EP2160970B1

EP2160970B1 - Weight sensing method for dishwashers

Info

Publication number: EP2160970B1
Application number: EP09167676A
Authority: EP
Inventors: Evren Bal; Mehmet Eldem
Original assignee: Vestel Beyaz Esya Sanayi ve Ticaret AS
Current assignee: Vestel Beyaz Esya Sanayi ve Ticaret AS
Priority date: 2008-09-05
Filing date: 2009-08-12
Publication date: 2012-03-21
Anticipated expiration: 2029-08-12
Also published as: ATE549963T1; EP2160970A2; EP2160970A3; EP2160970A8; TR200806744A2

Abstract

In a method for sensing the dish load in dishwashers, the water level in the machine pool (7) is measured at first step by means of a water-level measuring unit and this is reported to the machine's control unit; the upper nozzles (5) or lower nozzles (4) are rotated to some extent at second step, by operating the machine's washing pump (1); said pump (1) is stopped at third step, and some time is allowed for the water present on the upper rack (21) or lower rack (22) to drain away; the water level in the pool (7) is measured once more at forth step; and the load amounts at each rack is determined by means of the control unit at fifth step, based on the difference between the water levels measured at the first and forth steps; all these steps being conducted separately both for the upper rack (21) and the lower rack (22).

Description

Technical Field

The present invention relates to dishwashers that sense the dish load on upper and lower racks individually.

Prior Art

During a normal wash in dishwashers, this operation is conducted by the circulation of the water transferred by means of a pump through the washing nozzles, and recirculation of the water, which accumulates in a pool, back to the nozzles by means of the pump. In these machines, the use of different washing programs according to the amount of dishes to be cleaned becomes significant with respect to the consumption of water, cleaning agent, and energy.
The load sensing systems in dishwashers according to the prior art are realized by means of sensors disposed in the machine. These systems can be exemplified with the published patent applications DE10253017 and EP1252857 , in which the measurement is made according to the dirtiness of water that is used.
Another published patent document No DE10246016 A1 discloses a method of detecting dishwasher load based on measuring the quantity of washing fluid draining from dishes during washing. In said document, the dishwasher has an optical sensor to determine the level of washing fluid in the sump and an ultrasonic sensor to monitor the instantaneous fluid level. During washing, said sensors enable to determine the change in the quantity of fluid in the sump as fluid is circulated. Then, the determined level is used to estimate the ware load in the dishwasher so as to select the washing cycle by the programmer.

Brief Description of Invention

In the dishwasher equipped with the load sensing feature according to the present invention, load sensing is conducted by instantaneously monitoring the water level in the machine. This sensing is made separately for each rack.
In order to determine the water level in the machine, water-level measuring units are employed on the washing system of the machine. As an alternative embodiment for this purpose, there is provided a tube of a length that corresponds to the distance between the lower starting point and the top ending level of the pool water level and a floating element, which comprise a magnetic core or whose material has magnetic features, is provided in said tube. Water in the tube moves the floating element according to the water's buoyancy force principle. The movement of the floating part in the tube (the level of water) is sensed by a coil system with a magnetic reader, coiled around the tube. Or alternatively, the water level is read with the aid of a presostate, which is placed at the tip of a tube that is in connection with the pool. When the water starts raising or lowering, the presostate transmits signals of different frequencies, so that the water level can be determined.
The control unit of the dishwasher according to the present invention conducts the entire control of the machine, such as operating the valves, pumps, and heaters, and managing the program steps, etc., and additionally, it determines the dish load with the aid of water level measuring units and the washing system.
According to the present invention, the water level in the pool of the machine is measured instantaneously, such measured instant values are reported to the control unit, so that the machine, by itself, measures instant water losses and accordingly determines the load rate, automatically senses the distribution of this load to the lower and upper racks, and carries out the washing steps by means of a predefined algorithm according to this load.
According to the present invention, the load density of dishes placed in the machine's lower and upper racks can be calculated. Thus, according to which rack contains a more dense load, the washing intensity at that part is increased, such that a more efficient washing is ensured and the washing performance is developed. According to the present invention, the machine is enabled to make the program selection automatically, so that once the washing step is determined, the determination of the load levels of dishes placed into the machine is taken over from the user's initiative.
Additionally, since the amount of water in the machine is measured instantaneously according to the method of the present invention, any abnormal water level alterations, e.g. any uncontrolled intake of water into the machine, or the case in which pans or similar utensils in the machine are turned upside down so that their interior is filled with water, are sensed automatically. Thus, when the water level drops below a predetermined minimum level or exceeds a predetermined maximum level, the machine does not proceed with the normal washing step, but generates an error signal to the user.
Additionally, in cases of extreme foaming or occlusion of the filter during a normal wash or following the completion of a wash, the dishwasher may face difficulties in draining out the water. According to the present invention, however, the water level is measured during the draining-out period as well, and when the drained-out amount of water is not in compliance with what has been determined by this period, this case is interpreted as a potential filter occlusion or extreme foam formation, so that the machine is stopped and an error signal is generated for the user.

Aim of the Invention

An aim of this invention is to ensure the calculation of the dish load by instantaneously measuring the water level in the dishwasher.
Another aim of this invention is to ensure the determination of the load density of dishes placed in the dishwasher for the upper rack and for the lower rack separately.
A further aim of the invention is to enable the dishwasher to determine the dishwasher load by itself.
Yet another aim of the present invention is to enable the dishwasher to automatically determine the washing steps according to the load density present at the lower and upper racks and to conduct washes at differing intensities at the lower and upper racks.
Yet another aim of the present invention is to make it possible to easily adapt the water-level measuring units to currently-used dishwashers.
Still another aim of the present invention is to provide a load sensing system for currently-used dishwashers, by making use of the current components of such currently-used dishwashers and of inexpensive and reliable water-level measuring units.

Description of Figures

An exemplary dishwasher washing system and exemplary water-level measuring units according to the present invention are illustrated in the annexed figures, wherein:

Figure 1 is a general perspective illustration of the washing unit of a dishwasher.
Figure 2 is a schematic illustration of water levels of a dishwasher.
Figure 3 is an illustration of a water-level measuring unit for a dishwasher.
Figure 4 is an illustration of another water-level measuring unit for a dishwasher.

The parts in the figures are numbered one by one and the corresponding terms of these numbers are given below.

Pump (1)
Interconnection tube (2)
Heater (3)
Lower nozzles (4)
Upper nozzles (5)
Filter system (6)
Pool (7)
Nozzle tubes (8)
Upper rack (21)
Lower rack (22)
Tube (23)
Coil (31)
Floating element (32)
Presostate (41)

Disclosure of Invention

The operation of the washing system of a standard dishwasher, as illustrated in Figure 1, is as follows. Before washing is started, the water taken into the machine from the mains via the valves is filled into a pool (7), including the machine's filter system (6) as well. After a certain volume of water is taken in, the mains supply is cut off, then the water in the pool (7) is sucked by means of a pump (1) and passed through a heater (3) by means of an interconnection tube (2). Heated water is directed to the nozzle tubes (8) in connection with the upper nozzles (5) and lower nozzles (4) over the pool. The washing operation is carried out by delivering the water, which is pressurized by means of the washing pump (1), to the dishes from the lower nozzles (4) and upper nozzles (5). (Water output from the pump (1) can be separately guided to the lower and upper nozzles (4, 5). This operation can be made by means of a part, i.e. a divisor.)
According to the present invention, the water level present in the machine pool (7) can be read by two alternative applications. In the water-level measuring unit of the first alternative, illustrated in Figure 3, a tube (23) is disposed, which is in connection with the pool (7), and has a length that corresponds to the distance from the lowest starting point to the top ending level of the machine's water level. In the tube (23) is provided a floating element (32), which comprise a magnetic core or whose material has magnetic features. Water in the tube (23) moves the floating element (32) according to the water's buoyancy force principle. Here is provided also a coil (31) coiled around the tube (23), thus, the movement of the magnetic featured floating element (32) in the tube (23) is sensed from the changes that occur on the coil's (31) impedance value. Thus the water level in the tube (23) is measured. The water level in the tube (23) is the same with the water level in the machine.
In the water-level measuring unit of the second alternative as illustrated in Figure 4, the water level in the machine is read by means of a presostate (41) disposed at the tip of the tube (23) (by referring to water pressure). The water level data read by means of the coil (31) or the presostate (41) is instantly reported to the machine's control panel. Thus, it becomes possible both to determine, if water in the machine is drained out, and if water in the machine reached the overflow level, as well as to sense the dish load in the dishwasher in an automatic manner. For this purpose, the steps of the following method are followed.
In the method for sensing the dish load in dishwashers, the following steps are followed separately both for the upper rack (21) and the lower rack (22),

the first step of measuring the water level in the machine by means of a water-level measuring unit and of reporting this data to the control unit of said machine;
the second step of operating the machine's washing pump (1) and thereby rotating the upper nozzles (5) or lower nozzles (4) to some extent;
the third step of stopping said pump (1) and waiting some time so that the water on the upper rack (21) or lower rack (22) can drain away;
the forth step of measuring again the water level in the machine by means of said measuring unit;
the fifth step of determining the load amounts at each rack by means of the control unit, based on the difference between the water levels measured at the first and forth steps.

Thereafter each of the upper and lower nozzles (5, 4) is operated at an intensity that is proportional to the load amounts determined for each individual rack (21, 22).
The control unit of the dishwasher according to the present invention conducts the entire control of the machine, such as operating the valves, pumps, and heaters, and managing the program steps, etc., and additionally, it determines the dish load with the aid of said water-level measuring units and the washing system.
In order to determine the dish load, after water is taken in to the machine, first the water level in the machine is measured by any of the foregoing water level measurement approaches (presostate (41) or coil (31)), and this measurement result is reported to the machine's control unit. For instance, the initial water level is the level (a) illustrated in Figure 2.
Then, with the machine's washing pump (1) being operated, only the upper nozzles (5) are rotated several times, then the pump (1) is stopped, and waited for a certain period of time so that the water present at the upper rack (21) drains away, and then the water level is measured once more. This measured value is the level (b) illustrated in Figure 2. Since the dishes present at the machine's upper rack (21) shall retain some amount of water, the second measured value (level b) is lower than the first measured value (value a). The dish load present at the upper rack (21) is determined by the control unit according to the difference between these two values. The load density at the machine's upper rack (21) is revealed according to the extent of water loss.
Then, with the machine's washing pump (1) being operated again, now only the lower nozzles (4) are rotated several times, then the pump (1) is stopped, a certain time is allowed for the water present at the lower rack (22) to drain away, and then the water level is measured once more. This measured value is the level (c) illustrated in Figure 2. Since the dishes present at the machine's lower rack (22) shall likewise retain some amount of water, the third measured value (level c) will be lower than the second measured value (value b). The dish load present at the lower rack (22) is determined by the control unit according to the difference between these two values. The load density at the machine's lower rack (22) is similarly revealed according to the extent of water loss.
Thus the machine's control unit can automatically change the wash algorithm according to the load density. The wash to be conducted at the upper rack (21) may have a differing intensity from that to be conducted at the lower rack (22).
Maximum water loss and minimum water loss data are loaded in advance onto the control unit as reference values for determining the load density. The machine decides on the extent of density of the load, according to the extent of water loss as measured by referring to these values. So the present invention enables the dishwasher to conduct each operation by itself for measuring the load and takes over the determination of the load density from the user's initiative.
Besides the two alternatives given above for measuring the water level, other measuring devices, which measures the water level in the machine and reports this to the control unit can also be used. Carrying out the load measurement by means of already-present components of a dishwasher, besides the water-level measuring units, is one of the advantages of the present invention. In other words, it is sufficient to load the algorithm of the load sensing method to the control unit with the steps disclosed above, and to use a water-level detection unit communicating with the control unit.
Additionally, since the amount of water in the machine is measured instantaneously according to the method of the present invention, any abnormal water level alterations, e.g. any uncontrolled intake of water into the machine, or the case in which pans or similar utensils in the machine are turned upside down so that their interior is filled with water, are sensed automatically. Thus, when the water level drops below a predetermined minimum level or exceeds a predetermined maximum level, the machine does not proceed with the normal washing step, but generates an error signal for the user.
Additionally, in cases of extreme foaming or occlusion of the filter during a normal wash or following the completion of a wash, the dishwasher may face difficulties in draining out the water. According to the present invention, however, the water level is measured during the draining-out period as well, and when the amount of water drained-out does not correspond to what has been determined by this period, this case is interpreted as a potential filter occlusion or extreme foam formation, so that the machine is stopped and an error signal is generated for the user.

Claims

A method of operation of a dishwasher comprising a method for sensing the dish load in dishwashers which comprises the following steps to be conducted separately both for the upper rack (21) and the lower rack (22),
• a first step of measuring the water level in the machine by means of a water-level measuring unit and of reporting this data to the control unit of said machine;

• a second step of operating the machine's washing pump (1) and thereby rotating the upper nozzles (5) or lower nozzles (4) to some extent
characterized in that the method for sensing the dish load in dishwashers further comprises the steps to be conducted separately both for the upper rack (21) and the lower rack (22),
• a third step of stopping said pump (1) and waiting some time so that the water on the upper rack (21) or lower rack(22) can drain away;

• a forth step of measuring again the water level in the machine by means of said measuring unit;

• a fifth step of determining the load amounts at each rack by means of the control unit, based on the difference between the water levels measured at the first and forth steps.
A method according to Claim 1, characterized in that each of the upper and lower nozzles (5, 4) is operated at an intensity that is proportional to the load amounts determined for each individual rack (21, 22).
A method according to Claim 1, characterized in that the water-level measuring unit comprises a tube (23) in connection with a pool (7); a coil (31) coiled around this tube (23), and a floating element (32) with magnetic feature provided in this tube (23).
A method according to Claim 3, characterized by instantaneously measuring the water level according to impedance changes the floating element (32) generates on the coil (31).
A method according to Claim 1, characterized in that said water-level measuring unit comprises a tube (23) in connection with a pool (7), and a presostate (41) provided at the tip of said tube (23).
A method according to Claim 5, characterized in that said presostate (41) measures the water level instantaneously by referring to the water pressure in the tube (23).
A method according to claim 4 or 6, characterized in that the machine operation is stopped, when the water level drops below a predetermined minimum level, or exceeds over a predetermined maximum level.
A method according to claim 4 or 6, characterized in that the machine operation is stopped, when the water level measured during the discharge period is not at rates, as determined with the amount of drained-out water.
A method according to claim 7 or 8, characterized in that when the machine is stopped, an error signal is generated for the user.
A dishwasher using the method according to any of the preceding claims.