MOISTURE DETECTION AND ESTIMATION WITH MULTIPLE FREQUENCIES

Abstract

A method of moisture detection and estimation in an absorbent article with use of multiple frequencies is provide that comprises: applying, by capacitive coupling, drive signal of multiple frequencies to a drive electrode in the absorbent article; sensing, by capacitive coupling, sense signal of the multiple frequencies from a sense electrode in the absorbent article; detecting the first wetness event in the absorbent article with use of sense signal of a frequency of the multiple frequencies; and detecting the saturation of the absorbent article with use of sense signal of another frequency of the multiple frequencies.

Claims

1. A method of moisture detection and estimation in an absorbent article with use of multiple frequencies, comprising: applying, by capacitive coupling, drive signal of multiple frequencies to a drive electrode in the absorbent article; sensing, by capacitive coupling, sense signal of the multiple frequencies from a sense electrode in the absorbent article; detecting the first wetness event in the absorbent article with use of sense signal of a frequency of the multiple frequencies; and detecting the saturation of the absorbent article with use of sense signal of another frequency of the multiple frequencies.

2. The method according to claim 1, wherein the detecting the first wetness event comprises: detecting the first wetness event in the absorbent article when a sharp jump in amplitude is determined in the sense signal of the frequency that changes beyond a threshold height within a period shorter than a threshold period.

3. The method according to claim 1, wherein the detecting the first wetness event comprises: detecting the first wetness event in the absorbent article when a gradual upslope in amplitude is determined in the sense signal of the frequency that changes beyond a threshold height.

4. The method according to claim 1, wherein the detecting the saturation comprises: determining in the sense signal of the other frequency a difference in amplitude from the first wetness event; and detecting the saturation when the difference in amplitude is greater than a threshold amount.

5. The method according to claim 4, wherein the threshold amount is changed depending on the orientation of the absorbent article.

6. The method according to claim 1, wherein the applying drive signal of multiple frequencies comprising: applying a periodic drive signal that is swept in a period over the multiple frequencies.

7. The method according to claim 1, wherein the sensing sense signal of the multiple frequencies comprises: determining, for each of the multiple frequencies, sense signal by using a bandpass filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The various preferred embodiments of the present invention described herein can be better understood by those skilled in the art when the following detailed description is read with reference to the accompanying drawings. The components in the figures are not necessarily drawn to scale and any reference numeral identifying an element in one drawing will represent the same element throughout the drawings. The figures of the drawing are briefly described as follows.

[0016] FIG. 1 illustrates an exemplary disposable absorbent article in an exploded perspective view, according to an embodiment of the present disclosure.

[0017] FIG. 2 illustrates an exemplary disposable absorbent article with four spaced-apart conductive lines being provided on the top side of the substantially liquid impervious layer, according to an embodiment of the present disclosure.

[0018] FIG. 3 illustrates an exemplary pod that may be used with the exemplary disposal absorbent article as illustrated in FIG. 2 for moisture detection and estimation of the absorbent article, according to an embodiment of the present disclosure.

[0019] FIG. 4 illustrates amplitude vs. time graph of an exemplary drive signal Sd according to an embodiment of the present disclosure.

[0020] FIG. 5 illustrates amplitude vs. time graphs G showing the sense signals Ss of various frequencies, according to an embodiment of the present disclosure.

[0021] While the features described herein are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to be limiting to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 illustrates an exemplary disposable absorbent article in an exploded perspective view. As illustrated, a disposable absorbent article 100 primarily consists of an absorbent core 140 sandwiched between a liquid pervious layer 120 and a substantially liquid impervious layer 160.

[0023] As illustrated in the exemplary diaper of FIG. 1, a disposable absorbent article 100 has a substantially liquid impervious layer 160 configured to prevent the bodily exudates or excretions absorbed and retained in the absorbent core 140 from wetting articles, such as bed sheets and undergarments, which contact the disposable absorbent article 100. On top of the layer 160 is disposed an absorbent core 140 made of a superabsorbent material. On top of the absorbent core 140 is a liquid pervious layer 120 that is joined to the layer 160 in an assembled state of the disposable absorbent article and is placed next to the skin of the user when in use. Additional structural features such as additional layer(s), elastic members and fastening means for securing the article in place, such as tape tab fasteners, may also be included.

[0024] The liquid pervious layer 120 is configured to be penetrable by bodily exudates and excretions in a direction into the absorbent core 140 to enable them to be absorbed and retained in the underlying absorbent core 140. It is appreciated that the layer 120 may be made of a variety of liquid pervious materials, e.g. nonwoven fabric.

[0025] The absorbent core 140 is made up of hydrophilic superabsorbent polymers (SAP) and fibrous material, as a non-limiting example. The polymers act like tiny sponges that retain many times their weight in liquid.

[0026] The substantially liquid impervious layer 160 is made of a material substantially impervious to liquids. As an example, the substantially liquid impervious layer 160 may be manufactured from a thin plastic film, although other liquid impervious materials may also be used. As described above, the substantially liquid impervious layer 160 is configured to prevent the bodily exudates or excretions absorbed and retained in the absorbent core from wetting articles, such as bed sheets and undergarments, which contact the diaper.

[0027] As illustrated in the exemplary diaper of FIG. 1, the layers 120 and 160 are coextensive and have generally larger dimension, in length and/or width, than the absorbent core 140.

[0028] In order for moisture detection and estimation, in particular to detect the presence and/or amount of the bodily exudates or excretions in a disposable absorbent article, in particular in its absorbent core, a number of (e.g. at least two) spaced-apart conductive lines are provided as electrodes on the top side (i.e. the side facing the absorbent core) of the substantially liquid impervious layer along the length of the disposable absorbent article, in an embodiment of the present disclosure. In FIG. 2, an exemplary disposable absorbent article 100′ is depicted with four spaced-apart conductive lines 180′ being provided on the top side of the substantially liquid impervious layer 160′, as an example. The spaced-apart conductive lines 180′ in the disposable absorbent article 100′ operate in cooperation with a pod 200 (to be described below in reference to FIG. 3), for moisture detection and estimation of the absorbent article 100′.

[0029] As illustrated in FIG. 3, an exemplary pod 200 primarily consists of two halves 220 and 240 that are pivotably coupled to each other with a pivotal connection 260. At least one of the two halves 220 and 240 is provided with a number of (e.g. at least two) contacts 280 or 280′ on its inner side (i.e. the side facing the other half). As a non-limiting example, both the two halves 220 and 240 have each a number of contacts 280 or 280′ on their respective inner side, as illustrated in FIG. 3. In the example as illustrated in FIG. 3, there are four (the same number as the conductive lines 180′ as illustrated in FIG. 2) contacts 280 and 280′ on the two halves 220 and 240 respectively.

[0030] In operation, the pod 200 as illustrated in FIG. 3 is clipped on a disposable absorbent article (e.g. 100′ as illustrated in FIG. 2) at one of its waist end edges and coupled to the conductive lines (e.g. 180′ in FIG. 2) with the contacts 280 and/or 280′ on the pod 200. In use, the bodily exudates or excretions absorbed and retained in the absorbent core (e.g. 140′ in FIG. 2) of the absorbent article will cause at least two of the spaced-apart electrodes (conductive lines, e.g. 180′ in FIG. 2) to be connected to each other, and thus the pod 200 can detect the presence and/or amount of the exudates or excretions in the disposal absorbent article (e.g. 100′ in FIG. 2) by applying a drive signal to at least one of the electrodes (the drive electrode) and sensing a sense signal from at least another one of the electrodes (the sense electrode).

[0031] As mentioned above, in a disposable absorbent article the spaced-apart conductive lines may be provided on any layer, on which at least two of the spaced-apart conductive lines, with the aid of the bodily exudates or excretion absorbed and retained in the disposable absorbent article, will connect to each other, which in turn enables the detection of the presence and/or amount of the exudates or excretions in the disposal absorbent article.

[0032] It is to be noted that the pod 200, in particular its contacts 280 and 280′, cannot make physical contact with the electrodes (conductive lines, e.g. 180′ in FIG. 2) on the disposable absorbent article (e.g. 100′ in FIG. 2) due to the presence of outermore material or layer(s) of the article, e.g. material or layer(s) further away from the absorbent core, with respect to the conductive lines, e.g. the substantially liquid impervious layer (e.g. 160′ in FIG. 2) and/or the liquid pervious layer (e.g. 120′ in FIG. 2). That is, in use, the pod 200 is capacitively coupled to the electrodes (conductive lines, e.g. 180′ in FIG. 2) by aligning its contacts 280 and 280′ with the conductive lines (e.g. 180′ in FIG. 2) and placing them in close proximity.

[0033] As mentioned above, an absorbent article such as a diaper is provided with at least two electrodes, i.e. at least one drive electrode and at least one sense electrode, in an embodiment of the present disclosure. Further, a pod is provided to make capacitive contact with these electrodes in the absorbent article, that is, the pod touches the electrodes but does not make physic contact with electrodes.

[0034] In an embodiment of the present disclosure, in order for moisture detection and estimation, a drive signal is applied to a drive electrode in the absorbent article, and in response, a sense signal is sensed from a sense electrode in the absorbent article. It is appreciated that the drive signal cannot be a DC signal because of the capacitive coupling.

[0035] At a first wetness event in an absorbent article a significant rise (e.g. a sharp jump or a gradual upslope) in amplitude presents in a sense signal of a low frequency (e.g. around 10 kHz), which however does not change much either before or after the first wetness event even though further wetness events occur in the absorbent article later.

[0036] Further, a sense signal of high frequency e.g. ranging from 70 kHz-500 Khz gradually increases in its amplitude as more and more wetness events occur in the absorbent article.

[0037] Based on the above, multiple frequencies may be used for moisture detection and estimation of an absorbent article in an embodiment of the present disclosure.

[0038] In particular, in an embodiment of the present disclosure the drive signal that is to be applied to the drive electrode of the absorbent article may be a periodic signal that is swept with the same amplitude in a period over a range of frequencies f1, f2, . . . , fm, such as e.g. 5 kHz, 10 kHz, . . . , 3 MHz. For example, in a period the drive signal Sd is a sinewave signal that is swept over frequencies ranged from f1 to fm such as e.g. 5 kHz to 3 MHz, with each frequency being of the same amplitude and lasting for the same time interval e.g. 10 ms. In particular, in a period, the drive signal 100 is a sinewave signal of 5 kHz from Oms to 10 ms, then a sinewave signal of 10 kHz from 10 ms to 20 ms, then a sinewave signal of 15 kHz from 20 ms to 30 ms, . . . , finally a sinewave signal of 3 MHz from 1.99 s to 2 s, and then repeats periodically, as an example. It is appreciated that between different frequencies there may exist time interval with no signal. For example, the drive signal may be a sinewave signal of 5 kHz from 0 ms to 10 ms, then 0 (i.e. no signal) from 10 ms to 20 ms, then a sinewave signal of 10 kHz from 20 ms to 30 ms, then 0 from 30 ms to 40 ms, then a sinewave signal of 15 kHz from 40 ms to 50 ms, . . . , finally a sinewave signal of 3 MHz from 3.98 s to 3.99 s, then 0 from 3.99 s to 4 s, and then repeats periodically, as an example. As an example, FIG. 4 illustrates amplitude vs. time graph of an exemplary drive signal Sd according to an embodiment of the present disclosure.

[0039] In response to this drive signal Sd being applied to a drive electrode of an absorbent article, a sense signal 200 is sensed from a sense electrode of the absorbent article. It is appreciated that in response to a sinewave signal of a specific frequency being applied to a drive electrode of an absorbent article, a sinewave signal of the same specific frequency is sensed from a sense electrode of the absorbent article, but with a smaller amplitude.

[0040] By using bandpass filter at the sense electrode that is configured to allow only a specific frequency to pass through and to filter out all other frequencies, a sense signal may be obtained for each frequency. FIG. 5 illustrates amplitude vs. time graphs G showing the sense signals Ss of various frequencies, according to an embodiment of the present disclosure.

[0041] As an example, in FIG. 5 from up to down, the uppermost graph G1 illustrates the sense signal 200-1 of 5 kHz, the second uppermost graph G2 illustrates the sense signal 200-2 of 10 kHz, . . . , a graph Ga illustrates the sense signal 200-a of 5 a kHz, a graph Gb illustrates the sense signal 200-b of 5 b kHz, . . . , a graph Gm illustrates the sense signal 200-m of 5 m kHz, a graph Gn illustrates the sense signal 200-n of 5 n kHz, . . . , that are sensed from the sense electrode in response to the drive signal 100 as illustrated in FIG. 4 being applied to the drive electrode, where a, b, m, and n are integers.

[0042] In the embodiment as illustrated in FIG. 5, a first wetness event is assumed to occur at time t1, which causes the connection between the electrodes (the drive electrode and the sense electrode) in the absorbent article. In response to the first wetness event, a sharp jump in amplitude that changes beyond a threshold height Hj within a period shorter than a threshold period Tj may occur at or around t1 in a sense signal of a low frequency. This sense signal of the low frequency does not change in its amplitude much before and after this jump, even though further wetness events occur in the absorbent article later. It can be seen from FIG. 5 that a jump in amplitude of a height H within a period T appears around t1 in signal 200-a and the signal 200-a does not change in its amplitude much before and after this jump, as an example.

[0043] Based on the above, in an embodiment of the present disclosure, a sharp jump in amplitude that changes beyond a threshold height Hj within a period shorter than a threshold period Tj in a sense signal of a low frequency can be used to determine the first wetness event in an absorbent article.

[0044] It is to be noted that, the change in amplitude of the sense signal of a low frequency in response to the first wetness event might be smoother, e.g. a gradual upslope, In some circumstances, in which case a threshold height Hs greater than the threshold height Hj may be used to determine the first wetness event in an absorbent article. That is, in addition or alternatively to the sharp jump in amplitude as described above, a gradual upslope in amplitude with a height beyond a threshold height Hs in a sense signal of a low frequency may be used to determine the first wetness event in an absorbent article, in an embodiment of the present disclosure. As an example, in FIG. 5 an upslope in amplitude of a height H′ occurs around t1 in the sense signal 200-b that also does not change much before and after the first wetness event t1.

[0045] Based on the above, in an embodiment of the present disclosure, a periodic drive signal that is swept in a period over a range of frequencies is applied to a drive electrode in an absorbent article, and by using bandpass filter, a sense signal is sensed from a sense electrode in the absorbent article for each frequency in the frequency range. In order to determine the first wetness event, the sense signals of low frequencies e.g. around 10 kHz are checked for a sharp jump e.g. of a height beyond Hj within a period T shorter than Tj or for a gradual slop e.g. of a height beyond Hs in their amplitudes.

[0046] As mentioned above, the sense signal of low frequency, with which the first wetness event in an absorbent article is determined by checking a sharp jump or a gradual upslope in its amplitude, does not change in amplitude much after the sharp jump or the gradual upslope, and thus cannot be further used to estimate or detect the saturation in the absorbent article.

[0047] On the other hand, a sense signal of high frequency e.g. ranging from 70 kHz-500 Khz gradually increases in its amplitude as more and more wetness events occur in the absorbent article. Based on this, the sense signals of higher frequencies may be used to estimate or detect the saturation in the absorbent article after the first wetness event is determined, in an embodiment of the present disclosure.

[0048] It is understood that, after the first wetness event, further wetness events occur in the absorbent article. As further wetness events occur in the absorbent article, the sense signals of higher frequencies continue to increase in their amplitude gradually. In an embodiment of the present disclosure, in order to estimate or detect the saturation in the absorbent article, the difference in amplitude from the first wetness event (e.g. time t1 in FIG. 5) is determined in each of all sense signals of higher frequencies. Once the difference in amplitude from the first wetness event (e.g. time t1 in FIG. 5) is determined in any one of the sense signals of higher frequencies to be beyond a threshold amount Ts, the saturation is detected in the absorbent article.

[0049] As can be seen from FIG. 5, at time t2 the difference in amplitude from the first wetness event t1 is Dm2 in the sense signal 200-m, and is Dn2 in the sense signal 200-n. However, the differences in amplitude from t1 to t2 are all less than the threshold amount Ts in all the sense signals of higher frequencies.

[0050] Further, at time t3, the difference in amplitude from the first wetness event t1 is Dm3 in the sense signal 200-m, and is Dn3 in the sense signal 200-n. At this time, while the differences in amplitude from t1 to t2 are less than the threshold amount Ts in other sense signals of higher frequencies, the difference in amplitude of the sense signal 200-n from t1 to t2 is greater than the threshold amount Ts, which may be used as indication of the saturation in the absorbent article, according to an embodiment of the present disclosure. In an embodiment of the present disclosure, the sense signal 200n, in which a difference in amplitude from t1 greater than the threshold amount Ts is first detected, may be e.g. about 100 kHz.

[0051] Based on above, in an embodiment of the present disclosure, a periodic drive signal that is swept in a period over a range of frequencies is applied to a drive electrode in an absorbent article, and by using bandpass filter, a sense signal is sensed from a sense electrode in the absorbent article for each frequency in the frequency range. In order to estimate or detect the saturation in the absorbent article, the first wetness event, which is determined as described above with use of a sense signal of low frequency, is used as baseline, and the difference in amplitude from the first wetness event is compared to a threshold amount Ts in each of all sense signals of higher frequencies e.g. ranging from 70 kHz to 500 kHz, and whenever a difference in amplitude is determined to be greater than the threshold amount Ts, the saturation is detected in the absorbent article.

[0052] It is also appreciated that, the wetness spot changes in different orientations of the user wearing the absorbent article, which in turn results in different distances between the wetness spot and the pod. Therefore, in an embodiment of the present disclosure, the threshold amount Ts may be changed depending on the orientation of the user. For example, according to an embodiment of the present disclosure, a smaller threshold amount Ts is assigned to an orientation of user in which the wetness spot is further away from the pod.

[0053] As described above, in an embodiment of the present disclosure, multiple frequencies are used for moisture detection and estimation of an absorbent article. In particular, a low frequency is used to determine the first wetness event in the absorbent article, which is in turn used as a baseline for moisture or saturation estimation, while another high frequency is used to estimate or detect the saturation of the absorbent article. As mentioned above, low frequencies are checked for a sharp jump or a gradual upslope in amplitude that acts as indication of the first wetness event in the absorbent article. Then the differences in amplitude from the baseline of high frequencies are compared to a threshold amount in order to detect or estimate the saturation of the absorbent article.

[0054] Although the embodiments above have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.