US20140020718A1

US20140020718A1 - Dishwasher with ozone generator

Info

Publication number: US20140020718A1
Application number: US13/859,134
Authority: US
Inventors: Paul E. Beshears, Jr.; Jonathan D. Gephart; Saadat Hussain; Mark M. Senninger; Elliott V. Stowe
Original assignee: Whirlpool Corp
Current assignee: Whirlpool Corp
Priority date: 2012-07-19
Filing date: 2013-04-09
Publication date: 2014-01-23

Abstract

A dishwasher comprises a treating chamber for receiving dishes therein for treatment according to a cycle of operation, at least one sprayer providing a spray of liquid into the treating chamber, and an ozone generator for selectively providing ozone gas to the treating chamber for sanitizing the dishes in the treating chamber during a cycle of operation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 61/673,475, filed Jul. 19, 2012, which is incorporated herein by reference in its entirety.

BACKGROUND

Dishwashers include a treating chamber in which dishes are placed to be treated according to an automatic cycle of operation. Various treating aids, such as detergents, stain removers, rinse aids, odor removers and sanitizing agents may be applied to the dishes during a cycle of operation. One example of a sanitizing agent is ozone, which may be generated in a variety of different ways to provide ozone gas, ozone gas mixed with liquid and/or ozone gas dissolved in liquid to sanitize dishes in the treating chamber and/or surfaces within the dishwasher.

BRIEF SUMMARY

According to an embodiment of the invention, a method of controlling a dishwasher comprises introducing ozone gas into the treating chamber and maintaining the ozone gas in the treating chamber at a sanitizing concentration of 5 ppm or less for a time sufficient to sanitize the dishes.
According to another embodiment of the invention, a dishwasher comprises an ozone circuit, a recirculation circuit and a valve for selectively controlling the flow of liquid through the ozone circuit and the recirculation circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a cross-sectional view of a schematic of a dishwasher according to a first embodiment of the invention.

FIG. 2 is a cross-sectional view of a schematic of a dishwasher according to a second embodiment of the invention.

FIG. 3 is a schematic of a control system that may be used with the dishwasher of FIGS. 2 and 3 according to a third embodiment of the invention.

FIG. 4 is a flowchart illustrating a method of controlling a dishwasher according to a fourth embodiment of the invention.

FIG. 5 is a flowchart illustrating a method of controlling a dishwasher according to a fifth embodiment of the invention.

DETAILED DESCRIPTION

While the embodiments of the invention are illustrated in the context of a dishwasher having a single treating chamber, it is also within the scope of the invention for the embodiments of the invention to be used in a dishwasher having multiple treating chambers. The embodiments of the invention may be used with a dishwasher having a door for selectively closing an opening to the treating chamber, as illustrated in FIG. 1, as well as a dishwasher in which the treating chamber is defined by a drawer, which is slidingly moveable to provide access to the treating chamber.
FIG. 1 is a schematic cross-sectional view of an automatic dishwasher 10 according to an embodiment of the invention, the dishwasher 10 having a cabinet 12 defining an interior. Depending on whether the dishwasher 10 is a stand-alone or built-in, the cabinet 12 may be a chassis/frame with or without panels attached, respectively. The dishwasher 10 shares many features of a conventional automatic dishwasher, which will not be described in detail herein except as necessary for a complete understanding of the invention.
A controller 14 may be located within the cabinet 12 and may be operably coupled with various components of the dishwasher 10 to implement one or more cycles of operation. A control panel or user interface 16 may be provided on the dishwasher 10 and coupled with the controller 14. The user interface 16 may include operational controls such as dials, lights, switches, and displays enabling a user to input commands, such as a cycle of operation, to the controller 14 and receive information.
A tub 18 is located within the cabinet 12 and at least partially defines a treating chamber 20 with an access opening in the form of an open face. A closure, illustrated as a door 22, may be hingedly mounted to the cabinet 12 and may move between an opened position, wherein the user may access the treating chamber 20, and a closed position, as shown in FIG. 1, wherein the door 22 covers or closes the open face of the treating chamber 20. Dish holders in the form of upper and lower racks 24, 26 are located within the treating chamber 20 and receive dishes for treatment. The racks 24, 26 are mounted for slidable movement in and out of the treating chamber 20 for ease of loading and unloading.
As used herein, the term “dish(es)” is intended to be generic to any item, single or plural, that may be treated in the dishwasher 10, including, without limitation; dishes, utensils, plates, pots, bowls, pans, glassware, and silverware. While not shown, additional dish holders, such as a silverware basket on the interior of the door 22 or within the upper or lower racks 24, 26, may also be provided.
A spray system 28 is provided for spraying liquid in the treating chamber 20 and is provided in the form of a first lower spray assembly 30, a second lower spray assembly 32, a mid-level spray assembly 34, and/or an upper spray assembly 36. Upper spray assembly 36, mid-level spray assembly 34 and first lower spray assembly 30 are located, respectively, above the upper rack 24, beneath the upper rack 24, and beneath the lower rack 26 and are illustrated as rotating sprayers or spray arms. The second lower spray assembly 32 is illustrated as being located adjacent the lower rack 26 toward the rear of the treating chamber 20. The second lower spray assembly 32 is illustrated as including a vertically oriented distribution header or spray manifold. Such a spray manifold is set forth in detail in U.S. Pat. No. 7,594,513, issued Sep. 29, 2009, and titled “Multiple Wash Zone Dishwasher,” which is incorporated herein by reference in its entirety. Each of the spray assemblies 30, 34 and 36 may include a first set of openings 31, 35 and 37 through which liquid is emitted.
A liquid recirculation system may be provided for recirculating liquid from the treating chamber 20 to the spray system 28. The recirculation system may include a sump 38 and a pump assembly 40. The sump 38 collects the liquid sprayed in the treating chamber 20 and may be formed by a sloped or recessed portion of a bottom wall 42 of the tub 18. The pump assembly 40 may include both a drain pump 44 and a recirculation pump 46.
The dishwasher 10 may also include a filter assembly 48 in fluid communication with the sump 38 and the pump assembly 40 such that liquid flowing from the sump 38 to the recirculation pump 46 passes through the filter assembly 48. The filter assembly 48 may also be fluidly coupled with a water supply line 50 for receiving fresh water from a water supply source, such as a household water supply. The details of the filter assembly 48 are not germane to the embodiments of the invention.
The liquid recirculation system may also include a liquid supply conduit 52 fluidly coupled with the recirculation pump 46 and a spray system supply conduit 54 for supplying liquid from the filter assembly 48 to the spray system 28. In this manner, liquid may circulate from the sump 38 through the liquid recirculation system to the spray system 28 and back to the sump 38 to define a liquid recirculation circuit or flow path.
The drain pump 44 may draw liquid from the sump 38 and pump the liquid out of the dishwasher 10 to a drain line 56. The recirculation pump 46 may draw liquid from the sump 38 and pump the liquid to the spray system 28 through the liquid supply conduit 52 and the spray system supply conduit 54 to supply liquid into the treating chamber 20 through the spray assemblies 30, 32, 34 and 36. While the pump assembly 40 is illustrated as having separate drain and recirculation pumps 44, 46 in an alternative embodiment, the pump assembly 40 may include a single pump configured to selectively supply liquid to either the spray system 28 or the drain line 56, such as by configuring the pump to rotate in opposite directions, or by providing a suitable valve system. A heating system having a heater 58 may also be located within or near a lower portion of the tub 18 for heating liquid contained therein.
The dishwasher 10 may also be provided with an ozonating system 60 for supplying ozone gas to the treating chamber 20. The ozonating system 60 includes an ozone generator 62 for generating ozone gas and an ozone supply conduit 66 fluidly coupled with the ozone generator 62 for supplying the ozone gas generated by the ozone generator 62 to the treating chamber 20. The ozone supply conduit 66 may be fluidly coupled with the recirculation circuit at a first end and the spray system 28 at a second end such that liquid from the recirculation circuit may flow through the ozone supply conduit 66 to the spray system 28 to define an ozone circuit.
The ozone generator 62 may be coupled with the ozone supply conduit 66 to the treating chamber 20 in any suitable manner. As illustrated, a venturi 68 is used to couple the supply conduit 66 to the treating chamber 20 such that ozone gas generated by the ozone generator 62 is drawn into the liquid flowing through the venturi 68 through a low pressure input of the venturi 68 to form an ozone gas-liquid mixture. However, many other structures and methods may be used to couple the supply conduit 66 to the treating chamber, such as coupling the supply conduit 66 directly to the pump assembly 40. With such a configuration, the ozone gas-liquid mixture can then be supplied to the treating chamber 20 through the spray system 28.
The ozone generator 62 may also be coupled with the venturi 68 through a conduit 91 including a portion 92 extending above a maximum water level 94 in the sump 38 such that liquid in the sump 38 does not flow backwards through the conduit 91 to the ozone generator 62.
As used herein, the term ozone gas-liquid mixture refers to a mixture of ozone gas and a liquid in which some portion of the ozone gas is dissolved in the liquid and the remaining portion of ozone gas is undissolved. The amount of ozone gas dissolved in the liquid is dependent on a variety of characteristics of the system, such as temperature, pressure, pH and concentration of the ozone gas, for example. It will be understood that the application of the ozone gas-liquid mixture to a surface may include the application of a mixture of ozone gas dissolved in water and ozone gas which is not dissolved in water.
The ozone generator 62 may be any suitable type of generator known in the art that generates ozone gas, such as a corona discharge, ultraviolet or cold plasma ozone generator. The ozone generator 62 may be configured to draw in air from the ambient atmosphere in which the dishwasher 10 is located and generate ozone gas from the ambient air. The dishwasher 10 may also optionally include a desiccator 70 having a suitable desiccant for dehumidifying the air supplied to the ozone generator 62.
The dishwasher 10 also includes a valve 76 for selectively coupling the ozone circuit with the recirculation circuit. The valve 76 may be located downstream of the recirculation pump 46 and operably coupled with the controller 14 to selectively supply liquid to either the liquid supply conduit 52 or the ozone supply conduit 66. The valve 76 may be any suitable type of valve, such as a diverter valve. The liquid supply conduit 52 and ozone supply conduit 66 may be fluidly coupled with a suitable valve or manifold 77 for supplying liquid and/or gas flowing through the recirculation circuit or the ozone circuit to the spray system 28.
During a cycle of operation, the recirculation pump 46 may pump liquid from the filter assembly 48 to the spray system 28 for distribution onto dishes in the treating chamber 20 through the spray assemblies 30, 32, 34 and/or 36 during one or more pre-wash, wash and rinse phases of the selected cycle of operation. The controller 14 may control the diverter valve 76 such that liquid pumped from the filter assembly 48 by the recirculation pump 46 passes through the liquid supply conduit 52 to the spray system supply conduit 54 for delivery to the spray assemblies 30, 32, 34 and 36. Liquid supplied through the spray assemblies 30, 34 and 36 may be sprayed into the treating chamber 20 through the respective openings 31, 35 and 37 of the spray assemblies 30, 34 and 36, respectively.
When the selected cycle of operation calls for ozone to be supplied to the treating chamber 20 for sanitizing the surfaces of the treating chamber 20 and/or dishes present within the treating chamber 20, the controller 14 may control the diverter valve 76 to bypass the liquid supply conduit 52 and supply liquid to the ozone supply conduit 66. The controller 14 may also activate the ozone generator 62 to generate ozone gas. As the liquid flows through the ozone supply conduit 66 and the venturi 68, the ozone gas generated by the ozone generator 62 may be drawn into the ozone supply conduit 66 and mixed with the liquid flowing through the ozone supply conduit 66. The mixture of ozone gas and liquid exiting the venturi 68 is supplied to the spray system supply conduit 54 through the ozone supply conduit 66 for delivery to the spray assemblies 30, 32, 34 and 36. In this manner, the ozone gas-liquid mixture may be sprayed into the treating chamber 20 for sanitizing the surfaces and dishes present in the treating chamber 20 in the same manner as described above with respect to the recirculating liquid.
The venturi 68 in the ozone circuit restricts the flow of liquid through the ozone supply conduit 66, reducing the pressure of the liquid flowing through the spray system 28. Thus, if the recirculation pump 46 is operated at the same speed when liquid is selectively supplied to the recirculation circuit and the ozone circuit, the pressure of the liquid sprayed through the spray assemblies 30, 32, 34 and 36 from the ozone circuit will be less than the pressure of the liquid spray through the spray assemblies 30, 32, 34 and 36 from the recirculation circuit. Bypassing the ozone circuit when ozone gas is not being used in the cycle allows the recirculating liquid in the recirculation path to be supplied to the spray system 28 at a pressure which does not affect the wash performance without the need for a higher capacity recirculation pump to compensate for the decrease in pressure that would be caused by the venturi 68.
FIG. 2 illustrates a dishwasher 110, which is similar to the dishwasher 10, except for the configuration of the recirculation circuit and the ozone circuit. Therefore, elements in the dishwasher 110 similar to the dishwasher 10 are numbered with the prefix 100.
As illustrated in FIG. 2, the ozonating system 160 comprise an ozone generator 162 for generating ozone gas that is fluidly coupled with the recirculation circuit through the ozone supply conduit 166 upstream of the recirculation pump 146 between the recirculation pump 146 and the filter assembly 148. The ozone supply conduit 166 may be coupled directly with a pump inlet conduit 190 extending between the filter assembly 148 and recirculation pump 140, as illustrated. Alternatively, the ozone supply conduit 166 may be coupled with the pump inlet conduit 190 indirectly through a valve, for example. The ozone supply conduit 166 may also include a portion 192 which extends above a maximum water level 194 in the sump 138 such that liquid in the sump 138 or pump inlet conduit 190 does not flow backwards through the ozone supply conduit 166 to the ozone generator 162.
During a cycle of operation in which liquid is supplied to the treating chamber 120, the recirculation pump 146 draws liquid from the filter assembly 148 through the pump inlet conduit 190 and supplies the liquid to the spray system 128 through the spray system supply conduit 154. When the ozone generator 162 is activated, ozone gas generated by the ozone generator 162 may be drawn through the ozone supply conduit 166 and into the liquid flowing through the pump inlet conduit 190 by the recirculation pump 146.
FIG. 3 schematically illustrates a control system that may be used to control the operation of the dishwasher 10 and/or 110 described above. The controller 14, 114 may be coupled with the heater 58, 158 for heating the wash liquid during a cycle of operation, the drain pump 44, 144 for draining liquid from the treating chamber 20, 120, the recirculation pump 46, 146 for recirculating liquid during the cycle of operation, the diverter valve 76 for controlling the flow of liquid and gas through the recirculation circuit and ozone circuit, and the ozone generator 62, 162 for controlling the generation of ozone.
The controller 14, 114 may be provided with a memory 78, 178 and a central processing unit (CPU) 80, 180. The memory 78, 178 may be used for storing control software that may be executed by the CPU 80, 180 in completing a cycle of operation using the dishwasher 10, 110 and any additional software. For example, the memory 78, 178 may store one or more pre-programmed cycles of operation that may be selected by a user and completed by the dishwasher 10, 110.
The dishwasher 10, 110 may also include an ozone sensor 81,181 for determining the amount or concentration of ozone gas in the treating chamber 20, 120, which is communicably coupled with the controller 14, 114. The controller 14, 114 may also receive input from one or more additional sensors 82, 182. Non-limiting examples of sensors that may be communicably coupled with the controller 14, 114 include a temperature sensor and turbidity sensor to determine the soil load associated with a selected grouping of dishes, such as the dishes associated with a particular area of the treating chamber.
The controller 14, 114 may also be operably coupled with a closure lock 84, 184 for selectively locking and unlocking the closure 22, 122. The controller 14, 114 may control the closure lock 84, 184 to maintain the closure 22, 122 in an operable condition in which the closure 22, 122 may be used by a user to open and close the access opening to the treating chamber 20, 120, depending on the status of the cycle of operation. Alternatively, the controller 14, 114 may control the closure lock 84, 184 to maintain the closure 22, 122 in an inoperable condition in which the closure 22, 122 may not be opened by a user to prevent access to the treating chamber 20, 120.
Referring now to FIG. 4, a method 200 of operating the dishwasher 10 to supply ozone gas to the treating chamber 20 during a cycle of operation is illustrated. The sequence of steps depicted for this method and the subsequent methods are for illustrative purposes only, and are not meant to limit any of the methods in any way as it is understood that the steps may proceed in a different logical order or additional or intervening steps may be included without detracting from the invention.
The method 200 begins with assuming that a user has loaded the dishwasher 10 with the desired items to be treated and selected a desired cycle of operation at 202. At 204, the controller 14 determines if the selected cycle of operation includes ozone. The determination at 204 may occur at the beginning of the cycle of operation or at some predetermined time in the cycle of operation, such as during a rinse phase, for example.
If the selected cycle of operation does not include ozone, at 206 the controller 14 maintains the diverter valve 76 in a position such that liquid flows through the recirculation circuit and bypasses the ozone circuit throughout the cycle of operation. At 208, the controller 14 controls the dishwasher 10 to complete the cycle of operation without ozone.
If the selected cycle of operation includes ozone, when the cycle of operation reaches the phase in which ozone is used, such as a sanitizing or final rinse phase, the method 200 may include an optional drain at 210 in which liquid that has been circulated through the spray system 28 is drained by the drain pump 44 to the household drain. The controller 14 may control the ozone generator 62 to generate ozone gas at 212. At 214, the controller 14 may control the diverter valve 76 to open the bypass to the ozone circuit such that liquid flowing through the recirculation system is diverted through the venturi 68 and the ozone supply conduit 66. As the liquid flows through the venturi 68, the ozone gas generated by the ozone generator 62 may be drawn into the liquid and the mixture of ozone gas and liquid may be delivered to the spray system 28 through the ozone supply conduit 66. The controller 14 may control the ozone generator 62 and the diverter valve 76 such that the events at 212 and 214 occur simultaneously or sequentially. For example, at 214, the diverter valve 76 may be controlled to open the ozone circuit at some predetermined delay time after the activation of the ozone generator 62 at 212. Alternatively, the ozone generator 62 and diverter valve 76 may be activated simultaneously.
At 216, the recirculation pump 46 may pump liquid from the filter assembly 48 through the venturi 68 to the spray system 28 through the ozone supply conduit 66 for spraying through the spray assemblies 30, 32, 34 and/or 36 to supply the mixture of ozone gas and liquid to the treating chamber 20. Liquid may be pumped through the ozone circuit and ozone gas may be generated by the ozone generator 62 for a predetermined period of time. The predetermined period of time may correspond to a set period of time based on the selected cycle of operation, one or more operating parameters and/or based on sensor input. For example, the predetermined period of time may be based on a selected or sensed soil level. In another example, the predetermined period of time may be based on maintaining a predetermined concentration of ozone gas in the treating chamber 20 for a predetermined period of time.
At 217, the method 200 may include an optional step of maintaining the closure lock 84 in an unlocked state or condition such that the closure 22 remains operable while the concentration of ozone gas in the treating chamber 20 remains below a threshold value. The concentration of ozone gas in the treating chamber 20 may be determined using any suitable sensor or combination of sensors, such as the ozone sensor 81, for example. If the concentration of ozone gas in the treating chamber 20 is above the threshold value, the closure lock 84 may be activated such that the closure 22 is no longer operable by a user to gain access to the treating chamber 20. In addition, or alternatively, the ozone generator 62 may be deactivated to stop the supply of ozone gas to the treating chamber 20 until the concentration decreases below the threshold value.
The threshold value may be any suitable value. In one example, the threshold value may be based on a concentration of ozone gas that is generally considered a safe immediate exposure level for humans. For example, the Centers for Disease Control and Prevention National Institute for Occupational Safety and Health (NIOSH) lists the immediately dangerous to health (IDLH) level for ozone gas at 5 ppm. Thus, according to one embodiment, the concentration of ozone gas inside the treating chamber may be controlled to be 5 ppm or less. An ozone gas concentration of 5 ppm inside the treating chamber results in an ozone gas concentration of less than 5 ppm outside the treating chamber if the door to the dishwasher is opened during the supply of ozone to the treating chamber. Typically, a dishwasher treating chamber has a volume around 0.12 cubic meters. Any room the dishwasher is located in will inherently have a volume larger than 0.12 cubic meters, and typically a much larger volume. Therefore, if the treating chamber is provided with an amount of ozone gas that results in a concentration of 5 ppm within the volume of the treating chamber, the concentration of the ozone gas that may enter the room in which the dishwasher is installed if the door is opened will inherently be less than 5 ppm.
Thus, if the concentration of ozone gas inside the treating chamber 20 is maintained at around 5 ppm or less, it is not necessary to activate the lock 84 and the closure 22 may remain in an operable condition. As used in this context, the term operable condition means that a user can open the closure 22 to access the treating chamber 20 at any point during the supply of ozone gas. Alternatively, it is within the scope of the invention for the lock 84 to be activated during the supply of ozone gas to the treating chamber 20, such that the closure 22 is in an inoperable condition in which a user cannot access the treating chamber 20.
It is also within the scope of the invention for the threshold value for the ozone gas concentration inside the treating chamber 20 to be based on standards set by other regulatory or certification agencies, such as the United States Occupational Safety and Health Administration (OSHA) or Underwriters Laboratory, for example, such that it is not necessary to activate the lock 84 and the closure 22 may remain in an operable condition.
At 218, the controller 14 may activate the heater 58 to heat the treating chamber 20 and any liquid present in the sump 38. At 220, the controller 14 may control the dishwasher 10 to complete the selected cycle of operation.
The optional drain at 210 may be used to provide fresh liquid to the ozone circuit for mixing with the ozone gas to form the ozone gas-liquid mixture. Liquid that has been recirculated over the dishes in the treating chamber 20 may include organic material, such as food and soil particulates, detergents and/or other wash aids that may interact with the ozone gas, thus decreasing the amount of ozone gas delivered to the treating chamber 20. The use of fresh liquid to form the ozone gas-liquid mixture may minimize the amount of ozone gas that breaks down in the liquid prior to spraying in the treating chamber 20.
The heater 58 may be activated at the end of the ozone phase of the cycle or at the end of the cycle of operation to decrease the concentration of ozone gas in the treating chamber 20 when the cycle is complete before the user opens the closure 22.
One example of a cycle of operation that includes ozone is a sanitizing rinse which may be used to sanitize dishes in the treating chamber 20 and/or parts of the dishwasher 10, such as the recirculation system, spray system and surfaces of the treating chamber 20, for example. A sanitizing rinse may be provided as an individual cycle of operation and/or as part of another cycle of operation. For example, the dishwasher 10 may include a wash cycle that includes a sanitizing rinse as a final rinse. The controller 14 may control the diverter valve 76 to control the flow of liquid through the recirculation system, bypassing the ozone circuit, during the normal wash and rinse phases of the wash cycle. At the end of the wash cycle, the controller 14 may activate the ozone generator 62 and control the diverter valve 76 to divert liquid through the ozone circuit such that a mixture of ozone gas and liquid may be supplied to the treating chamber 20 to sanitize the dishes in the treating chamber 20.
Referring now to FIG. 5, a method 300 of operating the dishwasher 110 to use ozone in a cycle of operation is illustrated. While the method 300 is discussed in the context of the dishwasher 110, it will be understood that the method 300 may also be used in a similar manner with the dishwasher 10 or any other dishwasher having a gas ozone generation system. The method 300 may be used alone or in combination with the method 200 of FIG. 4, for example.
The method 300 begins with assuming that the user has loaded the dishwasher 110 and selected a desired cycle of operation that includes the use of ozone. At 302, the controller 114 may control the ozone generator 162 and the recirculation pump 146 to provide a mixture of ozone gas and liquid to the spray system 128 for spraying in the treating chamber 120. The operation of the ozone generator 162 and the recirculation pump 146 may be controlled so as to maintain the concentration of ozone gas within the treating chamber 120 at a predetermined concentration for a predetermined period of time to sanitize the dishes at 304.
For example, the concentration of ozone gas in the treating chamber 120 may be determined using the ozone sensor 181 and the ozone generator 162 and the recirculation pump 146 may be controlled to maintain the concentration of ozone gas in the treating chamber 120 at a predetermined value or within a predetermined concentration range. Alternatively, the amount of ozone gas provided to the treating chamber 120 to maintain a desired concentration may be determined experimentally or empirically based on one or more characteristics, such as the volume of the treating chamber, the selected cycle of operation, parameters of the cycle of operation, such as the water temperature or number of rinses, the volume of liquid used during the sanitizing rinse, and/or the soil level, for example.
The amount of time to maintain the concentration of ozone gas at the predetermined concentration may be determined experimentally or empirically. For example, the log reduction of one or more species of bacteria in a dishwasher under various conditions may be determined experimentally and used to provide a look-up table or control algorithm that may be stored in the controller memory 178. The look-up table or control algorithm may be used by the controller 114 to determine the amount of time to maintain a predetermined concentration of ozone gas based on a variety of conditions, such as structural parameters of the dishwasher (e.g. the volume of the treating chamber), the cycle of operation, parameters of the cycle of operation, such as the water temperature or number of rinses, the volume of liquid used during the sanitizing rinse, and/or the soil level, for example.
At 306, the ozone gas may be provided to the treating chamber 120 at 302 and 304 while the closure 122 remains in an operable condition. In this context, the language operable condition means that a user can open the closure 122 to access the treating chamber 120 at any point during the supply and maintenance of ozone gas at 302 and 304. During 302 and 304, the closure lock 184 remains in an unlocked condition and does not prevent a user from opening the closure 122 to access the treating chamber 120.
As used herein, the term sanitize refers to killing, removing, or otherwise rendering innocuous all or a portion of the microorganisms present on the dishes and/or surfaces within the dishwasher. Non-limiting examples of microorganisms that may be killed/removed/rendered innocuous include bacteria, mold, yeast, fungus and viruses. According to one embodiment, sanitize is defined as achieving at least a 99.999% or 5-log reduction of bacteria. For example, NSF® certifies the ability of residential dishwashers to sanitize according to NSF® International's ANSI 184 standard as achieving a minimum 99.999% or 5-log reduction of bacteria.
Sanitizing is effected by the concentration of ozone gas supplied to the treating chamber and the amount of time of exposure to the ozone gas. Lower concentrations of ozone gas may be able to provide the desired level of sanitization if the ozone gas is provided for a long enough period of time. Alternatively, very high concentrations of ozone gas may be used to provide sanitization in less time.
Applicants have found that providing ozone gas at a concentration of 5 ppm as an ozone gas-liquid mixture to the treating chamber 120 may provide the desired degree of sanitizing without overly extending the wash cycle. Maintaining the concentration of ozone gas at 5 ppm for 15-30 minutes can provide a 5-log reduction of microorganisms, such as the bacteria Escherichia coli (E. coli), for example. This level of sanitization is significant enough to meet standards for sanitizing, while not overly extending the length of the cycle.
In addition, as discussed above with respect to the method 200, an ozone gas concentration of 5 ppm inside the treating chamber provides a concentration of less than 5 ppm outside the treating chamber if the door to the dishwasher is opened during the supply of ozone to the treating chamber. A concentration of ozone gas of about 5 ppm or less is generally considered an acceptable immediate exposure level for humans. Thus, it is not necessary to activate the lock 184 during the supply of ozone gas to the treating chamber 120 while the concentration of ozone gas inside the treating chamber 120 is maintained around 5 ppm or less.
The application of ozone to the treating chamber as a mixture of ozone gas and liquid provides a humid environment within the dishwasher, which may facilitate sanitization by the ozone gas. Thus, it is not necessary to resort to measures to increase the amount of ozone dissolved in the liquid to achieve the desired level of sanitization.
To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.

Claims

What is claimed is:

1. A method of controlling an operation of a dishwasher having a treating chamber with an access opening through which dishes may be received for treatment according to at least one automatic cycle of operation, and a closure operable to selectively open and close the access opening, the method comprising:

introducing ozone gas into the treating chamber;

maintaining the ozone gas in the treating chamber at a sanitizing concentration of 5 ppm or less by controlling the introduction of ozone gas; and

maintaining the ozone gas at the sanitizing concentration for a sanitizing time sufficient to sanitize the dishes.

2. The method of claim 1 wherein sanitizing the dishes comprises at least a 5 log reduction of at least one species of bacteria.

3. The method of claim 1 wherein the at least one species of bacteria is Escherichia coli.

4. The method of claim 1 wherein the introducing ozone gas comprises introducing the ozone gas while the closure closes the access opening.

5. The method of claim 4 wherein the introducing ozone gas while the closure closes the access opening comprises introducing the ozone gas while the closure remains fully operable.

6. The method of claim 5 wherein fully operable comprises the closure being in an unlocked state.

7. A method of controlling an operation of a dishwasher having a treating chamber with an access opening through which dishes may be received for treatment according to at least one automatic cycle of operation, and a closure for selectively closing the access opening, the method comprising:

introducing ozone gas into the treating chamber while the closure closes the access opening;

maintaining the ozone gas in the treating chamber at a sanitizing concentration where opening of the closure would result in a 5 ppm or less concentration of ozone exterior of the dishwasher upon an opening of the closure; and

maintaining the ozone gas at the sanitizing concentration until the dishes are sanitized.

8. The method of claim 7 wherein sanitized comprises at least a 5 log reduction of at least one species of bacteria.

9. The method of claim 8 wherein the at least one species of bacteria is Escherichia coli.

10. The method of claim 7 wherein the ozone gas is maintained at the sanitizing concentration for 30 minutes.

11. The method of claim 7 wherein the treating chamber has a volume of 0.12 cubic meters.

12. The method of claim 7 wherein the introducing ozone gas while the closure closes the access opening comprises introducing the ozone gas while the closure remains fully operable.

13. The method of claim 12 wherein fully operable comprises the closure being in an unlocked state.

14. A method for sanitizing dishes in a dishwasher having a treating chamber with an access opening through which dishes may be received for treatment according to at least one automatic cycle of operation, and a closure operable to selectively open and close the access opening, the method comprising sanitizing any dishes within the treating chamber by introducing ozone gas into the treating chamber to maintain a 5 ppm or less sanitizing concentration of ozone gas within the treating chamber for a time sufficient to obtain a 5 log reduction in at least one species of bacteria, while the closure remains fully operable.

15. The method of claim 14 wherein the at least one species of bacteria is Escherichia coli.

16. The method of claim 14 wherein the ozone gas is maintained at the sanitizing concentration for 30 minutes.

17. The method of claim 14 wherein fully operable comprises the closure being in an unlocked state.

18. A dishwasher for treating dishes according to a cycle of operation, comprising:

a tub at least partially defining a treating chamber;

a sprayer providing a spray of liquid into the treating chamber;

a recirculation circuit recirculating the sprayed liquid from the treating chamber to the sprayer at a first pressure;

an ozone circuit fluidly coupling the recirculation circuit to the sprayer;

an ozone generator outputting ozone gas;

a venturi in fluid communication with the ozone circuit and the ozone generator such that when liquid passes through the venturi from the ozone circuit, the ozone gas is drawn into the liquid passing through the venturi to form an ozone gas-liquid mixture and the ozone gas-liquid mixture is emitted from the venturi to the sprayer, with the ozone gas-liquid mixture being at a second pressure, which is less than the first pressure;

a valve selectively coupling the ozone circuit to the recirculation circuit; and

a controller operably coupled to the valve to control an introduction of the ozone gas-liquid mixture to the sprayer according to the cycle of operation.

19. The dishwasher of claim 18 further comprising a filter in fluid communication with the recirculation circuit, and the ozone circuit fluidly couples to the recirculation circuit downstream of the filter.

20. The dishwasher of claim 18 wherein the sprayer comprises at least one rotating spray arm.

21. The dishwasher of claim 18 wherein the controller is configured to introduce the ozone gas-liquid mixture into the treating chamber to maintain the ozone gas in the treating chamber at a sanitizing concentration of 5 ppm or less to sanitize the dishes.

22. The dishwasher of claim 21 wherein sanitizing the dishes comprises at least a 5 log reduction of at least one species of bacteria.

23. The dishwasher of claim 18 further comprising a closure operable to selectively open and close an access opening to the treating chamber, and wherein the closure remains fully operable during the introduction of the ozone gas-liquid mixture.

24. A method of operating a dishwasher having a treating chamber in which dishes are received for treatment according to a cycle of operation, the method comprising:

recirculating liquid within the treating chamber to treat the dishes;

providing ozone gas to a low pressure input of a venturi;

generating an ozone gas-liquid mixture by diverting the recirculating liquid through the venturi to draw the ozone gas into the liquid passing through the venturi; and

supplying the ozone gas-liquid mixture to the treating chamber.

25. The method of claim 24 wherein the supplying of the ozone gas-liquid mixture occurs during a rinse phase of the cycle of operation.

26. The method of claim 24 further comprising filtering the liquid prior to generating the ozone gas-liquid mixture.

27. The method of claim 24 further comprising spraying the recirculating liquid in the treating chamber.

28. The method of claim 24 further comprising draining liquid from the treating chamber prior to diverting the recirculating liquid through the venturi.

29. The method of claim 24 wherein the diverting the recirculating liquid through the venturi occurs for a predetermined period of time.

30. The method of claim 29 further comprising actuating a heater upon expiration of the predetermined period of time.

31. The method of claim 24 wherein the recirculating the liquid within the treating chamber occurs at a first pressure.

32. The method of claim 31 wherein the supplying the ozone gas-liquid mixture to the treating chamber occurs at a second pressure, lower than the first pressure.

33. The method of claim 24 wherein the supplying the ozone gas-liquid mixture to the treating chamber comprises spraying the ozone gas-liquid mixture through at least one sprayer.

34. The method of claim 24 further comprising supplying the ozone gas-liquid mixture to maintain the ozone gas at a sanitizing concentration of 5 ppm or less to sanitize the dishes.

35. The method of claim 34 wherein sanitizing the dishes comprises at least a 5 log reduction of at least one species of bacteria.