EP0995828A1

EP0995828A1 - A washing cycle for washing machine

Info

Publication number: EP0995828A1
Application number: EP98830621A
Authority: EP
Inventors: Silvano Fumagalli
Original assignee: Candy SpA
Current assignee: Candy SpA
Priority date: 1998-10-19
Filing date: 1998-10-19
Publication date: 2000-04-26
Anticipated expiration: 2018-10-19
Also published as: DE69829052D1; DE69829052T2; EP0995828B1; ES2237833T3

Abstract

The present invention relates to a novel bleaching washing cycle for wash-fast items, for washing machines.

More particularly, the present invention relates to a washing cycle for wash-fast items for washing machines comprising:

a bleaching stage, and
at least one washing stage,
characterized in that the bleaching stage is performed before the at least one washing stage. The bleaching stage is preferably performed with bleach.

Description

The present invention relates to a novel bleaching washing cycle for wash-fast items, for washing machines.
The use of bleaching and disinfectant additives in washing machines is widely known.
However, one of the additives most often used, that is, sodium perborate, has shown poor efficiency in normal washing cycles, particularly in the 60°C washing cycle which is most often used. In fact, only 30-40% of the sodium perborate is actually utilized, whilst the remaining quantity is discharged during the various rinses.
It is therefore necessary to establish a washing cycle characterized by greater efficiency, particularly for especially dirty items which have persistent stains for which the use of normal detergents is not sufficient.
Bleach, which is a solution of sodium hypochlorite, is a strong oxidizing agent which can attack and remove even the most persistent stains. The use of bleach in washing cycles for washing machines is known. In known washing cycles, the bleach is taken in after or during the first rinse. It has been found that, although this method of operation is advantageous from the point of view of the economy of the process, it has some disadvantages.
In the first place, laboratory tests have shown that, at the moment when the bleach is added, 25-30% of the initial quantity of sodium perborate is still present in the washing machine. The sodium hypochlorite therefore reacts chemically therewith, to the detriment of its own effect.
Moreover, it has been found that sodium hypochlorite interferes with the optical whitening agents which are already partially fixed to the fabrics during washing and which are thus degraded, causing the yellowing phenomenon.
It has also been found that any shifting of the addition of bleach to subsequent rinses does not solve the above-mentioned problems. Although interference with sodium perborate is in fact reduced, interference with the optical whiteners is increased and this greatly affects the final whiteness of the laundry. A further disadvantage in the latter case is that the bleach goes through a smaller number of rinses and is therefore not completely removed. As a result, it has been found that fabrics thus treated do not lose the unpleasant odour typical of bleach and, what is more, are damaged in the long term by the prolonged bleaching action.
The problem upon which the present invention is based is to achieve a bleaching washing cycle which does not have the problems encountered in the known washing cycle.
This problem is solved by the establishment of a cycle for washing wash-fast items for washing machines comprising:

a bleaching stage, and
at least one washing stage,
characterized in that the bleaching stage is performed before the at least one washing stage.

A bleach is usually used in the bleaching stage.
The introduction of the bleaching stage using bleach has various advantages. In contrast with peroxide oxidizing agents (for example, sodium perborate), bleach can also be used in washing conditions which are not ideal, for example, at low temperatures, in the presence of hard water, and with relatively short treatment times. Bleach also has a considerable bactericidal effect even at low temperature. Treatment with bleach therefore has a disinfectant effect as well as eliminating persistent stains.
It has been found that the use of bleach enables the consumption of detergent in the subsequent washing stage to be reduced and the use of further additives (perborate or percarbonate) possibly to be avoided with better results, a lower cost, and a certain advantage at the environmental level (contamination of waste water).
The provision of this bleach treatment before the actual washing stage thus enables the bleach to perform to the maximum its dual effect of removing stains and disinfection.
It has also been noted that loads to be subjected to pre-washing and loads to be subjected to bleaching are fully compatible, in the sense that both require a pre-treatment (bleaching or pre-washing) followed by an actual washing (or prolonged washing) stage. The selection of the bleaching stage or of the pre-washing stage is dictated substantially by the specific resistance to bleaching of the items to be washed.
A further advantage of the washing cycle of the present invention is therefore that the bleaching stage may be replaced by a pre-washing stage simply by loading the appropriate container of the washing machine with the pre-washing detergent instead of with bleach. In this case, the respective reservoir should be dual-purpose.
This ability to interchange the two types of treatment - pre-washing and bleaching - according to requirements, which constitutes a preferred characteristic of the washing cycle of the present invention, increases the versatility of the washing machine.
The washing cycle of the present invention preferably also comprises a rinsing stage and a spinning stage upon completion of the bleaching stage.
The use of these rinsing and spinning stages after bleaching has the advantage of almost completely removing the bleach present in the fabrics, thus preventing all of the above-described problems of interference with the other additives and damaging prolongation of the bleaching action. Water containing the dirt removed by the bleach is thus eliminated, rendering subsequent washing more efficient.
The quantity of bleach usable in the bleaching stage may vary between 100 and 250 ml of commercial solution, enabling between 82 and 100% of the dirt to be removed.
The temperature and the washing time are two parameters which affect the efficiency of the bleaching stage. In general, the longer the bleaching time is, the lower the bleaching temperature can be. The preferred washing cycle comprises a bleaching stage lasting for about 12 minutes and a bleaching temperature of about 40°C.
According to a preferred aspect, the washing cycle provides for an automatic continuation from the bleaching stage to the washing stage, in accordance with the programme set on the programmer.
Alternatively, the washing cycle comprises a stop stage between the bleaching stage and the washing stage. The term "stop stage" is intended to define herein a stage in which the washing machine stops and can be re-started only by manual operation. Conversely, the absence of a stop stage means that the continuation from the bleaching stage to the washing stage takes place automatically.
The provision of the stop stage in the washing cycle enables the user to load, at this point - that is, immediately before the actual washing stage - any items which do not require a bleaching treatment, or for which such treatment would be damaging (delicate and/or coloured items).
A further advantage of the insertion of the stop stage is that the bleaching (or pre-washing with detergent instead of bleach) can be used as a short or quick-washing programme. Naturally, in this case, the rinsing and spinning stages are essential.
These programmes can be operated by the use of buttons and selectors which enable the rinsing and spinning stage to be excluded, according to requirements, thus prolonging the pre-washing stage.
In the washing cycle of the present invention, the actual washing stage may be a normal wash at at least 60°C (or possibly 90°C) or a low-temperature wash (at about 40°C). In the latter case, the washing times may be extended according to need. For example, an extended washing programme with a washing time of between 6 and 12 hours may be performed.
In order to implement the washing cycle of the present invention, the washing machine should have some essential characteristics. For example, a bleach reservoir (a sealed reservoir) having sufficient capacity to hold 250 ml of bleach must be provided in the compartment for the supply of detergents and additives. Moreover, a device must be provided for instantaneously mixing water with the bleach so that the bleach does not come directly into contact with the laundry, causing damage to the fabrics. A device which can advantageously be used for this purpose is that described in European patent filed in Italy under the number 25725BE/95 which is incorporated herein by reference.
The washing cycle of the present invention is described further by way of non-limiting example, by means of the following drawings:
Figure 1 is a graph of time (on the abscissa) / temperature (on the ordinate), for a washing cycle according to the present invention having intermediate rinsing and spinning stages, without a stop stage,
Figure 2 shows the graph of Figure 1 in which a stop stage has been inserted,
Figure 3 shows the graph of Figure 1 in which the washing stage is performed at low temperature.
The washing cycle shown in the graph of Figure 1 comprises:
a) a stage for filling with water and bleach (or alternatively pre-washing detergent), the duration of which is limited, by way of example, to 2 minutes,
b) a stage for instantaneous heating from ambient temperature to 30°C,
c) a bleaching stage of about 12 minutes' duration, in which the temperature is gradually raised to about 40°C,
d) a water-discharge stage in which the temperature falls to about 30°C.
e) a stage for filling with clean rinsing water, in which the temperature falls approximately to the temperature of the mains water,
f) a stage far the discharge of the rinsing water,
g) a spinning stage. At this point, the bleaching treatment is completed and the washing cycle provides for subsequent automatic continuation to the actual washing stage. This washing cycle therefore gives preference to the automatic working of the programme, to the detriment of its versatility.The washing stage comprises:
h) a stage for filling with washing water and detergent,
i) a washing stage of variable duration in which the temperature is raised from ambient temperature to 60°C.
l) discharge and rinsing stages as described above; these treatments, followed by a final spin, which are not shown in the graph, complete the washing cycle.
Moreover, the intermediate rinsing and spinning stages are provided for only in the case of bleaching. If a pre-washing stage is required instead of bleaching, the programme continues by extending the pre-washing stage and going on directly and automatically to the subsequent washing stage.
The washing cycle shown in Figure 2 is the same as that of Figure 1 with the difference that a stop stage has been inserted after the bleaching. This stop stage permits the loading of delicate items which would not have been able to withstand the initial bleaching stage.
The washing cycle shown in Figure 3 is the same as that of Figure 1 with the difference that the actual washing stage is performed at temperatures no greater than 40°C and can be extended even for a very long time (from 6 to 12 hours).
As shown in Figures 1 and 3, the washing cycle which provides for the bleaching, rinsing, spinning and subsequent washing stages may be interchanged with a washing cycle which provides solely for a pre-washing stage and subsequent actual washing. It is thus possible to establish a programme for washing machines which enables the two washing cycles to be selected according to requirements by means of suitable selectors and push-buttons for excluding rinsing/spinning and setting of the temperature. It should be noted that, in this case, the pre-washing must occupy the same time interval as is used to perform the bleaching, rinsing and spinning stages; an expanded pre-washing stage very advantageously results.
A further subject of the present invention is therefore the provision of a washing machine operating with a programme which permits the selection of a washing cycle with an initial bleaching stage as described above or, alternatively, a washing cycle with an expanded pre-washing stage.
Moreover, the washing machine may comprise only three reservoirs for the withdrawal of detergents: one for the bleach or for the pre-washing detergent, one for the washing detergent, and one for additives. As stated above, the bleach reservoir should have a capacity of at least 250 ml and should be leaktight. This reservoir may also be a normal tray which can be transformed into a leaktight reservoir by the insertion of a leaktight adaptor therein.
Alternatively, the washing machine may comprise four reservoirs, but with the condition that one of the first two adjacent reservoirs in the sequence performed by the programme will be a leaktight bleach reservoir.

Claims

A washing cycle for wash-fast items for washing machines comprising:

a bleaching stage, and

at least one washing stage,
characterized in that the bleaching stage is performed before the at least one washing stage.
A washing cycle according to Claim 1, comprising, in addition, a rinsing stage and a spinning stage, after the bleaching stage.
A washing cycle according to Claim 1 or Claim 2, in which the bleaching stage is performed with from 100 to 250 ml of bleach.
A washing cycle according to Claims 1 to 3, in which the bleaching stage has a duration of about 12 minutes and is performed at a temperature of about 40°C.
A washing cycle according to Claims 2 to 4, comprising, in addition, a stop stage between the bleaching stage and the at least one washing stage.
A washing cycle according to Claims 1 to 5, in which the at least one washing stage is performed at a temperature of at least 60°C.
A washing cycle according to Claims 1 to 5, in which the at least one washing stage is performed at a temperature of about 40°C.
A washing cycle according to Claim 7, in which the at least one washing stage is performed for a period of from 6 to 12 hours.
A short cycle for washing wash-fast items for washing machines, comprising, in order:

a bleaching stage,

a rinsing stage,

a spinning stage,

a stop stage.
A short washing cycle according to Claim 9, in which from 100 to 250 ml of bleach is used in the bleaching stage.
A washing machine operating with a programme which permits the selection of a washing cycle as claimed in Claims 1 to 10 or, alternatively, a washing cycle with an expanded pre-washing stage.
A washing machine according to Claim 11, comprising three reservoirs for the withdrawal of detergents and/or additives.
A washing machine according to Claim 12, in which one of the reservoirs, for holding the bleach or pre-washing detergent, has a capacity of at least 250 ml and is leaktight.