EP0094357A1

EP0094357A1 - Washing machine with a perfected resin regenerating process

Info

Publication number: EP0094357A1
Application number: EP83830089A
Authority: EP
Inventors: Marcello Premoli; Giuseppe Nerozzi
Original assignee: Indesit Industria Elettrodomestici Italiana SpA
Current assignee: Indesit Industria Elettrodomestici Italiana SpA
Priority date: 1982-05-07
Filing date: 1983-05-03
Publication date: 1983-11-16
Also published as: DE3365580D1; IT8267598A0; IT1156468B; EP0094357B1

Abstract

The present invention relates to a washing machine with a perfected resin regenerating process which essentially provides for washing with any type of hard water. In the case of medium-high hard water, softened water may be used throughout the wash cycle. Provision is also made for using a two-way electrovalve with only two hydraulic circuits.

Finally, the extent to which the resins are regenerated varies according to the amount of water used in the wash cycle. These results are archieved by providing for more powerful resin regeneration with the aid of a first additional regenerating stage, in the case of a normal wash cycle, and of a second additional regenerating stage, in the case of an intensive wash cycle.

Description

The present invention relates to a washing machine, with a perfected resin regenerating process, comprising a wash chamber, washing components and components for softening the water supplied from the mains.
It is a well known fact that, to obtain good results from a washing machine, hard water over a given maximum limit cannot be used, -at least in certain wash stages, and that, to remove the hardness in the water below the said limit, the said washing machines are provided with softeners.
It is also known that the said softeners consist essentially of a container filled with sulphonated resin granules through which the hard water is sent for softening.
The said resin reacts strongly with the calcium (Ca) and magnesium (Mg) ions in the water they come into contact with, thus reducing its hardness.
It is also known that, after coming into contact with a certain amount of water, the softening capacity of the resin falls, that the said resin must therefore be regenerated, that the said regenerating process consists in soaking the said resins with a high-concentration solution of sodium chloride (NaCl) and, finally, that the resin must then be washed.
In the case of dishwashing-machines, in particular, it is also known that the said hardness limit of the water that must not be exceeded is around 20°F (French degrees).
Known types of dishwashing-machines are usually fitted with a three-way electrovalve, a first for letting in hard water in certain wash stages, a second for letting in softened water in other wash stages and a third for letting in the water for regenerating the resin. On the said machines, the resin is regenerated during the dish-drying cycle and washed at the start of the next wash cycle.
These machines present a number of drawbacks : poor resin regenerating efficiency, the use of a three-way electrovalve and supply pipes for three hydraulic circuits and, more important the non-versatility of the regenerating system which removes the same amount of hardness from the water regardless of the wash cycle set by the user or the different hardness of water in different areas.
This is to say, the amount of hardness removed by a specific type of softner is strictly proportional to the amount of resin in the softener itself. Consequently, either the capacity of the latter is overestimated (an obvious waste both in terms of manufacturing and running expenses) or a limit placed on the hardness of the water that can be employed (which obviously limits the scope of the machine itself). To make this clearer, we should point out that the softening capacity of the resin, that is, the percentage of hardness removed, depends on the volume of resin inside the softener, on the volume of water and the speed at which it is loaded and the efficiency with which the resin is regenerated.
As already stated, on current dishwashing-machines, given the volume of the resin and the volume and loading speed of the water, softening efficiency depends essentially on how efficiently the resin is regenerated.
The resin is essentially regenerated in two stages : one dynamic (when the NaCl solution is poured into the resin container) and one static (when the said solution has settled inside the said container). Most of the regeneration process is performed in the dynamic stage, whereas static regeneration becomes gradually less effective as time goes by, so much so that, after two hours, it has practically no effect whatsoever.
With this taken into account, on certain of the latest known types of dishwashing-machines, the single regenerating operation has been replaced by a number of intermittent operations, all performed during drying time.
Though this provides for some improvement of resin regenerating efficiency, the said improvement is only small in that, though dynamic regeneration is increased (by increasing the number of operations) static regeneration remains the same (in that resin and NaCl solution remain in contact for the same length of time).
These machines therefore present more or less the same drawbacks as the previous ones. What is more, as, on both types of machine, static regeneration is mainly performed between the end of one washing operation and the start of the next one, if a new washing operation was started straight after the first, static regeneration would be very short and total regeneration efficiency insufficient.
Another point to note is that, if softened water is not made available for all the wash stages, there is a danger that water over the accepted hardness limit may also be supplied in the wash stages in which the said limit must not be exceeded. Though, at the end of a wash stage using hard water (e.g. 45°F) the said water is drained off, a certain amount is left inside the wash tub (1 1). When the softened water is added (e.g. 9 1 with 20°F hardness) the total hardness of the resulting mixture is over the accepted limit (about 23°F).
The aim of the present invention is therefore to overcome the above drawbacks by providing a washing machine with a perfected resin regenerating process which, by improving regeneration efficiency, provides essentially for using any type of hard water without having to overestimate the capacity of the softener; which removes the strict relationship between the amount of resin contained inside the softener and the amount of hardness removed, by adapting regenerating efficiency to the amount of water actually employed in a given wash cycle; which, in the case of medium-high hard water, provides for softening all the water needed for an entire wash cycle; and which provides for using a two-way electrovalve and, consequently, supply pipes for only two hydraulic circuits.
Further aims of the present invention are to reduce both material and manufacturing costs of the dishwashing-machine and to keep down running costs even in the case of very hard water.
With these aims in view, the present invention relates to a washing machine, with a perfected resin regenerating process, comprising a wash chamber, washing components and components for softening the water supplied from the mains, characterised by the fact that it comprises means which, without increasing the capacity of the softening components, ensure greater resin regenerating efficiency to the extent that the softening capacity of the softening components is such as to provide essentially for washing with any type of hard water.
The invention will now be described with reference to the attached drawings, supplied by way of a non-limiting example, and in which:

- Figs la, lb and 1c show softening efficiency graphs of various types of softeners under various operating conditions;
- Fig. 2a shows the wash cycle of a known type of dishwashing-machine;
- Fig. 2b shows the wash cycle of a dishwashing-machine using a first arrangement of the perfected resin regenerating process covered by the present invention;
- Fig. 2c shows the wash cycle of a dishwashing-machine using a second arrangement of the perfected resin regenerating process covered by the present invention;
- Fig. 3 shows part of the hydraulic circuit for performing the perfected resin regenerating process covered by the first arrangement of the present invention.

In the softening efficiency graphs in Figs la, 1b and 1c, the amount of water processed (Q) is expressed in litres on the Y axis and the percentage of residual hardness in the processed water coming from the softener shown on the X axis. The softening efficiency curves marked "a" refer to fully regenerated resin, whereas "b" and "c" are two of a family of softening efficiency curves relating to resin only partially regenerated and depending on resin regenerating efficiency.
Fig. la shows the graph of an ideal softener operating under ideal conditions, i.e. a very high cylindrical softener with a very small base, through which flows 50 Vol/Vol/h of water (i.e. the volume of water flowing through it in an hour is equivalent to 50 times the volume of resin it contains).
As can be seen from curve "a", up to processed water quantity Q1, the resin guarantees practically 0 residual hardness. The curve then starts to climb steeply, showing the resin is beginning to weaken, until it reaches a residual hardness of 100% at processed water quantity Q2, indicating that the resin is exhausted.
Curves "b" and "c" relative to partially regenerated resin and which follow the same trend as "a" show how the quantity of water that can be softened falls alongside the fall in resin regenerating efficiency.
Fig. 1b relates to the same ideal softener shown in Fig. 1a but with 700 Vol/Vol/h of water flowing through it (i.e. the volume of water flowing through it in one hour is equivalent to 700 times the volume of resin it contains). This is the amount of water with which current dishwashing-machines are usually filled.
Curve "a" shows how a certain amount of residual hardness is left even when very small quantities of water are processed and how the relative curve is less steep than the corresponding "a" curve in Fig, 1a.
Far from being a drawback, the fact that a certain amount of residual hardness remains is an advantage in that water with very little residual hardness could initiate corrosion of the metal parts inside the wash tub. What is more, a greater quantity of water can be processed with this type of curve.
Fig. 1c relates to the softener used in the present invention which consists of a cylindrical container with a base diameter to height ratio of around 1:2 and through which flows 700 Vol/Vol/h of water.
As can be seen from curve "a", residual hardness, even in the case of small quantities of processed water, is slightly higher than in the previous case and the curves are almost straight lines sloping gradually more steeply as resin regenerating efficiency diminishes.
The amount of processable water is even higher than that processable using the Fig. 1b softener.
The above Figures clearly show how the Fig. 1c softener better meets the practical water softening requirements of a dishwashing-machine and how, for a given type of softener, resin regenerating efficiency is essential from the standpoint of both maximum hardness and the maximum quantity of water that can be softened.
Fig. 2 shows a wash cycle on a known type of dishwashing-machine : number 1 indicates an intensive wash cycle, 2 a normal wash cycle, 3 the hot washing stage, 4 the first cold rinse, 5 the second cold rinse, 6 the third hot rinse, 7 the drying stage, letter "A" the resin regenerating stage, "B" the resin wash stage, "C" soft water fill and "D" hard water fill.
The wash cycle in Fig. 2a shows how the resin regenerating stage starts during the dish drying stage and continues until the next washing operation starts, how the resin wash stage is performed at the start of the next normal washing operation and how softened water is only loaded three times.
Dishwashing-machines using the said wash cycle and a softener containing 0.4 1 of ion-exchange resin are capable of softening 30 litres of water with a maximum hardness of 45°F. Static regeneration of the resin goes on for hours but, if a new washing operation is started straight after the end of the previous one, static regeneration only lasts the length of the drying stage (about 10 minutes) which is not long enough to ensure all the loaded water is softened properly. In other words, it could happen that, when soft water is loaded for the third time (for hot rinsing), the resin is exhausted and hard water would be loaded just when it should not be, i.e. just before drying in which stage the calcium (Ca) and magnesium (Mg) salts would cling to the dishes thus jeopardizing the success of the wash.
Finally, performing such a process according to the known technique requires a three-way electrovalve and three hydraulic circuits.
Other types of known diswashing-machines, again using a softener containing 0.4 1 of ion-exchange resin, provide for a number of regenerating pulses in the regenerating stage which results in a slight improvement in resin regeneration. The said machines, in fact, can soften as many as 40 litres of water with 45°F hardness.
Fig. 2b shows a wash cycle on a diswashing-machine using a first arrangement of the perfected resin regenerating process covered by the present invention; the cycles and wash stages common to Fig. 2a are shown using the same letters and numbers.
As can be seen in the Fig. 2b cycle, all loading is done using softened water. Also, provision has been made for two extra regenerating pulses as compared with the Fig. 2a cycle, one after water is loaded in intensive cycle 1 and one after water is loaded in hot wash 3 of normal cycle 2.
The resin is washed at the end of the drying stage, when water is loaded during cold prewash 2 and when water is loaded during first cold rinse 4.
To explain how the wash cycle works, we shall begin from the start of stage 7: during the dish drying stage, three regenerating pulses are performed, which consist in sending 0.1 1 of NaCl solution into the softener in 20", followed by a 1' pause. A fourth 20" supply of 0.1 1 of NaCl is then sent, followed by a pause which lasts until the end of the drying stage (about 5'). At the end of the drying stage, the resin is washed by flushing the softener with 7 1 of water and draining off the water containing the regeneration products (sodium and calcium chloride ions) directly, i.e. without sending it into the wash tub, by means of a plastic dam and a drain pump. The resin is now ready for softening water again. When starting, for example, with a normal cycle 2, at the start of the next wash, just after the water has been loaded, a first additional regenerating stage is performed, which consists in sending 0.1 1 of NaCl solution to the softener for 20", followed by a pause which lasts throughout hot wash 3 (about 20').
The said first additional regenerating stage is highly effective in that it combines dynamic regenerating efficiency with static regeneration lasting 20' which also provides a large contribution. After the water used for hot wash 3 has been drained off, water is loaded for first cold rinse 4 which, flowing through the softener, also washes the resin. Though the water containing the products of resin regeneration goes into the wash tub, it causes no damage to the metal parts inside the tub as it only stays there until after first cold rinse 4 (about 1') and the concentration of the regeneration products in it are very low (0.1 1 of solution in 7 1 of water).
If, on the other hand, the next wash cycle is an intensive one 1, besides the first additional regenerating stage already described, a second additional regenerating stage is performed straight after water is loaded for hot prewash 1, which also consists in sending 0.1 of NaCl solution to the softener for 20", followed by a pause lasting throughout hot prewash 1 (about 20'). The said second additional regenerating stage is also highly effective for the same reasons mentioned above. After the water used for hot prewash 1 has been drained off, water is loaded for cold prewash 2 which, passing through the softener, also washes the resin. The water containing the products of resin regeneration goes into the wash tub but, as explained previously, no damage is done to the metal parts in the tub for the reasons already given.
In other words, besides regenerating the resin at the end of the cycle, provision is made for an additional regenerating stage in the case of a normal wash cycle and two additional regenerating stages in the case of an intensive cycle. If, on the other hand, the cycle is started with a rinse stage (4 or 5 or 6) no additional regeneration is performed.
In other words, the extent to which the resin is regenerated is proportional to the number of times water is loaded and, therefore, to the amount of water used for washing the dishes.
As shown in Fig. 2b cycle, since only softened water and water for washing the resin is expected to be coming in, a two-way electrovalve and two hydraulic circuits are sufficient for the purpose. Also, there is absolutely no danger of wash cycles being performed with hard water over the accepted maximum limit.
Tests have shown that diswashing-machines using the present perfected resin regenerating process and a softener containing 0.4 1 of ion-exchange resin can soften 60 1 of water with roughly 55°F hardness.
Figure 2c shows a wash cycle on a diswashing- machine using a second arrangement of the perfected resin regenerating process covered by the present invention. Cycles and wash stages common to Figs 2a and 2b are marked using the same letters and numbers.
The cycle shown in Fig. 2c can be said to be a combination of those shown in Figs 2a and 2b, that is, in certain stages of the wash cycle, the machine is loaded with hard water, whereas in others it is loaded with soft water as in the Fig. 2a cycle. The additional regenerating stages are also performed as in the Fig. 2b cycle. Resin regeneration is therefore strengthened, as in the Fig. 2b cycle, whereas the softened water requirement is that of the Fig. 2a cycle, i.e. about 301. Consequently, a dishwashing-machine using this second arrangement of the perfected resin regenerating process and a softener containing 0.4 1 of ion-exchange resin is capable of softening water with around 70°F hardness.
The said second arrangement, of course, needs a three-way electrovalve but this extra cost is compensated by the possibility of softening very hard water which otherwise could not be used in a dishwashing-machine. The significance of this second arrangement will become clearer if we consider that 70°F is practically the maximum hardness allowed in water employed in dishwashing-machines.
Water harder than this poses other problems, such as high salinity which, without prior demineralization, would jeopardize washing results both in the wash stage itself (saponification) and the rinsing stage.
We can safely say, therefore, that, with the said second arrangement of the present invention, dishwashing-machines in particular and washing machines in general can be operated with practically any type of hard water.
Needless to say, depending on whether the first or second arrangement is selected, the timer controlling operation of all the parts on the dishwashing-machine must be designed so as to control the first stage arrangement - water loading, softening, resin regeneration and wash - or the second.
Fig. 3 shows a diagram of the hydraulic circuit on a dishwashing-machine using the first arrangement of the perfected resin regenerating process covered by the present invention. It comprises a mains water inlet pipe 10 to which is connected a two-way (E and E₂) electrovalve 11.
The first way (E₁) on electrovalve 11 is connected to one end of pipe 12 the other end of which is connected to a first inlet on cylindrical softener 13 which contains ion-exchange resin granules of about 1 mm in diameter, not shown in the Figure. The second way (E₂) of electrovalve 11 is connected to one end of pipe 14 the other end of which is connected to the inlet of container 15 filled with salt. The outlet of salt container 15 is connected to one end of pipe 16 the other end of which is connected to a second inlet on softener 13.
The outlet of softener 13 is connected to one end of pipe 17 the other end of which is connected to the inlet of a wash tub 18 on a dishwashing-machine comprising a wash pump 19 and a water drain pipe 20.
The device shown in Fig. 3, controlled by a timer not shown in the Figure operates as follows:

When water is loaded into wash tub 18 (or the resin is washed) way E on electrovalve 11 is open and water from the mains flows into softener 13 along pipe 12, is softened (or washes the resin) and flows into wash tub 18 along pipe 17. During regeneration, way E₂on electrovalve 11 is open and water from the mains flows into salt (NaCl) container 15 along pipe 14. The NaCl solution formed when the said water flows into the said container 15 flows into softener 13 along pipe 16 so as to regenerate the resin inside the softener.

The advantages of the washing machine with the perfected resin regenerating process covered by the present invention will be clear from the description given.
In particular, greater resin regenerating efficiency, more flexible resin regeneration proportional to the amount of water actually used in the wash cycle, the possibility of washing with practically any type of hard water, the possibility of using softened water in all the wash cycle stages, the possibility of using a two-way electrovalve and only two hydraulic circuits and, finally, lower cost for manufacturing and running the said dishwashing-machine.

Claims

1. Washing machine with a perfected resin regenerating process, comprising a wash chamber, washing components and components for softening the water supplied from the mains, characterised by the fact that it comprises means which, without increasing the capacity of the softening components, ensure greater resin regenerating efficiency to the extent that the softening capacity of the softening components is such as to provide essentially for washing with any type of hard water.

2. Washing machine with a perfected resin regenerating process according to Claim 1, characterised by the fact that the said means are designed so that the said increase in resin regenerating efficiency and, consequently, the softening capacity of the said softening components varies according to the amount of water actually used in a given wash cycle.

3. Washing machine with a perfected resin regenerating process according to Claim 2, characterised by the fact that, during the wash cycle, the said means perform at least two resin regenerating operations in two separate stages of the said wash cycle.

4. Washing machine with a perfected resin regenerating process according to Claim 3, characterised by the fact that, when the user selects a normal wash cycle, the said means enable, alongside a resin regenerating stage at the end of the wash cycle, at least a first additional resin regenerating stage which is performed at the start of the wash cycle so as to increase regenerating efficiency and, consequently, the softening capacity of the softening components.

5. Washing machine with a perfected resin regenerating process according to Claim 4, characterised by the fact that, when the user selects an intensive wash cycle, the said means enable at least a second additional resin regenerating stage which is performed during the wash cycle before the said first additional resin regenerating stage, so as to increase regenerating efficiency even further and, consequently, also the softening capacity of the softening components.

6. Washing machine with a perfected resin regenerating process according to Claim 4, characterised by the fact that the said first additional resin regenerating stage is performed after water is loaded for hot washing (3).

7. Washing machine with a perfected resin regenerating process according to Claim 5, characterised by the fact that the said second additional resin regenerating stage is performed after water is loaded for hot prewashing (1).

8. Washing machine with a perfected resin regenerating process according to Claim 6 and/or 7, characterised by the fact that the water loaded after the said first and/or second additional resin regenerating stage also washes the resin and removes the regenerating products.

9. Washing machine with a perfected resin regenerating process according to Claim 4, characterised by the fact that the said resin regenerating operation performed at the end of the wash cycle is intermittent, comprising dynamic and static stages, and is followed by washing of the resin.

10. Washing machine with a perfected resin regenerating process according to Claim 9, characterised by the fact that the ratio between the dynamic and static stages is roughly 1 to 3.

11. Washing machine with a perfected resin regenerating process according to Claim 10, characterised by the fact that the dynamic stage of the said intermittent regeneration lasts at least 10", that the said static stage of the said intermittent regeneration lasts at least 30" and that the said dynamic stages are more than two in number.

12. Washing machine with a perfected resin regeneration process according to Claims 6 and 7, characterised by the fact that the dynamic stage of the said first and second additional resin regenerating stage lasts at least 10" and that the static stage of the said first and second additional resin regenerating stage lasts at least 10'.

13. Washing machine with a perfected resin regenerating process according to Claim 1, characterised by the fact that the said means are designed to regenerate the resin so as to enable softening of about 30 1 of water with 70°F hardness.

14. Washing machine with a perfected resin regenerating process according to Claim 13, characterised by the fact that the said means comprise a timer, for controlling the number of resin regenerating operations and the sequence in which they are performed, as well as a three-way electrovalve.

15. Washing machine with a perfected resin regenerating process according to Claim 1, characterised by the fact that the said means are designed so that, when using medium-high hard water, they provide for increasing resin regenerating efficiency to such an extent that the softening components can soften all the water needed for an entire wash cycle.

16. Washing machine with a perfected resin regenerating process according to Claim 1, characterised by the fact that the said means regenerate the resin so as to enable roughly 60 1 of water with up to 55°F hardness to be softened.

17. Washing machine with a perfected resin regenerating process according to Claim 15, characterised by the fact that the said means comprise a timer, for controlling the number of resin regenerating operations and the sequence in which they are performed, as well as a two-way electrovalve (11).

18. Washing machine with a perfected resin regenerating process according to Claim 17, characterised by the fact that, when water is being loaded, a first way (E ) on the said electrovalve (11) is opened, the hard water flows along a first pipe (12) into a container (13) containing the said resin, is softened and then flows into the said wash chamber (18) along a second pipe (17).

19. Washing machine with a perfected resin regenerating process according to Claim 17, characterised by the fact that, during the dynamic stage σf the said resin regenerating operations, a second way (E₂) on the said electrovalve (11) is opened, water from the mains flows along a third pipe (14) into a salt container (15) and a solution of sodium chloride flows along a fourth pipe (16) into a container (13) filled with the said resin which is thus regenerated.

20. Washing machine with a perfected resin regenerating process according to any one of the previous Claims, characterised by the fact that the machine is a dishwashing-machine.