Patent Application
20160061381
1. Field of the Invention
This invention is in the field of pressure vessels such as those that are used in a variety of applications worldwide. These applications include industrial compressed air receivers, domestic hot water storage tanks, diving cylinders, recompression chambers, distillation towers, pressure reactors, autoclaves, and many other vessels in mining operations, oil refineries, petrochemical plants and nuclear reactor vessels.
Other applications include submarine and space ship habitats, aircraft pressurized systems, pressurized pneumatic and hydraulic reservoirs, rail vehicle airbrake reservoirs, road vehicle airbrake reservoirs, and storage vessels for liquefied gases such as ammonia, chlorine, propane and butane, and modern vehicles using compressed gases for their engines.
By way of only one (non-limiting example), fire suppression systems require high-pressure storage containers (also called bottles or cylinders), hundreds of thousands of which are being installed every year worldwide.
Many known pressure vessels are made of steel, either in a cylindrical or spherical shape, but some mechanical properties of steel, achieved by rolling or forging, could be adversely affected by welding, which is necessary to make a sealed vessel and leads to an increased wall thickness and overall weight of such vessels.
Some known pressure vessels are made of composite materials, such as a filament wound composite using carbon fiber held in place with a polymer. Due to the very high tensile strength of carbon fiber, these vessels can be very light, but are much more difficult to manufacture and require much more human labor.
The present invention introduces a method of manufacturing a new type of pressure vessel, and various design configurations of such pressure vessels using additive manufacturing technology, better known as 3D Printing, to provide:
The term “vessel” as used in this specification means any enclosed container, cylinder, bottle, tank, pipeline, inhabited vehicles (spacecraft, undersea research vessels, etc.) or any other enclosed structure capable of maintaining an interior pressure which is different from the pressure on the outside thereof. Vessels and inhabited containers having increased outside pressure apply to this invention as well.
2. Description of the Related Art
One of the earliest early efforts to design a vessel (tank) capable of withstanding high pressures up to 10,000 psi (69 MPa) was made in 1919. The result was a 6-inch (150 mm) diameter tank spirally-wound with two layers of high-tensile-strength steel wire to prevent sidewall rupture, having end caps longitudinally reinforced with lengthwise high-tensile rods.
U.S. Pat. No. 4,505,417, to Makarov, et al., describes a mill for manufacturing bodies of multilayer high-pressure vessels comprising rotators to rotate the body of the vessel, which has its butt-end portions secured therein. The body of the vessel is surrounded by a portal capable of moving along the body of the vessel for winding a steel strip around the vessel body.
U.S. Pat. No. 5,419,416, to Miyashita, et al., describes an energy absorber having a fiber-reinforced composite structure for receiving impact energy. The absorber has a body formed of a fiber-reinforced composite material with a hollow cylindrical shape and having a plurality of portions so that the thickness of the body gradually increases in at least two stages in an axial direction.
U.S. Pat. No. 8,557,185, to Schulmyer, et al., describes an external pressure vessel and at least one insert basket in the pressure vessel.
U.S. Pat. No. 8,540,876, to Poklop, et al., describes a multi-tube pressure vessel, however the focus of this invention is a permeate adapter.
A seemingly close design idea was presented in U.S. Pat. No. 7,963,400, to Stolarik, et al. This patent describes a thermoplastic distributor plate for a composite pressure vessel having a central opening and radial slits, however, the plate is useful only for the purpose of swirling the fluid through the disk from the bottom side to the top side around the opening for use in a water treatment apparatus. Moreover, in this case the disks should only “have a thickness sufficient to support water treatment media without deforming”—column 5, line 1. So, practically, in this case the outside wall of the vessel was holding and preventing the disk from deforming or destruction, which is the exact opposite from the present invention.
Finally, all previous inventions were focused mainly on reinforcing the walls of a vessel using different techniques and materials, from high tensile steel strips to composite materials. Nobody was actually thinking about reinforcing the vessel walls from the inside by providing an internal supportive structure that allows the considerable reduction of the pressure load on the walls of a vessel by transmitting such a load to the opposite part of the wall via the internal supportive structure, thereby distributing the pressure applied to the wall. Furthermore, no one thought about the possibility of making pressure vessels using a 3D printing process, which allows for the production of a whole vessel in one process and without use of human intervention and, most importantly, without waste materials.
The present invention therefore provides an improved method for manufacturing a pressure vessel, and a unique design of a pressure vessel that has improved performance and cost compared to known pressure vessels and methods for making them.
In the specification, the following terms have the meanings ascribed thereto:
Additive manufacturing or 3D printing is a process of making a three-dimensional solid object of virtually any shape from a digital model. 3D printing is achieved using an additive process, where successive layers of material are laid down in different shapes. 3D printing is also considered distinct from traditional machining techniques, which mostly rely on the removal of material by methods such as cutting or drilling (subtractive processes). Additive manufacturing employs different manufacturing technologies that can produce custom parts by accurately “printing” layer upon layer of material, including, but not limited to, plastics or metal, until a 3D form is created.
Bond—a device providing strong and solid connection between the wall or shell of a Pressure Vessel and/or a Central Supporting Element and having any shape including but not limited to the shape of spokes, strings, needles, chains, disks, plates, rods, screw-shaped and complex profiled structures, tubes, polyhedrons, cellular and Honeycomb-like structures and other rigid ties that allow the distribution and reduction of pressure forces applied on the walls or shell of a Vessel.
Central Internal supportive Element—an enclosed structure inside of a Pressure Vessel having its own internal enclosed space or cavity that communicates with the interior of the Pressure Vessel via one or more holes or other openings, and communicates with the environment outside of the Pressure Vessel via a Filling and/or Release device, such as a valve, when such has been initiated during filling or release of a fluid stored inside of the Vessel or other entry or exit (for human occupied containers). The Central supporting element, situated in any part of the Pressure Vessel, has a solid connection to the outer shell of the Pressure Vessel via Bonds and may have any geometrical shape, including but not limited to a round tube, sphere, Honeycomb-like cell or polyhedron-shaped cell or rod.
Honeycomb-like internal supportive structure—a Bond structure consisting of cells of any geometrical shape, whether enclosed or open, and including, but not limited to, any shape from a round tube to a polyhedron, having an internal space that communicates, directly or indirectly, with internal spaces of all other cells and the internal cavity of the Central Supporting Element, which in this case can be just another cell that distinguishes from all other cells in the structure by having direct communication with a Filling and/or Release device. Such a structure builds firm bonds or connections between the walls or Shell of the Pressure Vessel and the Central supporting element for distribution and reducing of tensile forces and the pressure load on the walls or shell of a Vessel.
Internal supportive structure—a structure that provides strong, solid connection between the walls (or shell) of a Pressure Vessel and the Internal Supportive Element via Bonds for distributing and reducing the pressure load on the walls or shell of a Vessel.
Pressure Vessel—an enclosed container, bottle, cylinder, pressurized pipe and any other enclosed structure designed to hold and/or transport gases, liquids and/or other fluids at a pressure substantially different from the ambient pressure, whether the internal pressure is higher or lower than ambient. This definition applies also to underwater, aerial and space vehicles and structures, both inhabited and industrial.
Filling device—a valve, regulator, tap or any other device, assembly or structure that allows filling and refilling of a Pressure Vessel with a fluid; in most cases such a device is used for both filling the Pressure Vessel with a fluid and for releasing the fluid therefrom. A Filling Device is normally situated in the end cap (or “head”) of a Pressure Vessel. For inhabited containers, this may also be a point of entry (such as, for example, a sluice or anteroom).
Release device—a valve, regulator, tap, membrane or any other device, assembly or structure that allows the release of a fluid from a Pressure Vessel; in most cases such a device is used for both filling the Pressure Vessel with a fluid and for releasing the fluid therefrom. A Release Device is normally situated in the end cap (or “head”) of a Pressure Vessel. For inhabited containers this may also be a point of exit (such as, for example, a sluice or anteroom).
Environment outside of Pressure Vessel (or Container)—Anything that is on the outside of the Pressure Vessel, such as, but not limited to, piping, valves and other devices placed outside of the Pressure Vessel for forwarding its contents further, or for filling the Pressure Vessel with a gas or other fluid or just venting the fluid to the external atmosphere if the contents of the Pressure Vessel are released directly into the external atmosphere.
Shell or External Shell—an external wall or wall structure of a Pressure Vessel or pipe.
The principal objects of this invention are as follows:
The provision of a pressure vessel design that overcomes the above-described deficiencies in the prior art, especially in pressure vessels and cylinders where there may be a very great pressure differential between the internal and external pressures.
The provision of a manufacturing method that allows making pressure vessels of a unique design having an internal supportive structure.
The provision of a method for making vessels for fluid packaging and storage.
The provision of a method of making pressure vessels in one automated process, without, or with limited, human intervention.
The provision of a pressure vessel design that allows reducing pressure load on its walls by providing an internal supportive structure having bonds which support the walls of the pressure vessel.
The provision of an additive manufacturing method and process whereby a pressure vessel is fabricated by applying a layer-upon-layer technique using 3D printing, the manufacturing method comprising, but not limited to, Fused deposition modeling, Electron Beam Freeform Fabrication, Direct Metal Laser Sintering, Electron Beam Melting, Selective Laser Melting, Selective Heat Sintering, Selective Laser Sintering and other additive manufacturing methods.
The provision of an additive manufacturing method and process where a pressure vessel is made layer-by-layer using 3D printing techniques and materials comprising, but not limited to, a group of synthesized materials, ceramics, metal and metal alloys powders, thermoplastics, clays, graphene and carbon compositions, paper, foils and combinations or mixtures of them.
The inventive method utilizes Additive Manufacturing and/or 3D Printing technology that allows the creation of a unique design of a pressure vessel, cylinder or other container under positive or negative pressure, using an internal supportive structure that allows for the reduction of pressure applied to the walls of the Pressure Vessel and/or the application of counterbalancing pressures to those walls. This allows for the fabrication of such vessels or containers that are lighter and stronger that current industry product, using less material and without any waste.
For many decades the industry relied on the strength of the material used to construct a Pressure Vessel, and the thickness of the vessel walls since Pressure Vessels are held together against the gas pressure due to tensile forces within the walls of the vessel. The normal (tensile) stress in the walls of the vessel is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls.
Therefore, Pressure Vessels are designed to have a thickness proportional to the radius of the tank and the pressure of the tank and inversely proportional to the maximum allowed normal stress of the particular material used in the walls of the vessel.
Because (for a given pressure) the thickness of the walls scales with the radius of the tank, the mass of a tank (which scales as the length times radius times thickness of the wall for a cylindrical tank) scales with the volume of the gas held (which scales as length times radius squared).
The present invention provides a new approach to the design and manufacturing method of a Pressure Vessel, which allows for making it lighter, stronger and capable of withstanding much greater pressure differentials (whether it is the pressure within the vessel which is greater, or the pressure outside the vessel which is greater) than heretofore known. In this context, a “much greater” pressure differential is one which is at least 5 times, and, more preferably, at least 10 times greater than known pressure differentials for vessels made of similar materials and with similar construction. For example, a currently known container for holding liquefied natural gas made of reinforced steel may be capable of withstanding a pressure differential of 300 bar, while a vessel made in accordance with the inventive method and design may be capable of withstanding a pressure differential of 10,000 bar. It will also be appreciated by one of ordinary skill in the art that, simply because a vessel may be capable of withstanding such a great pressure differential does not require that the vessel be subjected to any pressure differential whatsoever. Again, by way of example only, essentially every vessel is manufactured in a zero-differential environment, and, even after construction, may not be subjected to a differential pressure environment for some time, if ever. Some vessels made in accordance with the invention may be used for containing fluids at a zero-differential pressure environment, such as holding gasoline in a passenger vehicle. However, these vessels may be capable of withstanding higher pressure differentials due to their construction compared with known fuel tanks, and can therefore be made lighter due to their improved construction.
It is a further object of the invention to provide a vessel for use in vehicles which run on stored hydrogen, methane or other gases that would be able to safely accommodate much larger volumes of fuel by increasing storage and/or pressure.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
a is a top view, similar to that of
b is a detail of an individual cell of the embodiment of
Bonds 13 can be distributed within vessel 10 either randomly or, in a preferred embodiment, using a configuration calculated to optimize force equalization within vessel 10. The embodiment of
Central supporting element 12 can be of any shape, providing that it includes a cavity or an empty space inside therein that communicates with the internal environment of the vessel, e.g., via one or more holes or openings 15. This is necessary to allow for the filling of vessel 10 with a fluid and the release of the fluid stored in the interior of a vessel under pressure. For this purpose, a filling and/or release device, such as valve 14 or any other device with this functionality is positioned on one or both ends of central supporting element 12 allowing, when in use, a direct communication between the internal cavity of element 12 and the environment outside of vessel 10. Valve 14 can be made separately or integrally with vessel 10 during the 3D printing process. In some cases, a release valve can be situated on the top and a refilling valve on the bottom of element 12 or vice versa.
Central supporting element 12 is equipped with holes or openings 15 that allow communication with the internal environment of vessel 10. Holes 15 also allow filling vessel 10 with a gas or liquid and the release thereof. The size and number of such holes 15 may vary depending on the application and can conveniently be limited to a certain value in order to allow only a certain amount of the stored fluid to be released at a predetermined rate, which can be calculated in advance in known fashion in dependence upon the pressure of the fluid, its viscosity and the total cross-sectional area of all holes 15, inter alia. This is a very important feature of this invention since in many applications only a limited amount of fluid should exit vessel 10 during a given time interval, or in cases where a full discharge time is required by a standard, as in fire suppression cylinders (e.g., 60 sec.).
The embodiments shown in
The inventive concept allows making hermetically sealed or airtight vessels with internal positive pressure as well as external positive pressure, such as submarines and underwater structures, whether inhabitable or industrial.
Manufacturing of such pressure vessels using conventional technologies adopted by the industry would be very difficult. However, additive manufacturing, better known as 3D printing allows making such vessels without the problems associated with most current technologies and without the waste of construction materials.
There are various 3D printing techniques that can be used for manufacturing such vessels with the inventive design concept of the internal supportive structure, such as:
Most of these techniques are suitable for the manufacturing of the inventive pressure vessels. They allow for the manufacture of the end product from a single material and/or multiple materials. Extrusion (FDM), Wire (EBF) and Granulate (DMLS, EBM, SLM, SHS and SLS) based manufacturing processes are most preferable for this invention.
Using these techniques, the whole vessel may be made in one process, without direct human intervention or any waste materials. Moreover, the walls of a vessel can be made either solid or having a cell structure for reducing the total weight of the product, depending upon the application. Such a cell structure can be of any shape that maintains the overall strength of the wall, e.g., a honeycomb structure.
Using this idea, we introduce the most preferred embodiment shown in
All structural cells of the bond structure (63, 73, 93 and 103) must have some holes between them for communicating with each other and central supporting element (62, 72, 92 and 102) in order to allow filling the vessel (60, 70, 90 and 100) with a fluid and releasing it when needed via valve (64, 74 and 94) situated on one or both ends of the central supporting element (62, 72, 92 and 102). The structural cells of the bond structure (63, 73, 93 and 103) may have any possible shape that will allow for the effective transmission of the pressure forces applied to the external shell of the vessel (60, 70, 90 and 100) onto the central supporting element (62, 72, 92 and 102) and between the cells. Preferred structures are tubes or polyhedrons having triangular, square, pentagonal, hexagonal, etc. cross-sections. The central supporting element (62, 72, 92 and 102) of each embodiment can be the same as other cells with the only difference being that its internal cavity can communicate with its respective filling and release device(s) (64, 74 and 94). The opening shown inside central supporting elements (62, 72, 92 and 102) is provided only schematically and does not need to be different from the cross-section of the other cells in the vessel, which in turn can be made different within the same vessel, which is easy to accomplish using 3D printing techniques.
The biggest advantage of this design of a vessel (60, 70, 90 and 100) is the reduced risk of an explosion resulting from external damage to the vessel compared to the design of known pressure vessels. Should the external shell of the pressure vessel be damaged by a bullet or other mechanical means, then only one or a few cells will release their contents instantly, but most of the stored fluid will be released with a controlled speed. This is achieved due to reduced flow capacity of the holes through which each cell communicates with each other and the central supporting element. The number and size of these communication holes, as well as the number and size of the cells themselves can be calculated during the design process according to any needed release and filling time of a pressure vessel and the desired safety level. Most pressure vessels do not need fast fluid release, like fuel tanks of the vehicles using gases. Such fuel vessels shall have an increased number of cells of the internal supportive structure and a reduced number and/or flow capacity of the intercellular holes or openings between the cells which greatly increases the safety of such vessels.
Therefore, this design concept using honeycomb-like bond structures (63, 73, 93 and 103) is most suitable for high-pressure gas or liquid storage, especially in fuel tanks in aircraft and automobiles (e.g., those fueled by methane or hydrogen), etc. Moreover, the fact that the surface area of the interior cells is many multiples of the surface area of the vessel's external shell will also considerably reduce the pressure stress on the external shell of the vessel having such an internal supportive structure. This will allow holding fluids at much higher pressures than would be the case in vessels without internal supportive structure.
Attention is now specifically directed to
a shows a cross-sectional partial cutout of a vessel 70, which is similar to vessel 60, only having different cell structure 73 providing a firm connection between walls 71 and central supporting element 74 having an internal cavity 72.
Suitable materials for the manufacturing of the various inventive pressure vessels are metals and metal alloys, synthesized materials, silicones, clays, graphene, porcelain, foils and paper, and any other materials that can be used in Additive Manufacturing processes. These materials can be provided to the manufacturing process in the form of a powder, in liquid or molten form, or dissolved and synthesized during the 3D printing process, as well as any other form that can be used in additive manufacturing. Most suitable are synthesized materials, ceramics, metal and metal alloys powders, composites, thermoplastics, clays, graphene and carbon compositions, paper, foils and combinations or mixtures of them.
Powders containing titanium and its alloys, cobalt chrome alloys, stainless steel, aluminum and ceramics are most preferable for manufacturing the inventive pressure vessels.
Graphene and composites based on graphene are 200 times stronger than steel, therefore they are perfectly suited for making high pressure vessels and specifically for the external shell or wall of such a vessel, its internal structure or just a supporting part of such a shell.
The inventive method of manufacturing allows the manufacture of such vessels from computer aided design (CAD) using computer aided manufacturing (CAM), which enables producing a product of such complex shape in one piece, layer by layer, until complete.
The release and/or refilling device (14, 24, 34, 64, 74 and 94) can be made on one end or both ends of the central supporting element (12, 22, 32, 66, 74, 94 and 102), e.g., one for release and one for filling. Such devices can be made in one 3D printing process together with the vessel or can be made separately and attached to the central supporting element using a threaded connection, adhesives and any other connection techniques suitable for a particular application and pressure. The central supporting element selectively communicates with the environment outside of the vessel when filling and/or release device is initiated for a filling or release. This environment outside of the vessel can include, without limitation: piping, valves and other devices placed outside of the vessel for forwarding the released fluid further in a system or filling it with a gas or other fluid. In some cases, the environment outside of the vessel can be just the external atmosphere if the content of the vessel has to be, or may be, released directly into it.
All embodiments show that the shape of the supporting structure inside of a vessel can vary in many ways as long as it fulfills the main requirement of this invention—distribution of the pressure forces applied to the external shell of the vessel to the central supporting element, which in turn distributes these forces further to the external shell, thus reducing the overall pressure load on the shell (or walls) of the vessel.
The cellular design of the internal supportive structure allows for the considerable reduction of the pressure load on the external wall structure of any pressure vessel or container by transmitting and distributing at least a part of that load onto walls within the cellular structure. Also, a part of this pressure load will be transmitted onto other parts of the wall structure, which effectively cancels at least a part of this load and allows the external wall structure to accommodate a much higher pressure than without said internal supportive structure.
This allows making much stronger and lighter vessels or containers that can withstand much higher pressures than similar vessels without such internal supportive structure. The bonds and especially the walls of the cellular structure in all embodiments can have any thickness from 1 atom (by graphene) to many millimeters or more depending on the size of a desired vessel and the application in which it will be used.
The inventive method of manufacturing such vessels with an internal supportive structure, not limited to those shown in the above embodiments, allows making the complex structures of the vessels in one fabrication session using 3D printing techniques. A 3D printer, using computer aided design, can make any such vessel by printing it, layer-by-layer, from one end to another, using suitable materials described above whether in the form of a powder, paste, clay, etc. The technique of 3D printing is known to those skilled in the art and is not a subject of this invention, per se.
Some of the inventive design configurations, such as those shown in embodiments 20 and 30 can be made using conventional techniques adopted by the industry, such as Filament Wound Composite technique and some similar methods. In this case, the internal supportive structure consisting of the central supporting element (22 and 32) and bonds (23 and 33), can be made separately using a metal or other material and further being attached to the external shell using conventional filament winding machines working with carbon fiber or other fiber material. Here, it is necessary to establish firm connections between the bonds (23 and 33) and the external shell of a vessel, which can be done using many conventional techniques and materials. A use of graphene or graphene-based composites is strongly recommended. Graphene can also be used for making at least a part of the internal supportive structure, which can have bonds as thin as 1 atom.
The embodiments containing cellular bond structure (e.g., 60, 70, 90 and 100) will have a very high safety level, since such designs will prevent the rupture of the vessel due to high pressure and/or temperature and mechanical damage from outside. Such damage (e.g., from a riffle bullet) will only permit the fast release of a gas from one or a few cells while slowing the release of the gas from all other cells thereby preventing the catastrophic or explosive rupture of the vessel. This important feature can prevent the many fatal accidents occurring every year resulting from damage to pressure vessels worldwide.
The invention presented above also applies to human inhabitable or visited containers, such as underwater stations and vehicles that operate at a higher outside pressure; as well as aircraft and space vehicles, space and interplanetary stations that might have higher pressures inside than outside. The interplanetary stations and other habitats may have both, increased or reduced ambient atmospheric pressures.
Cellular supporting structures such as those shown in
Another use of the inventive vessel is shown in
The single segment's internal cellular supporting structure 112 can either have strong bonds for supporting each other and the external shell 111 of segment 110 or can be incorporated into supporting disks similar to those shown in
There can be two variations of the cell structure—the cells that have cavities that are communicating with the interior of a pipe or pipeline and the cells that are not communicating with the interior of a pipe segment or pipeline.
However, the best method of making such pipelines is to make them on location using a mobile 3D printer. Such a printer would produce external and internal structures similar to those described above, using the same materials and techniques and do so continuously on demand.
If such a pipeline, transporting for instance natural gas under pressure, is damaged then only damaged cells will start leaking their content, but other cells will continue in use. Repairing such a pipe would be also much easier, as well as containing and fighting fires resulting from such damage.
The walls of every single cell should be made as thin as possible, consistent with the operating parameters, for functioning as a supportive structure in order to keep the weight of the individual pipe segments down, which is possible since the external wall of the segment can be also made thinner since it has an internal supportive structure.
Moreover such pipes can be made from non-corrosive materials, which can greatly extend their life of use. For instance a pipe made from a ceramic using 3D printing can maintain a perfect condition in the ground or underwater for hundreds of years at least.
Car manufacturers and users would greatly benefit from this design as well, since pressurized fuel tanks would be much safer and can be made in any possible shape to fit into available space inside of a car body. This applies to all other vehicles, aircraft and space installations.
While there have been shown and described and pointed out fundamental novel features of the invention as applied to the described embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
