Patent Grant
7690061
The invention relates generally to article cleaning processes.
Conventional cleaning apparati such as washing machines utilize timed wash and rinse cycles as part of their laundering process. One problem with relying upon timed cycles is that at the end of a given cycle, clothing or other articles being laundered may not always be clean or detergent-free. In fact, due to variations in laundry load size and detergent usage amounts from one laundering cycle to another, it is very common for clothes to contain residual amounts of detergent even after all rinse cycles have been completed. The presence of the residual detergent can cause a variety of reactions in individuals ranging from minor itching to sever skin irritation in those who may be hypoallergenic.
In order to avoid the presence of residual detergents, many washing machine manufacturers unnecessarily program their rinse cycles for durations that are longer than which may otherwise be necessary. For example, even if the residual amounts of detergents contained within clothes fall below a predetermined acceptable level prior to the completion of the programmed rinse cycles, conventional washing machines nonetheless continue to complete the preprogrammed rinse cycles without modification. This is true even in the case where minimal to no additional detergent may be removed from the clothes through additional rinsing. Accordingly, this can result in a waste of natural resources such as energy and water as well as increased operating costs for the consumer.
In accordance with one aspect of the invention, a method for controlling a laundering process includes determining a concentration of a detergent within a wash fluid during at least one cycle of an article laundering process, and dynamically adjusting at least one characteristic of the laundering process based at least in part upon the determined concentration of the detergent.
In accordance with a second aspect of the invention, an apparatus for controlling a laundering process includes a fluid chamber to contain a wash fluid, a sensor coupled to the fluid chamber to determine a detergent concentration within the wash fluid, and a controller coupled to the sensor and configured to dynamically adjust at least one characteristic of the laundering process based at least in part upon the determined detergent concentration.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments of the present invention. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, well known methods, procedures, and components have not been described in detail.
Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. Lastly, the terms “comprising”, “including”, “having”, and the like, as well as their inflected forms as used in the present application, are intended to be synonymous unless otherwise indicated.
As used herein, the term “laundering process” refers to an article cleaning process by which articles to be cleaned are exposed to one or more cleaning agents. The term “article” may refer to but need not be limited to fabrics, textiles, garments, and linens. Furthermore, the term “load” may include a mixture of different or similar articles of different or similar types and kinds of fabrics, textiles, garments and linens within a particular laundering process. The term “wash fluid” is intended to broadly refer to a liquid phase used during a wash cycle or rinse cycle of a laundering process to remove dirt, odors, detergents or other components that are non-native to the articles to be laundered. The term “wash cycle” is intended to refer to one or more periods of time, in which a laundering apparatus that contains the articles to be laundered operates using a detergent to e.g., remove dirt and odors from the articles. The term “rinse cycle” is intended to refer to one or more periods of time in which the laundering apparatus operates to remove residual detergents that were retained by the articles after completion of the wash cycle. During a wash cycle of a laundering process described herein, the wash fluid may be a mixture of one or more commonly available laundry detergents and water. Alternatively, the wash fluid may be plain water. However, due to the leaching of residual detergents from the articles during the progression of the rinse cycle, the wash fluid used in the rinse cycle may end up as a mixture of water and some amount of detergent.
As it can be appreciated, detergent concentrations in wash fluids of different wash and rinse cycles can vary greatly depending upon a number of factors including the amount of detergent used, the amount of wash fluid (including e.g., water and/or, additives) provided, the temperature of the wash fluid, and the composition of the articles and size of the load to be laundered. As such, the amount of water and number of rinse cycles necessary to remove all but an acceptable amount of residual detergent from the articles can vary greatly. Thus, in accordance with one aspect of the invention, the concentration of detergent contained within wash fluid of a laundering process may be determined and at least one characteristic of a laundering process may be dynamically adjusted based at least in part upon the determined detergent concentration. The detergent concentration may be determined during one or more wash or rinse cycles of a laundering process and further may be sensed continuously, periodically or at otherwise discrete intervals throughout the laundering process. The term “concentration” as used herein with respect to detergent is intended to refer to the amount of detergent per unit volume of wash fluid, typically measured in parts-per-million (PPM). Thus the greater the amount of detergent present within a fixed volume of wash fluid, the greater the detergent concentration will be.
With the start of CYCLE 2, clean (e.g., non-detergent containing) wash fluid such as water is pumped into the laundering apparatus. As the clean wash fluid mixes with the articles being laundered, residual amounts of detergent retained by the articles from the wash cycle begin to leach out into the wash fluid. This in turn causes the detergent concentration in the wash fluid of the first rinse cycle to gradually increase until an equilibrium point is reached (LEVEL B) where the detergent concentration level remains substantially constant independent of the amount of time remaining in the current cycle. That is, at this point, only negligible amounts of additional detergent will be extracted from the articles without the addition of or replacement by clean wash fluid. As CYCLE 2 completes at time t2, the wash fluid is emptied from the laundering apparatus and the detergent concentration immediately decreases to zero. With the start of CYCLE 3, clean wash fluid is again pumped into the laundering apparatus causing additional amounts of detergent to be extracted from the articles and subsequently detected in the wash fluid. This continues until the laundering process ends and the wash fluid is evacuated one again at time t3.
Since the detergent that is detected in the wash fluid of each rinse cycle following a wash cycle is due to residual detergent leaching from the articles being laundered, the concentration of detergent in the rinse cycles should be less than that of the wash cycle. Additionally, the respective maximum concentrations of detected detergent should continue to decrease after each successive rinse cycle.
In accordance with one embodiment, at least one characteristic of a laundering process may be dynamically adjusted based at least in part upon a determined detergent concentration. Such dynamically adjustable characteristics may include but are not limited to the number of rinse or wash cycles performed, the duration of one or more rinse or wash cycles, the amount of water used within a given rinse cycle or a wash cycle or both, and the temperature of the wash fluid. In one embodiment, one or more sensors may be used to sense the detergent concentration at one or more points in time during the laundering process. The sensors may be optical or chemical sensors and may provide an indication of the detergent concentration to a controller which may in turn control operation of the wash and rinse cycles. For example, if the detergent concentration as measured from one cycle to another consecutive cycle does not appreciably change, a process controller may be configured to dynamically stop the associated laundering process before all preprogrammed cycles have been performed (e.g., after rinse cycle 3 in
Determination of a detergent concentration within a given wash fluid may be performed in a number of ways. In accordance with one aspect of the present invention, it has been determined that a photometric analysis may be performed on the wash fluid during at least one cycle of an article laundering process to determine a relative or absolute detergent concentration. Since many commonly available detergents contain optical brighteners in the form of chromophores that contribute to ultraviolet absorbance and ultraviolet light induced fluorescence, it has been determined that a detergent concentration within a wash fluid may be ascertained based at least in part upon fluorescent properties of the wash fluid. The term “fluorescent properties” may refer to whether a substance such as wash fluid fluoresces as well as the respective emission and absorption spectra related to the substance. The use of the term “fluorescence” herein is intended to be inclusive and includes the emission properties with fluorescence lifetimes ranging from 0.02 nanoseconds to 100 seconds, preferably from 0.2 nanoseconds to 50 seconds, and more preferably from 0.25 nanoseconds to 10 seconds. As used herein, the term fluorescence is intended to include emission and luminescence.
In one embodiment at least one optical sensor may be configured within a laundering apparatus to expose the wash fluid to a first radiation and to detect a second radiation emitted by the wash fluid responsive to the first radiation. The sensor may include a radiation-emitting element such as a light emitting diode (LED) to emit radiation at a first wavelength or range of wavelengths, and a radiation-detecting element such as a photodiode to detect radiation emitted by the wash fluid in a second wavelength or range of wavelengths, which may but need not coincide with the emission wavelengths. In one embodiment, the sensor may emit radiation at wavelengths in the range of about 200 nm to about 500 nm. In another embodiment, the sensor may emit radiation at wavelengths in the range of about 220 nm to about 450 nm. In yet another embodiment, the sensor may emit radiation at wavelengths in the range of about 300 nm to about 410 nm. Additionally, the sensor may detect radiation at wavelengths in the range of about 300 nm to about 600 nm. In another embodiment, the sensor may detect radiation at wavelengths in the range of about 330 nm to about 630 nm. In yet another embodiment, the sensor may detect radiation at wavelengths in the range of about 350 nm to about 600 nm.
It should be noted that the various emitter-detector element orientations illustrated in
As alluded to earlier, the radiation-emitting element of the sensor can operate in a steady state (e.g. continuous) or pulsed (e.g. periodic) modes. Operation in the pulsed mode provides several additional capabilities that include but are not limited to the increased optical output of the radiation-emitting element during the detergent concentration measurement cycle, capability to perform time-resolved fluorescence measurements, and extension of the operational lifetime of the radiation-emitting element.
In one embodiment, a collection of descriptors may be used to characterize one or more components of a dynamic signal pattern generated by a detergent sensor in accordance with embodiments described herein.
With reference to
In operation, a laundering apparatus may employ one or more user-selectable cleaning cycles that a user may select through e.g., an analog user interface such as a dial or knob or a digital user interface. The cleaning cycles may be time limited or performance limited. For example, an article laundering apparatus may be provided with a “normal” cycle, a “water-saving” cycle and a “hypoallergenic” cycle. In the “normal” cycle, the laundering apparatus may perform a cleaning process whereby the duration of the wash and rinse cycles are time-limited. In the “water-saving” cycle, the laundering apparatus may perform a hybrid cleaning process whereby the duration of the wash and rinse cycles are ultimately time-limited, but nonetheless may be stopped before the expiration of the scheduled cycle time if e.g., one or more components of a dynamic detergent concentration signal pattern indicates that the detergent concentration meets a specified criteria. In the “hypoallergenic” cycle, the cleaning cycle may continue independently of any predetermined time periods until e.g. the level of residual detergents falls below a very low specified amount. Additional approaches for further removal of residual detergent from the article may be employed. Such approaches may include rinsing with water at higher temperatures, rinsing with more agitation, with longer cycle time, with more water, with sonication, and others.
Referring back to block 64, if a determination is made to not bypass the detergent concentration determination cycle, one or more detergent sensors may in turn determine the detergent concentration at block 65. As was described above, the detergent concentration may be determined through a photometric or a fluorescent analysis of the wash fluid. Such analyses may be performed continuously or at discrete intervals. If the detergent concentration is determined to satisfy one or more determined criteria at block 66, the current cycle may be ended before its normally scheduled end and a further determination made at block 68 as to whether additional cleaning cycles remain. If the determined detergent concentration does not satisfy one or more determined criteria at block 66, a further determination may be made at block 67 as to whether the current cycle timer has expired. If the allocated time has expired, a determination is again made at block 68 as to whether any additional cycles remain. If so, the next cycle is initiated otherwise the process may come to an end.
Multivariate calibration methods (based on more than one response) offer an advantage of improved selectivity over univariate (one response) calibration methods. Multivariate calibration approaches permit more selective quantification of analyte (detergent) in complex samples (in presence of potential other fluorescent species such as lint, dirt, and others). Multivariate analysis has been widely used in chemistry. One aspect of the present invention is that multivariate analysis here is used to aid the dynamic control of the wash and rinse cycles. An exemplary method disclosed in this invention provides an array of photodetectors responsive to different spectral ranges of fluorescence and scatter from water solution. The sensor is provided that may include photodiode elements that are specifically designed to be optically responsive to different spectra ranges of fluorescence and scatter and applicable for multivariate analysis of fluorescence and scatter signals, and that would otherwise not be needed as part of a simple, but less accurate analysis. An example of such multiwavelength-response photodiode array is an array available from Texas Advanced Optoelectronic Solutions (USA).
Multivariate analysis methods include principal components analysis (PCA) that can be used to extract the desired descriptors from the dynamic data. PCA is a multivariate data analysis tool that projects the data set onto a subspace of lower dimensionality with removed co-linearity. PCA achieves this objective by explaining the variance of the data matrix X in terms of the weighted sums of the original variables with no significant loss of information. These weighted sums of the original variables are called principal components (PCs). Upon applying the PCA, the data matrix X is expressed as a linear combination of orthogonal vectors along the directions of the principal components:
X=t1pT1+t2pT2+ . . . +tApTK+E (Equation 1)
where ti and pi are, respectively, the score and loading vectors, K is the number of principal components, E is a residual matrix that represents random error, and T is the transpose of the matrix. Prior to PCA, data was appropriately preprocessed. The preprocessing included auto scaling.
To ensure the quality of the dynamic data several statistical tools may be applied. These tools are multivariate control charts and multivariate contributions plots. Multivariate control charts use two statistical indicators of the PCA model, such as Hotelling's T2 and Q values plotted as a function of combinatorial sample or time. The significant principal components of the PCA model are used to develop the T2-chart and the remaining PCs contribute to the Q-chart. The sum of normalized squared scores, T2 statistic, gives a measure of variation within the PCA model and determines statistically anomalous samples:
T2i=tiλ−1tiT=xiPλ−1PTxiT (Equation 2)
where ti is the ith row of Tk, the matrix of k scores vectors from the PCA model, λ−1 is the diagonal matrix containing the inverse of the eigenvalues associated with the K eigenvectors (principal components) retained in the model, xi is the ith sample in X, and P is the matrix of K loadings vectors retained in the PCA model (where each vector is a column of P). The Q residual is the squared prediction error and describes how well the PCA model fits each sample. It is a measure of the amount of variation in each sample not captured by K principal components retained in the model:
Qi=ei eiT=xi(I−Pk PkT)xiT (Equation 3)
where ei is the ith row of E, and I is the identity matrix of appropriate size (n×n).
Other multivariate analysis methods are also available, and may include, for example, pattern recognition techniques such as hierarchical cluster analysis (HCA), soft independent modeling of class analogies (SIMCA), and neural networks.
A spectral analysis of 13 detergents was performed in absorbance and fluorescence modes. Absorbance measurements were performed using detergent samples at 500 ppm on a benchtop diode array spectrophotometer (Hewlett Packard 8452A). Fluorescence measurements were performed using a 355 nm excitation. Fluorescence of samples (500 ppm of detergents) was measured using a portable fiber-optic spectrofluorometer (Ocean Optics ST2000). It was found that when excited at 355 nm, all 13 tested detergents produced detectable fluorescence. Based on emission spectra of the tested detergents, it was determined that the range from about 300 nm to about 600 nm should be applicable for determination of fluorescence from all detergents. Similarly, experimentally determined absorbance spectra (1-cm path length) of the detergents indicate the presence of enough ultraviolet absorbance for quantization of the detergents.
Analysis of multiple detergent concentrations was also performed to demonstrate the applicability of analytical fluorescence tools.
Analysis of spectral properties of water samples was also performed during a wash and two rinse cycles of clothes in a PROFILE brand washing machine (available from General Electric of Fairfield, Conn.) using XTRA brand laundry detergent (available from Church & Dwight Co., Inc. Princeton, N.J.).
Analysis of spectral properties of water samples was further performed during a wash and several rinse cycles of clothes in a vertical axis and horizontal axis washing machines.
UV LEDs were obtained from recently available commercial sources and were emitting at 365 nm. A photodiode was obtained from a commercial source. A sensor system was built and measurements were performed with a complete system that included a 365-nm UV LED and a photodiode.
An integrated array of photodiodes that are responsive to four spectral ranges of light was used to detect fluorescence from detergents in water. This response was provided by having optical bandpass filters in front of each photodiode element in the array. The spectral ranges covered blue, green and red light, as well as full spectrum of light from the light source.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
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