EP2138087A1

EP2138087A1 - Dishwasher and method for letting water into a dishwasher

Info

Publication number: EP2138087A1
Application number: EP08011653A
Authority: EP
Inventors: Alf Johansson
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2008-06-27
Filing date: 2008-06-27
Publication date: 2009-12-30

Abstract

A multi-compartment dishwasher (1) comprising a first washing compartment (10), having a first washing tub (13) for receiving objects that are to be washed, and a first water inlet (11), for leading water into the first washing compartment (10) from a water supply system (2), a second washing compartment (20), having a second washing tub (23) for receiving objects that are to be washed, and a second water inlet (21) for leading water into the second washing compartment (20) from the water supply system (2).

A control unit (30), operatively associated with the first and second washing compartments (10, 20) is arranged for controlling the first and second water inlets (11, 21), such that at any given instant, at the most one water inlet (11,21) lets water into its corresponding washing compartment (10, 20).

Description

Technical field

The present invention relates to multi-compartment dishwashers and methods for letting water into such a dishwasher.

Background

In general, multi-compartment dishwashers are well-known. Typically, a multi-compartment dishwasher has several pull-out drawers, slidably mounted in a cabinet.
In most multi-compartment dishwashers, each washing compartment comprises a washing tub that is arranged to receive the dishes to be washed, a water circulation unit that can perform a washing operation in the washing tub and a water inlet for leading water into the washing compartment from an external water supply, such as a domestic water supply system. A multi-compartment dishwasher is generally arranged such that a washing operation can be performed in only one of the washing compartments, or in several washing compartments simultaneously. A washing operation normally comprises a water intake procedure, leading water into the washing compartment via the water inlet, a washing procedure, and a drain procedure for discharging water from the washing compartment. These procedures may be performed more than once before a drying procedure for drying the cleaned dishes is performed.
It is essential that enough water is admitted into the washing compartment during a water intake procedure, for enabling a satisfactory washing result in the following washing procedure. On the other hand, there is also a request to use as little water as possible during a washing operation, for economic reasons as well as for minimizing the environmental influence of the dishwasher.
For multi-compartment dishwashers, it has been observed that, in some cases, too little water is admitted into a washing compartment during the water intake procedure, or that the water intake procedure is very time-consuming.
Consequently, there is a need for a multi-compartment dishwasher that provides a safe and efficient water intake procedure at a low cost.

Summary

An object of the invention is to provide a multi-compartment dishwasher that provides an efficient and cost-efficient intake of water into each washing compartment, which intake of water is also safe, i.e. securing that an adequate volume of water is let into each washing compartment before a washing procedure is performed.
Another object of the invention is to provide a method for letting water into a multi-compartment dishwasher that provides a safe, efficient and cost-efficient intake of water into each washing compartment.
The invention is based on the observance that the water pressure may be lowered during intake of water if water is let into more than one washing compartment simultaneously, resulting in a water intake procedure that is undesirably time-consuming or a water intake procedure that does not admit enough water into the washing compartment.
According to a first aspect of the invention, it is secured that an adequate volume of water is let into a washing compartment of a multi-compartment dishwasher by providing a multi-compartment dishwasher according to the preamble of claim 1 where a control unit is arranged for controlling the first and second water inlets such that at any given instant, at the most one water inlet lets water into its corresponding washing compartment.
Since not more than one water inlet at a time is leading water into a washing compartment, the problems concerning reduced water pressure and water flow, that would arise if several inlets would let water into the dishwasher simultaneously, are avoided. Accordingly, since water pressure is more constant, it will be easier to control that an adequate volume of water has been provided.
The arrangement provides an efficient water intake procedure in a multi-compartment dishwasher, since a maximum flow of water is introduced to fill a selected washing compartment, thereby allowing the start of a desired washing operation to occur in a short time period. Once the water intake procedure is finished, the washing operation can begin and, another washing compartment may start its water intake procedure.
Furthermore, in a multi-compartment dishwasher, each washing compartment may be connected to the water supply via a common hose that branches into the water inlet of each washing compartment. If several washing compartments would need water simultaneously, it may also be difficult to secure adequate intake of water since the dimensions of the common hose may limit the intake of water. By assuring that not more than one water inlet at a time is leading water into a washing compartment, according to the invention, adequate intake of water is more easily secured.
According to an embodiment of the invention, the control unit is arranged to control at least one of the first and second water inlets to let water into its corresponding washing compartment for a predetermined time interval. Since a substantially constant water pressure is achieved by the invention, the amount of water let into a washing compartment during a water intake procedure could be controlled by controlling the time that water is let into a washing compartment, i.e. the time that an inlet valve of the water inlet is open. Accordingly, no flow meters or other arrangements for measuring the amount of water let into the washing compartment would be necessary. As a result, a cost-efficient water intake procedure is achieved. Also, in modern dishwashers the water volumes are rather low, for which reason, it may be difficult to use flow meters for measuring the amount of water passing through the water inlet anyhow.
Although, even if a constant water pressure is assured for normal circumstances by the invention according to claim 1, it may be necessary to measure the amount of water let into the water inlet anyhow, to secure that there is enough water in the washing compartment. Reasons for such a measurement may be if water pressure in the water supply system is lowered such that the water pressure for water passing through the water inlet is lowered, or to detect if there is anything wrong with the water intake procedure. For this reason, the dishwasher has, according to an embodiment of the invention, an arrangement for detecting an amount of water in the washing compartment. According to a preferred alternative of this embodiment, the arrangement for detecting an amount of water in the washing compartment comprises a blind pipe arranged in communication with the circulation pump, and a pressure detecting device arranged for detecting an air pressure in the blind pipe. This pressure detecting device can e.g. be a high pressure cut out.
According to an embodiment of the invention, the control unit is arranged to control the water inlets such that the first water inlet takes precedence over the second water inlet. By organizing the washing compartments in such a hierarchical manner, the time needed to perform a water inlet procedure in the washing compartment having the highest priority will be easy to predict, since that water inlet procedure may not be interrupted and will always be allowed to start.
According to another embodiment of the invention, the control unit is arranged to control the inlets such that the first water inlet is allowed to start leading water into its corresponding washing compartment only if the second water inlet is not leading water into its corresponding washing compartment, and vice versa. By organizing the washing compartments in such a way, a water inlet that is letting water into its corresponding washing compartment may not be interrupted.
According to a second aspect of the invention, there is provided a method for letting water into a multi-compartment dishwasher according to the preamble of claim 9, the method comprising the step of controlling the first and second water inlets such that at any given instant, at the most one water inlet lets water into its corresponding washing compartment.
By letting the step of controlling the water inlets comprise the step of controlling each inlet to let water into its corresponding washing compartment for a predetermined time interval, the procedure of letting water into a washing compartment can be performed in a cost-efficient way.
According to an embodiment of the second aspect of the invention, the step of controlling a water inlet comprises the step of starting the circulation pump before the step of detecting the amount of water in the corresponding washing compartment. When the circulation pump is running, the step of detecting the amount of water is facilitated since this step can be performed by means of e.g. a high pressure cut-out, which provides measurements that are precise, also at low water levels.
According to another embodiment of the second aspect of the invention, the step of controlling the water inlet comprises the step of restarting the water intake procedure if there is to little water in the washing compartment when the water intake procedure is finished. Consequently, the water inlet may use several attempts for letting water into its corresponding washing compartment.
According to yet another embodiment of the second aspect of the invention, the method comprises the step of terminating an ongoing water intake procedure when a predetermined time limit is passed. The time-limit restricts the number of attempts that are allowed, or the total time allowed for performing a water intake procedure, and ensures that the water intake procedure will not get stuck in an endless loop.

Brief Description of the Drawings

Embodiments of the present invention will be described in more detail hereinafter, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side view of a cross section of a washing compartment.
Fig. 2 is a schematic block diagram of a multi-compartment dishwasher according to the invention.
Fig. 3 is a flow chart showing a method for performing a water intake procedure in a washing compartment of a dishwasher according to the present invention.

Description

The invention deals with a multi-compartment dishwasher, such as a drawer-type dishwasher. For the sake of simplicity, a dishwasher having two washing compartments is described in this disclosure, but the number of washing compartments may also be three or more.
Each washing compartment is capable of independent operation such that a user may operate one or both washing compartments depending on a particular need.
Fig. 1 shows in cross-section a schematic side view of a multi-compartment dishwasher 1, having two washing compartments 10, 20. A washing compartment 10, 20 may be configured as a pull-out drawer which is slidably mounted in a cabinet (not shown). Dishwashers in which the washing compartments 10, 20 are configured as drawers are generally known as drawer-type dishwashers.
Each washing compartment 10, 20 has a washing tub 13, 23 for receiving dirty dishes or other objects that are to be washed. A filter portion 13b, 23b is provided in a lower part of the washing tub 13, 23. The filter portion is positioned above a sump 13c, 23c, which is formed in the lower part of the washing tub 13, 23, such that the filter portion 13b, 23b separates the sump 13c, 23c from an upper dish receiving part 13a, 23a of the washing tub.
A washing operation is performed in a washing compartment 10, 20, in order to clean the dishes in the washing tub 13, 23. A washing operation comprises several procedures. The dishes are cleaned during a washing procedure, preceded by a water intake procedure 100 which is performed for admitting an adequate quantity of water into the washing compartment 10, 20 for use during the washing procedure. Other procedures that can be included in a washing operation are e.g. a heating procedure for heating water that is used to wash the dishes, a drain procedure for discharging water from the washing compartment 10, 20, and a drying procedure for drying the cleaned dishes.
A dishwasher according to the invention has a tubular conduit, such as a hose 3 that is connected to an external water supply, such as a domestic water supply system 2. The hose branches into separate branches 3a, 3b, one for each washing compartment 10, 20.
Each branch 3a, 3b leads to a water inlet 11, 21 which is arranged to perform a water intake procedure 100, i.e. admit water, from the water supply system 2, into the washing tub 13, 23. The water inlet 11, 21 comprises a first tubular part, e.g. a first hose 11a, 21a, an inlet valve 11b, 21b, and a second tubular part, e.g. a second hose 11c, 21c. The first hose 11a, 21a establishes a fluid connection between the hose 3 that is connected to the water supply system and the upstream side of the inlet valve 11b 21b. The second hose 11c, 21c fluidly connects the downstream side of the inlet valve11b, 21b and the washing tub 13, 23.
Each washing compartment 10, 20 has a water circulation unit 12, 22, arranged for establishing a flow of water in the washing compartment 10, 20 during a washing procedure. Each water circulation unit 12, 22 comprises a circulation pump 16 ,26 which is driven by a motor (not shown). The upstream side of each circulation pump 16, 26 is fluidly connected to the sump 13c, 23c in the washing tub 13, 23, whereas the downstream side of each circulation pump 16, 26 is connected to a conduit 17, 27, which is in communication with a sprinkler 18, 28 positioned in the washing tub 13, 23.
During a washing procedure in either of the washing compartments 10, 20, the circulation pump 16, 26 sucks water from the sump 13c, 23c and propels it into the conduit 17, 27. Water in the conduit 17, 27 is further guided into the sprinkler 18, 28 in the washing tub 13, 23, and from the sprinkler 18, 28, it is sprayed onto the dishes in the upper part 13a, 23a of the washing tub 13, 23. Water then returns to the sump 13c, 23c through the filter portion 13b, 23b, to be recirculated back to the washing tub 13, 23 by the circulation pump 16,26.
The dishwasher may also have a drainage pump (not shown) for pumping water out of the washing machine during a drain procedure.
Several water intake procedures 100 are generally performed during the course of a washing operation. Each water intake procedure 100 must be successfully completed before starting the following procedure in the washing operation.
In accordance with the present invention, the dishwasher 1 includes a control unit 30 (see Fig. 2) which is operatively connected to the two washing compartments 10, 20. The control unit 30 controls the course of the washing operations in the washing compartments 10, 20, as well as the different procedures performed during a washing operation.
According to the embodiment shown in Fig. 2, the control unit 30 comprises several sub control units 31, 32 for controlling the different washing compartments 10, 20. The first sub control unit 31 is operatively connected to the first washing compartment 10 and the second sub control unit 32 is operatively connected to the second washing compartment 20. For enabling communication between the sub control units 31, 32, which communication allows mutual adaptation of the washing operations of the different washing compartments 10, 20, there is a communication link 33 between the sub control units 31, 32. The communication link can take various forms, such as a wire line link or a wireless link.
This disclosure deals with the way the control unit 30 controls the water intake procedures 100 of the different washing compartments 10, 20 in a multi-compartment dishwasher 1.
If, for some reason, water pressure is low in the water inlets 11, 21, it may be difficult to secure that an adequate volume of water is admitted into each washing compartment 10, 20 via its water inlet. Furthermore, the inlet valves need a certain water pressure to be able to close correctly. It has been observed that the water pressure is lowered during intake of water if water is let into more than one washing compartment 10, 20 simultaneously, resulting in a water intake procedure that is undesirably time-consuming.
Therefore, in a dishwasher according to the present invention, the control unit 30 is arranged to control the different water inlets 11, 21 such that, at any given moment, not more than one water inlet 11, 21 is admitting water into its corresponding washing tub 13, 23. Since not more than one water inlet 12, 22 at a time is leading water into a washing compartment at a time, the problems concerning reduced water pressure and water flow, that would arise if several inlets 12, 22 would let water into the dishwasher simultaneously, are avoided. Accordingly, since water pressure is more or less constant, the water intake procedure 100 will require approximately the same time, and it will be easier to control that an adequate volume of water has been provided.
The arrangement provides an efficient water intake procedure in a multi-compartment dishwasher, since a maximum flow of water is introduced to fill a selected washing compartment, thereby allowing the start of a desired washing operation to occur in a short time period. Once the water intake procedure 100 is finished, the washing operation can begin and, another washing compartment may start its water intake procedure 100.
According to one embodiment of the invention, a "first come, first served" concept is used. This means that the control unit 30 is arranged to control the water inlets 11, 21 such that the first water inlet 11 is allowed to open its inlet valve 11b and start letting water into the first washing compartment 10, only if the inlet valve 21 b of the second water inlet 21 is closed and water is currently not let into the second washing compartment 20. If the inlet valve 21b of the second water inlet 21 is open, the first water inlet 11 has to wait for that inlet valve 21 b to close, before opening its inlet valve11b, and start letting water into the first washing compartment 10. If, on the other hand, the inlet valve 11b of the first water inlet 11 is open when the second water inlet 21 wants to start letting water into the second washing compartment 20, the second water inlet 21 has to wait for the inlet valve 11b of the first water inlet 11 to close.
According to another embodiment of the invention, the different washing compartments 10, 20 are organized in a hierarchical manner, with different priorities. If, for example, the first washing compartment 10 is given the highest priority, it will always be allowed to start letting water into its washing tub 13, and may interrupt an ongoing water intake procedure in the second washing compartment 20 which consequently has a lower priority. This means that the first water inlet 12 takes precedence over the second water inlet 22. A water intake procedure that is interrupted will continue when the inlet valve of the interrupting washing compartment 10 is closed.
A water intake procedure 100 in a multi-compartment dishwasher 1 according to one embodiment of the invention has one or several time intervals for which the inlet valve is open. The length of these time intervals is predetermined and controlled by the control unit 30. This means that the water intake procedure 100 is at least partially time-controlled.
During the washing procedure of a washing operation, a certain amount of water is needed for securing that the dishes get clean enough, and for ensuring that the circulation pump 16, 26 functions as expected. As long as the water pressure is substantially constant, the amount of water can be regulated by controlling the length of the time intervals for which the inlet valve 11b, 21b is open.
Nevertheless, it occurs that the water pressure in the water inlet 11, 21 varies, e.g. because of a very low water pressure in the water supply system 2. In order to avoid problems concerning varying or low water pressure, the time-controlled water intake procedure can be made more safe by an arrangement according to an embodiment of the invention.
According to that embodiment, the water intake procedure 100 includes a step for securing that enough water is admitted into the washing compartment 10, 20 during the water intake procedure 100. For enabling this security check, the dishwasher 1 has an arrangement 19, 29 for detecting an amount of water in the washing compartment 10, 20.
According to an embodiment of the invention, the arrangement 19, 29 for detecting the water level in the washing compartment 10, 20 is arranged as a sensor device 19a, 29a that detects an air pressure in a blind pipe 19b, 29b, which is fluid in communication with the circulation pump 16, 26. The blind pipe 19b, 29b is directed upwards from the circulation pump and is closed in an end distal to the circulation pump 16, 26, such that when water enters the circulation pump 16, 26 and the open end of the pipe 19b, 29b, the air stuck in the pipe 19b, 29b is compressed. The detected air pressure is then a measure of the amount of water in the washing compartment 10, 20.
When the circulation pump is working, a considerably higher air pressure is generated in the blind pipe, than what is the case if the circulation pump is not working. This higher pressure level makes it easier to detect variations in the air pressure, caused by a varying amount of water in the washing compartment 10, 20.
According to an embodiment of the invention, the sensor device 19a, 29b is a high pressure cut-out, i.e. an electrical control switch which automatically opens or closes an electrical circuit if the pressure reaches a predetermined value.
A water intake procedure 100 including a step for securing that enough water is admitted into the washing tub 13, 23 may for example comprise the steps of:

opening 101 the inlet valve 11b, 21b;
letting 102 water into the washing compartment 10, 20 for a predetermined time interval;
closing 103 the inlet valve 11b, 21b; and
detecting 105 the amount of water in the washing compartment 10, 20 by means of the arrangement 19, 29 for detecting the amount of water in the washing compartment 10, 20.

For making it easier to detect the amount of water in the washing compartment using a pressure detecting device, the water intake procedure may preferably comprise a step of starting 104 the circulation pump 16, 26 such that it begins to suck water from the sump 13c, 23c, between the step of closing the inlet valve and the step of detecting the amount of water in the washing compartment.
When the detection step is performed, the next step to perform depends on the status of the arrangement 19, 29 for detecting the amount of water in the washing compartment 10, 20. If the amount of water in the washing compartment 10, 20 is satisfactory, the water intake procedure is considered to be successfully completed, and another procedure in the washing operation can start. If there is too little water in the washing compartment 10, 20, the circulation pump 16, 26 can be stopped, whereupon the steps described above can be repeated, and a new security check is performed. Another alternative is to let the circulation pump 16, 26 work and leave the inlet valve 11b, 21b open until the amount of water in the washing compartment 10, 20 is satisfactory.
Preferably, there is a time-limit for restricting the number of attempts that are allowed, or the total time allowed for performing a water intake procedure 100. If the amount of water in the washing compartment 10, 20 is still not satisfactory when the time-limit has passed, the water intake procedure 100 is considered to be unsuccessful and is terminated. When a water intake procedure is terminated because the time-limit is passed, a signal can be generated in order to tell a user of the washing machine that an error has occurred.
In the drawings and specification, there have been disclosed preferred embodiments and examples of the invention and, although specific terms are employed, they are used in a generic and descriptive detect only and not for the purpose of limitation, the scope of the invention being set forth in the following claims.

Claims

A multi-compartment dishwasher (1) comprising:
a first washing compartment (10), having a first washing tub (13) for receiving objects that are to be washed, and a first water inlet (11), for leading water into the first washing compartment (10) from a water supply system (2);

a second washing compartment (20), having a second washing tub (23) for receiving objects that are to be washed, and a second water inlet (21) for leading water into the second washing compartment (20) from the water supply system (2);

a control unit (30), operatively associated with the first and second washing compartments (10, 20), characterized in that the control unit (30) is arranged for controlling the first and second water inlets (11, 21), such that at any given instant, at the most one water inlet (11,21) lets water into its corresponding washing compartment (10, 20).
The dishwasher as claimed in claim 1, wherein the control unit (30) is arranged to control at least one of the first and second water inlets (11, 21) to let water into its corresponding washing compartment (10, 20) for a predetermined time interval.
The dishwasher as claimed in claim 1 or 2, wherein the control unit (30) comprises a first sub control unit (31) for controlling the first water inlet (11), a second sub control unit (32) for controlling the second water inlet (21), and a communication link (33) between the two sub control units (31, 32) for enabling communication between the sub control units (31, 32).
The dishwasher as claimed in claim 1-3, wherein each washing compartment (10, 20) further has a water circulation unit (12, 22) for propelling water into and out of the washing tub (13, 23) of the washing compartment (10, 20), the water circulation unit (12, 22) comprising
a circulation pump (16, 26), arranged to suck water from the washing tub (13c, 23c) and propel it into a conduit (17, 27) leading into the washing tub (13, 23), and

an arrangement (19, 29) for detecting an amount of water in the washing compartment (10, 20).
The dishwasher as claimed in claim 4, wherein the arrangement (19) for detecting an amount of water in the washing compartment (10, 20) comprises
a blind pipe (19b, 29b) arranged in communication with the circulation pump (16, 26), and

a pressure detecting device (19a, 29a), arranged for detecting an air pressure in the blind pipe (19b, 29b).
The dishwasher as claimed in claim 5, wherein the pressure detecting device (19a, 29a) is a high pressure cut out.
The dishwasher according to any of claims 1 to 6, wherein the control unit (30) is arranged to control the water inlets (11, 21) such that the first water inlet (11) takes precedence over the second water inlet (21).
The dishwasher according to any of claims 1 to 6, wherein the control unit (30) is arranged to control the water inlets (11, 21) such that the first water inlet (11) is allowed to start leading water into its corresponding washing compartment (10) only if the second water inlet (21) is not leading water into its corresponding washing compartment (20).
Method for letting water into a multi-compartment dishwasher, which dishwasher has:
a first washing compartment (10), having a first washing tub (13) for receiving objects that are to be washed, and a first water inlet (11) for leading water into the first washing compartment (10) from a water supply system (2);

a second washing compartment (20), having a second washing tub (23) for receiving objects that are to be washed, and a second water inlet (21) for leading water into the second washing compartment (20) from the water supply system (2);

a control unit (30), operatively associated with the first and second washing compartments (10, 20), the control unit (30) being arranged for controlling the first and second water inlets (11, 21),

the method comprising:
controlling the first and second water inlets (11, 21), such that at any given instant, at the most one water inlet (11,21) lets water into its corresponding washing compartment (10, 20).
The method as claimed in claim 9, wherein the step of controlling the first and second water inlets (11, 21) comprises controlling each inlet (11, 21) to let water into its corresponding washing compartment (10, 20) for a predetermined time interval.
The method as claimed in claim 9 or 10, wherein each washing compartment (10, 20) further has a water circulation unit (12, 22) with a circulation pump (16, 26) for propelling water into and out of the washing tub (13, 23) of the washing compartment (10, 20), and wherein each water inlet (11, 21) has an inlet valve (11 b, 21 b) which can be opened and closed,
the method comprising:
controlling a water intake procedure (100) of the first washing compartment (10);

controlling a water intake procedure (100) of the second washing compartment (20);
wherein at least one of the water intake procedures (100) comprises the steps of:
opening (101) the inlet valve (11 b, 21 b);

letting (102) water into the washing compartment (10, 20) for a predetermined time interval;

closing (103) the inlet valve (11 b, 21 b);

detecting (105) an amount of water in the washing compartment (10, 20).
The method as claimed in claim 11, wherein the water intake procedure (100) further comprises, after the step of closing (103) the inlet valve (11 b, 21 b), and before the step of detecting (105) an amount of water in the washing compartment (10, 20), a step of;
starting (104) the circulation pump (16, 26);
The method as claimed in claim 11-12, wherein the water intake procedure (100) further comprises, if the detected amount of water in the washing compartment (10, 20) is less than a predetermined amount:
restarting (106) the water intake procedure (100).
The method as claimed in claim 12 and 13, wherein the water intake procedure (100) further comprises the step of stopping (107) the circulation pump before restarting the water intake procedure.
The method as claimed in any of claims 11-14, wherein the method comprises the step of terminating an ongoing water intake procedure (100) when a predetermined time limit is passed.