PROPERTY IN A DISHWASHER

TECHNICAL FIELD

The invention relates to a dishwasher comprising at least one rotating spray arm arranged to spray process water onto goods to be cleaned in a compartment of the dishwasher.

BACKGROUND

In dishwashers, it is desirable to detect various operational states causing failures that can lead to dishwasher damage, or damage of any goods to be cleaned accommodated in the dishwasher. Further, it may be desirable to detect operational states of the dishwasher in order to take appropriate measures for controlling the operation of the dishwasher depending on the detected operational state.

As an example, WO 2015/036040 discloses a dishwasher being equipped with a sensor, such as an accelerometer, for detecting spray arm blockage in the dishwasher. The accelerometer is arranged in a chassis of the dishwasher and is configured to detected shocks from process water being splashed by one or more spray arms onto the chassis.

In case the accelerometer detects irregularly occurring splashes of process water, it may be an indication of spray arm blockage.

A problem in the art is that customized, complex special-purpose sensors are utilized for detecting operational states of a dishwasher.

SUMMARY

An object of the present invention is to solve, or at least mitigate this problem in the art, and to provide an improved dishwasher arranged with at least one sensor for detecting spray arm blockage in the dishwasher. This object is attained in a first aspect of the present invention by a dishwasher comprising at least one rotating spray arm arranged to spray process water onto goods to be cleaned in a compartment of the dishwasher. The dishwasher further comprises at least one sensor arranged in a sump of the dishwasher and configured to detect a property of the process water indicating periodic rotation of the spray arm from process water sprayed by the spray arm into the sump, and to communicate a signal in response thereto indicative of the detected property, and a controller configured to receive the signal and to determine that the detected property changes periodically.

Advantageously, by determining from process water sprayed by the spray arm into the sump whether the detected property - e.g. pressure, level or flow rate of the process water in the sump- changes periodically or not, spray arm blockage and even rotational speed may be determined.

Further advantageous is that a sensor already available in the dishwasher is used for detecting the periodic changes, such as a pressure sensor, a water level sensor or a flow rate sensor. Any additional, expensive sensors to be mounted in the dishwashers may thus advantageously be avoided.

In an embodiment, if the controller detects that the property does not change periodically, the controller is configured to conclude that the spray arm is at least partially blocked.

In another embodiment, the sensor is configured to detect at least a first value of the property at a first spray arm position and at least a second value of the property at a second spray arm positon, and to communicate the measured values to the controller. The controller is configured to measure the time elapsed between the at least two measurements and determine the rotational speed of the spray arm based on the time elapsed and a

circumferential distance between the first and the second position. In another embodiment, the controller is configured to estimate a position of the spray arm based on the determined rotational speed and one of the first and the second spray arm positions being associated with the first and the second values of the property.

In a further embodiment, the sensor comprises a pressure sensor and the detected property is pressure of the process water exerted onto the pressure sensor in the sump.

In yet a further embodiment, the sensor comprises a flow sensor and the detected property is flow rate of the process water flowing through the flow sensor in the sump.

In still a further embodiment, the sensor comprises a level sensor and the detected property is level of the process water measured by the level sensor in the sump.

In an embodiment, the sensor is arranged at an interior wall of the sump, and in a further embodiment at a section of the sump adjacent to a bottom of the compartment.

In still an embodiment, the controller is arranged to communicate a detected spray arm blockage to a user via a user interface.

In a further embodiment, the controller is arranged to interrupt a current washing program in response to the detected spray arm blockage.

It is noted that the invention relates to all possible combinations of features recited in the claims. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described in the following. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Figure l shows a dishwasher in which the present invention is implemented;

Figure 2 illustrates an embodiment where a pressure sensor is utilized to detected spray arm blockage in a dishwasher;

Figure 3 illustrates the embodiment of Figure 2 but where the spray arm is in a different position;

Figure 4 illustrates an embodiment where a flow sensor is utilized to detected spray arm blockage in a dishwasher;

Figure 5 illustrates the embodiment of Figure 4 but where the spray arm is in a different position;

Figure 6 illustrates an embodiment where a level sensor is utilized to detected spray arm blockage in a dishwasher;

Figure 7 illustrates the embodiment of Figure 6 but where the spray arm is in a different position; and

Figure 8 illustrates another embodiment where rotational speed of the spray arm is determined.

DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

By the expression“process water” as used herein, is meant a liquid containing mainly water that is used in and circulates in a dishwasher. The process water is water that may contain detergent and/or rinse aid in a varying amount.

The process water may also contain soil, such as food debris or other types of solid particles, as well as dissolved liquids or compounds. Process water used in a main wash cycle is sometimes referred to as the wash liquid. Process water used in a rinse cycle is sometimes referred to as cold rinse or hot rinse depending on the temperature in the rinse cycle.

Figure l shows a dishwasher 10 in which the present invention is

implemented. It should be noted that dishwashers can take on many forms and include many different functionalities. The dishwasher 10 illustrated in Figure t is thus used to explain different embodiments of the present invention and should only be seen as an example of a dishwasher in which the present application can be applied. The dishwasher to comprises a washing compartment or tub n housing an upper basket 12, a middle basket 13 and a lower basket 14 for accommodating goods to be washed. Typically, cutlery is accommodated in the upper basket 12, while plates, drinking- glasses, trays, etc. are placed in the middle basket 13 and the lower basket 14.

Detergent in the form of liquid, powder or tablets is dosed in a detergent compartment located on the inside of a door (not shown) of the dishwasher 10 by a user, which detergent is controllably discharged into the washing compartment 11 in accordance with a selected washing programme. The operation of the dishwasher 10 is typically controlled by processing unit/controller 31 executing appropriate software.

Fresh water is supplied to the washing compartment 11 via water inlet 15 and water supply valve 16. This fresh water is eventually collected in a so called sump 17 arranged under the compartment 11, where the fresh water mixed with the discharged detergent - resulting in process water 18 - is transported. At the bottom of the washing compartment is a filter 19 for filtering soil from the process water 18 before the process water leaves the compartment 11 via the sump 17 for subsequent re-entry into the washing compartment 11 through circulation pump 21. Thus, the process water 18 passes the filter 19 and is pumped through the circulation pump 21, which typically is driven by a brushless direct current (BLDC) motor 22, via a conduit 23 and respective process water valves 24, 25 and sprayed into the washing compartment 11 via nozzles (not shown) of a respective spray arm 26, 27, 28 associated with each basket 12, 13, 14. Thus, the process water 18 exits the washing compartment 11 via the filter 19 and is recirculated via the circulation pump 21 and sprayed onto the goods to be washed accommodated in the respective basket via nozzles of an upper spray arm 26, middle spray arm 27 and lower spray arm 28. A pressure sensor 20 is arranged in the sump 17 for measuring process water pressure to determine whether there is enough water in the

compartment 11. Alternatively, instead of using a pressure sensor, a so called floater may be used for measuring a water level, or an impeller for measuring water flow.

The washing compartment 11 of the dishwasher 10 is drained on process water 18 with a drain pump 29 driven by a BLDC motor 30. It should be noted that it can be envisaged that the drain pump 29 and the circulation pump 21 may be driven by one and the same motor.

Figure 2 illustrates an embodiment using the pressure sensor 20 being communicatively connected to the controller 31 for detecting a property of the process water indicating periodic rotation of the spray arm in order to detect spray arm blockage, in this case the property being pressure. Figure 2 shows nozzles 33, 34, 35 of the lower spray arm 28 releasing splashes of process water into the compartment 11. After having splashed over the goods to be cleaned, the process water sprayed by the spray arm 28 will reach the bottom of the compartment 11, pass through the filter 19 and enter the sump 17, where it will be either re-circulated in the compartment 11 via the spray arms or drained from the dishwasher.

In an embodiment, the sensor 20 is arranged at an interior wall of the sump 17 and in a section of the sump 17 located adjacent to a bottom of the compartment 11, just under the filter 19.

As illustrated in Figure 2, assuming that the spray arm 28 is in a position where the nozzles 33, 34, 35 are located to the left, the level of the process water 18 in the sump 17 will be slightly higher at the left-hand side.

In contrast, with reference to Figure 3, upon the spray arm 28 rotating 180° thereby positon the nozzles 33, 34, 35 at the right-hand side of the figure, the level of the process water 18 in the sump 17 will be slightly higher at the right- hand side.

As is understood, in practice the changes in process water level are typically smaller than that illustrated with reference to Figures 2 and 3; nevertheless, the changes may indeed be detected by the sensor 20. Further, a spray arm of a dishwasher is typically arranged with nozzles for spraying process water at a number of different positions distributed over the length of the arm, and may further have different spray directions, both in an upward and

downward direction.

Hence, in Figure 2, the pressure sensor 20 will detect a first pressure Pi caused by the process water column exerting pressure onto the sensor 20, whereas in Figure 3 the pressure sensor 20 will detect a second pressure P2 caused by a higher process water column exerting pressure on the sensor 20, whereby P2 will be greater than Pi.

When the spray arm 28 rotates another 180° to the position of Figure 2, the first pressure Pi will again be measured, and so on. As a result, the pressure sensor 20 will measure the pressure exerted by the process water 18 onto the sensor 20 and communicate the measured pressure accordingly to the controller 31.

It is noted that there typically will be a slight delay from the moment where the spray arm 28 sprays process water 18 at a particular position, to the moment where the sensor 20 actually detects the pressure associate with the particular spraying position of the arm 28, since the process water 18 being sprayed travels some distance before reaching the sump 17.

The controller 31 will be configured to detect the periodical changes in measured pressure, for instance as indicated by the measured first and second pressures Pi and P2, and conclude that as longs as the measured values changes periodically, the spray arm 28 is rotating as intended. In a very simple example, assuming that the measure pressure changes from the first pressure Pi to the second pressure P2, and so on, the controller 31 will conclude that the spray arm 28 rotates adequately.

To the contrary, should the measured pressure values no longer change periodically, but for instance change in an irregular manner, the controller 31 concludes that the spray arm 28 is partially of completely blocked, and may alert a user of the dishwasher accordingly via the user interface 32 shown in Figure 1.

It is understood that a spray arm typically comprises more nozzles for releasing process water 18 in the dishwasher 1, and these may be

symmetrically or asymmetrically arranged along the spray arm.

Further, in practice, the spray arm 28 may need to rotate at least two full revolutions in order for the controller 31 to be capable of establishing periodicity in the measured property.

With reference to Figures 4 and 5, in an alternative embodiment, an impeller 40 or some other appropriate flow sensor is used as the sensor for detecting a property of the process water 18 indicating periodic rotation of the spray arm 28.

As illustrated in Figure 4, assuming that the spray arm 28 is in the position where the nozzles 33, 34, 35 are located to the left, the flow rate of the process water 18 into the sump 17 will be higher at the left-hand side.

In contrast, with reference to Figure 5, upon the spray arm 28 rotating 180° thereby positon the nozzles 33, 34, 35 at the right-hand side of the figure, the flow rate of the process water 18 in the sump 17 will be higher at the right- hand side. Hence, in Figure 4, the impeller 40 will detect a first process water flow Qi, whereas in Figure 5 the impeller 40 will detect a second process water flow Q2 being greater than Qi due to the greater volume of water flowing through the impeller 20 when the nozzles 33, 34, 35 are located at the right-hand side.

When the spray arm 28 rotates another 180° to the position of Figure 2, the first flow Qi will again be measured, and so on.

As a result, the impeller 40 will measure the flow of process water 18 and communicate the measured flow rate accordingly to the controller 31.

The controller 31 will be configured to detect the periodical changes in measured flow rate, for instance as indicated by the measured first and second flow rates Qi and Q2, and conclude that as longs as the measured flow values change periodically, the spray arm 28 is rotating as intended.

To the contrary, should the measured process water flow values no longer change periodically, but for instance change in an irregular manner, the controller 31 concludes that the spray arm 28 is partially of completely blocked, and may alert a user of the dishwasher accordingly via the user interface 32 shown in Figure 1. With reference to Figures 6 and 7, in yet an alternative embodiment, a floater 50 or some other appropriate water level sensor is used as the sensor for detecting a property of the process water 18 indicating periodic rotation of the spray arm 28.

As illustrated in Figure 6, assuming that the spray arm 28 is in the position where the nozzles 33, 34, 35 are located to the left, the level of the process water 18 in the sump 17 will be slightly higher at the left-hand side.

In contrast, with reference to Figure 7, upon the spray arm 28 rotating 180° thereby positioning the nozzles 33, 34, 35 at the right-hand side of the figure, the level of the process water 18 in the sump 17 will be slightly higher at the right-hand side.

Hence, in Figure 6, the floater 50 will detect a first process water level Li, whereas in Figure 7, the floater 50 will detect a second process water level L2 being greater than Li due to the greater volume of water into the sump 17 at the right hand-side where the floater 50 is located when the nozzles 33, 34, 35 are located at the right-hand side.

When the spray arm 28 rotates another 180° to the position of Figure 6, the first level Li will again be measured, and so on.

As a result, the floater 50 will measure the level of process water 18 and communicate the measured level accordingly to the controller 31.

The controller 31 will be configured to detect the periodical changes in measured process water level, for instance as indicated by the measured first and second levels Li and L2, and conclude that as longs as the measured level values change periodically, the spray arm 28 is rotating as intended.

To the contrary, should the measured process water level values no longer change periodically, but for instance change in an irregular manner, the controller 31 concludes that the spray arm 28 is partially of completely blocked, and may alert a user of the dishwasher accordingly via the user interface 32 shown in Figure 1.

In a further embodiment, the controller 31 is advantageously arranged to communicate the detected spray arm blockage of the dishwasher 10 to a user via a user interface 32, such that the user can take further action. This can be performed visually and/or audibly via the user interface 32. In still a further embodiment of the present invention, the controller 31 is advantageously arranged to interrupt a current washing program in response to the detected spray arm blockage, in case the blockage is serious and may cause further damage to the dishwasher 10, or the goods accommodate therein. The interruption may be communicated via the user interface 36.

Advantageously, the embodiments described hereinabove provide for straightforward detection of spray arm blockage, which is an undesired state in a dishwasher. Further, the detected spray arm blockage can be

communicated to a user via the user interface 32, or the controller 31 may even interrupt the current a washing program if there is a risk for dishwasher damage (or damage of goods).

Further advantageous is that a sensor already available in the dishwasher 1 is used for detecting the blockage, such as a sensor 50 configured to measure process water level in the sump 17. Any additional, expensive sensors to be mounted in the dishwashers may thus advantageously be avoided.

Figure 8 illustrates a further embodiment of the invention showing the spray arm 28 with the nozzles 33, 34, 35 in a top view, with the sump 17 and the sensor 20 arranged below the spray arm 28.

As was discussed with reference to Figure 2, when the spray arm 28 is in position Post, the level of the process water 18 in the sump 17 will be slightly higher at the side of the sump 17 being opposite to where the pressure sensor 20 is arranged, and the pressure sensor 20 will detect a first pressure Pi caused by the process water column exerting pressure onto the sensor 20. In contrast, with reference to Figures 3 and 8, upon the spray arm 28 rotating 180°, thereby positioning the nozzles 33, 34, 35 in position Pos2, the level of the process water 18 in the sump 17 will be slightly higher at the side of the sump 17 where the pressure sensor 20 is arranged, and the pressure sensor 20 will detect a second pressure P2 caused by a higher process water column exerting pressure on the sensor 20, whereby P2 will be greater than Pi.

When the spray arm 28 rotates another 180° to the position of Figure 2, the first pressure Pi will again be measured, and so on.

Now, by using these pressure measurements performed the sensor 20, the controller 31 can determine the rotational speed of the spray arm 28.

In this example, the controller 31 concludes that when having read the first pressure Pi at a first time Ti and the second pressure P2 at a second time T2, the spray arm 28 has rotated 180°.

Assuming for instance that the difference in time between the first time Ti and the second time T2, DT = T2-T1 = 0.5 s, the controller 31 computes the rotational speed of the spray arm 28 to be o.5/0.5 = 1 revolution/s = 60 rpm.

Hence, the controller 31 may advantageously compute the rotational speed of the spray arm 28.

By computing the rotational speed from the measurements performed at Posi and Pos2, the controller 31 may further estimate the position of the spray arm 28 for any pressure reading (or flow/level reading).

Further, if the controller 31 determines that the rotational speed is o, for instance by detecting that the pressure measured by the sensor does not change, the controller 31 will conclude that the spray arm 28 is blocked, and may alert a user accordingly.

In a further embodiment, given the periodical changes in the measured property, the position of the spray arm 28 may be determined from any measured property value. As an example, assuming that the first pressure Pi is measured at the first position Posi by the pressure sensor 20; the controller will then be able to interpolate a position POSN of the spray arm 28 for any other measured pressure value PN. The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.