Pipes and tubular conduits – Repairing
Reexamination Certificate
2001-12-19
2003-09-23
Gulakowski, Randy (Department: 1746)
Pipes and tubular conduits
Repairing
C134S025200, C134S05600D, C134S0570DL
Reexamination Certificate
active
06622754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for controlling the wash cycle of an automatic dishwasher. In one aspect, the invention relates to detecting the dish load in a dishwasher. In another aspect, the invention relates to the selecting of the steps and/or sub-cycles of the overall wash cycle in response to the detected dish load. In yet another aspect, the invention relates to adjusting the operating parameters, such as selecting the steps for the overall wash cycle and setting the variables for the steps based upon the size of the dish load.
2. Description of the Related Art
Domestic dishwashers are well known and have a general configuration regardless of the type of dishwasher, i.e. built-in, set-in, or stand-alone. The general configuration includes an open-faced tub, closable by a door, in which are mounted drawers and/or baskets for holding the dishes to be cleaned. A sump is located in the bottom of the tub along with a pump that circulates the water in the sump through a circulation system, generally comprising upper and lower sprayers, onto the dishes. A heating element is normally included to heat the water.
To clean the dishes, domestic dishwashers draw wash liquid from the sump at the bottom of the wash tub and spray the wash liquid within the wash tub to remove soil from dishes located on the baskets in the tub. The soil-entrained wash water is usually drained away. Large amounts of soil removed from the dishes and retained in the recirculating wash liquid can adversely impact the performance of the dishwasher. Therefore, an overall wash cycle may include multiple sequences or sub-cycles of the steps of water filling, circulating, and draining to adequately remove the soil. In some cases, the drain step is replaced with a step of filtering the soil from the water in combination with a partial drain and fill, which is referred to as a purge. The temperature of the water and the duration of the circulation are factors that control the soil removal. It is known to employ a system for adjusting the wash cycle duration and temperature in response to the level of soil in the wash liquid.
Dishwasher wash performance is also related to the size of the dish load, i.e. the number of dishes, in the wash chamber. All things being equal, large loads require longer wash cycles, higher temperature wash liquid, and more wash and rinse sub-cycles for a satisfactory level of cleaning. Smaller loads require shorter wash cycles, lower temperature wash liquid, and fewer wash and rinse sub-cycles.
Without any other constraints, all wash cycles could be conducted based on a “worst-case” approach: a full load of dishes with a high soil content. This would ensure that the dishes were adequately cleaned every time. However, increasing energy costs and increasing environmental awareness dictate that the energy used and water consumed be no greater than that needed to clean the dishes and thereby avoid wasting resources.
While there are presently many different methods for determining the soil content, the same cannot be said for determining the size of the dish load. Presently, selecting a wash and rinse cycle appropriate to the dish load is typically done by selecting one of a limited number of standardized cycles based on an estimate of the extent to which the selected cycle accurately corresponds to the actual dish load.
If the standardized cycle does not accurately represent the actual dish load and soil load, the wash liquid temperature may be too low or unnecessarily high, or the wash cycle duration may be too short or unnecessarily long. For example, heavily soiled dishes may not be washed in sufficiently hot water because a large wash cycle has not been selected, resulting in a poor wash performance. In other circumstances, dishes which are relatively lightly soiled and do not require as high a wash liquid temperature may nevertheless be washed in relatively hot wash liquid because a large wash cycle was selected. For example, lightly soiled dishes may be washed too long or there may be more water changes than necessary if a large load is indicated, which can result in unnecessary energy usage.
Accordingly, there is a need for a dishwasher wash system that can automatically adjust the temperature and duration of the wash cycle, the number of rinses, and the duration of the rinses in response to the dish soil level and dish load size.
SUMMARY OF THE INVENTION
In one aspect, the invention relates to a method of determining a dish load in an automatic dishwasher comprising a tub for receiving dishes to be cleaned, a water inlet valve for introducing water into the tub, a spraying assembly for spraying the water throughout the tub to clean the dishes, a heating element for heating the water, a temperature sensor for sensing the temperature of the water, and a controller. The controller is operably coupled to and controls the operation of the water inlet valve, spray assembly, heating element, and temperature sensor to introduce water into the tub, spray the water, and drain the water to wash the dishes according to a wash cycle stored in the controller.
The method comprises introducing a first charge of water into the tub and spraying the first charge of water throughout the tub. A first temperature is determined corresponding to the temperature of the first charge of water when the temperature of the first charge of water and dishes are substantially equalized. The first charge of water is then removed from the tub. A second charge of water is introduced into the tub. A second temperature is determined that corresponds to the temperature of the second charge of water prior to a time when the second charge of water contacts and transfers heat to the dishes. The second charge of water is sprayed throughout the tub. A third temperature, corresponding to the temperature of the second charge of water when the temperature of the first charge of water and dishes are substantially equalized, is then determined. The dish load is determined by calculating a temperature ratio of the difference between the second and third temperatures and the difference between the third and first temperatures.
Preferably, the determination of the second temperature occurs after the initiation of the introduction of the second charge of water. The determination of the second temperature can be delayed for a predetermined time after the initiation of the introduction of the second charge of water. The determination of the second temperature is preferably done prior to the spraying of the second charge. The determination of the second temperature can be accomplished by setting the second temperature equal to the maximum temperature sensed by the sensor within a predetermined time after the initiation of the introduction of the second water charge.
The determination of the dish load can include comparing the temperature ratio to a predetermined threshold value and selecting a dish load based on the comparison.
Preferably, the selection of the dish load comprises selecting the dish load from a group of dish load categories such as, for example, a group comprising at least large and small categories.
The threshold value is preferably selected based on at least one physical characteristic of the dishwasher such as, for example, the material from which the tub is made.
In another aspect, the invention relates to a method for cleaning dishes based on the dish load in an automatic dishwasher. The automatic dishwasher comprises a tub for receiving dishes to be cleaned, a water inlet valve for introducing water into the tub, a spraying assembly for spraying the water throughout the tub to clean the dishes, a heating element for heating the water, a temperature sensor for sensing the temperature of the water, and a programable controller. The controller is operably coupled to and controls the operation of the water inlet valve, spray assembly, heating element, and temperature sensor to wash the dishes according to a wash cycle programmed into the controller. The wash cycle h
Groppel Stephen M.
Roth Ryan Kevin
Chaudhry Saeed
Colligan John F.
Gulakowski Randy
Krefman Stephen
Rice Robert O.
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