US2668202A - Moisture responsive signaling device - Google Patents

Description

Feb. 2, 1954 a. D. KAPLAN MOISTURE RESPONSIVE SIGNALING DEVICE Filed Aug. 2, 1952 INVEN TOR. BENJAMIN D. KQPMN 1.

\ 4 I orne Patented Feb. 2, 1954 UFNFI TILED S TATE S FATE-N T O F -F'i CE MOISTURE'RE SPONSIVE SIGNAEINGDEVIGE Benjamin DrKaplan Bux-bank Galif.

Application August 2, 1952,SerialNo. 3021310 -9 laims. (Cl. 20.0--'.61".05')

This invention relates to signaling devices and more particularly to signaling devices adaptedto give a signal when affected by moisture.

Several-devicesoi the abovenature h-ave'been proposed for giving a signal when exposed to moisture "such as rain or partially conductive liquids in one form or another. For examplathe systems find'use in informing an attendant of the wettingof a-bed'or bed-clothes by them:- cupant thereof. The devices have generally compriseda pair of flexible flat coplanar'electrodes mounted on or inibedded in an insulative pad member Whichmay be placed in aninfants bed, or ina location where the presence of moisture isdesired'to be detected. Theelectrode-surface edges are'disposedjadjacent one another in such "a "manner 'that'a conducting liquid on the pad surface will electrically 'bridge and short circu'itthe electrodes to "complete "apower circuit. The signaling mechanism itself, such as .a hell or light, .forexample, may be actuated by a'reiay in the power circuit. To increaseithe arearesponsive to the moisture, the electrodes have been interleaved in such a manner thatthe'short circuitine canbe effected at several diflerent portions on the pad member surface.

While these prior systems have been satisfactory 'to some extent, they have tended to be bulkyand cumbersome. Further, the'interleaving type electrode-design lengthens considerably the electrical path that'the current must follow. This is especially the case when the short circuit is efiected at apoint on the pad spaceda considerable distance from the electrode terminals. In the interests of flexibility and portability, the electrodes must necessarilybe'thin in their third dimension. This additional path length therefore offersa high resistance to current Iflow and consequently reduces the reliability of the device. Thus, for example, while theactual current flow between the electrodes necessary to actuate a relay is generally quite small, the conductivity of the actuating liquid may be so poor that its resistance in series with any additional resistance due to the interleaving electrode structure, is oftentimes sufficient to prevent the current from actuating the signaling mechanism.

An additional difficulty Withthese paststruc tures is that in order to insure that the electrode interleaving edges are insulated from one another, an appreciable space between these edges would have to be maintained. This is because these electrodes have in the past .taken the form of metal foil or conductive fiat strips glued or otherwise 'secured' tothepad member surface and thus subject to slippage "into contact with one another, especially "during the moulding or 2 securing'proeess. The effectiveness of the moisture pad is impaired by a "large space to be bridged by the liquid since the resistance path through the liquid is greatly increased.

It 'is an object of the present "invention, accordingly, to provide a moisture responsive device which is considerably more flexible and portable than has "characterized prior designed systerns, and yet *is extremely *reliable in its electrical operation.

More particularly'it i's an objecto'f the invention to provide "an improved "moisture responsive pad-of the type "described 'in'wh'ich the'electrical resistance "or current paths in the electrodes isminimized.

A further "object is to "provide a "signaling clevice in which "the electrode :array and pad is such as to render the system'many times more sensitive to moisture "than has been :achieved in the past.

These and other objects of the invention are attained "by providing what may be termed .a three dimensional typemoisture responsiveipa'ol in "contra-distinction to the ftwo dimensional prior systems in which the electrodes were coplanar. In general, the invention comprises a flexible fiat pad meniberl'hav'ing deposited on one surface thereof a conductingmaterial .constituting a first electrode o'irelativelylarge surface area. ZPortionsof this .letrodesurffaceare coveredby an insulatin-glmaterial. This insulating material .may be treated .with a salt bath such.that:anylliquidlfalling on it will -.be rendered at least partially conductive. The insulating material in .turn Ilhasdeposit-ed on itssurfacea conducting material constituting a second elec-- trode. The electrodes. rethu sp d par y a thickness corresponding to .the thickness of the insulating material, in substantially parallel planes .when thepad. :member .is :lyingflat. The portions of thelfirst.electrodesurfaeenot covered by .the insulating material are exposed so that any moisture .on :the .pad member surface will readily effect a=short oircuit between the electrodes.

:In a specific :embodiment, zthe insulating lma terial may take f-theiorm .of a zdetachableeec- 0nd flexible pad .member upon which the second electrode:maybeeasily deposited. .On the other hand, .the insulating material may constitutean .insulative coating spread directly .on portions of the Ifirst electrode surface, the second electrode surfacebeing deposited on this coating tofiorm an integral unit.

With either .of these arrangements "it "will "be seen :at once that the electrical path -resistance through *the electrodes is materially reduced be- 3 cause of the infinite number of parallel paths the current can follow on each electrode to the terminals of the pad member. Furthermore, the feature of depositing the electrodes directly on the pad member and insulative material provides a device which is extremely flexible and portable.

A better understanding of the invention will be had by referring to the accompanying drawings, in which:

Fig. 1 shows in perspective one embodiment of the moisture pad and electrode arrangement;

Fig. 2 is an enlarged edge view of the pad member of Fig. l as an assembled unit;

Fig. 3 illustrates a top view of another embodiment of the invention together with a schematic diagram of the alarm circuit;

Fig. 4 is a cross-sectional view as seen along the line 44 of Fig. 3;

Fig. 5 shows in perspective still another form the moisture pad may take in accordance with the invention.

Referring to the drawings, there are shown signaling devices particularly suited for indicating the wetting of a bed by an infant, for example. For this purpose, it is desirable that the moisture responsive pad be light, rugged, and extremely flexible so that when it is laid flat in a bed or crib its presence will not be uncomfortable to the occupant. While features of the present invention render the signaling device as shown in the drawings particularly suitable for this particular use, the invention is not to be thought of as limited solely to this application.

In Fig. l the device is shown as comprising a flexible pad member Ii! having a first electrode I I on its upper surface as shown. Although elec trode II is preferably formed by depositing conductive material directly on the pad member surface, it may, instead, constitute a flexible metal foil secured to or imbedded in the surface of the pad. A metallic terminal I2 secured to an extension II of electrode II passes through pad member Ill and is adapted to be electrically connectetd to a cooperating terminal I2 on a detachable cord support I3.

A second pad member I4 made of insulative material adapted to cover partially electrode II has deposited or imbedded on its upper surface a second electrode I5 as shown. Electrode I5 also includes an extension [5' to which a metallic terminal I B is secured and adapted to extend through pad I4 and a cooperating opening in pad Ill (not shown) to a second terminal I5 on the cord support I3. Pad member I4 also includes at each of its four corners snap means cooperable with corresponding snap sockets on the corners of the lower pad member III. This arrangement permits the pad members to be secured together and corresponding electrodes to be connected to a cord extension leading from cord support I3. Cord extension I! terminates in a jack I8 which may be conveniently plugged into an alarm circuit. Clearly, other means for securing the two pad members Ill and I4 may be employed. The feature of making the two pads separable facilitates cleaning the electrode surfaces.

One or more openings I9 passing through the second electrode i5 and pad member I4 are provided so that only a portion of the first electrode surface II is covered when the various elements are assembled. Portions of the first electrode II are thus exposed through openings I9 when pad I I is covering the pad I0.

Fig. 2 shows the assembled unit from one end in exaggerated dimensions, the same reference numbers designating the corresponding elements shown in Fig. 1.

In operation, the assembled unit may be laid fiat in an infants crib under the main sheet for example, and the extension cord ll connected to a suitable alarm circuit. Wetting of the bed clothes or diapers by the infant will thus moisten the upper surface of the electrode I5 and the exposed surface of electrode I I through openings I9 providing a conducting path between the electrodes. This action completes a power circuit which may contain a relay to operate a buzzer or light and inform an attendant of the wetting, .or awaken the child.

Fig. 3 discloses such a circuit arrangement in schematic form connected to a modified type of moisture responsive pad. In this embodiment, a flat pad member 30 similar to pad ID in Fig. 1 has a first electrode 3| deposited on its surface. Electrode 3| is partially covered by an electrically insulative coating 32, such as a suitable insulating paint, as shown in the cross-sectional view of Fig. 4. A second electrode 33 is deposited on the surface of the insulative paint, the electrodes 3| and 33 being respectively provided with extensions 3| and 33' for connection to a suitable signaling circuit. A plurality of openings 34 in the electrode 33 and insulative coating 32 leave substantial portions of the surface of electrode 3| exposed such that the electrodes 3| and 33 are readily short circuited by any moisture or liquid falling on the surface of pad member 3|].

The associated power circuit may comprise a battery 35, relay coil 36 and switch 31 connected in series between the electrodes 3| and 33 as shown. Operation of the relay arm 36 serves to connect a signaling element, such as a light or buzzer 38, across the battery 35 by closing contact 39.

With this arrangement, and switch 31 closed, wetting of the pad member 30 will electrically connect the electrodes 3| and 33. Current from battery 35 will then flow around the circuit, operating relay 36 to close contact 39 and actuate the signaling element 38.

Fig. 5 discloses yet another form the invention may take. In this embodiment a flexible pad member 58 of insulating material has a first electrode 5| deposited or otherwise secured to one surface of the pad. A second electrode 52 is similarly applied to the opposite surface of the pad. As in Figs. 1 and 3, suitable electrode extensions 5| and 52 may b provided for connection to a suitable alarm circuit 53.

A plurality of openings 54 extending through both electrodes 5| and 52 and pad member 50 permit any moisture or liquid to electrically short circuit electrodes 5| and 52 when the pad member is lying on a bed sheet or mattress. This action obtains because of the absorbing nature of the sheet or mattress which serves to moisten the bottom electrode 52 from moisture passing through the openings 54.

In the various forms of the invention as illustrated in Figs. 1 to 5, the flexible pad member may comprise poly-vinyl chloride, known under the trade name of Vinylite. This material is highly flexible and has good electrical insulating properties. The electrodes themselves may comprise silver, deposited directly on the surface of the Vinylite. A suitable screening material may be used when applying the insulative paint and second electrode to the pad member in Fig. 3 to provide the openings 34.

It will be appreciated that the embodiments disclosed in Figs. 1 to 5 provide a highly flexible and rugged moisture-responsive signaling device. Further, the reliability of operation of the pad member in the presence of only small quantities of moisture is greatly enhanced due to the extremely close spacing of the electrodes. This close spacing is possible because of the three dimension construction feature wherein the electrodes are separated only by the thickness of the insulating material.

By providing a plurality of registering openings in the second electrode and th insulative layer thus exposing portions of the surface of the first electrode, the electrical bridging of the two electrodes by any moisture laden bed clothes or liquid on the pad surface is readily effected. in the case of the wetting by an infant, the salt in its urine is sufficient to provide a partially conducting liquid. On the other hand when the insulating material has been treated in a salt bath for example, any liquid such as rain will be rendered conductive upon falling on the pad. It should be understood of course that openings of any suitable configuration may be employed. The circular and elongated slot openings depicted in Figs. 1 and 3 respectively are shown merely by way of example. It is preferable to have the openings distributed over a large area of the pad surface so that moisture falling anywhere on the surface will eifect the short circuit.

It is also to be appreciated that the particular electrode arrangement provides a low resistance path from the point where the electrodes are shorted to the terminal points on the pad. This is because the whole surface of each pad respectively is utilized to conduct current to the pad terminals. Thus each pad surface effectively provides an infinite number of paths in parallel leading to the respective terminal. Also, these pads do not necessitate the use of molds or dies in their manufacture.

Various modifications within the spirit of the present invention will readily occur to those skilled in the art. Thus, while snap means have been disclosed in Fig. 1 for assemblying the various elements, any other suitable fastening means may be employed. For example, the extension cord may be directly secured to the electrodes by any suitable connecting means. Also, it is not necessary that the respective pads be fastened together; one may simply rest flat on top of the other. Further, the electrodes may constitute any type of flexible conducting material secured to or imbedded in the insulative surfaces, such as metal foil for example. Any suitable alarm circuit or responsive mechanism may also be substituted for the circuit of Fig. 3 such as a sensitive electronic circuit wherein the sensitivity of the device may be greatly increased by feeding the signal to the control grid of a vacuum tube.

Moreover, while the apparatus has been described in detail with reference to a signaling device for indicating the wetting of a bed, the invention has many other useful applications. For example, it may be used to actuate window or door closing mechanisms in response to rain drops falling on the pad member.

The invention therefore is not to be thought of as limited to the precise embodiments disclosed.

I claim:

1. A moisture responsive device comprising a flexible pad member made of electrical insulating material, a first electrode comprising a continuous layer of electrically conducting material on one surface of said pad member, and a second electrode containing a plurality of openings therethrough on the opposite surface of the pad member whereby the first and second electrodes are spaced apart by said pad member in substantially parallel planes when the pad member is lying flat.

2. A device according to claim 1, in which said electrodes comprise conductive metal foil secured to the opposite surfaces of said pad member respectively.

3. A signaling device comprising a flexible pad member, a first electrode deposited on one surface of the pad member, electrical insulating means comprising an insulative-coating covering portions of said first electrode, a second electrode deposited on only those portions of the insulative coating covering the first electrode, whereby the portions of the first electrode not covered by the insulative coating are exposed.

4. A moisture responsive device comprising in combination: a first flexible pad member, a first electrode on at least one surface of the pad member, a second flexible pad member made of electrical insulating material and containing a plurality of openings therein distributed over a substantial area of the second pad member, a second electrode covering said second pad member and containing openings registering with the first mentioned openings, means for securing the second pad member to the first pad member whereby the first and second electrodes are spaced apart by said second pad member and portions of the first electrode surface are exposed through said openings.

5. A device according to claim 4, in which said electrodes are imbedded in said pad members.

6. A moisture responsive device comprising a flexible pad member, a first electrode deposited on one surface of the pad member, electrical insulating means coated over portions of the first electrode whereby a plurality of openings exposing other portions of the first electrode surface are distributed over a substantial area of the surface, a second electrode deposited on only those portions of the insulative coating means covering the first electrode surface, whereby said electrodes are electrically insulated from each other by said insulative coating means.

'7. A moisture responsive device comprising a first electrode made of conductive material in the form of a fiexible pad, a second electrode similar in dimensions to said first electrode and containing a plurality of openings therethrough extending over a substantial portion of its area, said second electrode being adapted to lie over said first electrode, and electrical insulating means disposed between said electrodes.

8. A device according to claim 7, in which said first electrode comprises a continuous conductive layer, conducting portions thereof lying directly beneath said openings in the second electrode.

9. A device according to claim 8, in which said insulating means contains a plurality of openings registering with the openings in said second electrode whereby said conducting portions are exposed.

UNITED STATES PATENTS Name Date Van Guilder Aug. 5, 1930 Number

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