Cleaning and liquid contact with solids – Processes – Work handled in bulk or groups
Reexamination Certificate
1996-01-26
2004-04-13
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Work handled in bulk or groups
C134S05600D
Reexamination Certificate
active
06718991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for machine dishwashing in institutional dishwashing machines in which a detergent and another active substance supporting the detergent in its effect are added to the wash liquor of the dishwashing machine. The invention also relates to an arrangement for carrying out the process which comprises a detergent feed system and a feed system for another active substance with an associated pump and pump control system.
An institutional dishwashing machine normally contains several tanks arranged in tandem from which wash liquor is sprayed against the crockery passing through the dishwashing machine. The tanks are arranged in the form of a cascade, the wash liquor passing successively through the tanks from the crockery exit or outlet end to the crockery entrance or inlet end, so that the degree of soiling of the wash liquor increases from the outlet end to the inlet end. Fresh water is introduced into the dishwashing machines at the outlet end. The quantity of detergent required is introduced into at least one washing tank also known as the feed tank. The detergent is normally added automatically in dependence upon the conductivity or the pH value of the wash liquor or, where liquid detergent or powder-form detergent already dissolved in water is added, even by means of a timed feed pump.
In normal machine dishwashing, starch deposits which build up on the crockery often cannot be prevented and existing starch deposits cannot be removed with the detergents used in practice in the usual in-use concentrations. Accordingly, crockery affected by starch deposits is subjected to so-called thorough cleaning at certain time intervals. In the thorough cleaning process, a distinctly above-average concentration of detergent is established in the wash liquor. Another alternative is to spray a highly concentrated alkaline detergent onto the crockery in the course of a routine dishwashing cycle. In addition, manual tank cleaning is also possible
2. Discussion of Related Art
It is known from DE-OS 17 28 093, which relates to dishwashing in domestic dishwashing machines, that a rinse aid may be added together with amylase to the rinsing water in order to remove starch deposits on the crockery. If desired, protease or lipase may be added to the rinse aid in addition to the amylase.
In addition, DE-AS 12 85 087 describes a machine dishwashing process in which an alkaline detergent is added to the dishwashing machine in the main wash cycle while an enzyme-containing, more particularly amylase-containing, rinse aid is introduced in the final rinse cycle and optionally in the prewash cycle. The object of this is to degrade starch formed on the crockery in the final-rinse cycle and optionally in the prewash cycle. However, it is specifically pointed out that the enzyme-containing rinse aid cannot be added in the main wash cycle because the alkalinity of the detergent would immediately destroy the ferments.
3. Description of the Invention
In the Journal Fette, Seifen, Anstrichmittel, 73 (1971), No. 7, page 464, left-hand column, third-to-last paragraph, it is summarily pointed out that enzyme-containing detergents cannot be used in institutional dishwashing machines on account of the long contact times required. In view of the brief contact time in which the crockery comes into contact with the wash liquor in institutional dishwashing machines, it would not appear possible to the expert that starch deposits on crockery can be prevented or degraded with enzyme-containing detergents in institutional dishwashing machines.
A corresponding process and an arrangement for carrying out this process are known from DE-A-39 20 728. In this known machine dishwashing process for institutional dishwashing machines, active oxygen is introduced into the feed or washing tank of the dishwashing machine in addition to the detergent as the other active substance supporting the detergent in its effect. To maintain the concentration of oxygen in the washing tank in the event of interruptions in the wash cycle, more active oxygen is introduced into the washing tank during the interruptions.
The object of the present invention was to provide a solution which would permanently suppress the formation of starch deposits on the crockery during machine dishwashing in institutional dishwashing machines.
In a process of the type mentioned at the beginning, the solution provided by the invention is characterized in that a low-alkali detergent, more particularly based on phosphate or nitrilotriacetic acid or salts thereof (NTA), is added as the detergent while a detergency booster containing an enzyme, preferably a carbohydrate-degrading enzyme, more particularly an amylase-containing detergency booster, is added as the additional active substance.
In an arrangement of the type mentioned at the beginning for carrying out the process, the solution provided by the invention is characterized by a feed system for an enzyme-containing detergency booster which is separate from the detergent feed system and which comprises an operational regime for maintenance feeding during interruptions in or stoppage phases of the operation of the dishwashing machine and/or feed intervals of the detergent feed system and/or an operational regime for surge feeding after interruptions in or stoppage phases of the operation of the dishwashing machine and/or feed intervals of the detergent feed system.
It has surprisingly been found that a low-alkali detergent in typical concentrations in conjunction with an enzyme-containing detergency booster leads to excellent removal of and inhibition of starch deposits on crockery, even over the brief contact times of 10 to 180 seconds typical of institutional dishwashing machines. Compared with known dishwashing processes which use a highly alkaline detergent or a highly concentrated alkaline wash liquor, the process according to the invention is distinguished by a considerable improvement in operational and applicational safety. There is no longer any risk of injury to operating personnel by highly alkaline detergent or wash liquor.
The enzyme-containing detergency booster may be introduced—in the same way as typical detergents—either into at least one feed or washing tank of the dishwashing machine or even into the liquid flowing through the final rinse pipe and/or the spray system of the institutional dishwashing machine and added in this way to the dishwashing machine. The detergency booster may contain as enzyme amylase, lipase, protease or other enzymes, more particularly carbohydrate-degrading enzymes, either individually or in the form of suitable mixtures. If desired, the low-alkali detergent may optionally contain other complexing agents than those mentioned.
In one embodiment of the invention, a concentration of 0.5 to 15 g/l of low-alkali detergent and a concentration of 0.05 to 2 g/l of detergency booster may be established in the wash liquor.
In another advantageous embodiment of the invention, a low-alkali detergent is introduced in the in-use concentration with a pH value of 7 to 11 and preferably in the range from 9.1 to 10.8.
In another particularly advantageous embodiment, the detergency booster introduced contains around 0.01 to 0.6% by weight and preferably 0.45 to 0.55% by weight of enzyme, particularly amylase, and 10 to 25% by weight and preferably 15 to 20% by weight of propylene glycol, more particularly 1,2-propylene glycol, and a corresponding quantity of water.
In another embodiment of the invention, the enzyme-containing detergency booster is added to the wash liquor at the same time as or after the low-alkali detergent during regular operation of the dishwashing machine at typical detergent concentrations of 0.5 to 8 g/l in the wash liquor and/or during periodic thorough cleaning at an increased concentration of detergent in the wash liquor of 3 to 15 g/l.
It is known that enzymes, such as amylase, lipase or protease, are not stable in the wash liquor of institutional dishwashing machines. After they h
Breyer Jacques
Hellmann Guenter
Hemm Dieter
Wilbert Klaus
Ecolab GmbH & Co. oHG
Markoff Alexander
Merchant & Gould P.C.
LandOfFree
Process and an arrangement for machine dishwashing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and an arrangement for machine dishwashing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and an arrangement for machine dishwashing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3255843