EP2499290B1

EP2499290B1 - Household laundry dryer

Info

Publication number: EP2499290B1
Application number: EP10787190.7A
Authority: EP
Inventors: Giovanni Bombardieri; Giuseppina Pia Potena; Nicola Colucci; Lucio Amati; Gianbattista Pirola
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2009-11-09
Filing date: 2010-11-05
Publication date: 2014-12-03
Anticipated expiration: 2030-11-05
Also published as: PL2499290T3; EP2499290A1; ITTO20090857A1; WO2011055341A1

Description

Field of the invention

The present invention refers to a household laundry dryer comprising a cabinet having a front wall and a rear wall, a generally cylindrical laundry drum rotatably mounted within the cabinet for rotating according to a substantially horizontal rotation axis, support means for rotatably supporting the drum, motor means for rotating the drum, wherein the drum has a peripheral wall that is substantially cylindrical and extends between a front wall and a rear wall of the drum, the front and rear walls of the drum being substantially flange-shaped and each having at least one hole for passage of drying air, and wherein the rear wall of the drum has a central cavity, substantially coaxial with the rotation axis.

Background of the invention

Laundry dryers typically have a bearing structure or cabinet, through which a laundry drum is mounted, rotatable according to a substantially horizontal axis. The drum is actuated through an electric motor, by means of a drive belt, and it is rotatably supported in the front and rear areas thereof by means of pairs of rollers or wheels. In some solutions, the drum is supported at the front part thereof through an abovementioned pair of rollers and at the rear part by a shaft, coaxial with the rotation axis of the drum and associated to the rear wall thereof.
The laundry dryer has a circuit for conveying a flow of drying air, including a duct along which a fan and an electric resistance operate for heating the air. The fan forces the air into the drum, by means of an delivery branch of the system, after the air itself has been heated by means of the resistance. The hot air traverses the inside of the drum and is saturated with the moisture transferred by the laundry items contained therein, which items are thus progressively dried.
The hot air is generally introduced into the drum through a central region of the rear wall thereof, which is provided with a plurality of holes. This region of the drum faces a region of the rear wall of the cabinet, also provided with one or more holes. The duct which conveys the heated air downstream of the fan usually includes an end component which, together with the abovementioned region of the rear wall of the cabinet, forms a chamber, generally approximately circular shaped, so as to surround a region for spreading the air: the drying air spreads in the abovementioned chamber and then penetrates into the drum, through the holes of the respective rear wall. Seal means, usually made up of a low friction annular gasket, are operatively provided between the abovementioned regions provided with holes of the rear wall of the drum and the cabinet, so as to prevent the dispersion of the flow of hot air within the cabinet,.
The moist air exits from the drum through the front wall thereof, which is provided with a central opening, used - in case of front load machines - even with the aim of loading and unloading the laundry. In case of the machines referred to as of the "condensation" type, the front opening of the drum is in fluid communication with the suction branch of the drying air circuit, upstream of the fan, along which there is a condenser suitable for removing moisture from the air suctioned from the drum, such dehumidified air then being heated again and reintroduced into the drum by means of the delivery branch of the circuit. In the case of the machines referred to as of the "discharge" type, when the door is closed, the air exiting from the front opening of the drum is directed towards the external environment, directly through the door or through a respective discharge duct; as a matter of fact, in these machines the system for conveying the air is prearranged in such a manner that the fan suctions fresh air coming from inside the machine and/or from the installation environment thereof, and forces the air into the drum, after the respective heating, with the moist air exiting from the drum which is directly discharged from the apparatus.
In laundry dryers the drum is conventionally made using metal sheets, usually made of stainless steel. In a type of machine, to which the present invention refers, the drum has a peripheral wall, substantially cylindrical, as well as a front wall and a rear wall which are flange-shaped. In other prior art machines, the drum practically consists of the cylindrical wall alone: with the aim of preventing dispersions of the drying air and the moist air, these machines require gaskets of large diameter at the front and rear ends of the cylindrical wall, such gaskets being more subjected to wear and generating considerable frictions during the rotation of the drum, hence entailing complications in the actuation system.
In some known solutions, the front and rear walls of the drum are configured as separate pieces with respect to the peripheral wall, and rigidly fixed thereto, by welding or clinch. In other solutions, the front and rear walls are instead made integral with the peripheral wall.
In the first case, the front and rear wall are obtained by means of blanking and deforming a respective sheet-metal. The fact that the front wall must be provided with an opening sufficiently large to allow loading and unloading the laundry determines a waste of high amounts of material. On the other hand, the rear wall should only have a series of holes for passage of the drying air, instead of a large opening, with the ensuing extensive use of material.
In the second case, providing the front and rear wall of the drum integral with the peripheral wall requires operations for deforming and stretching a single initial foil of sheet-metal. In this case, also the rear wall of the drum inevitably has a relatively wide central opening, which requires closing, so as to prevent laundry items from slipping thereinto during the rotation of the drum. For such purpose, an additional closing component, provided with a series of holes for passage of air, is usually fixed to the rear wall of the drum. Considering the need of guaranteeing an efficient conveying of the drying air, an additional component, cylindrical-shaped, protruding towards the inside of the cabinet and coupled - with interposition of sealing means - to the opening of the rear wall of the drum, is fixed to the rear wall of the cabinet; in order to guarantee the passage of the drying air, such additional component is provided with one or more openings. This solution has the drawback of requiring the production and the sealed assembly of additional components on the structure of the cabinet of the machine, increasing production times and costs.
Document DE3624372A1 discloses a dryer having a front bottom fixed to the housing for the horizontally mounted laundry drum wherein, in order to prevent the laundry from rolling together, the stationary front bottom is made conical and is closed in the middle by means of a lint filter. It further discloses a channel member which belongs to the supply air duct into which air is blown by a blower, which is fixed to the rear wall of the cabinet and protrudes inside the opening of the rear wall of the drum.

Summary of the invention

Considering the above, the present invention essentially aims at providing a laundry dryer which, though being easier and cheaper to construct, is capable of guaranteeing an efficient operation equivalent to that of the dryers according to the prior art.
Such aim is attained, according to the present invention, by a laundry dryer having the characteristics indicate in the attached claims. Preferred characteristics of the invention are indicated in the sub-claims. The claims form an integral part of the technical disclosure provided herein in relation to the invention.
In summary, according to the invention, a laundry dryer of the type indicated at the beginning of the present description is characterized in that the rear wall of the cabinet has a substantially cylindrical drawing, protruding towards the inside of the cabinet and at least partly received in the central cavity of the rear wall of the drum. In a preferred embodiment, the drawing has a cylindrical wall and a bottom wall, at least one hole for passage of the drying air being formed in the latter.
The abovementioned drawing overcomes the need for application of additional components to the structure of the cabinet, hence advantageously leading to reduction of times, operations and costs required for the production of the machine; the drawing is actually obtainable directly during the steps of blanking and moulding the panel which is used to make the rear wall of the cabinet. Such drawing also allows conveying the flow of the drying air efficiently towards the inside of the basket. An induced advantage is the reduction of consumption of stainless steel required for forming the rear wall of the drum, given that the central cavity may be configured as a through cavity.
In a particularly advantageous embodiment, the peripheral wall of the drum is a metal wall and at least one of the front wall and the rear wall of the drum has a main body made of plastic material, which is fixed at a respective end edge of the peripheral wall.
In this way, at least one end wall of the drum, whether the front, the rear or both, may be obtained in a simple and inexpensive manner, particularly through operations of injection moulding of plastic material, such as thermoplastic material. The solution allows avoiding typical wastes and swarf and simplifying the operations for the production of the drum, using relatively simple machinery. The fact that the front and/or rear walls of the drum are made of plastic also offers the advantage of considerable flexibility in the choice of the shape or profile to be conferred to the walls in question, such profile being optimised according to the interaction thereof with other components of the machine, and not vice versa. For such purpose, for example, it is possible to design the end wall/s of the drum in such a manner to position and configure the surfaces intended to cooperate with the support rollers of the drum, or even the areas intended to cooperate with, or receive, the sealing means intended to prevent the dispersions of the airflows relatively at will. For example, in an embodiment, the body of the front and/or rear wall of the drum is provided with a central opening and it is shaped to have a generally cylindrical central portion, coaxial with the rotation axis of the drum and spaced from the opening, such cylindrical portion defining a supporting surface cooperating with respective support means of the drum.
In a preferred embodiment, the front and rear walls of the drum each have the respective main body made of plastic material. In this way, the saving on the cost of materials, elimination of wastes and swarf and flexibility in the design of the front and rear walls of the drum are increased further.
In a preferred version, the front and rear walls, or the relative plastic main bodies, are identical to each other. This version is advantageous in terms of production standardisation, even when the end walls of the drum are made of metal material.
In a preferred embodiment, the main bodies of the two end walls of the drum each have a central opening, substantially coaxial with the rotation axis of the drum. The opening of the rear wall may be closed - even when the two end walls have different shapes - using an additional component, fixed to the same wall, with interposition of sealing means. This additional element, which may be made of metal material or also of plastic material, is provided with at least one hole for passage of the drying air.
In an embodiment, the plastic main body of the front and/or rear wall of the drum is prearrangement for coupling with the corresponding end edge of the peripheral wall. Preferably, for such purpose, the plastic body of the front and/or rear wall defines a seat for coupling with said end edge of the peripheral wall. In this embodiment, the fact that the wall/s in question is/are made of plastic, offers considerable flexibility in the design of the profile for coupling between the end wall/s of the drum to the cylindrical wall thereof, such profile being freely selected according to the desired type of coupling, for example by means of screws, rivets, snap-couplings, gluing, etcetera. In an embodiment, for example, the abovementioned seat is obtained by means of two cylindrical walls, concentric with respect to each other and coaxial to the rotation axis of the drum, which define - with respect to each other - a space in which the corresponding end edge of the cylindrical wall of the drum is received.
In an embodiment, the support means of the drum include a shaft coaxial with the rotation axis and this shaft is associated to the rear wall. In case of a stationary shaft, when the rear wall has a main body made of plastic material, a seat - in which a member such as a hub or ball bearing or the like for coupling to the shaft is received - may be easily defined by moulding. The plastic body of the wall may also be directly overmoulded on the abovementioned member. In cases where the support shaft rotates with the drum, the plastic wall may be moulded directly on the respective end of the shaft.

Brief description of the drawings

Further characteristics and advantages of the present invention shall be clear from the description that follows, provided with reference to the attached drawings, purely provided by way of non-limiting example, wherein:

figure 1 and 2 are, respectively, a front view and a partial and schematic section of a laundry dryer according to the invention;
figure 3 is a partial and schematic section, in exploded view, of some components of the machine of figure 1 and 2;
figure 4 is a schematic perspective view of a rear wall of the cabinet of the machine of figure 1 and 2;
figure 5 is a partial and schematic view of a machine according to a second embodiment of the invention;
figure 6 is a schematic section of a component of the drum of the machine of figure 5;
figures 7 and 8 are representations similar to those of figures 5 and 6, regarding a third embodiment of the invention; and
figures 9 and 10 are representations similar to those of figures 5 and 6, regarding a fourth embodiment of the invention.

Description of preferred embodiments of the invention

Reference to "an embodiment" in this description indicates that a particular configuration, structure or characteristic described regarding the embodiment is included in at least one embodiment. Hence, expressions such as "in an embodiment" and the like, possibly present in various parts of this description do not necessarily refer to the same embodiment. Furthermore, particular configurations, structures or characteristics may be combined in any suitable manner into one or more embodiments. References numerals herein are used for facilitating the reader and thus they do not define the scope of protection or the scope of the embodiments.
Unless otherwise specified, in the present description and in the attached claims, the terms "front wall" or "rear wall" with reference to the drum, are used to indicate a component obtaining the structure or main body of a respective end wall of the drum, fixed to an end edge of the peripheral wall thereof, and without prejudice to the fact that other components, such as gaskets, sliding pads or a closing member, may be associated to such main structure, as described hereinafter.
It should also be observed that, in the present description and in the attached claims, the terms "plastic material" and the like, are used to indicate any plastic or synthetic material, or based on plastic or synthetic material, possibly added with fillers suitable to improve the functional and robustness characteristics thereof, such as mineral, textile synthetic fillers and so on and so forth.
In addition, it should also be observed that in the present description only the elements useful for the understanding of the invention shall be described in detail, assuming the machine subject of the invention to comprise all the other elements per se known for the normal operation of a laundry dryer, such as for example a control system, a motor for rotating the drum by means of a belt, a condenser for the drying air (should the invention be applied to a condensation machine), and so on and so forth.
In figures 1 and 2, a household laundry dryer according to an embodiment of the present invention is indicated in its entirety with 1; in figure 3 only some components of the machine 1 are illustrated, in exploded view.
The machine 1 has a cabinet or bearing structure, comprising a base 2, a front wall 3, a rear wall 4, an upper panel or "top" 5 and side walls S. Like in the prior art, the front wall 3 is provided with a through opening, indicated with 3a in figure 3, at which a door 6 is mounted.
Within the cabinet a drum or laundry holder 7 is provided, which is generally cylindrical and which is rotatably mounted for rotating according to a substantially horizontal rotation axis, indicated with X only in figure 2. Support means for rotatably supporting the drum 7, which may be of the rolling type, such as wheels, or of the sliding type, such as slides, are provided for in the cabinet.
In the exemplified preferred embodiment, these support means comprise two pairs of rollers, respectively mounted at the front and at the back of the drum 7. In the figures, the rollers of the front pair are indicated with 8, while a single roller of the rear pair is indicated with 9. In the embodiment, these rollers 8 and 9 are rotatably mounted on pins fixed to the front 3 and rear 4 walls of the cabinet, respectively, but such mounting solution shall not obviously be deemed restrictive. In an alternative embodiment, not represented, the rollers 8 and 9 are rotatably mounted on pins supported on the base 2.
The rollers 8 and 9 are intended to cooperate with respective surfaces of the drum 7 as clarified hereinafter. The machine 1 is further provided with motor means for rotating the drum 7. These motor means may be of any known type. In the example represented in figure 2, the motor means include a belt 10 fitted between a cylindrical wall of the drum 7 and an actuation pulley 11, associated to the shaft of an electric motor 12 mounted within the cabinet of the machine 1.
The drum 7 has a peripheral wall 13, generally cylindrical and made of metal material, for example stainless steel. The drum 7 further comprises a front wall 14 and a rear wall 15, between which the peripheral wall 13 extends. The front and rear walls 14 and 15 of the drum 7 are generally flange-shaped and they are each fixed to a respective end edge of the peripheral wall 13; such end edges are indicated only in figure 3 with 13a and 13b. The front wall 14 and rear wall 15 wall each have at least one through hole.
According to a preferred characteristic of the present invention, at least one of the front wall 14 and the rear wall 15 of the drum 7 has a main body made of plastic material, such main body being fixed at the respective end edge 13a or 13b of the peripheral wall 13 of the drum 7.
In the preferred embodiment according to figures 1-3, both walls 14 and 15 have the respective main body made of plastic material. The plastic material used may for example be a thermoplastic material, possibly filled and suitable for injection moulding. A material useable for the purpose may be polypropylene, preferably filled with talc, for example at about 30% (other filling materials may for example be calcium carbonate or glass fibre). Plastic or synthetic-based materials of this type are perfectly suitable for bearing the temperatures typical of the flow of the drying air present in a common laundry dryer.
Still referring to the embodiment according to figures 1-3, the front 14 and rear 15 walls of the drum have the respective main bodies identically shaped with respect to each other. Therefore, in the illustrated example, the walls 14 and 15 are provided with respective central through openings, indicated with 14a and 15a, having a relatively wide diameter, coaxial to the rotation axis of the drum 7. In the example, each opening 14a, 15a is delimited and surrounded by a generally cylindrical wall portion, 14b and 15b respectively, of the respective wall main body. A circular wall portion, 14c and 15c respectively, which develops radially, departs from the base of these cylindrical wall portions 14b, 15b.
The main bodies of the walls 14 and 15 are prearranged for coupling with the corresponding end edge 13a or 13b of the cylindrical wall 13 of the drum 7. For such purpose, in the exemplified embodiment, the main body of the walls 14 and 15 defines a seat for coupling with said end edge 13a or 13b of the peripheral wall 13. In the example, such seat is a blind annular seat, indicated with 14d and 15d respectively, and it is defined in a coupling portion, indicated with 14e and 15e respectively, which is at the perimeter region of the wall portion 14c or 15c. Still with reference to the illustrated example, the abovementioned coupling portion 14e or 15e is substantially made up of two cylindrical portions having different diameter, that are coaxial with respect to each other and with respect to the rotation axis of the drum and they project in the direction perpendicular from the wall portion 14c. As observable, the two abovementioned cylindrical wall portions define - therebetween - the seat 14d or 15d, in which the end edge 13a or 13b of the wall 13 is received. The fixing of the edges 13a and 13b of the cylindrical wall 13 in the abovementioned seats 14d or 15d may be obtained through any method suitable for the purpose, for example using screws, rivets, glue, or possibly a snap-coupling system (in the latter case, the edges 13a and 13b of the peripheral wall 13 and the wall portions 14e and 15e shall be suitably configured for the purpose).
Still in the figures, a component of the circulation system of the drying air of the machine 1 is indicated with 16. As mentioned, the air circulation system maybe of any type known in the field. In the illustrated example, the component 16 has the function of defining, partly alongside the rear wall 4 of the cabinet, a duct for conveying the drying air. Through the component 16 the air is conveyed up to the substantially central region of the rear wall 4 of the cabinet, in which a series of holes for passage of the drying air is preferably provided for.
In the exemplified embodiment, the through opening 15a of the rear wall 15 of the drum 7, or the cylindrical portion 15b, provides a central through cavity, coaxial with the rotation axis of the drum, in which a cylindrical closing element is at least partly received, at fixed position and protruding from the rear wall 4 of the cabinet, towards the inside of the cabinet.
According to the main characteristic of the present invention, the abovementioned cylindrical closing element is directly formed by a drawing of the rear wall 4 of the cabinet, indicated in its entirety with 17. As observable particularly in figure 4, such drawing 17 has preferably a cylindrical wall 17a and a bottom 17b provided with one or more holes 17c for passage of the drying air.
As observable in figure 2, in the assembled condition, the drawing 17 is inserted into the central opening 15a, or the tubular portion 15b of the main body of the wall 15. Furthermore, in the illustrated example, a covering element 18, which in the illustrated example is substantially disc or plate-shaped, provided with one or more holes for passage for the drying air in the drum 7, is mounted at the opening 15a; in an alternative embodiment, not represented, the element 18 may be generally hollow cylindrical, and have a cylindrical wall and a bottom wall, the latter being provided with one or more holes for passage of the drying air. The covering element 18 is fixed to the wall 15 through any known means and it may be made using metal or plastic material.
Seal means operating between the main body of the wall 15, particularly at the portion 15b, and the cylindrical wall 17a of the drawing 17 are indicated with 19. These means 19 provide a sealing aimed at preventing dispersions of the flow of the drying air and they may be made of an annular sealing, fixed to the drawing 17 or in the cylindrical wall portion 15b.
In the figures, further sealing means, cooperating between the rear wall 4 of the cabinet and the wall 15, are indicated with 20. In the example, these sealing means 20 cooperate with the front edge of the cylindrical wall portion 15b, to obtain an additional sealing with respect to that obtained by means of the gasket 19. These sealing means 20, for example in form of annular gasket, may be fixed to the rear wall 4 of the cabinet, or to the end of the cylindrical wall portion 15b of the wall 15 of the drum 7. The sealing means 20 are not strictly necessary and thus they should be considered optional; it should however be observed that, according to possible variants not illustrated, even the sealing means 20 alone could be provided for, used to obtain the sealing aimed at preventing dispersions of the flow of the drying air.
The portions 14b and 15b of the walls 14 and 15 provide cylindrical projections, directed towards the outside of the drum 7, each of which define a supporting and rolling surface, intended to cooperate with the rollers 8 and 9, with the aim of rotatably supporting the drum 7, rotated by means of the belt 10 and the motor 11-12.
Lastly, in figure 6 reference 6a indicates as a whole means for sealing and conveying the air - represented solely schematically - operating between the front wall 3 of the cabinet and the front wall 14 of the drum 7, which are configured for preventing dispersions - towards the inside of the cabinet of the machine - of the moist air coming from the drum 7. In cases where the machine 1 is of the condensation type, the air exiting from the drum 7 is reintroduced through the means 6a into the circuit, where a condenser is operative, as described in the introduction of the present description; on the contrary, in the case of discharge machines, the moist air which exits from the drum 7 is conveyed by the means 6a towards a discharge outlet of the air from the machine 1.
In the normal operation, the motor 12, through the pulley 11 and the belt 10 fitted on the cylindrical wall 13, rotates the drum 7. The drum 7 is rotatably supported by means of the pair of rollers 8 and 9, which cooperate with the rolling surfaces defined by the cylindrical portions 14b and 15b of the walls 14 and 15. The drying air, heated through an electric resistance, not represented, is forced by a fan, also not represented, along the circuit, up to inside the component 16. The air thus rises along the rear wall 4 of the cabinet, into the component 16, up to the top part thereof, in which a region for spreading the airflow is essentially defined. The drying air thus penetrates into the drawing 17 and, through the respective holes 17c, it may penetrate towards the inside of the drum, due to the presence of the holes, not represented, of the covering element 18. The presence of the covering element 18 is deemed preferable, but not essential, in terms of aesthetic features and for preventing the risk that the textile items treated in the machine 1 may partly slip between the internal surface of the cylindrical wall portion 15b and the surface of the drawing 17 turned towards the inside of the drum 7.
The drying air thus impacts the textile items contained in the drum 7, and then exits from the drum itself by means of the central opening 14a of the front wall 14. Obviously, such opening 14a is conveniently dimensioned also to be used for loading and unloading textile items with respect to the drum 7. The moist air which exits - at the front part - from the drum 7 is once again conveyed, through the means 6a of figure 2, into the circuit or towards the outside of the cabinet.
A second embodiment of the invention is schematically represented in figures 5 and 6. In such figures, the same reference numbers of the preceding figures are used for indicating elements technically equivalent to the ones described above.
Also in the embodiment of figures 5 and 6, the front 14 and rear 15 walls of the drum 7 have respective main bodies made of plastic material, but shaped differently with respect to each other. In particular, in this embodiment, the functions of the covering element 18 of the first embodiment are directly integrated in the main body of the rear wall 15. In particular, as evincible, in this embodiment the cylindrical wall portion 15b is provided with a respective closing bottom 15f. The bottom 15f is naturally provided with one or more through holes for passage of the drying air.
Figures 7 and 8, which use the same reference numbers of the preceding figures for indicating elements technically equivalent with those described previously, refer to a third embodiment of the invention. In this embodiment, the drum 7 is supported at the rear part by means of a shaft 21, instead of the pair of rollers 9, said shaft being coaxial with the rotation axis of the drum 7 and passing through in a respective opening of the drawing 17. In the exemplified embodiment, this shaft 21 is fixed and it is supported by an assembly component 22, fixed at the drawing 17, therein. In this embodiment, the cylindrical wall portion 15b of the wall 15 has the corresponding closing bottom 15f and a member receiving in a rotatable manner the respective end of the shaft 21, is mounted in such bottom. This member, indicated with 23, may for example be a ball or roller bearing, or a hub suitable to allow the rotation of the drum 7 with respect to the fixed shaft 21. The seat for the bearing or hub 23 may be easily defined during the moulding of the main body of the rear wall 15, with the bearing or hub being fixed in the respective seat through any per se known method and means. Obviously, the main body of the rear wall 15 may also be directly overmoulded on the bearing or hub 23, according to per se well known technologies. In addition, it shall be observed that, in a possible variant, the shaft 21 may be rotatable with the rear wall 15, the member 22 rotatably supporting the shaft 21 in such case; in this variant, the body of the rear wall 15 may be overmoulded directly with respect to the respective end of the shaft 21, which shall be suitably configured to guarantee a fixed coupling between the two parts.
The previously described embodiments obviously refer solely to some of the numerous embodiment variants provided for by the invention. Previously, reference was made to a drum 7 in which both end walls 14 and 15, 15', 15" are made of plastic material but it shall also be observed that, in the practical embodiment of the invention, even only one of such walls may be made of synthetic material. Obviously, the advantages are maximized when both end walls of the drum 7 are made of plastic material. The preferred production using plastic material considerably simplifies the process of obtaining the front and rear walls or flange of the drum, also using comparatively less materials with respect to the stainless steel used conventionally. Also the plastic material moulding operations, particularly injection moulding, are simplified with respect to those of deforming sheets typical of the prior art. Also swarfs and wastes typical of the prior art solutions are clearly considerably reduced.
The preferred use of the plastic material also allows the big advantage of offering a wide range of choice of the profile to be conferred to the end wall/s of the drum, by means of a simple prearrangement of equipment (and in particular moulds) used for the plastic material moulding operations. A big advantage of this preferred solution lies in that, contrary to the prior art, the shape of the front and/or rear flange of the drum may be optimized depending on the type of positioning, dimensions and construction intended to be conferred to the components meant to cooperate with the flanges, and specifically the support means - whether represented by pairs of rollers or comprising a rotation shaft - and the means for sealing and/or conveying air provided for in the front and/or rear part of the cabinet of the machine. It shall be observed, for example, that in this manner, possible seats for mounting the sealing gaskets may be directly formed in the plastic main body of the front and/or rear walls of the drum, or the surfaces intended to cooperate with such gaskets may be formed - in the manner and shape deemed most suitable - when the latter are at stationary position and mounted on the structure of the machine.
An example of the design flexibility allowed by the preferred use of plastic material to obtain the front wall and/or rear wall of the drum is schematically represented in figures 9 and 10; the same reference numbers of the preceding figures are also used in such figures to indicate elements technically equivalent to those described previously.
In the embodiment of figures 9 and 10 the drum 7 is provided with a front wall 14' whose profile is shaped with the aim of allowing a different positioning and dimensioning of the front support.rollers, one of which is indicated in figure 14 with 8'. As observable, in this embodiment, besides the cylindrical wall portion 14b, delimiting the opening 14a, from the radial wall portion 14c there rises a further cylindrical portion 14f, that is substantially concentric and coaxial with respect to the opening 14a and having a larger diameter with respect thereto. As observable from figure 14, this further portion of the cylindrical wall 14f defines the rolling surface intended to cooperate with the wheels 8', which in this embodiment have a smaller diameter with respect to the previously described embodiments, and positioned lower.
As already highlighted in some of the previous embodiments, the profiles of the two end walls of the drum, even when both are made of plastic material, may be different. For example, with reference to the embodiment of figures 9-10, the cylindrical portion 14b could possibly be omitted, a simple through opening 14a - obtained in the radial wall portion 14c - being provided for in such case. Obviously, means whose function shall be analogous to those indicated with 6a in figure 2, or configured to allow the conveying of the drying air which exits from the front of the drum 7 shall be provided for at the front part of the drum, to prevent dispersions of moist air into the cabinet of the laundry dryer and to prevent that - during the operations of loading and unloading textile items and during the rotation of the drum - portions of such textile items find their way out of the drum and/or slip between the drum and the fixed structure of the machine.
It should also be pointed out that the use of the drawing 17 provided for according to the invention is applicable, though with less advantages with respect to the preferred use of plastic material, even when one or both the end walls of the drum 7 are obtained in a conventional manner, i.e. made up of a metal flanges applied to the peripheral wall 13 of the drum 7, or obtained by means of blanking and deforming a sheet element which also provides the peripheral wall 13. As mentioned previously, even in such kind of application, the two aforementioned walls may be identical to each other.
Naturally, without prejudice to the principle of the invention, the details and embodiments may vary, even significantly, with respect to what has been described and illustrated purely by way of non-limiting example, without departing from the scope of the invention as defined in the attached claims.
In the previously described embodiments reference was made to a front loading laundry dryer, but the invention is clearly susceptible to application even in case of top loading machines, i.e. of the type in which the door of the machine is hinged to the top part of the corresponding cabinet and the cylindrical wall of the basket is in turn provided with a door.

Claims

A household laundry drier comprising a cabinet (2-5, S) having a front wall (3) and a rear wall (4), a generally cylindrical laundry drum (7) rotatably mounted within the cabinet (2-5, S) for rotating about a substantially horizontal rotation axis (X), support means (8, 9; 8', 9; 8, 21) for rotatably supporting the drum (7), driving means (10-12) to cause rotation of the drum (7), wherein the drum (7) has a peripheral wall (13) that is substantially cylindrical and extends between a front wall (14; 14') and a rear wall (15; 15'; 15") of the drum (7), the front wall (14; 14') and the rear wall (15; 15'; 15") of the drum (7) being substantially flange-shaped and each having at least one hole (14a, 15a) for passage of the drying air, and wherein the rear wall (15; 15'; 15") of the drum (7) has a central cavity (15a, 15b) substantially coaxial with the rotation axis (X), characterized in that the rear wall (4) of the cabinet (2-5, S) has a substantially cylindrical drawing (17) protruding towards the inside of the cabinet (2-5, S) and which is at least partly received in the central cavity (15a, 15b) of the rear wall (15; 15'; 15") of the drum (7).
The laundry drier according to claim 1, wherein the drawing (17) has a cylindrical wall (17a) and a bottom wall (17b), in the latter at least one hole (17c) being formed for passage of the drying air.
The laundry drier according to claim 1 or 2, wherein the peripheral wall (13) of the drum (7) is a metal wall and at least one of the front wall (14; 14') and the rear wall (15; 15'; 15") of the drum (7) has a main body formed of a plastic material, that is fixed at a respective end edge (13a, 13b) of the peripheral wall (13).
The laundry drier according to claim 3, wherein the front wall (14; 14') and the rear wall (15; 15'; 15") of the drum (7) each have the respective main body formed of plastic material.
The laundry drier according to any of the preceding claims, wherein the front wall (14) of the drum (7) and the rear wall (15) of the drum (7) have the same form.
The laundry drier according to claim 1 or 2, wherein the central cavity (15a, 15b) comprises a through opening (15a) of the rear wall (15) of the drum (7).
The laundry drier according to claim 6, wherein within the drum (7), at the central cavity (15a, 15b), a covering element (18) is mounted, the covering element (18) being preferably provided with one or more holes for passage of the drying air.
The laundry drier according to claim 1 or 2, wherein the central cavity is a cavity comprising a cylindrical wall (15b) and a bottom (15f), the bottom (15f) being preferably provided with one or more holes for passage of the drying air.
The laundry drier according to claim 3, wherein the main bodies of the front wall (14; 14') and the rear wall (15) of the drum (7) each have a central through opening (14a, 15a), being substantially coaxial with the rotation axis (X).
The laundry drier according to claim 3, wherein the main body of the at least one of the front wall (14; 14') and the rear wall (15; 15'; 15") of the drum (7) is prearranged for coupling with the corresponding end edge (13a, 13b) of the peripheral wall (13) of the drum (7).
The laundry drier according to claim 10, wherein the main body of at least one of the front wall (14; 14') and rear wall (15; 15'; 15") of the drum (7) defines a respective seat (14d) for coupling with the said end edge (13a, 13b) of the peripheral wall (13).
The laundry drier according to claim 1, wherein the support means (8, 21) include a shaft (21) coaxial with the rotation axis (X) and the shaft (21) has an end operatively coupled to the main body of the rear wall (15") of the drum (7), directly or through an additional member (23).
The laundry drier according to claim 1, wherein at least one of the front wall (14; 14') and the rear wall (15; 15'; 15") of the drum (7) has a generally cylindrical projection (14b; 14f; 15b), directed towards the outside of the drum (7), defining a supporting surface cooperating with respective support means (8, 9) of the drum (7).
The laundry drier according to claim 1 or 3, wherein the main body of the rear wall (15) of the drum (7) is formed of plastic material and includes a single through opening (15a) substantially coaxial with the rotation axis (X).
The laundry drier according to claim 14, wherein the single opening (15a) of the rear wall (15) of the drum (7) is provided, at the end thereof turned to the inside of the drum, of a closing member (18) having a plurality of through holes.