The assignee for this patent application is
Reporters obtained the following quote from the background information supplied by the inventors: "This invention relates to storage vessels for compressed fluids. More specifically, it relates to light-weight storage vessels conformable to a desired geometry.
"As the prices of gasoline continue to rise and the damaging effects of exhaust fumes exerted into the atmosphere by gasoline combustion engines come to the forefront of public attention, natural gas vehicles rapidly gain popularity. According to some estimates, currently, more than 15 million vehicles worldwide are fueled by compressed natural gas (CNG), and their number is growing. CNG has a much lower emission profile than any other fossil fuel, while providing comparable mileage per gasoline gallon equivalent (GGE), making it an attractive environmentally-friendly alternative to gasoline and diesel. Natural gas is fairly abundant in many parts of the world, including
"Natural gas vehicles face a number of issues that must be resolved to facilitate a widespread adoption of this technology. One major problem arises with respect to storage of CNG in a vehicle. Gas is typically stored in spherical or cylindrical vessels because of their inherent abilities to resist internal pressures. Conventional CNG tanks are made of steel, making them very heavy and unwieldy. For automobiles, cylindrical CNG tanks are generally placed in the trunk, where they occupy considerable volume and add excess weight. Accordingly, what is needed is a light-weight storage vessel capable of withstanding high internal pressures and conformable to desired geometries better suitable for unobtrusive placement in vehicles.
"This problem was recognized by others, but was addressed through inferior approaches. For example, patent no. EP0633422 discloses a CNG storage vessel that may be formed to different shapes. The storage vessel relies on a number of internal I-beams that are welded or diffusion bonded to the interior walls of a vessel, which is made of superplastic material. Such design creates a number of problems. The I-beams add additional weight, while welding may weaken the structure and create failure points, therefore, compromising the safety of the tank when it is filled with a highly pressurized gas. Accordingly, the solution offered by EP0633422 has several serious flaws, all of which are eliminated in the present invention.
"A similar solution to the one provided by EP0633422 was offered by U.S. Pat. No. 5,323,953 assigned to the automotive giant
"The present invention utilizes a much different design that eliminates the aforementioned drawbacks present in the prior art. In view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "The long-standing but heretofore unfulfilled need for a light-weight storage vessel for CNG capable of withstanding high internal pressures and conformable to desired geometries is now met by a new, useful, and nonobvious invention.
"In an embodiment, the novel structure includes a network of internal supports disposed within the interior of the storage vessel. The internal supports may be integrated into the structure by utilizing a lattice frame composed of a plurality of interconnected frame members. Each internal support is a strip of fiber-reinforced composite material disposed between two or more frame members. When the storage vessel is filled with pressurized gas, the walls of the storage vessel are subjected to large outwardly directed forces due to high internal pressure. The internal supports counteract the pressure forces by applying inwardly directed tension.
"The storage vessel includes a fluid-impermeable outer shell that possesses required structural integrity and ability to withstand high internal pressures without undergoing plastic deformation. The outer shell is composed of several differently-oriented layers of fiber-reinforced composite material. The lattice frame may be utilized for integrating the outer shell into the structure of the storage vessel. This may be accomplished by covering all exterior surfaces of the lattice frame with one or more layers of fiber-reinforced composite material.
"A valve module is connected to the storage vessel to permit charging and discharging the vessel with compressed gas.
"In an embodiment, the internal supports may be twisted within the interior of the lattice frame to reduce their surface area. This technique allows more interior supports to pass through the interior of the storage vessel without interfering with one another. In an alternative embodiment, the internal supports may be tapered rather than twisted to achieve the same goal. In yet another embodiment, one or more internal supports may be tied or gathered to reduce their surface.
"In an embodiment, the frame members may be made of a fiber-reinforced composite material, steel, titanium, alloys thereof, and other ductile materials exhibiting high yield strength, shear modules, fracture toughness, hardness, and specific strength. The frame members may be interconnected by means of welding or diffusion bonding collectively forming the lattice frame of a predetermined shape suitable for a particular application.
"In an alternative embodiment, the lattice frame is only needed during the manufacturing process, and once the curing process has been completed, the lattice frame does not serve a notable function. In such embodiment, the lattice frame may be made of a polyurethane foam, which may be dissolved after curing is completed by introducing organic solvent to the interior of the storage vessel. In alternative, the lattice frame may be left in place if removal is not necessary to achieve desired strength and functionality.
"The fiber-reinforced composite material comprises a reinforcing base fabric infiltrated with a matrix resin. Reinforcing base fabric may be one of the following: carbon fiber, carbon nanotubes, para-aramid synthetic fiber, aramid fiber, vinylon fiber, and polyester fiber fabric. The matrix resin is selected from the group consisting of epoxy resin, vinyl ester resin, polyester resin, phenolic resin, polybutylene terephthalate resin, polyimide resin, polyetheretherketone resin, and bis-maleimide resin.
"In an embodiment, additional materials may be placed between the layers of the outer shell to increase strength, fluid impermeability, shock absorption, thermal insulation, etc.
"The fiber-reinforced composite material must be cured under proper temperature and pressure conditions. An autoclave may be utilized to achieve high temperature and pressure curing. In one embodiment, the curing process in performed only once after all internal supports and outer shell layers have been added to the lattice frame. In an alternative embodiment, the curing processes may be done in stages to allow each set of components to cure before the next set is introduced.
DESCRIPTION OF THE DRAWINGS
"For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which:
"FIG. 1 is a perspective view of the lattice frame;
"FIGS. 2A-C depict a sequence of internal supports being integrated into the lattice frame;
"FIG. 3 is a cross-sectional view of the lattice frame depicting a network of internal supports within the lattice frame; and
"FIGS. 4A-C depict a sequence of exterior shell enveloping the lattice frame being formed layer by layer."
For more information, see this patent application: Horstman,
Keywords for this news article include: Energy, Oil & Gas, Natural Gas,
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