EP2292137B1

EP2292137B1 - Washing machine, in particular a dishwasher

Info

Publication number: EP2292137B1
Application number: EP10169868.6A
Authority: EP
Inventors: Gloria Ghezzi; Marco Wilhelmus Gerhardus Ten Bok
Original assignee: Whirlpool EMEA SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2009-07-24
Filing date: 2010-07-16
Publication date: 2017-08-23
Anticipated expiration: 2030-07-16
Also published as: ITTO20090566A1; EP2292137A1

Description

The present invention relates to a washing machine, in particular a dishwasher, according to the preamble of claim 1.
Dishwashers are traditionally adapted to wash crockery, which for this purpose is housed in at least one rack inside a tub and is sprayed with a wash liquid (normally water and detergent and/or rinse aid or the like) coming out of a rotary sprayer arranged on said rack. Dishwashers usually comprise a couple of racks positioned at different heights, each of said racks being associated with one rotary sprayer.
In such washing machines, the wash liquid is circulated by a pump and flows through a hydraulic circuit that includes the tub, a pump intake duct, a sprayer supply duct and the sprayers themselves, to return then back into the tub.
Aiming at improving the washing action, the wash liquid is heated by a suitable electric resistor arranged within the hydraulic circuit.
In the hydraulic circuits of known washing machines, the pump that circulates the wash liquid is often subject to cavitation, in particular when said wash liquid is rich in foam formed by the wash agents and/or when a portion of said liquid is lacking.
In short, cavitation is a physical phenomenon that places the motor of the washing machine in a suffering state, since it has to move a mixture consisting of a liquid and an aeriform substance.
Cavitation is an undesired phenomenon leading to several problems.
In fact, cavitation and the resulting loss of efficiency of the pump generate considerable noise and a drop in the efficiency of the hydraulic circuit of the washing machine, resulting in a pressure drop at the sprayers and unsatisfactory washing performance.
Moreover, cavitation makes it more difficult to control the speed of the pump impeller, since the pump motor operates in a condition which is different from the optimal working point for which it has been designed.
Document EP 1 428 926 A2 discloses a washing machine comprising a pump, the pump being fitted with a rotary assembly and the rotary assembly being associated with a synchronous motor. The pump comprises a shaft provided with appropriate flywheel and eccentric protrusion and an impeller provid with ring-shaped cavity accommodating protrusion. The flywheel increases the inertia of the shaft to reduce a separation of the cavity from the protrusion.
In this frame, it is the main object of the present invention to overcome the above-mentioned drawbacks by providing a washing machine, in particular a dishwasher, designed in a manner such as to comprise a hydraulic circuit which is scarcely or not at all affected by cavitation-induced problems.
In particular, it is an object of the present invention to considerably reduce the noise generated by the washing machine in the presence of pump cavitation conditions.
It is another object of the present invention to provide a washing machine, in particular a dishwasher, so designed as to cause the pump motor to operate in an optimal manner.
It is a further object of the present invention to provide a washing machine having a hydraulic circuit which is highly efficient even in the presence of a cavitation phenomenon.
Said objects are achieved by the present invention through a washing machine, in particular a dishwasher, incorporating the features set out in the appended claims, which are intended as an integral part of the present description.
Further objects, features and advantages of the present invention will become apparent from the following detailed description and from the annexed drawings, which are supplied by way of non-limiting example, wherein:

Fig. 1 is a schematic sectional side view of a washing machine, in particular a dishwasher, according to the present invention;
Fig. 2 is an exploded view of a pump of the washing machine of Fig. 1;
Fig. 3 is an exploded view of a rotary assembly of the pump of Fig. 2.

Referring now to the annexed Fig. 1, reference numeral 1 designates as a whole a washing machine, in particular a dishwasher, according to the present invention.
Said washing machine 1 comprises a tub 2 in which the crockery to be subjected to the action of a wash liquid is placed.
In particular, the tub 2 of Fig. 1 houses a first rack 3A and a second rack 3B, which are typically slideable on suitable guides (not shown), so that they can be extracted from the tub 2. In this regard, it should be noted that the machine 1 is shown in Fig. 1 with a door partially overturned and the first rack 3A partially extracted for illustration purposes only. It is clear that, for the purposes of the present invention, the washing machine 1 may be of the type comprising a single rack 3A, 3B, said single rack 3A, 3B being in particular of the fixed type.
A first sprayer 5A and a second sprayer 5B are respectively associated in a known manner with said first rack 3A and second rack 3B; as known, said first sprayer 5A and second sprayer 5B are rotatable relative to the first rack 3A and second rack 3B, so as to spray, when rotating, all the crockery contained in said first rack 3A and second rack 3B.
The washing machine 1 also comprises a pump 10, in particular a centrifugal pump, for circulating said wash liquid in a hydraulic circuit comprising a plurality of ducts afferent to and from the tub 2.
In particular, in addition to said first sprayer 5A and second sprayer 5B, said plurality of ducts comprises:

a first duct 6A for connecting said pump 10 to the first sprayer 5A;
a second duct 6B for connecting said pump 10 to the second sprayer 5B;
a flow distributor 7, typically provided with a shutter, adapted to open a passage for the wash liquid towards the first duct 6A, towards the second duct 6B, or towards both ducts 6A and 6B.

Furthermore, the washing machine 1 also comprises heating means (not shown in the drawings), such as an electric resistor, for heating the wash liquid in order to improve the washing action.
Referring now to Fig. 2, there is shown an exploded view of the pump 10 according to the present invention, which comprises:

a scroll 11 comprising an intake duct 11A for connecting the pump 10 to the tub 2 and provide a central intake of wash liquid, said scroll 11 further comprising a delivery duct 11B which provides a tangential delivery of wash liquid towards the first duct 6A, towards the second duct 6B, or towards both ducts 6A and 6B;
a body 20 comprising a motor and electric components (not shown in Fig. 2) of the pump 10;
an impeller 30 arranged inside said scroll 11 and associated with the body 20.

As can also be seen in Fig. 3, said impeller 30 comprises a plurality of vanes 31 arranged between a first disc 32 and a second disc 33, said first disc 32 having an aperture 32A through which the wash liquid can flow.
As known, the centrifugal force produced by the rotating impeller 30 generates a vacuum which sucks the wash liquid from the intake duct 11A and projects it into the delivery duct 11B of the scroll 11.
Fig. 3 shows that the pump 10 is fitted with a rotary assembly that comprises said impeller 30, a shaft 40 and a magnet 50.
In particular, said shaft 40 comprises a first end 41 adapted to be associated with the impeller 30 and a second end 42 adapted to be associated with the magnet 50, preferably by inserting said second end 42 into a passage 51 obtained in said magnet 50.
According to the present invention, said rotary assembly 30, 40, 50 is associated with a synchronous motor (not shown in the drawings) and is so conceived as to have a moment of inertia between 145 gr•cm² and 305 gr•cm² relative to an axis X.
In Fig. 3 said axis X is indicated by a dashed-dotted line and substantially coincides with the axis of rotation of said rotary assembly 30, 40, 50.
Preferably, said rotary assembly 30, 40, 50 is so conceived as to have a moment of inertia between 165 gr•cm² and 205 gr•cm².
The particular design of the rotary assembly 30, 40, 50 according to the present invention allows to obtain a washing machine 1 which is considerably less noisy in the presence of cavitation conditions, while still providing adequate efficiency.
Furthermore, the design of the rotary assembly 30, 40, 50 according to the present invention causes the motor of the pump 10 to operate in an optimal manner.
According to the present invention, the impeller 30 is so conceived as to have a moment of inertia between 100 gr•cm² and 260 gr•cm² relative to said axis X.
In a preferred embodiment, said impeller 30 is so conceived as to have a moment of inertia between 120 gr•cm² and 160 gr•cm².
As shown in Fig. 3, the impeller 30 is associated with an additional element or flywheel 60 which stabilizes the wash liquid pressure, in particular on said plurality of vanes 31 and in the delivery duct 11B of the pump 10.
In particular, said additional element or flywheel 60 promotes and keeps substantially constant the rotation of the impeller 30, even when there is foam in the wash liquid and it is more likely that cavitation occurs in the wash liquid near the impeller 30 or other components of the rotary assembly 30, 40, 50.
Preferably, said additional element 60 is associated with an outer surface 32B of the first disc 32 and has a substantially annular shape, so as to allow the wash liquid to flow into the aperture 32A of the first disc 32.
In particular, said additional element 60 is co-moulded with said outer surface 32B of the first disc 32.
As an alternative, the impeller 30 and the additional element 60 may be so designed as to include mutual engaging means (not shown in the drawings).
It is understood that, in accordance with the present invention, the particular design of the impeller 30 and/or of the additional element 60 may also be implemented in a washing machine having a pump 10 fitted with a motor other than a synchronous one, e.g. a direct or alternating current brushless motor.
The advantages of a washing machine, in particular a dishwasher, according to the present invention are apparent from the above description.
The special design of the rotary assembly 30, 40, 50 and/or of the impeller 30 according to the present invention allows to obtain a washing machine 1 which eliminates or at least limits any problems caused by cavitation.
In particular, the washing machine 1 according to the present invention is so designed as to be considerably less noisy in the presence of cavitation conditions, while still providing adequate efficiency.
A further advantage of the washing machine 1 according to the present invention lies in that it allows the motor of the pump 10 to operate in an optimal manner.
In the practical implementation of the invention the illustrated details may have different shapes or be replaced with other technically equivalent elements.
Among the many possible variants, a flywheel 60 may be associated with one component of said rotary assembly 30, 40, 50 in order to keep the rotation of the rotary assembly 30, 40, 50 substantially constant and stabilize the pressure of the wash liquid, in particular within a delivery duct 11B of the pump 10.

Claims

Washing machine (1), in particular a dishwasher, of the type comprising:
- a tub (2) in which crockery to be subjected to the action of a wash liquid is placed;

- a pump (10), in particular a centrifugal pump, for circulating said wash liquid in a hydraulic circuit comprising a plurality of ducts (5A, 5B, 6A, 6B, 7, 11A, 11B) afferent to and from said tub (2), said pump (10) being fitted with a rotary assembly (30, 40, 50), in particular comprising an impeller (30), a shaft (40) and a magnet (50), said rotary assembly (30, 40, 50) being associated with a synchronous motor,
characterized in that
said rotary assembly (30, 40, 50) is so conceived as to have a moment of inertia between 145 gr·cm² and 305 gr·cm² relative to an axis (X) said axis (X) substantially coinciding with the axis of rotation of said rotary assembly (30, 40, 50) and in that
said impeller (30) comprises a plurality of vanes (31) arranged between a first disc (32) having an aperture (32A) through which the wash liquid can flow and a second disc (33), said impeller (30) being associated with an additional element or flywheel (60),
said additional element (60) is associated with an outer surface (32B) of the first disc (32) and has a substantially annular shape, so as to allow the wash liquid to flow into the aperture (32A) of the first disc (32).
Washing machine (1) according to claim 1, characterized in that said rotary assembly (30, 40, 50) is so conceived as to have a moment of inertia between 165 gr·cm² and 205 gr·cm².
Washing machine (1) according to any of the preceding claims, characterized in that said impeller (30) is so conceived as to have a moment of inertia between 100 gr·cm² and 260 gr·cm² when rotating about said axis (X).
Washing machine (1) according to claim 3, characterized in that said impeller (30) is so conceived as to have a moment of inertia between 120 gr·cm² and 160 gr·cm².
Washing machine (1) according to claim 4, characterized in that said additional element (60) is co-moulded with said outer surface (32B) of the first disc (32).