EP1633231A2

EP1633231A2 - Improved wash method, and dishwashing machine implementing such a method

Info

Publication number: EP1633231A2
Application number: EP04730322A
Authority: EP
Inventors: Giuseppe Marchitto; Nicola Gaudiano
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2003-04-29
Filing date: 2004-04-29
Publication date: 2006-03-15
Also published as: WO2004096006A2; WO2004096006A3; ITTO20030324A1

Abstract

The present invention relates to a wash method in a dishwashing machine, of a type suitable for implementing at least one phase for checking the value of the pressure (12, 15, 17, 36) existing in one or more points of the hydraulic circuit of said dishwashing machine through sensor means in order to carry out subsequent actions (13, PF, 16, 18) of said method (1), which are commanded by a machine management and control system suitable for detecting and processing information. The peculiarity of the wash method consists in the fact that it comprises a special wash cycle (PF) which is capable of, when said sensor means in a pressure value check phase (12, 15, 17) provide values which are below a certain threshold suitable for ensuring a sufficient head to a wash pump of said hydraulic circuit in order to carry out an effective washing of the kitchenware, accomplishing hydraulic pressure conditions similar to those attainable in normal operating conditions, i.e. with filters (51, 52, 54) of the same hydraulic circuit free from residues or solid dirt.

Description

IMPROVED WASH METHOD, AND DISHWASHING MACHINE IMPLEMENTING SUCH A METHOD

DESCRIPTION

The present invention relates to an improved wash method and a dishwashing machine implementing such a method. More in detail, the invention concerns a method for the execution of a special wash cycle in a dishwashing machine, as well as the special wash cycle itself. As it is known, a dishwashing machine is made up of a plurality of components and circuits, such as a hydraulic circuit and a system for the management and control of the operation of said hydraulic circuit and of the whole machine. The management and control system permits to execute wash programs which the user can select among those stored in a control logic of the system itself and which can be implemented according to known procedures. Such a system uses one or more microcontrollers located inside the dishwashing machine and provided with suitable memories in order to implement and/or modify the wash methods available to the user.

The hydraulic circuit of a dishwashing machine, in particular one for domestic use, generally includes: - a tub supply duct for the water from the main, integrating safety and adjustment devices such as, for example, a flowmeter suitable for transferring data to the machine logic about the quantity of water introduced into the hydraulic circuit from the main;

- a softener device suitable for lowering the hardness of the water from the main, for a more effective chemical action of the detergents used in the wash cycle; - a wash tub where, in one or more dishwasher operation phases implementing the selected wash program, the wash water is sprayed onto the kitchenware;

- a pit, located under the wash tub, having the function of collecting and filtering the water coming from the supply duct and dripping into the tub after having been sprayed onto the kitchenware; - a wash pump which, when commanded, rotates to put the water in continuous circulation within the hydraulic circuit, and which is connected to the pit through an outlet generally located in the lower part of the pit itself;

- sprayer means which allow the water to be conveyed, with appropriate dynamic characteristics and possibly enriched with washing agents, onto the kitchenware to be washed in order to carry out an effective mechanical and chemical action on it; - means for warming up the water circulating in the tub to an appropriate temperature, in order to produce a further thermal effect on the kitchenware to be washed, thereby improving the washing result;

- a wash water drain circuit, wherein a drain pump, when activated, intakes the water from the pit and conveys it to a drain duct. The hydraulic circuit also comprises sensor means for pressure detection, and in particular to detect if the pressure of the circulating fluid drops below a certain predetermined design threshold. Such sensors, which are typically pressure switches, are electrically connected to the machine management and control system, which receives and processes such information. Nowadays it is common to use a pressure switch associated to the lower compartment of the pit of the dishwasher, which is suited to detect whether a given pressure caused by a predetermined water head is present or not in the pit, and to subsequently send such information to the logic of the management and control system. Some dishwashers are provided with further pressure sensor means suitable for transmitting the value of the dynamic pressure existing in a certain point of the hydraulic circuit to the management and control system. An example of such an application is illustrated in the Italian Patent Application No. TO2003A000256 in the name of the present Applicant. During each of the wash phases of the dishwashing machine, the management and control system takes into account, for determining the subsequent phases to be implemented, both the static pressure parameter read by the pressure switch in the pit and the dynamic pressure parameter detected by another sensor in the circuit, if any, also called "high pressure switch"; in the embodiment example referred to in the above- mentioned application, the high pressure switch is located at the outlet of the wash pump. With this procedure, the system can verify if there are any pressure losses in the hydraulic circuit, and in particular: - if the water head in the pit is sufficient to ensure the correct operation of the wash pump and consequently an effective washing of the kitchenware;

- if the dynamic pressure value in a certain point of the circuit is sufficient to ensure a really effective washing of the kitchenware. In practice it may happen, in fact, that the accumulated solid dirt of the kitchenware clogs the filters in the pit, resulting in a reduction of the mass of water being able to seep into the lower part of the pit and to circulate in the hydraulic circuit with respect to the design value, such reduction being sometimes substantial. To operate properly, the wash pump, driven by the electric motor and generally calibrated so as to ensure a fixed head at all times, needs the presence of a certain water head in the pit. If the water head is insufficient, the pump is going to intake air as well as water. Therefore the hydraulic pressure in the circuit will drop, sometimes even to values lower than half the design ones; the dishwasher will carry out an ineffective washing due to an insufficient pressure from the hydraulic circuit to the sprayers and the resulting poor mechanical action of the jets sprayed onto the kitchenware.

There are also other reasons for the poor washing result in such a situation, which will be analyzed in the following paragraphs.

The management and control system used in the known dishwashers uses the data of insufficient pressure or of pressure below a certain predetermined threshold received from one or more pressure switches in the circuit mainly to cut out the power supply of the electrical resistances used for warming up the circulating wash water. This method prevents such resistances from overheating in case the circulating water mass is substantially reduced, avoiding the risk of damage to the resistances, which may eventually even blow out, as well as the risk of damage to the plastic covers, if any, touching the resistances.

The logic of the management and control system of many dishwashers does not provide for the deactivation of the wash pump; the kitchenware is therefore washed with cold water and low water pressure to the sprayers in the tub, with unsatisfying washing results due to a reduced mechanical and thermal action performed by the water onto the kitchenware.

Other dishwashers are fitted with safety systems which in such a case stop the wash cycle completely, and in some instances warn the user of the problem occurred. In these dishwashers, filters clogging therefore causes a complete machine stop until the correct operating conditions are restored, generally through a manually user's or a technician's intervention. A further disadvantage of the known dishwashers is represented by the fact that the electric motor associated to the wash pump, when working with a lower head than expected from its designing, is subject to the risk of blowing out, in that it may reach rotational speeds much higher than the maximum ones foreseen by the motor design specifications. In the absence of the correct wash water or lye flow rate, the pump rotor shank may also reach an excessive temperature risking a seize itself, therefore requiring a subsequent replacement of the entire dishwasher motor pump assembly.

In conclusion, the known dishwashing machines are provided with machine management and control systems that include safety systems which are suitable for preventing the resistances used for warming up the wash water from overheating, but cannot avoid poor washing results due to an insufficient pressure in the hydraulic system or to the operation with cold water, and also cannot prevent the electrical motor associated to the wash pump from working incorrectly. Within such a frame, the present invention intends to solve the above-mentioned issues by realizing a method for performing a special wash cycle in a dishwashing machine as well as a special wash cycle and a dishwashing machine implementing such a method and/or special cycle, which is capable of carrying out a satisfactory washing of the kitchenware even with the filters in the wash tub clogged due to a large quantity of accumulated dirt or residues. It is an object of the method and special wash cycle of the dishwashing machine according to the invention to provide an effective washing of the kitchenware whatever the conditions of dirtiness in the wash tub. The dishwasher is therefore much more versatile than the known ones, in that it does not require immediate maintenance in case of the presence of a large quantity of dirt in the tub, at the same time always ensuring an effective washing.

It is a further object of the invention to avoid any damage to the components of the dishwashing machine in case of presence of dirt which clogs the filters in the tub, i.e. which prevents the water from flowing to the bottom of the pit, at the same time ensuring satisfactory washing results. In particular, the invention avoids the risk of damage to the wash motor pump assembly, e.g. due to blowing out of the electric motor driving the pump or the seizing of the rotor shank.

It is a further object of the invention to attain the above-mentioned objects and simultaneously to advise the user to remove the dirt from the tub, although this operation is not strictly necessary, in order to obtain subsequent high quality washings. It is a further object to accomplish the above-mentioned objects by means of an economical and reliable solution, which is easily applicable to the current dishwashing machines.

In order to attain said objects, the present invention comprises a method for the execution of a special wash cycle in a dishwashing machine as well as a special wash cycle and a dishwashing machine implementing such a method and/or special cycle, as featured by the characteristics of the attached claims, which are integral part of the present description.

Further objects, characteristics and advantages of the present invention will become apparent from the description of a detailed representation of the invention itself and from the annexed drawings, which are supplied by way of an explanatory and non- limiting example, wherein:

- Fig. 1 shows a block diagram related to the method for the execution of a special wash cycle in a dishwashing machine according to the present invention;

- Fig. 2 shows a schematic diagram of a special wash cycle according to the present invention; - Fig. 3 shows a schematic sectional view of a part of the undertub area of a dishwashing machine according to the invention;

- Fig. 4 shows the schematic sectional view of Fig. 3 in a particular operating condition of the dishwashing machine, i.e. with clogged filters in the pit;

- Fig. 5 shows a block diagram related to a particular phase of the special wash cycle shown in Fig. 2.

It must be stated beforehand that the method for the execution of the special wash cycle in a dishwashing machine, as well as the program implementing said special cycle according to the invention and described here in a non-limiting embodiment example, is implemented in a special control card located inside the dishwashing machine. Said control card is a part of the dishwashing machine management and control system; it is of a type known in the art and comprises a microcontroller having the necessary memory means where the wash and management programs of the machine are allocated. Being known, for simplicity's sake the components and the operation of the control card will not be described in detail herein. It must also be stated beforehand that the dishwashing machine taken into consideration in the example described herein, implementing the method which is the subject of the present invention, is of a type provided with a pressure switch associated to the lower compartment of the pit of the dishwasher and an additional pressure switch, i.e. the so- called "high pressure switch", associated to or in proximity of the outlet duct of the wash pump, e.g. as described in the above-mentioned Italian Application No. TO2003A000256. The hydraulic circuit and the management and control system of the machine also have the same characteristics already introduced and described. Fig. 1 shows a block diagram of a wash method in a dishwashing machine, globally indicated with 1, which includes a special wash cycle according to the invention, indicated with PF. Said special wash cycle has the characteristic of completing an entire wash cycle, as specified below, even if the filters are not effectively cleaned.

The method 1 starts when a user has selected a specific wash program to be carried out, e.g. by means of a knob of a selector mechanism or through suitable push-buttons located on a control shelf and connected to the control card of the dishwashing machine. The selection of the set program is read, interpreted and implemented by the dishwashing machine management and control system by the means of said control card.

The start of the wash method 10 is implemented by draining any liquids existing from a previous washing and by executing a first water supply 11, of a static type, i.e. takeing place without water circulation in the hydraulic circuit. It must be stated that, from this point onwards, the pressure sensors will be defined as being "full" when the detected pressure is equal to or higher than a predetermined threshold; on the contrary, they will be defined as being "empty" when said threshold is not reached.

The method 1 specifies the following additional steps:

12 a first pressure check carried out only by the pressure switch located in the pit, as for there is no dynamic water circulation in the hydraulic circuit of the dishwasher. If the pressure switch signals the correct water head within a certain time tl2, i.e. it is full, the subsequent step will be carried out, otherwise the special cycle PF, detailed in the following with reference to Fig. 2, will be activated;

13 a second wash water supply, also carried out in the static operating condition of the machine, until the optimum quantity for starting one of the active phases of the machine specified by the selected program, such as a cold prewash phase, is reached;

14 actuation of the wash pump and start of the water circulation in the hydraulic circuit of the dishwasher;

15 a second check operated by both pressure sensors for a certain time tl5: the check verifies whether the values of the wash water pressure detected by the pressure sensors are above a certain threshold.

This threshold is calculated in such a way as to provide that a washing with a pressure at least equal to the predetermined threshold value ensures an effective mechanical action of the jets of the sprayers onto the kitchenware to be washed, as well as the correct operation of the wash motor pump assembly.

At this point, if both pressure sensors (the pressure switch and the second pressure switch called "high pressure switch") reach the full condition within the time tl5, i.e. exceed the above-mentioned threshold values, the method 1 will implement the subsequent phase 18 of the selected wash cycle, thereby confirming its continuation. Otherwise, i.e. if the hydraulic pressure detected by one of the two sensors does not reach the predetermined threshold value, the method 1 will implement the following subsequent steps:

16 a third water supply, which can be carried out when the wash pump is activated, i.e. in dynamic operating conditions; 17 a third check of the pressure sensors for a time tl7: if both sensors are full, i.e. the problem of the clogged filters has been solved, the operation will continue with the subsequent phase 18 of the selected wash cycle, otherwise the special cycle PF will be activated.

The wash method 1, in the presence of pressure conditions sufficient to implement the subsequent phase of the selected wash cycle, will continue the selected wash cycle 18 until one or both pressure switches go empty for a certain time tl9: such step is indicated with 19 in the method 1. In this latter case, the method 1 will cause the activation of the special cycle PF.

The wash method 1 is basically characterized by the fact that the first, second and third checks operated by the pressure sensors 12, 15, 17 calculate if the full conditions of the sensors are reached within a certain time tl2, tl5, tl7, in order to understand whether the hydraulic circuit filters are free or clogged by residual dirt from previous washings. Instead, the additional check operated by the sensors during step 19, which takes place continuously during the entire washing, verifies if, for a time interval tl9, at least one of the sensors is always empty: such a check verifies a possible clogging of the filters during the washing. The activation of the special cycle PF therefore depends on the detection of the pressure parameter as a function of time, and permits to discern if the filters are clogged by residual dirt from previous washings or if there is accumulation of dirt during the washing. This allows to adapt the subsequent special cycle PF, if required, to a specific situation, e.g. by providing for a sequence of phases appropriately aimed at the different clogging situations.

In the event that, for one of the above-mentioned reasons, the filter cleaning cycle PF is activated during the wash method 1, the latter will continue by executing this special cycle PF substantially as a replacement for the normal wash program preselected by the user, so as to implement an actual and effective kitchenware washing in the dishwashing machine, as explained later. This effect is the basis of the inventive idea of the above-mentioned method and special wash cycle.

It will now be described, with reference to Fig. 2, the way in which, according to the present invention, the special filter cleaning cycle is implemented when the wash method 1 commands its execution. Fig. 2 shows a schematic diagram of the operation of the special cycle PF, wherein the X-axis indicates the time variable and the Y-axis indicates the temperature variable in almost the whole representation (an exception is, for example, phase 32). The special cycle PF is illustrated with particular reference to an activation taking place during o immediately before a wash phase specified by the basic program selected by a user. The principles of execution of such a special cycle PF are however valid for its activation during the execution of any phases of the wash method 1, i.e. of the selected wash cycle 18. This fact will be made clearer later.

The special cycle PF starts with a water supply phase 30 in addition to the water already present in the tub, wherein a first quantity of water ΔQj is supplied, i.e. added to the previous quantity. Aimed to understand the reason for the execution of this water supply phase 30, as well as of all the subsequent water supply phases, below there is a description of the operating condition of the undertub components of a dishwashing machine, in particular in an operating condition of the machine with the filters clogged by solid dirt. Such a condition is described with particular reference to Figures 3 and 4, which show a schematic sectional view of a part of the undertub area of the dishwashing machine according to the invention, in the condition of absence of water (Fig. 3) and in the condition of presence of water and clogged filters (Fig.4), respectively.

In short, being these components known, in the undertub area of the dishwashing machine, globally indicated with 50, there is an upper filter 51 having a central filter cup 52 protruding internally into a pit 53 of the dishwashing machine. An additional filter 54 is associated to the upper filter 51, and in particular it surrounds the filter cup 52, so that all the water or lye dripping into the tub is conveyed into the filter cup 52 and subsequently passes through this additional filter 54 before being collected inside the pit 53. At the bottom of the pit 53, there are a first outlet 55, which conveys the filtered water or lye towards a wash pump of the dishwashing machine, which performs the water recirculation, and a drain outlet 56 that conveys the water or lye to a drain pump for its elimination into the sewer. Said wash and drain pumps, as well as all the structural elements of the dishwashing machine suitable for implementing its correct operation, are not illustrated or described below for simplicity's sake. The water supplied to the wash tub is either filtered in the upper filter 51 in a known manner or conveyed and filtered through the central filter cup 52 and the additional filter 54, thus ending up in the pit 53 and leaving the dirt inside the filters 51 , 52 and 54. That same dirt may be decomposed by the washing chemical agents present in the lye, thereby unclogging the filters 51, 52 and 54.

The operating condition of the dishwashing machine with the hydraulic circuit for the recirculation of the water or lye in the presence of a large quantity of solid dirt, i.e. with the filters 51, 52 and 54 clogged, is shown in Fig. 4. The dark gray area indicates the lye with solid dirt SS, whereas the light gray area indicates the water A or the lye that passes through the filters and is suitable for being recirculated within the hydraulic circuit of the dishwashing machine by the wash pump. From here, as known, it arrives at the sprayers and is sprayed onto the kitchenware in the tub. In the operating condition of Fig. 4, the solid dirt SS prevents the water from passing freely through the mesh of the filters 51, 52 and 54, and the flow is therefore slowed down. As a result, the accumulated water head is lower than when the filters 51, 52 and 54 are free from dirt. A pressure switch in fluid connection with the inside of the pit, where the water that will be used for the washing is filtered, in condition of clogged filters generally measures a water head which is lower than that required for the correct operation of the wash pump, and therefore signals an empty condition to the machine management and control system. This information is received, interpreted and processed as appropriate by the machine management and control system in order to implement subsequent actions of the wash method. The pressure switch and its connections with the inside of the pit 53 are not shown in Figures 3 and 4 for simplicity's sake.

For a correct understanding of the phenomenology detectable in the dishwashing machine in the condition of clogged filters as shown in Fig. 4, it is important to point out the following characteristics: a) the central filter cup 52 is shaped with an upper portion 57 which, besides a winged appendix 57 A with the function of facilitating the manual removal of the whole upper filter 51 from the bottom of the dishwasher tub, also has a grid 57B accessing to a duct, not represented here for simplicity's sake, which is in direct connection with an annular section 58 located between the central filter cup 52 and the additional filter 54; b) the pressure switch in the pit, for the reasons explained later, may signal a full condition, i.e. a pressure exceeding a certain optimum threshold, even in the presence of an actual water head much lower than that required to ensure the correct operation of the wash pump.

As regards the characteristic a), i.e. the presence of the grid 57B on the upper portion 57 of the filter cup 52, Fig. 4 shows a configuration of the water A and of a solid dirt SS in the condition of clogged filters and continuous operation of the hydraulic circuit of the washing machine, before the intervention of the filter cleaning special cycle.

In the above condition, in fact, only the quantity of water Al can pass through the additional filter 54, instead of the theoretical quantity with respect to the hydraulic system, and in particular the wash pump, has been sized. On the contrary, if the continuous operation of the wash water recirculation hydraulic circuit is interrupted, the water has time to pass through even when the filters 51, 52 and 54 are particularly clogged. The clogging of these filters is largely caused by the solid dirt accumulation that is present on the kitchenware in the tub and not removed from the user before putting the kitchenware into the wash tub, or not disgregated by the thermal and chemical action of the lye, or not removed from the wash water precipitating onto the tub bottom and inside the central filter cup 52, through the mesh of which, however wide, the solid dirt cannot pass.

The phenomenon of the solid dirt accumulation inside the central filter cup 52 is promoted by the funnel-like shape of the upper filter 51 and in general of the dishwashing machines tub bottom. The solid dirt thus settles initially on the bottom of the filter cup 52, and then its level rises until it definitely hinders the passage of the lye or wash water in the annular section 58. In practice, a plug is formed which from the funnel bottom grows progressively until it clogs the whole cylindrical part of the filter cup 52, and possibly even the bottom of the upper filter 51. More dirt accumulates also in the annular section 58, in that the fine mesh of the additional filter 54 does not allow the passage of dirt inside the pit 53.

In the light of what has been explained so far, in the condition of clogged filters 51, 52, 54 and with a certain quantity of water circulating in the wash tub of the dishwasher, the lye with solid dirt SS present on the tub bottom, i.e. which has not filtered into the pit 53, reaches the level indicated with SSI. Said level SSI generally does not allow the lye to pass through the grid 57B incorporated in the upper portion 57 of the filter cup 52, which represents a channel not susceptible of clogging because the solid dirt tends to accumulate on the bottom of the wash tub. Consequently, one of the reasons for the execution of the water supply phase 30 in addition to the water already present in the tub, at the beginning of the special cycle PF, is to allow the lye to reach said grid 57B and overflow directly into the annular section 58. As a result, this lye, which is substantially free from solid residues because these tend to precipitate onto the tub bottom and from there into the central filter cup 52, passes easily through the additional filter 54, contributing to increase the quantity of water Al and to restore the correct operating conditions of the dishwashing machine wash pump. As regards the characteristic b), such a condition takes place when there is a fluid communication suitable for transmitting a hydraulic pressure between the quantity of water Al and the central lye column present in the central filter cup 52 in conditions of clogging. In such a case, the pressure switch does not merely detect the hydraulic pressure caused by the hydraulic head related to the quantity of water Al present in the pit 53, but substantially detects the hydraulic head related to the water column above, i.e. the lye present on the whole bottom of the wash tub. This is the reason why, in the dishwashing machine according to the present invention, a second pressure switch is used which dynamically detects the pressure of the wash water actually circulating in the hydraulic circuit. In particular, this additional pressure switch, called "high pressure switch", is inserted downstream of the delivery of the wash pump, as illustrated and described in the Italian Patent Application No. TO2003A000256 in the name of the present Applicant, whose teachings are incorporated for reference in the present description. Said additional pressure switch has the function of checking the actual hydraulic pressure existing in the hydraulic circuit of the machine, not the sometimes fictitious pressure measured by the pressure switch in the pit. Advantageously, the solution with double pressure sensor or pressure switch permits to monitor the actual pressure present in the hydraulic circuit of the dishwasher, further avoiding the risk of incorrect operation of the wash pump.

After having explained a first reason for the implementation of a water supply phase, let us resume the explanation of the operation of the special cycle PF as a part of a more general wash method.

Other reasons supporting such additional phases can be found in the fact that a larger quantity of water permits a better dissolution of the dirt in the tub and the collection of a larger quantity of water in the pit 53. As a result, it is more likely that the filters are cleaned by the mechanical action of a larger quantity of water occupying the bottom of the wash tub, which consequently filters into the pit 53 in less time. The special cycle PF then continues with the following phases:

31 a first intermittent washing, which is implemented for a certain first time Δtj with the resistances, provided for warming up the wash water, being activated in order to reach a first temperature Tj;

32 a pit washing phase, made up of repeated drain and supply operations (twice in Fig. 2) of a second quantity of water ΔQ ;

33 a second intermittent washing, which is implemented for a certain second time Δt₂ with the resistances, provided for warming up the wash water, being activated in order to reach a second temperature T₂;

34 an additional pit washing phase, with a single drain and supply operation of a third quantity of water ΔQ₃ ;

35 an intermittent rinsing, which is implemented for a certain third time Δt₃ at a third temperature T₃ with the resistances, provided for warming up the wash water, being deactivated;

36 a pressure check phase carried out through the sensors for a check time Δt_c. During the above sensor check phase 36, which takes place with the wash pump activated, there is also the possibility that both sensors are in full condition; in such a case, the machine will carry out a normal rinsing 37 in continuous operation for a fourth time Δ j and at a fourth temperature T₄. If, on the contrary, one of the two pressure sensors goes empty during the check time Δtc, i-6- it does not measure a certain pressure suitable for ensuring a sufficient flow rate to the pump within the predetermined time and therefore an effective washing, the machine will implement a subsequent intermittent rinsing phase with a subsequent new check phase carried out in the same way as the previous one. If this latter check phase is not passed, the dishwashing machine will switch to the filter cleaning alarm condition, i.e. it will stop the wash program and inform the user that the filters must be manually cleaned, for the reason that the wash method 1 , during the special cycle PF, could not unclog the filters, at least partially, from the solid dirt.

It can be noted that, unlike some of the known dishwashers, the user can be warned about the presence of clogged filters at a point of the wash method when a complete washing cycle has already been performed through the intermittent phases, therefore ensuring an effective result of the washing of the kitchenware even if the special cycle PF has not been able to solve the problem.

The special cycle PF is performed with different modalities with respect to the case illustrated in Fig. 2, depending on which different phase of the wash method 1 is implemented. The particular special cycle PF described here refers to the case in which it is commanded at the beginning of the wash program 1, specifically at the step 12 or 17. It comprises a series of wash phases of intermittent type, which can be identified as prewash, wash and rinse phases, respectively, and therefore it is suitable for carrying out a whole complete washing. The steps sequence described is clearly modified by the dishwashing machine management and control system when the special cycle PF is commanded at a more advanced point of the wash program, i.e. at the step 19 of the wash method 1, with reference to Fig. 1. The phases of the special cycle PF are conveniently reduced with respect to those illustrated, in that some wash phases have already been carried out in normal operation conditions of the dishwashing machine. The phases of the special cycle PF may be further modified by adapting the times Δt_c, Δtι-Δt», the temperatures Tj-T₄ and the quantities of water ΔQj-ΔQ drained and supplied, or by determining a different sequence of the phases to be implemented; all this in order to obtain a better optimization of the washing of the kitchenware in accordance to the experimental results of an accurate engineering of the wash method according to the present invention. In particular, such times Δt_c, ΔtpΔ _t may be varied according to the pressure values detected by the sensor means continuously and/or during the pressure sensor check phases 12, 15, 17, 36, so that the correct hydraulic head in the pit is always ensured at any moment of each intermittent phase 31, 33, 35. The following fact must certainly be highlighted: by alternating an intermittent active phase 31, 33, 35 with a water supply or drain and supply phase 30, 32, 34, it is possible to determine a certain sequential mechanical pumping action due to the intermittent action of the wash pump, as well as the phenomenology already described in regard to the reasons for the execution of phases with water addition. All this creates conditions suitable for an effective unclogging of the filters 51, 52, 54 of the dishwashers from the solid dirt, which takes place through a combined action of mechanical type (the intermittent pumping of the wash pump and of the drain pump in presence of abundant water), of thermal type (when the wash water is warmed up to the temperatures T]-T₄), and of chemical type (the washing agents dissolved in the water or lye) exerted on the residual dirt.

The gist of the special cycle PF and of the wash method which is the subject of the present invention, is precisely the realization of one or more wash and/or rinse phases 31 , 33, 35 of "intermittent" type.

Each intermittent phase, either washing or rinsing, hot or cold and implementing or not the dispensing of any washing agents or brighteners, has the characteristic as shown in Fig. 5, i.e. it is substantially implemented according to a periodic mode M consisting of the following steps: Start The machine management and control system commands the start of the intermittent phase to be executed;

Ml first periodic mode: the wash pump is activated ON at full and constant speed for an actuation time Δt'; M2 second periodic mode: the wash pump is deactivated OFF for a stop time Δt"; M3 the sequence Ml, M2 is repeated until the management and control system records the total time Δt_ls Δt₂, Δt₃ of the overall duration of the related intermittent wash and/or rinse phases 31, 33, 35.

The first periodic mode Ml permits to carry out, for a limited time Δt', an effective washing as a result of the fact that a previous phase has ended with the wash pump in OFF position for a certain time, thereby allowing the wash water or the lye to filter inside the pit 53 until a hydraulic head, substantially made up of the entire volume of the pit 53, is obtained. After the actuation time Δt', unless meanwhile the filters have not unclogged themselves from the solid residues, the water head decreases again to values that would not ensure an optimum operation of the hydraulic system of the dishwasher. At this point the second periodic mode M2 is implemented, thereby the wash pump is OFF for a stop time Δt". During this time, the water is allowed to re- establish the optimum water head and therefore the quantity of water Al sufficient for an effective hydraulic system operation.

For reasons of rationalization and an easy implementation of the periodic mode M as well as of the special cycle PF, the actuation time Δt" and the stop time Δt' are constant for the whole duration of every single phase t_x. Nevertheless, said times Δt', Δt" could also be calculated as a function of the pressure values detected by the sensor means of the dishwasher, so as to be adapted to the actual hydraulic head present in the pit 53 of the dishwasher. For the reasons explained so far, the wash pump of the dishwasher according to the present invention operates advantageously in the presence of a proper head due to a sufficient hydraulic head being present in the pit, i.e. with the correct water flow rate, being able to arrive at the jets of the sprayers in the tub with sufficient energy to perform a good mechanical action onto the kitchenware to be washed. Advantageously, the motor pump assembly operates correctly, i.e. with proper head, in any case; this definitively eliminates the risk of failure of the wash pump rotor shank or of blowing out of the associated electric motor.

The wash method 1, through the implementation of the special cycle PF, always performs a satisfactory washing of the kitchenware by executing the intermittent wash and/or rinse phases 31, 33, 35, for the reason that such phases are carried out with the wash water or the lye at an optimum pressure value for substantially the whole time interval in which said phases are activated. Furthermore, the special cycle PF, once activated, completes an effective wash cycle in a manner substantially independent from the wash method 1. A further advantage of the dishwashing machine incorporating the wash method 1 according to the invention, is to ensure at all times the monitoring of the actual pressure conditions of the lye in the hydraulic circuit during the activation of the wash pump, as per using a double check of the pressure value, i.e. a check in the static condition inside the pit 53 and a check of the dynamic pressure at the outlet of the wash pump. This double check definitively eliminates the risk that the machine operates with insufficient water pressure and flow rate.

The above-listed technical advantages are obtained by means of technical modifications which are very simple, reliable and economic to carry out in the known dishwashing machines.

It is clear that many variations to the improved method and the special wash cycle, as well as to a dishwashing machine implementing said method according to the invention may be made by a person skilled in the art without departing from the novelty principles contained in the innovative idea; and it is clear that in the practical realization of the invention the components may have shapes different from those described or be replaced with other technically equivalent elements. For instance, the special cycle PF shown in Fig. 2 is just one of the possible examples of implementation of said special cycle by the dishwashing machine management and control system. Said implementation can therefore vary according to the wash program initially selected for start by a user, adapting itself to the selected basic program substantially through the execution of "intermittent" phases, which may be alternated with water or lye supply and drain phases, or wash water warm-up phases. The various phases 30-37 of the special cycle PF may also be combined in a different way, just as it is possible to add different phases from those illustrated, without departing from the novelty principle: i.e. that all the remaining active phases, wherein water circulation is implemented in the dishwasher hydraulic circuit and carried out after having detected that one of the sensor means or pressure switches is operating in empty condition and after the activation of the special cycle PF, are implemented by the execution of intermittent phases according to the application example illustrated and explained with reference to Fig. 5.

It is also clear that in each intermittent phase 31, 33, 35, just like in any other phases, the temperatures the times tι-t₄ and the quantities of water ΔQr ΔQ₃ can be optimized depending on the wash program selected by an operator through an accurate engineering process.

As regards the periodic mode M, the actuation time Δt' and the stop time Δt" of the wash pump may advantageously be either fixed, i.e. obtained through experimentation, or variable as a function of the pressure values detected by the pressure switch located in the pit of the dishwasher and/or further means for detecting the level of the water present in the pit and/or detectors of the dynamic pressure value in one or more points of the hydraulic circuit.

The times Δt', Δt" may therefore vary depending on the sensor means capable to detect continuously and precisely the flow rate and/or the pressure of the water in the pit or in the hydraulic circuit, moment by moment, in such a way as to allow the dishwashing machine management and control system to establish a prpper stop time Δt" and a proper actuation time Δt' at any moment for each intermittent phase according to the selected wash program.

Both the actuation time Δt' and the stop time Δt' ' may also be variable both within the duration Δt_x of a single intermittent phase and between two different intermittent phases.

As a result of the above considerations, the special cycle PF advantageously permits to obtain higher levels of effectiveness and versatility when applied to any dishwashing machine having a hydraulic system fitted with at least one pressure sensor. In a variation embodiment of the dishwashing machine management and control system according to the present invention, using remote microcontrollers storing the wash programs to be implemented or their updates, aimed to implement and/or modify the wash method according to the present invention, as well as the single special cycles PF, is further provided. In substance, a part of the control logic of the dishwashing machine can be implemented by using external units, in particular remote microcontrollers. It is also possible to realize a convenient embodiment of the undertub configuration related to the dishwashing machine according to the present invention. In particular, it is possible to shape the filter cup in a slightly different way with respect to that illustrated and described with reference to Figures 3 and 4. The components which are common to both the above-mentioned embodiment and the undertub representation are recalled with reference to Fig. 3. The embodiment consists in realizing a supplementary filter to be inserted into the top of the central filter cup 52, so as to be lifted with respect to the upper filter 51 to a certain height over the winged appendix 57A of said cup. The supplementary filter is positioned so that the wash water or the lye, before entering the central filter cup 52, must necessarily pass through the supplementary filter. It is made up of a rather wide mesh, so that only a solid dirt having a certain volume is trapped, hence preventing it from clogging the central filter cup 52. It may for instance have a cylindrical shape, be made up of one or more pieces, or be integrated in one piece with the filter cup.

Advantageously, said supplementary filter permits to access more easily to the wash water in the filter cup in case of solid dirt accumulation on the dishwasher tub bottom, and ensures a lower solid dirt accumulation inside the central cup. As a matter of fact, the water can always pass through said supplementary filter in correspondence with those areas which are higher with respect to that of the tub bottom, because the solid dirt tends to deposit onto the bottom. The times required for filtering the lye are therefore reduced, with a consequent reduction also of the times in which the wash pump must remain stationary in order to allow the pit to re-establish the correct hydraulic head during the execution of an intermittent phase of the filter cleaning special cycle.

Claims

1. A wash method in a dishwashing machine, of a type suitable for implementing at least one phase for checking the value of the pressure (12, 15, 17, 36) existing in one or more points of the hydraulic circuit of said dishwashing machine through sensor means in order to carry out subsequent actions (13, PF, 16, 18) of said method (1), which are commanded by a machine management and control system suitable for detecting and processing information, characterized in that it comprises a special wash cycle (PF) which is capable of, when said sensor means in a pressure value check phase (12, 15, 17) provide values which are below a certain threshold suitable for ensuring a sufficient head to a wash pump of said hydraulic circuit in order to carry out an effective washing of the kitchenware, accomplishing pressure conditions in the hydraulic circuit of the dishwasher similar to those attainable in normal operating conditions, i.e. with the filters (51, 52, 54) of the same hydraulic circuit unclogged from residues or solid dirt.

2. A method according to the previous claim, characterized in that said special wash cycle (PF) is suitable for realizing hydraulic pressure conditions in the hydraulic circuit of said dishwashing machine substantially equivalent to those attainable in normal operating conditions, i.e. with the filters (51, 52, 54) of the same hydraulic circuit unclogged from residues or solid dirt.

3. A method according to the previous claim, characterized in that said special wash cycle (PF) is suitable for realizing a hydraulic pressure in the hydraulic circuit of said dishwashing machine substantially equivalent to that attainable in normal operating conditions, i.e. with the filters (51, 52, 54) of the same hydraulic circuit free from residues or solid dirt.

4. A method according to one or more of the previous claims, characterized in that the logic of execution of said special wash cycle (PF) is based on the time variable.

5. A method according to the previous claim, characterized in that said special wash cycle (PF) implements a number of intermittent phases (31, 33, 35), i.e. phases that carry out steps (M) which are implemented according to a periodic mode during each of said phases (31, 33, 35).

6. A method according to the previous claim, characterized in that said steps (M) of said intermittent phases (31, 33, 35) of said special wash cycle (PF) are repeated according to a constant periodic mode for the whole duration of each of said intermittent phases (31, 33, 35).

7. A method according to claim 5 or 6, characterized in that said steps of said intermittent phases (31, 33, 35) of said special wash cycle (PF) include a first step (Ml), wherein the wash pump of the dishwashing machine is activated for a certain first time interval (Δt'), and a second step (M2), wherein said wash pump is deactivated for a certain second time interval (Δt").

8. A method according to the previous claim, characterized in that said time intervals (Δt', Δt") of said steps (Ml, M2) of said intermittent phases (31, 33, 35) of said special wash cycle (PF) are constant during the execution of each of said intermittent phases (31, 33, 35).

9. A method according to claim 7, characterized in that said time intervals (Δt', Δt") of said steps (Ml, M2) of said intermittent phases (31, 33, 35) of said special wash cycle (PF) are variable during the execution of each of said intermittent phases (31, 33, 35).

10. A method according to the previous claim, characterized in that said time intervals (Δt', Δt") of said steps (Ml, M2) of said intermittent phases (31, 33, 35) of said special wash cycle (PF) are variable depending on the pressure parameters detected by said sensor means of said dishwashing machine.

11. A method according to one or more of the previous claims, characterized in that said intermittent phases (31, 33, 35) of said special wash cycle (PF) are executed at certain temperatures (T[-T₄) of the wash water specified by the same special wash cycle (PF).

12. A method according to one or more of the previous claims, characterized in that said special wash cycle (PF) includes supply phases (30) and/or drain and supply operations (32, 34) of water quantities in the wash tub.

13. A method according to at least claims 5 and 12, characterized in that said special wash cycle (PF) comprises said supply phases (30) and/or drain and supply operations (32, 34) alternated with said intermittent phases (31, 33, 35).

14. A method according to one or more of the previous claims, characterized in that said special wash cycle (PF) implements said phases and/or operations (30-37) according to an order established on the basis of the specific phase of said pressure value check phases (12, 15, 17, 36) of said method (1) wherein it is activated.

15. A method according to one or more of the previous claims, characterized in that it implements said special wash cycle (PF) according to an activation logic based on the time variable.

16. A method according to the previous claim, characterized in that it implements said special wash cycle (PF) on the basis of pressure parameters detected by said sensor means. 17. A method according to the previous claim, characterized in that it comprises sensor check steps (12, 15,

17) according to which said special wash cycle (PF) is implemented when the pressure value(s) detected by said sensor means do not reach a certain predetermined threshold within a certain detection time (tl2, tl5, tl7).

18. A method according to claim 16, characterized in that it comprises additional sensor check steps (19) according to which said special wash cycle (PF) is implemented when the pressure value(s) detected by said sensor means drop below a certain predetermined threshold within a certain detection time (tl7).

19. A method according to claims 17 and 18, characterized in that it performs said sensor check steps (12, 15, 17) at the beginning of said method (1), and in that it performs said additional sensor check steps (19) in a subsequent phase.

20. A method according to one or more of the previous claims, characterized in that said special wash cycle (PF) comprises one or more water supply phases (30), whererin a certain quantity of water (ΔQ ) is supplied in addition to that already present in the wash tub.

21. A method according to one or more of the previous claims, characterized in that said special wash cycle (PF), once started, proceeds autonomously and substantially replaces the normal wash program selected by the user.

22. A method according to one or more of the previous claims, characterized in that said special wash cycle (PF) comprises at least one phase (36) for checking the pressure in the hydraulic circuit of the dishwashing machine.

23. A method according to the previous claim, characterized in that said special wash cycle (PF), following said phase (36) for checking the pressure in the hydraulic circuit of the dishwashing machine, in the event that the pressure values read by the sensor means exceed the critical threshold suitable for ensuring an effective washing in normal operating conditions, carries out further normal, i.e. not intermittent, wash phases (37).

24. A management and control system of a dishwashing machine, implementing the wash method according to one or more of claims 1 to 23.

25. A dishwashing machine, of a type comprising a hydraulic circuit and a machine management and control system, said machine management and control system being suitable for commanding at least the activation of a wash pump and a drain pump of said dishwashing machine, as well as for interpreting and processing the pressure values sent by sensor means of said machine through a control logic storing at least one wash program for said dishwashing machine; characterized in that said dishwashing machine management and control system is susceptible of implementing the wash method according to claims 1 to 23.

26. A dishwashing machine according to the previous claim, characterized in that said hydraulic circuit of said machine comprises at least one pressure sensor suitable for measuring the dynamic pressure within said circuit, and in particular downstream of the wash pump.

27. A dishwashing machine according to claim 21 or 22, characterized in that said hydraulic circuit of said machine comprises an additional sensor or pressure switch which is capable of measuring the pressure generated by the hydraulic head present in the pit (53).

28. A dishwashing machine according to one or more of claims 21 to 23, characterized in that the undertub area of said machine comprises a supplementary filter which is inserted into the top of a central filter cup (52), so as to be lifted with respect to an upper filter (51) at a certain height up to an eventually present winged appendix (57A) of said filter cup (52); said supplementary filter being located so that the wash water or the lye, before entering the central filter cup (52), must necessarily pass through said supplementary filter.

29. A dishwashing machine according to the previous claim, characterized in that said supplementary filter includes a rather wide mesh, so that only the solid dirt having a certain volume is trapped, therefore preventing it from clogging said central filter cup (52), in particular said supplementary filter being able to have a cylindrical shape, made up of one or more pieces, or integrated in one piece with the filter cup.