Cleaning and liquid contact with solids – Processes – Work handled in bulk or groups
Patent
1992-02-18
1994-02-22
Bell, Mark L.
Cleaning and liquid contact with solids
Processes
Work handled in bulk or groups
134 253, 134 18, 134 29, 134 93, 68 1218, 68 17R, B08B 304, B08B 308
Patent
active
052883310
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
1.0 Field Of The Invention
This invention relates generally to dishwashing machines, and more particularly to methods and apparatus for supplying the washing tank of a dishwashing machine with chemical substances.
2.0 Discussion Of Related Art
In institutional dishwashing machines, with which the present invention is particularly concerned, fresh water is supplied to washing tank--also known as the dosing tank--in the clear-rinse phase. The corresponding quantity of detergent--controlled through conductivity--is subsequently added as required. Alkaline detergents of the described type used in practice contain active chlorine as their bleach component, mostly in the form of liquid chlorine bleach in the case of liquid detergents or in the form of di- and trichloroisocyanurates in the case of powder-form detergents.
The use of active chlorine as bleach in dishwashing machines is ecologically objectionable. As a result, efforts are being made to use environment-friendly bleaches. Considerable difficulties have been encountered in this regard. At the present time, only active oxygen is available as an economically reasonable alternative to active chlorine. However, this bleaching agent cannot be formulated with the generally highly alkaline liquid detergents.
Although solid active oxygen carriers can be incorporated in powder-form alkaline detergents, corresponding detergent formulations quickly lose their bleaching effect after flushing into the washing tank of the dishwashing machine because the active oxygen content of the rinse liquor quickly diminishes--often at around 40 to 60% per hour--during machine stoppage times. When a new rinse cycle begins, insufficient active oxygen is available in the washing tank so that cleaning performance can be unsatisfactory at the beginning of the rinse cycle.
EP-A-0 195 619 describes a method in which rinse cycles are carried out with a substance containing active oxygen after one or more wash cycles in a dishwashing machine comprising a spray unit.
In addition, U.S. Pat. No. 4,373,863 describes an apparatus for supplying the washing tank of a dishwashing machine with chemical substances which consist of a detergent dosing system for supplying detergent and a separate dosing system comprising a pump and a storage container for supplying another substance.
3.0 Summary Of The Invention
The problem addressed by the present invention was to enable active oxygen to be used as bleach in conjunction with an alkaline liquid detergent and to eliminate any significant reduction in the active oxygen content in the washing tank during pauses in dosing, even where a bleach-containing powder-form detergent is used. For the method mentioned at the beginning, the solution provided by the invention is characterized in that, where active oxygen is used as the bleach component, the active oxygen content in the washing tank is maintained during pauses in the dosing of detergent by maintenance dosing of the bleach. The maintenance dosing preferably takes place in individual dosing strokes.
Accordingly, one embodiment of the invention relates to maintenance dosing of the bleach during the stoppage times of the dishwashing machine between two successive rinse cycles. The effect of this maintenance dosing is that fresh bleach containing active oxygen enters the washing tank as the active oxygen content diminishes. Accordingly, the washing tank of the dishwashing machine is always kept in readiness for a new rinse phase and is therefore able immediately to supply dishwashing detergent containing sufficient bleach at the beginning of the rinse phase.
Another embodiment of the invention is characterized in that, where a detergent, particularly a powder-form detergent, basically containing sufficient bleach for immediate rinsing is used, bleach continues to be introduced into the washing tank as the active oxygen content decreases during the machine stoppage times or pauses in the dosing of detergent.
In addition to this maintenance dosing regime, a parallel bleach dosing regime is pre
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Odendahl Karl-Heinz
Pruehs Horst
Rings Friedel
Bell Mark L.
Chaudhry Saeed T.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
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