Moisture detector

A compressed dehydrated cellulose sponge wafer has conductive plates attached to opposing faces. A bridging conductor electrically connects the two plates together upon swelling of the wafer responsive to its contact with moisture. One edge of the sponge is treated with adhesive so as to form a hinge. The wafer opens like a book upon contact with moisture forcing the extending plates into contact.

CROSS REFERENCE TO RELATED APPLICATIONS 
None. However, applicants filed two Disclosure Documents which are 
Disclosure Document No. 074,588 filed on Sept. 27, 1978 and Disclosure 
Document No. 074,486 filed on Sept. 25, 1978, which documents concern this 
application. 
BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to electrical alarms which are actuated by the 
presence of moisture. 
(2) Description of the Prior Art 
In modern homes expensive carpets are often laid above concrete floors. 
Also, often hot water heaters are located near the center of the house so 
that they are near bathrooms and the like. When leaks occur in this or 
other water using applicances, the water can ruin the carpets upon the 
floor. 
Previous workers have designed alarms to detect the moisture in this and 
similar situations. The previous workers have suggested using an expansion 
material, which upon expansion, would close electrical contacts. Normally, 
the expansion material was in a confined space so that its expansion 
pushed one electrical contact against the other by compression. SHU, U.S. 
Pat. No. 3,562,731, ANDRESEN U.S. Pat. No. 2,423,367 and UHLIG U.S. Pat. 
No. 3,200,388 disclose such detectors. 
Other alarm systems for the home have received extensive development. 
Specifically, fire and smoke alarms have been developed to respond to a 
change in conditions as detected to sound an alarm from a battery operated 
energy source. 
SUMMARY OF THE INVENTION 
(1) New and Different Function 
We have invented a new and improved method and means for detecting the 
presence of moisture and closing an electrical contact thereby. The prior 
art discloses excellent equipment whereby an alarm may be sounded once the 
moisture is detected and the contacts closed. 
We have discovered that a very inexpensive detector can be made using a 
compressed dehydrated cellulose sponge which expands upon contact with the 
water as is known to the prior art. However, we have invented covering the 
faces and at least one edge of a wafer or plate-like block of the sponge 
with an adhesive. By covering one edge with adhesive, this presents that 
edge from expanding. Therefore, when the bulk of the material expands, it 
causes the sponge to fan open much like a book or a clam. If a conductive 
plate attached to the faces extends beyond the hinge edge, the opening 
will force the extensions into contact with a certain leverage action 
which will increase the pressure by which the conductive plates are pushed 
together. 
Therefore it may be seen that we have invented a device which is very 
inexpensive to manufacture and also has an extremely long storage life. 
Thus it may be seen that the total function of our complete device far 
exceeds the functions of the individual elements, i.e., the adhesive, 
sponge, plates, etc. 
(2) Objects of this Invention 
An object of this invention is to detect the presence of water. 
Further objects are to achieve the above with a device that has a long 
shelf life, is sturdy, compact, durable, lightweight, simple, safe, 
efficient, versatile, ecologically compatible, energy conserving, and 
reliable, yet inexpensive and easy to manufacture, install, adjust, 
operate and maintain. 
Other objects are to achieve the above with a method that is versatile, 
ecologically compatible, energy conserving, rapid, efficient, and 
inexpensive, and does not require skilled people to install, adjust, 
operate, and maintain. 
The specific nature of the invention, as well as other objects, uses, and 
advantages thereof, will clearly appear from the following description and 
from the accompanying drawing, the different views of which are not scale 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, there may be seen a block or plate or wafer of 
compressed dehydrated cellulose sponge 10. Electrical conductive plate 12 
is attached to one face 14 of the sponge wafer 10. Opposing plate 16 is 
attached to the opposing face 18. As may be seen, the opposing plate is 
shown in the form of a wire. Also those with skill in the art will 
understand that the compressed dehydrated cellulose sponge is an expansion 
substance which expands upon contact with water. The wire, a portion of 
which forms the opposing plate 16, is bent upward through the sponge 10 to 
a head 20. As may be seen, the bridging portion 22 or that portion of the 
wire which bridges between the opposing plate 16 and the head 20 extends 
through a hole or opening or aperture 24 in the plate 12. There is a 
connection means 26 shown schematically which connects the connection 
device to battery 28 and alarm 30. As may be seen in FIG. 1, if moisture 
causes the sponge 10 to expand, it will force the plate 12 against the 
protuberance or head 20, which is a part of the bridging conductor and 
that this will make an electrical contact between the two plates, 
therefore, activating the alarm 30 as is well known in the art. 
Referring to FIGS. 2, 3 and 4 is shown another embodiment. In this 
embodiment, again a plate or wafer of compressed dehydrated cellulose 
sponge 32 is used. In this case, the first main face has an adhesive 34 
covering first main face 36, hinge edge 38 and opposing face 40. A water 
resistent adhesive is used. 
First conductive plate 42 is attached to the adhesive on the first face 36 
of the wafer 32. As it may be seen in the drawings, the first plate 42 is 
corrugated. We prefer to corrugate it because we prefer to use an 
extremely thin conductive plate herein, therefore, the corrugation give 
additional rigidity to the material. Also, it may be seen that the plate 
42 extends at area 44 beyond the hinge edge 38. 
On the opposing face 40, opposing electrical conductive plate 46 is 
attached by the adhesive 34. The opposing conductive plate may be planar, 
as seen in FIG. 2, or it also may be corrugated, as seen in FIGS. 3 and 4. 
It also extends in an area 48. It is necessary that the extension 44 of 
the plate 42 and the extension 48 of the plate 46 be greater than the 
distance across the hinge edge 38. Therefore, when the sponge wafer 32 
swells because of contact with moisture it will cause the edge of the 
shorter extension to bite into the surface of the longer extension. As 
illustrated, it may be seen that the first extension 44 is shorter than 
the opposing extension 48 and, therefore, the edge of the corrugations on 
44 will bite into the surface of the extension 48. Analysis will show that 
the plates are pivoted, i.e., the hinge edge 38 forms the fulcrum of a 
lever and, therefore, since the extensions 44 and 48 are of lesser length 
than the face 36 or opposing face 40 the force by which the plates are 
forced together is greater. Also, the extension 44 and 48 could be 
considered bridging conductors which electrically connect the two 
connector plates. 
Suitable connectors 26 are attached as by soldering to the plates 42 and 
46. 
As may be seen, plates 42 and 46 do not extend to the edge opposite the 
hinge edge 38, providing greater surface by which the wafer 32 may absorb 
water. Although the drawings show the adhesive to cover this portion of 
the wafer, under certain manufacturing conditions it might be that this 
portion of the wafer 32 would not be covered with the adhesive 34, thereby 
giving even greater access of the wafer to moisture on its supporting 
surface. 
Therefore, it may be seen that we have designed very simple, but very 
effective, moisture detectors which may be manufactured inexpensively and 
yet be very rugged and have a long shelf life. Because of ability to 
manufacture them so inexpensively, obviously it would be possible to use 
three or four of these beneath each water heater so as to be able to 
detect any moisture or leakage whatsoever in different locations around 
the water heater. It would also be possible to use them in attics to 
detect a leak in roofs or in basements to detect seeping water or to be 
used under sinks to detect drainage leaks. Because of the low expense and 
long shelf life, they could be used in many locations. 
In some embodiments, such as FIG. 1, the top plate could be in the form of 
a conductive paint such as an aluminum paint which is applied to the 
sponge as by dipping or spraying. 
As an aid to correlating the terms of the claims to the exemplary drawing, 
the following catalog of elements is provided: 
10 sponge 
12 plate 
14 face 
16 opposing plate 
18 opposing face 
20 head 
22 bridging portion 
24 aperture 
26 connection 
28 battery 
30 alarm 
32 wafer 
34 adhesive 
36 first face 
38 hinge edge 
40 opposing face 
42 plate 
44 area 
46 opposing plate 
48 opposing area 
The embodiments shown and described above are only exemplary. We do not 
claim to have invented all the parts, elements or steps described. Various 
modifications can be made in the construction, material, arrangement, and 
operation, and still be within the scope of our invention. The limits of 
the invention and the bounds of the patent protection are measured by and 
defined in the following claims. The restrictive description and drawing 
of the specific examples above do not point out what an infringement of 
this patent would be, but are to enable the reader to make and use the 
invention.