This invention relates to a frameless, preferably folded plate, space structure. More particularly, the invention relates to frameless folded plate space structural systems which use folded plate space modular(s) as the building block(s) of a structural system and may be used to create structures without the need for load bearing columns, frames or other structural support members, in order to maintain the integrity of the structure.
This invention has several main components including the folded plate space modular, and frameless folded plate space structural systems (FFPSSS). The system applications may include:
The space modular is designed based on the folded plate structural concept, and can be made from any material, including plastics. Space modules are, in accordance with one aspect of the invention, made from thin plates of structural plastic, and these can be as thin as ⅛ inch or less, specifically configured and shaped so that a plurality of such plates, whether of the same shape or different shapes, can be located adjacent one another in a selected manner to create a folded plate space modular.
A single folded plate space modular is used with other identical or different shaped modules to form a frameless folded plate space structural system. Frameless folded plate space structural system(s) can be assembled to form a complete structure or a component of a structure such as frameless plate space roof structures.
Frameless folded plate space structures offer advantages of conventional structures and a lot more. Unlike conventional structures in which the load on the structure is transferred onto a framing component of the structure, the load on frameless space structures is carried by the entire shell of the structure. This particular design may eliminate the need for framing. The framing is indeed the largest and heaviest component of any structure.
Folded plate spaced structures have numerous usages in private, commercial and public sectors. They may be ideal for school cafeterias and lunch shelters, gathering rooms, swimming pool enclosures, gyms, shade structures, green houses, warehousing, light industries, hangars, to name just a few examples.
Lightweight, easy and fast construction makes the space structures of the invention additionally advantageous for fast track projects. A 2000 square foot structure can be assembled by a small crew in a couple of days. The modular space structures of the invention can evenly distribute the load to the foundation thereby eliminating the need for large foundation due to concentrated framing loads.
Roof modules are typically installed on the exterior walls of the structure. They are only supported by the exterior walls and there is no need for any roof framing or interior supports. Furthermore, they are water proof and insulated.
Flexible metal molds (or jigs) can be designed and fabricated which with some modifications can take the angles and sizes of several size modules. All modules (including wall, ceiling, roof) may be typically the same and follow the same formulas. The same mold can be used to fabricate different modules.
Folded plate solar modules can be fabricated by incorporating solar cells into the structural plastic plates. Solar modules are like the other modules in that they have all architectural and structural characteristics of the modules. The number of solar modules used in any structure will typically depend upon the electrical and other needs and requirements of the structure.
Preferably, each module is monolithically fabricated to act as one structural unit. Forces on the module typically result from dead load, live load, wind and seismic movements and these are balanced by the tension and compression stresses in the plates. Stress in a structure is an internal resistant to an external force. It is the sum of these stresses in the plates which holds the modules in equilibrium.
The modules of the invention (including wall, ceiling and roof) are typically, but not necessarily, the same. Flexible molds can be adjusted to form the angles and measurements of different modules. This design flexibility offers structures which can practically satisfy all architectural needs of any projects.
The modules preferably need to be monolithical. The plates preferably need to have fixed connections to transfer the stresses in the plates. There are two primary fabrication methods.
(1) Molding: Selected material is molded into the shape of the modular. Structural Plastic can be molded by injection, press or vacuum methods. Flexible wood and metal Molds are being fabricated which with some modifications can take the angles and sizes of several modular.
(2) Continuous Connection: Pre-cut and angled structural plates are assembled in the above molds and connected to each other with stainless steel or aluminum, or other material, profiles in the shape and angles of the module. The connections are combinations of mechanical and chemical attachments and these may include rivets, bolts, glue and epoxy, as examples only.
The modules may be connected to each other and the foundation by flexible bolted connections. The connections allow free movement of the individual modules as well as the entire structure.
In a foundation by a flexible bolted connection, the module can freely move in all directions. The flexible connections absorb a big percentage of pressure on the module which may result from seismic movements, wind and other loads on the structure. In connecting of the modules to each other, the entire structure can freely move in the direction of the load. The pressure on the structure is preferably absorbed by the connections reducing the load on individual modules.
In the drawings:
The invention comprises a specially designed and configured space module. The invention is also for a structure which is comprised of such a space module which may be used with other similar and/or differently configured space modules, the various space modules being designed and attached to each other in a manner which results in a structure that is strong, easy to construct and has various other advantages and benefits as will be described herein.
Reference is made to
The space module 10 is generally of overall rectangular shape and is made up of longitudinal panels 12, 14, 16 and 18. The panels are angled with respect to each other, and their relationship changes over the length of the panel. This can best be seen by reference to section A-A, section B-B and section C-C in this figure. End panels 20 and 22 and provided. In
Other figures in this application show different panels configured for different purposes, and further details relating thereto are discussed below.
In the description and disclosure below, a range of examples of applications of the frameless space structure of the invention are set forth, together with reference to drawings and formulae which may be used in calculating and determining the shape, size and other characteristics of space structures and their assembly in order to achieve suitably designed structures.
Brick was used by early Romans as the Building Block for Arch Shape Structural Systems. The Arch Shape Structural System was used to develop several applications including Arch Shape Structures and Roofs, Domes, Arch Shape Bridges, Arch Shape Tunnels, and Arch Shape Dams.
In one embodiment, the Frameless Folded Plate Space Structural system of the invention uses the folded Plate Space Module, as the building block of the new system. The system has numerous applications including Frameless Folded Plate Space Structures, Roof Systems, Domes, Future Pressurized Colonies, High Rises, Bridge Systems. Dam Systems, and Tunneling Systems.
The Space Modular is designed based on the Folded Plate Structural Concept. Space Modules are monolithic Structural Units made of thin structural plates, placed in various planes and angles to form the shape of the space modules. Forces on the modular resulting from Dead Loads, Live Loads, Wind and Seismic Movements are balanced by internal Tensile and Compressive Stresses in symmetrical plates acting in opposite directions. Stresses in a structure are internal resistance to external forces. It is the sum of these stresses which holds the Space Modules in equilibrium.
Space Modules in accordance with one aspect of the invention are three dimensional structural units, carrying and transferring loads in three dimensions. It is the three dimensional structural characteristic of the modules and using the plates as structural members and stresses in the plates to counterbalance the external forces which provide the space module with its unique features. Plates are placed, supported and involved in a manlier to carry their maximum loading capacities and reach their maximum allowable stresses.
The Space Module of the invention is designed to be supported on all four sides. Bottom and Top modules in the chain provide the longitudinal support and adjacent modules or symmetrical outer plates of the same modular acting in opposite directions provide the lateral Support.
There are a number of Architectural and Structural factors and considerations to consider when designing and selecting a Space Module of the invention.
a) shows the side view of an atypical modular. Rotation Angle A, End Connection Angles A1L, A1H and Rotation Arm a are variables and are selected based on the Longitudinal Cross section of the system and positioning of each modular in the system. The Desired Span, Middle and End Height values of each modular among other structural and architectural requirements of the system dictates the selection of these values.
b) illustrates the top view of a Space Modular. Detail shows Total width of the Modular W, width of each section W5, Projected end widths of Load Bearing Plates W2, W4 and projected middle width value of W3. In Standard Shape Space Modules, the value of W3 is half of the section width W5.
1-A-a: Design Variables
The first step in design of the space modular is the selection of following variables:
1-A-b: Variable Selection and Considerations
1-A-b-1: Modular Rotation Angle A, Modular Connection Angles A1l and A1h
Rotation and connection angles are calculated based on the architectural characteristics of the system and positioning of each modular. Designers should select these angles, among other considerations, with emphasis on limiting the number of typical modules needed to design the system. Designers should choose angles which would best form the required longitudinal cross section while minimizing the number of typical modules.
1-A-b-2: Modular Rotation Arm a
Among architectural factors which designers need to consider when selecting the Length of Rotation Arm a as outlined above, Designers should consider and take into consideration the structural impact of increasing the length of Rotation Arm a. An increase in length of rotation Arm a reduces the number of modules required to form the required cross section but proportionally decreases the Maximum allowable Moment and Load Bearing capacity of the Modular.
1-A-b-3: Modular Width W, Section Width W5, Load Bearing Plate Projected End Widths W2, W4 Load Bearing Plate Projected Mid Width W3.
Modular Width W is independent but should be chosen proportional to Modular Rotation Arm a. A ratio close to ½ is preferred for W/a is a reasonable starting point. Increase of the total width of the modular increases the maximum Allowable Moment a Modular can carry.
Section Width W5 is chosen based on the structural requirement of the modular. An increase in the Section Width W5, proportionally increases the Load Bearing Plate Widths and effective structural depths. Designers should use a reasonable number of sections in each modular to achieve the required load requirements while maintaining reasonable Plate Widths.
Plate Projected End width W2 is proportional to the end width of Load Bearing Plates (Dimensions f1 and f2). An increase in Dimension W2 increases the above f1 and f2 dimensions, End Plate Connection Plate Sizes and Shear Force capacity of the modular.
1-A-b-4: Plate Projected Mid Width W3
In standard Shape Modules, Dimension W3 is half the dimension W5. In tapered modules, W3 is half the dimension of section at the middle.
1-A-b-5: Main Load Bearing Intersection Angle γ
1-A-c: Geometric Formulas and Calculations
Variables:
Equations:
1-B-a: FC Brick Shapes
Tapered FC Bricks have tapered shapes with variable End and Mid Widths. Tapered FC Bricks are used for round sections including Dome and Super Dome Structures. End and mid Widths are calculated based on the radius each one turns.
1-B-b: FC Brick Types
FC Brick Type illustrates the Shape and the number of sections each FC Brick is made of.
I-B-c, Identifications, Catalogue and Part Numbers
Catalogue and Part numbers represent Type and Major FC Brick dimensions including: Rotation Angle, A; Rotation Arm, a; End Connection Angles, A1h and Ail, Brick Width, W; and Main Load Bearing Plates Intersection Angle, γ.
Space modules are three dimensional structural units. They carry and transfer loads in three dimensions, using the plates as load bearing structural members.
1-C-a: Loading Conditions
1-C-a-1: Loading Causing Positive Longitudinal Moment
a) shows a Space modular subject to Downward Loading condition with upward reactions at end connection points (End Connection Plates). This Loading Condition results in positive moment on the space Modular and inward forces on the outer side Plates due to internal stresses in the outer plates. Positive moment causes Compressive Stresses above the Neutral Axis X-X and Tensile Stresses below the Neutral Axis. It is the sum of Internal Compressive and Tensile Torques which balances the External Moment. Maximum Shear happens at the connection points and is equal to the Resultant of the Reactions at the connection. Inward Forces on the outer symmetrical Plates are either balanced by the adjacent modules' outer plates acting in opposite directions or by a compression member (Braces) tying the outer symmetrical plates of the same Modular acting in opposite directions.
1-C-a-2: Loading Causing Negative Longitudinal Moment
e) shows the Modular subjected to upward loading condition with downward Reactions. This Loading Condition results in negative moment on the Space modular and outward Forces on the outer Plates due to internal stresses. Negative Moment on the Modular causes Tensile Stresses above Neutral Axis X-X and Compressive Stresses below Neutral Axis X-X. Maximum Shear happens at the connection points and is equal to the Resultant of Reactions at the connection. Outward forces on the outer symmetrical Plates are either balanced by the adjacent module's outer Plates acting in opposite directions or by a tension member (braces) tying the outer Plates of same modular acting in opposite directions.
1-C-a-3: Lateral Loading
This Loading Condition results in positive lateral moment on the space Modular, inward Forces on the plates subject to Lateral Loading and outward forces on the opposite outer plates. Positive lateral moment on the modular causes Compressive stresses in the plates to the loading side of Y-Y axis and tensile stresses in the plates on the other side of Y-Y axis. Maximum shear happens at the connections equal to the resultant of the reactions at the connections.
1-C-b: Structural Formulas
1-C-b-1: Centroid and Neutral Axis
Centroid of a plane surface is a point that corresponds to the center of gravity of a very thin homogeneous plate of the same area and shape. Neutral Axis of a section is a line through the Centroid of the section. The equation of moments is used to locate the Neutral Axis. If an area is divided into a number of parts, Statical Moment of the area with respect to an axis is equal to the sum of Statical Moments of the parts with respect to the same axis.
Statical Moment of a plane area with respect to an axis is the product of the area times the distance of the Centroid of the area to the axis. Section A-A, in
1-C-b-2: Moment of Inertia
Moment of inertia can be defined as the sum of products obtained by multiplying all the infinity small areas a by the square of their distances z to the Neutral Axis or: I=a×z2. It can be shown that the moment of inertia of a rectangular cross section of width b and depth d through its base is I=b×d3. It can also be shown that if I be the moment of inertia of a section, having an area A about the Neutral Axis, Ix, the moment of inertia of the same section with respect to an axis X-X which is parallel to the Neutral Axis at h distance is Ix=I+A×h2.
Referring to Section A-A, in
1-C-b-3: Maximum Allowable Longitudinal Moment
Moment Formula
is used in the design of Space Modules in which: M is Maximum allowable Bending Moment: fm is Maximum Allowable Unit Stress in the fiber farthest from the Neutral Axis; c is Distance of the fiber farthest from the Neutral Axis; and I is Moment of Inertia about the Neutral Axis.
Section A-A, in
1-C-b-4: Maximum Allowable Lateral Moment
Referring to section A-A, in
and My(max) is the lesser of the two values or
M
y(max)≦Myc(max)
M
y(max)≦Myt(max)
1-C-b-5: Shear Calculations
After the Space Modular is designed for flexure, it should be investigated for shear. Space Modular has a tendency to fail by shear by the fibers that slide past each other both vertically and horizontally. Shearing stresses are not equally distributed over the cross section but are greatest at the Neutral Axis and are zero at the extreme fibers. Maximum allowable vertical shear V is the product of the cross sectional area A and maximum allowable shearing stress ν or V=ν×A. Maximum shear force happens at the connections and is equal to the sum of reactions.
Section B-B,
V=ν×t×(N.O.P×f1+N.O.P×f2+2r1)
1-C-b-6: Buckling
Buckling is the failure of Space Modular at a concentrated load or at reactions due to compression stresses or
R
max
=t×(N.O.P×f1+N.O.P×f2+2r1)fc
1-C-b-7: Outer Plates Lateral Forces Calculations
Sheet SM-3B illustrates a modular subject to negative and positive moments.
Internal longitudinal forces Fil is the product of the stresses in the plates, effective depth, 1 ml and the thickness of the plates. The maximum force happens under maximum allowable positive and negative moments causing maximum allowable compressive and tensile stresses. The following formulas should be used to find the maximum internal longitudinal forces.
If M=(+)
The upper portion of the plates are under compressive stress which causes an Internal Longitudinal Compressive Force, Filc
And Maximum Lateral Inward Force, Fli of
If M=(−)
The upper portion of the plates are under tensile stress which cause an Internal Longitudinal Tensile Force, Filt of
And Maximum Lateral Inward Force, Fli of
1-C-b-8: Outer Plates Lateral Support (Braces, Connections), Selection
The lateral force is either provided by adjacent sections or in case of single section systems, it is provided by braces.
Multiple Sections: In case of multiple sections, the total allowable tensile forces of connections, bolts should be more than the total Lateral Inward Force described in previous chapter.
Single Sections: In case of single section systems, the total allowable tensile and compressive forces of the braces should be more than the total Lateral Inward or outward forces described in previous chapter.
1-C-c: Sample Calculations
Frameless Folded Plate Space Structural System uses the Space Modular as the core of the system. Typical Modules, FC Bricks are bolted together by the end plates to form a longitudinal chain. Each FC Brick is supported longitudinally by bottom and top bricks, eliminating the need for any intermediate supports. The system is only supported by the two end FC bricks bolted to the foundation (Exterior Supports). Lateral support is provided by adjacent Bricks. or in case of single section structures, lateral support is provided by outer plates of the same modular acting in opposite Directions. The number and kinds of bricks to form the chain depends on the architectural, civil and structural characteristic of the system.
Frameless Folded Plate Space Structural System combines and expands four main structural systems: Arch System; Shell System; Sectionalized System; and Folded Plate. The end system is an Arch, Shell, Folded Plate, and Sectionalized System. Each system has numerous advantages which will be briefly explained but it is the folded Plate structure of the FC Bricks and new extended sectionalized concept which practically provides unlimited structural capabilities for the system.
Monolithic Dome and Shell Structures, with all their advantages, have their limitations. As the span of the structure grows, Moment on the structure proportionally increases. A structure can fail due to several factors including Moment, Shear and buckling. However, Moment is often the main reason a structure collapses. The system in accordance with one aspect of the invention prevents accumulation of the moment by dividing the cross section into several sections. Each section is a Folded Plate Unit.
Among other structural characteristics and capabilities of the FC Brick is the structural capability of the FC Brick to resist negative and positive moments which make the system possible and unique. Under normal loading conditions, a modular is held in place by top and bottom modules acting as main supports, just like a structural unit in conventional structures is supported by columns or walls. The moment which each FC Brick is subject to is the moment caused by the loads directly on the brick and the moment caused by the resultant of the reactions at each end on the connections. However, unlike conventional structures in which reactions are positive causing positive moments on the modular, reactions on a connection in this system can be negative causing negative moment in the brick.
Maximum Shear Force on the FC Brick is equal to the upward or downward resultant reaction Forces.
Most Space Structures are made of several sections. Each section is bolted to the adjacent sections providing the necessary lateral support. The resultant inward or outward forces on the outer plates are the sum of dead and live load on the outer plates, and the longitudinal forces in the plates result from stresses in the plates. Maximum longitudinal forces in the plates happen at the point of maximum moment on the modular.
In the case of single section structures, lateral support is provided by symmetrical outer plates acting in opposite directions. This is done by compression and tension members (braces) tying the two outer plates together.
Preferably, the optimum numbers and kinds of Typical Space Modules are selected to form the required cross section.
2-B-a: Geometric Design Considerations
These angles should be selected to minimize the use of different kinds of units while maintaining the cross sectional requirement. Selection of rotation Arm a, should also be based on cross sectional requirement and optimum number of typical Space Modules to form the cross section.
2-B-b: Geometric Calculations and Modular Selection
2-B-b-1: Variable Selections
The first step of selection is to select the number of modules, Modular Rotation Arms and Modules Projected angles α1 to αn.
Then the following variables are selected
2-B-b-2: Modular Rotation & Connection Angle Formulas
The aim of structural calculation is to select the optimum space modular for the system.
2-C-a: Variable Selections
Variables can be grouped in two categories.
2-C-a-1: Variables Governed by Structural Codes and Project Specifications:
The following Variables are chosen as per structural codes and Project Specifications:
2-C-a-2: Space Modular Structural Variables
2-C-b: Dead Load, Live Load
2-C-b-1: Loads, Reactions, Calculation
The first step to analyze the Space Structures is to calculate the Reactions due to Deal Load, Live Load and Wind Pressure.
For instance. Connection C provides an upward Reaction Force Of r3y for modular 2, equal to half of the total load of the section to the left and applies a downward force of W3, on the modular, equal to half of the total load of the section to the right.
Similarly, at connection point D:
2-C-b-2: Maximum Moment Calculations
The same formulas can be written for each modular under different loading conditions and the maximum negative and positive moments applied to each modular can be calculated. Depending on the loading conditions, maximum moments and signs change. Modules are selected based on the worst loading conditions.
2-C-b-3: Actual Shear and Buckling Force Calculations
Actual shear Forces on each unit occur at the ends of the Modular, equal to the sum of reactions and loads at the connections. Maximum Shear force is the bigger of the two resultant forces at each end or Va(max)=(rny+Wn), or Va(max
)=(rn1y+Wn1). Maximum Buckling occurs at the supports and the maximum actual buckling force is equal to the total reactions at the supports, equal to R1y and R3y.
2-C-c, Wind Calculations
2-C-c-1: Wind Pressure and Reaction Calculations
2-C-c-2: Maximum Moment Calculations
Moment calculations for each modular is similar to calculations previously described in chapter 2-C-b-2.
2-C-c-3: Shear Calculations
Shear calculations are similar to calculations previously described in chapter 2-C-b-3.
2-C-c-4: Modular Selection
Modular selection is based on the maximum moment for each modular. Maximum moment is the maximum moment on each modular based on Live/Dead Load, wind Pressure or a combination thereof.
2-C-d: Modular Verification
2-C-d-1: Actual Moment Calculations
Previous chapters calculated the maximum moment at the center of the modular. The maximum moment does not necessarily happen at the center. Maximum moment happens at a point where the resultant moments on each side of the point are equal.
2-C-d-2
Frameless Folded Plate Space Structural Systems have numerous applications and usages. Applications have been grouped into eight separate main categories, which are intended to be representative and not definitive.
Simple Frameless Folded Plate Space Structures are made of assembling several similar sections of a Frameless Folded Plate Space Structural System with required cross section in a row to achieve the required depth (Length). Numerous advantages of FFPSS to conventional structures make them ideal for construction of all kinds and types of structures including Residential, commercial, Agricultural and industrial buildings. Their light weight, easy delivery, fast construction, and structural capabilities make them unique for fast track or Emergency Shelter construction.
3-A-a: Types
3-A-b: Front and Back Elevations, Space Wall Modules
3-A-c: Standard Sizes
3-A-d: System Flexibility
3-A-e: Structural Design
3-A-e-1: Shell Calculations
Structural calculations for Space structures follow the basic calculations and formulas described above.
3-A-e-2: End Sections and Wall Modules Calculations
End sections: End sections should be treated as laterally unsupported. End sections should be braced like a single section system, previously described in section 1-C-b-8. In most structures, a total of three braces is adequate to provide the required lateral support.
Wall Modules:
Frameless Folded Plate Space Roof Structures are made of sections of Frameless Folded Plate Space Structural Systems with the desired cross section to achieve the required size. They may be installed on exterior walls or on main structural framing eliminating the need for any additional framing, sheathing, roofing and insulation.
3-B-a: Types
3-B-b: Structural Design
Structural calculations for Space Roof Systems follow the basic calculations and formulas described above.
3-C-a, Geometric Design
Frameless folded plate Space Domes are Dome, Shell, Sectionalized structures. They look like an upside down bowl, cut horizontally and vertically into several layers and Grids.
3-C-a-1: Shell
OD3=OD1−First Layer Total Horizontal Projection
OD-5=OD3−2nd Layer Total Horizontal Projection, etc.
b) shows the top view of the same Dome. As the top view shows, the Dome has been divided into Vertical Grids. Vertical Grid Lines divide each layer into typical, similar size sections: SM-1A, SM-2A, SM-3A, . . . ; SM-1B, SM-2B, SM-3B, . . . . Each section is a tapered space modular with bottom, mid and top total widths, Wl, WM and WH equal to:
W
AL=OD1÷Number of Grids
W
AM=OD2÷Number of Grids
W
AH
=W
BL=OD3÷Number of grids
3-C-a-2: Tapered Modular
Tapered modules should be designed using the following sets of variables:
3-C-b: Architectural Design
3-C-c: Frameless Folded Plate Space Future Pressurized Colonies, FFPS-FPC
Unique Structural Capabilities of space domes make them ideal for future pressurized structures. Space Domes can carry the same loads regardless of direction of the loads. All formulas developed treat the loads as vectors. Direction of the loads basically changes the direction of the reactions and moments.
Frameless Folded Plate Space High Rises are constructed by using Space wall Modules and Space Ceiling Modules as Load Bearing Walls and Ceilings. Structural capabilities of the Space System reduces the number of interior load bearing walls, providing architectural capabilities which conventional structures can not economically provide.
3-D-a: Architectural Design
3-D-b: Structural Calculations
Structural calculations follow the structural calculations described in System Structural Design and Space Modular Structural calculations. Lateral support for each section (walls and ceilings) is provided by adjacent sections.
FFPS-Bridge Systems with their numerous advantages including Light Weight, Easy Delivery and Erection can be used as temporary or permanent bridges. System flexibility offers any required cross section and span.
3-E-a: Type
3-E-b: Civil & Geometric Design
Geometric and Civil design of Space Bridges are similar to the System design described herein.
3-E-c: Structural Design
Structural Design of FFPS-Bridge Systems is similar to System Structural Design described in previous chapters. Lateral Support for the Bridges is provided by a Bridge Deck Framing System.
FFPS-Dam System are made of sections of FFPS-Structural systems with desired cross section to achieve the desired height.
3-F-a: Structural Design
FFPS-Dam is calculated as per structural calculations described herein. Live Load on each section varies and is proportional to the height of the Dam. Each section needs to be designed to independently carry the live load. Since the live load on each section varies, the lateral force resulting from internal stresses also varies. The entire structure needs to be laterally supported by a system of continuous bracings. Section A-A in
FFPS-SS can be used for tunneling purposes for both Rock Tunneling and Shield Tunneling Methods. Tunnel sections are made of sections of FFPS-Structural System with the desired cross section installed after the drilling is done. In the case of Rock tunneling, each section can be assembled in whole or parts and erected after the drilling is done.
Number | Date | Country | |
---|---|---|---|
61070389 | Mar 2008 | US | |
61203585 | Dec 2008 | US |