EP2497404A1

EP2497404A1 - Cleaning cycle for diswasher with device for recycling the rinse water

Info

Publication number: EP2497404A1
Application number: EP11425059A
Authority: EP
Inventors: Andrea Ambrosi
Original assignee: Bonferraro SpA
Current assignee: Bonferraro SpA
Priority date: 2011-03-10
Filing date: 2011-03-10
Publication date: 2012-09-12

Abstract

A cleaning cycle for a dishwasher comprising a wash tank with a collecting sump at the bottom and a wash pump (1) that draws the water from the collecting sump and sends it to a storage reservoir (3) provided with valve means suitable to prevent the water from flowing back to the wash tank and with a vent duct (10) connected to the wash tank, comprises the steps of:
a) arranging in the dishwasher a suitable dose of detergent;
b) opening the valve means of the storage reservoir (3);
c) starting the wash pump (1) while loading an amount of water suitable to completely fill the storage reservoir (3), until the water overflows in the wash tank through the vent duct (10), and to allow its continuous operation without cavitation;
d) stopping the wash pump (1), after a preset period of time, and starting the drain pump;
e) stopping the drain pump, upon complete draining of the water, and starting the wash pump (1) while loading an amount of water suitable to completely fill the storage reservoir (3), until the water overflows in the wash tank through the vent duct (10), and to allow its continuous operation without cavitation;
f) stopping the wash pump (1), after a preset period of time, and starting the drain pump;
g) stopping the drain pump upon complete draining of the water.

Description

The present invention relates to dishwashers, and in particular to a cleaning cycle for a dishwasher provided with a device for recycling the rinse water and/or the wash water.
It is known that in a dishwasher the normal operating cycle substantially consists of the pre-wash, wash, intermediate rinse, final rinse and drying phases. The initial pre-wash phase is useful to remove the largest residues from the dishes and the water used in said phase is then drained and replaced with clean water for the subsequent wash phase.
In order to reduce the amount of water used in the operating cycle of a dishwasher it is already known to recycle the water of the last rinse of the previous cycle for the pre-wash phase of the following cycle. This recycling is achieved by storing the rinse water in a specific reservoir that is connected to the collecting sump of the wash tank through a relevant hydraulic system with pipes and valves, such that the water can be introduced in the reservoir after the final rinse phase and returned to the tank at the beginning of the following cycle.
Examples of dishwashers provided with such a rinse water recycling system are found in US 2007-0277854A1 and DE 4243605A1 , that disclose hydraulic connecting systems between the storage reservoir and the wash tank in which there is provided a specific valve that closes and opens the access to the reservoir or a two-way valve that directs the rinse water towards the reservoir or towards the drain pipe.
Regardless of the type of hydraulic system that is employed, it is clear that the water stored in the reservoir is not perfectly clean but contains dirt residues that tend to deposit at the reservoir bottom since the water may stay in the reservoir for several hours or even days before being re-used in the following cycle.
This implies a high risk, over time, of clogging of the hydraulic connection between the reservoir and the wash tank, which results in problems in loading the water in the storage reservoir and even more in the gravity outflow towards the wash tank of the water previously loaded in the reservoir. As a consequence, the water recycled in the pre-wash phase may be insufficient and the machine is therefore forced to load network water to achieve a correct operation of the wash pump, thus reducing the water saving.
It should be noted that in prior art dishwashers there is sometimes provided a specific machine cleaning cycle that uses the normal detergent used for cleaning the dishes or a specific detergent (so called "dishwasher cleaner"). The indication of the need to perform the cleaning cycle is provided to the user by means of a visual display on the control panel or simply by stating in the instruction manual the maximum time interval that must occur between the cleaning cycles.
In any case, said cleaning cycle provides the empty operation of the dishwasher with the load of the same amount of water used in the normal operating cycle and without recycling the rinse and/or wash water. Therefore the cleaning cycle affects only the parts usually contacted by the water in the normal operating cycle such as the wash tank, wash and drain pumps, load and drain pipes but not the rinse water storage reservoir that thus keeps accumulating dirt.
Therefore the object of the present invention is to provide a cleaning cycle, for a dishwasher that performs the water recycling function, which overcomes the above-mentioned drawbacks. This object is achieved by means of a cycle that provides also the opening of the hydraulic connection towards the storage reservoir as well as the loading of an amount of water sufficient to guarantee the correct operation of the wash pump without cavitation even when said reservoir is full. Other advantageous features of the present cleaning cycle for dishwasher are disclosed in the dependent claims.
The main advantage of this cleaning cycle resides in the fact that by loading the water also in the storage reservoir without having this cause the cavitation of the wash pump it is possible to remove the dirt residues from said reservoir so as to achieve a complete and accurate cleaning of the machine.
This assures the full and correct operation of the water recycling circuit so as to guarantee the maximum water saving in the following cycles.
These and other advantages and characteristics of the cleaning cycle for dishwasher according to the present invention will be clear to those skilled in the art from the following detailed description of an embodiment thereof, with reference to the annexed drawings wherein:

Fig.1 is a diagrammatic rear perspective view of a dishwasher, without the external casing, illustrating the position, shape and extension of the reservoir formed in the dishwasher side and its connection to the wash pump; and
Fig.2 is an enlarged view of detail A of Fig.1.

The figures above illustrate in particular a dishwasher as disclosed in the European patent application no. 11425017.8 in the name of the same applicant but it is clear that what is being said hereafter also applies to a dishwasher with a water recycling circuit that is different from the one shown in these figures.
A dishwasher implementing a cleaning cycle according to the present invention is conventionally provided with a wash pump 1 that draws the water from the collecting sump and sends it, through a pipe 2, towards a storage reservoir 3 extending in the side portion of the dishwasher, between the wash tank and the external casing.
Said reservoir 3 includes an inlet passage 4 separate from an outlet passage 5, each passage being controlled by a respective valve 6 and 7, which converge downwards into the single connection to pipe 2. Reservoir 3 further includes a load duct 8 extending from the inlet passage 4 to the top of reservoir 3.
A flowmeter, e.g. in the form of a turbine 9, is preferably arranged in the load duct 8 to precisely measure the amount of water loaded in reservoir 3 and consequently control the stopping of the wash pump 1. It should be noted that, upon entry of the water, the air present in reservoir 3 is vented through the vent duct 10 connected to the wash tank through collar 11.
The simple and effective operation of the cleaning cycle of the present invention is therefore readily understood in the light of the description given above and can be summarized in the following steps:

a) arranging in the dishwasher a suitable dose of detergent, be it specific for the cleaning cycle or not;
b) opening at least one between the inlet valve 6 and the outlet valve 7, preferably both;
c) starting the wash pump 1 while loading an amount of water suitable to completely fill the storage reservoir 3, until the water overflows in the wash tank through the vent duct 10 and collar 11, and to allow the continuous operation of the wash pump 1 without cavitation;
d) stopping the wash pump 1, after a preset period of time, and starting the drain pump possibly upon opening of the outlet valve 7 if the latter was not opened in step b);
e) stopping the drain pump, upon complete draining of the water, and starting the wash pump 1 while loading an amount of water suitable to completely fill the storage reservoir 3, until the water overflows in the wash tank through the vent duct 10 and collar 11, and to allow the continuous operation of the wash pump 1 without cavitation;
f) stopping the wash pump 1, after a preset period of time, and starting the drain pump;
g) stopping the drain pump, upon complete draining of the water, and closing the inlet valve 6 and/or the outlet valve 7, said closure(s) being possibly postponed to the beginning of the following operating cycle.

It should be noted that these steps of the cleaning cycle according to the present invention are practically all different from the steps of a similar prior art cleaning cycle for the same dishwasher in that:

in step a) the arranged dose of detergent must properly take into account the greater amount of water that will be loaded in the machine in order to obtain a washing liquor with a suitable concentration of detergent;
step b) is not present in prior art cleaning cycles;
step c) provides the loading of a significantly greater amount of water;
step d) provides the outflow of water from the storage reservoir 3 and the possible opening of the outlet valve 7;
step e) provides the loading of a significantly greater amount of water;
step f) provides the outflow of water from the storage reservoir 3; and
step g) provides the possible closing of the inlet valve 6 and/or of the outlet valve 7.

It should also be noted that since valves 6, 7 are usually driven by thermoactuators that must not exceed given operating times, it is possible that the flow of water through reservoir 3 is interrupted and restored during the cleaning cycle in order to allow the closing and re-opening of valves 6, 7 so as to comply with said operating times. This does not affect the cleaning effectiveness in that, in designing the cycle, the correct valve operating times are obviously taken into consideration so as to obtain a sufficient duration of the wash and rinse steps of reservoir 3.
It is therefore clear that the above-described and illustrated embodiment of the cleaning cycle according to the invention is just an example susceptible of various modifications. In particular, in case reservoir 3 has a single inlet/outlet valve this will remain always open between steps b) and f), not considering the thermoactuator limitations mentioned in the previous paragraph.
Finally, by properly raising the water temperature in the rinse step e) and maintaining it high for a suitable time it is possible to achieve the sanitization of the whole hydraulic circuit of the dishwasher, including reservoir 3, by reaching a sufficient amount of HUE (Heat Unit Equivalent) as defined for example in the US standard NSF/ANSI 3-2007.

Claims

Cleaning cycle for a dishwasher comprising a wash tank with a collecting sump at the bottom and a wash pump (1) that draws the water from said collecting sump and sends it to a storage reservoir (3) provided with valve means suitable to prevent the water from flowing back to said wash tank and with a vent duct (10) connected to the wash tank, said cleaning cycle comprising the steps of:
a) arranging in the dishwasher a suitable dose of detergent;

b) starting the wash pump (1) while loading an amount of water suitable to allow its continuous operation without cavitation;

c) stopping the wash pump (1), after a preset period of time, and starting the drain pump;

d) stopping the drain pump, upon complete draining of the water, and starting the wash pump (1) while loading an amount of water suitable to allow its continuous operation without cavitation;

e) stopping the wash pump (1), after a preset period of time, and starting the drain pump;

f) stopping the drain pump upon complete draining of the water,
characterized in that between steps a) and b) there is provided a further step a') of opening the valve means of said storage reservoir (3), and in that in steps b) and d) the water load is sufficient to completely fill the storage reservoir (3) until the water overflows in the wash tank through the vent duct (10).
Cleaning cycle for a dishwasher according to claim 1, characterized in that it includes a further step g) of closing the valve means of the storage reservoir (3).
Cleaning cycle for a dishwasher according to claim 1 or 2, characterized in that in case the valve means of the storage reservoir (3) include an inlet valve (6) and an outlet valve (7), step a') may consist in the opening of just one of said valves (6, 7).
Cleaning cycle for a dishwasher according to claim 3, characterized in that it includes a further step b') of opening the outlet valve (7) in case step a') consists in the opening of the inlet valve (6) only.
Cleaning cycle for a dishwasher according to any of the preceding claims, characterized in that in case the valve means of the storage reservoir (3) are driven by thermoactuators that must not exceed given operating times, it includes repeated steps of closing and re-opening of said valve means so as to comply with said operating times.
Cleaning cycle for a dishwasher according to any of the preceding claims, characterized in that in step d) the water temperature is raised and maintained high for a time suitable to achieve the sanitization of the whole hydraulic circuit of the dishwasher by reaching a sufficient amount of HUE (Heat Unit Equivalent).