Measuring and testing – Liquid level or depth gauge – Thermal type
Reexamination Certificate
1998-10-22
2001-07-17
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Thermal type
Reexamination Certificate
active
06260414
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a device for determining the level of a cooled liquid in a closed container, and more particularly, to a cholesteric liquid crystal fluid level indicator that determines the level of a cooled liquid, such as beer, in a keg when placed in thermal contact with the exterior surface of the keg by producing a color change that is a function of the liquid temperature when the liquid is within a predetermined temperature range. The invention also produces a predetermined color when the liquid is within a predetermined temperature range for visually ascertaining whether it is at its ideal temperature.
2. Description of the Background Art
In the bar and restaurant industry, an accurate inventory is paramount to maintaining the bottom line and anticipated profit margins. When food and drink inventory are lost, it eats into the company's profit. Accordingly, restaurant owners and operators employ strict inventory tracking methods for food, liquor and controllables. For instance, food consumption is measured by noting counts per unit or weighing the food product. Specific emphasis is placed on the amount of pounds and ounces being sold and lost. Inventory for controllables, such as paper goods (paper towels, toilet paper, napkins, etc.), condiments (ketchup, mustard, sugars, Sweet-n-Low®, sauces, etc.), glassware and miscellaneous items (straws, toothpicks, etc.) are also routinely counted. Liquor is accounted for by counting bottles and noting levels remaining in partially used bottles. In fact, most bar inventory methods count the bottles in tenths or quarters. This measuring technique is reasonably accurate since the liquor levels can be seen through the bottles. While accountable inventory measuring techniques exist for food, liquor and controllables, there is still no accurate, cost effective method or device for taking the inventory of draft beer in a closed keg.
Conventional techniques for taking inventory of draft beer are either inaccurate, unsafe, time consuming and/or too expensive. Draft beer is sold in opaque kegs. Therefore, beer levels can not be readily and accurately ascertained. Inventory for draft beer is primarily done by lifting and shaking the keg. Lifting and shaking kegs to determine the quantity remaining is highly subjective and inaccurate. It only provides an approximation of how much beer is left in the keg. Another method involves lifting and weighing the keg to determine the amount of beer remaining. Weighing the keg, while theoretically more accurate, requires a durable scale and additional information for converting weight to ounces. Neither method is convenient and both involve heavy lifting. As a full keg weighs approximately 160 pounds, there is a high risk of back injuries, muscle tears and hernias, associated with lifting, shaking and/or weighing kegs, even with a partially filled keg. An injured employee is inevitably lost for a period of time and a worker's compensation claim is invariably made, increasing the likelihood of increased insurance premiums. It is therefore desirable to have a device that measures keg fluid levels without requiring lifting, shaking or weighing. A device for readily measuring keg levels that avoids and solves the foregoing risks and problems would be well received.
Another problem experienced by restaurant and bar businesses is ascertaining whether beer in a keg is at its ideal temperature or at least within its required temperature range. The ideal temperature for beer varies. The ideal temperature for beer can range between 32° F. and 44° F. depending on the make and entity storing the beer. The ideal temperature for most beer is approximately thirty-eight degrees Fahrenheit (38° F.). Microbrews and foreign beers can have ideal temperatures between 38° F. and 42° F. And, some establishments store their beer at temperatures below 38° F. and as low as 32° F. Therefore, most coolers are operated within this temperature range to keep the beer at its ideal temperature. In fact, many local health ordinances require that coolers be operated within a specified range, such as 35° F. to 44° F.
Beer kegs are stored in coolers, typically along with other items that are needed more frequently. Therefore, the temperature in a cooler constantly fluctuates due to the refrigeration system efficiency and frequent opening of the door. If the cooler is not operating properly or is experiencing a high flow of traffic, it can warm the cooler several degrees. This increase in temperature is typically unnoticeable to the individual, but still affects the temperature of the beer. If the cooler is allowed to operate outside its temperature for extended periods of time it can cause the beer to age prematurely. Conversely, some coolers may be operated too low, such as around 33° F., to compensate for fluctuations in temperture. However, when traffic slows down for a period of time the beer can drop below its ideal temperature. If a device was ecomically available for monitoring the temperature of beer in a keg, the cooler could be adjusted to ensure that the beer is maintained at or near its ideal temperature. In fact, a beer level measuring device for kegs that also insures proper beer temperature would be well received by the industry.
Several devices are known in the background art for measuring propane levels in gas tanks. Other devices are known for measuring the temperature of liquids, such as wine. However, none of these devices are adapted for or capable of measuring the level of beer or other fluids in a closed keg or for indicating whether beer is at its ideal temperature, as contemplated by the instant invention. One known device comprises an electronic sonar device. This device is costly and outside the scope of the instant invention. Other devices known employ thermotropic or thermochromic liquid crystal technology for measuring gas levels in closed tanks, such as propane tanks. This technology has primarily been applied to flow visualization and heat transfer research. More recently, thermochromic liquid crystal technology has been used for thermometer strips, such as forehead thermometers, and propane tank gas measurement devices. These devices, however, are not designed for reacting to temperatures within the temperature range in which conventional coolers and walk-in refrigerators are operated, i.e. between 32° F. and 44° F. Such a device would facilitate convenient monitoring of a keg's beer level and indicate whether the beer is below, above or at its ideal temperature.
The most common thermochromic liquid crystal known to be employed with measuring gas in closed tanks is the cholesteric liquid crystal. Cholesteric liquid crystals are chemical compounds and mixtures which exhibit the mechanical properties of liquids but have the optical properties of crystals. Cholesteric liquid crystals are optically active mixtures of organic materials which produce color changes in reaction to fluctuations in temperature in a temperature range which is a function of the particular compound selected. Depending on the compound selected, changes from red to violet can occur in a range of +20° C. to 250° C. Known gas level monitoring devices are only designed to react to temperatures above 59° F. The liquid crystal composition in theses devices can not react to exhibit colors between 30° F. and 50° F.
Cholesteric liquid crystals show color by selectively reflecting incident white light. In response to temperature differentials, conventional cholesteric liquid crystals change colors across the visible spectrum, beginning at colorless and going through red, orange/yellow (tan or brown), green, blue, violet and colorless again. Liquid crystal mixtures and products typically have a red start/transition temperature at one end of the bandwidth, a green mid-section and a blue start/transition temperature at the other end of the ban
Brown Keith
Currie Chester J.
Jackson - Kie, Inc.
Lhota, Esq. David P.
Stearns Weaver Miller Weisslar Alahadeff & Sitterson, P.A.
Williams Hezron
Wilson Katina M.
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