Patent Application
20110302995
The present invention relates to an inherently-low-cost approach to monitoring for fluid leaks ranging from small to large. More particularly the present invention relates to a system and methods for using minimal solid-state sensing and minimal packaging to recognize that fluid is flowing even down at nominal shutoff conditions. It offers the unique ability to provide a wide range of flow monitoring, ranging from smaller leaks than any other system currently available can detect to the maximum flow resulting from breakage of piping and flow elements. A single solid state element combines both a heater and a temperature sensor for the fluid as it leaks past the sensing position simplifying assembly and minimizing setup complexity. Commodity-type housings to add onto or drop into piping can complete the economical but powerful system.
In many flow metering applications i.e. irrigation, there is a need for recognizing that flow leakage is occurring even while the system is nominally shutdown. Existing meters suffer from inability to respond to small flows, inability to keep responding when unwanted flows reach the maximum capacity of the piping, and inherent complexity that drives up their cost and makes them inappropriate for many applications in which monitor prices are a limiting factor.
Prior art involving heat and heat detection in the presence of fluid flow involve unnecessary complexity in that they add additional elements that are not needed, particularly in the common case of water flowing under pressure through pipes. U.S. Pat. No. 6,813,944 by Mayer, et al., U.S. Pat. No. 7,444,863 by Sakai, U.S. Pat. No. 7,058,532 by Yamaghishi, et al., U.S. Pat. No. 6,637,264 by Lotters, et al., U.S. Pat. No. 6,672,154 by Yamaghishi, et al., and U.S. Pat. No. 6,487,904 by Myhre require a second sensor to sense temperature in the flow upstream of where the heat is applied. U.S. Pat. No. 5,553,505 by Bignell, et al. needs four SiC sensing chips. U.S. Pat. No. 7,054,767 by Eldridge requires a second RTD thermal sensor to provide temperature correction. However, in the most common application involving water under pressure flowing through pipes the water temperature is stable and low compared to the highly heated thermistor used in the present invention obviating the need for temperature compensation. U.S. Pat. No. 7,337,661 by Yamada, et al. and U.S. Pat. No. 7,058,532 by Yamaghishi, et al. specify two thermistors and a separate heater. The present invention uses a single sensor which also serves as the heat source. U.S. Pat. No. 7,587,948 by Gysling, et al. requires at least two pressure sensors to determine the pressure fluctuations caused by flow. U.S. Pat. No. 7,587,948 by Gysling, et al. requires two acoustic transducers and matching sensors to get velocity from phase.
U.S. Pat. No. 6,813,944 by Mayer, et al. and U.S. Pat. No. 6,644,133 by Williams make use of sensing on the exterior of the tube through which the fluid is flowing and making use of the thermal conductivity of that tube. That makes it inapplicable to applications in which the flow is passing though PVC or similar non-metallic tubes in which the tube wall is a poor conductor of heat. The present invention avoids that pitfall by inserting the sensor directly into the interior of the tube so that contact is with the fluid and sensitivity to heat dissipation is at its maximum.
U.S. Pat. No. 5,637,789 by Lawson uses a single self-heated thermistor for low flow monitoring but requires the complication of housing it in a separate tube adding to the complexity and cost of the monitoring means. Moreover this tube that bypasses the plumbing-code-required backflow-prevention means is not permitted in irrigation systems. It constitutes an illegal cross-connection that could permit contamination of the incoming water supply so that metering means could not be used with irrigation systems for which the preferred embodiment of the current invention is well suited. The present invention avoids that pitfall by having its sensor in the main stream without any bypassing.
Current techniques used involve metering elements (such as mechanical paddle wheels and turbines that must be spun by the flow for which U.S. Pat. No. 6,644,133 by Williams is one of several techniques that use a turbine within the fluid to generate pulses proportional to flow), or orifice plates and venture sections that partially block the flow for which U.S. Pat. No. 7,437,951 by McDonald, et al is one of several, or that require extensive calibration whenever the metering element is replaced. These meters also contain parts that must be assembled to high precision and that contain costly components in a specially-prepared housing that sets minimum prices that can be charged for the meter. The present invention avoids that pitfall by using a small solid state sensor with no moving parts and minimal protrusion into the flow.
In the flow metering needs of commercial and residential water metering applications those users may have unnoticed water leakage that totals to significant amounts without that passage of water being detected by the meters as it occurs hiding excess water usage. In addition, cost-conscious applications like outdoor water usage, particularly on the residential level, can not afford meters with high price tags since they drive up the system capital costs to unacceptable levels.
Metering devices that offer full range for monitoring at an inherently low cost are needed to detect leakage and to fairly show consumption as an aid to minimizing waste.
Accordingly, several advantages of one or more aspects of the invention are ability to respond to all flows from small to full, inherently-lower cost of manufacture that makes them appropriate for many applications in which moderate costs are a requirement, avoidance of moving elements that must be spun by the flow or that partially block the flow or that require extensive calibration whenever the metering element is replaced, ability to dynamically change properties to meet extreme flow conditions, elimination of parts that must be assembled to high precision and that contain costly components in a specially-molded housing.
Other advantages of one or more aspects are the simplicity of design that permits achieving lower manufacturing cost making them appropriate for cost-sensitive applications like outdoor watering, particularly on the residential level, which can not afford meters with high price tags since they drive up the system capital costs to unacceptable levels, and their ability to be configured to match a wide variety of electrical/electronic inputs so that they can offer the benefits of metering and leak detection where it is not presently practical.
Further advantages will become apparent from a consideration of the ensuing description and the accompanying drawings.
This metering apparatus combines the sensitivity and interchangeability of solid state sensors with a compact form that fits into appropriate packaging specifically, but not limited to, in this case existing commodity plumbing fittings to provide a detector that avoids the costs and complexity of mechanical-basis meters while providing the range and accuracy expected of computer-supported meters.
The ability of the meter's sensing element to respond to the smallest of flows, hundredths of a gallon per minute, gives it the ability to find leaks that are occurring when the system valves are shut off. Leaks that small at a single location can waste over a hundred gallons per day which totals tens of thousands of gallons per year. In areas with water bans those savings over a municipal area can spell the difference between adequate water supplies using existing facilities versus bans or drought conditions being declared.
In addition to that low end monitoring the meter reports typical usage with standard precision so that water awareness can become a constant caution against wastage.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the figures, where like reference numbers refer to similar elements throughout the figures, and:
The present invention may be described herein in terms of various functional components.
In accordance with various aspects of the present invention, and with reference to
Accordingly the reader will see that, according to the invention, we have provided the ability to respond to small flows, ability to respond closely to flows reaching the maximum capacity of the piping, inherently-lower cost of manufacture that makes the device appropriate for many applications in which moderate costs are a necessary factor, avoidance of metering elements that must be spun by the flow that partially block the flow or that require extensive calibration whenever the metering element is replaced, elimination of parts that must be assembled to high precision and that contain costly components in a specially-molded housing.
While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but as exemplifications of the presently preferred embodiments thereof. Many other ramifications and variations are possible within the teachings of the invention. For example, the system could utilize a solid state sensor which responds sharply to temperature differences to provide an on/off signal rather than a proportional one, could use other thermal detection elements such as transistors if less sensitivity is needed, could be located on the top, bottom, or sides of the piping to provide flow monitoring for sewage or drainage gravity systems that do not utilize a full pipe, could be wired into an existing alarm notification to alert a central office of the existence of a fire sprinkler system leak, could be used with an Automatic Meter Reading (AMR) system to provide a minimally-expensive metering element for municipal water service monitoring, could be used with equipment drip pans to alert that leakage flow is occurring, could be used with catheterized post-surgery patients to confirm successful urine flow, could be used in high-flow fire flow meters since it does not block the piping passageway, could be used as a backup safety meter element in a failsafe flow monitoring system, or could even be used in a reverse fashion for a small sailboat or small trolling boat speedometer with the device being fixed to the boat and the boat's travel through the water causing the relative motion for thermal transfer.
Thus the scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.
A method of performing accurate flow monitoring and sensitive leak recognition utilizing state of the art solid state technology in water irrigation systems in all industries including, but, not limited to landscaping, farmlands, vineyards, fire-sprinkling systems etc, or in any other fluid flow monitoring system.
