US20160029869A1

US20160029869A1 - Dishwasher with vacuum drying and method

Info

Publication number: US20160029869A1
Application number: US14/880,930
Authority: US
Inventors: David R. McKinney
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-06
Filing date: 2015-10-12
Publication date: 2016-02-04

Abstract

An automatic dishwasher, having a wash cycle and a drying cycle, includes an openable and closeable washing chamber, at least one spray apparatus inside the washing chamber, and a vacuum pump in fluid communication with the washing chamber. The washing chamber has an interior configured to contain articles to be washed, and is configured to withstand vacuum pressure when closed. The at least one spray apparatus is configured to spray a cleaning fluid upon the articles to be washed during the wash cycle. The vacuum pump is configured to evacuate the interior of the washing chamber to a selected vacuum pressure level during at least a portion of the drying cycle.

Description

PRIORITY CLAIM

The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/202,044, filed on Aug. 6, 2015 and entitled DISHWASHER WITH VACUUM DRYING, the contents of which are incorporated by reference herein in their entirety.

FIELD OF THE DISCLOSURE

The present application relates to automatic dishwashers. More particularly, the present application relates to a dishwasher that uses vacuum pressure to assist with drying dishes or other articles placed therein.

BACKGROUND

Automatic dishwashers are a common household appliance, and commercial dishwashers are also widely used in the food service industry. Automatic dishwashers clean dishes by directing high pressure jets of heated water, mixed with detergent, against dishes in an enclosed chamber. The water is often filtered to remove food particles and recirculated by a pump, so that the dishes can be thoroughly washed while limiting the overall quantity of water that is used. Following the wash cycle, a final rinse of clean, hot water is typically sprayed against the dishes, after which the rinse water is drained from the wash chamber, and the dishes are allowed to dry. An electrical heating element in the wash chamber is often activated to raise the temperature during the drying cycle, to speed the drying of the dishes. Some dishwashers, particularly commercial dishwashers, also use a blower to blow air through the washing chamber during the drying cycle, to assist with the drying process.
It is generally considered desirable that the dishes emerge from the dishwasher completely dry. Nevertheless, even with commercial dishwashers, there is often some residual rinse water remaining on the dishes, such as in crevices of the dishes or between adjacent items that contact each other. This aspect is fairly common with household dishwashers, and tends to diminish the effectiveness of the drying cycle.
At the same time, it is also desirable that dishwashers use as little energy in their operations as possible. Indeed, industry standards and government regulations increasingly limit the quantities of water and energy that dishwashers can use. These factors place a variety of constraints on dishwasher manufacturers. For example, many dishwashers have a selectable air dry mode that does not apply heat during the drying cycle. Unfortunately, depending on water hardness and other factors, air drying often produces results that are considered unsatisfactory to consumers.
The present application is directed to one or more of the above issues.

SUMMARY

In accordance with one aspect thereof, the present disclosure provides an automatic dishwasher, having a wash cycle and a drying cycle. The dishwasher includes an openable and closeable washing chamber, having an interior configured to contain articles to be washed, and at least one spray apparatus inside the washing chamber, configured to spray a cleaning fluid upon the articles to be washed during the wash cycle. The washing chamber is configured to withstand vacuum pressure when closed, and the dishwasher includes a vacuum pump in fluid communication with the washing chamber. The vacuum pump is configured to evacuate the interior of the washing chamber to a selected vacuum pressure level during at least a portion of the drying cycle.
In accordance with another aspect thereof, the present disclosure provides a dishwasher, including a washing tub, having a door and walls enclosing an interior configured to contain articles to be washed, at least one spray apparatus, disposed in the interior of the washing tub, a vacuum pump, in fluid communication with the interior of the washing tub, and a controller, coupled to the spray apparatus and the vacuum pump. The washing tub is configured to withstand vacuum pressure in the interior when the door is closed. The at least one spray apparatus is configured to spray a heated cleaning fluid upon the articles to be washed during a wash cycle of the dishwasher. The vacuum pump is configured to evacuate the interior of the washing tub to a selected vacuum pressure level during at least a portion of a drying cycle of the dishwasher. The controller is configured to control a duration and vacuum pressure level of operation of the vacuum pump during the drying cycle.
In accordance with yet another aspect thereof, the present disclosure provides a method for washing articles in a dishwasher having a washing chamber. The method includes spraying a cleaning fluid upon the articles within the washing chamber during a wash cycle of the dishwasher, and evacuating the washing chamber to a vacuum pressure level during at least a portion of a drying cycle of the dishwasher.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partial sectional view of a conventional household dishwasher.

FIG. 2 is a side, cross-sectional view of an embodiment of a household dishwasher with vacuum drying, in accordance with the present disclosure.

FIG. 3 is a schematic diagram of the dishwasher of FIG. 2.

FIG. 4 is a cross-sectional view of an embodiment of a dishwasher tub configured for withstanding vacuum pressure, in accordance with the present disclosure.

FIG. 5 is a partial cross-sectional view of another embodiment of a dishwasher tub configured for withstanding vacuum pressure, in accordance with the present disclosure.

FIG. 6 is a perspective view of an embodiment of a commercial dishwasher with vacuum drying, in accordance with the present disclosure.

FIG. 7 is a perspective view of another embodiment of a commercial dishwasher system with vacuum drying, in accordance with the present disclosure.

FIG. 8 is a flowchart outlining the steps in a method of drying dishes in an automatic dishwasher using vacuum pressure, in accordance with the present disclosure.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Shown in FIG. 1 is a perspective, partial sectional view of a conventional household dishwasher 100. This type of dishwasher is commonly configured for installation below a kitchen countertop, though freestanding units of this type are also available, and other dishwasher configurations are also known. The dishwasher 100 generally includes a wash tub or chamber 102, with an openable door 104. Disposed within the tub 102 are one or more spray arms 106, such as an upper spray arm 106 a and a lower spray arm 106 b, which dispense jets of water for washing and rinsing dishes. Lower-end models have plastic wash tubs 102, while high- and some mid-priced units have stainless steel tubs, which have become more popular in recent years. A lower portion of the wash tub 102 includes a depression or sump region 108, with a float valve 110 for detecting the water level in the sump 108. A heating element 112 can be disposed within the water sump area 108, and is used for heating water in the sump 108, and also for heating the interior of the wash tub 102 during a dish drying cycle. Also disposed within the tub 102 are moveable racks 114 for holding dishes or other items to be washed. These racks 114 can be extended out from the wash tub 102 to allow for easy loading and unloading of dishes.
The door 104 of the dishwasher includes a latch 116 and is designed to securely close against a door gasket 118 at the front opening 120 of the wash tub 102, to provide a water-tight seal while the dishwasher 100 is operating. A detergent dispenser 122 is often also attached to the inside 124 of the door 104, and dispenses dish detergent (e.g. powder or liquid) at a specific point in the dishwashing cycle. A rinse aid dispenser 126 can also be provided to dispense a rinse assisting agent during the final rinse phase of the dishwashing cycle.
The major electrical and mechanical components of the dishwasher 100 are often disposed behind an access panel 128 below the wash tub 102. These generally include a power supply 130, a water pump and motor 132, a water supply line 133 with an inlet valve 134, and a water drain hose 136. The power supply 130 can be hard-wired into a household electrical system, or it can include a plug (not shown) that plugs into an electrical outlet (e.g. located inside or behind a cabinet and under a countertop, not shown). During a pump cycle, the pump 132 forces water up into the spray arms 106 to wash or rinse the dishes. During a drain cycle, the pump 132 draws water from the sump 108 and into the drain hose 136. The pump 132 can be reversible or non-reversible. Reversible pumps switch between pumping water to the spray arms 106 and pumping water to the drain 136 by reversing their pumping direction. Non-reversible pumps run in only one direction, and the direction of flow can be switched from the spray arms 106 to the drain by opening and closing appropriate valves to switch one hose connection to another.
The controls of the dishwasher can be located inside the door 104 behind an upper control panel (not shown in FIG. 1), or in a fixed control panel 138 that is above the door 104, as shown in FIG. 1. Some dishwashers use a simple electro-mechanical controller with a mechanical dial and timer that determines how long each part of a cycle lasts and activates the proper functions at the proper time (such as the detergent dispenser, wash spray and draining functions). Newer and higher-priced dishwashers, like that shown in FIG. 1, typically include a computerized control system, with push-button control devices, digital readouts, computerized timers and other features, as shown at 138 in FIG. 1. Electronically controlled dishwashers can offer a wide variety of cycle options, including high pressure super heavy-duty, crystal/china and sanitizing modes, for example. Sensors (not shown in FIG. 1) can also be included in the dishwasher, for example to sense the level of dirtiness of the water, etc. Most dishwashers, whether old or new, mechanically- or electrically-controlled, include a heated dry cycle, or at least the option of such, which will dry dishes more quickly.
The exterior of the wash tub 102 is typically covered with insulation (not shown) to reduce noise transmission and retain heat while the dishwasher is operating. Insulation is typically also included in the door 104. Dishwashers that are more expensive typically have heavier insulation to reduce noise. They may also include higher quality components (e.g. the dishwasher pump) that run quieter. It is to be appreciated that the dishwasher 100 shown in FIG. 1 is just one type of dishwasher. Other types and configurations are also known, such as in-sink-type dishwashers and drawer-type dishwashers. Moreover, a variety of additional features and alternative configurations can be associated with a dishwasher, beyond those shown and described here. Nevertheless, this description presents the basic operational components that are common to many dishwashers.
Modern dishwashers generally function in the same basic way. Still with reference to FIG. 1, once dishes or other articles to be cleaned are loaded in the racks 114 of the dishwasher 100 and detergent is added, the user simply closes and latches the door 104, sets the desired washing cycles using the control panel 138, and turns the dishwasher on. The dishwasher 100 then opens the water inlet valve 134 to add water to the sump 108 until the float 110 valve rises to indicate that the sump 108 is full. When the intake valve 134 opens, water pressure in the water supply pipe 133 drives the water into the sump region 108, without any need for pumping.
The dishwasher 100 then heats the water in the sump 108 to a set temperature (e.g. to 130° to 140° F.) using the heating element 112, and uses this water for a first rinse cycle. To do this, the dishwasher pump 132 is activated, drawing water from the sump 108 and pumping the water through the spray arms 106. The pressure of the water drives the rotation of the spray arms 106, and the water sprays out through the water jets of the spray arms 106 in multiple directions to rinse the dishes. The rinse water continuously drains back into the sump 108, where it is drawn back into the pump 132 and recycled for continued rinsing, thus minimizing water usage.
The inlet to the pump 132 can include a filter (not shown) to screen out food bits and other debris that are rinsed off during this process, so that the pump 132 pumps substantially clear water, and dirty water can be drained. The dishwasher drain line 136 can connect to drain pipes associated with a nearby sink, or it can drain into the sink itself, or directly into its own drain, depending on the type of dishwasher and the installation.
Following rinsing (and at other appropriate times during the wash cycle), the pump 132 is used to pump the dirty water from the sump 108 to the drain 136, after which the water inlet valve 134 can be opened again to refill the sump 108 with clean water, and this new water can then be heated and used in the same manner as before. After a rinsing cycle (if there is one), the dishwasher 100 commences a wash cycle, in which it automatically opens the detergent dispenser 122 at an appropriate time, allowing detergent to drop into the sump 108 to mix with the wash water. Again, the dishwasher pump 132 is activated, drawing water from the sump 108 and pumping the water through the spray arms 106 to wash the dishes. After washing in one or more wash cycles, the dirty water can again be drained and the sump 108 refilled with clean water, and a final rinse cycle can be initiated to rinse the dishes, after which the rinse water is again drained for the last time.
Modern dishwashers can monitor themselves, to make sure everything is running properly. A timer (or a small computer controller) can regulate the length of each cycle, with sensors to detect the water and air temperature to prevent the dishwasher from overheating. Other sensors can detect whether the water level is too high and some dishwashers have sensors to detect the dirtiness of the water coming off of the dishes. With these dishwashers, when the water is clear enough, a signal from the sensor will indicate to the dishwasher controller that the dishes are clean, and the dishwasher can transition to the final rinse cycle.
After the final rinse water is drained from the sump 108, the heating element 112 can again be activated to heat the interior of the wash tub 102 to assist with drying the dishes, if the user has selected a heat-dry setting. Alternatively, dishes can be left to air dry, without heat, in order to conserve energy. Unfortunately, air drying often leaves water spots, depending upon the characteristics of the water supplied to the dishwasher, and also tends to leave larger amounts of water trapped in crevices and other small spaces that are often found in various types of dishes and other items that are often cleaned in automatic dishwashers. Oddly shaped items, in particular, can include portions where water pools and does not drain away or dry up. Even when heated drying is used, noticeable and annoying quantities of rinse water can remain trapped on dishes and other items. This can necessitate hand-drying of dishes upon removal from the dishwasher, in order to avoid stacking and/or storing dishes that are still partly wet.
Advantageously, a dishwasher with a vacuum drying capability is described herein. Shown in FIG. 2 is a side, cross-sectional view of an embodiment of an automatic dishwasher 200 with vacuum drying, in accordance with the present disclosure, and a schematic diagram of the same is provided in FIG. 3. As with conventional dishwashers, this dishwasher includes a wash tub or chamber 202, configured to contain articles to be washed, with an openable door 204 and a spray apparatus, indicated generally at 206, disposed inside the washing chamber 202, including one or more spray arms 206 a, 206 b positioned adjacent to moveable racks 214 for holding dishes and the like. As used herein, the terms “dishes” and “articles to be washed” and “items to be washed” are used interchangeably to refer to any items that may be placed in a dishwasher for cleaning.
This dishwasher 200 has a wash cycle and a drying cycle, and the spray apparatus 206 is configured to spray a cleaning fluid (e.g. water mixed with detergent) upon the articles to be washed during the wash cycle. The dishwasher 200 also includes a heating device, such as an electric heating element 212, disposed in the lower portion of the wash tub 202, as is common in automatic dishwashers. The heating element 212 can be used to heat water for washing and rinsing the dishes, and can also be used for heating the interior of the washing chamber 202 to a selected heat level during the drying cycle. The lower portion of the wash tub 202 also defines a water sump 208, and a float valve 210 is provided for detecting the water level in the sump. The door 204 of the dishwasher is designed to securely close against a door gasket 218 at the front opening 220 of the wash tub 202, and includes a latch (not shown) and a detergent dispenser 222 on the inside of the door 204.
A power supply 230, a water pump 232 and pump motor 231, a water supply line 233 with a power-actuated inlet valve 234, and a drain hose 236 are disposed below the wash tub 202 behind an access panel 228. The dishwasher 200 includes a controller 240, that can be located inside the door 204 or behind an upper control panel 238 of the door 204, or in a fixed control panel (not shown in FIG. 2) that is above the door 204, or in some other location. These electrical and mechanical components can be generally like those of conventional dishwashers, described above.
Advantageously, the washing chamber 202 is configured to withstand vacuum pressure, and, in addition to the typical dishwasher components, the dishwasher of FIGS. 2 and 3 includes a vacuum pump 250 and associated features configured to evacuate the interior of the washing chamber to a selected vacuum pressure level during at least a portion of the drying cycle. The vacuum pump 250 includes its own motor 252, and has an inlet 254 in fluid communication with the interior of the wash tub 202. The inlet 254 can be located and designed to prevent water from entering the vacuum pump during the wash and rinse cycles. Additionally, a vacuum pump inlet valve 256 (FIG. 3) can be provided to close the vacuum pump inlet 254 except when the pump 250 is to be operated. It is anticipated that this valve 256 will be kept closed during the wash and rinse cycles, and only opened during the drying cycle, though it is possible that other operational modes can be used. The vacuum pump 250 has an outlet 258 that leads to the outside of the dishwasher, for exhausting air that is pumped out of the wash tub 202.
The vacuum pump 250, its inlet 254 and outlet 258 can be provided in a wide variety of locations, only a couple of which are shown herein. For example, the vacuum pump 250 can be located below the wash tub 202, near the water pump 232, and its outlet 258 can extend from this location to an exhaust location through the access panel 228. The inlet 254 can be in a sidewall of the wash tub 202, and can have a shape, such as the inverted U shape shown in FIG. 2, that helps prevent water from entering the vacuum pump inlet during the wash and rinse cycles. Other configurations of the inlet 254 can also be used.
Alternatively, the vacuum pump exhaust outlet 258 can be located near the top of the dishwasher unit 200, such as extending through a top portion of the dishwasher door 204, as shown in dashed lines in FIG. 2. Another alternative location for the vacuum pump 250 is suggested in the schematic diagram of FIG. 3. In this view, the vacuum pump 250 is positioned above the wash tub 250, with the vacuum inlet 254 located in the top wall 264 of the wash tub 202. Another location is suggested in FIG. 4, wherein a vacuum pump 450 is positioned near an upper corner 490 of a wash tub 402, behind the dishwasher door 404 and façade 466, with the vacuum inlet 454 positioned near a top of one of the side walls of the wash tub 402. Many other variations are also possible. As shown in FIG. 3, a vacuum release valve 268 is also provided to allow the release of vacuum pressure at the end of the vacuum drying cycle, or to ensure that the vacuum pressure level does not exceed some design threshold.
Vacuum pumps that are suitable for this purpose are commercially available from a variety of sources. Vacuum pumps are widely used in food processing and semiconductor fabrication, for example, and many pumps that have been developed for use in these and other industries could be adapted for use in the dishwasher disclosed herein. There are also many types of vacuum pumps that can be suitable, such as piston pumps, scroll pumps, rotary vane pumps, diaphragm pumps, etc. Commercial sources for vacuum pumps include Edwards Vacuum, based in Crawley, West Sussex, UK; Busch USA, of Virginia Beach, Va.; and Gardner Denver, Inc. of Milwaukee, Wis. Vacuum pumps are also available from other sources.
It is anticipated that a typical residential dishwasher may have an internal volume up to about 6 cu. ft., though the volume can be more or less than this. Commercial dishwashers may have a significantly larger internal volume in the wash chamber. Once the desired pump volume and maximum vacuum pressure level are known, it can be a relatively straight-forward matter to select a vacuum pump that can pump a chamber of this volume to the desired vacuum pressure within a selected time, such as 5 or 10 minutes. The characteristics of the selected vacuum pump and its duration of operation can also be affected by any known or anticipated level of leakage of air into the dishwasher tub during pumping. It is also desirable that the vacuum pump be adapted for pumping steam or saturated air, and at an elevated temperature that is likely in the dishwashing and drying environment. Pumps that can satisfy all of these criteria are commercially available from the sources mentioned above. Other considerations, such as low energy usage and quietness of operation, can also be factored into the choice of the vacuum pump.
Returning to FIGS. 2 and 3, a variety of power-operated valves are provided to seal the wash tub during the vacuum drying process. As discussed above, the water inlet line 233 includes an automatic inlet valve 234, as is common in most dishwashers. The main pump 232 also includes an inlet valve 270 and an outlet valve 272, and valves are also provided in association with the vacuum pump and vacuum release valve, as discussed above. The conduits associated with these valves and all other components that pierce the wall of the wash tub 202 are configured with sufficient strength to withstand vacuum pressure during the drying phase, and to minimize leakage of air into the wash tub 202. One or more sensors 274 can be disposed within the washing chamber 202, in addition to sensors that are commonly found in dishwashers generally, and is coupled to the controller 240. The sensor 274 can be configured to sense at least one of pressure, temperature and humidity within the washing chamber 202, and the controller 240 can be configured to determine the duration and pressure level for the drying cycle based on signals from the sensor 274. Sensors to detect other parameters in the interior of the wash tub 202 can also be provided.
The various valves 234, 256, 268, 270 and 272, along with the sensors 274 and other components of the dishwasher 200, are coupled to the controller 240, which governs their operation and/or receives input from them. The controller 240 is coupled to the vacuum pump 250 and other components of the dishwasher 200, and is configured to control a duration and vacuum pressure level of operation of the vacuum pump 250 during the drying cycle. The controller 250 can be a mechanical dial and timer system, or a computerized control system, as discussed above. For example, the controller 240 can be a microprocessor device having a processor and system memory and provided with programming instructions for time-based and/or sensor-based control of the spray apparatus 206, the vacuum pump 250, and for controlling the wash cycle and the drying cycle. Following the final rinse cycle, the rinse water is drained from the sump 208 by the main pump 232, and pumped into the drain outlet 236. At this point in the process, the main pump valves 270, 272, the water inlet valve 234 and the vacuum release valve 268 are (or remain) closed, and the vacuum pump valve 256 is opened. The controller 240 activates the vacuum pump 250, which pumps air from the wash tub 202 through the outlet 258, producing a partial vacuum therein.
It will be appreciated that the air pumped from the wash tub 202 will include a significant quantity of water/water vapor that remains from the final rinse process, such that the exhaust from the vacuum pump 250 will, at least at first, comprise a significant quantity of water vapor. This will be particularly true if the heating element 212 is activated during the vacuum pumping process. However, as drying continues and air pressure in the wash tub 202 drops, the amount of water vapor in the wash tub (and hence in the vacuum exhaust) will gradually diminish. The vacuum pumping process can continue in a variety of ways. For example, the controller 240 can be programmed to pump for a specified time interval. Alternatively, it can be programmed to pump until a specified vacuum pressure level is reached, as detected by the sensor 274. As another alternative, pumping can continue until a specified humidity level is reached in the wash tub 202, as detected by the sensor 274.
After the desired vacuum drying conditions have been reached, the vacuum pump 250 can be stopped, the vacuum pump valve 256 can be closed, and the vacuum release valve 268 can be opened, to allow the wash tub 202 to return to atmospheric pressure. Alternatively, when the desired vacuum drying conditions have been reached, the dishwasher 200 can enter a hold mode, wherein the final vacuum conditions are simply maintained for some time interval t. This hold mode can be accomplished in several ways. In one approach, the vacuum pump 250 is stopped, the vacuum pump valve 256 is closed, and all other valves and openings into the wash tub are kept closed. So long as the tub 202 has minimal air leakage, vacuum conditions can be maintained for a period of time that allows continued drying of the dishes, but without using additional energy. Alternatively, if leakage into the tub 202 is an issue, the desired pressure level can be held by continued pumping of the vacuum pump 250, for example at a lower power level. As yet another alternative, the hold interval t can involve one or more time intervals with the pump 250 off and all valves or openings closed, followed by a brief interval of additional vacuum pumping, to regain the desired pressure level if it has diminished because of leakage. At the end of the hold time interval t, the vacuum release valve 268 can be opened, under control of the controller 240, allowing the wash tub 202 to return to atmospheric pressure.
As noted above, the heating element 212 can be activated while the vacuum pump 250 is operating, so that both elevated heat and vacuum conditions are applied to dry the dishes or other items in the dishwasher 200. Alternatively, it is possible that vacuum drying alone can be sufficient to entirely dry the dishes, without the need for additional heat. Where the final rinse of the dishes uses heated water, the residual heat from that final rinse may be sufficient, combined with the vacuum pressure, to adequately dry the dishes. Thus, any combination of heat and vacuum pressure, both in terms of magnitude and temporal duration, can be used, or vacuum pressure alone can be used, depending on the vacuum pressure level.
It is to be appreciated that the wash tub 202 is designed as a pressure vessel, and is configured to withstand the vacuum pressure that is exerted upon it. Those of skill in the art will recognize that there are a variety of ways to configure a wash tub that can withstand vacuum pressure, depending on the level of that pressure. As shown in FIG. 2, the opening 220 of the wash tub 202 that accommodates the door 204 includes a face frame 280 that carries a seal element 218. This frame 280 can be of high strength material, such as stainless steel, and is configured to maintain the shape of the opening 220 during the vacuum process. The dishwasher door 204 can include a corresponding frame element (not shown) that mates with the wash tub face frame 280, and includes an opposing seal element (not shown) for providing a strong seal around the door 204.
In addition to tight seals around the door 204 and strong valves for the various pump openings and the like, the wash tub 202 and door 204 are designed to withstand the anticipated vacuum pressure. This can be done in many ways. Many dishwasher tubs are molded of polymer material, while others are fabricated from metals, such as stainless steel. It will be apparent that increasing the strength and rigidity of these materials and of the overall wash tub construction to withstand the desired pressure can be accomplished in many ways, by either increasing the strength and/or thickness of the materials, or modifying their shape, or both.
A variety of options exist for changing the shape or design of the wash tub 202 to provide a suitable pressure vessel, and any suitable methods, whether now known or later developed, are contemplated by this disclosure. One such option is shown in FIG. 4, in which a wash tub 402 is shown having walls 403 with double curvature. In this cross-sectional view, looking at the back of a façade or surround 466 for the dishwasher 400, the outline of the door opening 404 is shown in dashed lines, as are the dish racks 414, the spray arms 406 and the main pump 432. The wash tub 402 includes sidewalls 403 that have corner portions 490 that form the edges or corner members of the generally rectangular dishwasher tub structure, with the portions of the sidewalls 403 between the edge or corner portions 490 having a 3-dimensionally outwardly curved shape, such as a hemispherical, ellipsoid or paraboloid shape. These curved wall shapes could be used for all sides of the wash tub 402 and for the inside of the door 404. Such double-curved shapes provide significantly greater strength for a given thickness than flat panels, though they may cause the overall size of the dishwasher to be larger relative to its washing capacity than other dishwashers that do not have curved walls. On the other hand, the curved bottom panel 405 naturally forms a sump 408 for the washwater. This embodiment also provides a space for the vacuum pump 450 and vacuum pump inlet 454 in the upper region adjacent to one of the edge or corner portions 490 of the wash tub 402.
Another alternative for strengthening the wash tub is shown in FIG. 5. This figure shows a partial cross-sectional view of a portion of a dishwasher tub 502 near an upper corner 590 of the door opening 520. Here the face frame 580 for the door opening 520 can be seen, with the door seal 518 disposed in a channel therein. This wash tub 520 is a polymer wash tub that has generally flat walls 503, but the exterior of the walls include corrugated reinforcing panels 594, which are staked to the polymer wash tub in multiple locations, some of which are indicated at 596. The corrugated reinforcing panels 594 can be of stainless steel or other strong material, and provide strength to the wash tub walls 503 for withstanding the vacuum pressure. The corrugated reinforcing panels 594 can also be attached to each other at the corners 590 of the wash tub 502, as indicated at 598, thus providing a sort of external frame for the wash tub 502.
The selected vacuum pressure level can be any level that is considered desirable to assist in drying the dishes or other articles placed in the dishwasher. It is well known that at standard atmospheric pressure (about 14.7 psia), water boils at a temperature of about 212° F. (100° C.). At lower pressures, however, water boils (i.e. spontaneously evaporates) at lower temperatures. For example, at a pressure of about 5 psia, water will boil at a temperature of around 162° F., which is a temperature near which some dishwashers, particularly commercial dishwashers, heat the rinse water and the dishes during a final rinse cycle. At a pressure of about 1 psia, water will boil at a temperature of around 102° F. Consequently, if the vacuum pressure is low enough, all residual rinse water can be eliminated solely through the vacuum pressure, without the need for additional heat for drying. However, producing very low pressure levels requires the expenditure of greater amounts of energy. Thus, it can be desirable to select a temperature and pressure combination that will use the least energy for effectively drying the dishes or other articles. Alternatively, a temperature and pressure combination can be selected that will dry the dishes in the least amount of time. As yet another alternative, a temperature and pressure combination can be selected that will dry the dishes at a lower temperature. This can be desirable for safety reasons, for example.
Given these various temperature and pressure considerations, a variety of vacuum pressure levels can be selected. In general, the present dishwasher system and method contemplates vacuum pressures of at least about ½ psi below atmospheric pressure. For purposes of this disclosure, pressures that are not at or below this level are not considered vacuum pressures. More particularly, vacuum pressures of at least 1 psi below atmospheric pressure are considered desirable, and pressure levels that are at least 5 psi or 10 psi below atmospheric pressure are considered useful. Lower pressures can also be used.
Commercial dishwashers can also incorporate the vacuum drying features disclosed herein. Some commercial dishwashers are configured similar to the dishwashers shown in FIGS. 1-3, and these can be provided with vacuum drying features in the manner discussed above. On the other hand, some commercial dishwashers are different. Shown in FIG. 6 is a perspective view of a fairly common commercial dishwasher 600. This dishwasher 600 includes a lowerable hood 602, which is disposed above a frame 604 that is configured for supporting a moveable dish rack 606. Dirty dishes 608 are placed in the rack 606 and can first be hand-rinsed with a sprayer 609 by a worker at an adjacent sink 610, to remove large food particles, etc. The rack 606 with the partially rinsed dishes 608 is then placed upon the frame 604, and the dishwasher hood 602 is lowered by a worker using a handle 612, and thus encloses and surrounds the dish rack 606. At least some of the apparatus for washing the dishes (e.g. water jets, etc.) can be included within the hood 602. The dishwasher hood 602 seals with the frame structure 604 below when the hood 602 is closed, to create a water-tight washing chamber, in which the dishes 608 are sprayed with jets of cleaning fluid (e.g. water with detergent) for washing. A heating mechanism (e.g. heating coil(s), etc.) is included in the dishwasher 600 to heat the cleaning fluid during the wash phase(s), and to heat the dishes during a drying phase. A blower 618 and related devices can also be provided to blow air into, and withdraw air from, the washing chamber during a portion of the drying phase. When the dishes are washed and dried, the hood 602 can be lifted, and the rack 606 with the dishes 608 can be pulled over to a finish station 620, where the dishes can sit to allow additional air drying (if needed) and to cool down, while another dish rack 606 is placed in the machine 600 and the process is repeated.
The type of commercial dishwasher 600 shown in FIG. 6 can wash dishes relatively quickly, which is desirable in restaurants and other food service industries. However, even these sorts of dishwashers can do an inadequate job of drying dishes, which can be of particular concern in the food service industry, where dishes are used, washed, and reused very quickly. Advantageously, this dishwasher 600 can be configured with a vacuum drying feature in accordance with the present disclosure. In the embodiment of FIG. 6, the hood includes an upper chamber portion 614 that seals with a lower chamber portion 616 in the structure below when the hood 602 is closed for washing. The upper portion 614 and lower portion 616 are designed to come together to provide a closed wash chamber that is not only water-tight, but also provide a pressure vessel for vacuum drying of the dishes 608. A vacuum pump 650 and associated structures can be disposed in the hood 602 (or some other location), and are configured to be activated during a drying cycle. The vacuum pump 650 pumps air out of the wash chamber, which helps with drying the dishes in the manner discussed above. The air blower 618 can also be used before and/or after the vacuum drying stage, and can include a pressure door or other suitable valve mechanism (not shown) to seal it off during the vacuum drying stage.
An alternative configuration for a commercial dishwasher system 700 with vacuum drying in accordance with the present disclosure is shown in FIG. 7. In this system, a pair of dishwashing devices 760, 762 are provided with lowerable hoods 702, 704, respectively. These dishwashing devices are similar in configuration to the commercial dishwasher 600 shown in FIG. 6. However, the first unit 760 can be configured for washing the dishes only, while the second unit 762 is configured for drying only. That is, the first unit 760 is configured generally like typical commercial dishwashers of this size and configuration, but does not dry the dishes. Instead, after the washing and a final rinse phase, the hood 702 of the first unit 760 can be raised, and the dish rack 706 with clean but wet dishes 708 is moved to the second unit 762.
The second unit 762 includes within its hood 704 an upper vacuum chamber portion 714, and a lower vacuum chamber portion 716 is positioned in the lower portion of the machine. These chamber portions are configured to mate together when the hood 704 is lowered to contain the rack 706 with the wet dishes 708 and provide a second chamber (i.e. a drying chamber) that is a pressure vessel, configured for withstanding vacuum pressure inside it. A vacuum pump 750 disposed in the second unit 762 pumps air out of the second chamber, in the manner discussed above, thus drying the dishes 708. The second unit 762 can also include a heat source (not shown) to heat the air and contents of the second chamber while the vacuum pump 750 operates. When a sufficient time or pressure or humidity level are reached (e.g. as detected by sensors or established by a controller associated with the second unit 762), the second hood 704 can be raised, and the dishes 708 will be clean and dry and presumably ready for reuse, except that some cool-down time may be desirable.
It should be appreciated that other types of commercial dishwashers can also be provided with a vacuum drying feature in accordance with the present disclosure. These can have a variety of configurations and features that are not shown herein, but operate according to the same principles. The present disclosure contemplates any dishwasher that has a washing and/or drying chamber that is configured to withstand vacuum pressure, and a vacuum pump or comparable mechanism for pumping air from the chamber during a drying phase, thus using vacuum pressure, either alone or in combination with elevated temperature or other conditions, to dry dishes or other articles placed in the dishwasher for cleaning.
Shown in FIG. 8 is a flowchart outlining the steps in a method 800 of drying dishes in an automatic dishwasher using vacuum pressure, in accordance with the present disclosure. Following the start of the process 802, articles are washed 804 in a washing chamber of a dishwasher by spraying a cleaning fluid (e.g. water and detergent) upon the articles within the washing chamber during a wash cycle of the dishwasher. This can be done during multiple stages or cycles of washing and/or rinsing. After the final rinse stage 806, vacuum pressure is applied to the washing chamber 808 to some selected vacuum pressure level during at least a portion of a drying cycle of the dishwasher. Alternatively, vacuum pressure and heat can be applied to the interior of the washing chamber 810, either concurrently or separately, during at least a portion of the drying cycle. The selected vacuum pressure level can be at least 1 psi below atmospheric pressure, and more specifically can be at least 5 psi below atmospheric pressure. To further facilitate drying, air can be blown into and withdrawn from the washing chamber during a portion of the drying cycle during a portion of the drying cycle when the vacuum pump is not operating to evacuate the washing chamber.
After the desired vacuum pressure level is reached, it can be held for some time interval t as indicated at 812, after which the process ends, by release of the vacuum pressure (e.g. opening the vacuum release valve). As noted above, the vacuum pressure can be held by sealing the washing chamber to hold the pressure and stopping the vacuum pump, or by pumping at a lower rate for a time, or alternating pumping and holding. Alternatively, the system can be configured to skip the hold step 812, and moving directly to release the vacuum pressure at the stop step 814. At this point, the dishes should be dry
Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations as would be apparent to one skilled in the art.

Claims

What is claimed is:

1. An automatic dishwasher having a wash cycle and a drying cycle, comprising:

an openable and closeable washing chamber, configured to withstand vacuum pressure when closed, having an interior configured to contain articles to be washed;

at least one spray apparatus, inside the washing chamber, configured to spray a cleaning fluid upon the articles to be washed during the wash cycle; and

a vacuum pump, in fluid communication with the washing chamber, configured to evacuate the interior of the washing chamber to a selected vacuum pressure level during at least a portion of the drying cycle.

2. A dishwasher in accordance with claim 1, further comprising a heating device, associated with the washing chamber, configured to heat the interior of the washing chamber to a selected heat level during the drying cycle.

3. A dishwasher in accordance with claim 2, wherein the heating device is an electric heating element.

4. A dishwasher in accordance with claim 1, wherein the selected vacuum pressure level is at least 1 psi below atmospheric pressure.

5. A dishwasher in accordance with claim 1, wherein the selected vacuum pressure level is at least 5 psi below atmospheric pressure.

6. A dishwasher in accordance with claim 1, wherein the selected vacuum pressure level is at least 10 psi below atmospheric pressure.

7. A dishwasher in accordance with claim 1, further comprising a blower system, configured to blow air into, and withdraw air from, the washing chamber during a portion of the drying cycle.

8. A dishwasher in accordance with claim 1, further comprising a controller, coupled to the vacuum pump, configured to control a duration and vacuum pressure level of operation of the vacuum pump during the drying cycle.

9. A dishwasher in accordance with claim 8, wherein the controller comprises a microprocessor device having a processor and system memory and provided with programming instructions for controlling the spray apparatus and the vacuum pump and for controlling the wash cycle and the drying cycle.

10. A dishwasher in accordance with claim 8, further comprising a sensor, disposed within the washing chamber and coupled to the controller, configured to sense at least one of pressure, temperature and humidity within the washing chamber, the controller being configured to determine the duration and pressure level for the drying cycle based on a signal from the sensor.

11. A dishwasher, comprising:

a washing tub, having a door and walls enclosing an interior configured to contain articles to be washed, the washing tub being configured to withstand vacuum pressure in the interior when the door is closed;

at least one spray apparatus, disposed in the interior of the washing tub, configured to spray a heated cleaning fluid upon the articles to be washed during a wash cycle of the dishwasher;

a vacuum pump, in fluid communication with the interior of the washing tub, configured to evacuate the interior of the washing tub to a selected vacuum pressure level during at least a portion of a drying cycle of the dishwasher; and

a controller, coupled to the spray apparatus and the vacuum pump, configured to control a duration and vacuum pressure level of operation of the vacuum pump during the drying cycle.

12. A dishwasher in accordance with claim 11, wherein the selected vacuum pressure level is at least 1 psi below atmospheric pressure.

13. A dishwasher in accordance with claim 11, wherein the selected vacuum pressure level is at least 5 psi below atmospheric pressure.

14. A dishwasher in accordance with claim 11, further comprising a heating device, disposed within the washing tub, configured to heat the interior of the washing tub to a selected elevated temperature during at least a portion of the drying cycle.

15. A dishwasher in accordance with claim 11, further comprising a sensor, disposed within the washing tub and coupled to the controller, configured to sense at least one of pressure, temperature and humidity within the washing chamber, the controller being configured to determine the duration and pressure level for the drying cycle based on a signal from the sensor.

16. A method for washing articles in a dishwasher having a washing chamber, comprising:

spraying a cleaning fluid upon the articles within the washing chamber during a wash cycle of the dishwasher; and

evacuating the washing chamber to a vacuum pressure level during at least a portion of a drying cycle of the dishwasher.

17. A method in accordance with claim 16, wherein evacuating the washing chamber to the vacuum pressure level comprises evacuating the washing chamber to a pressure that is at least 1 psi below atmospheric pressure.

18. A method in accordance with claim 16, wherein evacuating the washing chamber to the vacuum pressure level comprises evacuating the washing chamber to a pressure that is at least 5 psi below atmospheric pressure.

19. A method in accordance with claim 16, further comprising blowing air into and withdrawing air from the washing chamber during a portion of the drying cycle and not while evacuating the washing chamber.

20. A method in accordance with claim 16, further comprising heating an interior of the washing chamber during at least a portion of the drying cycle.