WO2017137072A1

WO2017137072A1 - Dishwasher and washing cycle for such dishwasher

Info

Publication number: WO2017137072A1
Application number: PCT/EP2016/052737
Authority: WO
Inventors: Asli GENCER OZEL; Basak BENGU; Osman Gokhan Ersoy
Original assignee: Arcelik Anonim Sirketi
Priority date: 2016-02-09
Filing date: 2016-02-09
Publication date: 2017-08-17

Abstract

A dishwasher (1) programmed to perform at least a washing phase and, subsequently, at least a first rinsing phase and comprising a tub (2) in which the dishes to be washed are placed, a hydraulic circuit (3) for circulating a washing liquid through the tub (2), a dispensing system (10) activable for introducing a flocculant into the washing liquid in the hydraulic circuit (3) in order to promote the aggregation of detergent and dirt particles therein contained for the formation of floes (F); a control unit (11) controlling the operation of the dispensing system (10) and programmed to activate the dispensing system (10) at least at the end of the washing phase, before the first rinsing phase; and separation means (12) for separating the formed floes (F) from the washing liquid in order to render the latter enough clean to perform the subsequent first rinsing phase. By these measures water and energy consumption can be reduced due to reusing the washing liquid.

Description

[Title established by the ISA under Rule 37.2] DISHWASHER AND WASHING CYCLE FOR SUCH DISHWASHER

The present invention relates to a dishwasher, in particular to a domestic dishwasher, having an improved energy and water consumption. The present invention further relates to a washing cycle for such dishwasher.

As it is known, the washing cycle for a dishwasher typically comprises a pre-washing phase, during which the dishes to be washed, placed in the tub, are sprayed with washing liquid which generally is not heated, a washing phase, which is performed with heated washing liquid, a cold rinsing phase aimed to remove dirt and detergent residuals from the surface of the dishes and a final hot rinsing phase.

In order to limit the amount of water required to perform the entire washing cycle, the water used is changed only at the beginning of each of the phases while the same water, in case mixed with detergent or other washing or rinsing aids, is recirculated through the tub during each of the phases.

In the traditional washing cycle above described the hot dishes that just underwent the main washing phase with heated washing liquid, are cooled down in the cold rinsing phase by being sprayed with cold water. Subsequently, the cooled dishes are again heated up during the hot rinsing phase, by being sprayed with heated water.

This requires a high amount of energy to be consumed in order to reheat the water and the dishes in the hot rinsing phase, leading to a poor energy efficiency of the dishwasher.

It is known in the state of the art from the international patent application n. WO 2012/123927 to add a flocculating agent to the washing liquid recirculating during the washing phase in order to promote the agglomeration of the food soil particles for forming agglomerated particles which are then separated from the washing liquid by using a hydrocyclone. In particular the flocculating agent is preferably added directly in the formulation of the detergent. This allows to use lower amount of water during the washing phase, since the washing liquid is maintained cleaner while at the same time filming phenomena on the dishes being cleaned due to the food soil accumulation in the sump are avoided.

Therefore the above mentioned international application solves the problem of how to reduce the water consumption in a washing cycle by diminishing the amount of water used during the washing phase, thanks to the addition of a flocculating agent into the detergent.

An objective of the present invention is to provide a dishwasher and a washing cycle for such dishwasher allowing an improved energy and water consumption, without compromising the washing performance.

This objective has been achieved by the dishwasher as defined in claim 1 and by the washing cycle as defined in claim 8. Further achievements have been attained by the subject-matters respectively defined in the dependent claims.

In the dishwasher of the present invention and in the washing cycle performed by the dishwasher, a flocculant is added to the washing liquid that performed the washing phase in order to remove dirt and detergent particles therein contained and to obtain a sufficiently clean water to perform the subsequent first rinsing phase. This allows to save both water, since a new intake of fresh water is not needed to perform the first rinsing phase, and energy, since the dishes and tub are maintained warm during the first rinsing phase and a lower amount of energy is required to heat up the water for the second and last rinsing phase.

To this aim, the dishwasher comprises a dispensing system, for introducing the flocculant in the washing liquid, separation means for removing the flocs created upon the action of the flocculant, and a control unit programmed to control the operation of the dispensing means and, if required, of the separation means.

In an embodiment the dispensing system of the dishwasher is designed to dispense a flocculant in the liquid or in the solid form and it comprises a reservoir, distinct from the detergent reservoir.

In another embodiment, the dispensing system is designed to dispense a flocculant in the solid form and the dishwasher comprises mixing means for mixing the flocculant with the washing liquid.

The separation means in an embodiment comprises a filter that can be also a cyclonic filter, while in a different embodiment comprises a sedimentation receptacle.

The washing cycle according to the invention comprises hence a washing phase, a main dirt removing phase, during which the flocculant is introduced into the washing liquid that performed the washing phase in order to promote the aggregation of detergent and dirt particles and the formation of flocs, and during which the formed flocs are separated from the washing liquid for obtaining cleaned water, and a first rinsing phase, during which the dishes are rinsed with such cleaned water.

In a version of the washing cycle, the flocculant is a salt based flocculant and in particular is aluminum potassium sulfate based and, in a further version, it is introduced in an amount between 30 mg/l and 50 mg/l into the washing liquid during the dirt removing phase.

According to a version of the washing cycle, the flocculant is provided in a 50% solution in water.

In a version, the washing cycle further comprises a disinfection phase, during which the washing liquid is irradiated with ultraviolet light. To this aim, the dishwasher according to the invention comprises ultraviolet light emitting means.

In a version, the washing cycle further comprises a pre-washing phase, preceding the washing phase, and a preliminary dirt removing phase, following the pre-washing phase and preceding the washing phase, during which a flocculant is introduced into the washing liquid that performed the pre-washing phase, for obtaining a cleaned water to be used in the washing phase. To this aim, the dishwasher according to the invention is programmed to perform the pre-washing phase and the control unit is further programmed to activate the dispensing system at the end of the pre-washing phase, before the washing phase, in order to introduce a dose of flocculant into the washing liquid that performed the pre-washing phase.

Additional advantages of the dishwasher and of the washing cycle of the present invention will become apparent with the detailed description of the embodiments with reference to the accompanying drawings in which:

Figure 1 – is a schematic view of a dishwasher according to the present invention.

Figure 2 – is a graphic showing the water intake during each phase of a traditional washing cycle and the amount of water that is saved during a washing cycle according to the invention.

Figure 3 – is a graphic showing the temperature variation during each phase of a traditional washing cycle (with a continuous line) and the temperature variation during each phase of the washing cycle according to the invention (with a dotted line), highlighting the avoided temperature drop and, consequently, the amount of energy saved.

The reference signs appearing on the drawings relate to the following technical features.

Dishwasher
Tub
Hydraulic circuit
Racks
Spray arms
Sump
Recirculation ducts
Recirculation pump
Heater
Dispensing system
Control unit
Separation means
Reservoir
Drain duct

The dishwasher 1 comprises a tub 2 in which the dishes, i.e. dishes, kitchenware, tableware, crockery etc., to be washed are placed and a hydraulic circuit 3, connectable to an external source of water, for circulating washing liquid through the tub 2.

The hydraulic circuit 3 has one or more racks 4, which are extendably disposed into the tub 2 to be loaded by the user with the dishes to be washed, and one or more spray arms 5 which are associated to corresponding racks 4 to spray the dishes therein arranged with the washing liquid.

The hydraulic circuit 3 further comprises a sump 6 which is arranged in the lower section of the tub 2 to collect the washing liquid that has been sprayed on the dishes during the different phases of a washing cycle, recirculation ducts 7 and a recirculation pump 8 for conveying the washing liquid from the sump 6 to the spray arms 5 and a heater 9, as illustrated in Fig. 1.

The dishwasher 1 is programmed to perform one or more washing cycles. In particular it is programmed to perform a washing cycle comprising at least a washing phase, during which heated washing liquid, comprising in particular heated water with detergent added to it, is distributed on the dishes to be washed, and, subsequently, at least a first rinsing phase, during which cleaned water is distributed on the dishes to remove dirt and detergent residuals from their surfaces.

According to the present invention, the dishwasher 1 further comprises a dispensing system 10 activable for introducing a flocculant, i.e. a flocculating agent, into the washing liquid in the hydraulic circuit 3 in order to promote the aggregation of detergent and dirt particles therein contained for the formation of flocs F. More in detail, the flocculant added to the washing liquid causes the detergent colloids, the suspended oils and particles of dirt in the washing liquid to aggregate forming flocs F, improving the sedimentation or filterability of such colloids and particles and hence allowing the removal of detergent and microscopic particles, including bacteria, viruses, algae, protozoa and organic and inorganic particles, that could not be removed by simple filtration.

The dishwasher 1 of the present invention further comprises a control unit 11 controlling the operation of the dispensing system 10 and programmed to activate the dispensing system 10 at least at the end of the washing phase, before the first rinsing phase, in order to introduce a dose of flocculant into the washing liquid that performed the washing phase. The dishwasher 1 also comprises separation means 12 for separating the formed flocs F from the washing liquid in order to render the latter enough clean to perform the subsequent first rinsing phase.

Therefore the dishwasher 1 according to the present invention allows to reutilize the same water that has been heated and used during the main washing phase to perform the first rinsing phase. This ensures an optimization in water and energy consumption.

Up to 4 or more liters of water, in fact, can be saved by reutilizing the water used in the washing phase, upon cleaning it, also in the first rinsing phase. Moreover, since the washing cycle comprises also a second rinsing phase performed with heated water before the dishes undergo a possible drying phase, the amount of energy required to perform the whole washing cycle in the dishwasher 1 according to the present invention is lower than the amount of energy required to perform a traditional washing cycle wherein the first rinsing phase is performed with a fresh intake of water.

During the first rinsing phase, in fact, performed with the recycled heated water of the washing phase, the tub 2 and the dishes therein arranged are not cooled down so that a lower amount of energy is subsequently required to heat up the water for the second rinsing phase, as illustrated in Figure 2.

According to an embodiment, the control unit 11 is programmed for controlling both the functioning of the dishwasher 1, i.e. the performance of the different phases of the washing cycles, and the operation of the dispensing system 10.

In an embodiment, the dispensing system 10 of the dishwasher 1 is designed to dispense a flocculant in the liquid or in the solid form and it comprises a reservoir 13 which is distinct from the detergent reservoir. The dedicated reservoir 13 for the flocculant prevents dispensing the flocculant together with the detergent, thus allowing to introduce the flocculant into the hydraulic circuit 3 only at the desired stages, such as at the end of the washing phase as above specified.

In an embodiment, the flocculant reservoir 13 is accommodated in the bottom part of the tub 2, in a position easily reachable by the user in order to fill it with one or more doses of flocculant, such as for instance the position of the salt reservoir generally provided in the dishwashers.

In a different embodiment, the flocculant reservoir 13 is accommodated on one of the lateral walls of the dishwasher 1 delimiting the tub 2 or on the frontal door of the dishwasher 1, for instance close to detergent reservoir.

According to a further embodiment, the reservoir 13 is designed to contain various doses of flocculant, so that the user is not requested to provide the dishwasher with one or more doses of flocculant at each new washing cycle.

In an embodiment, the dispensing system 10, designed to dispense a flocculant in the liquid form therein comprising also a gel form, further comprises injection means (not illustrated) for injecting the selected dose of flocculant into the hydraulic circuit 3.

In another embodiment, the dispensing system 10, designed to dispense a flocculant in the solid form therein comprising also a powder form, further comprises releasing means (not illustrated) for releasing the selected dose of flocculant into the hydraulic circuit 3.

In a version of this embodiment the dispensing system 10 comprises also mixing means (not illustrated) for mixing the flocculant with the washing liquid. In order to ensure an optimal removal of the detergent, oils and dirt particles present in the washing liquid that performed the washing phase, it is in fact preferable that the flocculant is thoroughly mixed with the washing liquid.

According to an embodiment, the dishwasher 1 comprises a turbidity sensor (not illustrated) in order to measure the turbidity of the washing liquid at the end of the washing phase, and the control unit 11 is programmed to determine the amount of flocculant that should be added to the washing liquid depending on the sensed turbidity of the latter and to control the operation of the dispensing system 10 accordingly.

In an embodiment, the separation means 12 comprises a filter.

More in detail, in a version of this embodiment the filter of the separation means 12 is the same filter normally used in the known dishwashers for filtering the washing liquid recirculating in the hydraulic circuit 3 during the performance of the different phases of the washing cycle, which is arranged in the sump 6. This filter is usually a microfilter.

In a different version of this embodiment, the filter of the separation means 12 is a cyclonic filter. In particular the cyclonic filter may replace in the dishwasher 1 according to the present invention the filter normally used in the known dishwashers for filtering the washing liquid recirculating in the hydraulic circuit 3 and be arranged in the sump 6.

In a further version of this embodiment, the filter of the separation means 12 is a centrifugal separator. In particular the centrifugal separator may replace in the dishwasher 1 according to the present invention the filter normally used in the known dishwashers for filtering the washing liquid recirculating in the hydraulic circuit 3 and be arranged in the sump 6 or may be an additional filter.

In particular, the usage of a cyclonic filter or of a centrifugal separator is preferred with respect to the traditional filter, since they allow an easier and more complete removal also of oils present in the washing liquid.

In a different embodiment, the separation means 12 comprises a sedimentation receptacle. According to this embodiment, in order to separate the flocs F from the water, the fact that the flocs F have a different density with respect to the water and hence tend either to deposit on the bottom of the sedimentation receptacle or to float near the surface of the water is exploited. The sedimentation receptacle in an embodiment corresponds to the sump 6. In particular the sedimentation receptacle is designed to be connected to the drain duct 14 at its bottom or upper part depending on the expected density of the flocs F.

According to an embodiment, the dishwasher 1 further comprises ultraviolet light emitting means (not illustrated) for irradiating with ultraviolet light the washing liquid circulating in the hydraulic circuit 3 during at least a disinfection phase. In a version of this embodiment, the ultraviolet light emitting means are arranged on the recirculation ducts 7 that lead to the spray arms 5. The ultraviolet light emitting means are provided in order to achieve a cleaner water, by enhancing the microbiological disinfection.

In an embodiment, the dishwasher 1 according to the present invention is programmed to perform in a washing cycle, beside the washing and rinsing phases, at least a pre-washing phase, preceding the washing phase, and the control unit 11 is further programmed to activate the dispensing system 10 at the end of the pre-washing phase, before the washing phase, in order to introduce a dose of flocculant into the washing liquid that performed the pre-washing phase. This allows to reutilize the water that has been used during the pre-washing phase, so that part of the water required during the washing phase can be saved by using the cleaned water previously used during the pre-washing phase, as illustrated in Figure 2.

In this manner the water consumption of the dishwasher 1 during such washing cycle is further reduced.

It is an object of the present invention also a washing cycle for a dishwasher 1 as above described. The washing cycle comprises a washing phase during which heated washing liquid, comprising in particular heated water with detergent added to it, is recirculating in the hydraulic circuit 3 and repeatedly distributed on the dishes arranged in the tub 2, in particular on the racks 4.

The washing cycle comprises hence a first rinsing phase, subsequent the washing phase, during which cleaned water is distributed on the dishes in order to rinse them by removing dirt and detergent residuals deposited on their surfaces.

According to the present invention, the washing cycle further comprises a main dirt removing phase, following the washing phase and preceding the first rinsing phase, during which a flocculant is introduced into the washing liquid circulating in the hydraulic circuit 3, in order to promote the aggregation of detergent, oil and dirt colloids and particles therein contained for the formation of flocs F, and during which the formed flocs F are separated from the washing liquid by separation means 12 for obtaining the cleaned water to be used in the first rinsing phase. More clearly the main dirt removing phase comprises an introduction step of the flocculant in the washing liquid and a subsequent separation step for removing the flocs F thus formed in the washing liquid and obtain cleaned water, i.e. water enough clean to perform a first rinsing phase.

In particular, according to a version of the washing cycle, if the filter of the separation means 12 of the dishwasher 1 is the same filter used for filtering the washing liquid recirculating in the hydraulic circuit 3 during the performance of the different phases of the washing cycle, in order to favor the separation of the flocs F from the water, during the main dirt removing phase the recirculation pump 8 may operate with a higher suction force.

In a different version of the washing cycle, if the filter of the separation means 12 of the dishwasher 1 is a cyclonic filter, the latter is operated during the separation step to separate the flocs F and residual oil and detergent suspensions from the water based on a density profile into a concentrate stream and a permeate stream.

In a version of the washing cycle, if the filter of the separation means 12 of the dishwasher 1 is a centrifugal separator, the latter is operated during the separation step to separate the flocs F and residual oil and detergent suspensions from the water by means of centrifugal force.

According to a different version of the washing cycle, if the separation means 12 comprises a sedimentation receptacle, during the main dirt removing phase the washing liquid containing the flocs F, or part of such washing liquid, is kept for a time interval in the sedimentation receptacle to allow the flocs F either to deposit on the bottom of the receptacle or to reach the surface of the liquid and, subsequently, the portion of the washing liquid comprising the flocs F is drawn from the sedimentation receptacle and drained out of the dishwasher 1 through the drain duct 14.

As previously underlined, the first rinsing phase is therefore performed with hot cleaned water, obtained from the heated washing liquid previously used during the washing phase, thus avoiding the tub 2 and the dishes therein arranged to be cooled.

The washing cycle, in fact, according to a preferred embodiment further comprises a second rinsing phase, during which new clean water, drawn from the external source of water and heated by the heater 9, is distributed on the dishes in order to last rinse them. Thanks to the first rinsing phase being performed with the heated cleaned water obtained from the washing liquid of the main washing phase, a lower amount of energy is required in order to heat up the water for the second rinsing phase.

In general the use of strongly positively charged flocculant is preferred, so as to easily attract negatively charged particles to create larger particles, i.e. flocs F.

The flocculant may be based on a single chemical compound having flocculating properties or may be based on a mixture of such compounds.

According to a version of the washing cycle, the flocculant added during the main dirt removing phase is a salt based flocculant and in particular is aluminum potassium sulfate based.

This flocculant has the advantage of being environmental friendly and not harmful for the human health so that it can be safely used. Moreover, the solution obtained introducing aluminum potassium sulfate as flocculant in the washing liquid has a pH range which is close to neutrality, between 6,8 and 7,5, and similar to the pH of the solutions generally used in the washing cycles. The solution having a pH in the above indicated rate is also not aggressive for the dishwasher parts.

In a version of the washing cycle wherein aluminum potassium sulfate is used as flocculant, the amount of flocculant introduced into the washing liquid during the main dirt removing phase is comprised between 30 mg/l and 50 mg/l. This amount has been proven to be sufficient to promote the aggregation of most of the dirt particles and oil and detergent colloids in flocs F to be removed for obtaining a sufficiently cleaned water to perform the first rinsing phase.

According to a version of the washing cycle of the invention, the flocculant is provided in a 50% solution of flocculant in water. This allows to easily dose the correct amount of flocculant and to favor the mixing of the flocculant with the washing liquid.

In a further version the flocculant may comprise, beside aluminum potassium sulfate, cationic polymers, for enhancing the flocculating effect.

In a version, the washing cycle further comprises a disinfection phase, during which the washing liquid is irradiated with ultraviolet light in order to kill or inactivate microorganisms, having a bactericide and germicide effect. More in detail such disinfection phase can be performed contemporarily to the main dirt removing phase or it can follow such phase.

According to a version, the washing cycle of the invention further comprises a pre-washing phase, preceding the washing phase, and a preliminary dirt removing phase, following the pre-washing phase and preceding the washing phase.

More in detail the pre-washing phase is performed by using simple water or by using water with the addition of detergent. Preferably the pre-washing phase is moreover performed without heating the water or washing liquid.

During the preliminary dirt removing phase a flocculant is introduced into the washing liquid that performed the pre-washing phase in the hydraulic circuit 3, in order to promote the aggregation at least of dirt particles therein contained for the formation of flocs F, and the formed flocs F are separated from the washing liquid by separation means 12 for obtaining a cleaned water to be used in the washing phase

In particular, if the pre-washing phase is performed adding detergent to the water, in the preliminary dirt removing phase the flocculant promotes also the removal of detergent colloids, in a manner completely similar to the main dirt removing phase.

More in detail, a further amount of water and detergent are preferably added to the cleaned water obtained from the preliminary dirt removing phase in order to obtain the washing liquid to be used in the washing phase. Moreover, in order to perform the washing phase, the washing liquid is previously heated.

The preliminary dirt removing phase can be performed in a manner completely similar to the main dirt removing phase, therefore all the technical details previously specified for the main dirt removing phase are referable, mutatis mutandis, also to the preliminary dirt removing phase.

With the dishwasher 1 and the washing cycle of the present invention, significant amounts of water and energy can be saved without however affecting the cleaning performances of the dishwasher 1.

Claims

A dishwasher (1) programmed to perform at least a washing phase and, subsequently, at least a first rinsing phase and comprising:

- a tub (2) in which the dishes to be washed are placed;

- a hydraulic circuit (3) for circulating a washing liquid through the tub (2),

characterized in that it further comprises:

- a dispensing system (10) activable for introducing a flocculant into the washing liquid in the hydraulic circuit (3) in order to promote the aggregation of detergent and dirt particles therein contained for the formation of flocs (F);

- a control unit (11) controlling the operation of the dispensing system (10) and programmed to activate the dispensing system (10) at least at the end of the washing phase, before the first rinsing phase, in order to introduce a dose of flocculant into the washing liquid that performed the washing phase; and

- separation means (12) for separating the formed flocs (F) from the washing liquid in order to render the latter enough clean to perform the subsequent first rinsing phase.
The dishwasher (1) according to claim 1, characterized in that the dispensing system (10) is designed to dispense a flocculant in the liquid or in the solid form and it comprises a reservoir (13) which is distinct from the detergent reservoir.
The dishwasher (1) according to claim 1 or 2, characterized in that the dispensing system (10) is designed to dispense a flocculant in the solid form and the dishwasher (1) comprises mixing means for mixing the flocculant with the washing liquid.
The dishwasher (1) according to any of the preceding claims, characterized in that the separation means (12) comprises a filter and, in particular, a centrifugal separator, a cyclonic filter or a microfilter.
The dishwasher (1) according to any one of claims 1 to 3, characterized in that the separation means (12) comprises a sedimentation receptacle.
The dishwasher (1) according to any of the preceding claims, characterized in that it further comprises ultraviolet light emitting means for irradiating with ultraviolet light the washing liquid circulating in the hydraulic circuit (3) during at least a disinfection phase.
The dishwasher (1) according to any of the preceding claims, characterized in that it is programmed to perform at least a pre-washing phase, preceding the washing phase, and the control unit (11) is further programmed to activate the dispensing system (10) at the end of the pre-washing phase, before the washing phase, in order to introduce a dose of flocculant into the washing liquid that performed the pre-washing phase.
A washing cycle for a dishwasher (1) according to any of the preceding claims, comprising:

- a washing phase during which heated washing liquid is recirculating in the hydraulic circuit (3) and repeatedly distributed on the dishes in the tub (2);

- a first rinsing phase, subsequent the washing phase, during which cleaned water is recirculating in the hydraulic circuit (3) and repeatedly distributed on the dishes in order to rinse them by removing dirt and detergent residuals deposited on their surfaces; characterized in that it further comprises:

- a main dirt removing phase, following the washing phase and preceding the first rinsing phase, during which a flocculant is introduced into the washing liquid that performed the washing phase, in order to promote the aggregation of detergent and dirt particles therein contained for the formation of flocs (F), and the formed flocs (F) are separated from the washing liquid by separation means (12) for obtaining the cleaned water to be used in the first rinsing phase.
The washing cycle according to claim 8, characterized in that the flocculant is a salt based flocculant and in particular is aluminum potassium sulfate based.
The washing cycle according to claim 9, characterized in that the amount of flocculant introduced into the washing liquid during the dirt removing phase is comprised between 30 mg/l and 50 mg/l.
The washing cycle according to any of the claims from 8 to 10, characterized in that the flocculant is provided in a 50% solution in water.
The washing cycle according to any of the claims from 8 to 11, characterized in that it further comprises a disinfection phase, during which the washing liquid is irradiated with ultraviolet light.
The washing cycle according to any of the claims from 8 to 12, characterized in that it further comprises a pre-washing phase, preceding the washing phase, and a preliminary dirt removing phase, following the pre-washing phase and preceding the washing phase, during which a flocculant is introduced into the washing liquid in the hydraulic circuit (3) that performed the pre-washing phase, in order to promote the aggregation at least of dirt particles therein contained for the formation of flocs (F), and the formed flocs (F) are separated from the washing liquid by separation means (12) for obtaining a cleaned water to be used in the washing phase.