Electricity: circuit makers and breakers – Special application – Liquid or moisture responsive
Reexamination Certificate
2002-04-25
2004-09-07
Luebke, Renee (Department: 2833)
Electricity: circuit makers and breakers
Special application
Liquid or moisture responsive
Reexamination Certificate
active
06787718
ABSTRACT:
BACKGROUND
The electronics-industry is increasing the density of electronic components within electronic systems, and this increase results in increased heat that must be dissipated from the systems. The increased component density is fostered in part by increased signal frequencies that require a shorter signal path between components. Furthermore, increased component density increases the heat density, and reduces the space available in the system for cooling by forced air circulation.
Because of the increased heat, electronics manufacturers are more frequently using liquid to cool high-density electronic systems. Techniques for liquid cooled, high-density systems include immersion of the system in a liquid cooling bath, and mounting certain components of an electronic system on a liquid-cooled plate. Water is frequently used for the coolant, particularly deionized water. Other types of coolants are used as well.
Many of today's high-density electronic systems are also expensive. Leaks can quickly damage expensive electronic components if the coolant leaks into the electronic system, often resulting in a high-dollar loss and service interruption. Such damage can occur within a minute or two of coolant drops entering the electronics system.
Existing leak detectors are generally bulky devices designed for protection of buildings and large pieces of equipment against water leaks. The detectors generally operate by sensing a change in resistance between two electrically isolated wires contained in a sensor cable routed through an area to be protected. Water enters the sensor cable and forms a conductive path between the two wires, causing the resistance between the wires to drop. The resistance drop is detected by an ohm-meter-like device that forces a current between the wires and measures the voltage when a conductive path is formed.
Several types of sensor cables or elements are available, but they are not suitable for high-density electronics systems for several reasons, including size, and response parameters. One type of sensor cables uses water resistant insulation along its length, with discrete gaps in the insulation where the pair of wires are uninsulated and exposed to water. The gaps in the insulation are generally placed at regular intervals, with the separation interval ranging from several inches to several feet. The water must be at the location of the gap, and have sufficient depth to conductively bridge across the exposed wires. This type of sensor provides only a limited ability to sense water. The basic feature of this type of sensor makes it unsuitable for use in small electronics systems because the water might not collect at a gap in the insulation, and the sensor would not be activated. Another type of sensor uses a polyester wicking insulation to separate and protect the sensor wires, which are spaced about one-quarter of an inch apart. However, the size and physical characteristics of the existing wicking insulated sensor elements makes them unsuitable for high-density electronics systems. For example, they are more than one-inch wide, which is too wide to be routed among the small spaces available in high-density electronics systems. They do not have an optimal response profile for sensing the presence of water to protect electronics systems, including response time and distinguishing between high humidity and water drops. Furthermore, they do not have an acceptable level of sensitivity to the deionized water commonly used in cooling systems of electronic systems.
In view of the foregoing, there is a need in the art for a sensor that can quickly detect the presence of a liquid in an electronics system.
SUMMARY
In one embodiment of the invention, an elongated sensor element can detect the presence of a liquid in an electronics system. The sensor element includes a pair of adjacent electrical conductors, and a liquid permeable material that when dry electrically insulates the conductors, and when wet with a liquid at any point along the length of the conductors allows electric coupling of the conductors. The liquid permeable material may be arranged to wick the liquid into the sensor element, and the wicked liquid may electrically couple the conductors.
Such an elongated sensor element can quickly sense a liquid at any point along its length, and is suited for placement in the small spaces of a liquid cooling, high-density electronics system. A liquid is quickly sensed in part because any liquid proximate to the sensor element is wicked into the sensor element without waiting for the liquid itself to bridge the adjacent electrical conductors. Consequently, such an elongated sensor element is able to quickly sense the presence of leaks to limit possible damage to electronic components.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.
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patent: 6580013 (2003-06-01), Belloso
Water Alert Sensor Cable, Dorlen Products, Milwaukiee, WI, Principle of Operation and Construction, p. 3, SC-01-no date.
Specification For Water Leakage Sensor S-1F, Sumitomo 3M Limited, Tokyo, Japan, Fig. 1, Sep. 2001—S. Suzuki.
Linear Leak-Detection; Hydro-Temp, Inc., Baton Rouge, LA; Thomas Publishing Company, p1-2; Jul. 2001.
Andberg John William
Chaikin Stephen Jerry
Agilent Technologie,s Inc.
Luebke Renee
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