatus-claims, characterized in that a second water supply (19), preferably in the form of a water tap, is provided at the preparation tank (9).

39. Apparatus according to any one of the preceding apparatus-claims, characterized in that a water meter (21; 22) is provided at the water supply (6) and, if existing, the second water supply (19).

40. Apparatus according to any one of the preceding apparatus-claims, characterized in that a stirring means (23) is provided at or near to the bottom of the preparation tank (9).

41. Apparatus according to any one of the preceding apparatus-claims, characterized in that the exit of a conduit (24) from the mixture pump means (11) is positioned in the preparation tank (9) at or near to the bottom of the preparation tank (9).

42. Apparatus according to any one of the preceding apparatus-claims, characterized in that the volume of the detergent stock solution (10) in the prepa- ration tank (9) is measured and/or controlled by means of a level gauge (25).

43. Apparatus according to claim 42, characterized in that the level gauge (25) measures the filing level of the detergent stock solution (10) in the preparation tank (9) or measures at least a maximum level and a minimum level of the detergent stock solution (10) in the preparation tank (9).

44. Apparatus according to any one of the preceding apparatus-claims, charac- terized in that the preparation tank (9) is equipped with a weighing means (26) so that the mass of the detergent stock solution (10) in the preparation tank (9) is measured.

45. Apparatus according to claim 44, characterized in that the weighing means (26) comprises a number of, preferably three, weight cells (27).

46. Apparatus according to any one of the preceding apparatus-claims, characterized in that the control means (12) is provided to calculate the concentration from the mass of detergent paste product (2) in the detergent stock solution ( 10) in the preparation tank (9) .

47. Apparatus according to the claims 44 and 46, characterized in that the control means (12) is provided to calculate the mass of detergent paste product (2) in the detergent stock solution (10) in the preparation tank (9) from the difference between the mass of the detergent stock solution (10) in the preparation tank (9) as measured and the mass of water introduced as measured from the water supply (6) or the water supplies (6, 19).

48. Apparatus according to any one of the preceding apparatus-claims, charac- terized in that an additional feed conduit (28) or the like is provided at the preparation tank (9) for the introduction of at least one washing aid that is stable together with the detergent.

49. Apparatus according to the claim 48, characterized in that the washing aid or washing aids are introduced into the preparation tank (9) in liquid or finely divided solid form.

0. Apparatus according to any one of the preceding apparatus-claims, characterized in that further conduit means (29), pump means (30) and/or valve means (31) are connected to the preparation tank (9) providing a connection from the preparation tank (9) to a storage tank for detergent stock solution (10).