WO2009023466A1

WO2009023466A1 - Dishwasher and method for cleaning items to be washed with such a diswasher

Info

Publication number: WO2009023466A1
Application number: PCT/US2008/072189
Authority: WO
Inventors: Harry Braun; Harald Disch; Markus Heidt; Klaus Padtberg
Original assignee: Premark FEG LLC
Current assignee: Premark FEG LLC
Priority date: 2007-08-11
Filing date: 2008-08-05
Publication date: 2009-02-19
Anticipated expiration: 2010-02-11
Also published as: DE102007037934A1

Abstract

Method and dishwasher for cleaning items to be washed. The method and the dishwasher are designed in such a way that a final-rinse phase with unheated final-rinse liquid is followed by a steam phase in which steam is introduced into a treatment chamber (2) for items being washed above a tank (4) into which liquid can flow down from the treatment chamber (2) for items being washed due to the force of gravity.

Description

DISHWASHER AND METHOD FOR CLEANING ITEMS. TO BE WASHED WITH SUCH A DISHWASHER

The invention relates to a dishwasher or to a method for cleaning items to be washed.

In particular, the invention relates to a method for cleaning items to be washed in a dishwasher, in particular a commercial dishwasher, which is in the form of a batch dishwasher. The invention also relates to a dishwasher, in particular a commercial dishwasher, in the form of a batch dishwasher.

Batch dishwashers are dishwashers which can be manually loaded and unloaded. Batch dishwashers (also called box-type dishwashers) can be hood-type dishwashers or front loader dishwashers. Front loader dishwashers can be under-counter machines or top- counter machines.

Examples of items to be washed are plates, cups, pots, trays, knives, forks, spoons, glasses and other kitchen utensils.

WO2006/037447 Al discloses a dishwasher in the form of a batch dishwasher in which successive method steps are run through: a wash phase, in which wash liquid is sprayed into a treatment chamber from a tank by means of a wash pump through a wash line system and can flow back into the tank from the treatment chamber due to the force of gravity; a final-rinse phase, in which heated fresh water as final-rinse liquid is sprayed into the treatment chamber from a fresh-water feed line by means of a final-rinse pump through a final-rinse line system and can flow into the tank from the treatment chamber due to the force of gravity; a steam phase, in which steam from heated fresh water is generated by means of a steam generator from a fresh-water feed line and is conducted into the treatment chamber through the final-rinse line system. Provision is optionally made for items which have been washed to be dried after the steam phase by air being blown in or to be cooled by letting in water. A water heater (booster) can alternatively be used to heat up the fresh water for final rinsing or for steam generation.

EP 1 738 677 A2 discloses a domestic dishwasher which is designed for the following procedure: a wash phase, during which wash liquid is sprayed into a washing chamber, which is designed to accommodate items to be washed, from a sump by means of a pump via spray nozzles. Wash liquid is then pumped away and the sump is filled with fresh water which is then conveyed from the same pump as the wash liquid previously to the same spray nozzles as the wash liquid previously. The junction of the sump to the pump contains a heater for heating the wash liquid, it being possible for the final-rinse liquid to be heated or left unheated during the final-rinse phase. The final-rinse phase is followed by a steam phase in which fresh water from the sump is evaporated by means of the heater and is conducted into the treatment chamber via the said spray nozzles. The steam phase may be followed by a drying phase in which the heated items which have been washed dry.

In order to clean items to be washed (wash ware), commercial dishwashers require water, detergent, final-rinse aid and power.

A commercial dishwasher usually has two water circuits which are completely separate from one another. These two water circuits are a water circuit which is responsible for washing and through which used water from the wash tank flows, and a fresh-water circuit which is responsible for final rinsing and uses fresh water from a boiler.

The main object of final rinsing is to remove wash-liquid residues which are found on the items being washed. The final-rinse liquid (pure fresh water or fresh water mixed with final-rinse aid) which is sprayed during the final-rinse phase flows into the wash tank and serves to regenerate the wash liquid.

Before new final-rinse liquid is conducted into the wash tank, the same quantity of wash liquid is pumped out of the wash tank.

The object to be achieved by the invention is to provide a way of reducing the quantity of fresh water required for cleaning items to be washed, without cleaning of the items to be washed being adversely affected.

The invention achieves this object by means of a method for cleaning items to be washed in a dishwasher, in particular in a commercial dishwasher, which is in the form of a batch dishwasher, comprising successive program-controlled method steps: a wash phase, in which wash liquid is sprayed into a treatment chamber from a tank by means of a wash pump through a wash line system and can flow back into the tank from the treatment chamber due to the force of gravity; a final-rinse phase, in which fresh water as final-rinse liquid is sprayed into the treatment chamber from a fresh-water supply device by means of a final-rinse pump through a final-rinse line system and can flow into the tank from the treatment chamber due to the force of gravity; a steam phase, in which steam is generated by means of a steam generator, which is connected to a fresh-water feed line, and is conducted into the treatment chamber; characterized in that unheated final-rinse liquid is sprayed into treatment chamber during the final-rinse phase, and in that the steam is introduced into the treatment chamber at a point which is higher than the tank via a steam line, which is separate from the wash line system and from the final-rinse line system, during the steam phase.

A draining phase is preferably executed for a defined time period in a program-controlled manner following the steam phase, during which time period condensed steam can drain into the tank, before the end of the program is reached.

Final-rinse aid can be added to the fresh water which is used for the final-rinse phase in a metered fashion.

Detergent can be added to the wash liquid in a metered fashion.

The invention also achieves the said object by means of a dishwasher for executing the abovementioned method, in particular a commercial dishwasher, in the form of a batch dishwasher, comprising a program-control device for executing at least one cleaning program; a treatment chamber into which items to be washed can be manually inserted and from which items which have been washed can be manually removed; a tank into which liquid can flow down from the treatment chamber due to the force of gravity; a wash system comprising a wash pump and a wash line system for conveying wash liquid into the treatment chamber from the tank through wash nozzles during a wash phase; a final-rinse system comprising a final-rinse pump and a final-rinse line system for conveying final- rinse liquid into the treatment chamber from a fresh-water supply device through final-rinse nozzles during a final-rinse phase; a steam generator, which is connected to a fresh-water feed line, for generating steam and conducting the steam into the treatment chamber during a steam phase; with the program-control device being designed in such a way that first the wash phase, then the final-rinse phase and thereafter the steam phase are executed; characterized in that the program-control device and the final-rinse system controlled by it are designed to spray unheated final-rinse liquid into the treatment chamber during the final-rinse phase, and in that a steam outlet of the steam generator is connected to the treatment chamber at a point which is higher than the tank via a steam line which is separate from the final-rinse line system and from the wash line system.

The invention includes a steam phase in which steam from fresh water is used to remove residual wash liquid, in particular wash liquor, from the surfaces of items being washed. As a result, the total water consumption per cleaning cycle can be reduced, together with a simultaneous reduction in power and chemical costs.

Tests have shown that steam which condenses on the surfaces of dishes has very good rinsing-off effects. Uniformly distributed steam has an advantage over conventional final rinsing with fresh water primarily in shadow zones of the items being washed (dish surfaces which cannot be directly reached by the spray jet). Steam reaches every dish surface within the treatment space substantially in equal parts, irrespective of the position and the orientation of the dish surface.

Restrictions for the use of steam as a rinsing medium are dish surfaces which, on account of their geometric shape, prevent liquid from flowing off due to the force of gravity, for example small bowls or glasses with depressions in the base.

This restriction means that a steam cycle alone is not sufficient to achieve a good cleaning result, but only in conjunction with additional final rinsing with fresh water in which the quantity of fresh water can be reduced compared to conventional dishwashers.

The invention is described below using a preferred embodiment with reference to the attached drawing, in which

Fig. 1 schematically shows a dishwasher, in particular a commercial dishwasher, in the form of a batch dishwasher according to the invention.

The dishwasher according to the invention contains a treatment chamber 2 for cleaning items (not illustrated) to be washed, beneath which treatment chamber a tank 4 which is covered at the top by a screen 3 is located and into which liquid can flow back from the cleaning chamber 2 due to the force of gravity. The tank 4 contains wash liquid 6, which is usually water, to which detergent can optionally be automatically supplied by a detergent- metering apparatus (not shown). The wash liquid can be conveyed to wash nozzles 12 and 14 from a wash pump 8 via a wash line system 10 and be sprayed through these wash nozzles in the treatment chamber 2 onto the items to be cleaned. The sprayed wash liquid flows back into the tank 4. A discharge line 18 with a discharge pump 20 can be connected to the lower end 16 of the tank 4 for the purpose of emptying the tank 4.

The intake end of a final-rinse pump 22 is connected to a fresh-water source, for example to a fresh-water feed line or to a fresh-water container 24, and the pressure end of the said final-rinse pump is connected to a final-rinse line system 26 for conveying unheated fresh water as final-rinse liquid to final-rinse nozzles 32 and 34, which are arranged in the treatment chamber 2, in order to spray the unheated fresh water in the treatment chamber 2 onto the items to be washed.

The wash nozzles 12, 14 and the final-rinse nozzles 32, 34 are each preferably arranged above and below the region for the items being washed and are directed towards the region for the items being washed of the treatment chamber 2. The wash nozzles 12, 14 and/or the final-rinse nozzles 32, 34 could instead be arranged at the bottom and at the top or only at the top or only at the bottom, or instead or in addition also on one side of the treatment chamber 2 and be directed transverse to the treatment chamber 2 into the region for the items being washed.

The container 24 is a constituent part of a return-prevention means 36 which prevents fresh water from being able to return from the intake side of the final -rinse pump 22 into a freshwater feed line 38. The liquid level 40 in the container 24 is automatically kept at a value at which the liquid level 40 has a vertical air gap from the outlet opening 42 in the fresh-water feed line 38. In order to keep the liquid level 40 in the container 24 constant at a predetermined level or in a predetermined level range, it is possible, for example, to provide a level sensor 44. The level sensor 44 provides the option of automatically controlling an electromagnetic valve 46 in the fresh-water feed line 38.

A metering apparatus 50 for final-rinse aid for metering final-rinse aid into the fresh water which serves as final-rinse liquid can be connected to the container 24 or to another point upstream or downstream of the final-rinse pump 22.

A steam generator 52 has a fresh- water inlet 54 and a steam outlet 56. The fresh-water inlet 54 has connected to it a second fresh- water feed line 58 which can contain an electromagnetically operated valve 60 and, between the valve 60 and the steam generator 52, preferably a non-return valve 62 for preventing liquid from flowing back from the steam generator 52 into the second fresh- water feed line 58.

The steam outlet 56 of the steam generator 52 is connected to the treatment space 2 via a steam line 64 at a point 66 above the tank 4, in order to introduce steam into the said treatment space. The outlet opening 68 in the steam line 64 is preferably located between the upper nozzles 12, 32 and the lower nozzles 14, 34 of the wash line system 10 or the final-rinse line system 26. However, other positions are also possible. The steam generator contains a heater 70. Furthermore, the steam generator can contain a level sensor 72 which controls the valve 60 in the second fresh- water feed line 58. The two fresh-water feed lines 38 and 58 can be connected to a common liquid feed line 78 upstream of their valves 46 and, respectively, 60. The common liquid feed line 78 can contain a water softener 80.

The steam generator 52 can be provided with a discharge opening 81 and a discharge valve

82.

According to another embodiment of the invention, the intake end 83 of the final-rinse pump 22 can be connected to a water outlet of the steam generator 52 instead of to the return-prevention means 36, in order to alternatively supply the fresh- water line system 26 with non-heated or heated fresh water as final-rinse liquid from the steam generator 52.

A program-control device 74 for controlling at least one cleaning program is designed in such a way and is connected to the controllable elements of the dishwasher, for example the valves 46, 60, the level sensors 44 and 72 and a heater control circuit for controlling the heater 70 of the steam generator 52, in such a way that the dishwasher can execute a cleaning method (cleaning cycle) with successive steps (phases):

1. a wash phase, in which wash liquid is sprayed into the treatment chamber 2 from the tank 4 by means of the wash pump 8 through the wash line system 10 and then can flow back into the tank 4 from the treatment chamber 2 due to the force of gravity;

2. a final-rinse phase, in which unheated fresh water as final-rinse liquid is sprayed into the treatment chamber 2 by means of the final-rinse pump 22 through the final- rinse line system 26 and then flows into the tank 4 from the treatment chamber 2 due to the force of gravity;

3 a steam phase, which follows the final-rinse phase, in which steam is introduced into the treatment chamber 2 via the steam line 64 which is separate from the wash line system 10 and separate from the final-rinse line system 26.

Furthermore, the program controller 74 is preferably designed in such a way that a draining phase is executed for a specific time period in a program-controlled manner following the steam phase, during which time period condensed steam can drain from the treatment chamber 2 into the tank 4, before the end of the program is reached.

Claims

1. Method for cleaning items to be washed in a dishwasher, in particular in a commercial dishwasher, which is in the form of a batch dishwasher, comprising the successive program-controlled method steps:

1.1 a wash phase, in which wash liquid (6) is sprayed into a treatment chamber (2) from a tank (4) by means of a wash pump (8) through a wash line system (10) and can flow back into the tank (4) from the treatment chamber due to the force of gravity;

1.2 a final-rinse phase, in which fresh water as final-rinse liquid is sprayed into the treatment chamber (2) from a fresh- water supply device (36, 38) by means of a final-rinse pump (22) through a final-rinse line system (26) and can flow into the tank (4) from the treatment chamber due to the force of gravity;

1.3 a steam phase, in which steam is generated by means of a steam generator (52), which is connected to a fresh-water feed line (58), and is conducted into the treatment chamber (2); characterized

1.4 in that unheated final-rinse liquid is sprayed into treatment chamber (2) during the final-rinse phase, and

1.5 in that the steam is introduced into the treatment chamber (2) at a point which is higher than the tank (4) via a steam line (64), which is separate from the wash line system (10) and from the final-rinse line system (26), during the steam phase.

2. Method according to Claim 1, characterized in that a draining phase is executed for a defined time period in a program-controlled manner following the steam phase, during which time period steam which has condensed in the treatment space (2) can drain into the tank (4), before the end of the program is reached.

3. Method according to Claim 1 or 2, characterized in that the unheated final-rinse liquid used during the final-rinse phase is fresh water from the fresh-water supply device (36, 38) and final-rinse aid which is added to the fresh water in a metered fashion.

4. Dishwasher for executing the method according to one of the preceding claims, in particular commercial dishwasher, in the form of a batch dishwasher, comprising a program-control device (74) for executing at least one cleaning program; a treatment chamber (2) into which items to be washed can be manually inserted and from which items which have been washed can be manually removed; a tank (4) into which liquid can flow down from the treatment chamber due to the force of gravity; a wash system (8, 10, 12, 14) comprising a wash pump (8) and a wash line system (10) for conveying wash liquid into the treatment chamber (2) from the tank (4) through wash nozzles (12, 14) during a wash phase; a final-rinse system (32, 34, 22, 26) comprising a final-rinse pump (22) and a final- rinse line system (26) for conveying final-rinse liquid into the treatment chamber (2) from a fresh-water supply device (36, 38) through final-rinse nozzles (32, 34) during a final-rinse phase; a steam generator (52), which is connected to a fresh- water feed line (58), for generating steam and conducting the steam into the treatment chamber (2) during a steam phase; with the program-control device (74) being designed in such a way that first the wash phase, then the final-rinse phase and thereafter the steam phase are executed; characterized in that the program-control device (74) and the final-rinse system (32, 34, 22, 26) controlled by it are designed to spray unheated final-rinse liquid into the treatment chamber (2) during the final-rinse phase, and in that a steam outlet (56) of the steam generator (52) is connected to the treatment chamber (2) at a point (66) which is higher than the tank (4) via a steam line (64) which is separate from the final-rinse line system (26) and from the wash line system (10).

5. Dishwasher according to Claim 4, characterized in that the program-control device (74) is designed to execute a draining phase which follows the steam phase and which lasts for a defined time during which steam which has condensed in the treatment chamber can flow down into the tank (4) after the steam phase, before the end of the program is reached.

6. Dishwasher according to Claim 4 or 5, characterized in that a metering device (50) for final-rinse aid is provided for metering final-rinse aid into the fresh water of the final- rinse liquid.

7. Dishwasher according to one of Claims 4 to 6, characterized in that the fresh-water supply device (36, 38) has a return-prevention means (36), and in that the intake end (83) of the final-rinse pump (22) is connected to a fresh-water feed line (38) via the return- prevention means (36), with the backflow-prevention means (36) being designed to prevent liquid from flowing back into the fresh- water feed line (38) in the direction from the final- rinse pump (22).

8. Dishwasher according to one of Claims 4 to 7, characterized by a water softener (80) for conditioning the fresh water for the final-rinse system (32, 34, 22, 26) and the fresh water for the steam generator (52).