EP2757930B1

EP2757930B1 - Dishwashing machine with drying system

Info

Publication number: EP2757930B1
Application number: EP12780840.0A
Authority: EP
Inventors: Gloria Ghezzi; Gianluca Benedetto; Maria Chiara Brugnera
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2011-09-20
Filing date: 2012-09-18
Publication date: 2015-11-25
Anticipated expiration: 2032-09-18
Also published as: EP3000377B1; EP3000377A1; PL2757930T3; EP2757930A1; WO2013042036A1

Description

Field of the invention

The present invention relates to a dishwashing machine having a drying system.

Prior art

Drying systems that equip modem-day dishwashers are substantially of a closed-circuit type or open-circuit type; the latter may be subdivided into systems of natural circulation or else systems of forced circulation of the air.
In dishwashers with closed-circuit drying systems a fan sucks the damp air from the tub, and then re-introduces it into the tub after it has been dehumidified. For this purpose, between the outlet for the damp air of the tub and the intake mouth of the fan a condenser device or the like is provided, whilst between the delivery of the fan and the inlet for the air into the tub a heating resistor may be operative, to render the drying process more efficient (see, for example, FR-A-2491322 ).
In open-circuit dishwashers with natural ventilation, instead, between an inlet and an outlet of the tub a flow of air is induced in a non-forced way, i.e., without the aid of a fan, with the air coming from the outside that progressively replaces the damp air present in the tub (see, for example, EP-A-0752232 ). In the case of open-circuit machines with forced ventilation, instead, the outlet for the damp air is in fluid communication with the inlet of an aspirator, the outlet of which is, instead, in fluid communication with the environment external to the tub, usually via a condenser device. In these machines, the tub is also provided with at least one opening aimed at enabling change-over of air, i.e., inlet in a non-forced way into the tub of air coming from the external environment (see, for example, EP-A-0721762 ).
From WO 2009/008828 , on which the preamble of Claim 1 is based, there is also known a dishwasher, the open-circuit drying system of which includes a first fan for introducing in a forced way into the tub drying air taken in from the external environment, said air being previously heated in order to improve the drying efficiency. More in particular, the tub has an outlet opening, defined in an upper area of a first side wall, in which the first fan is operative. Said fan takes in the damp air in a forced way to introduce it into a condensation conduit having a body that extends generally parallel to the aforesaid first side wall, with the dehumidified air that is then expelled into the external environment. In this solution, the outlet for the damp air is defined in the shell of the door of the machine, which forms the front wall of the wash tub, with the fan and the condensation conduit that are housed in the gap inside the door. The system moreover includes a second fan, positioned in a housing space defined by a basement of the tub. The casing of the second fan is mounted in such a way that the axis of rotation of the corresponding impeller, and hence the axis of the corresponding intake mouth, is substantially vertical; connected to the delivery of the casing is a conduit having a generally flattened configuration, which rises along a stationary side wall of the tub, as far as an inlet opening for the drying air. Operative between the delivery of the casing of the second fan and the aforesaid conduit is an electric heater, designed to heat the air in order to improve the efficiency of the drying process.
The solution of drying circuit described in WO 2009/008828 is relatively complicated, costly, and cumbersome, and not fully efficient.

Aim and summary of the invention

In accordance with a first aspect, the present invention basically aims to provide a dishwasher equipped with a system for drying dishes with open circuit for the air that is simple and inexpensive to produce and compact in structure, and at the same time is such as to guarantee a high efficiency of operation. The above aim is achieved by a dishwashing machine having the characteristics specified in Claim 1. Preferred characteristics are indicated in the dependent claims 2-14. The claims 1-14 form an integral part of the technical teaching provided herein in relation to the invention.
In summary, according to the aforesaid first aspect of the invention, a dishwashing machine of the type indicated at the preamble of claim 1 is characterized in that:

the inlet for the drying air into the tub includes a chimney that extends through the lower wall of the tub itself and has an upper end and a lower end, which open on opposite sides of said lower wall, to the upper end there being associated a chimney cap defining a substantially labyrinth-path and to the lower end there being coupled an outlet end of the first conduit that delivers the drying air;
the aforesaid first side wall, that the first portion of the condenser device faces, is a stationary wall of the tub;

the outlet for the damp air from the tub is defined in the upper wall of the tub itself; and
the condenser device has a second portion, which generally faces the upper wall of the tub and extends between the outlet for the damp air and an upper region of the first portion of the body of the condenser device.

The fact that the outlet for the damp air is defined in the upper wall of the tub facilitates evacuation of the steam, which tends in a natural way to rise upwards and to accumulate at the upper wall. The relative position between the inlet opening for the drying air and the outlet opening for the damp air, in walls opposite to one another, enables the flow of drying air to impinge in an efficient and substantially uniform way upon the load of dishes present in the tub, supported on customary racks. In the known solution referred to above, in front of the inlet for the drying air there may be present a dish (a plate or a pan), with a consequent perturbation of the flow of the forced air at inlet, and said drawback is overcome in the case of the present invention. In the known solution referred to above a dish may be set also in front of the outlet opening for the damp air. This problem is, instead, overcome, according to the invention, by providing the outlet in the upper wall of the tub.
The presence of the chimney mentioned previously, provided with the corresponding labyrinthine cap, prevents, in the course of normal washing operations, water from penetrating into the conduit for supply of the forced air into the tub.
The fact that the condenser is associated to stationary walls of the tub, i.e., a side wall and the upper wall, simplifies realization of the condensation part of the system, which does not have to be integrated in the door of the machine. Said solution renders the system very compact.
Advantageously, in a preferred embodiment, also the part of the system that comprises the fan, the first conduit, and the heating means, can be mounted entirely in the housing space of the basement of the machine, i.e., underneath the lower wall of the tub, with further advantage as regards compactness of the drying system as a whole.
In one embodiment, the casing of the fan is mounted in the housing space of the basement with at least one of the axis of rotation of the impeller and the axis of the intake mouth oriented substantially horizontally, or in any case transverse with respect to a height dimension of the basement. In the case where the intake mouth faces the inside of the basement - as in the attached figures - the air at inlet to the fan has already been at least slightly heated in so far as it can receive heat from other operating components of the machine present in the basement, to the advantage of the efficiency of the process (consider, for example, the motor of the washing pump and/or of the discharge pump, which, following upon their operation, heat up at least slightly, and can hence yield heat to the surrounding air; the body itself of the collection sump of the wash tub, mounted on the lower wall of the tub and projecting within the basement, can yield heat to the air). The arrangement referred to above moreover enables a transverse intake flow to be obtained that affects to a large extent the housing space of the basement, thus affecting a number of functional components, which can yield heat to the air.
In another embodiment, the casing of the fan can be oriented in such a way that the intake mouth faces the outside of the basement, and in particular the side corresponding to the side wall of the tub that the vertical portion of the condenser faces, inside which the condensation path for the air is defined. Basically, in this way, the intake mouth is located in an area that is set underneath the lower end of the aforesaid vertical portion. This enables intake of the air that surrounds the condenser, favouring a heating of the condenser itself and hence increasing the condensation efficiency. For this reason, in a particularly advantageous embodiment, the vertical portion of the condenser can extend at at least a small distance from the corresponding side wall of the tub, in such a way that defined between the two parts is a gap, from which the air can be extracted in the aforesaid way, further improving the effect of condensation. The presence of this gap, on the other hand, contributes to improving the effect of condensation also when the intake mouth of the fan is oriented towards the inside of the basement, and not towards the outside.
In a preferential embodiment, the condenser has an outlet for the dehumidified air, which is located in the upper region of the vertical portion of the corresponding hollow body. Basically, hence, the inlet for the damp air in the vertical portion and the outlet for the dehumidified air are both set in the upper region of the same portion in which the condensation path is defined, in positions generally set alongside one another. In this way, the condensation path includes a descending stretch, which goes substantially from the horizontal portion of the body of the condenser device to the lower region of the vertical portion, and an ascending stretch that goes substantially from the aforesaid lower region to the aforesaid upper region, in which the outlet for the dehumidified air is located.
In this way, the dehumidified air can be made to come out upwards, in a position relatively remote from the basement, at the same time guaranteeing a condensation path that is relatively extensive in length. For this purpose, preferably, at least in a region at the aforesaid descending stretch of the condensation path, the body of the condenser device is substantially labyrinth-shaped. Once again preferentially, at the lower end of the vertical portion of the body of the condenser device, defined in a position that is substantially close to the end of the aforesaid descending stretch of the condensation path is a collection receptacle for the condensation water, said receptacle having a respective draining outlet.
The hollow body of the condenser device, comprising its various portions, has a generally flattened configuration and is preferably made of a single piece of thermoplastic material, in particular obtained via blow-moulding.
According to a further embodiment, the drying system can comprise a second fan, associated to the condenser device, for facilitating off-flow of the damp air from the tub and contributing to preventing undesirable increases in pressure inside the tub of the machine.
It should be also noticed that, in machines of the type described in WO 2009/008828 , it is necessary to prevent, during washing or rinsing steps, water sprinkled in the tub by the sprinkler members of the machine from entering the inlet opening for the drying air and hence reach, through the relevant piping, electrical parts of the machine, and in particular the motor of the fan (the air heating means being intrinsically protected from said risks). Also for this reason, the aforesaid piping has, in the upper stretch thereof, a bend at about 180° and, at the inlet for the drying air in the tub, there is associated a deflector member, that performs the function of shielding and addressing the flow downwards. Besides that, in front of the opening defined in the above said deflector there may be present a dish (a plate or a pan), with a consequent perturbation of the flow of the forced air at inlet. As said, additionally, the solution of drying circuit described in WO 2009/008828 is in general relatively complicated, expensive and cumbersome.

Brief description of the drawings

Further purposes, characteristics, and advantages of the invention will emerge clearly from the ensuing detailed description of an embodiment provided purely by way of explanatory and non-limiting example, with reference to the annexed drawings, wherein:

Figure 1 is a partial and schematic perspective view of a dishwashing machine according to a possible embodiment of the invention;
Figures 2 and 3 are partial and schematic perspective views, from different angles, of a lower portion of the machine of Figure 1;
Figures 4 and 5 are schematic perspective views, from different angles, of an assembly for blowing and heating the air of a drying system of a machine according to a possible embodiment of the invention;
Figure 6 is a schematic side elevation, in partial cross section, of some parts of the machine of Figure 1, including the assembly of Figures 3 and 4;
Figure 7 is a schematic perspective view of the parts of Figure 6;
Figure 8 is a schematic perspective view from beneath of a lower part of the machine of Figure 1;
Figure 9 is a partial and schematic perspective view of some components of a drying system of a machine according to a possible embodiment of the invention;
Figure 10 is a cross-sectional view of an inlet for the drying air into the tub of a machine according to a possible embodiment of the invention;
Figure 11 is a partial and schematic view from above of the assembly of Figures 3 and 4, in a possible preferential embodiment;
Figure 12 is a partial and schematic perspective view of an upper portion of the machine of Figure 1;
Figure 13 is a perspective view of a condenser device forming part of the drying system of a machine according to a possible embodiment of the invention;
Figures 14 and 15 are partial and schematic perspective views of respective portions of the condenser device of Figure 13; and
Figure 16 is a partial and schematic representation of a dishwashing machine according to an embodiment which does not form part of the invention, with a sorption drying system.

Description of preferred embodiments of the invention

Reference to "an embodiment," or "one embodiment" in the framework of the present description is meant to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as "in an embodiment" or "in one embodiment" and the like, that may be present in various parts of the present description do not necessarily all refer to one and the same embodiment. Moreover, the particular configurations, structures, or characteristics may be combined in any adequate way in one or more embodiments. The references used in what follows are only provided for convenience and do not define the sphere of protection or the scope of the embodiments.
It is moreover pointed out that in the sequel of the present description only the elements useful for an understanding of the invention will be described, it being taken for granted, for example, that the machine according to the invention comprises all the elements in themselves known for operation of a dishwashing machine, including an outer cabinet thereof, a user interface, a control system, pumps, level sensors, resistors, a sprayer system for spraying water on the dishes, etc.
Figure 1 is a schematic representation of a dishwashing machine 1 having a system for drying the dishes, according to a first possible embodiment of the invention. The machine 1 is illustrated limitedly to the parts of immediate interest for an understanding of the present invention. In this embodiment the machine 1 has a dish-drying system with a substantially open circuit.
The machine 1 comprises a basement 2 and a wash tub 3, supported by the basement 2. The basement 2, made for example of injection-moulded thermoplastic material, defines a housing space 2a, positioned within which are various functional components of the machine 1, amongst which, for example, a washing pump, a discharge pump, a pressure switch, a sump for collection of the washing liquid, etc., here not represented for reasons of greater clarity of the drawings.
The wash tub 3 is of a conception as a whole known, apart from the specific characteristics envisaged according to the above said first inventive concept, that are linked to the arrangement of the drying system. The tub 3 hence comprises a lower wall 3a, an upper wall 3b, and four side walls; in Figures 1 and 2 only the stationary side walls of the tub 3 are visible, i.e., the rear wall 3c, and the right and left-hand walls, designated by 3d and 3e; the fourth side wall of the tub 3, i.e., its front wall, is constituted by an inner shell of the door of the machine, here not represented (the so-called "counter-door"). From Figure 1 it may be noted how the left-hand wall 3e is provided with an opening 3e', at which, on the outside of the tub 3, a known multifunction device is mounted, through which the water coming from the water mains is introduced into the tub, according to modalities in themselves known; said device integrates the so-called "air-break" and can moreover fulfil venting functions to prevent, during operation of the machine, any overpressure within the tub 3 from arising. The presence of the aforesaid device is not in any case strictly linked to operation of the drying system described hereinafter.
Also from Figure 2 it may be seen how the lower wall 3a of the tub defines a central opening 3a', mounted at which is the aforesaid collection sump (not represented) integrating the filtering system of the machine.
The drying system of the machine 1 basically includes an assembly for blowing and heating the drying air, designated as a whole by 10 in Figures 1-3, and a condensation assembly, designated as a whole by 30 in Figures 1 and 3. As may be clearly seen, for example, in Figures 2 and 3, the assembly 10 is substantially installed within the housing space 2a of the basement 2, whilst the condensation assembly 30 (see Figures 1 and 3) extends substantially on the outside of the tub 3.
The assembly 10, represented in isolation in Figures 4 and 5, includes a body preferably formed in a number parts made of thermoplastic material assembled together. Within the assembly 10 there may be identified a fan, preferably of a centrifugal type, designated as a whole by 11. The fan 11 has a respective volute or casing 12, housed in which is an impeller 13, driven by a corresponding electric motor 14. The casing 12 has an intake mouth 12a, preferably substantially coaxial to the rotation axis of the impeller 13, and a delivery, not indicated. In the example of embodiment, the delivery of the casing 12 is obtained in a single piece with a descending portion 15a of a conduit, designated as a whole by 15, which connects the outlet of the fan 11 to an inlet for introducing drying air into the tub 3, described hereinafter. Said conduit 15, shaped in accordance with the above said second aspect of the invention, then includes an ascending portion, designated by 15b, which defines an outlet end 16 of the conduit 15.
The assembly 10 integrates, as has been said, also means for heating the drying air, which are preferably set along the conduit 15, upstream of the outlet end 16. The heating means may be of any known type and comprise, for example, an electrical resistance or a radiator integrating a plurality of resistors of a PTC type or a serigraphed resistor. In the figures, the heating means, designated by 17 only in Figure 5, are not fully visible if not limitedly to the corresponding electrical contacts, here of a faston male type. The heating means 17 are integrated in the assembly 10 preferably in a corresponding seat defined substantially in the aforesaid descending stretch 15a of the conduit 15, or at the inlet thereof, and hence slightly downstream of the outlet of the fan 11. From Figures 4 and 5 it may moreover be noted how the main body of the assembly 10 defines appendages 18 provided with corresponding pins 18a for anchorage of the assembly itself to the basement 2.
Figures 6-9 illustrate with different views an assembled condition of the assembly 10 (note that in Figures 6 and 7 the basement 2 and the side walls 3d, 3e of the tub are not represented, and that in Figure 9 also the representation of the lower wall 3a is omitted). Figure 10 is a cross-sectional view of a portion of the lower wall 3a of the tub, with the corresponding inlet for the drying air, whereas Figure 11 shows a part of the assembly 10, from above.
As may be noted in particular in Figures 6-8, in the machine 1 the inlet for the drying air is defined at the lower wall 3a of the tub. Said inlet includes a passage of the wall 3a, designated by 20, defined in the proximity of the right lower angle of the tub, and a tubular chimney 21, which extends through said passage, with interposition of fluid-tightness means and fixing means, having a structure in itself known and not indicated. As may be seen in particular in Figure 10, the chimney 21 has an upper end 21a and a lower end 21b, which open on opposite sides of the wall 3a, the upper end being at a height greater than the level reached by the water in the course of the washing or rinsing operations performed by the machine 1. Associated to the upper end of the chimney 20 is a cap or lid 22 (see also Figures 2 and 9), which defines a substantially shielded or labyrinthine path, whereas coupled to the lower end is the outlet end 16 of the conduit 15. Once again with reference to Figure 10, the lid 22 has inner walls 22a shaped for defining the aforesaid labyrinthine path, according to modalities known to the person skilled in the art, and has one or more openings 22b for off-flow of the drying air; preferably, but not necessarily, the outlet opening or openings 22b are located in the rear part of the chimney 22, i.e., its part opposite with respect to the centre of the tub 3.
From Figures 6-9 it may moreover be noted how - in the embodiment exemplified in the figures - the casing 12 of the fan 11 is mounted with the axis of rotation of the impeller 13 (and hence with the intake mouth 12a substantially sharing said axis) that is generally oriented in a horizontal direction, or in any case in a direction transverse to the height of the machine. In the example, the mouth 12a (see also Figure 2) faces the inside of the basement 2, where functional components are normally installed (such as the pumps and the sump), which can yield heat to the air taken in. Once again from Figures 6-9 there may be noted how, in accordance with the above said second inventive concept, the conduit 15 has a particular substantially V-shaped development, which comprises the aforesaid descending portion 15a and ascending portion 15b, provided between which is an intermediate elbow portion, designated by 15c, which is preferably set at a height lower than that of the motor of the fan 11. As may be seen, the conduit 15 extends substantially entirely in the housing space of the basement 2, underneath the lower wall 3a of the tub, with the portion 15a that is generally descending from the fan 11 to the elbow portion 15c, whilst the portion 15b is generally ascending from the elbow portion 15c to the inlet for the drying air, comprising the passage 20 and the chimney 21.
From the figures it may moreover be noted how, in a preferred embodiment, defined in a position substantially corresponding to the elbow portion 15c of the conduit 15 is a drain opening, designated by 23, via which any water that may collect in the area of the elbow portion itself can be evacuated from the conduit 15. Preferably, the outlet 23 faces an underlying tray (not represented), which is normally present in the lower part of the basement 2. For this purpose, to the opening 23, shaped like a union, there may also possibly be connected a small tube, which gives out into the aforesaid tray. The amount of water that can reach the inside of the conduit 15, and hence the aforesaid tray, is as a rule very modest so that said water can evaporate naturally from the tray in a brief period, without any prolonged accumulation in time. In a possible embodiment, in any case, within the aforesaid tray there may be installed sensors means of a type in itself known that, upon detection of a level of water deemed potentially dangerous, issue a warning for the user of the machine 1 and/or interrupt operation of the machine itself.
From Figure 11 it may be noted how, in a particularly advantageous embodiment, provided within the conduit 15 is a baffle element 24. Said baffle element, for example in the form of wall, preferably extends from an intermediate stretch of the ascending portion 15b of the conduit as far as a position corresponding to the lower part of the elbow portion 15c, a little upstream of the inlet of the drain opening 23. Said baffle element 24 basically has the dual function of shielding the inlet of the opening 23, with respect to the flow of forced air that comes from the portion 15a of the conduit 15, and at the same time of defining a duct 24a that, like a funnel, conveys into the draining opening 23 any possible water that descends from the portion 15b towards the elbow portion 15c. In the example illustrated, the conduit 15 is formed by the union of two longitudinally extending pieces, designated by 10a and 10b only in Figure 11, with the baffle element 24 that itself includes two longitudinal halves, each made in a respective piece 10a, 10b.
In the machine 1 the outlet for evacuating damp air from the tub 3 is defined in the upper wall 3b, in the region designated by 25 in Figure 12, where a through hole is provided, not indicated. Connected in fluid communication to said outlet is a condenser device, designated as a whole by 31 for example in Figure 1, forming part of the assembly 30, and defined hereinafter for reasons of simplicity as "condenser".
The condenser 31, illustrated as a whole in Figure 13, basically consists of a hollow body provided with an inlet for the damp air 32, designed for connection with the aforesaid outlet of the tub, and a respective outlet for the dehumidified air 33, that in this case is in fluid communication with the environment external to the tub. As may be appreciated also from Figure 1, the body of the condenser 31 has a first vertical portion 34, which - in the installed condition - extends axially in the direction of the height of the tub 3, generally facing, and set parallel to, a side wall of the latter, in particular the stationary right-hand wall 3d, inside said vertical portion 34 there being defined a condensation path for the damp air leaving the tub 3.
The body of the condenser 31 then includes a second generally horizontal portion, designated by 35, which has dimensions and cross section of passage that are decidedly smaller than the portion 34 and extends substantially perpendicular to the latter. As may be clearly seen in Figure 1, the horizontal portion 35 of the body of the condenser 31 generally faces, and is set parallel to, the upper wall 3a of the tub 3 and is intended to connect the outlet for the damp air from the tub to the upper region of the portion 34.
Hence, as may be noted in Figure 13, the inlet 32 of the condenser 31 is defined in the horizontal portion 35, and in particular in its side facing the upper wall of the tub. For this purpose, the inlet consists of a cylindrical stretch 32a, which is fitted, with interposition of known sealing means, in the aforesaid hole provided in the area 25 of the wall 3a (see Figure 12); fixing in position can be obtained, for example, by means of a shielding member 26, coupled - for instance, by snap action - to the end of the cylindrical stretch 32a that projects within the tub 3.
In the example of embodiment, the outlet 33 for the dehumidified air of the condenser 31 is located in the upper region of the vertical portion 34, as may be clearly seen in Figure 14, in a position generally set alongside the radiusing stretch 34a between the portion 34 itself and the horizontal portion 35, i.e., at the inlet for the damp air into the condensation path. As may be appreciated, the condensation path hence includes a descending stretch, designated by 36 in Figure 13, which extends substantially from the radiusing stretch 34a as far as the lower region of the vertical portion 34, and an ascending stretch 37, which extends substantially from said lower region up to the area in which the outlet 33 is present. For said purpose, defined in the body of the condenser 31 is at least one intermediate longitudinal wall 38a, which extends substantially from the lower region of the portion 34 almost up to its upper end, in the proximity of the outlet 33. As may be appreciated in particular from Figure 13, moreover, in an area corresponding to the descending stretch 36 of the condensation path, the body of the condenser 31 is substantially labyrinthine; for said purpose, transverse walls 38b are provided, with a substantially interdigitated arrangement, some of which depart from the longitudinal wall 38a.
In the embodiment represented, the walls 38a and 38b are made of a single piece in the body of the condenser, substantially in the form of grooves projecting towards the inside of the body itself (as is clearly visible in particular in Figures 14 and 15). A hollow body of the above sort, of a generally flattened configuration and made of a single piece, can, for example, be advantageously obtained by means of blow-moulding of thermoplastic material.
Preferably, at the lower end of the vertical portion 34 of the body of the condenser 31, defined in a position substantially close to the end of the descending stretch 36 of the condensation path, is a receptacle for collection of the water resulting from condensation of the damp air. The aforesaid receptacle, formed by a corresponding lower portion of the body of the condenser 31, is designated by 39 in the figures and has a respective drain union or outlet, designated by 40 in Figure 15. Preferably, connected to said outlet 40 is a small tube, designated by 41 in Figures 6, 7 and 9, which gives out into the collection tray previously mentioned in relation to the drain outlet 23 of the conduit 15. Also the amount of water discharged by the condenser 31 is as a rule modest and can evaporate naturally from the tray in a short period.
Once again in Figure 15 it should be noted how in the portion itself of the body of the condenser 31 that defines the receptacle 39 there can be advantageously provided lateral flanges 42, which can be used for fixing the lower part of the condenser itself to the basement 2, for example with the aid of screws, not represented.
The machine 1 is of course provided with a control system of its own with corresponding user interface, of a substantially known conception, which enables selection, start-up, and control of a plurality of washing programs.
At least one of said programs is configured for carrying out a step of drying of the dishes. Consequently, after the step of discharge of the water used in the course of the last step of the program that envisages the use of water (typically the last rinsing step), the control system issues a command for start of the fan 11 and supply of the heating means 17. The air taken in via the mouth 12a of the fan 11 is then forced into the conduit 15, at the inlet of which it is heated. Preferably, the control system includes sensor means for detecting the temperature of the air (for example, set downstream of the heating means 17) and/or for detecting the rate of humidity of the air (for example, within the condenser 31), for control of the process, according to modalities in themselves known. In the case of a device for heating the air based upon the use of PTC resistors, means for sensing the temperature of the air are not strictly necessary, thanks to the characteristics of self-regulation in temperature proper to this type of resistors.
In a particularly advantageous embodiment, the temperature of the drying air is detected in an indirect way by the control system, exploiting the temperature sensor used for detecting the temperature of the washing or rinsing water. For this purpose, the aforesaid sensor - not illustrated in the figures - can be installed in the proximity of the chimney 21, for example facing the outlet 22b of its lid 22.
At outlet from the conduit 15 the hot air passes into the chimney 21 and, through the lid 22, propagates into the tub 3 from beneath, impinging upon the dishes contained in the racks inside the tub (not represented). Pre-heating of the air obviously favours and speeds up the process of drying of the dishes. The hot air tends to rise from beneath upwards, thus favouring also off-flow of the damp air towards the upper outlet, said damp air tending in any case already in itself to move in a natural way into the upper part of the tub 3. The damp air then penetrates into the horizontal portion 35 of the condenser 31, and then reaches the vertical portion 34. The air then traverses the descending stretch 36 of the condensation path, yielding humidity and then rises along the ascending stretch 37 and comes out substantially dehumidified into the external environment, via the opening 33. The condensation water is collected in the receptacle 39, from which it is evacuated via the tube 41.
The drying process can terminate after a pre-set program time, or else can take place following upon detections made by the aforesaid sensor means, according to a technique in itself known (for example, detecting a rate of humidity of the air not higher than a pre-set threshold).
In the course of the steps of washing envisaged by a program of operation of the machine 1, the presence of the chimney 21 with the corresponding lid 22 prevents the passage of water towards the inside of the conduit 15. Also in the case where the water occasionally manages to penetrate into the conduit 15, however, this water can at the most reach the elbow portion 15c, from where it can be evacuated via the draining outlet 23, and hence without any possibility of reaching electrically supplied parts of the drying system.
The machine 1 according to the invention can be of the stand-alone type, in which case it will be provided with a cabinet that encloses the tub, with the condenser assembly 30 that can easily be housed even in the tiny gap normally existing between the external cabinet and the side and upper walls of the tub of a dishwasher. Obviously, the machine 1 may also be of the built-in type, and hence without a cabinet that encloses the tub completely.
It is clear that numerous variations may be made to the dishwashing machine described by way of example by the person skilled in the art, without thereby departing from the scope of the invention as defined in the annexed claims.
As already mentioned, it is possible to provide and install the casing 12 of the fan 11 in such a way that the intake mouth 12a faces the outside of the basement 2, and hence is in a position generally underlying the condenser assembly 30 (see by way of reference, for example, Figures 1 and 3). As already explained, in this case, the fan 11 takes in air that is present in the proximity of the condenser 31 so as to tend to reduce the temperature thereof and hence favour the condensation process. For said purpose, it is particularly advantageous to provide at least part of the vertical portion 34 of the condenser 31 - and preferably substantially the entire portion 34 - at a slight distance with respect to the side wall 3d (indicatively a distance comprised between 1 and 3 mm), in such a way that the action of intake by the fan will determine also a circulation of air through the gap defined between the aforesaid portion of the condenser and the corresponding side wall: the body of the condenser 31 is in this way slightly cooled, thus favouring condensation.
As has been said, on the other hand, the solution of providing at least the vertical portion 34 of the condenser 31 set at a distance from the corresponding stationary wall of the tub is in any case advantageous also in the case exemplified in the figures, with the intake mouth 12a of the fan 11 facing the inside of the basement 2, in order to contain any possible transmission of heat between said wall and the body of the condenser.
As has already been mentioned previously, in a possible embodiment, the drying system of the machine according to the invention can comprise also a further aspirator, operatively associated to the condenser device 31 for facilitating off-flow of the damp air from the tub 3 and contributing to balancing the pressure in the tub.

Claims

A dishwashing machine having a drying system, the machine (1) comprising a basement (2) and a washing tub (3) supported by the basement (2), wherein the basement (2) defines a housing space (2a) for housing operating components of the machine, wherein the tub (3) has a lower wall (3a), an upper wall (3b), and side walls (3c-3e), and wherein the drying system comprises:
- an inlet (20-22) for introducing drying air into the tub (3);

- an outlet (25) for evacuating damp air from the tub (3);

- a condenser device (31), having a hollow body provided with a respective inlet (32), in fluid communication with the outlet for the damp air (25), and a respective outlet (33), in fluid communication with the environment external to the tub (3), the condenser device (31) having a first portion (34) that generally faces a side wall (3d) of the tub (3) and that defines a condensation path (36-37) for the damp air leaving the tub (3);

- a fan (11), comprising a fan casing (12) housed in which is an impeller (13) driven by a corresponding motor (14), the fan casing (12) being mounted in the housing space (2a) of the basement (2) and having an intake mouth (12a) and a delivery branch; and

- means for heating the drying air (17), operatively arranged along a first conduit (15) that connects the delivery branch of the fan casing (12) to the inlet for the drying air (20-22),
characterized in that:
- the inlet for the drying air (20-22) includes a chimney (21) that extends through the lower wall (3a) of the tub (3) and has an upper end (21a) and a lower end (21b), which open on opposite sides of said lower wall (3a), at the upper end (21a) there being associated a chimney cap (22) defining a substantially labyrinth-path and at the lower end (21b) there being coupled an outlet end (16) of the first conduit (15);

- the outlet for the damp air (25) is defined in the upper wall (3b) of the tub (3);

- the condenser device (31) comprises a second portion (35), which generally faces the upper wall (3b) of the tub (3) and extends between the outlet for the damp air (25) and an upper region of the first portion (34) of the condenser device (31).
The dishwashing machine according to Claim 1, wherein said side wall (3d) is a stationary wall of the tub (3).
The dishwashing machine according to Claim 1 or Claim 2, wherein the first conduit (15) is generally V-shaped, i.e. it comprises a generally descending stretch (15a) from the delivery branch of the fan casing (12) towards an elbow stretch (15c) of the first conduit (15) and a generally ascending stretch (15b) from said elbow stretch (15c) towards the inlet for the drying air (20-22).
The dishwashing machine according to any one of the preceding claims, wherein the fan casing (12) is mounted in the housing space (2a) of the basement (2) with at least one of a rotation axis of the impeller (13) and an axis of the intake mouth (12a) oriented in a direction that is generally horizontal or in any case transverse with respect to a height dimension of the basement (2).
The dishwashing machine according to Claim 3, wherein the first conduit (15) extends substantially entirely in the housing space (2a) of the basement (2).
The dishwashing machine according to Claim 3 or Claim 5, wherein the means for heating the air (17) are positioned in a corresponding seat defined substantially in said descending stretch (15a) of the first conduit (15).
The dishwashing machine according to any one of Claims 4 to 6, wherein defined substantially at the elbow stretch (15c) of the first conduit (15) is a drain opening (23).
The dishwashing machine according to Claim 7, wherein within the first conduit (15) is a baffle element (24) is provided, configured for preventing a substantial reflux towards the drain opening (23) of air forced by the fan (11) and for conveying at the same time into the drain opening (23) any possible water that might reach the inside of the first conduit (15) through the inlet for the drying air (20-22).
The dishwashing machine according to any one of the preceding claims, wherein the condenser device (31) has an outlet for dehumidified air (33) that is located in said upper region of the corresponding first portion (34), the condensation path including a descending stretch (36), which extends substantially from the second portion (35) to a lower region of said first portion (34), and an ascending stretch (37), which extends substantially from said lower region to an area of said upper region where the outlet for dehumidified air (33) is located.
The dishwashing machine according to Claim 9, wherein at the lower end of the first portion (34) of the condenser device (31), in a position substantially corresponding to the end of the descending stretch (36) of the condensation path, there is defined a receptacle (39) for collecting condensation water, having a respective drain outlet (40).
The dishwashing machine according to Claim 9 or Claim 10, wherein at said descending stretch (36) of the condensation path, the body of the condenser device (31) is substantially labyrinth-shaped.
The dishwashing machine according to any one of the preceding claims, wherein the hollow body of the condenser device (31) has a generally flattened configuration and is made of a single piece of thermoplastic material, in particular a blow-moulded piece.
The dishwashing machine according to any one of the preceding claims, wherein the first portion (34) of the condenser device (31) is at least in part spaced apart from said side wall (3d) of the tub (3).
The dishwashing machine according to any one of the preceding claims, also comprising a further fan, operatively associated to the condenser device (31) and arranged for facilitating off-flow of the damp air from the tub (3).