Leak detection tape

Details Leak detection tape Leak detection tape

1999-05-10

2001-01-16

Lieu, Julie (Department: 2736)

Communications: electrical

Condition responsive indicating system

Specific condition

C340S604000, C073S040000, C604S361000

Reexamination Certificate

active

06175310

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an elongated flexible tape having flat, spaced conductors for detecting liquid leaks, and a method for using the same.
2. Description of the Prior Art
Water and other liquid leaks have long been a problem to homeowners. For example, many homes have air conditioning units with air handlers that are located in the home's attic. These units include evaporators that generate large quantities of condensation that must be collected, and removed through a small drain pipe. It is quite common for the drain pipes to become clogged, and cause the condensation to back up and overflow onto the floor of the attic. Since the residents of the home typically do not check the condition of the unit, the overflowing condensate is usually not detected until it does substantial, costly damage to the ceilings of the rooms below. Hot water heaters are another example of devices that are prone to leak, but which leaks typically go unnoticed until substantial water damage has been done. Likewise, leaky basements and roofs are also apt to go unnoticed until substantial damage has been done to the floor, roof, furnishings and other items in the house.
To address this problem, numerous leak detection systems and methods have been proposed. For example, many electrically operated leak detection devices are available that sense the presence of water or liquid by detecting a change in electrical resistance or impedance between two or more conductors that are exposed to the liquid. While these devices generally work well, they suffer from a number of limitations that inhibit their use in certain applications. For example, in circumstances where it is desirous to monitor a large area, such as a roof or a perimeter of a basement, present systems require the use of time domain reflectometry (TDR), or some other technique, to detect the location along the pair of conductors in the monitored area where a leak occurs. This is because a simple short circuit detection circuit is not capable of detecting the location along a pair of conductors where a short circuit created by water or other conductive liquid bridging the conductors occurs. TDR works by sending a signal along the conductors and detecting the reflection of the signal that is generated at the point where an impedance change occurs between the conductors. Through phase analysis of the reflected signal, the distance along the conductor where a conductive liquid that is present can be determined. While TDR based systems work well, they are much more costly than simple short circuit detectors.
Another problem with previous electrically operated leak detection systems is that they are typically only effective in sensing fairly large quantities of water or other liquid. This is because they employ spaced apart conductors that are too thick, and essentially act as a dam to small quantities of water that prevent the water from traveling past a first conductor into contact with a second conductor, and thereby triggering the leak detector. While this problem may not be a concern in applications where only large quantities of leaking liquid need to be detected, it is a notable concern in numerous other applications, including those discussed previously where water leaking from evaporation units, hot water heaters, toilets and other fixtures, basements and roofs, is to be detected. In these applications, it is imperative that any water leakage be detected as soon as possible to minimize the likelihood that serious water damage will occur. It is therefore desirous that even a few drops of water be detected by the leak detection system so that an individual will be given the earliest warring possible that a leakage problem has developed.
SUMMARY OF THE INVENTION
The present invention overcomes the aforementioned limitations of previous leak detection systems through provision of a flexible, flat self-adhesive conductive tape that can be easily applied to any surface to be monitored for water or other liquid leaks, and connected to any suitable type of conventional electrically operated leak detector. First and second spaced parallel conductors are disposed on a top surface of the tape that run longitudinally along the length thereof. The conductors are spaced from one another by a small distance to insure that only a small quantity of water or other conductive liquid is necessary to bridge the gap between the conductors, and create an electrical short circuit or substantial impedance or resistance reduction between the two. In addition, the conductors and the tape are preferably as flat as possible to insure that liquid can freely flow transversely across them without being impeded thereby. Both of these features of the invention combine to insure that the detector tape can be used in combination with the leak detector to sense even very small quantities of liquid, and thereby generate an early warning of a leak condition before extensive damage results.
Another notable feature of the invention is the provision of visible indicating means on the tape which is used to identify the location along the tape where water or other leaking liquid has come in contact therewith. The indicating means may comprise a surface on the tape that changes color or stains when contacted with water, or may be a pattern of water soluble markings that smear or run when contacted wit water. This is advantageous for a number of reasons. First, it enables one or more long runs of tape to be used with a single simple detector for monitoring one or more large areas, such as the roof and basement of a house, without requiring use of an expensive TDR sensing device to locate the source of a leak. Second, the indicating means makes it easy to quickly spot the source of one or more leaks, regardless of their size. In addition, the liquid responsive indicating means acts as a telltale to mark areas along the detection tape where leaks may have occurred for a brief period of time, such as during a heavy rain shower, but have gone unnoticed because the residence's occupants were not home at the time of the leak to observe the alarm condition. While circuitry can obviously be built into a leak detection system that keeps records of past alarm conditions, the use of the visible indicating means eliminates the need for such circuitry, thus once again enabling a simple, inexpensive short circuit detector to be employed with the detection tape.


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