[0001] This invention relates to a washing appliance, in particular a washing appliance
equipped with a system designed to prevent noise from being produced by the drainage
pump under certain working conditions.
[0002] Washing appliances comprise electrical appliances such as, for example:
- laundry washers for washing clothes, bed sheets, etc.;
- dishwashers for washing dishes, cutlery, pans, etc.
[0003] In particular, washing appliances called "laundry washers" are suitable for carrying
out at least a washing treatment on textile articles made of any fibre or in any colour
and include machines known as "washing machines" and machines known as "washer dryers",
if in addition to washing they also carry out at least a treatment for drying textile
articles.
[0004] There are washing machines comprising a washing tank with a drum in which the laundry
to be washed is placed. A pipe for draining the washing tank extends from the washing
tank. The drainage pipe is connected to a drainage pump through which the washing
water from the washing tank is pumped. After the main washing treatment and after
each rinse, the washing water used is drained out of the tank. To enable the washing
water to be drained out of the washing machine, an electronic circuit board activates
the drainage pump for a preset length of time.
[0005] This causes some disadvantages, however.
[0006] When the suction inlet of the drainage pump is no longer fully occupied by water,
the pump begins sucking in air together with the remaining water, producing an unpleasant
noise.
[0007] To this must be added the noise produced by the small quantity of washing water that
remains trapped in the drainage pump delivery pipe and which moves up and down the
pipe under the action of the pump itself.
[0008] This invention has for an aim to overcome the above mentioned disadvantages by providing
a washing appliance which prevents the drainage pump from producing unpleasant noise
under certain working conditions.
[0009] Another aim of the invention is to provide a washing tank that optimizes the operation
of some of the components of the washing appliance.
[0010] A further aim of the invention is to provide a washing appliance that reduces power
consumption.
[0011] A yet further aim of the invention is to provide a washing appliance that allows
the above aims to be achieved with only minor modifications to the basic structure
of prior art washers.
[0012] These aims and others, which are more apparent in the description which follows,
are achieved, in accordance with the present invention, by a washing appliance with
the structural and functional features described in the independent claims herein.
Alternative embodiments of the appliance are described in the dependent claims.
[0013] The invention will now be described in more detail with reference to the accompanying
drawing, which illustrates a non-limiting preferred embodiment of it.
[0014] Figure 1 is a schematic view of a washer according to this invention.
[0015] With reference to Figure 1, the numeral 1 denotes a washing appliance that uses a
washing liquid. The washing liquid usually consists of a mixture of water and cleaning
agents such as detergents and other washing aids (bleach, fabric softener, etc).
[0016] The washing appliance 1 may be one of several different kinds of machine but in the
preferred embodiment it is a laundry washer or a dishwasher. The washing appliance
1 is designed preferably for household use.
[0017] The washing appliance 1 comprises a washing tank 2 suitable for containing the washing
liquid used for the washing treatment. Inside the washing tank 2, the washing appliance
1 also comprises means 7 for containing the articles to be washed, said containing
means 7 defining at least a space for accommodating the articles to be washed. In
Figure 1, for example, which schematically illustrates a laundry washer without limiting
the scope of the invention, the containing means 7 comprise a rotary drum in which
the laundry to be washed is placed. Similarly, in the case of a dishwasher, the containing
means 7 comprise one or more racks which can usually be pulled out by means of suitable
carriages.
[0018] The washing appliance 1 also comprises:
- a pipe 3 for draining out the washing liquid and in fluid communication with the washing
tank 2;
- a drainage pump 6 operatively connected to the drainage pipe 3;
- means 4 for detecting a free surface level of a column of the washing liquid. The
column is located immediately upstream of the drainage pump 6 relative to the direction
in which the washing liquid flows out of the washing tank 2 during its drainage. The
column is preferably inside the drainage pipe 3 and may also extend inside the washing
tank 2.
[0019] The drainage pipe 3 advantageously extends from the bottom portion of the washing
tank 2; during drainage, the washing liquid flows out through the drainage pipe 3
under the action of the drainage pump 6.
[0020] The drainage pump 6 normally used is a centrifugal pump. The drainage pump 6 is suitably
mounted on the drainage pipe 3 and is designed in such a way that the washing liquid
flows through it during its operation. Usually, the drainage pipe 3 extends both upstream
and downstream of the drainage pump 6.
[0021] The washing appliance 1 comprises means 5, operatively connected to the detecting
means 4, for controlling the drainage pump 6. The detecting means 4 detect a first
condition where the water level is less than or equal to a first predetermined level.
[0022] At least during a predetermined part of the washing cycle, if the drainage pump 6
is in operation, the control means 5 inhibit the operation of the drainage pump 6
upon occurrence of the first condition sensed by the detecting means 4. Appropriately,
the detecting means 4 apply a first condition detected signal to the control means
5, either directly or indirectly. Advantageously, the detecting means 4 sense the
level of the free surface of the column and compare it with a predetermined reference
level. The predetermined reference level is below the level of the free surface of
the column and, in particular, is located below the first predetermined level.
[0023] In the preferred embodiment, during the entire washing cycle, if the drainage pump
6 is in operation, the control means 5 inhibit the operation of the drainage pump
6 upon occurrence of the first condition.
[0024] In this case, the predetermined part of the washing cycle in which the detecting
means 4 inhibit the operation of the drainage pump 6 upon occurrence of the first
condition coincides with the entire duration of the washing cycle. By washing cycle
is meant the pre-wash step, if any, the rinse step, if any, and the main wash step
in their entirety.
[0025] Alternatively, in another embodiment, the predetermined part of the washing cycle
in which the control means 5 inhibit the operation of the drainage pump 6 might not
include the final step of draining the washing liquid, this step being usually associated
with the final rinse. That is because, in the final drainage step, to enable as much
washing liquid as possible to be drained out, it may be necessary to set the timer
of the drainage pump 6 so that the pump operates for a slightly extended length of
time.
[0026] In the first condition, the washing liquid constitutes a liquid barrier to the air
inside the drainage pipe 3. The barrier is at least partly upstream of the drainage
pump 6 relative to the direction in which the washing liquid flows out of the washing
tank 2 during its drainage. The barrier obstructs at least a full section of the drainage
pipe 3 upstream of the drainage pump 6 and thereby prevents the drainage pump 6 from
sucking in air, in addition to the washing liquid, from the washing tank 2.
[0027] Also in this regard, the washing appliance 1 comprises an interface connecting a
suction zone 60 of the pump 6 to the drainage pipe 3, said interface being fully immersed
in the washing liquid when the first predetermined level occurs.
[0028] The first predetermined level of the free surface is between 0 and 30 mm above a
minimum level necessary for the interface to be fully immersed in the washing liquid.
Preferably, the first predetermined level is preset at a level of the free surface
of around 20 mm above the minimum level necessary for the interface to be fully immersed
in the washing liquid. This provides a good safety margin and minimizes the risk of
the drainage pump 6 sucking in air together with the washing liquid.
[0029] During a predetermined part of the washing cycle, the control means 5 start the drainage
pump 6 upon occurrence of a predetermined second condition after the first condition,
the occurrence of the second condition being sensed by the detecting means 4; the
detecting means 4 appropriately applying a second condition detected signal to the
control means 5, either directly or indirectly. Just before the predetermined second
condition occurs, the level of the washing liquid column upstream of the drainage
pump 6 is on the rise. In the predetermined second condition, the level of the free
surface is greater than or equal to a second predetermined level, which is greater
than the first predetermined level and smaller than any other level such that the
space that accommodates the articles to be washed would be at least partly immersed
in the washing liquid to be drained out. The occurrence of the second condition is
typical of a laundry washer but is not usual in dishwashers. That is because in laundry
washers, during the step in which the drainage pump is in operation or after the occurrence
of the first condition, there may be a spin-drying step during which more washing
liquid may accumulate at the bottom of the washing tank 2, which must be disposed
of and which must not come into contact with the articles in the drum again. It is
also important that the drum be free to rotate without coming into contact with the
washing liquid to be drained out from the washing tank 2: given the high rotation
speeds of the drum, this is particularly true during spin-drying also to prevent noise
from being produced.
[0030] The second predetermined level is between 1 and 20 mm below the level in which the
washing liquid reaches the space of the containing means 7 where the articles to be
washed are placed. Preferably, the second predetermined level is preset at a level
of the free surface of around 15 mm below the level in which the washing liquid reaches
the space of the containing means 7 where the articles to be washed are placed. This
prevents the washing liquid at the bottom of the washing tank from coming into contact
with the articles to be washed in the containing means 7. When the washing liquid
is being fed into the washing tank 2 through the inlet valve, the control means 5
are inhibited. Thus, the drainage pump 6 is not activated at the wrong time for example
when the washing liquid must not be drained out.
[0031] Advantageously, the detecting means 4 comprise a pressure sensor 40.
[0032] Advantageously, the pressure sensor 40 can continuously measure the level of the
free surface of the washing liquid with respect to the reference level located below
the free surface. The pressure sensor 40 comprises what in the trade is commonly known
as "linear pressure switch".
[0033] The pressure sensor 40 also makes it possible to control the washing liquid level
during the step of feeding the washing liquid into the washing tank 2 and/or provides
prior warning of the risk of the washing liquid overflowing from the washing tank
2. The use of a pressure sensor 40 that continuously measures the level of the free
surface is highly advantageous and makes it unnecessary to fit an additional bistable
pressure switch. Bistable pressure switches are normally used in traditional washing
machines to control the level of washing liquid during the feeding of washing liquid
into the washing tank 2.
[0034] The pressure sensor 40 that continuously measures the level of the free surface comprises
a measuring point 41 located upstream of the drainage pump 6 relative to the direction
in which the washing liquid flows out of the washing tank 2 during its drainage. When
the first predetermined level occurs, the measuring point 41 is fully immersed in
the washing liquid column. Advantageously, the above mentioned predetermined reference
level is at the same level as the measuring point 41.
[0035] As illustrated by way of non limiting example in Figure 1, the measuring point 41
is made on the drainage pipe 3.
[0036] The pressure sensor 40 that continuously measures the level of the free surface associates
a specific command with the detection of each of at least four predetermined levels
that occur during the normal and correct operation of the washing appliance: the occurrence
of the first and second predetermined level during a predetermined part of the washing
cycle is associated, respectively, with the starting and stopping of the drainage
pump 6; the occurrence of a third and fourth predetermined level during a predetermined
part of the washing cycle respectively enables and inhibits the feeding of the washing
liquid into the washing tank 2. The occurrence of the third predetermined level while
the washing liquid is being drained out does not start washing liquid feed. Similarly,
the occurrence of the second predetermined level while the washing liquid is being
fed into the washing tank 2 out does not start the drainage pump 6. By way of non-limiting
example, the first, second, third and fourth levels might be associated with a height
of the free surface of the washing liquid column of 15mm, 30mm, 60mm and 90mm from
the measuring point 41, respectively. If necessary, the pressure sensor 40 might also
be used to detect a fifth level indicating a fault or excessively high level of washing
liquid in the washing tank 2. The fifth level is normally associated with counteractions
such as immediate activation of the drainage pump 6 to prevent the water from overflowing
from the washing tank.
[0037] The operation of the washing appliance 1 during use may be described very briefly
by way of example as follows: after washing and/or a rinsing step, the drainage pump
6 is started in order to drain out the washing liquid. Upon occurrence of the first
condition, the detecting means 4 stop the drainage pump 6. In the case of a laundry
washer, this step is usually followed by a spin-drying step during which a certain
amount of washing liquid is released by the washed laundry and settles at the bottom
of the washing tank 2: as a result, the washing liquid level in the washing tank 2
rises. When the detecting means 4 sense that the washing liquid in the washing tank
2 has reached a predetermined level associated with a second condition, the drainage
pump is started again to drain out the washing liquid that has accumulated.
[0038] The invention brings important advantages.
[0039] First of all, it minimizes the noise produced by the drainage pump under certain
working conditions.
[0040] Secondly, it allows the drainage pump to be used only when its use is necessary.
Thus, besides reducing power consumption, it reduces pump wear and hence extends pump
life.
[0041] The invention can be modified and adapted in several ways without thereby departing
from the scope of the inventive concept.
[0042] Moreover, all details of the invention may be substituted by other technically equivalent
elements.
[0043] In practice, the embodiments of the invention may be made from any material, and
in any size, depending on requirements.
1. A washing appliance that uses a washing liquid, comprising:
- a washing tank (2) suitable for containing the washing liquid used for a washing
treatment;
- a pipe (3) for draining out the washing liquid and in fluid communication with the
washing tank (2);
- a drainage pump (6) operatively connected to the drainage pipe (3);
- means (4) for detecting a free surface level of a column of the washing liquid,
said column being located immediately upstream of the drainage pump (6) relative to
the direction in which the washing liquid flows out of the washing tank (2) during
its drainage;
the washing appliance being
characterized in that it comprises means (5), operatively connected to the detecting means (4), for controlling
the drainage pump (6), said detecting means (4) detecting a first condition where
the water level is less than or equal to a first predetermined level; and
characterized in that at least during a predetermined part of the washing cycle, if the drainage pump (6)
is in operation, the control means (5) inhibit the operation of the drainage pump
(6) upon occurrence of the first condition sensed by the detecting means (4).
2. The washing appliance according to claim 1, characterized in that during the entire washing cycle, if the drainage pump (6) is in operation, the control
means (5) inhibit the operation of the drainage pump (6) upon occurrence of the first
condition sensed by the detecting means (4).
3. The washing appliance according to claim 1 or 2,
characterized in that in the first condition, the washing liquid constitutes a liquid barrier to the air
inside the drainage pipe (3), the barrier being at least partly upstream of the drainage
pump (6) relative to the direction in which the washing liquid flows out of the washing
tank (2) during its drainage.
4. The washing appliance according to any of the foregoing claims, characterized in that it comprises an interface connecting a suction zone (60) of the pump (6) to the drainage
pipe (3), said interface being fully immersed in the washing liquid when the first
predetermined level of the free surface of the washing liquid column occurs.
5. The washing appliance according to claim 4, characterized in that the first predetermined level of the free surface is between 0 e 20 mm above a minimum
level necessary for the interface to be fully immersed in the washing liquid.
6. The washing appliance according to any of the foregoing claims, characterized in that, inside the washing tank (2), it comprises means (7) for containing the articles
to be washed, said containing means (7) defining at least a space for accommodating
the articles to be washed, and characterized in that during a predetermined part of the washing cycle, the control means (5) start the
drainage pump (6) upon occurrence of a predetermined second condition after the first
condition, the occurrence of the second condition being sensed by the detecting means
(4); just before the predetermined second condition occurs, the level of the washing
liquid column upstream of the drainage pump (6) being on the rise, in the second condition,
the level of the free surface being greater than or equal to a second predetermined
level, said second predetermined level being greater than the first predetermined
level and smaller than any other level such that the space that accommodates the articles
to be washed would be at least partly immersed in the washing liquid to be drained
out.
7. The washing appliance according to claim 6, characterised in that the second predetermined level of the free surface is between 1 and 20 mm below the
level in which the washing liquid reaches the space of the containing means (7) where
the articles to be washed are placed.
8. The washing appliance according to any of the foregoing claims, characterised in that the detecting means (4) comprise a pressure sensor (40).
9. The washing appliance according to claim 8, characterized in that the pressure sensor (40) can continuously measure the level of the free surface of
the washing liquid with respect to a predetermined reference level located below the
free surface.
10. The washing appliance according to claim 8 or 9, characterized in that the pressure sensor (40) also makes it possible to control the washing liquid level
during the step of feeding the washing liquid into the washing tank (2) and/or provides
prior warning of the risk of the washing liquid overflowing from the washing tank
(2).
11. The washing appliance according to any of the foregoing claims from 8 to 10, characterized in that the pressure sensor (40) comprises a measuring point (41) located upstream of the
drainage pump (6) relative to the direction in which the washing liquid flows out
of the washing tank (2) during its drainage, the measuring point (41) being fully
immersed in the washing liquid column in the first condition.
12. The washing appliance according to claim 11, characterised in that the measuring point (41) is made on the drainage pipe (3).