The present invention concerns the field of laundry washing techniques.

Specifically, the invention relates to a washing drum adapted to be rotatably mounted in a laundry washing machine.

Nowadays the use of laundry washing machines, both "simple" laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.

In the present description, the term "laundry washing machine" will refer to both a simple laundry washing machine and a laundry washing-drying machine. Laundry washing machines generally comprise an external casing, or cabinet, provided with a washing tub which contains a washing drum where the laundry is placed. A loading/unloading door ensures access to the washing drum.

Washing drums of known type typically comprise a substantially cylindrical wall closed at one end by a substantially flat rear wall and presenting, on its other end, an opening closed by said loading/unloading door.

Cylindrical wall is typically provided with perforations/holes which allow the liquid flowing therethrough.

Said holes are typically and preferably homogeneously distributed on the wall of the drum. Furthermore, the cylindrical wall is also typically provided with bulges.

According to the known art, bulges and holes are arranged to increase the performance of the washing process.

During the washing process, particularly when the washing drum is rotated, the laundry hits and/or is stuck against the inner surface of the drum wall and water contained in the laundry is ejected outwardly through the holes by means of the centrifugal force for centrifugally dehydrating the laundry.

Shape of bulges may affect treatment of the laundry due to interaction with laundry.

EP1028189A2 discloses a drum for a washing machine, with a drum shell in which elevations on the inside of the drum shell are advantageously arranged in rows next to one another on the circumference of the drum shell, the elevations pointing towards the axis of rotation of the drum and alternating with depressions, so that so passage openings realized between elevations and depressions are linearly arranged aligned along the rotational axis of the drum.

DE102012204560 A1 discloses a drum for a washing machine, which drum shell has a structural pattern based at least in sections on a Penrose tiling to achieve an effective suppression of vibrations of the drum, thereby reducing deformation of the laundry drum compared to drums having a regular structuring and embossing. EP1925704 A1 discloses a drum adapted to be rotatably mounted in a tub of a washing machine or washer dryer, with a cylindrical wall provided with perforations and with a plurality of bulges oriented towards the exterior of the drum and shaped as frustum of pyramid, wherein the perforations of the drum are centered within the bulges.

WO2013030394A discloses a drum that is suitable for using in laundry washing or laundry washing-drying machines and that comprises a cylindrical body, at least one hole located on the cylindrical body and at least one bulge which is located on the cylindrical body and extends from the surface of the cylindrical body towards the rotational axis of the drum, and the contour of which is shaped as a polygon.

It is an object of the present invention to optimize the shape of the washing drum wall in order to increase dehydration performance of the laundry.

It is another object of the invention to optimize the shape of the washing drum wall in order to obtain a gentle treatment of the laundry.

Applicant has found that by providing a laundry washing machine comprising a washing tub external to a washing drum wherein the washing drum comprises a plurality of bulges and by providing said bulges with a squircle-shaped contour, it is possible to reach the mentioned objects.

In a first aspect thereof the present invention relates, therefore, to a washing drum which is adapted to be rotatably mounted in a laundry washing machine wherein laundry to be washed may be placed, said washing drum comprising a tubular body wall apt to rotate around a rotational axis and said tubular body wall comprising at least one bulge protruding from said tubular body wall towards said rotational axis and at least one hole, wherein the contour of said at least one bulge at said tubular body wall has the shape of a squircle, wherein the reference axis of said squircle-shaped contour is inclined with respect to said rotational axis.

The squircle is preferably composed by four rounded corners joined by four slightly rounded sides.

Preferably, the reference axis divides symmetrically two opposed slightly rounded sides.

In a preferred embodiment of the invention, the reference axis of the squircle-shaped contour is inclined with respect to the rotational axis to form an angle between 22,5° and 67,5° preferably an angle equal to 45°.

Preferably, said at least one bulge comprises side walls extending from said contour and terminating at a bottom wall.

According to a preferred embodiment of the invention, the washing drum comprises a plurality of bulges placed side by side, two adjacent bulges defining a channel therebetween.

In a preferred embodiment of the invention, said at least one hole is realized in said channel.

In a further preferred embodiment of the invention, said at least one hole is realized in said side walls and/or said bottom wall.

Preferably, the washing drum comprises a plurality of holes.

In a preferred embodiment of the invention, the holes are realized in the channel. In a further preferred embodiment of the invention, the holes are realized in the side walls and/or the bottom wall.

According to a preferred embodiment of the invention, the side walls and/or the bottom wall are rounded shaped.

In a preferred embodiment of the invention, the washing drum comprises a plurality of bulges, said plurality of bulges being arranged in a row along a main axis.

In a further preferred embodiment of the invention, the washing drum comprises one or more groups of bulges, said one or more groups comprising one or more rows of bulges aligned along a main axis.

Preferably, two of said groups are separated by a smooth area.

Preferably, the smooth area may be considered as a channel having a width preferably equal or larger than the width of a row of bulges.

According to a preferred embodiment of the invention, the main axis is parallel to the rotational axis.

According to a further preferred embodiment of the invention, the main axis is inclined with respect to the rotational axis.

In a preferred embodiment of the invention, the height of the side walls is constant.

In a further preferred embodiment of the invention, the height of the side walls varies. Preferably, the height of said side walls decreases continuously.

In a preferred embodiment of the invention, the bottom wall is parallel to the tubular body wall.

In a further preferred embodiment of the invention, the bottom wall is not parallel to the tubular body wall.

Preferably, the bottom wall is inclined with respect to the tubular body wall.

In a further aspect thereof, the present invention concerns a laundry washing machine comprising a washing tub external to a washing drum, wherein the washing drum is realized as described above.

Further characteristics and advantages of the present invention will be highlighted in greater detail in the following detailed description of some of its preferred embodiments, provided with reference to the enclosed drawings. In the drawings, corresponding characteristics and/or components are identified by the same reference numbers. In particular:

• Figure 1 shows a perspective view of a washing drum according to the invention adapted to be used in a washing laundry machine;
• Figure 2 shows an element of the washing drum of Figure 1 isolated from the rest;
• Figure 3 is an enlarged view of a detail of the washing drum shown in figure 1;
• Figure 4 shows a geometrical shape used for realization of the washing drum according to the invention;
• Figure 5 shows a plan view of a detail of figure 3;
• Figure 6 is a cross section along line VI°-VI° of figure 2;
• Figure 7 is a cross section along line VII°-VII° of figure 2;
• Figure 8 is a cross section along line VIII°-VIII° of figure 5;
• Figure 8A is a further preferred embodiment of figure 8;
• Figure 9 shows a plan view of the drum portion shown in Figure 3, from the front point of view V indicated in Figure 3, according to a second preferred embodiment of the invention;
• Figures 10 and 11 show the washing drum of Figure 2 according to further preferred embodiments of the invention.

The present invention has proved to be particularly advantageous when applied to laundry washing machines, as described below. It should in any case be underlined that the present invention is not limited to laundry washing machines. On the contrary, the present invention can be conveniently applied to laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry).

With reference to Figure 1 a preferred embodiment of a washing drum 1 according to the invention which is adapted to be rotatably mounted in a laundry washing machine is shown.

The washing drum 1 preferably comprises a tubular body wall 10 apt to rotate around a rotational axis R, as better visible in Figure 2. The tubular body wall 10 is preferably cylindrically shaped. In different embodiments, the tubular body wall may by differently shaped, for example it may be frustum conical shaped and/or showing a rounded shape.

The tubular body wall 10 preferably comprises a rear end 12 closed by a rear wall 12 and a front end 14 presenting an opening 18 for loading/unloading laundry and preferably aligned with a loading/unloading door of the laundry washing machine (not shown). The tubular body wall 10 is preferably made by metallic material, preferably made of stainless steel.

The tubular body wall 10 comprises bulges 20 protruding from the tubular body wall 10 towards the rotational axis R.

Preferably, the tubular body wall 10 is metallic and bulges 20 are obtained by punching the tubular body wall 10.

According to an aspect of the invention, the contour 30 of the bulge 20 at said tubular body wall 10 has the shape of a squircle.

Figure 4 shows a squircle in a cartesian coordinate system x and y. The squircle is defined by the equation (x-a)⁴+(y-b)⁴=r⁴.

The squircle substantially shows four rounded corners K1÷K4 joined by four slightly rounded sides S1÷S4.

The squircle is symmetrical and shows two lines of symmetry coinciding with said axis x and y. Hereinafter, it will be indicated the first line of symmetry x as a reference axis X of the squircle. It has to be noted that, due to symmetry of squircle, the reference axis as used in the present invention could indicate also the second line of symmetry y.

In other words, the reference axis X divides symmetrically two opposed slightly rounded sides S2, S4.

It has to be noted that actually the squircle may be roughly symmetrical rather than perfectly symmetrical, in particular due to deformation caused by the punching process.

The bulge 20 preferably comprises side walls 32 extending from said contour 30 and terminating at a bottom wall 34.

Side and bottom walls 32, 34 preferably comprise smooth surfaces advantageously joined therebetween without sharp edges.

Side and bottom walls 32, 34 preferably comprise rounded surfaces with proper radii of curvature.

Rounded walls advantageously offer gentle treatment of the laundry.

According to an aspect of the invention, the bulge 20 is opportunely oriented at the tubular body wall 10 so that the reference axis X of the squircle-shaped contour 30 is inclined with respect to the rotational axis R, as illustrated in Figure 5.

In Figure 5 the rotational axis R is depicted together with the preferred rotation directions C1, C2 of the washing drum 1.

As known, in fact, during a washing cycle the washing drum 1 is preferably rotated in clockwise C1 and counterclockwise C2 directions around the rotational axis R for centrifugally dehydrating the laundry placed therein.

Clockwise C1 and counterclockwise C2 directions are also indicated in Figures 1 and 2.

According to an aspect of the invention, the reference axis X of the squircle-shaped contour 30 is inclined with respect to the rotational axis R of the washing drum 1 to form an angle A.

In a preferred embodiment of the invention, as illustrated in the Figures, the angle A is equal to 45°. Preferably, the angle is comprised between 22,5° and 67,5°.

Preferably, the tubular body wall 10 comprises a plurality bulges 20 placed side by side to define a desired pattern.

As illustrated in Figure 2, bulges 20 are preferably defined almost all over the entire tubular body wall 10 and arranged in a sort of inclined row-column matrix. Two adjacent bulges 20 preferably define therebetween a respective channel 50. The channel 50 is defined by side walls 32 of two adjacent bulges 20.

Each channel 50 is therefore preferably aligned along a direction inclined with respect to the rotational axis R.

Figure 10 shows a first different pattern obtained by bulges 20 displaced in groups G and arranged in inclined row-column spaced one to the other over the tubular body wall 110.

Bulges 20 are preferably arranged in rows along a main axis Y. Preferably, the main axis Y is parallel to the rotational axis R.

Between the groups G of bulges 20 smooth areas A are preferably defined. Each area A may also be considered as a large channel, preferably with a width equal or larger than a corresponding row of bulges, preferably aligned along the rotational axis R.

Figure 11 shows a second different pattern obtained by bulges 20 displaced in inclined rows H spaced one to the other over the tubular body wall 210.

Bulges 20 are preferably arranged in rows along a main axis Y'. Preferably, the main axis Y' is inclined with respect to the rotational axis R.

Between the groups H of bulges 20 smooth areas A' are preferably defined. Each area A' may also be considered as a channel, preferably with a width equal or larger than a corresponding row of bulges, preferably aligned along a direction inclined with respect to the rotational axis R.

The tubular body wall 10 preferably comprises distributed holes 70. Holes 70 are preferably obtained by punching the tubular body wall 10.

Holes 70 help discharging of water from inside of the washing drum 4 to the outside to centrifugally dehydrating the laundry placed therein.

According to a preferred embodiment of the invention, holes 70 are realized in channels 50, as better visible in Figures 3 and 5. Here, preferably, holes 70 are realized only in channels 50.

In different embodiments, holes 70 are differently distributed over the tubular body wall. For example, as illustrated in Figure 9, holes 70 in the tubular body wall 310 are additionally or alternatively realized at side walls 32 and/or bottom walls 34 of the bulges 20.

According to and advantageous aspect of the invention, the bulges 20 thanks to their shape and orientation, as described above, enhances channelling away of water when the washing drum 1 rotates, either in clockwise direction C1 or counterclockwise direction C2.

Referring to Figure 5, when the washing drum 1 rotates in clockwise direction C1, water hits the first/upper corner K1 and lateral sides S1, S2 of the bulge 20. The effect is that water is deflected from the center towards the sides of the bulge 20 along channels 50 between adjacent bulges 20, avoiding creation of turbulence and/or accumulation of water and enhancing conveyance of the water towards discharging holes 70.

Analogously, when the washing drum 1 rotates in counterclockwise direction C2 water hits the third/lower corner K3 and lateral sides S3, S4 of the bulge 20. The effect is that water is deflected from the center towards the sides of the bulge 20 along channels 50 between adjacent bulges 20, avoiding creation of turbulence and/or accumulation of water and enhancing conveyance of the water towards discharging holes 70.

According to a further advantageous aspect of the invention, the bulges 20 thanks to their shape and orientation, as described above, offer gentle treatment of the laundry when the washing drum 1 rotates, either in clockwise direction C1 or counterclockwise direction C2.

Referring to Figures 5 and 8, when the washing drum 1 rotates in clockwise direction C1, laundry hits the first/upper corner K1 and lateral sides S1, S2 of the bulge 20. The effect is that laundry does not stick against the inner wall of the tubular body wall 10 but the laundry is gently detached from the same. Analogously, when the washing drum 1 rotates in counterclockwise direction C2, laundry hits the third/lower corner K3 and lateral sides S3, S4 of the bulge 20. The effect is that laundry does not stick against the inner wall of the tubular body wall 10 but the laundry is gently detached from the same.

In a preferred embodiment of the invention, as better visible in Figure 8, the height D of the side walls is preferably constant, or substantially constant, and the bottom wall 34 is preferably parallel, or substantially parallel, to the tubular body wall 10.

In further preferred embodiments of the invention, the height of the side walls varies, and the bottom wall preferably is not parallel to the tubular body wall. For example, as illustrated in the embodiment of Figure 8A, the height of the side walls 32' decreases continuously and the bottom wall 34' of the bulge 20' is inclined with respect to the tubular body wall 10.

Preferably, the height of the side walls 32' decreases continuously going from the first corner K1 to the third corner K3 (as it can be deduced by comparing distances D1 and D2 depicted in Figure 8A). The bottom wall 34' of the bulge 20' is therefore preferably sloped going from the first corner K1 to the third corner K3.

The effect of this shape is that the laundry is detached differently when the when the washing drum 1 rotates in clockwise direction C1 or in counterclockwise direction C2.

Advantageously, mechanical treatment of the laundry is differentiated between clockwise and counterclockwise rotations of the washing drum 1.

It has thus been shown that the present invention allows all the set objects to be achieved. In particular, it makes it possible to provide a washing drum increasing dehydration performance of the laundry during a washing cycle compared to known laundry washing machines.

While the present invention has been described with reference to the particular embodiments shown in the figures, it should be noted that the present invention is not limited to the specific embodiments illustrated and described herein; on the contrary, further variants of the embodiments described herein fall within the scope of the present invention, which is defined in the claims.