Title

TUB FOR A WASHING MACHINE EQUIPPED WITH A FRONT-MOUNTED BRUSHLESS MOTOR

Technical field

The present invention refers to a washing machine; more specifically, the invention refers to means for driving the drum and for controlling its rotation and its balance.

State of the art

A washing machine or washer, in its current configuration, is formed of a containment structure, internally to which a tank or tub is accommodated, which in turn accommodates a rotatable drum; the latter is driven into rotation by an electric motor. In front-loading washing machines, the motor is conventionally located on the back side with respect to the tub and transmits motion to the drum by way of a transmission belt. In some models of recent production, a direct connection between the motor and the drum is provided .

In all washing machines, it shall be possible to adjust the speed of rotation of the drum as a function of the different steps of the washing cycle; this is the reason why washing machines generally comprise electronic means for controlling the electric motors.

The current washing machines can be equipped with a brushless motor, a motor driven via an inverter, or a conventional motor.

Patent application WO 2006/067649 A2 describes a washing machine equipped with a brushless motor in which there are provided a stator and a rotor arranged one in front of the other, for generating an electromagnetic field. In particular, the washing machine according to WO 2006/067649 A2 has the stator-rotor assembly arranged in correspondence with the back zone of the tub and of the drum. In this way, the contribution to motion determined by the interaction between the rotor and the stator is active in a little advantageous position as far as mechanical work is concerned; in practice, the force exerted onto the drum induces a little advantageous torque in that it is very close (almost corresponding) to the back part of the washing machine .

Patent application WO 2014/084802 A2 describes a washing machine in which there are provided two stator-rotor pairs associated with each other and arranged at different heights along the axis of rotation of the drum with respect to the tub. The solution proposed by this document overcomes the drawbacks of the previous document, relevant to a little effective arrangement of the stator-rotor assembly, but it requires a duplication of the electromagnetic materials used .

Objects and summary of the invention

An object of the present invention is to optimize the distribution of the spaces internally to the washing machine, thus maximizing net loading space.

Another object of the present invention is to reduce the number of the component parts of the washing machine, in particular those subjected to tear and wear, in order to make it stronger, simpler, and cost-effective to manufacture, and also to increase its lifetime and reduce its maintenance requirements.

A further object consists of improving the balance of the drum and of more effectively countering vibrations and offsets induced by unbalanced loads and high speeds of rotation .

The last but not least object of the present invention is to manufacture a washing machine wherein the rotational coupling of the drum with the tub does not oblige to drill the latter.

These objects and others, which will be apparent to those skilled in the art from reading the following text, are achieved thanks to a special arrangement of the stator and rotor elements, which are arranged opposite to each other and are inclined with respect to the longitudinal axis of rotation of the drum. The stator-rotor assembly can be located in a point whatsoever of the outer surface of the drum; in a particularly advantageous solution, the stator and the rotor are applied to the tub and to the drum respectively on the opposite side with respect to the point of connection between the drum and the tub.

The invention here described makes it possible not to have the motor placed outside the tub, thus reducing the component parts of the washing machine as much as possible, and its function is taken over by the tub, whose stator co ^¬ operates with one or several magnets present on the drum. The tub can be manufactured in a single block and the special type of connection to the drum is such that no leakages can occur from the tub.

In a particularly practical solution, the stator assembly is manufactured by using one or several electromagnets, whereas the rotor assembly can be also manufactured by using permanent magnets, in order to prevent the movable parts from being wired, which would be otherwise necessary if using electromagnets.

Brief description of the drawings

In order to better describe the invention and highlight its characteristics and advantages, reference will be made to the attached drawings, which are given for explanatory, non- limitative purposes, wherein:

- Figure 1 is a schematic side view with some parts cut away of a possible exemplary embodiment of the invention;

- Figure 2 is a schematic side view with some parts cut away of a detail relevant to a possible exemplary embodiment of the tub to drum connection according to the invention;

- Figure 3 is a schematic side view with some parts cut away of a detail relevant to a further possible exemplary embodiment of the tub to drum connection according to the invention;

- Figure 4 is a schematic side view with some parts cut away of a detail relevant to a possible exemplary embodiment of a stator position regulation device according to the invention .

Detailed description of an embodiment of the invention

The washing machine comprises a support and containment structure (50), also referred to as cabinet o chassis, internally to which there is arranged a tub (1) for washing laundry .

In the example here illustrated, the support and containment structure (50) includes an opening arranged on the front side, in correspondence with the window (9) for putting laundry therein and taking it out. In the present description, the face of the washing machine equipped with such opening will be referred to as first face (8) and, in the figures attached to the present patent application, it coincides with the front face of the washing machine. The washing tub (1) includes a back wall (10), on the side opposite to that of the first face (8), and, internally thereto, said tub receives a drum (4), whose back portion includes engagement means by means of which it rotationally connects to the back wall of said tub, where corresponding engagement means are provided.

The drum (4) rotates internally to said tub (1) about a longitudinal axis (X) ; in balance and equilibrium conditions, the longitudinal axis (X) of the drum coincides with the longitudinal axis of the rotational engagement means present in the back part of the tub; whenever the operating conditions cause unbalances, the two axes diverge. The rotation of the drum with respect to the tub is induced by motor means comprising a stator (2), fixed to or integral with said washing tub (1), and an integrally movable rotor (5) connected to said drum (4) .

The configuration of the stator (2) and of the rotor (5) is such as to determine an interaction of an electromagnetic nature; in practice, the movement of the drum (4), i.e. its rotation about the longitudinal axis (X) , is obtained by driving the assembly formed of the stator and the rotor, by way of electronic means here not illustrated, which possibly include electronic cards and their respective resident software, the assembly formed of the stator and the rotor thus taking advantage of the created electromagnetic field. Advantageously, said stator (2) and said rotor (5) are arranged in a zone opposite to said back wall (10), i.e. in proximity to said first face (8); according to a preferred embodiment, the stator elements rest on the front portion of the washing tub (1) called flange.

This positioning of the rotor-stator assembly makes it possible to very effectively intervene onto the dynamics of the acting forces, thanks to the distance existing between the connection point, where the drum (4) engages the tub

(1), and the position of the stator (2) and of the rotor

(5) .

In the example illustrated in figure 1, the reference numeral (7) identifies the support springs, which are shown schematically, which the tub (1), containing the drum (4), is hung to; the figure also shows the front part of the washing machine, also shown schematically. According to the preferred embodiment illustrated in the figures, the washing tub (1) is built as a single block and is sealed on the back side because the rotational engagement means of the drum (4) in the point of connection to the hub (1) do not come out from the back wall (10) of the latter, because the drum (4) is secured to the back wall (10) by way of one or several ball bearings (41) accommodated in an internal seat (14) provided on the inner face of said back wall (10), not in communication with the outside of the tub (1) . In this way, the potential leakages which characterize the rotary feedthroughs of those washing machines wherein the motor is arranged behind the tub, are eliminated. In addition, by making one or several ball bearings from stainless steel, a washing machine is realized whose lifetime is actually very long.

Other embodiments are possible, wherein various parts are assembled to form a tub; these parts include, amongst others, seals, but the main advantage of the present solution is in that the tub (1) has no openings towards the outside in its back wall (10) . In practice, the tub (1) is only open on the front side in correspondence with the window (9) or with another convenient opening for accessing the drum ( 4 ) .

The tub (1), just as a non-limitative example, can be sealed and obtained by die-casting or hot welding, without any transmission belts, pulleys, without gaskets or external mechanical parts used for transmitting motion to the drum (4) .

Advantageously, by eliminating the conventional motor, which in the traditional washing machines is back-mounted, the tub for washing machines according to the present invention can be equipped with a drum (4) that, the dimensions of the external container being equal, is bigger. A drum (4) according to the invention extends in the direction of its longitudinal axis (X) by a value close to that of the inner dimension of the tub (1) .

The washing machine according to the present invention comprises a tub (1), with which there is associated a stator (2) which, in the non-limitative example here illustrated, is inclined by 45 degrees with respect to the longitudinal axis (X), exactly as the rotor (5), so as to arrange itself according to such positions as to achieve the mentioned function and all of its respective advantages entailed by such arrangement. The stator (2) and the bunch of magnets of the rotor (5) possibly differ from each other, in a non- limitative example, in the number of coils present in their respective windings, and in volume and dimensions, including the magnets' ones.

In an advantageous embodiment of the invention, there are provided, as a non-limitative example, a stator (2) inclined by 45 degrees and a rotor (5) with a bunch of magnets, similar to those described in international patent application no. PCT/IT2013/000195, located on the drum (4) which, as a non-limitative example, are inclined by 45 degrees, said bunch of magnets operating as a rotor (5) . In the most advantageous embodiment, the stator-rotor assembly is positioned on the front side on the flange (6) because, in this case, the arm of the electromagnetic forces is the maximum one with respect to the point of rotary connection of the drum (4) with respect to the tub (1), but the advantages resulting from the stator-rotor assembly being inclined with respect to the longitudinal axis (X) are evident even if said assembly is positioned differently, for instance on the back side.

If considering the tub - drum geometry and the space available for installing the magnets, one can appreciate the possibility offered by the present invention of being capable of installing even low-cost ferrite magnets, just thanks to the free space put at disposal by the drum (4) ; ferrite magnets can be coated with appropriate protective layers to reduce the risk of oxidation.

Thanks to the pulley and the other component parts having been removed from the back side of the tub (1), it is possible to increase the net depth of the drum (4), thus obtaining a greater load as compared to the known washing machines, the cabinet being equal.

It is worth emphasizing that the special arrangement of the stator-rotor assembly described in the previously cited embodiment makes it possible to also recover the entire circumferential space, because the stator-rotor assembly is not positioned on the side walls of the drum, as it happens in the prior art.

In addition, as compared to the known stator-rotor assemblies, the position being inclined also prevents the drum from possibly getting excessively closed to the tub in the case of an unbalanced load, thus creating electromagnetic imbalances in driving the rotor itself with respect to the stator.

As a matter of fact, thanks to the inclined position the forces generated by the stator-rotor electromagnetic interaction operate in several directions, i.e. tangentially, axially, and radially.

In general, the tangential forces drive the drum into rotation, the axial forces push it towards the back wall and stabilize it, and, by adjusting the radial forces, it is possible to control the distance between the outer surface of the drum and the inner surface of the tub.

The position of the stator-rotor assembly being inclined makes it possible an optimum management of the magnetic forces and allows for an accurate control of the dynamics of the washing machine even during the centrifugation step, by keeping the drum and the tub as much coaxial as possible to each other, thus reducing the offsets of the engagement means, which are usually ball bearings, by means of which the drum is rotationally connected to the tub.

Magnetic force management is either passive or active.

In a possible passive version, the washing machine comprises a positioning device (90) acting onto said stator (2) in order to make it get closer to or move away from the rotor (5), so as to optimize the interaction between the elements. Said positioning device (90) possibly comprises calibrated springs (100), in order to withstand a given magnetic repulsion .

In another possible passive version, the stator (2) rests on an electronic positioning device properly driven by an electronic circuit capable of calculating and balancing the stator (2), by making it get closer to or move away from the rotor (5) whenever the latter unbalances too much with respect to the stator (2), thus permanently holding the stator-rotor electromagnetic interaction to its optimum field value.

In fact, said plurality of equally spaced magnets in front of the drum does not work alone by itself, therefore it becomes working only by adopting the present invention. A demonstration of this circumstance is in having coupled a fixed stator located on the circumference of the flange of the washing machine with a plurality of magnets equally spaced around the drum.

Thanks to the position of the stator (2) being inclined and positioned on the flange (6) and to the magnets being also inclined and positioned in front of a tub (1) embodied according to the present invention, this one is capable of keeping the drum balanced, thanks to a kind of magnetic levitation imposed by the stator (2) opposite to the rotor (5) by way of the magnetic repulsion, thus forming several force vectors all directed in the central direction towards the drum along the axis (X) , even in the presence of a load in the tub ( 4 ) .

A possible active force management version comprises electronic control means which continuously modify the magnetic field of the individual stator elements to induce balancing forces which counter any offsets.

Offsets can be detected by using known methods, for instance by installing one or several position sensors on the tub and connecting them to the electronic control means.

Advantageously, the same electronic control means that manage the stator magnetic field can also be used to detect the effects of any offsets by detecting any variations in the electronic field induced by any changes of distance caused by unbalances and offsets.

All of this determines a greater stability, hence the possibility of getting a lower tear and wear and, consequently, a longer lifetime, the tub (1) being equal; the following advantages are also obtained: reduced vibrations, hence an extremely noiseless tub (1), possibility of installing mono ball bearings and possibility of actually operating at the number of revolutions per minute as expected, irrespective of the load, and having an increased couple, also thanks to the drum (4) being stable during its operation. Increasing the couple results in reducing electric power absorption and, the power consumption being equal, higher performances will be obtained .

A tub (1) equipped with such system can also provide a greater number of revolutions per minute (RPM) as compared to the traditional 1600 RPM of the washing machines presently marketed, and these performances are also provided in the presence of a load in the drum (4), thanks to the technology used for the tub (1), which is moved by a kind of magnetic levitation.

According to a practical embodiment of the invention, the drum (4) is cut on the front side according to a truncated- cone surface and is anchored to the tub from the inside, by way an internal screw (30) . This allows to eliminate all external mechanical parts and to reduce the thickness of the tub (1) . Whereas a conventional drum according to the prior art is anchored to the tub by way of a central hub and is secured thereto by means of a screw located on the outside of the tub, this drum is advantageously the first drum (4) having a screw (30) internal to the drum itself, whereby its depth is increased and the spaces and materials used are reduced. Among the possible explanatory embodiments of the invention, two models are represented here: one using a die- cast tub, illustrated in figure 2, of a maintenance-free type with a mono ball bearing, reduced thickness, reduced costs, and greater depth, and a second tub, that illustrated in figure 3, more robust, dismountable by way of routine maintenance operations, and made up of component parts that are replaceable.

So, with reference to figure 2, it is a matter of a drum (4) having an internal hub (21) which ends in an end of the hub (11) internally to the die-cast tub (1), with a sealing and sliding mechanism (23), which performs anchoring and centering functions, and a fixing screw (30) and a washer (24) . A cap (22) is present, wherein the fixing screw (30) and the washer (24) are accommodated. The die-cast tub (1) possibly includes an integrated mono ball bearing (41) and a ball bearing cover (28) . The drum (4) is separatable from the tub (1) upon removing the fixing screw (30) and the washer (24) . The final segmented hub (7) has such geometrical shape as to be embedded into the drum (4) featuring a mating geometrical shape (29) , so as to provide seizure and sealing with the final hub (11) . Advantageously, this allows to reduce the thickness of the tub (1) and to use one ball bearing (41) only, so as to get a greater depth for the tub (1) located in a standard support and containment structure (50) and substantial savings in manufacturing the tub (1), as well as the possibility of putting a greater number of articles to wash in the washing machine .

In the example illustrated in figure 3, there is provided a normal-maintenance tub (1), with a drum (4), a withdrawable external hub (21) terminating in the hub (11) internally to the die-cast tub (1), said hub (21) being centered thanks to one or several replaceable bearings (41), a fixing screw (30), and a washer (24), all of them being anchored onto the drum (4) . The external hub (21) terminates in a flat head (20) on the outer side of the tub and is the only component part in sight. A cap (22) is present, wherein the fixing screw (30) and the washer (24) are accommodated. In a normal-maintenance washing tub (1), one or several replaceable bearings (41) and a bearing cover (28) are present. The drum (4) is separatable from the tub (1) thanks to the fixing screw (30) and the washer (24) being removed. The final segmented hub (7) has such geometrical shape as to be embedded into the drum (4) having a mating geometrical shape (29) , so as to provide seizure and sealing with the final hub (11) . Advantageously, this results in a greater resistance over time and allows to replace those component parts which are subjected to tear and wear, such as bearings, by simple routine maintenance operations and makes it ideal for durable and repairable models, besides the possibility of putting a greater number of articles to wash in a conventional chassis.

In practice, a preferred embodiment comprises: a support and containment structure (50), including a first face (8) provided with an opening, for putting laundry therein and taking it out; a washing tub (1) arranged internally to said structure; a drum (4) for containing laundry, constrained to such tub on the opposite side with respect to said first face (8), so as to be rotatable about its own longitudinal axis (X); motor means comprising a stator (2) and a rotor (5) suitable for determining an interaction of an electromagnetic nature. In particular, the first face (8) is a front face, said axis (X) being substantially horizontal. Advantageously, the washing machine is characterized in that said rotor (5) and said stator (2) are secured to said drum (4) and to said tub (1) respectively, their own active surfaces being arranged opposite to each other and defining an angle with said axis (X) . In practice, the rotor (5) can be made up of a magnet ring arranged opposite to one or several stator elements.

Advantageously, said active surfaces of the stator (2) and of the rotor (5) form an angle ranging from 30° to 60° with respect to such axis (X) , preferably 45° as with the non- limitative example illustrated in the drawings.

Figure 1 shows one stator element, arranged in the lower side; advantageously, the stator elements can be distributed along a circumference and form a stator ring opposite to the rotor (5) . Four equally angularly spaced rotor elements can be provided, for instance, placed in correspondence with the four angles formed by the quadrilateral that defines the vertical cross section of the structure of the washing machine . The tub (1), the flange (6), and the drum (4) can be separated from each other by gaskets.

It is understood indeed that the executive details can however vary equivalently in shape, dimensions, nature of materials used, without departing from the scope of the inventive idea adopted, and consequently remaining within the limits of protection granted by the present patent.

For instance, the teachings of the present patent application can also be applied to top loading washing machines instead of front loading washing machines; in this event a preferred embodiment entails that said first face (8) is the upper face of the box-like body, which performs the tub support and containment function, and the longitudinal axis (X) of the drum is substantially vertical. Different configurations are also possible, wherein the tub and the drum develop according to oblique axes.