Heating apparatus for combined clothes washing and drying machine.

0001The present invention relates to a heating apparatus for a combined laundering machine for washing and drying clothes, which is apt to both improve the efficiency of the machine during the clothes drying process and enhance the construction and the assemblability of the machine itself.

0002In particular, the present invention relates to a front-loading domestic washing machine, which is equipped with a wash tub within which a clothes drum is able to rotate about a horizontal axis and to accomodate the washload during both the washing and the drying process.

0003Combined washing and drying machines are known, which wash the clothes either by soaking them into the wash liquor or by spraying them with a reduced amount of wash liquor being properly cir­culated in the wash tub, and them dry the washload by a hot-air process.

0004Said drying process can be implemented either by means of a closed-loop air circulation system, where the air is forced to successively flow through a heating apparatus, the drum containing the clothes, a dehumidifying apparatus, and is finally returned to the circuit where the cycle starts again, or by means of an open-loop system which ta­kes in the air from the room, heats it up, sends it through the clothes and finally blows it outside the machine under moist and hot conditions.

0005In view of obtaining a higher effi­ciency of the machine during the drying operation, the heating elements provided to heat up the drying air are preferably placed into a box-like housing which is fixed by welding in the area where the air intake opening lies in the upper part of the wash tub.

0006The main disadvantage arising in con­nection with this solution, however, lies in the problems which are encountered in getting at the heating elements for maintenance and repair pur­poses, since access to them can be only gained by first taking the tub-drum assembly apart.

0007A further disadvantage lies in the corrosion initiation effects induced by the welding operation performed to attach the heating-element housing onto the wash tub.

0008Furthermore, heating elements are usually employed in this type of machines to heat up the drying air, which are designed to operate at as high temperatures as 600°C in order to ensure a favourable heat-exchange interaction with the drying air and, as such, shall necessarily be sheathed with special-alloy materials having high nickel-chromium contents for increased corrosion strength.

0009Such heating elements require manufac­turing processes which are quite complex and imply high defect rates.

0010A metal screen is furthermore arranged above the body of said heating elements in view of both increasing the heat-exchange surface area and minimizing heat radiation losses towards the outside of the appliance, while at the same time reducing the temperature values which the electrical and other functional parts housed in the upper part of the machine may become exposed to.

0011As a consequence, heating elements of this type are both intensively power-consuming and expensive, and they also require the use of thermal screening arrangements which not only contribute to the construction complexity of the machine, but can also give rise to disturbing noise and vibration problems during certain operation cycles (eg., spin extraction) of the machine.

0012Under these circumstances it would therefore be desirable, and is in fact the main object of the present invention, to provide a heating apparatus for a combined clothes washing and drying machine capable of eliminating all above described disadvantages, while ensuring the same or possibly a better efficiency of the machine during the clothes drying process.

0013These and other objects are attained according to the present invention by a heating apparatus for a combined clothes washing and drying machine, particularly a front-loading washer-dryer machine for home use comprising a wash tub within which a drum is rotatable about a horizontal axis and is capable of accomodating the clothes to be both washed and dried, a drying pneumatic circuit equipped with a blower forcing the drying air to successively flow through a housing containing heat­ing elements and communicating with an opening in the upper part of the wash tub, and the drum con­taining the clothes, to finally expel it out of the tub of the machine, characterized in that the hous­ing of the heating apparatus is joined in a remo­vable way with the opening in the upper part of the wash tub and forms a part of the wall of said wash tub, said heating apparatus being formed by one or more electrical resistance heating elements embedded in a mass of heat-radiating material and being further provided with means capable of conveying the drying air toward the drum containing the clothes.

0014The characteristics and advantages of the invention will become more clearly apparent from the following description, given by way of non-­limiting example with reference to the accompanying drawings, wherein: <ul id="ul0001" list-style="none"><li>Figure 1 is a partial cut-away, side view of a clothes washing and drying machine equipped with a preferred embodiment of the appa­ratus according to the invention;</li><li>Figures 2 and 3 respectively show a longitudinal cut-away view along the II-II line of Fig. 3 and a partial top view of the apparatus according to Fig. 2.</li></ul>

0015The clothes washing and drying machine 4 shown in Fig. 1 is essentially formed by a wash tub 5 in which a drum 6 is mounted in such a way as to be capable of rotating about a horizontal axis and accomodating the clothes to be washed and dried.

0016The drum 6 is driven rotationally by an electric motor and belt-type driving means in a per se known, not shown way, and it features a front loading opening 7 which is in a line with both the front opening 8 in the wash tub and the front open­ing in the outer cabinet (not shown) of the washing and drying machine.

0017The wash tub 5 has a lower opening 9 connected via a conduit 10 with a filtering device, a pump and a drain conduit (not shown) which are provided to duly discharge the wash liquor or the water from the machine at the end of the various washing and rinsing cycles.

0018After completion of a washing process, the machine 4 can in a per se know way perform also the drying of the washed clothes by means of a heated-up air flow which is circulated through the drum 6 containing the wet drying load, and which is then expelled from the tub 5, dehumidified, heated up and blown again into the tub 5.

0019To this purpose, a blower 11 is pro­vided, the suction side of which is connected with the drain conduit 10 of the wash tub 5 through a water-cooled condensing device 12, while the deli­very side of said blower 11 is connected with an opening 13 in the upper part of the wash tub 5 through a housing 14 containing a heating apparatus 15 formed by electrical resistance heating elements.

0020The condensing device 12 is connected to the water mains through a conduit 16 and a water inlet solenoid value (not shown) which deliver to a spray nozzle 17 the water needed to form the cooling curtain for condensing the moisture out of the air expelled from the tub 5.

0021Both cooling water and condensate are then conveyed to the discharge pump and, from there, to the drain.

0022The machine equipped with the heating apparatus according to the invention is capable, in a per se known way, of either traditionally washing the clothes by soaking them in the wash liquor or washing the clothes by spraying a reduced quantity of continuously circulated wash liquor on them.

0023To this purpose, the filtering appa­ratus (not shown) of the machine is connected, via a collecting manifold and a circulation pump (not shown), with a conduit 18 which penetrates into the top part of the tub 5, just above the heating appa­ratus 15, so that it can spray heated-up wash liquor onto the clothes contained in the drum 6.

0024The housing 14 of the heating apparatus 15 is in a preferred way made of stainless steel and is attached in a removable way to the opening 13 in the upper part of the wash tub 5 with the interpo­sition of suitable sealing means 19 (eg., rubber sealing gaskets) therebetween.

0025The connection of the housing 14 of the heating apparatus 15 with the wash tub 5 is made through the use of tie-rods 20 connected to the ends of a circular strap (not shown) which is capable of being applied in a removable way against the circum­ference of the wash tub 5 as described in European Patent Application No. 0 214 510.

0026Instead of or together with said tie-rods, traditional screw-and-nut fastening means can also be used.

0027The heating apparatus 15 (Fig. 2) is fixed in a removable way to the housing 14, eg. by screw-and-nut or similar fastening means 21, and includes one or more electrical resistance heating elements 22 made of conventional stainless steel material and embedded in a plate 23 of heat-radiat­ing material.

0028Said heat-radiating plate 23 has a rectangular shape extending transversally so as to cover almost the whole surface of the opening 13 in the wash tub 5, except for a narrow passage gap 24 all along the perimeter (Fig. 1).

0029The plate 23 is further provided with a number of through holes 25 (Fig. 3) which are so designed as to enable both the drying air and the wash liquor issuing from the circulation conduit 18 during spray washing of the clothes to freely flow through them.

0030The upper surface of the plate 23 is provided with fins 26 (Fig. 3) which feature a diverging pattern along the direction in which the drying air flows into the tub 5, in view of enabling the drying air to be distributed over the largest possible surface area of the plate 23.

0031The plate 23 may for example be formed by a cast slab of aluminium in all those cases in which the heating elements 22 are required to ope­rate at medium-to-low temperature values which would therefore exclude the occurrence of problems arising from the difference in the thermal expansion coeffi­cients of the stainless steel, of which the heating elements 22 are made, and the aliminium forming the plate 23.

0032Should on the contrary heating elements for higher operating temperatures be required, the plate 23 may advantageously be made of a ceramic material enabling also normal heating elements, ie. not specially sheathed, to be embedded therein.

0033It is to be noticed that the heating apparatus as described herein is connected in a removable way with the wash tub 5, thereby elimi­nating all disadvantages deriving from a welded attachment and simplifying maintenance of the housing 14 as well as the possible replacement of the heating apparatus 15.

0034Furthermore, the heating apparatus 15 is such as to make it unnecessary to use expensive heating elements sheathed with high-grade steel claddings, since the heat-radiating plate 23 enables the actually available heat-exchange surface, and as a consequence the efficiency of normal heating elements, to be increased and, at the same time, the heating elements themselves to be effectively protected against corrosion.

0035As a consequence, the heating apparatus 15 may be made to operate at lower temperatures and makes it unnecessary to provide for the arrangement of such heat shielding means as usually required by traditional solutions.

0036In the above-described embodiment, the heating apparatus is used in a closed-loop condens­ing-type combined clothes washing and drying ma­chine. However, it is quite apparent that the same advantages would also derive from its use in washing and drying machines provided with an open-loop drying circuit.

0037The heating apparatus according to the present invention can of course be further modified or differently made as compared to the described embodiment without departing from the scope of the invention.

0038For example, the heating plate 23 could also be given different shapes (eg. oval or arched) or be made of materials other than those previously mentioned (eg., special ceramics).