GB2308431A - Dish washing machine with condensation drying apparatus - Google Patents

Description

DISH WASHING MACHINE WITH IMPROVED CONDENSATION DRYING APPARATUS The invention relates to a dish washing machine, in particular a domestic machine, provided with an improved apparatus for condensation of the moisture in the air contained in the washing tub.

It is known that in particular domestic dish washing machines commonly use the method of drying the dishes by means of dehumidification of the air saturated with water vapour contained in the washing tub; that dehumidification effect is achieved by passing the moist air in a suitable conduit provided with a blower or fan which provides for circulation of the air, a heat exchanger with a cold body being fitted to the conduit.

Usually the condensed water is re-introduced into the tub under the effect of gravity and following the flow of air while the cold body is usually a heat-conducting surface which is cooled in turn by a flow of air taken from and reintroduced into the ambient atmosphere after having passed over said surface. Those types of dish washing machines are disclosed for example in British Patent No. 2,263,969 which suffer from the double disadvantage of a heat exchanger formed by a single surface over which air passes in counterflow relationship on the two opposite faces and thus with a low level of efficiency, and the fact that the motor which drives the fan is disposed in the upper rear corner of the casing of the dish washing machine, thus occupying a space which reduces the useful volume of the tub.

British Patent No. 2,265,820 is functionally similar to the above-described arrangement; the only difference lies in the different positioning of the openings for intake and expulsion of the ambient cooling air which in that patent are disposed at the back.

British Patent No. 2,262,027 (Toshiba) discloses means for drying by condensation in a dish washing machine, comprising a vertical wall along which is passed a circulation of hot moist air coming from the washing tub, a thin layer of cold water taken from the external water supply system passing over the vertical wall. The temperature difference between the surface of the vertical wall and the flow of hot moist air which is blown into contact with the wall causes condensation of the moisture from the air.

That construction is certainly adequate and also highly efficient for vigorous drying of the air; however it suffers from the serious disadvantage of requiring a significant additional consumption of water from the water mains system with cooling means, and that fact is in frontal conflict with the requirement and the endeavours on the part of the producers of dish washing machines to market products which require less and less water, power and detergent substances and accessories to operate correctly while nonetheless affording satisfactory levels of performance.

Also known is the construction disclosed in patent DE 3938180 (Sanyo Electric Co) which uses a single doubleaction fan which certainly reduces the level of complexity and the cost of the apparatus, while nonetheless being similar in other features to the patents referred to above and which also suffers from the disadvantages thereof, including the fact that the flows of hot moist air and cooling air are in parallel streams and that the fan and the motor are disposed behind the tub, thus reducing the useful volume thereof.

In addition the use of the double-action fan, with the necessity for limited clearance gaps between the blades of the fan and the two separate air flow passages makes it inevitable that moist air escapes to the exterior of the machine, which is something that is to be avoided.

German utility model No. 8026939.2 discloses a type of dish washing machine provided with a system for condensation of the moist air, which likewise causes the air to circulate in a conduit which is external to the tub and in which condensation takes place by virtue of heat exchange with the adjacent side wall of the casing.

This arrangement is also found to suffer from the disadvantages of a weak cooling and thus condensation action which in fact has to be enhanced by activation of a means for heating the air in the conduit, in practice an ordinary electrical resistance which increases the temperature difference of the air between the two ends of the conduit.

However that expedient has an adverse effect on the levels of power consumption and makes the machine more complicated, more expensive and also more delicate in terms of use.

It would thus be desirable, and this is the aim of the present patent, to provide dish washing machines having apparatuses for drying by means of condensation of the moist air, which are functionally effective, simple and require only minimal levels of additional power consumption.

According to the present invention there is provided a dish washing machine, provided with an external casing, a washing tub, and an apparatus for drying by condensation of the moist air contained in said tub, said apparatus comprising: a first conduit which is external to said tub and which is provided at its two ends with two apertures with which it is connected to the interior of said tub, of which a first aperture opens at the upper portion thereof and the second aperture opens in the associated lower portion, and comprising in its interior a first fan capable of drawing air from the upper aperture and discharging it from the lower aperture; a second conduit which is independent of the first and capable of drawing in a flow of air taken from the ambient atmosphere by way of a suitable intake and discharging it to the ambient atmosphere by means of a suitable discharge opening, said flow being activated by a suitable second fan disposed at an intermediate position of said second conduit; and heat exchanger means between said first conduit and said second conduit, the heat exchanger means being designed in such a way that the flow of said first conduit and the flow of said second conduit are disposed in mutually transverse directions when they pass within said means.

The invention will be better appreciated from the following description given solely by way of non-limiting example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side view showing the principle of a condensation apparatus according to the invention; Figures 2 and 3 separately show two sub-assemblies of the invention which are subsequently assembled; Figure 4 is a partly cut-away perspective view of the apparatus according to the invention; and Figures 5 and 6 respectively show views in horizontal and vertical section of the apparatus shown in Figure 4.

Hereinafter in this description the term "a ir" will be used synonymously with the term "hot moist air" but the use of one term or the other will not compromise the clarity of the description having regard to the context in which those expressions are used, as will be immediately apparent to the man skilled in the art.

The invention essentially consists of a first vertical conduit 1 and a second conduit 2 which is substantially transverse thereto. The first conduit 1 is connected to the interior of the tub by means of two openings, an upper opening 3 and a lower opening 4 respectively, which are disposed at the corresponding terminal portions of the first conduit.

Arranged in the vicinity of the lower opening 4 is a first fan 5 which is motor driven, as will be better explained hereinafter, and which is capable of drawing air through the upper opening 3.

The second conduit 2 is open at its ends with respective intake and discharge apertures 55 and 6 respectively which both open to the ambient atmosphere; in addition it is provided, in the vicinity of the intake aperture 55, with a second fan 7 which is also motor-driven and which is capable of circulating in said second conduit air which is taken from the exterior.

The first and second conduits intersect in a heat exchanger 8 which is designed substantially in such a way as to have a plurality of first parallel passages 9 fitted into the first conduit in such a fashion that the entire flow of air of the first conduit is completely subdivided among the first passages; they are spaced by mutual gaps 10 in which are accommodated second parallel passages 11 which are fitted in the second conduit in such a way that the entire flow of air in the second conduit is subdivided among the second passages.

The heat exchanger is designed in such a way that the first passages 9 and the second passages 11 are arranged in directions which are transverse relative to each other.

The condensate produced from the moist air which passes through the first passages moves downwardly through the final portion 20 of the first conduit downstream of the heat exchanger and falls under the effect of gravity back into the tub again by way of the same lower opening 4 which is naturally disposed at a position below the position of the heat exchanger.

The advantages of that configuration, that is to say in regard to subdivision of the lows of air, is that this enormously increases the heat exchange surface area without appreciably increasing the volume or the dimensions of the heat exchanger, which is something that, together with the fact that the flows are transverse, markedly enhances the efficiency of the heat exchanger, as demonstrated in numerous laboratory tests. Naturally a simplified version of that type of heat exchanger is formed by a single pair of passages, one for the cooling air and one for the moist air to be dried, but that construction, as can be easily realised, affords a lower level of efficiency in terms of heat exchange.

Even if the passages may be of sections of different and not particularly elongate shapes, a preferred configuration is illustrated in the drawings, in particular in Figures 2 and 3, where it will be seen that the first parallel passages 9 are of a heavily elongate rectangular section and are of similar dimensions and disposed in sideby-side relationship but mutually separated by the respective gaps 10, similarly to the second parallel passages 11 which are disposed within said gaps which separate the first parallel passages. That configuration increases the mutually facing surface areas and thus enhances the heat exchange effect.

The invention affords the opportunity for some improvements: the first provides that the walls 13 and 14 respectively of the first and second parallel passages, which are illustrated in Figures 2 and 3 for the sole purpose of graphically describing such passages taken separately and not in the context of the final structure of the heat exchanger, are structurally combined in such a way that a pair of adjacent walls is provided by a single physical wall capable of defining both the passages on the two opposite faces thereof, as shown in Figure 4. That makes it possible to simplify and economise on production of the heat exchanger and at the same time to enhance heat exchange between adjacent passages.

A further improvement which is useful for occupying the minimum amount of space provides that the fans are motordriven by a single motor to which suitable coupling means are coupled, and the motor is directly fixed on the shaft of the second fan 7 which is disposed below the tub, and which transmits the motion to the first fan 5 by means of a suitable belt 16 interposed between two suitable pulleys mounted on the respective fans.

The motor is also disposed in such a way as not to be affected by the flow of cold air which is drawn in from the exterior, since in the opposite case the heat which is given off during operation would heat up the cooling air, thereby significantly reducing the capacity thereof for condensation of the hot moist air.

To promote the passage of the cooling air into the second conduit, the respective two apertures 55 and 6 are disposed in two opposite directions, preferably one disposed at the front 17 and the other at the back 18.

Although the invention has been described by reference to the example of the preferred embodiment and with known terminology, it is not to be considered limited thereby since the man skilled in the art may make numerous variations therein.

Claims (9)

1. CLAIMS 1. A dish washing machine, provided with an external casing, a washing tub, and an apparatus for drying by condensation of the moist air contained in said tub, said apparatus comprising: a first conduit which is external to said tub and which is provided at its two ends with two apertures with which it is connected to the interior of said tub, of which a first aperture opens at the upper portion thereof and the second aperture opens in the associated lower portion, and comprising in its interior a first fan capable of drawing air from the upper aperture and discharging it from the lower aperture; a second conduit which is independent of the first and capable of drawing in a flow of air taken from the ambient atmosphere by way of a suitable intake and discharging it to the ambient atmosphere by means of a suitable discharge opening, said flow being activated by a suitable second fan disposed at an intermediate position of said second conduit; and heat exchanger means between said first conduit and said second conduit, the heat exchanger means being designed in such a way that the flow of said first conduit and the flow of said second conduit are disposed in mutually transverse directions when they pass within said means.
2. 2. A machine according to claim 1, wherein said heat exchanger means are disposed in the gap between said tub and a side wall of the external casing.
3. 3. A machine according to claim 1 or claim 2, wherein said heat exchanger means comprise first parallel passages of greatly elongate rectangular section and of similar dimensions and disposed in side-by-side relationship but mutually separated by respective gaps, and second parallel passages of greatly elongate rectangular section and of similar dimensions, which second passages are disposed in said gaps which separate said first passages.
4. 4. A machine according to claim 3 wherein the walls which define and separate said first passages from said second passages are single walls which are common to each pair of adjacent passages.
5. 5. A machine according to claim 4 wherein said fans are motor-driven by a single motor which transmits the rotational movement of its rotary shaft to the rotary shafts of the respective fans by way of suitable coupling means, and that said motor is disposed substantially below said tub.
6. 6. A machine according to claim 5 wherein said motor is directly fixed on the shaft of said second fan which transmits the motion to said first fan by way of a suitable belt interposed between two pulleys mounted on said respective fans.
7. 7. A machine according to any one of the preceding claims wherein said motor is protected from the flow of air of said second fan so that said flow of air is not heated by the heat issuing from said motor.
8. 8. A machine according to any one of the preceding claims wherein said intake and discharge apertures of said second conduit are disposed respectively on the front side and the back of said machine.
9. 9. A machine constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings