Road structure – process – or apparatus – Miscellaneous road structure
Reexamination Certificate
2001-10-18
2003-07-15
Will, Thomas B. (Department: 3671)
Road structure, process, or apparatus
Miscellaneous road structure
C404S019000, C404S031000, C404S036000, C238S014000
Reexamination Certificate
active
06592288
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
This invention is in the field of anti-icing systems for roads and bridges, and is more specifically directed to roadway covering systems.
The icing and snow-covering of roadways is of course a well-known cause of poor vehicle traction, and thus poor driving conditions, during the winter season in many parts of the world. These poor driving conditions result in motor vehicle collisions, and also in reduced traffic flow as vehicles slow in attempting to prevent collisions.
Bridges are especially susceptible to dangerous icing, especially in souther parts of the United States, which often have temperatures around freezing, and also often receive freezing rain and sleet in winter months. An example of a particularly dangerous icing condition is referred to as “black ice”. Because bridge span portions are not in direct contact with the earth, which retains heat from earlier in the day, bridges generally ice sooner than the rest of the roadways in these conditions. Accordingly, cities, states, and other road maintenance entities continue to take significant anti-icing and de-icing actions in winter to maintain or improve roadway and bridge traction. By way of definition, the term “anti-icing” often refers to actions taken prior to precipitation in order to prevent ice buildup, in contrast to the term “de-icing” which often refers to actions taken after precipitation to remove ice buildup. However, these terms are often also used interchangeably with one another. These conventional anti-icing and de-icing actions take the forms of chemical, thermal, and mechanical methods, as will now be summarized.
Anti-icing chemicals prevent ice buildup by lowering the melting temperature of water to a temperature below that of the ambient temperature, thus preventing the formation of ice. These chemicals are also used to melt ice, in the de-icing context, although with poorer efficiency than if used prior to formation of the ice. Examples of anti-icing and de-icing chemicals include the salts of sodium chloride, calcium chloride, and magnesium chloride. Of these three salts, sodium chloride is the least expensive, but is only effective to a temperature of about −12° to −18° C. Sodium chloride also involves significant environmental impact, because of its tendency to increase groundwater salinity, its undesirable effects on fragile aquatic ecosystems, and its effect of leaching soil toxins into groundwater and surface water; sodium chloride also tends to crack the top surface of concrete roadways. Calcium chloride reduces the melting temperature of water to −29° C. and is less damaging to concrete, but can be more damaging to the environment. Calcium chloride and sodium chloride are also quite corrosive to the vehicles themselves, and corrosive to the steel that is often used to reinforce concrete bridge decks. Magnesium chloride is know to reduce the melting point of water to −33° C. and is believed to be less environmentally damaging and less corrosive, but is significantly more expensive than the other salts. In addition, the dispensing of anti-icing chemicals often involves significant labor costs.
Thermal anti-icing techniques involve the heating of the roadway surface to keep its temperature above the melting point of water. For example, U.S. Pat. No. 3,995,965 discloses a heating system including ducts at the surface of the roadway for carrying heating fluid, in which the fluid is pumped in response to a vehicle passing over an actuator. In recent years, test projects have been built in Oregon and in Virginia to evaluate the heating of bridge decks. One of the Oregon projects reportedly involves the heating of a bridge deck that is over 1000 meters in length, using a mineral insulate cable. Another bridge project in Oregon evaluated the use of heated ground water that is pumped through thermoplastic tubing in the bridge deck. The Virginia Department of Transportation projects heats a bridge deck with ammonia carried by steel piping in the bridge deck; the ammonia is heated via a heat exchanger, in which the primary loop carriers a mixture of propylene glycol and water that is heated by a gas-fired furnace. In this Virginia system, a computerized control system activates the bridge heating upon detecting of snow or ice, or upon detecting freezing temperatures in combination with precipitation or a wet bridge deck; the control system also shuts down the heating cycle upon detecting safe conditions.
These conventional thermal anti-icing methods necessarily involve significant construction costs to place the cable or pipe, and are generally not very energy efficient considering that the entire bridge deck is being heated. In addition, if the hazardous conditions (i.e., wet and freezing) continue, the bridge deck continues to be heated, consuming additional energy.
Mechanical methods are generally used for de-icing, rather than anti-icing. Examples of these methods include simply the plowing and bulldozing of ice and snow on the roadways by plowing vehicles.
By way of further background, the application of anti-skid elements to road surfaces is know. A fundamental example of this approach is simply the dispensing of sand over ice and snow, to provide additional friction between the frozen surface and the tires of passing vehicles. Of course, sand and other abrasives do not themselves serve to melt ice and snow, and as such abrasives are often used in combination with chemical de-icing chemicals. Examples of such anti-skid elements, in the form of road or walkway markers or marking tape, are disclosed in U.S. Pat. No. 4,146,635, U.S. Pat. No. 5,316,406, German Patent No. DE 2702442, and U.S. Pat. No. 5,204,159. A description of heat insulation materials for frozen roads is disclosed in Soviet Union Patent No. 1010889-A1.
In recent years, significant research in the field of highway safety improvement has been funded by the United States Department of Transportation. This research includes the use of thin bonded overlays or surface laminates of highway pavements and bridge decks. Several test projects of various bonded overlays and inlays of highway surfaces, and of non-corrosive lightweight thin overlays for bridges, have been carried out. Computer modeling programs for the estimation of pavement and bridge resurfacing life and costs, as well as pavement simulation machines, have also been developed.
By way of still further background, super insulator materials are known. These materials would improve the energy efficiency of thermal anti-icing methods. For example, silica aerogel has the known properties of extremely light weight, and excellent thermal insulating properties. Another known thermal insulator with excellent properties is the THERMAL DIODE coating developed by 27
th
Century Technologies, Inc. This coating is described as creating an effectively one-way super-conducting path for thermal energy in one direction, but an excellent thermal insulator in the opposite direction. By way of still further background, one type of known tire stud material remains flexible and pliable under warm temperatures, but changes its molecular structure under freezing temperatures to become rigid.
By way of still further background, remote and on-site actuation of the dispensing of liquid chemical anti-icing agents onto the driving surfaces of bridges, tunnels, ramps, and roadways, is also known in the art.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a system for preventing the buildup of ice on a roadway or bridge deck by preventing the bonding of ice to the road surface.
It is a further object of this invention to provide such a system having a road cover that can be readily removed and replaced, for example with the change of season.
It is a further object of this invention to provide such a system that utilizes mechanical anti-icing, based on force applied by the ve
Addie Raymond W
Anderson Levine & Lintel
Will Thomas B.
LandOfFree
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