Dishwasher with improved drying system

Abstract

A dishwasher provided with a drying system includes a plurality of inlets (2) located at different heights along a water supply duct (3) to feed washing liquid and also air for drying in the final drying phase into the wash tank, such air arriving from an air supply duct (5) connected to the water supply duct (3) by two connections (6) each of which is equipped with a unidirectional flap valve (7) in which a flap (7a) is hinged at the top and rests by gravity on a seat (7b), and the air supply duct (5) is equipped at its lower end with a drain (8) connected to the wash tank.

Description

[0001] The present invention relates to dishwashing machines, and in particular to a dishwasher with an improved drying system. Note that although specific reference is made in the following to a dishwasher, which can be either domestic or industrial, the invention also applies to similar machines, such as machines for washing and thermodisinfecting medical items.

[0002] It is known that an operating cycle of a dishwasher usually includes a final drying phase intended to make the dishes ready for use as soon as they are taken out of the dishwasher, and for this purpose the dishwasher is equipped with a drying system that can be implemented in various more or less sophisticated ways. The most advanced systems include elements outside the wash tank, such as devices for capturing, condensing, or expelling vapor, with possible heating of the air fed back into the tank.

[0003] However, these known drying systems have the drawback of causing an "indirect" drying, in the sense that they act by reducing the relative humidity of the air contained in the tank to allow the subsequent evaporation of the water clinging to the dishes. This implies long drying times and high energy consumption for heating the air fed back into the tank.

[0004] A faster and more effective drying system is to act directly on the dishes by delivering, through the washing sprayers, a stream of air that "spreads out" the water droplets on the dishes, facilitating their evaporation. In addition, this airflow creates convective motions that bring the vapor contained in the air more in contact with the walls of the tank facilitating its condensation, since the walls of the tank have greater heat exchange than the dishes.

[0005] This configuration implies that there is a connection between the washing circuit and the drying circuit, since the same sprayers deliver first the washing water and then the hot air for drying. In order to prevent water from entering the drying circuit during the washing phases, it is therefore essential to have valves along the connections between the two circuits.

[0006] In prior art machines such valves are non-return valves, typically valves with a ball shutter pressed by a spring, or solenoid valves controlled directly by the machine control unit. These types of valves are effective in preventing water leakage to the drying circuit, but they have drawbacks in terms of reliability and cost.

[0007] First, particularly in the case of thermodisinfection machines, the high temperature of rinse water can adversely affect valve life because the spring of a non-return valve undergoes repeated thermal cycling that can weaken it, and the electrical components of a solenoid valve can also be affected by such temperature. Second, a solenoid valve that must be connected to the control unit implies a higher cost and higher machine construction complexity than a simple mechanical valve.

[0008] In addition, the spring of a non-return valve must be strong enough to adequately press the ball on its seat to prevent leakage, therefore opening such a valve will also require a high pressure in the drying circuit to overcome the spring thrust. This implies a robust construction of the drying circuit, since even a limited pressure drop could cause the valves to fail to open, and requires an air pump of adequate power to generate the required pressure, resulting in cost and power consumption for such a pump.

[0009] It is therefore the purpose of the present invention to provide a dishwasher that overcomes the above drawbacks. This purpose is achieved by means of a dishwasher provided with valves separating the washing and drying circuits that are simple flap valves, and the drying circuit is provided with a bottom drain into the tank.

[0010] The main advantage of this dishwasher lies in the presence of valves that are cheaper and more reliable, since they are simple mechanical valves without springs given that the flap closes by gravity, and in the presence of the bottom drain that guarantees the absence of water in the drying circuit since any possible leakage of water through the flap valves during the washing phases is returned to the tank through said bottom drain.

[0011] A second advantage of this configuration is to have an additional point of entry of drying air into the tank through the bottom drain, making the distribution of air in the tank more uniform resulting in improved drying in the lower basket.

[0012] A further advantage of the present solution is that it does not require high air pressure to open the valves during the drying phase, resulting in savings in the cost of the air pump and the structure of the drying circuit, lower energy consumption, and greater reliability.

[0013] These and other advantages and features of the dishwasher according to the present invention will be evident to those skilled in the art from the following detailed description of an embodiment thereof with reference to the attached drawings in which: Fig.1 is a front perspective view, with the door open and the baskets removed, of a dishwasher equipped with an improved drying system according to the present invention; Fig.2 is a rear perspective view of the dishwasher of Fig. 1; Figs.3 and 4 are enlarged transparency views of the connections between the washing and drying circuits in the washing and drying phases, respectively; and Fig.5 is a view similar to Fig. 1 showing the entry of the drying air into the wash tank.

[0014] Referring to the above figures, it can be seen that a dishwasher according to the present invention traditionally comprises a wash tank 1 in which three water inlets 2 located at different heights are arranged along a central vertical duct 3 for supplying water. Each inlet 2 is closed by a spring-loaded shutter that opens when pushed by a corresponding inlet of a duct located on a basket, so that water is delivered only through the inlets 2 to which the baskets (not shown) in the wash tank 1 are connected.

[0015] As mentioned earlier, the same inlets 2 are also used to feed air into wash tank 1 for drying in the final phase of the operating cycle. This air comes from a heater 4 that feeds air into an air supply duct 5 connected to the water supply duct 3 via one or more connections 6, two in the example shown, each of which has a valve 7.

[0016] As shown in the enlarged detail of figures 3 and 4, one of the novel features of the present invention is that valves 7 are simple unidirectional flap valves in which a flap 7a is hinged at the top and rests by gravity on a seat 7b. Such a seat 7b is preferably inclined so that its upper end where the flap 7a is hinged is upstream from its lower end when the direction of air flow is considered, preferably forming an angle of about 30° to the vertical. In this way, the weight force acting on flap 7a has a component orthogonal to seat 7b, which improves valve tightness.

[0017] A second innovative element of the drying system lies in the presence of a drain 8 formed at the lower end of duct 5, below connections 6, and connected to the wash tank 1. This drain 8 is free, i.e., it has no plug, and its passage section is sized so that during the drying phase in duct 5 there is sufficient pressure to cause valves 7 to open, overcoming the weight force acting on flaps 7a.

[0018] In the light of the above description, the simple and effective operation of the dishwasher drying system according to the present invention is immediately understandable.

[0019] As shown in Fig.3, when the water fed through duct 3 enters connections 6 it is intercepted by valves 7, since the water pressure itself pushes flaps 7a against seats 7b. However, it is possible for water leakages into duct 5 to occur, but this water falls by gravity to the bottom of duct 5 where it re-enters the wash tank 1 through drain 8.

[0020] In this way, when the drying phase begins (Fig.4) there is no water in the drying circuit and air from heater 4, through duct 5 and connections 6, enters the wash tank 1 both through those among inlets 2 that are operational (e.g., the first two at the top) and through the bottom drain 8, as shown in Fig.5.

[0021] It is clear that the embodiment of the dishwasher according to the invention described and illustrated above is only an example susceptible to many variations. In particular, the exact shape and arrangement of the elements of the drying system could be varied according to specific constructional requirements. For example, connections 6 could be sloped so that the air outlet ends are lower than the air inlet ends, so as to make leakage through valves 7 less likely and to facilitate water outflow when the wash pump is turned off.

[0022] Similarly, duct 5 could also have other outlets in addition to drain 8 to further improve air distribution in the wash tank 1, these additional outlets also being able to be obtained at a higher position than connections 6.

Claims

1. Dishwasher provided with a drying system, comprising a plurality of inlets (2) located at different heights along a water supply duct (3) for introducing into a wash tank (1) washing liquid in a washing phase and also air for drying in a drying phase, said air arriving from an air supply duct (5) connected to said water supply duct (3) by one or more connections (6) each of which is provided with a valve (7), characterized in that each of said one or more valves (7) is a unidirectional flap valve in which a flap (7a) is hinged at the top and rests by gravity on a seat (7b), and in that said air supply duct (5) is provided at its lower end, below said one or more connections (6), with a drain (8) connected to said wash tank (1), said drain (8) being free with a passage section sized so that during said drying phase in the air supply duct (5) there is sufficient pressure to cause the opening of said valves (7).

2. Dishwasher according to claim 1, characterized in that the seat (7b) is inclined so that its upper end where the door flap (7a) is hinged is upstream from its lower end when the direction of air flow is considered, preferably forming an angle of about 30° with respect to the vertical direction.

3. Dishwasher according to claim 1 or 2, characterized in that the connections (6) are sloped so that the air outlet ends are lower than the air inlet ends.

4. Dishwasher according to any of the preceding claims, characterized in that the air supply duct (5) has additional outlets connected to the wash tank (1) in addition to the bottom drain (8), said additional outlets also being able to be obtained at a higher position than the connections (6).

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